Commit a13f0d40eb

Andrew Kelley <andrew@ziglang.org>
2025-07-02 23:50:41
compiler: delete arm backend
this backend was abandoned before it was completed, and it is not worth salvaging.
1 parent 20a5430
src/arch/arm/bits.zig
@@ -1,1566 +0,0 @@
-const std = @import("std");
-const assert = std.debug.assert;
-const testing = std.testing;
-
-/// The condition field specifies the flags necessary for an
-/// Instruction to be executed
-pub const Condition = enum(u4) {
-    /// equal
-    eq,
-    /// not equal
-    ne,
-    /// unsigned higher or same
-    cs,
-    /// unsigned lower
-    cc,
-    /// negative
-    mi,
-    /// positive or zero
-    pl,
-    /// overflow
-    vs,
-    /// no overflow
-    vc,
-    /// unsigned higer
-    hi,
-    /// unsigned lower or same
-    ls,
-    /// greater or equal
-    ge,
-    /// less than
-    lt,
-    /// greater than
-    gt,
-    /// less than or equal
-    le,
-    /// always
-    al,
-
-    /// Converts a std.math.CompareOperator into a condition flag,
-    /// i.e. returns the condition that is true iff the result of the
-    /// comparison is true. Assumes signed comparison
-    pub fn fromCompareOperatorSigned(op: std.math.CompareOperator) Condition {
-        return switch (op) {
-            .gte => .ge,
-            .gt => .gt,
-            .neq => .ne,
-            .lt => .lt,
-            .lte => .le,
-            .eq => .eq,
-        };
-    }
-
-    /// Converts a std.math.CompareOperator into a condition flag,
-    /// i.e. returns the condition that is true iff the result of the
-    /// comparison is true. Assumes unsigned comparison
-    pub fn fromCompareOperatorUnsigned(op: std.math.CompareOperator) Condition {
-        return switch (op) {
-            .gte => .cs,
-            .gt => .hi,
-            .neq => .ne,
-            .lt => .cc,
-            .lte => .ls,
-            .eq => .eq,
-        };
-    }
-
-    /// Returns the condition which is true iff the given condition is
-    /// false (if such a condition exists)
-    pub fn negate(cond: Condition) Condition {
-        return switch (cond) {
-            .eq => .ne,
-            .ne => .eq,
-            .cs => .cc,
-            .cc => .cs,
-            .mi => .pl,
-            .pl => .mi,
-            .vs => .vc,
-            .vc => .vs,
-            .hi => .ls,
-            .ls => .hi,
-            .ge => .lt,
-            .lt => .ge,
-            .gt => .le,
-            .le => .gt,
-            .al => unreachable,
-        };
-    }
-};
-
-test "condition from CompareOperator" {
-    try testing.expectEqual(@as(Condition, .eq), Condition.fromCompareOperatorSigned(.eq));
-    try testing.expectEqual(@as(Condition, .eq), Condition.fromCompareOperatorUnsigned(.eq));
-
-    try testing.expectEqual(@as(Condition, .gt), Condition.fromCompareOperatorSigned(.gt));
-    try testing.expectEqual(@as(Condition, .hi), Condition.fromCompareOperatorUnsigned(.gt));
-
-    try testing.expectEqual(@as(Condition, .le), Condition.fromCompareOperatorSigned(.lte));
-    try testing.expectEqual(@as(Condition, .ls), Condition.fromCompareOperatorUnsigned(.lte));
-}
-
-test "negate condition" {
-    try testing.expectEqual(@as(Condition, .eq), Condition.ne.negate());
-    try testing.expectEqual(@as(Condition, .ne), Condition.eq.negate());
-}
-
-/// Represents a register in the ARM instruction set architecture
-pub const Register = enum(u5) {
-    r0,
-    r1,
-    r2,
-    r3,
-    r4,
-    r5,
-    r6,
-    r7,
-    r8,
-    r9,
-    r10,
-    r11,
-    r12,
-    r13,
-    r14,
-    r15,
-
-    /// Argument / result / scratch register 1
-    a1,
-    /// Argument / result / scratch register 2
-    a2,
-    /// Argument / scratch register 3
-    a3,
-    /// Argument / scratch register 4
-    a4,
-    /// Variable-register 1
-    v1,
-    /// Variable-register 2
-    v2,
-    /// Variable-register 3
-    v3,
-    /// Variable-register 4
-    v4,
-    /// Variable-register 5
-    v5,
-    /// Platform register
-    v6,
-    /// Variable-register 7
-    v7,
-    /// Frame pointer or Variable-register 8
-    fp,
-    /// Intra-Procedure-call scratch register
-    ip,
-    /// Stack pointer
-    sp,
-    /// Link register
-    lr,
-    /// Program counter
-    pc,
-
-    /// Returns the unique 4-bit ID of this register which is used in
-    /// the machine code
-    pub fn id(reg: Register) u4 {
-        return @truncate(@intFromEnum(reg));
-    }
-
-    pub fn dwarfNum(reg: Register) u4 {
-        return reg.id();
-    }
-};
-
-test "Register.id" {
-    try testing.expectEqual(@as(u4, 15), Register.r15.id());
-    try testing.expectEqual(@as(u4, 15), Register.pc.id());
-}
-
-/// Program status registers containing flags, mode bits and other
-/// vital information
-pub const Psr = enum {
-    cpsr,
-    spsr,
-};
-
-/// Represents an instruction in the ARM instruction set architecture
-pub const Instruction = union(enum) {
-    data_processing: packed struct {
-        // Note to self: The order of the fields top-to-bottom is
-        // right-to-left in the actual 32-bit int representation
-        op2: u12,
-        rd: u4,
-        rn: u4,
-        s: u1,
-        opcode: u4,
-        i: u1,
-        fixed: u2 = 0b00,
-        cond: u4,
-    },
-    multiply: packed struct {
-        rn: u4,
-        fixed_1: u4 = 0b1001,
-        rm: u4,
-        ra: u4,
-        rd: u4,
-        set_cond: u1,
-        accumulate: u1,
-        fixed_2: u6 = 0b000000,
-        cond: u4,
-    },
-    multiply_long: packed struct {
-        rn: u4,
-        fixed_1: u4 = 0b1001,
-        rm: u4,
-        rdlo: u4,
-        rdhi: u4,
-        set_cond: u1,
-        accumulate: u1,
-        unsigned: u1,
-        fixed_2: u5 = 0b00001,
-        cond: u4,
-    },
-    signed_multiply_halfwords: packed struct {
-        rn: u4,
-        fixed_1: u1 = 0b0,
-        n: u1,
-        m: u1,
-        fixed_2: u1 = 0b1,
-        rm: u4,
-        fixed_3: u4 = 0b0000,
-        rd: u4,
-        fixed_4: u8 = 0b00010110,
-        cond: u4,
-    },
-    integer_saturating_arithmetic: packed struct {
-        rm: u4,
-        fixed_1: u8 = 0b0000_0101,
-        rd: u4,
-        rn: u4,
-        fixed_2: u1 = 0b0,
-        opc: u2,
-        fixed_3: u5 = 0b00010,
-        cond: u4,
-    },
-    bit_field_extract: packed struct {
-        rn: u4,
-        fixed_1: u3 = 0b101,
-        lsb: u5,
-        rd: u4,
-        widthm1: u5,
-        fixed_2: u1 = 0b1,
-        unsigned: u1,
-        fixed_3: u5 = 0b01111,
-        cond: u4,
-    },
-    single_data_transfer: packed struct {
-        offset: u12,
-        rd: u4,
-        rn: u4,
-        load_store: u1,
-        write_back: u1,
-        byte_word: u1,
-        up_down: u1,
-        pre_post: u1,
-        imm: u1,
-        fixed: u2 = 0b01,
-        cond: u4,
-    },
-    extra_load_store: packed struct {
-        imm4l: u4,
-        fixed_1: u1 = 0b1,
-        op2: u2,
-        fixed_2: u1 = 0b1,
-        imm4h: u4,
-        rt: u4,
-        rn: u4,
-        o1: u1,
-        write_back: u1,
-        imm: u1,
-        up_down: u1,
-        pre_index: u1,
-        fixed_3: u3 = 0b000,
-        cond: u4,
-    },
-    block_data_transfer: packed struct {
-        register_list: u16,
-        rn: u4,
-        load_store: u1,
-        write_back: u1,
-        psr_or_user: u1,
-        up_down: u1,
-        pre_post: u1,
-        fixed: u3 = 0b100,
-        cond: u4,
-    },
-    branch: packed struct {
-        offset: u24,
-        link: u1,
-        fixed: u3 = 0b101,
-        cond: u4,
-    },
-    branch_exchange: packed struct {
-        rn: u4,
-        fixed_1: u1 = 0b1,
-        link: u1,
-        fixed_2: u22 = 0b0001_0010_1111_1111_1111_00,
-        cond: u4,
-    },
-    supervisor_call: packed struct {
-        comment: u24,
-        fixed: u4 = 0b1111,
-        cond: u4,
-    },
-    undefined_instruction: packed struct {
-        imm32: u32 = 0xe7ffdefe,
-    },
-    breakpoint: packed struct {
-        imm4: u4,
-        fixed_1: u4 = 0b0111,
-        imm12: u12,
-        fixed_2_and_cond: u12 = 0b1110_0001_0010,
-    },
-
-    /// Represents the possible operations which can be performed by a
-    /// Data Processing instruction
-    const Opcode = enum(u4) {
-        // Rd := Op1 AND Op2
-        @"and",
-        // Rd := Op1 EOR Op2
-        eor,
-        // Rd := Op1 - Op2
-        sub,
-        // Rd := Op2 - Op1
-        rsb,
-        // Rd := Op1 + Op2
-        add,
-        // Rd := Op1 + Op2 + C
-        adc,
-        // Rd := Op1 - Op2 + C - 1
-        sbc,
-        // Rd := Op2 - Op1 + C - 1
-        rsc,
-        // set condition codes on Op1 AND Op2
-        tst,
-        // set condition codes on Op1 EOR Op2
-        teq,
-        // set condition codes on Op1 - Op2
-        cmp,
-        // set condition codes on Op1 + Op2
-        cmn,
-        // Rd := Op1 OR Op2
-        orr,
-        // Rd := Op2
-        mov,
-        // Rd := Op1 AND NOT Op2
-        bic,
-        // Rd := NOT Op2
-        mvn,
-    };
-
-    /// Represents the second operand to a data processing instruction
-    /// which can either be content from a register or an immediate
-    /// value
-    pub const Operand = union(enum) {
-        register: packed struct {
-            rm: u4,
-            shift: u8,
-        },
-        immediate: packed struct {
-            imm: u8,
-            rotate: u4,
-        },
-
-        /// Represents multiple ways a register can be shifted. A
-        /// register can be shifted by a specific immediate value or
-        /// by the contents of another register
-        pub const Shift = union(enum) {
-            immediate: packed struct {
-                fixed: u1 = 0b0,
-                typ: u2,
-                amount: u5,
-            },
-            register: packed struct {
-                fixed_1: u1 = 0b1,
-                typ: u2,
-                fixed_2: u1 = 0b0,
-                rs: u4,
-            },
-
-            pub const Type = enum(u2) {
-                logical_left,
-                logical_right,
-                arithmetic_right,
-                rotate_right,
-            };
-
-            pub const none = Shift{
-                .immediate = .{
-                    .amount = 0,
-                    .typ = 0,
-                },
-            };
-
-            pub fn toU8(self: Shift) u8 {
-                return switch (self) {
-                    .register => |v| @as(u8, @bitCast(v)),
-                    .immediate => |v| @as(u8, @bitCast(v)),
-                };
-            }
-
-            pub fn reg(rs: Register, typ: Type) Shift {
-                return Shift{
-                    .register = .{
-                        .rs = rs.id(),
-                        .typ = @intFromEnum(typ),
-                    },
-                };
-            }
-
-            pub fn imm(amount: u5, typ: Type) Shift {
-                return Shift{
-                    .immediate = .{
-                        .amount = amount,
-                        .typ = @intFromEnum(typ),
-                    },
-                };
-            }
-        };
-
-        pub fn toU12(self: Operand) u12 {
-            return switch (self) {
-                .register => |v| @as(u12, @bitCast(v)),
-                .immediate => |v| @as(u12, @bitCast(v)),
-            };
-        }
-
-        pub fn reg(rm: Register, shift: Shift) Operand {
-            return Operand{
-                .register = .{
-                    .rm = rm.id(),
-                    .shift = shift.toU8(),
-                },
-            };
-        }
-
-        pub fn imm(immediate: u8, rotate: u4) Operand {
-            return Operand{
-                .immediate = .{
-                    .imm = immediate,
-                    .rotate = rotate,
-                },
-            };
-        }
-
-        /// Tries to convert an unsigned 32 bit integer into an
-        /// immediate operand using rotation. Returns null when there
-        /// is no conversion
-        pub fn fromU32(x: u32) ?Operand {
-            const masks = comptime blk: {
-                const base_mask: u32 = std.math.maxInt(u8);
-                var result = [_]u32{0} ** 16;
-                for (&result, 0..) |*mask, i| mask.* = std.math.rotr(u32, base_mask, 2 * i);
-                break :blk result;
-            };
-
-            return for (masks, 0..) |mask, i| {
-                if (x & mask == x) {
-                    break Operand{
-                        .immediate = .{
-                            .imm = @as(u8, @intCast(std.math.rotl(u32, x, 2 * i))),
-                            .rotate = @as(u4, @intCast(i)),
-                        },
-                    };
-                }
-            } else null;
-        }
-    };
-
-    pub const AddressingMode = enum {
-        /// [<Rn>, <offset>]
-        ///
-        /// Address = Rn + offset
-        offset,
-        /// [<Rn>, <offset>]!
-        ///
-        /// Address = Rn + offset
-        /// Rn = Rn + offset
-        pre_index,
-        /// [<Rn>], <offset>
-        ///
-        /// Address = Rn
-        /// Rn = Rn + offset
-        post_index,
-    };
-
-    /// Represents the offset operand of a load or store
-    /// instruction. Data can be loaded from memory with either an
-    /// immediate offset or an offset that is stored in some register.
-    pub const Offset = union(enum) {
-        immediate: u12,
-        register: packed struct {
-            rm: u4,
-            fixed: u1 = 0b0,
-            stype: u2,
-            imm5: u5,
-        },
-
-        pub const Shift = union(enum) {
-            /// No shift
-            none,
-            /// Logical shift left
-            lsl: u5,
-            /// Logical shift right
-            lsr: u5,
-            /// Arithmetic shift right
-            asr: u5,
-            /// Rotate right
-            ror: u5,
-            /// Rotate right one bit, with extend
-            rrx,
-        };
-
-        pub const none = Offset{
-            .immediate = 0,
-        };
-
-        pub fn toU12(self: Offset) u12 {
-            return switch (self) {
-                .register => |v| @as(u12, @bitCast(v)),
-                .immediate => |v| v,
-            };
-        }
-
-        pub fn reg(rm: Register, shift: Shift) Offset {
-            return Offset{
-                .register = .{
-                    .rm = rm.id(),
-                    .stype = switch (shift) {
-                        .none => 0b00,
-                        .lsl => 0b00,
-                        .lsr => 0b01,
-                        .asr => 0b10,
-                        .ror => 0b11,
-                        .rrx => 0b11,
-                    },
-                    .imm5 = switch (shift) {
-                        .none => 0,
-                        .lsl => |n| n,
-                        .lsr => |n| n,
-                        .asr => |n| n,
-                        .ror => |n| n,
-                        .rrx => 0,
-                    },
-                },
-            };
-        }
-
-        pub fn imm(immediate: u12) Offset {
-            return Offset{
-                .immediate = immediate,
-            };
-        }
-    };
-
-    /// Represents the offset operand of an extra load or store
-    /// instruction.
-    pub const ExtraLoadStoreOffset = union(enum) {
-        immediate: u8,
-        register: u4,
-
-        pub const none = ExtraLoadStoreOffset{
-            .immediate = 0,
-        };
-
-        pub fn reg(register: Register) ExtraLoadStoreOffset {
-            return ExtraLoadStoreOffset{
-                .register = register.id(),
-            };
-        }
-
-        pub fn imm(immediate: u8) ExtraLoadStoreOffset {
-            return ExtraLoadStoreOffset{
-                .immediate = immediate,
-            };
-        }
-    };
-
-    /// Represents the register list operand to a block data transfer
-    /// instruction
-    pub const RegisterList = packed struct {
-        r0: bool = false,
-        r1: bool = false,
-        r2: bool = false,
-        r3: bool = false,
-        r4: bool = false,
-        r5: bool = false,
-        r6: bool = false,
-        r7: bool = false,
-        r8: bool = false,
-        r9: bool = false,
-        r10: bool = false,
-        r11: bool = false,
-        r12: bool = false,
-        r13: bool = false,
-        r14: bool = false,
-        r15: bool = false,
-    };
-
-    pub fn toU32(self: Instruction) u32 {
-        return switch (self) {
-            .data_processing => |v| @as(u32, @bitCast(v)),
-            .multiply => |v| @as(u32, @bitCast(v)),
-            .multiply_long => |v| @as(u32, @bitCast(v)),
-            .signed_multiply_halfwords => |v| @as(u32, @bitCast(v)),
-            .integer_saturating_arithmetic => |v| @as(u32, @bitCast(v)),
-            .bit_field_extract => |v| @as(u32, @bitCast(v)),
-            .single_data_transfer => |v| @as(u32, @bitCast(v)),
-            .extra_load_store => |v| @as(u32, @bitCast(v)),
-            .block_data_transfer => |v| @as(u32, @bitCast(v)),
-            .branch => |v| @as(u32, @bitCast(v)),
-            .branch_exchange => |v| @as(u32, @bitCast(v)),
-            .supervisor_call => |v| @as(u32, @bitCast(v)),
-            .undefined_instruction => |v| v.imm32,
-            .breakpoint => |v| @as(u32, @intCast(v.imm4)) | (@as(u32, @intCast(v.fixed_1)) << 4) | (@as(u32, @intCast(v.imm12)) << 8) | (@as(u32, @intCast(v.fixed_2_and_cond)) << 20),
-        };
-    }
-
-    // Helper functions for the "real" functions below
-
-    fn dataProcessing(
-        cond: Condition,
-        opcode: Opcode,
-        s: u1,
-        rd: Register,
-        rn: Register,
-        op2: Operand,
-    ) Instruction {
-        return Instruction{
-            .data_processing = .{
-                .cond = @intFromEnum(cond),
-                .i = @intFromBool(op2 == .immediate),
-                .opcode = @intFromEnum(opcode),
-                .s = s,
-                .rn = rn.id(),
-                .rd = rd.id(),
-                .op2 = op2.toU12(),
-            },
-        };
-    }
-
-    fn specialMov(
-        cond: Condition,
-        rd: Register,
-        imm: u16,
-        top: bool,
-    ) Instruction {
-        return Instruction{
-            .data_processing = .{
-                .cond = @intFromEnum(cond),
-                .i = 1,
-                .opcode = if (top) 0b1010 else 0b1000,
-                .s = 0,
-                .rn = @as(u4, @truncate(imm >> 12)),
-                .rd = rd.id(),
-                .op2 = @as(u12, @truncate(imm)),
-            },
-        };
-    }
-
-    fn initMultiply(
-        cond: Condition,
-        set_cond: u1,
-        rd: Register,
-        rn: Register,
-        rm: Register,
-        ra: ?Register,
-    ) Instruction {
-        return Instruction{
-            .multiply = .{
-                .cond = @intFromEnum(cond),
-                .accumulate = @intFromBool(ra != null),
-                .set_cond = set_cond,
-                .rd = rd.id(),
-                .rn = rn.id(),
-                .ra = if (ra) |reg| reg.id() else 0b0000,
-                .rm = rm.id(),
-            },
-        };
-    }
-
-    fn multiplyLong(
-        cond: Condition,
-        signed: u1,
-        accumulate: u1,
-        set_cond: u1,
-        rdhi: Register,
-        rdlo: Register,
-        rm: Register,
-        rn: Register,
-    ) Instruction {
-        return Instruction{
-            .multiply_long = .{
-                .cond = @intFromEnum(cond),
-                .unsigned = signed,
-                .accumulate = accumulate,
-                .set_cond = set_cond,
-                .rdlo = rdlo.id(),
-                .rdhi = rdhi.id(),
-                .rn = rn.id(),
-                .rm = rm.id(),
-            },
-        };
-    }
-
-    fn signedMultiplyHalfwords(
-        n: u1,
-        m: u1,
-        cond: Condition,
-        rd: Register,
-        rn: Register,
-        rm: Register,
-    ) Instruction {
-        return Instruction{
-            .signed_multiply_halfwords = .{
-                .rn = rn.id(),
-                .n = n,
-                .m = m,
-                .rm = rm.id(),
-                .rd = rd.id(),
-                .cond = @intFromEnum(cond),
-            },
-        };
-    }
-
-    fn integerSaturationArithmetic(
-        cond: Condition,
-        rd: Register,
-        rm: Register,
-        rn: Register,
-        opc: u2,
-    ) Instruction {
-        return Instruction{
-            .integer_saturating_arithmetic = .{
-                .rm = rm.id(),
-                .rd = rd.id(),
-                .rn = rn.id(),
-                .opc = opc,
-                .cond = @intFromEnum(cond),
-            },
-        };
-    }
-
-    fn bitFieldExtract(
-        unsigned: u1,
-        cond: Condition,
-        rd: Register,
-        rn: Register,
-        lsb: u5,
-        width: u6,
-    ) Instruction {
-        assert(width > 0 and width <= 32);
-        return Instruction{
-            .bit_field_extract = .{
-                .rn = rn.id(),
-                .lsb = lsb,
-                .rd = rd.id(),
-                .widthm1 = @as(u5, @intCast(width - 1)),
-                .unsigned = unsigned,
-                .cond = @intFromEnum(cond),
-            },
-        };
-    }
-
-    fn singleDataTransfer(
-        cond: Condition,
-        rd: Register,
-        rn: Register,
-        offset: Offset,
-        mode: AddressingMode,
-        positive: bool,
-        byte_word: u1,
-        load_store: u1,
-    ) Instruction {
-        return Instruction{
-            .single_data_transfer = .{
-                .cond = @intFromEnum(cond),
-                .rn = rn.id(),
-                .rd = rd.id(),
-                .offset = offset.toU12(),
-                .load_store = load_store,
-                .write_back = switch (mode) {
-                    .offset => 0b0,
-                    .pre_index, .post_index => 0b1,
-                },
-                .byte_word = byte_word,
-                .up_down = @intFromBool(positive),
-                .pre_post = switch (mode) {
-                    .offset, .pre_index => 0b1,
-                    .post_index => 0b0,
-                },
-                .imm = @intFromBool(offset != .immediate),
-            },
-        };
-    }
-
-    fn extraLoadStore(
-        cond: Condition,
-        mode: AddressingMode,
-        positive: bool,
-        o1: u1,
-        op2: u2,
-        rn: Register,
-        rt: Register,
-        offset: ExtraLoadStoreOffset,
-    ) Instruction {
-        const imm4l: u4 = switch (offset) {
-            .immediate => |imm| @as(u4, @truncate(imm)),
-            .register => |reg| reg,
-        };
-        const imm4h: u4 = switch (offset) {
-            .immediate => |imm| @as(u4, @truncate(imm >> 4)),
-            .register => 0b0000,
-        };
-
-        return Instruction{
-            .extra_load_store = .{
-                .imm4l = imm4l,
-                .op2 = op2,
-                .imm4h = imm4h,
-                .rt = rt.id(),
-                .rn = rn.id(),
-                .o1 = o1,
-                .write_back = switch (mode) {
-                    .offset => 0b0,
-                    .pre_index, .post_index => 0b1,
-                },
-                .imm = @intFromBool(offset == .immediate),
-                .up_down = @intFromBool(positive),
-                .pre_index = switch (mode) {
-                    .offset, .pre_index => 0b1,
-                    .post_index => 0b0,
-                },
-                .cond = @intFromEnum(cond),
-            },
-        };
-    }
-
-    fn blockDataTransfer(
-        cond: Condition,
-        rn: Register,
-        reg_list: RegisterList,
-        pre_post: u1,
-        up_down: u1,
-        psr_or_user: u1,
-        write_back: bool,
-        load_store: u1,
-    ) Instruction {
-        return Instruction{
-            .block_data_transfer = .{
-                .register_list = @as(u16, @bitCast(reg_list)),
-                .rn = rn.id(),
-                .load_store = load_store,
-                .write_back = @intFromBool(write_back),
-                .psr_or_user = psr_or_user,
-                .up_down = up_down,
-                .pre_post = pre_post,
-                .cond = @intFromEnum(cond),
-            },
-        };
-    }
-
-    fn initBranch(cond: Condition, offset: i26, link: u1) Instruction {
-        return Instruction{
-            .branch = .{
-                .cond = @intFromEnum(cond),
-                .link = link,
-                .offset = @as(u24, @bitCast(@as(i24, @intCast(offset >> 2)))),
-            },
-        };
-    }
-
-    fn branchExchange(cond: Condition, rn: Register, link: u1) Instruction {
-        return Instruction{
-            .branch_exchange = .{
-                .cond = @intFromEnum(cond),
-                .link = link,
-                .rn = rn.id(),
-            },
-        };
-    }
-
-    fn supervisorCall(cond: Condition, comment: u24) Instruction {
-        return Instruction{
-            .supervisor_call = .{
-                .cond = @intFromEnum(cond),
-                .comment = comment,
-            },
-        };
-    }
-
-    // This instruction has no official mnemonic equivalent so it is public as-is.
-    pub fn undefinedInstruction() Instruction {
-        return Instruction{
-            .undefined_instruction = .{},
-        };
-    }
-
-    fn initBreakpoint(imm: u16) Instruction {
-        return Instruction{
-            .breakpoint = .{
-                .imm12 = @as(u12, @truncate(imm >> 4)),
-                .imm4 = @as(u4, @truncate(imm)),
-            },
-        };
-    }
-
-    // Public functions replicating assembler syntax as closely as
-    // possible
-
-    // Data processing
-
-    pub fn @"and"(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .@"and", 0, rd, rn, op2);
-    }
-
-    pub fn ands(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .@"and", 1, rd, rn, op2);
-    }
-
-    pub fn eor(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .eor, 0, rd, rn, op2);
-    }
-
-    pub fn eors(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .eor, 1, rd, rn, op2);
-    }
-
-    pub fn sub(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .sub, 0, rd, rn, op2);
-    }
-
-    pub fn subs(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .sub, 1, rd, rn, op2);
-    }
-
-    pub fn rsb(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .rsb, 0, rd, rn, op2);
-    }
-
-    pub fn rsbs(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .rsb, 1, rd, rn, op2);
-    }
-
-    pub fn add(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .add, 0, rd, rn, op2);
-    }
-
-    pub fn adds(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .add, 1, rd, rn, op2);
-    }
-
-    pub fn adc(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .adc, 0, rd, rn, op2);
-    }
-
-    pub fn adcs(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .adc, 1, rd, rn, op2);
-    }
-
-    pub fn sbc(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .sbc, 0, rd, rn, op2);
-    }
-
-    pub fn sbcs(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .sbc, 1, rd, rn, op2);
-    }
-
-    pub fn rsc(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .rsc, 0, rd, rn, op2);
-    }
-
-    pub fn rscs(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .rsc, 1, rd, rn, op2);
-    }
-
-    pub fn tst(cond: Condition, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .tst, 1, .r0, rn, op2);
-    }
-
-    pub fn teq(cond: Condition, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .teq, 1, .r0, rn, op2);
-    }
-
-    pub fn cmp(cond: Condition, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .cmp, 1, .r0, rn, op2);
-    }
-
-    pub fn cmn(cond: Condition, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .cmn, 1, .r0, rn, op2);
-    }
-
-    pub fn orr(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .orr, 0, rd, rn, op2);
-    }
-
-    pub fn orrs(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .orr, 1, rd, rn, op2);
-    }
-
-    pub fn mov(cond: Condition, rd: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .mov, 0, rd, .r0, op2);
-    }
-
-    pub fn movs(cond: Condition, rd: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .mov, 1, rd, .r0, op2);
-    }
-
-    pub fn bic(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .bic, 0, rd, rn, op2);
-    }
-
-    pub fn bics(cond: Condition, rd: Register, rn: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .bic, 1, rd, rn, op2);
-    }
-
-    pub fn mvn(cond: Condition, rd: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .mvn, 0, rd, .r0, op2);
-    }
-
-    pub fn mvns(cond: Condition, rd: Register, op2: Operand) Instruction {
-        return dataProcessing(cond, .mvn, 1, rd, .r0, op2);
-    }
-
-    // Integer Saturating Arithmetic
-
-    pub fn qadd(cond: Condition, rd: Register, rm: Register, rn: Register) Instruction {
-        return integerSaturationArithmetic(cond, rd, rm, rn, 0b00);
-    }
-
-    pub fn qsub(cond: Condition, rd: Register, rm: Register, rn: Register) Instruction {
-        return integerSaturationArithmetic(cond, rd, rm, rn, 0b01);
-    }
-
-    pub fn qdadd(cond: Condition, rd: Register, rm: Register, rn: Register) Instruction {
-        return integerSaturationArithmetic(cond, rd, rm, rn, 0b10);
-    }
-
-    pub fn qdsub(cond: Condition, rd: Register, rm: Register, rn: Register) Instruction {
-        return integerSaturationArithmetic(cond, rd, rm, rn, 0b11);
-    }
-
-    // movw and movt
-
-    pub fn movw(cond: Condition, rd: Register, imm: u16) Instruction {
-        return specialMov(cond, rd, imm, false);
-    }
-
-    pub fn movt(cond: Condition, rd: Register, imm: u16) Instruction {
-        return specialMov(cond, rd, imm, true);
-    }
-
-    // PSR transfer
-
-    pub fn mrs(cond: Condition, rd: Register, psr: Psr) Instruction {
-        return Instruction{
-            .data_processing = .{
-                .cond = @intFromEnum(cond),
-                .i = 0,
-                .opcode = if (psr == .spsr) 0b1010 else 0b1000,
-                .s = 0,
-                .rn = 0b1111,
-                .rd = rd.id(),
-                .op2 = 0b0000_0000_0000,
-            },
-        };
-    }
-
-    pub fn msr(cond: Condition, psr: Psr, op: Operand) Instruction {
-        return Instruction{
-            .data_processing = .{
-                .cond = @intFromEnum(cond),
-                .i = 0,
-                .opcode = if (psr == .spsr) 0b1011 else 0b1001,
-                .s = 0,
-                .rn = 0b1111,
-                .rd = 0b1111,
-                .op2 = op.toU12(),
-            },
-        };
-    }
-
-    // Multiply
-
-    pub fn mul(cond: Condition, rd: Register, rn: Register, rm: Register) Instruction {
-        return initMultiply(cond, 0, rd, rn, rm, null);
-    }
-
-    pub fn muls(cond: Condition, rd: Register, rn: Register, rm: Register) Instruction {
-        return initMultiply(cond, 1, rd, rn, rm, null);
-    }
-
-    pub fn mla(cond: Condition, rd: Register, rn: Register, rm: Register, ra: Register) Instruction {
-        return initMultiply(cond, 0, rd, rn, rm, ra);
-    }
-
-    pub fn mlas(cond: Condition, rd: Register, rn: Register, rm: Register, ra: Register) Instruction {
-        return initMultiply(cond, 1, rd, rn, rm, ra);
-    }
-
-    // Multiply long
-
-    pub fn umull(cond: Condition, rdlo: Register, rdhi: Register, rn: Register, rm: Register) Instruction {
-        return multiplyLong(cond, 0, 0, 0, rdhi, rdlo, rm, rn);
-    }
-
-    pub fn umulls(cond: Condition, rdlo: Register, rdhi: Register, rn: Register, rm: Register) Instruction {
-        return multiplyLong(cond, 0, 0, 1, rdhi, rdlo, rm, rn);
-    }
-
-    pub fn umlal(cond: Condition, rdlo: Register, rdhi: Register, rn: Register, rm: Register) Instruction {
-        return multiplyLong(cond, 0, 1, 0, rdhi, rdlo, rm, rn);
-    }
-
-    pub fn umlals(cond: Condition, rdlo: Register, rdhi: Register, rn: Register, rm: Register) Instruction {
-        return multiplyLong(cond, 0, 1, 1, rdhi, rdlo, rm, rn);
-    }
-
-    pub fn smull(cond: Condition, rdlo: Register, rdhi: Register, rn: Register, rm: Register) Instruction {
-        return multiplyLong(cond, 1, 0, 0, rdhi, rdlo, rm, rn);
-    }
-
-    pub fn smulls(cond: Condition, rdlo: Register, rdhi: Register, rn: Register, rm: Register) Instruction {
-        return multiplyLong(cond, 1, 0, 1, rdhi, rdlo, rm, rn);
-    }
-
-    pub fn smlal(cond: Condition, rdlo: Register, rdhi: Register, rn: Register, rm: Register) Instruction {
-        return multiplyLong(cond, 1, 1, 0, rdhi, rdlo, rm, rn);
-    }
-
-    pub fn smlals(cond: Condition, rdlo: Register, rdhi: Register, rn: Register, rm: Register) Instruction {
-        return multiplyLong(cond, 1, 1, 1, rdhi, rdlo, rm, rn);
-    }
-
-    // Signed Multiply (halfwords)
-
-    pub fn smulbb(cond: Condition, rd: Register, rn: Register, rm: Register) Instruction {
-        return signedMultiplyHalfwords(0, 0, cond, rd, rn, rm);
-    }
-
-    pub fn smulbt(cond: Condition, rd: Register, rn: Register, rm: Register) Instruction {
-        return signedMultiplyHalfwords(0, 1, cond, rd, rn, rm);
-    }
-
-    pub fn smultb(cond: Condition, rd: Register, rn: Register, rm: Register) Instruction {
-        return signedMultiplyHalfwords(1, 0, cond, rd, rn, rm);
-    }
-
-    pub fn smultt(cond: Condition, rd: Register, rn: Register, rm: Register) Instruction {
-        return signedMultiplyHalfwords(1, 1, cond, rd, rn, rm);
-    }
-
-    // Bit field extract
-
-    pub fn ubfx(cond: Condition, rd: Register, rn: Register, lsb: u5, width: u6) Instruction {
-        return bitFieldExtract(0b1, cond, rd, rn, lsb, width);
-    }
-
-    pub fn sbfx(cond: Condition, rd: Register, rn: Register, lsb: u5, width: u6) Instruction {
-        return bitFieldExtract(0b0, cond, rd, rn, lsb, width);
-    }
-
-    // Single data transfer
-
-    pub const OffsetArgs = struct {
-        mode: AddressingMode = .offset,
-        positive: bool = true,
-        offset: Offset,
-    };
-
-    pub fn ldr(cond: Condition, rd: Register, rn: Register, args: OffsetArgs) Instruction {
-        return singleDataTransfer(cond, rd, rn, args.offset, args.mode, args.positive, 0, 1);
-    }
-
-    pub fn ldrb(cond: Condition, rd: Register, rn: Register, args: OffsetArgs) Instruction {
-        return singleDataTransfer(cond, rd, rn, args.offset, args.mode, args.positive, 1, 1);
-    }
-
-    pub fn str(cond: Condition, rd: Register, rn: Register, args: OffsetArgs) Instruction {
-        return singleDataTransfer(cond, rd, rn, args.offset, args.mode, args.positive, 0, 0);
-    }
-
-    pub fn strb(cond: Condition, rd: Register, rn: Register, args: OffsetArgs) Instruction {
-        return singleDataTransfer(cond, rd, rn, args.offset, args.mode, args.positive, 1, 0);
-    }
-
-    // Extra load/store
-
-    pub const ExtraLoadStoreOffsetArgs = struct {
-        mode: AddressingMode = .offset,
-        positive: bool = true,
-        offset: ExtraLoadStoreOffset,
-    };
-
-    pub fn strh(cond: Condition, rt: Register, rn: Register, args: ExtraLoadStoreOffsetArgs) Instruction {
-        return extraLoadStore(cond, args.mode, args.positive, 0b0, 0b01, rn, rt, args.offset);
-    }
-
-    pub fn ldrh(cond: Condition, rt: Register, rn: Register, args: ExtraLoadStoreOffsetArgs) Instruction {
-        return extraLoadStore(cond, args.mode, args.positive, 0b1, 0b01, rn, rt, args.offset);
-    }
-
-    pub fn ldrsh(cond: Condition, rt: Register, rn: Register, args: ExtraLoadStoreOffsetArgs) Instruction {
-        return extraLoadStore(cond, args.mode, args.positive, 0b1, 0b11, rn, rt, args.offset);
-    }
-
-    pub fn ldrsb(cond: Condition, rt: Register, rn: Register, args: ExtraLoadStoreOffsetArgs) Instruction {
-        return extraLoadStore(cond, args.mode, args.positive, 0b1, 0b10, rn, rt, args.offset);
-    }
-
-    // Block data transfer
-
-    pub fn ldmda(cond: Condition, rn: Register, write_back: bool, reg_list: RegisterList) Instruction {
-        return blockDataTransfer(cond, rn, reg_list, 0, 0, 0, write_back, 1);
-    }
-
-    pub fn ldmdb(cond: Condition, rn: Register, write_back: bool, reg_list: RegisterList) Instruction {
-        return blockDataTransfer(cond, rn, reg_list, 1, 0, 0, write_back, 1);
-    }
-
-    pub fn ldmib(cond: Condition, rn: Register, write_back: bool, reg_list: RegisterList) Instruction {
-        return blockDataTransfer(cond, rn, reg_list, 1, 1, 0, write_back, 1);
-    }
-
-    pub fn ldmia(cond: Condition, rn: Register, write_back: bool, reg_list: RegisterList) Instruction {
-        return blockDataTransfer(cond, rn, reg_list, 0, 1, 0, write_back, 1);
-    }
-
-    pub const ldmfa = ldmda;
-    pub const ldmea = ldmdb;
-    pub const ldmed = ldmib;
-    pub const ldmfd = ldmia;
-    pub const ldm = ldmia;
-
-    pub fn stmda(cond: Condition, rn: Register, write_back: bool, reg_list: RegisterList) Instruction {
-        return blockDataTransfer(cond, rn, reg_list, 0, 0, 0, write_back, 0);
-    }
-
-    pub fn stmdb(cond: Condition, rn: Register, write_back: bool, reg_list: RegisterList) Instruction {
-        return blockDataTransfer(cond, rn, reg_list, 1, 0, 0, write_back, 0);
-    }
-
-    pub fn stmib(cond: Condition, rn: Register, write_back: bool, reg_list: RegisterList) Instruction {
-        return blockDataTransfer(cond, rn, reg_list, 1, 1, 0, write_back, 0);
-    }
-
-    pub fn stmia(cond: Condition, rn: Register, write_back: bool, reg_list: RegisterList) Instruction {
-        return blockDataTransfer(cond, rn, reg_list, 0, 1, 0, write_back, 0);
-    }
-
-    pub const stmed = stmda;
-    pub const stmfd = stmdb;
-    pub const stmfa = stmib;
-    pub const stmea = stmia;
-    pub const stm = stmia;
-
-    // Branch
-
-    pub fn b(cond: Condition, offset: i26) Instruction {
-        return initBranch(cond, offset, 0);
-    }
-
-    pub fn bl(cond: Condition, offset: i26) Instruction {
-        return initBranch(cond, offset, 1);
-    }
-
-    // Branch and exchange
-
-    pub fn bx(cond: Condition, rn: Register) Instruction {
-        return branchExchange(cond, rn, 0);
-    }
-
-    pub fn blx(cond: Condition, rn: Register) Instruction {
-        return branchExchange(cond, rn, 1);
-    }
-
-    // Supervisor Call
-
-    pub const swi = svc;
-
-    pub fn svc(cond: Condition, comment: u24) Instruction {
-        return supervisorCall(cond, comment);
-    }
-
-    // Breakpoint
-
-    pub fn bkpt(imm: u16) Instruction {
-        return initBreakpoint(imm);
-    }
-
-    // Aliases
-
-    pub fn nop() Instruction {
-        return mov(.al, .r0, Instruction.Operand.reg(.r0, Instruction.Operand.Shift.none));
-    }
-
-    pub fn pop(cond: Condition, args: anytype) Instruction {
-        if (@typeInfo(@TypeOf(args)) != .@"struct") {
-            @compileError("Expected tuple or struct argument, found " ++ @typeName(@TypeOf(args)));
-        }
-
-        if (args.len < 1) {
-            @compileError("Expected at least one register");
-        } else if (args.len == 1) {
-            const reg = args[0];
-            return ldr(cond, reg, .sp, .{
-                .mode = .post_index,
-                .positive = true,
-                .offset = Offset.imm(4),
-            });
-        } else {
-            var register_list: u16 = 0;
-            inline for (args) |arg| {
-                const reg = @as(Register, arg);
-                register_list |= @as(u16, 1) << reg.id();
-            }
-            return ldm(cond, .sp, true, @as(RegisterList, @bitCast(register_list)));
-        }
-    }
-
-    pub fn push(cond: Condition, args: anytype) Instruction {
-        if (@typeInfo(@TypeOf(args)) != .@"struct") {
-            @compileError("Expected tuple or struct argument, found " ++ @typeName(@TypeOf(args)));
-        }
-
-        if (args.len < 1) {
-            @compileError("Expected at least one register");
-        } else if (args.len == 1) {
-            const reg = args[0];
-            return str(cond, reg, .sp, .{
-                .mode = .pre_index,
-                .positive = false,
-                .offset = Offset.imm(4),
-            });
-        } else {
-            var register_list: u16 = 0;
-            inline for (args) |arg| {
-                const reg = @as(Register, arg);
-                register_list |= @as(u16, 1) << reg.id();
-            }
-            return stmdb(cond, .sp, true, @as(RegisterList, @bitCast(register_list)));
-        }
-    }
-
-    pub const ShiftAmount = union(enum) {
-        immediate: u5,
-        register: Register,
-
-        pub fn imm(immediate: u5) ShiftAmount {
-            return .{
-                .immediate = immediate,
-            };
-        }
-
-        pub fn reg(register: Register) ShiftAmount {
-            return .{
-                .register = register,
-            };
-        }
-    };
-
-    pub fn lsl(cond: Condition, rd: Register, rm: Register, shift: ShiftAmount) Instruction {
-        return switch (shift) {
-            .immediate => |imm| mov(cond, rd, Operand.reg(rm, Operand.Shift.imm(imm, .logical_left))),
-            .register => |reg| mov(cond, rd, Operand.reg(rm, Operand.Shift.reg(reg, .logical_left))),
-        };
-    }
-
-    pub fn lsr(cond: Condition, rd: Register, rm: Register, shift: ShiftAmount) Instruction {
-        return switch (shift) {
-            .immediate => |imm| mov(cond, rd, Operand.reg(rm, Operand.Shift.imm(imm, .logical_right))),
-            .register => |reg| mov(cond, rd, Operand.reg(rm, Operand.Shift.reg(reg, .logical_right))),
-        };
-    }
-
-    pub fn asr(cond: Condition, rd: Register, rm: Register, shift: ShiftAmount) Instruction {
-        return switch (shift) {
-            .immediate => |imm| mov(cond, rd, Operand.reg(rm, Operand.Shift.imm(imm, .arithmetic_right))),
-            .register => |reg| mov(cond, rd, Operand.reg(rm, Operand.Shift.reg(reg, .arithmetic_right))),
-        };
-    }
-
-    pub fn ror(cond: Condition, rd: Register, rm: Register, shift: ShiftAmount) Instruction {
-        return switch (shift) {
-            .immediate => |imm| mov(cond, rd, Operand.reg(rm, Operand.Shift.imm(imm, .rotate_right))),
-            .register => |reg| mov(cond, rd, Operand.reg(rm, Operand.Shift.reg(reg, .rotate_right))),
-        };
-    }
-
-    pub fn lsls(cond: Condition, rd: Register, rm: Register, shift: ShiftAmount) Instruction {
-        return switch (shift) {
-            .immediate => |imm| movs(cond, rd, Operand.reg(rm, Operand.Shift.imm(imm, .logical_left))),
-            .register => |reg| movs(cond, rd, Operand.reg(rm, Operand.Shift.reg(reg, .logical_left))),
-        };
-    }
-
-    pub fn lsrs(cond: Condition, rd: Register, rm: Register, shift: ShiftAmount) Instruction {
-        return switch (shift) {
-            .immediate => |imm| movs(cond, rd, Operand.reg(rm, Operand.Shift.imm(imm, .logical_right))),
-            .register => |reg| movs(cond, rd, Operand.reg(rm, Operand.Shift.reg(reg, .logical_right))),
-        };
-    }
-
-    pub fn asrs(cond: Condition, rd: Register, rm: Register, shift: ShiftAmount) Instruction {
-        return switch (shift) {
-            .immediate => |imm| movs(cond, rd, Operand.reg(rm, Operand.Shift.imm(imm, .arithmetic_right))),
-            .register => |reg| movs(cond, rd, Operand.reg(rm, Operand.Shift.reg(reg, .arithmetic_right))),
-        };
-    }
-
-    pub fn rors(cond: Condition, rd: Register, rm: Register, shift: ShiftAmount) Instruction {
-        return switch (shift) {
-            .immediate => |imm| movs(cond, rd, Operand.reg(rm, Operand.Shift.imm(imm, .rotate_right))),
-            .register => |reg| movs(cond, rd, Operand.reg(rm, Operand.Shift.reg(reg, .rotate_right))),
-        };
-    }
-};
-
-test "serialize instructions" {
-    const Testcase = struct {
-        inst: Instruction,
-        expected: u32,
-    };
-
-    const testcases = [_]Testcase{
-        .{ // add r0, r0, r0
-            .inst = Instruction.add(.al, .r0, .r0, Instruction.Operand.reg(.r0, Instruction.Operand.Shift.none)),
-            .expected = 0b1110_00_0_0100_0_0000_0000_00000000_0000,
-        },
-        .{ // mov r4, r2
-            .inst = Instruction.mov(.al, .r4, Instruction.Operand.reg(.r2, Instruction.Operand.Shift.none)),
-            .expected = 0b1110_00_0_1101_0_0000_0100_00000000_0010,
-        },
-        .{ // mov r0, #42
-            .inst = Instruction.mov(.al, .r0, Instruction.Operand.imm(42, 0)),
-            .expected = 0b1110_00_1_1101_0_0000_0000_0000_00101010,
-        },
-        .{ // mrs r5, cpsr
-            .inst = Instruction.mrs(.al, .r5, .cpsr),
-            .expected = 0b1110_00010_0_001111_0101_000000000000,
-        },
-        .{ // mul r0, r1, r2
-            .inst = Instruction.mul(.al, .r0, .r1, .r2),
-            .expected = 0b1110_000000_0_0_0000_0000_0010_1001_0001,
-        },
-        .{ // umlal r0, r1, r5, r6
-            .inst = Instruction.umlal(.al, .r0, .r1, .r5, .r6),
-            .expected = 0b1110_00001_0_1_0_0001_0000_0110_1001_0101,
-        },
-        .{ // ldr r0, [r2, #42]
-            .inst = Instruction.ldr(.al, .r0, .r2, .{
-                .offset = Instruction.Offset.imm(42),
-            }),
-            .expected = 0b1110_01_0_1_1_0_0_1_0010_0000_000000101010,
-        },
-        .{ // str r0, [r3]
-            .inst = Instruction.str(.al, .r0, .r3, .{
-                .offset = Instruction.Offset.none,
-            }),
-            .expected = 0b1110_01_0_1_1_0_0_0_0011_0000_000000000000,
-        },
-        .{ // strh r1, [r5]
-            .inst = Instruction.strh(.al, .r1, .r5, .{
-                .offset = Instruction.ExtraLoadStoreOffset.none,
-            }),
-            .expected = 0b1110_000_1_1_1_0_0_0101_0001_0000_1011_0000,
-        },
-        .{ // b #12
-            .inst = Instruction.b(.al, 12),
-            .expected = 0b1110_101_0_0000_0000_0000_0000_0000_0011,
-        },
-        .{ // bl #-4
-            .inst = Instruction.bl(.al, -4),
-            .expected = 0b1110_101_1_1111_1111_1111_1111_1111_1111,
-        },
-        .{ // bx lr
-            .inst = Instruction.bx(.al, .lr),
-            .expected = 0b1110_0001_0010_1111_1111_1111_0001_1110,
-        },
-        .{ // svc #0
-            .inst = Instruction.svc(.al, 0),
-            .expected = 0b1110_1111_0000_0000_0000_0000_0000_0000,
-        },
-        .{ // bkpt #42
-            .inst = Instruction.bkpt(42),
-            .expected = 0b1110_0001_0010_000000000010_0111_1010,
-        },
-        .{ // stmdb r9, {r0}
-            .inst = Instruction.stmdb(.al, .r9, false, .{ .r0 = true }),
-            .expected = 0b1110_100_1_0_0_0_0_1001_0000000000000001,
-        },
-        .{ // ldmea r4!, {r2, r5}
-            .inst = Instruction.ldmea(.al, .r4, true, .{ .r2 = true, .r5 = true }),
-            .expected = 0b1110_100_1_0_0_1_1_0100_0000000000100100,
-        },
-        .{ // qadd r0, r7, r8
-            .inst = Instruction.qadd(.al, .r0, .r7, .r8),
-            .expected = 0b1110_00010_00_0_1000_0000_0000_0101_0111,
-        },
-        .{ // smulbt r0, r0, r0
-            .inst = Instruction.smulbt(.al, .r0, .r0, .r0),
-            .expected = 0b1110_00010110_0000_0000_0000_1_1_0_0_0000,
-        },
-    };
-
-    for (testcases) |case| {
-        const actual = case.inst.toU32();
-        try testing.expectEqual(case.expected, actual);
-    }
-}
-
-test "aliases" {
-    const Testcase = struct {
-        expected: Instruction,
-        actual: Instruction,
-    };
-
-    const testcases = [_]Testcase{
-        .{ // pop { r6 }
-            .actual = Instruction.pop(.al, .{.r6}),
-            .expected = Instruction.ldr(.al, .r6, .sp, .{
-                .mode = .post_index,
-                .positive = true,
-                .offset = Instruction.Offset.imm(4),
-            }),
-        },
-        .{ // pop { r1, r5 }
-            .actual = Instruction.pop(.al, .{ .r1, .r5 }),
-            .expected = Instruction.ldm(.al, .sp, true, .{ .r1 = true, .r5 = true }),
-        },
-        .{ // push { r3 }
-            .actual = Instruction.push(.al, .{.r3}),
-            .expected = Instruction.str(.al, .r3, .sp, .{
-                .mode = .pre_index,
-                .positive = false,
-                .offset = Instruction.Offset.imm(4),
-            }),
-        },
-        .{ // push { r0, r2 }
-            .actual = Instruction.push(.al, .{ .r0, .r2 }),
-            .expected = Instruction.stmdb(.al, .sp, true, .{ .r0 = true, .r2 = true }),
-        },
-        .{ // lsl r4, r5, #5
-            .actual = Instruction.lsl(.al, .r4, .r5, Instruction.ShiftAmount.imm(5)),
-            .expected = Instruction.mov(.al, .r4, Instruction.Operand.reg(
-                .r5,
-                Instruction.Operand.Shift.imm(5, .logical_left),
-            )),
-        },
-        .{ // asrs r1, r1, r3
-            .actual = Instruction.asrs(.al, .r1, .r1, Instruction.ShiftAmount.reg(.r3)),
-            .expected = Instruction.movs(.al, .r1, Instruction.Operand.reg(
-                .r1,
-                Instruction.Operand.Shift.reg(.r3, .arithmetic_right),
-            )),
-        },
-    };
-
-    for (testcases) |case| {
-        try testing.expectEqual(case.expected.toU32(), case.actual.toU32());
-    }
-}
src/arch/arm/CodeGen.zig
@@ -1,6340 +0,0 @@
-const std = @import("std");
-const builtin = @import("builtin");
-const mem = std.mem;
-const math = std.math;
-const assert = std.debug.assert;
-const codegen = @import("../../codegen.zig");
-const Air = @import("../../Air.zig");
-const Mir = @import("Mir.zig");
-const Emit = @import("Emit.zig");
-const Type = @import("../../Type.zig");
-const Value = @import("../../Value.zig");
-const link = @import("../../link.zig");
-const Zcu = @import("../../Zcu.zig");
-const InternPool = @import("../../InternPool.zig");
-const Compilation = @import("../../Compilation.zig");
-const ErrorMsg = Zcu.ErrorMsg;
-const Target = std.Target;
-const Allocator = mem.Allocator;
-const trace = @import("../../tracy.zig").trace;
-const leb128 = std.leb;
-const log = std.log.scoped(.codegen);
-const build_options = @import("build_options");
-const Alignment = InternPool.Alignment;
-
-const CodeGenError = codegen.CodeGenError;
-
-const bits = @import("bits.zig");
-const abi = @import("abi.zig");
-const errUnionPayloadOffset = codegen.errUnionPayloadOffset;
-const errUnionErrorOffset = codegen.errUnionErrorOffset;
-const RegisterManager = abi.RegisterManager;
-const RegisterLock = RegisterManager.RegisterLock;
-const Register = bits.Register;
-const Instruction = bits.Instruction;
-const Condition = bits.Condition;
-const callee_preserved_regs = abi.callee_preserved_regs;
-const caller_preserved_regs = abi.caller_preserved_regs;
-const c_abi_int_param_regs = abi.c_abi_int_param_regs;
-const c_abi_int_return_regs = abi.c_abi_int_return_regs;
-const gp = abi.RegisterClass.gp;
-
-const InnerError = CodeGenError || error{OutOfRegisters};
-
-pub fn legalizeFeatures(_: *const std.Target) ?*const Air.Legalize.Features {
-    return null;
-}
-
-gpa: Allocator,
-pt: Zcu.PerThread,
-air: Air,
-liveness: Air.Liveness,
-bin_file: *link.File,
-target: *const std.Target,
-func_index: InternPool.Index,
-err_msg: ?*ErrorMsg,
-args: []MCValue,
-ret_mcv: MCValue,
-fn_type: Type,
-arg_index: u32,
-src_loc: Zcu.LazySrcLoc,
-stack_align: u32,
-
-/// MIR Instructions
-mir_instructions: std.MultiArrayList(Mir.Inst) = .{},
-/// MIR extra data
-mir_extra: std.ArrayListUnmanaged(u32) = .empty,
-
-/// Byte offset within the source file of the ending curly.
-end_di_line: u32,
-end_di_column: u32,
-
-/// The value is an offset into the `Function` `code` from the beginning.
-/// To perform the reloc, write 32-bit signed little-endian integer
-/// which is a relative jump, based on the address following the reloc.
-exitlude_jump_relocs: std.ArrayListUnmanaged(usize) = .empty,
-
-reused_operands: std.StaticBitSet(Air.Liveness.bpi - 1) = undefined,
-
-/// We postpone the creation of debug info for function args and locals
-/// until after all Mir instructions have been generated. Only then we
-/// will know saved_regs_stack_space which is necessary in order to
-/// calculate the right stack offsest with respect to the `.fp` register.
-dbg_info_relocs: std.ArrayListUnmanaged(DbgInfoReloc) = .empty,
-
-/// Whenever there is a runtime branch, we push a Branch onto this stack,
-/// and pop it off when the runtime branch joins. This provides an "overlay"
-/// of the table of mappings from instructions to `MCValue` from within the branch.
-/// This way we can modify the `MCValue` for an instruction in different ways
-/// within different branches. Special consideration is needed when a branch
-/// joins with its parent, to make sure all instructions have the same MCValue
-/// across each runtime branch upon joining.
-branch_stack: *std.ArrayList(Branch),
-
-// Key is the block instruction
-blocks: std.AutoHashMapUnmanaged(Air.Inst.Index, BlockData) = .empty,
-
-register_manager: RegisterManager = .{},
-/// Maps offset to what is stored there.
-stack: std.AutoHashMapUnmanaged(u32, StackAllocation) = .empty,
-/// Tracks the current instruction allocated to the compare flags
-cpsr_flags_inst: ?Air.Inst.Index = null,
-
-/// Offset from the stack base, representing the end of the stack frame.
-max_end_stack: u32 = 0,
-/// Represents the current end stack offset. If there is no existing slot
-/// to place a new stack allocation, it goes here, and then bumps `max_end_stack`.
-next_stack_offset: u32 = 0,
-
-saved_regs_stack_space: u32 = 0,
-
-/// Debug field, used to find bugs in the compiler.
-air_bookkeeping: @TypeOf(air_bookkeeping_init) = air_bookkeeping_init,
-
-const air_bookkeeping_init = if (std.debug.runtime_safety) @as(usize, 0) else {};
-
-const MCValue = union(enum) {
-    /// No runtime bits. `void` types, empty structs, u0, enums with 1
-    /// tag, etc.
-    ///
-    /// TODO Look into deleting this tag and using `dead` instead,
-    /// since every use of MCValue.none should be instead looking at
-    /// the type and noticing it is 0 bits.
-    none,
-    /// Control flow will not allow this value to be observed.
-    unreach,
-    /// No more references to this value remain.
-    dead,
-    /// The value is undefined.
-    undef,
-    /// A pointer-sized integer that fits in a register.
-    ///
-    /// If the type is a pointer, this is the pointer address in
-    /// virtual address space.
-    immediate: u32,
-    /// The value is in a target-specific register.
-    register: Register,
-    /// The value is a tuple { wrapped: u32, overflow: u1 } where
-    /// wrapped is stored in the register and the overflow bit is
-    /// stored in the C flag of the CPSR.
-    ///
-    /// This MCValue is only generated by a add_with_overflow or
-    /// sub_with_overflow instruction operating on u32.
-    register_c_flag: Register,
-    /// The value is a tuple { wrapped: i32, overflow: u1 } where
-    /// wrapped is stored in the register and the overflow bit is
-    /// stored in the V flag of the CPSR.
-    ///
-    /// This MCValue is only generated by a add_with_overflow or
-    /// sub_with_overflow instruction operating on i32.
-    register_v_flag: Register,
-    /// The value is in memory at a hard-coded address.
-    ///
-    /// If the type is a pointer, it means the pointer address is at
-    /// this memory location.
-    memory: u64,
-    /// The value is one of the stack variables.
-    ///
-    /// If the type is a pointer, it means the pointer address is in
-    /// the stack at this offset.
-    stack_offset: u32,
-    /// The value is a pointer to one of the stack variables (payload
-    /// is stack offset).
-    ptr_stack_offset: u32,
-    /// The value resides in the N, Z, C, V flags of the Current
-    /// Program Status Register (CPSR). The value is 1 (if the type is
-    /// u1) or true (if the type in bool) iff the specified condition
-    /// is true.
-    cpsr_flags: Condition,
-    /// The value is a function argument passed via the stack.
-    stack_argument_offset: u32,
-};
-
-const Branch = struct {
-    inst_table: std.AutoArrayHashMapUnmanaged(Air.Inst.Index, MCValue) = .empty,
-
-    fn deinit(self: *Branch, gpa: Allocator) void {
-        self.inst_table.deinit(gpa);
-        self.* = undefined;
-    }
-};
-
-const StackAllocation = struct {
-    inst: Air.Inst.Index,
-    /// TODO do we need size? should be determined by inst.ty.abiSize()
-    size: u32,
-};
-
-const BlockData = struct {
-    relocs: std.ArrayListUnmanaged(Mir.Inst.Index),
-    /// The first break instruction encounters `null` here and chooses a
-    /// machine code value for the block result, populating this field.
-    /// Following break instructions encounter that value and use it for
-    /// the location to store their block results.
-    mcv: MCValue,
-};
-
-const BigTomb = struct {
-    function: *Self,
-    inst: Air.Inst.Index,
-    lbt: Air.Liveness.BigTomb,
-
-    fn feed(bt: *BigTomb, op_ref: Air.Inst.Ref) void {
-        const dies = bt.lbt.feed();
-        const op_index = op_ref.toIndex() orelse return;
-        if (!dies) return;
-        bt.function.processDeath(op_index);
-    }
-
-    fn finishAir(bt: *BigTomb, result: MCValue) void {
-        const is_used = !bt.function.liveness.isUnused(bt.inst);
-        if (is_used) {
-            log.debug("%{d} => {}", .{ bt.inst, result });
-            const branch = &bt.function.branch_stack.items[bt.function.branch_stack.items.len - 1];
-            branch.inst_table.putAssumeCapacityNoClobber(bt.inst, result);
-
-            switch (result) {
-                .register => |reg| {
-                    // In some cases (such as bitcast), an operand
-                    // may be the same MCValue as the result. If
-                    // that operand died and was a register, it
-                    // was freed by processDeath. We have to
-                    // "re-allocate" the register.
-                    if (bt.function.register_manager.isRegFree(reg)) {
-                        bt.function.register_manager.getRegAssumeFree(reg, bt.inst);
-                    }
-                },
-                .register_c_flag,
-                .register_v_flag,
-                => |reg| {
-                    if (bt.function.register_manager.isRegFree(reg)) {
-                        bt.function.register_manager.getRegAssumeFree(reg, bt.inst);
-                    }
-                    bt.function.cpsr_flags_inst = bt.inst;
-                },
-                .cpsr_flags => {
-                    bt.function.cpsr_flags_inst = bt.inst;
-                },
-                else => {},
-            }
-        }
-        bt.function.finishAirBookkeeping();
-    }
-};
-
-const DbgInfoReloc = struct {
-    tag: Air.Inst.Tag,
-    ty: Type,
-    name: [:0]const u8,
-    mcv: MCValue,
-
-    fn genDbgInfo(reloc: DbgInfoReloc, function: Self) !void {
-        switch (reloc.tag) {
-            .arg,
-            .dbg_arg_inline,
-            => try reloc.genArgDbgInfo(function),
-
-            .dbg_var_ptr,
-            .dbg_var_val,
-            => try reloc.genVarDbgInfo(function),
-
-            else => unreachable,
-        }
-    }
-
-    fn genArgDbgInfo(reloc: DbgInfoReloc, function: Self) !void {
-        // TODO: Add a pseudo-instruction or something to defer this work until Emit.
-        //       We aren't allowed to interact with linker state here.
-        if (true) return;
-        switch (function.debug_output) {
-            .dwarf => |dw| {
-                const loc: link.File.Dwarf.Loc = switch (reloc.mcv) {
-                    .register => |reg| .{ .reg = reg.dwarfNum() },
-                    .stack_offset,
-                    .stack_argument_offset,
-                    => blk: {
-                        const adjusted_stack_offset = switch (reloc.mcv) {
-                            .stack_offset => |offset| -@as(i32, @intCast(offset)),
-                            .stack_argument_offset => |offset| @as(i32, @intCast(function.saved_regs_stack_space + offset)),
-                            else => unreachable,
-                        };
-                        break :blk .{ .plus = .{
-                            &.{ .reg = 11 },
-                            &.{ .consts = adjusted_stack_offset },
-                        } };
-                    },
-                    else => unreachable, // not a possible argument
-                };
-
-                try dw.genLocalDebugInfo(.local_arg, reloc.name, reloc.ty, loc);
-            },
-            .plan9 => {},
-            .none => {},
-        }
-    }
-
-    fn genVarDbgInfo(reloc: DbgInfoReloc, function: Self) !void {
-        // TODO: Add a pseudo-instruction or something to defer this work until Emit.
-        //       We aren't allowed to interact with linker state here.
-        if (true) return;
-        switch (function.debug_output) {
-            .dwarf => |dw| {
-                const loc: link.File.Dwarf.Loc = switch (reloc.mcv) {
-                    .register => |reg| .{ .reg = reg.dwarfNum() },
-                    .ptr_stack_offset,
-                    .stack_offset,
-                    .stack_argument_offset,
-                    => |offset| blk: {
-                        const adjusted_offset = switch (reloc.mcv) {
-                            .ptr_stack_offset,
-                            .stack_offset,
-                            => -@as(i32, @intCast(offset)),
-                            .stack_argument_offset => @as(i32, @intCast(function.saved_regs_stack_space + offset)),
-                            else => unreachable,
-                        };
-                        break :blk .{ .plus = .{
-                            &.{ .reg = 11 },
-                            &.{ .consts = adjusted_offset },
-                        } };
-                    },
-                    .memory => |address| .{ .constu = address },
-                    .immediate => |x| .{ .constu = x },
-                    .none => .empty,
-                    else => blk: {
-                        log.debug("TODO generate debug info for {}", .{reloc.mcv});
-                        break :blk .empty;
-                    },
-                };
-                try dw.genLocalDebugInfo(.local_var, reloc.name, reloc.ty, loc);
-            },
-            .plan9 => {},
-            .none => {},
-        }
-    }
-};
-
-const Self = @This();
-
-pub fn generate(
-    lf: *link.File,
-    pt: Zcu.PerThread,
-    src_loc: Zcu.LazySrcLoc,
-    func_index: InternPool.Index,
-    air: *const Air,
-    liveness: *const Air.Liveness,
-) CodeGenError!Mir {
-    const zcu = pt.zcu;
-    const gpa = zcu.gpa;
-    const func = zcu.funcInfo(func_index);
-    const func_ty = Type.fromInterned(func.ty);
-    const file_scope = zcu.navFileScope(func.owner_nav);
-    const target = &file_scope.mod.?.resolved_target.result;
-
-    var branch_stack = std.ArrayList(Branch).init(gpa);
-    defer {
-        assert(branch_stack.items.len == 1);
-        branch_stack.items[0].deinit(gpa);
-        branch_stack.deinit();
-    }
-    try branch_stack.append(.{});
-
-    var function: Self = .{
-        .gpa = gpa,
-        .pt = pt,
-        .air = air.*,
-        .liveness = liveness.*,
-        .target = target,
-        .bin_file = lf,
-        .func_index = func_index,
-        .err_msg = null,
-        .args = undefined, // populated after `resolveCallingConventionValues`
-        .ret_mcv = undefined, // populated after `resolveCallingConventionValues`
-        .fn_type = func_ty,
-        .arg_index = 0,
-        .branch_stack = &branch_stack,
-        .src_loc = src_loc,
-        .stack_align = undefined,
-        .end_di_line = func.rbrace_line,
-        .end_di_column = func.rbrace_column,
-    };
-    defer function.stack.deinit(gpa);
-    defer function.blocks.deinit(gpa);
-    defer function.exitlude_jump_relocs.deinit(gpa);
-    defer function.dbg_info_relocs.deinit(gpa);
-
-    var call_info = function.resolveCallingConventionValues(func_ty) catch |err| switch (err) {
-        error.CodegenFail => return error.CodegenFail,
-        else => |e| return e,
-    };
-    defer call_info.deinit(&function);
-
-    function.args = call_info.args;
-    function.ret_mcv = call_info.return_value;
-    function.stack_align = call_info.stack_align;
-    function.max_end_stack = call_info.stack_byte_count;
-
-    function.gen() catch |err| switch (err) {
-        error.CodegenFail => return error.CodegenFail,
-        error.OutOfRegisters => return function.fail("ran out of registers (Zig compiler bug)", .{}),
-        else => |e| return e,
-    };
-
-    for (function.dbg_info_relocs.items) |reloc| {
-        reloc.genDbgInfo(function) catch |err|
-            return function.fail("failed to generate debug info: {s}", .{@errorName(err)});
-    }
-
-    var mir: Mir = .{
-        .instructions = function.mir_instructions.toOwnedSlice(),
-        .extra = &.{}, // fallible, so assign after errdefer
-        .max_end_stack = function.max_end_stack,
-        .saved_regs_stack_space = function.saved_regs_stack_space,
-    };
-    errdefer mir.deinit(gpa);
-    mir.extra = try function.mir_extra.toOwnedSlice(gpa);
-    return mir;
-}
-
-fn addInst(self: *Self, inst: Mir.Inst) error{OutOfMemory}!Mir.Inst.Index {
-    const gpa = self.gpa;
-
-    try self.mir_instructions.ensureUnusedCapacity(gpa, 1);
-
-    const result_index: Mir.Inst.Index = @intCast(self.mir_instructions.len);
-    self.mir_instructions.appendAssumeCapacity(inst);
-    return result_index;
-}
-
-fn addNop(self: *Self) error{OutOfMemory}!Mir.Inst.Index {
-    return try self.addInst(.{
-        .tag = .nop,
-        .data = .{ .nop = {} },
-    });
-}
-
-pub fn addExtra(self: *Self, extra: anytype) Allocator.Error!u32 {
-    const fields = std.meta.fields(@TypeOf(extra));
-    try self.mir_extra.ensureUnusedCapacity(self.gpa, fields.len);
-    return self.addExtraAssumeCapacity(extra);
-}
-
-pub fn addExtraAssumeCapacity(self: *Self, extra: anytype) u32 {
-    const fields = std.meta.fields(@TypeOf(extra));
-    const result: u32 = @intCast(self.mir_extra.items.len);
-    inline for (fields) |field| {
-        self.mir_extra.appendAssumeCapacity(switch (field.type) {
-            u32 => @field(extra, field.name),
-            i32 => @bitCast(@field(extra, field.name)),
-            else => @compileError("bad field type"),
-        });
-    }
-    return result;
-}
-
-fn gen(self: *Self) !void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const cc = self.fn_type.fnCallingConvention(zcu);
-    if (cc != .naked) {
-        // push {fp, lr}
-        const push_reloc = try self.addNop();
-
-        // mov fp, sp
-        _ = try self.addInst(.{
-            .tag = .mov,
-            .data = .{ .r_op_mov = .{
-                .rd = .fp,
-                .op = Instruction.Operand.reg(.sp, Instruction.Operand.Shift.none),
-            } },
-        });
-
-        // sub sp, sp, #reloc
-        const sub_reloc = try self.addNop();
-
-        // The sub_sp_scratch_r4 instruction may use r4, so we mark r4
-        // as allocated by this function.
-        const index = RegisterManager.indexOfRegIntoTracked(.r4).?;
-        self.register_manager.allocated_registers.set(index);
-
-        if (self.ret_mcv == .stack_offset) {
-            // The address of where to store the return value is in
-            // r0. As this register might get overwritten along the
-            // way, save the address to the stack.
-            const stack_offset = try self.allocMem(4, .@"4", null);
-
-            try self.genSetStack(Type.usize, stack_offset, MCValue{ .register = .r0 });
-            self.ret_mcv = MCValue{ .stack_offset = stack_offset };
-        }
-
-        for (self.args, 0..) |*arg, arg_index| {
-            // Copy register arguments to the stack
-            switch (arg.*) {
-                .register => |reg| {
-                    // The first AIR instructions of the main body are guaranteed
-                    // to be the functions arguments
-                    const inst = self.air.getMainBody()[arg_index];
-                    assert(self.air.instructions.items(.tag)[@intFromEnum(inst)] == .arg);
-
-                    const ty = self.typeOfIndex(inst);
-
-                    const abi_size: u32 = @intCast(ty.abiSize(zcu));
-                    const abi_align = ty.abiAlignment(zcu);
-                    const stack_offset = try self.allocMem(abi_size, abi_align, inst);
-                    try self.genSetStack(ty, stack_offset, MCValue{ .register = reg });
-
-                    arg.* = MCValue{ .stack_offset = stack_offset };
-                },
-                else => {},
-            }
-        }
-
-        _ = try self.addInst(.{
-            .tag = .dbg_prologue_end,
-            .cond = undefined,
-            .data = .{ .nop = {} },
-        });
-
-        try self.genBody(self.air.getMainBody());
-
-        // Backpatch push callee saved regs
-        var saved_regs = Instruction.RegisterList{
-            .r11 = true, // fp
-            .r14 = true, // lr
-        };
-        self.saved_regs_stack_space = 8;
-        inline for (callee_preserved_regs) |reg| {
-            if (self.register_manager.isRegAllocated(reg)) {
-                @field(saved_regs, @tagName(reg)) = true;
-                self.saved_regs_stack_space += 4;
-            }
-        }
-        self.mir_instructions.set(push_reloc, .{
-            .tag = .push,
-            .data = .{ .register_list = saved_regs },
-        });
-
-        // Backpatch stack offset
-        const total_stack_size = self.max_end_stack + self.saved_regs_stack_space;
-        const aligned_total_stack_end = mem.alignForward(u32, total_stack_size, self.stack_align);
-        const stack_size = aligned_total_stack_end - self.saved_regs_stack_space;
-        self.max_end_stack = stack_size;
-        self.mir_instructions.set(sub_reloc, .{
-            .tag = .sub_sp_scratch_r4,
-            .data = .{ .imm32 = stack_size },
-        });
-
-        _ = try self.addInst(.{
-            .tag = .dbg_epilogue_begin,
-            .cond = undefined,
-            .data = .{ .nop = {} },
-        });
-
-        // exitlude jumps
-        if (self.exitlude_jump_relocs.items.len > 0 and
-            self.exitlude_jump_relocs.items[self.exitlude_jump_relocs.items.len - 1] == self.mir_instructions.len - 2)
-        {
-            // If the last Mir instruction (apart from the
-            // dbg_epilogue_begin) is the last exitlude jump
-            // relocation (which would just jump one instruction
-            // further), it can be safely removed
-            self.mir_instructions.orderedRemove(self.exitlude_jump_relocs.pop().?);
-        }
-
-        for (self.exitlude_jump_relocs.items) |jmp_reloc| {
-            self.mir_instructions.set(jmp_reloc, .{
-                .tag = .b,
-                .data = .{ .inst = @intCast(self.mir_instructions.len) },
-            });
-        }
-
-        // Epilogue: pop callee saved registers (swap lr with pc in saved_regs)
-        saved_regs.r14 = false; // lr
-        saved_regs.r15 = true; // pc
-
-        // mov sp, fp
-        _ = try self.addInst(.{
-            .tag = .mov,
-            .data = .{ .r_op_mov = .{
-                .rd = .sp,
-                .op = Instruction.Operand.reg(.fp, Instruction.Operand.Shift.none),
-            } },
-        });
-
-        // pop {fp, pc}
-        _ = try self.addInst(.{
-            .tag = .pop,
-            .data = .{ .register_list = saved_regs },
-        });
-    } else {
-        _ = try self.addInst(.{
-            .tag = .dbg_prologue_end,
-            .cond = undefined,
-            .data = .{ .nop = {} },
-        });
-
-        try self.genBody(self.air.getMainBody());
-
-        _ = try self.addInst(.{
-            .tag = .dbg_epilogue_begin,
-            .cond = undefined,
-            .data = .{ .nop = {} },
-        });
-    }
-
-    // Drop them off at the rbrace.
-    _ = try self.addInst(.{
-        .tag = .dbg_line,
-        .cond = undefined,
-        .data = .{ .dbg_line_column = .{
-            .line = self.end_di_line,
-            .column = self.end_di_column,
-        } },
-    });
-}
-
-fn genBody(self: *Self, body: []const Air.Inst.Index) InnerError!void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const ip = &zcu.intern_pool;
-    const air_tags = self.air.instructions.items(.tag);
-
-    for (body) |inst| {
-        // TODO: remove now-redundant isUnused calls from AIR handler functions
-        if (self.liveness.isUnused(inst) and !self.air.mustLower(inst, ip))
-            continue;
-
-        const old_air_bookkeeping = self.air_bookkeeping;
-        try self.ensureProcessDeathCapacity(Air.Liveness.bpi);
-
-        self.reused_operands = @TypeOf(self.reused_operands).initEmpty();
-        switch (air_tags[@intFromEnum(inst)]) {
-            // zig fmt: off
-            .add,            => try self.airBinOp(inst, .add),
-            .add_wrap        => try self.airBinOp(inst, .add_wrap),
-            .sub,            => try self.airBinOp(inst, .sub),
-            .sub_wrap        => try self.airBinOp(inst, .sub_wrap),
-            .mul             => try self.airBinOp(inst, .mul),
-            .mul_wrap        => try self.airBinOp(inst, .mul_wrap),
-            .shl             => try self.airBinOp(inst, .shl),
-            .shl_exact       => try self.airBinOp(inst, .shl_exact),
-            .bool_and        => try self.airBinOp(inst, .bool_and),
-            .bool_or         => try self.airBinOp(inst, .bool_or),
-            .bit_and         => try self.airBinOp(inst, .bit_and),
-            .bit_or          => try self.airBinOp(inst, .bit_or),
-            .xor             => try self.airBinOp(inst, .xor),
-            .shr             => try self.airBinOp(inst, .shr),
-            .shr_exact       => try self.airBinOp(inst, .shr_exact),
-            .div_float       => try self.airBinOp(inst, .div_float),
-            .div_trunc       => try self.airBinOp(inst, .div_trunc),
-            .div_floor       => try self.airBinOp(inst, .div_floor),
-            .div_exact       => try self.airBinOp(inst, .div_exact),
-            .rem             => try self.airBinOp(inst, .rem),
-            .mod             => try self.airBinOp(inst, .mod),
-
-            .ptr_add => try self.airPtrArithmetic(inst, .ptr_add),
-            .ptr_sub => try self.airPtrArithmetic(inst, .ptr_sub),
-
-            .min => try self.airMinMax(inst),
-            .max => try self.airMinMax(inst),
-
-            .add_sat         => try self.airAddSat(inst),
-            .sub_sat         => try self.airSubSat(inst),
-            .mul_sat         => try self.airMulSat(inst),
-            .shl_sat         => try self.airShlSat(inst),
-            .slice           => try self.airSlice(inst),
-
-            .sqrt,
-            .sin,
-            .cos,
-            .tan,
-            .exp,
-            .exp2,
-            .log,
-            .log2,
-            .log10,
-            .floor,
-            .ceil,
-            .round,
-            .trunc_float,
-            .neg,
-            => try self.airUnaryMath(inst),
-
-            .add_with_overflow => try self.airOverflow(inst),
-            .sub_with_overflow => try self.airOverflow(inst),
-            .mul_with_overflow => try self.airMulWithOverflow(inst),
-            .shl_with_overflow => try self.airShlWithOverflow(inst),
-
-            .cmp_lt  => try self.airCmp(inst, .lt),
-            .cmp_lte => try self.airCmp(inst, .lte),
-            .cmp_eq  => try self.airCmp(inst, .eq),
-            .cmp_gte => try self.airCmp(inst, .gte),
-            .cmp_gt  => try self.airCmp(inst, .gt),
-            .cmp_neq => try self.airCmp(inst, .neq),
-
-            .cmp_vector => try self.airCmpVector(inst),
-            .cmp_lt_errors_len => try self.airCmpLtErrorsLen(inst),
-
-            .alloc           => try self.airAlloc(inst),
-            .ret_ptr         => try self.airRetPtr(inst),
-            .arg             => try self.airArg(inst),
-            .assembly        => try self.airAsm(inst),
-            .bitcast         => try self.airBitCast(inst),
-            .block           => try self.airBlock(inst),
-            .br              => try self.airBr(inst),
-            .repeat          => return self.fail("TODO implement `repeat`", .{}),
-            .switch_dispatch => return self.fail("TODO implement `switch_dispatch`", .{}),
-            .trap            => try self.airTrap(),
-            .breakpoint      => try self.airBreakpoint(),
-            .ret_addr        => try self.airRetAddr(inst),
-            .frame_addr      => try self.airFrameAddress(inst),
-            .cond_br         => try self.airCondBr(inst),
-            .fptrunc         => try self.airFptrunc(inst),
-            .fpext           => try self.airFpext(inst),
-            .intcast         => try self.airIntCast(inst),
-            .trunc           => try self.airTrunc(inst),
-            .is_non_null     => try self.airIsNonNull(inst),
-            .is_non_null_ptr => try self.airIsNonNullPtr(inst),
-            .is_null         => try self.airIsNull(inst),
-            .is_null_ptr     => try self.airIsNullPtr(inst),
-            .is_non_err      => try self.airIsNonErr(inst),
-            .is_non_err_ptr  => try self.airIsNonErrPtr(inst),
-            .is_err          => try self.airIsErr(inst),
-            .is_err_ptr      => try self.airIsErrPtr(inst),
-            .load            => try self.airLoad(inst),
-            .loop            => try self.airLoop(inst),
-            .not             => try self.airNot(inst),
-            .ret             => try self.airRet(inst),
-            .ret_safe        => try self.airRet(inst), // TODO
-            .ret_load        => try self.airRetLoad(inst),
-            .store           => try self.airStore(inst, false),
-            .store_safe      => try self.airStore(inst, true),
-            .struct_field_ptr=> try self.airStructFieldPtr(inst),
-            .struct_field_val=> try self.airStructFieldVal(inst),
-            .array_to_slice  => try self.airArrayToSlice(inst),
-            .float_from_int    => try self.airFloatFromInt(inst),
-            .int_from_float    => try self.airIntFromFloat(inst),
-            .cmpxchg_strong  => try self.airCmpxchg(inst),
-            .cmpxchg_weak    => try self.airCmpxchg(inst),
-            .atomic_rmw      => try self.airAtomicRmw(inst),
-            .atomic_load     => try self.airAtomicLoad(inst),
-            .memcpy          => try self.airMemcpy(inst),
-            .memmove         => try self.airMemmove(inst),
-            .memset          => try self.airMemset(inst, false),
-            .memset_safe     => try self.airMemset(inst, true),
-            .set_union_tag   => try self.airSetUnionTag(inst),
-            .get_union_tag   => try self.airGetUnionTag(inst),
-            .clz             => try self.airClz(inst),
-            .ctz             => try self.airCtz(inst),
-            .popcount        => try self.airPopcount(inst),
-            .abs             => try self.airAbs(inst),
-            .byte_swap       => try self.airByteSwap(inst),
-            .bit_reverse     => try self.airBitReverse(inst),
-            .tag_name        => try self.airTagName(inst),
-            .error_name      => try self.airErrorName(inst),
-            .splat           => try self.airSplat(inst),
-            .select          => try self.airSelect(inst),
-            .shuffle_one     => try self.airShuffleOne(inst),
-            .shuffle_two     => try self.airShuffleTwo(inst),
-            .reduce          => try self.airReduce(inst),
-            .aggregate_init  => try self.airAggregateInit(inst),
-            .union_init      => try self.airUnionInit(inst),
-            .prefetch        => try self.airPrefetch(inst),
-            .mul_add         => try self.airMulAdd(inst),
-            .addrspace_cast  => return self.fail("TODO implement addrspace_cast", .{}),
-
-            .@"try"          => try self.airTry(inst),
-            .try_cold        => try self.airTry(inst),
-            .try_ptr         => try self.airTryPtr(inst),
-            .try_ptr_cold    => try self.airTryPtr(inst),
-
-            .dbg_stmt         => try self.airDbgStmt(inst),
-            .dbg_empty_stmt   => self.finishAirBookkeeping(),
-            .dbg_inline_block => try self.airDbgInlineBlock(inst),
-            .dbg_var_ptr,
-            .dbg_var_val,
-            .dbg_arg_inline,
-            => try self.airDbgVar(inst),
-
-            .call              => try self.airCall(inst, .auto),
-            .call_always_tail  => try self.airCall(inst, .always_tail),
-            .call_never_tail   => try self.airCall(inst, .never_tail),
-            .call_never_inline => try self.airCall(inst, .never_inline),
-
-            .atomic_store_unordered => try self.airAtomicStore(inst, .unordered),
-            .atomic_store_monotonic => try self.airAtomicStore(inst, .monotonic),
-            .atomic_store_release   => try self.airAtomicStore(inst, .release),
-            .atomic_store_seq_cst   => try self.airAtomicStore(inst, .seq_cst),
-
-            .struct_field_ptr_index_0 => try self.airStructFieldPtrIndex(inst, 0),
-            .struct_field_ptr_index_1 => try self.airStructFieldPtrIndex(inst, 1),
-            .struct_field_ptr_index_2 => try self.airStructFieldPtrIndex(inst, 2),
-            .struct_field_ptr_index_3 => try self.airStructFieldPtrIndex(inst, 3),
-
-            .field_parent_ptr => try self.airFieldParentPtr(inst),
-
-            .switch_br       => try self.airSwitch(inst),
-            .loop_switch_br  => return self.fail("TODO implement `loop_switch_br`", .{}),
-            .slice_ptr       => try self.airSlicePtr(inst),
-            .slice_len       => try self.airSliceLen(inst),
-
-            .ptr_slice_len_ptr => try self.airPtrSliceLenPtr(inst),
-            .ptr_slice_ptr_ptr => try self.airPtrSlicePtrPtr(inst),
-
-            .array_elem_val      => try self.airArrayElemVal(inst),
-            .slice_elem_val      => try self.airSliceElemVal(inst),
-            .slice_elem_ptr      => try self.airSliceElemPtr(inst),
-            .ptr_elem_val        => try self.airPtrElemVal(inst),
-            .ptr_elem_ptr        => try self.airPtrElemPtr(inst),
-
-            .inferred_alloc, .inferred_alloc_comptime => unreachable,
-            .unreach  => self.finishAirBookkeeping(),
-
-            .optional_payload           => try self.airOptionalPayload(inst),
-            .optional_payload_ptr       => try self.airOptionalPayloadPtr(inst),
-            .optional_payload_ptr_set   => try self.airOptionalPayloadPtrSet(inst),
-            .unwrap_errunion_err        => try self.airUnwrapErrErr(inst),
-            .unwrap_errunion_payload    => try self.airUnwrapErrPayload(inst),
-            .unwrap_errunion_err_ptr    => try self.airUnwrapErrErrPtr(inst),
-            .unwrap_errunion_payload_ptr=> try self.airUnwrapErrPayloadPtr(inst),
-            .errunion_payload_ptr_set   => try self.airErrUnionPayloadPtrSet(inst),
-            .err_return_trace           => try self.airErrReturnTrace(inst),
-            .set_err_return_trace       => try self.airSetErrReturnTrace(inst),
-            .save_err_return_trace_index=> try self.airSaveErrReturnTraceIndex(inst),
-
-            .wrap_optional         => try self.airWrapOptional(inst),
-            .wrap_errunion_payload => try self.airWrapErrUnionPayload(inst),
-            .wrap_errunion_err     => try self.airWrapErrUnionErr(inst),
-
-            .add_optimized,
-            .sub_optimized,
-            .mul_optimized,
-            .div_float_optimized,
-            .div_trunc_optimized,
-            .div_floor_optimized,
-            .div_exact_optimized,
-            .rem_optimized,
-            .mod_optimized,
-            .neg_optimized,
-            .cmp_lt_optimized,
-            .cmp_lte_optimized,
-            .cmp_eq_optimized,
-            .cmp_gte_optimized,
-            .cmp_gt_optimized,
-            .cmp_neq_optimized,
-            .cmp_vector_optimized,
-            .reduce_optimized,
-            .int_from_float_optimized,
-            => return self.fail("TODO implement optimized float mode", .{}),
-
-            .add_safe,
-            .sub_safe,
-            .mul_safe,
-            .intcast_safe,
-            .int_from_float_safe,
-            .int_from_float_optimized_safe,
-            => return self.fail("TODO implement safety_checked_instructions", .{}),
-
-            .is_named_enum_value => return self.fail("TODO implement is_named_enum_value", .{}),
-            .error_set_has_value => return self.fail("TODO implement error_set_has_value", .{}),
-            .vector_store_elem => return self.fail("TODO implement vector_store_elem", .{}),
-            .runtime_nav_ptr => return self.fail("TODO implement runtime_nav_ptr", .{}),
-
-            .c_va_arg => return self.fail("TODO implement c_va_arg", .{}),
-            .c_va_copy => return self.fail("TODO implement c_va_copy", .{}),
-            .c_va_end => return self.fail("TODO implement c_va_end", .{}),
-            .c_va_start => return self.fail("TODO implement c_va_start", .{}),
-
-            .wasm_memory_size => unreachable,
-            .wasm_memory_grow => unreachable,
-
-            .work_item_id => unreachable,
-            .work_group_size => unreachable,
-            .work_group_id => unreachable,
-            // zig fmt: on
-        }
-
-        assert(!self.register_manager.lockedRegsExist());
-
-        if (std.debug.runtime_safety) {
-            if (self.air_bookkeeping < old_air_bookkeeping + 1) {
-                std.debug.panic("in codegen.zig, handling of AIR instruction %{d} ('{}') did not do proper bookkeeping. Look for a missing call to finishAir.", .{ inst, air_tags[@intFromEnum(inst)] });
-            }
-        }
-    }
-}
-
-/// Asserts there is already capacity to insert into top branch inst_table.
-fn processDeath(self: *Self, inst: Air.Inst.Index) void {
-    // When editing this function, note that the logic must synchronize with `reuseOperand`.
-    const prev_value = self.getResolvedInstValue(inst);
-    const branch = &self.branch_stack.items[self.branch_stack.items.len - 1];
-    branch.inst_table.putAssumeCapacity(inst, .dead);
-    switch (prev_value) {
-        .register => |reg| {
-            self.register_manager.freeReg(reg);
-        },
-        .register_c_flag,
-        .register_v_flag,
-        => |reg| {
-            self.register_manager.freeReg(reg);
-            self.cpsr_flags_inst = null;
-        },
-        .cpsr_flags => {
-            self.cpsr_flags_inst = null;
-        },
-        else => {}, // TODO process stack allocation death
-    }
-}
-
-/// Called when there are no operands, and the instruction is always unreferenced.
-fn finishAirBookkeeping(self: *Self) void {
-    if (std.debug.runtime_safety) {
-        self.air_bookkeeping += 1;
-    }
-}
-
-fn finishAir(self: *Self, inst: Air.Inst.Index, result: MCValue, operands: [Air.Liveness.bpi - 1]Air.Inst.Ref) void {
-    const tomb_bits = self.liveness.getTombBits(inst);
-    for (0.., operands) |op_index, op| {
-        if (tomb_bits & @as(Air.Liveness.Bpi, 1) << @intCast(op_index) == 0) continue;
-        if (self.reused_operands.isSet(op_index)) continue;
-        self.processDeath(op.toIndexAllowNone() orelse continue);
-    }
-    if (tomb_bits & 1 << (Air.Liveness.bpi - 1) == 0) {
-        log.debug("%{d} => {}", .{ inst, result });
-        const branch = &self.branch_stack.items[self.branch_stack.items.len - 1];
-        branch.inst_table.putAssumeCapacityNoClobber(inst, result);
-
-        switch (result) {
-            .register => |reg| {
-                // In some cases (such as bitcast), an operand
-                // may be the same MCValue as the result. If
-                // that operand died and was a register, it
-                // was freed by processDeath. We have to
-                // "re-allocate" the register.
-                if (self.register_manager.isRegFree(reg)) {
-                    self.register_manager.getRegAssumeFree(reg, inst);
-                }
-            },
-            .register_c_flag,
-            .register_v_flag,
-            => |reg| {
-                if (self.register_manager.isRegFree(reg)) {
-                    self.register_manager.getRegAssumeFree(reg, inst);
-                }
-                self.cpsr_flags_inst = inst;
-            },
-            .cpsr_flags => {
-                self.cpsr_flags_inst = inst;
-            },
-            else => {},
-        }
-    }
-    self.finishAirBookkeeping();
-}
-
-fn ensureProcessDeathCapacity(self: *Self, additional_count: usize) !void {
-    const table = &self.branch_stack.items[self.branch_stack.items.len - 1].inst_table;
-    try table.ensureUnusedCapacity(self.gpa, additional_count);
-}
-
-fn allocMem(
-    self: *Self,
-    abi_size: u32,
-    abi_align: Alignment,
-    maybe_inst: ?Air.Inst.Index,
-) !u32 {
-    assert(abi_size > 0);
-    assert(abi_align != .none);
-
-    // TODO find a free slot instead of always appending
-    const offset: u32 = @intCast(abi_align.forward(self.next_stack_offset) + abi_size);
-    self.next_stack_offset = offset;
-    self.max_end_stack = @max(self.max_end_stack, self.next_stack_offset);
-
-    if (maybe_inst) |inst| {
-        try self.stack.putNoClobber(self.gpa, offset, .{
-            .inst = inst,
-            .size = abi_size,
-        });
-    }
-
-    return offset;
-}
-
-/// Use a pointer instruction as the basis for allocating stack memory.
-fn allocMemPtr(self: *Self, inst: Air.Inst.Index) !u32 {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const elem_ty = self.typeOfIndex(inst).childType(zcu);
-
-    if (!elem_ty.hasRuntimeBits(zcu)) {
-        // As this stack item will never be dereferenced at runtime,
-        // return the stack offset 0. Stack offset 0 will be where all
-        // zero-sized stack allocations live as non-zero-sized
-        // allocations will always have an offset > 0.
-        return 0;
-    }
-
-    const abi_size = math.cast(u32, elem_ty.abiSize(zcu)) orelse {
-        return self.fail("type '{}' too big to fit into stack frame", .{elem_ty.fmt(pt)});
-    };
-    // TODO swap this for inst.ty.ptrAlign
-    const abi_align = elem_ty.abiAlignment(zcu);
-
-    return self.allocMem(abi_size, abi_align, inst);
-}
-
-fn allocRegOrMem(self: *Self, elem_ty: Type, reg_ok: bool, maybe_inst: ?Air.Inst.Index) !MCValue {
-    const pt = self.pt;
-    const abi_size = math.cast(u32, elem_ty.abiSize(pt.zcu)) orelse {
-        return self.fail("type '{}' too big to fit into stack frame", .{elem_ty.fmt(pt)});
-    };
-    const abi_align = elem_ty.abiAlignment(pt.zcu);
-
-    if (reg_ok) {
-        // Make sure the type can fit in a register before we try to allocate one.
-        const ptr_bits = self.target.ptrBitWidth();
-        const ptr_bytes: u64 = @divExact(ptr_bits, 8);
-        if (abi_size <= ptr_bytes) {
-            if (self.register_manager.tryAllocReg(maybe_inst, gp)) |reg| {
-                return MCValue{ .register = reg };
-            }
-        }
-    }
-
-    const stack_offset = try self.allocMem(abi_size, abi_align, maybe_inst);
-    return MCValue{ .stack_offset = stack_offset };
-}
-
-pub fn spillInstruction(self: *Self, reg: Register, inst: Air.Inst.Index) !void {
-    const stack_mcv = try self.allocRegOrMem(self.typeOfIndex(inst), false, inst);
-    log.debug("spilling {} (%{d}) to stack mcv {any}", .{ reg, inst, stack_mcv });
-
-    const reg_mcv = self.getResolvedInstValue(inst);
-    switch (reg_mcv) {
-        .register,
-        .register_c_flag,
-        .register_v_flag,
-        => |r| assert(r == reg),
-        else => unreachable, // not a register
-    }
-
-    const branch = &self.branch_stack.items[self.branch_stack.items.len - 1];
-    try branch.inst_table.put(self.gpa, inst, stack_mcv);
-    try self.genSetStack(self.typeOfIndex(inst), stack_mcv.stack_offset, reg_mcv);
-}
-
-/// Save the current instruction stored in the compare flags if
-/// occupied
-fn spillCompareFlagsIfOccupied(self: *Self) !void {
-    if (self.cpsr_flags_inst) |inst_to_save| {
-        const ty = self.typeOfIndex(inst_to_save);
-        const mcv = self.getResolvedInstValue(inst_to_save);
-        const new_mcv = switch (mcv) {
-            .cpsr_flags => try self.allocRegOrMem(ty, true, inst_to_save),
-            .register_c_flag,
-            .register_v_flag,
-            => try self.allocRegOrMem(ty, false, inst_to_save),
-            else => unreachable, // mcv doesn't occupy the compare flags
-        };
-
-        try self.setRegOrMem(self.typeOfIndex(inst_to_save), new_mcv, mcv);
-        log.debug("spilling {d} to mcv {any}", .{ inst_to_save, new_mcv });
-
-        const branch = &self.branch_stack.items[self.branch_stack.items.len - 1];
-        try branch.inst_table.put(self.gpa, inst_to_save, new_mcv);
-
-        self.cpsr_flags_inst = null;
-
-        // TODO consolidate with register manager and spillInstruction
-        // this call should really belong in the register manager!
-        switch (mcv) {
-            .register_c_flag,
-            .register_v_flag,
-            => |reg| self.register_manager.freeReg(reg),
-            else => {},
-        }
-    }
-}
-
-/// Copies a value to a register without tracking the register. The register is not considered
-/// allocated. A second call to `copyToTmpRegister` may return the same register.
-/// This can have a side effect of spilling instructions to the stack to free up a register.
-fn copyToTmpRegister(self: *Self, ty: Type, mcv: MCValue) !Register {
-    const reg = try self.register_manager.allocReg(null, gp);
-    try self.genSetReg(ty, reg, mcv);
-    return reg;
-}
-
-fn airAlloc(self: *Self, inst: Air.Inst.Index) !void {
-    const stack_offset = try self.allocMemPtr(inst);
-    return self.finishAir(inst, .{ .ptr_stack_offset = stack_offset }, .{ .none, .none, .none });
-}
-
-fn airRetPtr(self: *Self, inst: Air.Inst.Index) !void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const result: MCValue = switch (self.ret_mcv) {
-        .none, .register => .{ .ptr_stack_offset = try self.allocMemPtr(inst) },
-        .stack_offset => blk: {
-            // self.ret_mcv is an address to where this function
-            // should store its result into
-            const ret_ty = self.fn_type.fnReturnType(zcu);
-            const ptr_ty = try pt.singleMutPtrType(ret_ty);
-
-            // addr_reg will contain the address of where to store the
-            // result into
-            const addr_reg = try self.copyToTmpRegister(ptr_ty, self.ret_mcv);
-            break :blk .{ .register = addr_reg };
-        },
-        else => unreachable, // invalid return result
-    };
-
-    return self.finishAir(inst, result, .{ .none, .none, .none });
-}
-
-fn airFptrunc(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement airFptrunc for {}", .{self.target.cpu.arch});
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airFpext(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement airFpext for {}", .{self.target.cpu.arch});
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airIntCast(self: *Self, inst: Air.Inst.Index) !void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    if (self.liveness.isUnused(inst))
-        return self.finishAir(inst, .dead, .{ ty_op.operand, .none, .none });
-
-    const operand = try self.resolveInst(ty_op.operand);
-    const operand_ty = self.typeOf(ty_op.operand);
-    const dest_ty = self.typeOfIndex(inst);
-
-    const operand_abi_size = operand_ty.abiSize(zcu);
-    const dest_abi_size = dest_ty.abiSize(zcu);
-    const info_a = operand_ty.intInfo(zcu);
-    const info_b = dest_ty.intInfo(zcu);
-
-    const dst_mcv: MCValue = blk: {
-        if (info_a.bits == info_b.bits) {
-            break :blk operand;
-        }
-        if (operand_abi_size > 4 or dest_abi_size > 4) {
-            return self.fail("TODO implement intCast for abi sizes larger than 4", .{});
-        }
-
-        const operand_lock: ?RegisterLock = switch (operand) {
-            .register => |reg| self.register_manager.lockRegAssumeUnused(reg),
-            else => null,
-        };
-        defer if (operand_lock) |lock| self.register_manager.unlockReg(lock);
-
-        const reg = try self.register_manager.allocReg(inst, gp);
-        try self.genSetReg(dest_ty, reg, operand);
-        break :blk MCValue{ .register = reg };
-    };
-
-    return self.finishAir(inst, dst_mcv, .{ ty_op.operand, .none, .none });
-}
-
-fn truncRegister(
-    self: *Self,
-    operand_reg: Register,
-    dest_reg: Register,
-    int_signedness: std.builtin.Signedness,
-    int_bits: u16,
-) !void {
-    // TODO check if sxtb/uxtb/sxth/uxth are more efficient
-    _ = try self.addInst(.{
-        .tag = switch (int_signedness) {
-            .signed => .sbfx,
-            .unsigned => .ubfx,
-        },
-        .data = .{ .rr_lsb_width = .{
-            .rd = dest_reg,
-            .rn = operand_reg,
-            .lsb = 0,
-            .width = @intCast(int_bits),
-        } },
-    });
-}
-
-/// Asserts that both operand_ty and dest_ty are integer types
-fn trunc(
-    self: *Self,
-    maybe_inst: ?Air.Inst.Index,
-    operand_bind: ReadArg.Bind,
-    operand_ty: Type,
-    dest_ty: Type,
-) !MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const info_a = operand_ty.intInfo(zcu);
-    const info_b = dest_ty.intInfo(zcu);
-
-    if (info_b.bits <= 32) {
-        if (info_a.bits > 32) {
-            return self.fail("TODO load least significant word into register", .{});
-        }
-
-        var operand_reg: Register = undefined;
-        var dest_reg: Register = undefined;
-
-        const read_args = [_]ReadArg{
-            .{ .ty = operand_ty, .bind = operand_bind, .class = gp, .reg = &operand_reg },
-        };
-        const write_args = [_]WriteArg{
-            .{ .ty = dest_ty, .bind = .none, .class = gp, .reg = &dest_reg },
-        };
-        try self.allocRegs(
-            &read_args,
-            &write_args,
-            if (maybe_inst) |inst| .{
-                .corresponding_inst = inst,
-                .operand_mapping = &.{0},
-            } else null,
-        );
-
-        switch (info_b.bits) {
-            32 => {
-                try self.genSetReg(operand_ty, dest_reg, .{ .register = operand_reg });
-            },
-            else => {
-                try self.truncRegister(operand_reg, dest_reg, info_b.signedness, info_b.bits);
-            },
-        }
-
-        return MCValue{ .register = dest_reg };
-    } else {
-        return self.fail("TODO: truncate to ints > 32 bits", .{});
-    }
-}
-
-fn airTrunc(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const operand_bind: ReadArg.Bind = .{ .inst = ty_op.operand };
-    const operand_ty = self.typeOf(ty_op.operand);
-    const dest_ty = self.typeOfIndex(inst);
-
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else blk: {
-        break :blk try self.trunc(inst, operand_bind, operand_ty, dest_ty);
-    };
-
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airNot(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const operand_bind: ReadArg.Bind = .{ .inst = ty_op.operand };
-        const operand_ty = self.typeOf(ty_op.operand);
-        switch (try operand_bind.resolveToMcv(self)) {
-            .dead => unreachable,
-            .unreach => unreachable,
-            .cpsr_flags => |cond| break :result MCValue{ .cpsr_flags = cond.negate() },
-            else => {
-                switch (operand_ty.zigTypeTag(zcu)) {
-                    .bool => {
-                        var op_reg: Register = undefined;
-                        var dest_reg: Register = undefined;
-
-                        const read_args = [_]ReadArg{
-                            .{ .ty = operand_ty, .bind = operand_bind, .class = gp, .reg = &op_reg },
-                        };
-                        const write_args = [_]WriteArg{
-                            .{ .ty = operand_ty, .bind = .none, .class = gp, .reg = &dest_reg },
-                        };
-                        try self.allocRegs(
-                            &read_args,
-                            &write_args,
-                            ReuseMetadata{
-                                .corresponding_inst = inst,
-                                .operand_mapping = &.{0},
-                            },
-                        );
-
-                        _ = try self.addInst(.{
-                            .tag = .eor,
-                            .data = .{ .rr_op = .{
-                                .rd = dest_reg,
-                                .rn = op_reg,
-                                .op = Instruction.Operand.fromU32(1).?,
-                            } },
-                        });
-
-                        break :result MCValue{ .register = dest_reg };
-                    },
-                    .vector => return self.fail("TODO bitwise not for vectors", .{}),
-                    .int => {
-                        const int_info = operand_ty.intInfo(zcu);
-                        if (int_info.bits <= 32) {
-                            var op_reg: Register = undefined;
-                            var dest_reg: Register = undefined;
-
-                            const read_args = [_]ReadArg{
-                                .{ .ty = operand_ty, .bind = operand_bind, .class = gp, .reg = &op_reg },
-                            };
-                            const write_args = [_]WriteArg{
-                                .{ .ty = operand_ty, .bind = .none, .class = gp, .reg = &dest_reg },
-                            };
-                            try self.allocRegs(
-                                &read_args,
-                                &write_args,
-                                ReuseMetadata{
-                                    .corresponding_inst = inst,
-                                    .operand_mapping = &.{0},
-                                },
-                            );
-
-                            _ = try self.addInst(.{
-                                .tag = .mvn,
-                                .data = .{ .r_op_mov = .{
-                                    .rd = dest_reg,
-                                    .op = Instruction.Operand.reg(op_reg, Instruction.Operand.Shift.none),
-                                } },
-                            });
-
-                            if (int_info.bits < 32) {
-                                try self.truncRegister(dest_reg, dest_reg, int_info.signedness, int_info.bits);
-                            }
-
-                            break :result MCValue{ .register = dest_reg };
-                        } else {
-                            return self.fail("TODO ARM not on integers > u32/i32", .{});
-                        }
-                    },
-                    else => unreachable,
-                }
-            },
-        }
-    };
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn minMax(
-    self: *Self,
-    tag: Air.Inst.Tag,
-    lhs_bind: ReadArg.Bind,
-    rhs_bind: ReadArg.Bind,
-    lhs_ty: Type,
-    rhs_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) !MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    switch (lhs_ty.zigTypeTag(zcu)) {
-        .float => return self.fail("TODO ARM min/max on floats", .{}),
-        .vector => return self.fail("TODO ARM min/max on vectors", .{}),
-        .int => {
-            assert(lhs_ty.eql(rhs_ty, zcu));
-            const int_info = lhs_ty.intInfo(zcu);
-            if (int_info.bits <= 32) {
-                var lhs_reg: Register = undefined;
-                var rhs_reg: Register = undefined;
-                var dest_reg: Register = undefined;
-
-                const read_args = [_]ReadArg{
-                    .{ .ty = lhs_ty, .bind = lhs_bind, .class = gp, .reg = &lhs_reg },
-                    .{ .ty = rhs_ty, .bind = rhs_bind, .class = gp, .reg = &rhs_reg },
-                };
-                const write_args = [_]WriteArg{
-                    .{ .ty = lhs_ty, .bind = .none, .class = gp, .reg = &dest_reg },
-                };
-                try self.allocRegs(
-                    &read_args,
-                    &write_args,
-                    if (maybe_inst) |inst| .{
-                        .corresponding_inst = inst,
-                        .operand_mapping = &.{ 0, 1 },
-                    } else null,
-                );
-
-                // lhs == reg should have been checked by airMinMax
-                //
-                // By guaranteeing lhs != rhs, we guarantee (dst !=
-                // lhs) or (dst != rhs), which is a property we use to
-                // omit generating one instruction when we reuse a
-                // register.
-                assert(lhs_reg != rhs_reg); // see note above
-
-                _ = try self.addInst(.{
-                    .tag = .cmp,
-                    .data = .{ .r_op_cmp = .{
-                        .rn = lhs_reg,
-                        .op = Instruction.Operand.reg(rhs_reg, Instruction.Operand.Shift.none),
-                    } },
-                });
-
-                const cond_choose_lhs: Condition = switch (tag) {
-                    .max => switch (int_info.signedness) {
-                        .signed => Condition.gt,
-                        .unsigned => Condition.hi,
-                    },
-                    .min => switch (int_info.signedness) {
-                        .signed => Condition.lt,
-                        .unsigned => Condition.cc,
-                    },
-                    else => unreachable,
-                };
-                const cond_choose_rhs = cond_choose_lhs.negate();
-
-                if (dest_reg != lhs_reg) {
-                    _ = try self.addInst(.{
-                        .tag = .mov,
-                        .cond = cond_choose_lhs,
-                        .data = .{ .r_op_mov = .{
-                            .rd = dest_reg,
-                            .op = Instruction.Operand.reg(lhs_reg, Instruction.Operand.Shift.none),
-                        } },
-                    });
-                }
-                if (dest_reg != rhs_reg) {
-                    _ = try self.addInst(.{
-                        .tag = .mov,
-                        .cond = cond_choose_rhs,
-                        .data = .{ .r_op_mov = .{
-                            .rd = dest_reg,
-                            .op = Instruction.Operand.reg(rhs_reg, Instruction.Operand.Shift.none),
-                        } },
-                    });
-                }
-
-                return MCValue{ .register = dest_reg };
-            } else {
-                return self.fail("TODO ARM min/max on integers > u32/i32", .{});
-            }
-        },
-        else => unreachable,
-    }
-}
-
-fn airMinMax(self: *Self, inst: Air.Inst.Index) !void {
-    const tag = self.air.instructions.items(.tag)[@intFromEnum(inst)];
-    const bin_op = self.air.instructions.items(.data)[@intFromEnum(inst)].bin_op;
-    const lhs_ty = self.typeOf(bin_op.lhs);
-    const rhs_ty = self.typeOf(bin_op.rhs);
-
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const lhs_bind: ReadArg.Bind = .{ .inst = bin_op.lhs };
-        const rhs_bind: ReadArg.Bind = .{ .inst = bin_op.rhs };
-
-        const lhs = try self.resolveInst(bin_op.lhs);
-        if (bin_op.lhs == bin_op.rhs) break :result lhs;
-
-        break :result try self.minMax(tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst);
-    };
-    return self.finishAir(inst, result, .{ bin_op.lhs, bin_op.rhs, .none });
-}
-
-fn airSlice(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_pl = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_pl;
-    const bin_op = self.air.extraData(Air.Bin, ty_pl.payload).data;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const ptr = try self.resolveInst(bin_op.lhs);
-        const ptr_ty = self.typeOf(bin_op.lhs);
-        const len = try self.resolveInst(bin_op.rhs);
-        const len_ty = self.typeOf(bin_op.rhs);
-
-        const stack_offset = try self.allocMem(8, .@"4", inst);
-        try self.genSetStack(ptr_ty, stack_offset, ptr);
-        try self.genSetStack(len_ty, stack_offset - 4, len);
-        break :result MCValue{ .stack_offset = stack_offset };
-    };
-    return self.finishAir(inst, result, .{ bin_op.lhs, bin_op.rhs, .none });
-}
-
-fn airBinOp(self: *Self, inst: Air.Inst.Index, tag: Air.Inst.Tag) !void {
-    const bin_op = self.air.instructions.items(.data)[@intFromEnum(inst)].bin_op;
-    const lhs_ty = self.typeOf(bin_op.lhs);
-    const rhs_ty = self.typeOf(bin_op.rhs);
-
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const lhs_bind: ReadArg.Bind = .{ .inst = bin_op.lhs };
-        const rhs_bind: ReadArg.Bind = .{ .inst = bin_op.rhs };
-
-        break :result switch (tag) {
-            .add => try self.addSub(tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-            .sub => try self.addSub(tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-
-            .mul => try self.mul(lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-
-            .div_float => try self.divFloat(lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-
-            .div_trunc => try self.divTrunc(lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-
-            .div_floor => try self.divFloor(lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-
-            .div_exact => try self.divExact(lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-
-            .rem => try self.rem(lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-
-            .mod => try self.modulo(lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-
-            .add_wrap => try self.wrappingArithmetic(tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-            .sub_wrap => try self.wrappingArithmetic(tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-            .mul_wrap => try self.wrappingArithmetic(tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-
-            .bit_and => try self.bitwise(tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-            .bit_or => try self.bitwise(tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-            .xor => try self.bitwise(tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-
-            .shl_exact => try self.shiftExact(tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-            .shr_exact => try self.shiftExact(tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-
-            .shl => try self.shiftNormal(tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-            .shr => try self.shiftNormal(tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-
-            .bool_and => try self.booleanOp(tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-            .bool_or => try self.booleanOp(tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst),
-
-            else => unreachable,
-        };
-    };
-    return self.finishAir(inst, result, .{ bin_op.lhs, bin_op.rhs, .none });
-}
-
-fn airPtrArithmetic(self: *Self, inst: Air.Inst.Index, tag: Air.Inst.Tag) !void {
-    const ty_pl = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_pl;
-    const bin_op = self.air.extraData(Air.Bin, ty_pl.payload).data;
-    const lhs_ty = self.typeOf(bin_op.lhs);
-    const rhs_ty = self.typeOf(bin_op.rhs);
-
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const lhs_bind: ReadArg.Bind = .{ .inst = bin_op.lhs };
-        const rhs_bind: ReadArg.Bind = .{ .inst = bin_op.rhs };
-
-        break :result try self.ptrArithmetic(tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, inst);
-    };
-    return self.finishAir(inst, result, .{ bin_op.lhs, bin_op.rhs, .none });
-}
-
-fn airAddSat(self: *Self, inst: Air.Inst.Index) !void {
-    const bin_op = self.air.instructions.items(.data)[@intFromEnum(inst)].bin_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement add_sat for {}", .{self.target.cpu.arch});
-    return self.finishAir(inst, result, .{ bin_op.lhs, bin_op.rhs, .none });
-}
-
-fn airSubSat(self: *Self, inst: Air.Inst.Index) !void {
-    const bin_op = self.air.instructions.items(.data)[@intFromEnum(inst)].bin_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement sub_sat for {}", .{self.target.cpu.arch});
-    return self.finishAir(inst, result, .{ bin_op.lhs, bin_op.rhs, .none });
-}
-
-fn airMulSat(self: *Self, inst: Air.Inst.Index) !void {
-    const bin_op = self.air.instructions.items(.data)[@intFromEnum(inst)].bin_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement mul_sat for {}", .{self.target.cpu.arch});
-    return self.finishAir(inst, result, .{ bin_op.lhs, bin_op.rhs, .none });
-}
-
-fn airOverflow(self: *Self, inst: Air.Inst.Index) !void {
-    const tag = self.air.instructions.items(.tag)[@intFromEnum(inst)];
-    const ty_pl = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_pl;
-    const extra = self.air.extraData(Air.Bin, ty_pl.payload).data;
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const lhs_bind: ReadArg.Bind = .{ .inst = extra.lhs };
-        const rhs_bind: ReadArg.Bind = .{ .inst = extra.rhs };
-        const lhs_ty = self.typeOf(extra.lhs);
-        const rhs_ty = self.typeOf(extra.rhs);
-
-        const tuple_ty = self.typeOfIndex(inst);
-        const tuple_size: u32 = @intCast(tuple_ty.abiSize(zcu));
-        const tuple_align = tuple_ty.abiAlignment(zcu);
-        const overflow_bit_offset: u32 = @intCast(tuple_ty.structFieldOffset(1, zcu));
-
-        switch (lhs_ty.zigTypeTag(zcu)) {
-            .vector => return self.fail("TODO implement add_with_overflow/sub_with_overflow for vectors", .{}),
-            .int => {
-                assert(lhs_ty.eql(rhs_ty, zcu));
-                const int_info = lhs_ty.intInfo(zcu);
-                if (int_info.bits < 32) {
-                    const stack_offset = try self.allocMem(tuple_size, tuple_align, inst);
-
-                    try self.spillCompareFlagsIfOccupied();
-
-                    const base_tag: Air.Inst.Tag = switch (tag) {
-                        .add_with_overflow => .add,
-                        .sub_with_overflow => .sub,
-                        else => unreachable,
-                    };
-                    const dest = try self.addSub(base_tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, null);
-                    const dest_reg = dest.register;
-                    const dest_reg_lock = self.register_manager.lockRegAssumeUnused(dest_reg);
-                    defer self.register_manager.unlockReg(dest_reg_lock);
-
-                    const truncated_reg = try self.register_manager.allocReg(null, gp);
-                    const truncated_reg_lock = self.register_manager.lockRegAssumeUnused(truncated_reg);
-                    defer self.register_manager.unlockReg(truncated_reg_lock);
-
-                    // sbfx/ubfx truncated, dest, #0, #bits
-                    try self.truncRegister(dest_reg, truncated_reg, int_info.signedness, int_info.bits);
-
-                    // cmp dest, truncated
-                    _ = try self.addInst(.{
-                        .tag = .cmp,
-                        .data = .{ .r_op_cmp = .{
-                            .rn = dest_reg,
-                            .op = Instruction.Operand.reg(truncated_reg, Instruction.Operand.Shift.none),
-                        } },
-                    });
-
-                    try self.genSetStack(lhs_ty, stack_offset, .{ .register = truncated_reg });
-                    try self.genSetStack(Type.u1, stack_offset - overflow_bit_offset, .{ .cpsr_flags = .ne });
-
-                    break :result MCValue{ .stack_offset = stack_offset };
-                } else if (int_info.bits == 32) {
-                    const lhs_immediate = try lhs_bind.resolveToImmediate(self);
-                    const rhs_immediate = try rhs_bind.resolveToImmediate(self);
-
-                    // Only say yes if the operation is
-                    // commutative, i.e. we can swap both of the
-                    // operands
-                    const lhs_immediate_ok = switch (tag) {
-                        .add_with_overflow => if (lhs_immediate) |imm| Instruction.Operand.fromU32(imm) != null else false,
-                        .sub_with_overflow => false,
-                        else => unreachable,
-                    };
-                    const rhs_immediate_ok = switch (tag) {
-                        .add_with_overflow,
-                        .sub_with_overflow,
-                        => if (rhs_immediate) |imm| Instruction.Operand.fromU32(imm) != null else false,
-                        else => unreachable,
-                    };
-
-                    const mir_tag: Mir.Inst.Tag = switch (tag) {
-                        .add_with_overflow => .adds,
-                        .sub_with_overflow => .subs,
-                        else => unreachable,
-                    };
-
-                    try self.spillCompareFlagsIfOccupied();
-                    self.cpsr_flags_inst = inst;
-
-                    const dest = blk: {
-                        if (rhs_immediate_ok) {
-                            break :blk try self.binOpImmediate(mir_tag, lhs_bind, rhs_immediate.?, lhs_ty, false, null);
-                        } else if (lhs_immediate_ok) {
-                            // swap lhs and rhs
-                            break :blk try self.binOpImmediate(mir_tag, rhs_bind, lhs_immediate.?, rhs_ty, true, null);
-                        } else {
-                            break :blk try self.binOpRegister(mir_tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, null);
-                        }
-                    };
-
-                    if (tag == .sub_with_overflow) {
-                        break :result MCValue{ .register_v_flag = dest.register };
-                    }
-
-                    switch (int_info.signedness) {
-                        .unsigned => break :result MCValue{ .register_c_flag = dest.register },
-                        .signed => break :result MCValue{ .register_v_flag = dest.register },
-                    }
-                } else {
-                    return self.fail("TODO ARM overflow operations on integers > u32/i32", .{});
-                }
-            },
-            else => unreachable,
-        }
-    };
-    return self.finishAir(inst, result, .{ extra.lhs, extra.rhs, .none });
-}
-
-fn airMulWithOverflow(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_pl = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_pl;
-    const extra = self.air.extraData(Air.Bin, ty_pl.payload).data;
-    if (self.liveness.isUnused(inst)) return self.finishAir(inst, .dead, .{ extra.lhs, extra.rhs, .none });
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const result: MCValue = result: {
-        const lhs_bind: ReadArg.Bind = .{ .inst = extra.lhs };
-        const rhs_bind: ReadArg.Bind = .{ .inst = extra.rhs };
-        const lhs_ty = self.typeOf(extra.lhs);
-        const rhs_ty = self.typeOf(extra.rhs);
-
-        const tuple_ty = self.typeOfIndex(inst);
-        const tuple_size: u32 = @intCast(tuple_ty.abiSize(zcu));
-        const tuple_align = tuple_ty.abiAlignment(zcu);
-        const overflow_bit_offset: u32 = @intCast(tuple_ty.structFieldOffset(1, zcu));
-
-        switch (lhs_ty.zigTypeTag(zcu)) {
-            .vector => return self.fail("TODO implement mul_with_overflow for vectors", .{}),
-            .int => {
-                assert(lhs_ty.eql(rhs_ty, zcu));
-                const int_info = lhs_ty.intInfo(zcu);
-                if (int_info.bits <= 16) {
-                    const stack_offset = try self.allocMem(tuple_size, tuple_align, inst);
-
-                    try self.spillCompareFlagsIfOccupied();
-
-                    const base_tag: Mir.Inst.Tag = switch (int_info.signedness) {
-                        .signed => .smulbb,
-                        .unsigned => .mul,
-                    };
-
-                    const dest = try self.binOpRegister(base_tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, null);
-                    const dest_reg = dest.register;
-                    const dest_reg_lock = self.register_manager.lockRegAssumeUnused(dest_reg);
-                    defer self.register_manager.unlockReg(dest_reg_lock);
-
-                    const truncated_reg = try self.register_manager.allocReg(null, gp);
-                    const truncated_reg_lock = self.register_manager.lockRegAssumeUnused(truncated_reg);
-                    defer self.register_manager.unlockReg(truncated_reg_lock);
-
-                    // sbfx/ubfx truncated, dest, #0, #bits
-                    try self.truncRegister(dest_reg, truncated_reg, int_info.signedness, int_info.bits);
-
-                    // cmp dest, truncated
-                    _ = try self.addInst(.{
-                        .tag = .cmp,
-                        .data = .{ .r_op_cmp = .{
-                            .rn = dest_reg,
-                            .op = Instruction.Operand.reg(truncated_reg, Instruction.Operand.Shift.none),
-                        } },
-                    });
-
-                    try self.genSetStack(lhs_ty, stack_offset, .{ .register = truncated_reg });
-                    try self.genSetStack(Type.u1, stack_offset - overflow_bit_offset, .{ .cpsr_flags = .ne });
-
-                    break :result MCValue{ .stack_offset = stack_offset };
-                } else if (int_info.bits <= 32) {
-                    const stack_offset = try self.allocMem(tuple_size, tuple_align, inst);
-
-                    try self.spillCompareFlagsIfOccupied();
-
-                    const base_tag: Mir.Inst.Tag = switch (int_info.signedness) {
-                        .signed => .smull,
-                        .unsigned => .umull,
-                    };
-
-                    var lhs_reg: Register = undefined;
-                    var rhs_reg: Register = undefined;
-                    var rdhi: Register = undefined;
-                    var rdlo: Register = undefined;
-                    var truncated_reg: Register = undefined;
-
-                    const read_args = [_]ReadArg{
-                        .{ .ty = lhs_ty, .bind = lhs_bind, .class = gp, .reg = &lhs_reg },
-                        .{ .ty = rhs_ty, .bind = rhs_bind, .class = gp, .reg = &rhs_reg },
-                    };
-                    const write_args = [_]WriteArg{
-                        .{ .ty = lhs_ty, .bind = .none, .class = gp, .reg = &rdhi },
-                        .{ .ty = lhs_ty, .bind = .none, .class = gp, .reg = &rdlo },
-                        .{ .ty = lhs_ty, .bind = .none, .class = gp, .reg = &truncated_reg },
-                    };
-                    try self.allocRegs(
-                        &read_args,
-                        &write_args,
-                        null,
-                    );
-
-                    _ = try self.addInst(.{
-                        .tag = base_tag,
-                        .data = .{ .rrrr = .{
-                            .rdlo = rdlo,
-                            .rdhi = rdhi,
-                            .rn = lhs_reg,
-                            .rm = rhs_reg,
-                        } },
-                    });
-
-                    // sbfx/ubfx truncated, rdlo, #0, #bits
-                    try self.truncRegister(rdlo, truncated_reg, int_info.signedness, int_info.bits);
-
-                    // str truncated, [...]
-                    try self.genSetStack(lhs_ty, stack_offset, .{ .register = truncated_reg });
-
-                    // cmp truncated, rdlo
-                    _ = try self.addInst(.{
-                        .tag = .cmp,
-                        .data = .{ .r_op_cmp = .{
-                            .rn = truncated_reg,
-                            .op = Instruction.Operand.reg(rdlo, Instruction.Operand.Shift.none),
-                        } },
-                    });
-
-                    // mov rdlo, #0
-                    _ = try self.addInst(.{
-                        .tag = .mov,
-                        .data = .{ .r_op_mov = .{
-                            .rd = rdlo,
-                            .op = Instruction.Operand.fromU32(0).?,
-                        } },
-                    });
-
-                    // movne rdlo, #1
-                    _ = try self.addInst(.{
-                        .tag = .mov,
-                        .cond = .ne,
-                        .data = .{ .r_op_mov = .{
-                            .rd = rdlo,
-                            .op = Instruction.Operand.fromU32(1).?,
-                        } },
-                    });
-
-                    // cmp rdhi, #0
-                    _ = try self.addInst(.{
-                        .tag = .cmp,
-                        .data = .{ .r_op_cmp = .{
-                            .rn = rdhi,
-                            .op = Instruction.Operand.fromU32(0).?,
-                        } },
-                    });
-
-                    // movne rdlo, #1
-                    _ = try self.addInst(.{
-                        .tag = .mov,
-                        .cond = .ne,
-                        .data = .{ .r_op_mov = .{
-                            .rd = rdlo,
-                            .op = Instruction.Operand.fromU32(1).?,
-                        } },
-                    });
-
-                    // strb rdlo, [...]
-                    try self.genSetStack(Type.u1, stack_offset - overflow_bit_offset, .{ .register = rdlo });
-
-                    break :result MCValue{ .stack_offset = stack_offset };
-                } else {
-                    return self.fail("TODO ARM overflow operations on integers > u32/i32", .{});
-                }
-            },
-            else => unreachable,
-        }
-    };
-    return self.finishAir(inst, result, .{ extra.lhs, extra.rhs, .none });
-}
-
-fn airShlWithOverflow(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_pl = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_pl;
-    const extra = self.air.extraData(Air.Bin, ty_pl.payload).data;
-    if (self.liveness.isUnused(inst)) return self.finishAir(inst, .dead, .{ extra.lhs, extra.rhs, .none });
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const result: MCValue = result: {
-        const lhs_ty = self.typeOf(extra.lhs);
-        const rhs_ty = self.typeOf(extra.rhs);
-
-        const tuple_ty = self.typeOfIndex(inst);
-        const tuple_size: u32 = @intCast(tuple_ty.abiSize(zcu));
-        const tuple_align = tuple_ty.abiAlignment(zcu);
-        const overflow_bit_offset: u32 = @intCast(tuple_ty.structFieldOffset(1, zcu));
-
-        switch (lhs_ty.zigTypeTag(zcu)) {
-            .vector => if (!rhs_ty.isVector(zcu))
-                return self.fail("TODO implement vector shl_with_overflow with scalar rhs", .{})
-            else
-                return self.fail("TODO implement shl_with_overflow for vectors", .{}),
-            .int => {
-                const int_info = lhs_ty.intInfo(zcu);
-                if (int_info.bits <= 32) {
-                    const stack_offset = try self.allocMem(tuple_size, tuple_align, inst);
-
-                    try self.spillCompareFlagsIfOccupied();
-
-                    const shr_mir_tag: Mir.Inst.Tag = switch (int_info.signedness) {
-                        .signed => Mir.Inst.Tag.asr,
-                        .unsigned => Mir.Inst.Tag.lsr,
-                    };
-
-                    var lhs_reg: Register = undefined;
-                    var rhs_reg: Register = undefined;
-                    var dest_reg: Register = undefined;
-                    var reconstructed_reg: Register = undefined;
-
-                    const rhs_mcv = try self.resolveInst(extra.rhs);
-                    const rhs_immediate_ok = rhs_mcv == .immediate and Instruction.Operand.fromU32(rhs_mcv.immediate) != null;
-
-                    const lhs_bind: ReadArg.Bind = .{ .inst = extra.lhs };
-                    const rhs_bind: ReadArg.Bind = .{ .inst = extra.rhs };
-
-                    if (rhs_immediate_ok) {
-                        const read_args = [_]ReadArg{
-                            .{ .ty = lhs_ty, .bind = lhs_bind, .class = gp, .reg = &lhs_reg },
-                        };
-                        const write_args = [_]WriteArg{
-                            .{ .ty = lhs_ty, .bind = .none, .class = gp, .reg = &dest_reg },
-                            .{ .ty = lhs_ty, .bind = .none, .class = gp, .reg = &reconstructed_reg },
-                        };
-                        try self.allocRegs(
-                            &read_args,
-                            &write_args,
-                            null,
-                        );
-
-                        // lsl dest, lhs, rhs
-                        _ = try self.addInst(.{
-                            .tag = .lsl,
-                            .data = .{ .rr_shift = .{
-                                .rd = dest_reg,
-                                .rm = lhs_reg,
-                                .shift_amount = Instruction.ShiftAmount.imm(@intCast(rhs_mcv.immediate)),
-                            } },
-                        });
-
-                        try self.truncRegister(dest_reg, dest_reg, int_info.signedness, int_info.bits);
-
-                        // asr/lsr reconstructed, dest, rhs
-                        _ = try self.addInst(.{
-                            .tag = shr_mir_tag,
-                            .data = .{ .rr_shift = .{
-                                .rd = reconstructed_reg,
-                                .rm = dest_reg,
-                                .shift_amount = Instruction.ShiftAmount.imm(@intCast(rhs_mcv.immediate)),
-                            } },
-                        });
-                    } else {
-                        const read_args = [_]ReadArg{
-                            .{ .ty = lhs_ty, .bind = lhs_bind, .class = gp, .reg = &lhs_reg },
-                            .{ .ty = rhs_ty, .bind = rhs_bind, .class = gp, .reg = &rhs_reg },
-                        };
-                        const write_args = [_]WriteArg{
-                            .{ .ty = lhs_ty, .bind = .none, .class = gp, .reg = &dest_reg },
-                            .{ .ty = lhs_ty, .bind = .none, .class = gp, .reg = &reconstructed_reg },
-                        };
-                        try self.allocRegs(
-                            &read_args,
-                            &write_args,
-                            null,
-                        );
-
-                        // lsl dest, lhs, rhs
-                        _ = try self.addInst(.{
-                            .tag = .lsl,
-                            .data = .{ .rr_shift = .{
-                                .rd = dest_reg,
-                                .rm = lhs_reg,
-                                .shift_amount = Instruction.ShiftAmount.reg(rhs_reg),
-                            } },
-                        });
-
-                        try self.truncRegister(dest_reg, dest_reg, int_info.signedness, int_info.bits);
-
-                        // asr/lsr reconstructed, dest, rhs
-                        _ = try self.addInst(.{
-                            .tag = shr_mir_tag,
-                            .data = .{ .rr_shift = .{
-                                .rd = reconstructed_reg,
-                                .rm = dest_reg,
-                                .shift_amount = Instruction.ShiftAmount.reg(rhs_reg),
-                            } },
-                        });
-                    }
-
-                    // cmp lhs, reconstructed
-                    _ = try self.addInst(.{
-                        .tag = .cmp,
-                        .data = .{ .r_op_cmp = .{
-                            .rn = lhs_reg,
-                            .op = Instruction.Operand.reg(reconstructed_reg, Instruction.Operand.Shift.none),
-                        } },
-                    });
-
-                    try self.genSetStack(lhs_ty, stack_offset, .{ .register = dest_reg });
-                    try self.genSetStack(Type.u1, stack_offset - overflow_bit_offset, .{ .cpsr_flags = .ne });
-
-                    break :result MCValue{ .stack_offset = stack_offset };
-                } else {
-                    return self.fail("TODO ARM overflow operations on integers > u32/i32", .{});
-                }
-            },
-            else => unreachable,
-        }
-    };
-    return self.finishAir(inst, result, .{ extra.lhs, extra.rhs, .none });
-}
-
-fn airShlSat(self: *Self, inst: Air.Inst.Index) !void {
-    const zcu = self.pt.zcu;
-    const bin_op = self.air.instructions.items(.data)[@intFromEnum(inst)].bin_op;
-    const result: MCValue = if (self.liveness.isUnused(inst))
-        .dead
-    else if (self.typeOf(bin_op.lhs).isVector(zcu) and !self.typeOf(bin_op.rhs).isVector(zcu))
-        return self.fail("TODO implement vector shl_sat with scalar rhs for {}", .{self.target.cpu.arch})
-    else
-        return self.fail("TODO implement shl_sat for {}", .{self.target.cpu.arch});
-    return self.finishAir(inst, result, .{ bin_op.lhs, bin_op.rhs, .none });
-}
-
-fn airOptionalPayload(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement .optional_payload for {}", .{self.target.cpu.arch});
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airOptionalPayloadPtr(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement .optional_payload_ptr for {}", .{self.target.cpu.arch});
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airOptionalPayloadPtrSet(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement .optional_payload_ptr_set for {}", .{self.target.cpu.arch});
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airWrapOptional(self: *Self, inst: Air.Inst.Index) !void {
-    const pt = self.pt;
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const optional_ty = self.typeOfIndex(inst);
-        const abi_size: u32 = @intCast(optional_ty.abiSize(pt.zcu));
-
-        // Optional with a zero-bit payload type is just a boolean true
-        if (abi_size == 1) {
-            break :result MCValue{ .immediate = 1 };
-        } else {
-            return self.fail("TODO implement wrap optional for {}", .{self.target.cpu.arch});
-        }
-    };
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-/// Given an error union, returns the error
-fn errUnionErr(
-    self: *Self,
-    error_union_bind: ReadArg.Bind,
-    error_union_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) !MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const err_ty = error_union_ty.errorUnionSet(zcu);
-    const payload_ty = error_union_ty.errorUnionPayload(zcu);
-    if (err_ty.errorSetIsEmpty(zcu)) {
-        return MCValue{ .immediate = 0 };
-    }
-    if (!payload_ty.hasRuntimeBitsIgnoreComptime(zcu)) {
-        return try error_union_bind.resolveToMcv(self);
-    }
-
-    const err_offset: u32 = @intCast(errUnionErrorOffset(payload_ty, zcu));
-    switch (try error_union_bind.resolveToMcv(self)) {
-        .register => {
-            var operand_reg: Register = undefined;
-            var dest_reg: Register = undefined;
-
-            const read_args = [_]ReadArg{
-                .{ .ty = error_union_ty, .bind = error_union_bind, .class = gp, .reg = &operand_reg },
-            };
-            const write_args = [_]WriteArg{
-                .{ .ty = err_ty, .bind = .none, .class = gp, .reg = &dest_reg },
-            };
-            try self.allocRegs(
-                &read_args,
-                &write_args,
-                if (maybe_inst) |inst| .{
-                    .corresponding_inst = inst,
-                    .operand_mapping = &.{0},
-                } else null,
-            );
-
-            const err_bit_offset = err_offset * 8;
-            const err_bit_size: u32 = @intCast(err_ty.abiSize(zcu) * 8);
-
-            _ = try self.addInst(.{
-                .tag = .ubfx, // errors are unsigned integers
-                .data = .{ .rr_lsb_width = .{
-                    .rd = dest_reg,
-                    .rn = operand_reg,
-                    .lsb = @intCast(err_bit_offset),
-                    .width = @intCast(err_bit_size),
-                } },
-            });
-
-            return MCValue{ .register = dest_reg };
-        },
-        .stack_argument_offset => |off| {
-            return MCValue{ .stack_argument_offset = off + err_offset };
-        },
-        .stack_offset => |off| {
-            return MCValue{ .stack_offset = off - err_offset };
-        },
-        .memory => |addr| {
-            return MCValue{ .memory = addr + err_offset };
-        },
-        else => unreachable, // invalid MCValue for an error union
-    }
-}
-
-fn airUnwrapErrErr(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const error_union_bind: ReadArg.Bind = .{ .inst = ty_op.operand };
-        const error_union_ty = self.typeOf(ty_op.operand);
-
-        break :result try self.errUnionErr(error_union_bind, error_union_ty, inst);
-    };
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-/// Given an error union, returns the payload
-fn errUnionPayload(
-    self: *Self,
-    error_union_bind: ReadArg.Bind,
-    error_union_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) !MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const err_ty = error_union_ty.errorUnionSet(zcu);
-    const payload_ty = error_union_ty.errorUnionPayload(zcu);
-    if (err_ty.errorSetIsEmpty(zcu)) {
-        return try error_union_bind.resolveToMcv(self);
-    }
-    if (!payload_ty.hasRuntimeBitsIgnoreComptime(zcu)) {
-        return MCValue.none;
-    }
-
-    const payload_offset: u32 = @intCast(errUnionPayloadOffset(payload_ty, zcu));
-    switch (try error_union_bind.resolveToMcv(self)) {
-        .register => {
-            var operand_reg: Register = undefined;
-            var dest_reg: Register = undefined;
-
-            const read_args = [_]ReadArg{
-                .{ .ty = error_union_ty, .bind = error_union_bind, .class = gp, .reg = &operand_reg },
-            };
-            const write_args = [_]WriteArg{
-                .{ .ty = err_ty, .bind = .none, .class = gp, .reg = &dest_reg },
-            };
-            try self.allocRegs(
-                &read_args,
-                &write_args,
-                if (maybe_inst) |inst| .{
-                    .corresponding_inst = inst,
-                    .operand_mapping = &.{0},
-                } else null,
-            );
-
-            const payload_bit_offset = payload_offset * 8;
-            const payload_bit_size: u32 = @intCast(payload_ty.abiSize(zcu) * 8);
-
-            _ = try self.addInst(.{
-                .tag = if (payload_ty.isSignedInt(zcu)) Mir.Inst.Tag.sbfx else .ubfx,
-                .data = .{ .rr_lsb_width = .{
-                    .rd = dest_reg,
-                    .rn = operand_reg,
-                    .lsb = @intCast(payload_bit_offset),
-                    .width = @intCast(payload_bit_size),
-                } },
-            });
-
-            return MCValue{ .register = dest_reg };
-        },
-        .stack_argument_offset => |off| {
-            return MCValue{ .stack_argument_offset = off + payload_offset };
-        },
-        .stack_offset => |off| {
-            return MCValue{ .stack_offset = off - payload_offset };
-        },
-        .memory => |addr| {
-            return MCValue{ .memory = addr + payload_offset };
-        },
-        else => unreachable, // invalid MCValue for an error union
-    }
-}
-
-fn airUnwrapErrPayload(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const error_union_bind: ReadArg.Bind = .{ .inst = ty_op.operand };
-        const error_union_ty = self.typeOf(ty_op.operand);
-
-        break :result try self.errUnionPayload(error_union_bind, error_union_ty, inst);
-    };
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-// *(E!T) -> E
-fn airUnwrapErrErrPtr(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement unwrap error union error ptr for {}", .{self.target.cpu.arch});
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-// *(E!T) -> *T
-fn airUnwrapErrPayloadPtr(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement unwrap error union payload ptr for {}", .{self.target.cpu.arch});
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airErrUnionPayloadPtrSet(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement .errunion_payload_ptr_set for {}", .{self.target.cpu.arch});
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airErrReturnTrace(self: *Self, inst: Air.Inst.Index) !void {
-    const result: MCValue = if (self.liveness.isUnused(inst))
-        .dead
-    else
-        return self.fail("TODO implement airErrReturnTrace for {}", .{self.target.cpu.arch});
-    return self.finishAir(inst, result, .{ .none, .none, .none });
-}
-
-fn airSetErrReturnTrace(self: *Self, inst: Air.Inst.Index) !void {
-    _ = inst;
-    return self.fail("TODO implement airSetErrReturnTrace for {}", .{self.target.cpu.arch});
-}
-
-fn airSaveErrReturnTraceIndex(self: *Self, inst: Air.Inst.Index) !void {
-    _ = inst;
-    return self.fail("TODO implement airSaveErrReturnTraceIndex for {}", .{self.target.cpu.arch});
-}
-
-/// T to E!T
-fn airWrapErrUnionPayload(self: *Self, inst: Air.Inst.Index) !void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const error_union_ty = ty_op.ty.toType();
-        const error_ty = error_union_ty.errorUnionSet(zcu);
-        const payload_ty = error_union_ty.errorUnionPayload(zcu);
-        const operand = try self.resolveInst(ty_op.operand);
-        if (!payload_ty.hasRuntimeBitsIgnoreComptime(zcu)) break :result operand;
-
-        const abi_size: u32 = @intCast(error_union_ty.abiSize(zcu));
-        const abi_align = error_union_ty.abiAlignment(zcu);
-        const stack_offset: u32 = @intCast(try self.allocMem(abi_size, abi_align, inst));
-        const payload_off = errUnionPayloadOffset(payload_ty, zcu);
-        const err_off = errUnionErrorOffset(payload_ty, zcu);
-        try self.genSetStack(payload_ty, stack_offset - @as(u32, @intCast(payload_off)), operand);
-        try self.genSetStack(error_ty, stack_offset - @as(u32, @intCast(err_off)), .{ .immediate = 0 });
-
-        break :result MCValue{ .stack_offset = stack_offset };
-    };
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-/// E to E!T
-fn airWrapErrUnionErr(self: *Self, inst: Air.Inst.Index) !void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const error_union_ty = ty_op.ty.toType();
-        const error_ty = error_union_ty.errorUnionSet(zcu);
-        const payload_ty = error_union_ty.errorUnionPayload(zcu);
-        const operand = try self.resolveInst(ty_op.operand);
-        if (!payload_ty.hasRuntimeBitsIgnoreComptime(zcu)) break :result operand;
-
-        const abi_size: u32 = @intCast(error_union_ty.abiSize(zcu));
-        const abi_align = error_union_ty.abiAlignment(zcu);
-        const stack_offset: u32 = @intCast(try self.allocMem(abi_size, abi_align, inst));
-        const payload_off = errUnionPayloadOffset(payload_ty, zcu);
-        const err_off = errUnionErrorOffset(payload_ty, zcu);
-        try self.genSetStack(error_ty, stack_offset - @as(u32, @intCast(err_off)), operand);
-        try self.genSetStack(payload_ty, stack_offset - @as(u32, @intCast(payload_off)), .undef);
-
-        break :result MCValue{ .stack_offset = stack_offset };
-    };
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-/// Given a slice, returns the length
-fn slicePtr(mcv: MCValue) MCValue {
-    switch (mcv) {
-        .register => unreachable, // a slice doesn't fit in one register
-        .stack_argument_offset => |off| {
-            return MCValue{ .stack_argument_offset = off };
-        },
-        .stack_offset => |off| {
-            return MCValue{ .stack_offset = off };
-        },
-        .memory => |addr| {
-            return MCValue{ .memory = addr };
-        },
-        else => unreachable, // invalid MCValue for a slice
-    }
-}
-
-fn airSlicePtr(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const mcv = try self.resolveInst(ty_op.operand);
-        break :result slicePtr(mcv);
-    };
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airSliceLen(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const mcv = try self.resolveInst(ty_op.operand);
-        switch (mcv) {
-            .register => unreachable, // a slice doesn't fit in one register
-            .stack_argument_offset => |off| {
-                break :result MCValue{ .stack_argument_offset = off + 4 };
-            },
-            .stack_offset => |off| {
-                break :result MCValue{ .stack_offset = off - 4 };
-            },
-            .memory => |addr| {
-                break :result MCValue{ .memory = addr + 4 };
-            },
-            else => unreachable, // invalid MCValue for a slice
-        }
-    };
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airPtrSliceLenPtr(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const mcv = try self.resolveInst(ty_op.operand);
-        switch (mcv) {
-            .dead, .unreach => unreachable,
-            .ptr_stack_offset => |off| {
-                break :result MCValue{ .ptr_stack_offset = off - 4 };
-            },
-            else => {
-                const lhs_bind: ReadArg.Bind = .{ .mcv = mcv };
-                const rhs_bind: ReadArg.Bind = .{ .mcv = .{ .immediate = 4 } };
-
-                break :result try self.addSub(.add, lhs_bind, rhs_bind, Type.usize, Type.usize, null);
-            },
-        }
-    };
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airPtrSlicePtrPtr(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const mcv = try self.resolveInst(ty_op.operand);
-        switch (mcv) {
-            .dead, .unreach => unreachable,
-            .ptr_stack_offset => |off| {
-                break :result MCValue{ .ptr_stack_offset = off };
-            },
-            else => {
-                if (self.reuseOperand(inst, ty_op.operand, 0, mcv)) {
-                    break :result mcv;
-                } else {
-                    break :result MCValue{ .register = try self.copyToTmpRegister(Type.usize, mcv) };
-                }
-            },
-        }
-    };
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn ptrElemVal(
-    self: *Self,
-    ptr_bind: ReadArg.Bind,
-    index_bind: ReadArg.Bind,
-    ptr_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) !MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const elem_ty = ptr_ty.childType(zcu);
-    const elem_size: u32 = @intCast(elem_ty.abiSize(zcu));
-
-    switch (elem_size) {
-        1, 4 => {
-            var base_reg: Register = undefined;
-            var index_reg: Register = undefined;
-            var dest_reg: Register = undefined;
-
-            const read_args = [_]ReadArg{
-                .{ .ty = ptr_ty, .bind = ptr_bind, .class = gp, .reg = &base_reg },
-                .{ .ty = Type.usize, .bind = index_bind, .class = gp, .reg = &index_reg },
-            };
-            const write_args = [_]WriteArg{
-                .{ .ty = elem_ty, .bind = .none, .class = gp, .reg = &dest_reg },
-            };
-            try self.allocRegs(
-                &read_args,
-                &write_args,
-                if (maybe_inst) |inst| .{
-                    .corresponding_inst = inst,
-                    .operand_mapping = &.{ 0, 1 },
-                } else null,
-            );
-
-            const tag: Mir.Inst.Tag = switch (elem_size) {
-                1 => .ldrb,
-                4 => .ldr,
-                else => unreachable,
-            };
-            const shift: u5 = switch (elem_size) {
-                1 => 0,
-                4 => 2,
-                else => unreachable,
-            };
-
-            _ = try self.addInst(.{
-                .tag = tag,
-                .data = .{ .rr_offset = .{
-                    .rt = dest_reg,
-                    .rn = base_reg,
-                    .offset = .{ .offset = Instruction.Offset.reg(index_reg, .{ .lsl = shift }) },
-                } },
-            });
-
-            return MCValue{ .register = dest_reg };
-        },
-        else => {
-            const addr = try self.ptrArithmetic(.ptr_add, ptr_bind, index_bind, ptr_ty, Type.usize, null);
-
-            const dest = try self.allocRegOrMem(elem_ty, true, maybe_inst);
-            try self.load(dest, addr, ptr_ty);
-            return dest;
-        },
-    }
-}
-
-fn airSliceElemVal(self: *Self, inst: Air.Inst.Index) !void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const bin_op = self.air.instructions.items(.data)[@intFromEnum(inst)].bin_op;
-    const slice_ty = self.typeOf(bin_op.lhs);
-    const result: MCValue = if (!slice_ty.isVolatilePtr(zcu) and self.liveness.isUnused(inst)) .dead else result: {
-        const ptr_ty = slice_ty.slicePtrFieldType(zcu);
-
-        const slice_mcv = try self.resolveInst(bin_op.lhs);
-        const base_mcv = slicePtr(slice_mcv);
-
-        const base_bind: ReadArg.Bind = .{ .mcv = base_mcv };
-        const index_bind: ReadArg.Bind = .{ .inst = bin_op.rhs };
-
-        break :result try self.ptrElemVal(base_bind, index_bind, ptr_ty, inst);
-    };
-    return self.finishAir(inst, result, .{ bin_op.lhs, bin_op.rhs, .none });
-}
-
-fn airSliceElemPtr(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_pl = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_pl;
-    const extra = self.air.extraData(Air.Bin, ty_pl.payload).data;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const slice_mcv = try self.resolveInst(extra.lhs);
-        const base_mcv = slicePtr(slice_mcv);
-
-        const base_bind: ReadArg.Bind = .{ .mcv = base_mcv };
-        const index_bind: ReadArg.Bind = .{ .inst = extra.rhs };
-
-        const slice_ty = self.typeOf(extra.lhs);
-        const index_ty = self.typeOf(extra.rhs);
-
-        const addr = try self.ptrArithmetic(.ptr_add, base_bind, index_bind, slice_ty, index_ty, null);
-        break :result addr;
-    };
-    return self.finishAir(inst, result, .{ extra.lhs, extra.rhs, .none });
-}
-
-fn arrayElemVal(
-    self: *Self,
-    array_bind: ReadArg.Bind,
-    index_bind: ReadArg.Bind,
-    array_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) InnerError!MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const elem_ty = array_ty.childType(zcu);
-
-    const mcv = try array_bind.resolveToMcv(self);
-    switch (mcv) {
-        .stack_offset,
-        .memory,
-        .stack_argument_offset,
-        => {
-            const ptr_to_mcv = switch (mcv) {
-                .stack_offset => |off| MCValue{ .ptr_stack_offset = off },
-                .memory => |addr| MCValue{ .immediate = @intCast(addr) },
-                .stack_argument_offset => |off| blk: {
-                    const reg = try self.register_manager.allocReg(null, gp);
-
-                    _ = try self.addInst(.{
-                        .tag = .ldr_ptr_stack_argument,
-                        .data = .{ .r_stack_offset = .{
-                            .rt = reg,
-                            .stack_offset = off,
-                        } },
-                    });
-
-                    break :blk MCValue{ .register = reg };
-                },
-                else => unreachable,
-            };
-            const ptr_to_mcv_lock: ?RegisterLock = switch (ptr_to_mcv) {
-                .register => |reg| self.register_manager.lockRegAssumeUnused(reg),
-                else => null,
-            };
-            defer if (ptr_to_mcv_lock) |lock| self.register_manager.unlockReg(lock);
-
-            const base_bind: ReadArg.Bind = .{ .mcv = ptr_to_mcv };
-
-            const ptr_ty = try pt.singleMutPtrType(elem_ty);
-
-            return try self.ptrElemVal(base_bind, index_bind, ptr_ty, maybe_inst);
-        },
-        else => return self.fail("TODO implement array_elem_val for {}", .{mcv}),
-    }
-}
-
-fn airArrayElemVal(self: *Self, inst: Air.Inst.Index) !void {
-    const bin_op = self.air.instructions.items(.data)[@intFromEnum(inst)].bin_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const array_bind: ReadArg.Bind = .{ .inst = bin_op.lhs };
-        const index_bind: ReadArg.Bind = .{ .inst = bin_op.rhs };
-        const array_ty = self.typeOf(bin_op.lhs);
-
-        break :result try self.arrayElemVal(array_bind, index_bind, array_ty, inst);
-    };
-    return self.finishAir(inst, result, .{ bin_op.lhs, bin_op.rhs, .none });
-}
-
-fn airPtrElemVal(self: *Self, inst: Air.Inst.Index) !void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const bin_op = self.air.instructions.items(.data)[@intFromEnum(inst)].bin_op;
-    const ptr_ty = self.typeOf(bin_op.lhs);
-    const result: MCValue = if (!ptr_ty.isVolatilePtr(zcu) and self.liveness.isUnused(inst)) .dead else result: {
-        const base_bind: ReadArg.Bind = .{ .inst = bin_op.lhs };
-        const index_bind: ReadArg.Bind = .{ .inst = bin_op.rhs };
-
-        break :result try self.ptrElemVal(base_bind, index_bind, ptr_ty, inst);
-    };
-    return self.finishAir(inst, result, .{ bin_op.lhs, bin_op.rhs, .none });
-}
-
-fn airPtrElemPtr(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_pl = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_pl;
-    const extra = self.air.extraData(Air.Bin, ty_pl.payload).data;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const ptr_bind: ReadArg.Bind = .{ .inst = extra.lhs };
-        const index_bind: ReadArg.Bind = .{ .inst = extra.rhs };
-
-        const ptr_ty = self.typeOf(extra.lhs);
-        const index_ty = self.typeOf(extra.rhs);
-
-        const addr = try self.ptrArithmetic(.ptr_add, ptr_bind, index_bind, ptr_ty, index_ty, null);
-        break :result addr;
-    };
-    return self.finishAir(inst, result, .{ extra.lhs, extra.rhs, .none });
-}
-
-fn airSetUnionTag(self: *Self, inst: Air.Inst.Index) !void {
-    const bin_op = self.air.instructions.items(.data)[@intFromEnum(inst)].bin_op;
-    _ = bin_op;
-    return self.fail("TODO implement airSetUnionTag for {}", .{self.target.cpu.arch});
-    // return self.finishAir(inst, result, .{ bin_op.lhs, bin_op.rhs, .none });
-}
-
-fn airGetUnionTag(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    _ = ty_op;
-    return self.fail("TODO implement airGetUnionTag for {}", .{self.target.cpu.arch});
-    // return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airClz(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    _ = ty_op;
-    return self.fail("TODO implement airClz for {}", .{self.target.cpu.arch});
-    // return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airCtz(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    _ = ty_op;
-    return self.fail("TODO implement airCtz for {}", .{self.target.cpu.arch});
-    // return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airPopcount(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    _ = ty_op;
-    return self.fail("TODO implement airPopcount for {}", .{self.target.cpu.arch});
-    // return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airAbs(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    _ = ty_op;
-    return self.fail("TODO implement airAbs for {}", .{self.target.cpu.arch});
-    // return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airByteSwap(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    _ = ty_op;
-    return self.fail("TODO implement airByteSwap for {}", .{self.target.cpu.arch});
-    // return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airBitReverse(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    _ = ty_op;
-    return self.fail("TODO implement airBitReverse for {}", .{self.target.cpu.arch});
-    // return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airUnaryMath(self: *Self, inst: Air.Inst.Index) !void {
-    const un_op = self.air.instructions.items(.data)[@intFromEnum(inst)].un_op;
-    const result: MCValue = if (self.liveness.isUnused(inst))
-        .dead
-    else
-        return self.fail("TODO implement airUnaryMath for {}", .{self.target.cpu.arch});
-    return self.finishAir(inst, result, .{ un_op, .none, .none });
-}
-
-fn reuseOperand(
-    self: *Self,
-    inst: Air.Inst.Index,
-    operand: Air.Inst.Ref,
-    op_index: Air.Liveness.OperandInt,
-    mcv: MCValue,
-) bool {
-    if (!self.liveness.operandDies(inst, op_index))
-        return false;
-
-    switch (mcv) {
-        .register => |reg| {
-            // We assert that this register is allocatable by asking
-            // for its index
-            const index = RegisterManager.indexOfRegIntoTracked(reg).?; // see note above
-            if (!self.register_manager.isRegFree(reg)) {
-                self.register_manager.registers[index] = inst;
-            }
-
-            log.debug("%{d} => {} (reused)", .{ inst, reg });
-        },
-        .stack_offset => |off| {
-            log.debug("%{d} => stack offset {d} (reused)", .{ inst, off });
-        },
-        .cpsr_flags => {
-            log.debug("%{d} => cpsr_flags (reused)", .{inst});
-        },
-        else => return false,
-    }
-
-    // Prevent the operand deaths processing code from deallocating it.
-    self.reused_operands.set(op_index);
-
-    // That makes us responsible for doing the rest of the stuff that processDeath would have done.
-    const branch = &self.branch_stack.items[self.branch_stack.items.len - 1];
-    branch.inst_table.putAssumeCapacity(operand.toIndex().?, .dead);
-
-    return true;
-}
-
-fn load(self: *Self, dst_mcv: MCValue, ptr: MCValue, ptr_ty: Type) InnerError!void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const elem_ty = ptr_ty.childType(zcu);
-    const elem_size: u32 = @intCast(elem_ty.abiSize(zcu));
-
-    switch (ptr) {
-        .none => unreachable,
-        .undef => unreachable,
-        .unreach => unreachable,
-        .dead => unreachable,
-        .cpsr_flags,
-        .register_c_flag,
-        .register_v_flag,
-        => unreachable, // cannot hold an address
-        .immediate => |imm| {
-            try self.setRegOrMem(elem_ty, dst_mcv, .{ .memory = imm });
-        },
-        .ptr_stack_offset => |off| {
-            try self.setRegOrMem(elem_ty, dst_mcv, .{ .stack_offset = off });
-        },
-        .register => |reg| {
-            const reg_lock = self.register_manager.lockReg(reg);
-            defer if (reg_lock) |reg_locked| self.register_manager.unlockReg(reg_locked);
-
-            switch (dst_mcv) {
-                .register => |dst_reg| {
-                    try self.genLdrRegister(dst_reg, reg, elem_ty);
-                },
-                .stack_offset => |off| {
-                    if (elem_size <= 4) {
-                        const tmp_reg = try self.register_manager.allocReg(null, gp);
-                        const tmp_reg_lock = self.register_manager.lockRegAssumeUnused(tmp_reg);
-                        defer self.register_manager.unlockReg(tmp_reg_lock);
-
-                        try self.load(.{ .register = tmp_reg }, ptr, ptr_ty);
-                        try self.genSetStack(elem_ty, off, MCValue{ .register = tmp_reg });
-                    } else {
-                        // TODO optimize the register allocation
-                        const regs = try self.register_manager.allocRegs(4, .{ null, null, null, null }, gp);
-                        const regs_locks = self.register_manager.lockRegsAssumeUnused(4, regs);
-                        defer for (regs_locks) |reg_locked| {
-                            self.register_manager.unlockReg(reg_locked);
-                        };
-
-                        const src_reg = reg;
-                        const dst_reg = regs[0];
-                        const len_reg = regs[1];
-                        const count_reg = regs[2];
-                        const tmp_reg = regs[3];
-
-                        // sub dst_reg, fp, #off
-                        try self.genSetReg(ptr_ty, dst_reg, .{ .ptr_stack_offset = off });
-
-                        // mov len, #elem_size
-                        try self.genSetReg(Type.usize, len_reg, .{ .immediate = elem_size });
-
-                        // memcpy(src, dst, len)
-                        try self.genInlineMemcpy(src_reg, dst_reg, len_reg, count_reg, tmp_reg);
-                    }
-                },
-                else => unreachable, // attempting to load into non-register or non-stack MCValue
-            }
-        },
-        .memory,
-        .stack_offset,
-        .stack_argument_offset,
-        => {
-            const reg = try self.register_manager.allocReg(null, gp);
-            const reg_lock = self.register_manager.lockRegAssumeUnused(reg);
-            defer self.register_manager.unlockReg(reg_lock);
-
-            try self.genSetReg(ptr_ty, reg, ptr);
-            try self.load(dst_mcv, .{ .register = reg }, ptr_ty);
-        },
-    }
-}
-
-fn airLoad(self: *Self, inst: Air.Inst.Index) !void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const elem_ty = self.typeOfIndex(inst);
-    const result: MCValue = result: {
-        if (!elem_ty.hasRuntimeBits(zcu))
-            break :result MCValue.none;
-
-        const ptr = try self.resolveInst(ty_op.operand);
-        const is_volatile = self.typeOf(ty_op.operand).isVolatilePtr(zcu);
-        if (self.liveness.isUnused(inst) and !is_volatile)
-            break :result MCValue.dead;
-
-        const dest_mcv: MCValue = blk: {
-            const ptr_fits_dest = elem_ty.abiSize(zcu) <= 4;
-            if (ptr_fits_dest and self.reuseOperand(inst, ty_op.operand, 0, ptr)) {
-                // The MCValue that holds the pointer can be re-used as the value.
-                break :blk ptr;
-            } else {
-                break :blk try self.allocRegOrMem(elem_ty, true, inst);
-            }
-        };
-        try self.load(dest_mcv, ptr, self.typeOf(ty_op.operand));
-
-        break :result dest_mcv;
-    };
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn store(self: *Self, ptr: MCValue, value: MCValue, ptr_ty: Type, value_ty: Type) InnerError!void {
-    const pt = self.pt;
-    const elem_size: u32 = @intCast(value_ty.abiSize(pt.zcu));
-
-    switch (ptr) {
-        .none => unreachable,
-        .undef => unreachable,
-        .unreach => unreachable,
-        .dead => unreachable,
-        .cpsr_flags,
-        .register_c_flag,
-        .register_v_flag,
-        => unreachable, // cannot hold an address
-        .immediate => |imm| {
-            try self.setRegOrMem(value_ty, .{ .memory = imm }, value);
-        },
-        .ptr_stack_offset => |off| {
-            try self.genSetStack(value_ty, off, value);
-        },
-        .register => |addr_reg| {
-            const addr_reg_lock = self.register_manager.lockReg(addr_reg);
-            defer if (addr_reg_lock) |reg| self.register_manager.unlockReg(reg);
-
-            switch (value) {
-                .dead => unreachable,
-                .undef => {
-                    try self.genSetReg(value_ty, addr_reg, value);
-                },
-                .register => |value_reg| {
-                    try self.genStrRegister(value_reg, addr_reg, value_ty);
-                },
-                else => {
-                    if (elem_size <= 4) {
-                        const tmp_reg = try self.register_manager.allocReg(null, gp);
-                        const tmp_reg_lock = self.register_manager.lockRegAssumeUnused(tmp_reg);
-                        defer self.register_manager.unlockReg(tmp_reg_lock);
-
-                        try self.genSetReg(value_ty, tmp_reg, value);
-                        try self.store(ptr, .{ .register = tmp_reg }, ptr_ty, value_ty);
-                    } else {
-                        const regs = try self.register_manager.allocRegs(4, .{ null, null, null, null }, gp);
-                        const regs_locks = self.register_manager.lockRegsAssumeUnused(4, regs);
-                        defer for (regs_locks) |reg| {
-                            self.register_manager.unlockReg(reg);
-                        };
-
-                        const src_reg = regs[0];
-                        const dst_reg = addr_reg;
-                        const len_reg = regs[1];
-                        const count_reg = regs[2];
-                        const tmp_reg = regs[3];
-
-                        switch (value) {
-                            .stack_offset => |off| {
-                                // sub src_reg, fp, #off
-                                try self.genSetReg(ptr_ty, src_reg, .{ .ptr_stack_offset = off });
-                            },
-                            .memory => |addr| try self.genSetReg(ptr_ty, src_reg, .{ .immediate = @intCast(addr) }),
-                            .stack_argument_offset => |off| {
-                                _ = try self.addInst(.{
-                                    .tag = .ldr_ptr_stack_argument,
-                                    .data = .{ .r_stack_offset = .{
-                                        .rt = src_reg,
-                                        .stack_offset = off,
-                                    } },
-                                });
-                            },
-                            else => return self.fail("TODO store {} to register", .{value}),
-                        }
-
-                        // mov len, #elem_size
-                        try self.genSetReg(Type.usize, len_reg, .{ .immediate = elem_size });
-
-                        // memcpy(src, dst, len)
-                        try self.genInlineMemcpy(src_reg, dst_reg, len_reg, count_reg, tmp_reg);
-                    }
-                },
-            }
-        },
-        .memory,
-        .stack_offset,
-        .stack_argument_offset,
-        => {
-            const addr_reg = try self.copyToTmpRegister(ptr_ty, ptr);
-            try self.store(.{ .register = addr_reg }, value, ptr_ty, value_ty);
-        },
-    }
-}
-
-fn airStore(self: *Self, inst: Air.Inst.Index, safety: bool) !void {
-    if (safety) {
-        // TODO if the value is undef, write 0xaa bytes to dest
-    } else {
-        // TODO if the value is undef, don't lower this instruction
-    }
-    const bin_op = self.air.instructions.items(.data)[@intFromEnum(inst)].bin_op;
-    const ptr = try self.resolveInst(bin_op.lhs);
-    const value = try self.resolveInst(bin_op.rhs);
-    const ptr_ty = self.typeOf(bin_op.lhs);
-    const value_ty = self.typeOf(bin_op.rhs);
-
-    try self.store(ptr, value, ptr_ty, value_ty);
-
-    return self.finishAir(inst, .dead, .{ bin_op.lhs, bin_op.rhs, .none });
-}
-
-fn airStructFieldPtr(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_pl = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_pl;
-    const extra = self.air.extraData(Air.StructField, ty_pl.payload).data;
-    const result = try self.structFieldPtr(inst, extra.struct_operand, extra.field_index);
-    return self.finishAir(inst, result, .{ extra.struct_operand, .none, .none });
-}
-
-fn airStructFieldPtrIndex(self: *Self, inst: Air.Inst.Index, index: u8) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result = try self.structFieldPtr(inst, ty_op.operand, index);
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn structFieldPtr(self: *Self, inst: Air.Inst.Index, operand: Air.Inst.Ref, index: u32) !MCValue {
-    return if (self.liveness.isUnused(inst)) .dead else result: {
-        const pt = self.pt;
-        const zcu = pt.zcu;
-        const mcv = try self.resolveInst(operand);
-        const ptr_ty = self.typeOf(operand);
-        const struct_ty = ptr_ty.childType(zcu);
-        const struct_field_offset: u32 = @intCast(struct_ty.structFieldOffset(index, zcu));
-        switch (mcv) {
-            .ptr_stack_offset => |off| {
-                break :result MCValue{ .ptr_stack_offset = off - struct_field_offset };
-            },
-            else => {
-                const lhs_bind: ReadArg.Bind = .{ .mcv = mcv };
-                const rhs_bind: ReadArg.Bind = .{ .mcv = .{ .immediate = struct_field_offset } };
-
-                break :result try self.addSub(.add, lhs_bind, rhs_bind, Type.usize, Type.usize, null);
-            },
-        }
-    };
-}
-
-fn airStructFieldVal(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_pl = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_pl;
-    const extra = self.air.extraData(Air.StructField, ty_pl.payload).data;
-    const operand = extra.struct_operand;
-    const index = extra.field_index;
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const mcv = try self.resolveInst(operand);
-        const struct_ty = self.typeOf(operand);
-        const struct_field_offset: u32 = @intCast(struct_ty.structFieldOffset(index, zcu));
-        const struct_field_ty = struct_ty.fieldType(index, zcu);
-
-        switch (mcv) {
-            .dead, .unreach => unreachable,
-            .stack_argument_offset => |off| {
-                break :result MCValue{ .stack_argument_offset = off + struct_field_offset };
-            },
-            .stack_offset => |off| {
-                break :result MCValue{ .stack_offset = off - struct_field_offset };
-            },
-            .memory => |addr| {
-                break :result MCValue{ .memory = addr + struct_field_offset };
-            },
-            .register_c_flag,
-            .register_v_flag,
-            => |reg| {
-                const reg_lock = self.register_manager.lockRegAssumeUnused(reg);
-                defer self.register_manager.unlockReg(reg_lock);
-
-                const field: MCValue = switch (index) {
-                    // get wrapped value: return register
-                    0 => MCValue{ .register = reg },
-
-                    // get overflow bit: return C or V flag
-                    1 => MCValue{ .cpsr_flags = switch (mcv) {
-                        .register_c_flag => .cs,
-                        .register_v_flag => .vs,
-                        else => unreachable,
-                    } },
-
-                    else => unreachable,
-                };
-
-                if (self.reuseOperand(inst, operand, 0, field)) {
-                    break :result field;
-                } else {
-                    // Copy to new register
-                    const dest_reg = try self.register_manager.allocReg(null, gp);
-                    try self.genSetReg(struct_field_ty, dest_reg, field);
-
-                    break :result MCValue{ .register = dest_reg };
-                }
-            },
-            .register => {
-                var operand_reg: Register = undefined;
-                var dest_reg: Register = undefined;
-
-                const read_args = [_]ReadArg{
-                    .{ .ty = struct_ty, .bind = .{ .mcv = mcv }, .class = gp, .reg = &operand_reg },
-                };
-                const write_args = [_]WriteArg{
-                    .{ .ty = struct_field_ty, .bind = .none, .class = gp, .reg = &dest_reg },
-                };
-                try self.allocRegs(
-                    &read_args,
-                    &write_args,
-                    ReuseMetadata{
-                        .corresponding_inst = inst,
-                        .operand_mapping = &.{0},
-                    },
-                );
-
-                const field_bit_offset = struct_field_offset * 8;
-                const field_bit_size: u32 = @intCast(struct_field_ty.abiSize(zcu) * 8);
-
-                _ = try self.addInst(.{
-                    .tag = if (struct_field_ty.isSignedInt(zcu)) Mir.Inst.Tag.sbfx else .ubfx,
-                    .data = .{ .rr_lsb_width = .{
-                        .rd = dest_reg,
-                        .rn = operand_reg,
-                        .lsb = @intCast(field_bit_offset),
-                        .width = @intCast(field_bit_size),
-                    } },
-                });
-
-                break :result MCValue{ .register = dest_reg };
-            },
-            else => return self.fail("TODO implement codegen struct_field_val for {}", .{mcv}),
-        }
-    };
-
-    return self.finishAir(inst, result, .{ extra.struct_operand, .none, .none });
-}
-
-fn airFieldParentPtr(self: *Self, inst: Air.Inst.Index) !void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const ty_pl = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_pl;
-    const extra = self.air.extraData(Air.FieldParentPtr, ty_pl.payload).data;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const field_ptr = try self.resolveInst(extra.field_ptr);
-        const struct_ty = ty_pl.ty.toType().childType(zcu);
-
-        if (struct_ty.zigTypeTag(zcu) == .@"union") {
-            return self.fail("TODO implement @fieldParentPtr codegen for unions", .{});
-        }
-
-        const struct_field_offset: u32 = @intCast(struct_ty.structFieldOffset(extra.field_index, zcu));
-        switch (field_ptr) {
-            .ptr_stack_offset => |off| {
-                break :result MCValue{ .ptr_stack_offset = off + struct_field_offset };
-            },
-            else => {
-                const lhs_bind: ReadArg.Bind = .{ .mcv = field_ptr };
-                const rhs_bind: ReadArg.Bind = .{ .mcv = .{ .immediate = struct_field_offset } };
-
-                break :result try self.addSub(.sub, lhs_bind, rhs_bind, Type.usize, Type.usize, null);
-            },
-        }
-    };
-    return self.finishAir(inst, result, .{ extra.field_ptr, .none, .none });
-}
-
-/// An argument to a Mir instruction which is read (and possibly also
-/// written to) by the respective instruction
-const ReadArg = struct {
-    ty: Type,
-    bind: Bind,
-    class: RegisterManager.RegisterBitSet,
-    reg: *Register,
-
-    const Bind = union(enum) {
-        inst: Air.Inst.Ref,
-        mcv: MCValue,
-
-        fn resolveToMcv(bind: Bind, function: *Self) InnerError!MCValue {
-            return switch (bind) {
-                .inst => |inst| try function.resolveInst(inst),
-                .mcv => |mcv| mcv,
-            };
-        }
-
-        fn resolveToImmediate(bind: Bind, function: *Self) InnerError!?u32 {
-            switch (bind) {
-                .inst => |inst| {
-                    // TODO resolve independently of inst_table
-                    const mcv = try function.resolveInst(inst);
-                    switch (mcv) {
-                        .immediate => |imm| return imm,
-                        else => return null,
-                    }
-                },
-                .mcv => |mcv| {
-                    switch (mcv) {
-                        .immediate => |imm| return imm,
-                        else => return null,
-                    }
-                },
-            }
-        }
-    };
-};
-
-/// An argument to a Mir instruction which is written to (but not read
-/// from) by the respective instruction
-const WriteArg = struct {
-    ty: Type,
-    bind: Bind,
-    class: RegisterManager.RegisterBitSet,
-    reg: *Register,
-
-    const Bind = union(enum) {
-        reg: Register,
-        none: void,
-    };
-};
-
-/// Holds all data necessary for enabling the potential reuse of
-/// operand registers as destinations
-const ReuseMetadata = struct {
-    corresponding_inst: Air.Inst.Index,
-
-    /// Maps every element index of read_args to the corresponding
-    /// index in the Air instruction
-    ///
-    /// When the order of read_args corresponds exactly to the order
-    /// of the inputs of the Air instruction, this would be e.g.
-    /// &.{ 0, 1 }. However, when the order is not the same or some
-    /// inputs to the Air instruction are omitted (e.g. when they can
-    /// be represented as immediates to the Mir instruction),
-    /// operand_mapping should reflect that fact.
-    operand_mapping: []const Air.Liveness.OperandInt,
-};
-
-/// Allocate a set of registers for use as arguments for a Mir
-/// instruction
-///
-/// If the Mir instruction these registers are allocated for
-/// corresponds exactly to a single Air instruction, populate
-/// reuse_metadata in order to enable potential reuse of an operand as
-/// the destination (provided that that operand dies in this
-/// instruction).
-///
-/// Reusing an operand register as destination is the only time two
-/// arguments may share the same register. In all other cases,
-/// allocRegs guarantees that a register will never be allocated to
-/// more than one argument.
-///
-/// Furthermore, allocReg guarantees that all arguments which are
-/// already bound to registers before calling allocRegs will not
-/// change their register binding. This is done by locking these
-/// registers.
-fn allocRegs(
-    self: *Self,
-    read_args: []const ReadArg,
-    write_args: []const WriteArg,
-    reuse_metadata: ?ReuseMetadata,
-) InnerError!void {
-    // Air instructions have exactly one output
-    assert(!(reuse_metadata != null and write_args.len != 1)); // see note above
-
-    // The operand mapping is a 1:1 mapping of read args to their
-    // corresponding operand index in the Air instruction
-    assert(!(reuse_metadata != null and reuse_metadata.?.operand_mapping.len != read_args.len)); // see note above
-
-    const locks = try self.gpa.alloc(?RegisterLock, read_args.len + write_args.len);
-    defer self.gpa.free(locks);
-    const read_locks = locks[0..read_args.len];
-    const write_locks = locks[read_args.len..];
-
-    @memset(locks, null);
-    defer for (locks) |lock| {
-        if (lock) |locked_reg| self.register_manager.unlockReg(locked_reg);
-    };
-
-    // When we reuse a read_arg as a destination, the corresponding
-    // MCValue of the read_arg will be set to .dead. In that case, we
-    // skip allocating this read_arg.
-    var reused_read_arg: ?usize = null;
-
-    // Lock all args which are already allocated to registers
-    for (read_args, 0..) |arg, i| {
-        const mcv = try arg.bind.resolveToMcv(self);
-        if (mcv == .register) {
-            read_locks[i] = self.register_manager.lockReg(mcv.register);
-        }
-    }
-
-    for (write_args, 0..) |arg, i| {
-        if (arg.bind == .reg) {
-            write_locks[i] = self.register_manager.lockReg(arg.bind.reg);
-        }
-    }
-
-    // Allocate registers for all args which aren't allocated to
-    // registers yet
-    for (read_args, 0..) |arg, i| {
-        const mcv = try arg.bind.resolveToMcv(self);
-        if (mcv == .register) {
-            arg.reg.* = mcv.register;
-        } else {
-            const track_inst: ?Air.Inst.Index = switch (arg.bind) {
-                .inst => |inst| inst.toIndex().?,
-                else => null,
-            };
-            arg.reg.* = try self.register_manager.allocReg(track_inst, arg.class);
-            read_locks[i] = self.register_manager.lockReg(arg.reg.*);
-        }
-    }
-
-    if (reuse_metadata != null) {
-        const inst = reuse_metadata.?.corresponding_inst;
-        const operand_mapping = reuse_metadata.?.operand_mapping;
-        const arg = write_args[0];
-        if (arg.bind == .reg) {
-            arg.reg.* = arg.bind.reg;
-        } else {
-            reuse_operand: for (read_args, 0..) |read_arg, i| {
-                if (read_arg.bind == .inst) {
-                    const operand = read_arg.bind.inst;
-                    const mcv = try self.resolveInst(operand);
-                    if (mcv == .register and
-                        std.meta.eql(arg.class, read_arg.class) and
-                        self.reuseOperand(inst, operand, operand_mapping[i], mcv))
-                    {
-                        arg.reg.* = mcv.register;
-                        write_locks[0] = null;
-                        reused_read_arg = i;
-                        break :reuse_operand;
-                    }
-                }
-            } else {
-                arg.reg.* = try self.register_manager.allocReg(inst, arg.class);
-                write_locks[0] = self.register_manager.lockReg(arg.reg.*);
-            }
-        }
-    } else {
-        for (write_args, 0..) |arg, i| {
-            if (arg.bind == .reg) {
-                arg.reg.* = arg.bind.reg;
-            } else {
-                arg.reg.* = try self.register_manager.allocReg(null, arg.class);
-                write_locks[i] = self.register_manager.lockReg(arg.reg.*);
-            }
-        }
-    }
-
-    // For all read_args which need to be moved from non-register to
-    // register, perform the move
-    for (read_args, 0..) |arg, i| {
-        if (reused_read_arg) |j| {
-            // Check whether this read_arg was reused
-            if (i == j) continue;
-        }
-
-        const mcv = try arg.bind.resolveToMcv(self);
-        if (mcv != .register) {
-            if (arg.bind == .inst) {
-                const branch = &self.branch_stack.items[self.branch_stack.items.len - 1];
-                const inst = arg.bind.inst.toIndex().?;
-
-                // Overwrite the MCValue associated with this inst
-                branch.inst_table.putAssumeCapacity(inst, .{ .register = arg.reg.* });
-
-                // If the previous MCValue occupied some space we track, we
-                // need to make sure it is marked as free now.
-                switch (mcv) {
-                    .cpsr_flags => {
-                        assert(self.cpsr_flags_inst.? == inst);
-                        self.cpsr_flags_inst = null;
-                    },
-                    .register => |prev_reg| {
-                        assert(!self.register_manager.isRegFree(prev_reg));
-                        self.register_manager.freeReg(prev_reg);
-                    },
-                    else => {},
-                }
-            }
-
-            try self.genSetReg(arg.ty, arg.reg.*, mcv);
-        }
-    }
-}
-
-/// Wrapper around allocRegs and addInst tailored for specific Mir
-/// instructions which are binary operations acting on two registers
-///
-/// Returns the destination register
-fn binOpRegister(
-    self: *Self,
-    mir_tag: Mir.Inst.Tag,
-    lhs_bind: ReadArg.Bind,
-    rhs_bind: ReadArg.Bind,
-    lhs_ty: Type,
-    rhs_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) !MCValue {
-    var lhs_reg: Register = undefined;
-    var rhs_reg: Register = undefined;
-    var dest_reg: Register = undefined;
-
-    const read_args = [_]ReadArg{
-        .{ .ty = lhs_ty, .bind = lhs_bind, .class = gp, .reg = &lhs_reg },
-        .{ .ty = rhs_ty, .bind = rhs_bind, .class = gp, .reg = &rhs_reg },
-    };
-    const write_args = [_]WriteArg{
-        .{ .ty = lhs_ty, .bind = .none, .class = gp, .reg = &dest_reg },
-    };
-    try self.allocRegs(
-        &read_args,
-        &write_args,
-        if (maybe_inst) |inst| .{
-            .corresponding_inst = inst,
-            .operand_mapping = &.{ 0, 1 },
-        } else null,
-    );
-
-    const mir_data: Mir.Inst.Data = switch (mir_tag) {
-        .add,
-        .adds,
-        .sub,
-        .subs,
-        .@"and",
-        .orr,
-        .eor,
-        => .{ .rr_op = .{
-            .rd = dest_reg,
-            .rn = lhs_reg,
-            .op = Instruction.Operand.reg(rhs_reg, Instruction.Operand.Shift.none),
-        } },
-        .lsl,
-        .asr,
-        .lsr,
-        => .{ .rr_shift = .{
-            .rd = dest_reg,
-            .rm = lhs_reg,
-            .shift_amount = Instruction.ShiftAmount.reg(rhs_reg),
-        } },
-        .mul,
-        .smulbb,
-        => .{ .rrr = .{
-            .rd = dest_reg,
-            .rn = lhs_reg,
-            .rm = rhs_reg,
-        } },
-        else => unreachable,
-    };
-
-    _ = try self.addInst(.{
-        .tag = mir_tag,
-        .data = mir_data,
-    });
-
-    return MCValue{ .register = dest_reg };
-}
-
-/// Wrapper around allocRegs and addInst tailored for specific Mir
-/// instructions which are binary operations acting on a register and
-/// an immediate
-///
-/// Returns the destination register
-fn binOpImmediate(
-    self: *Self,
-    mir_tag: Mir.Inst.Tag,
-    lhs_bind: ReadArg.Bind,
-    rhs_immediate: u32,
-    lhs_ty: Type,
-    lhs_and_rhs_swapped: bool,
-    maybe_inst: ?Air.Inst.Index,
-) !MCValue {
-    var lhs_reg: Register = undefined;
-    var dest_reg: Register = undefined;
-
-    const read_args = [_]ReadArg{
-        .{ .ty = lhs_ty, .bind = lhs_bind, .class = gp, .reg = &lhs_reg },
-    };
-    const write_args = [_]WriteArg{
-        .{ .ty = lhs_ty, .bind = .none, .class = gp, .reg = &dest_reg },
-    };
-    const operand_mapping: []const Air.Liveness.OperandInt = if (lhs_and_rhs_swapped) &.{1} else &.{0};
-    try self.allocRegs(
-        &read_args,
-        &write_args,
-        if (maybe_inst) |inst| .{
-            .corresponding_inst = inst,
-            .operand_mapping = operand_mapping,
-        } else null,
-    );
-
-    const mir_data: Mir.Inst.Data = switch (mir_tag) {
-        .add,
-        .adds,
-        .sub,
-        .subs,
-        .@"and",
-        .orr,
-        .eor,
-        => .{ .rr_op = .{
-            .rd = dest_reg,
-            .rn = lhs_reg,
-            .op = Instruction.Operand.fromU32(rhs_immediate).?,
-        } },
-        .lsl,
-        .asr,
-        .lsr,
-        => .{ .rr_shift = .{
-            .rd = dest_reg,
-            .rm = lhs_reg,
-            .shift_amount = Instruction.ShiftAmount.imm(@intCast(rhs_immediate)),
-        } },
-        else => unreachable,
-    };
-
-    _ = try self.addInst(.{
-        .tag = mir_tag,
-        .data = mir_data,
-    });
-
-    return MCValue{ .register = dest_reg };
-}
-
-fn addSub(
-    self: *Self,
-    tag: Air.Inst.Tag,
-    lhs_bind: ReadArg.Bind,
-    rhs_bind: ReadArg.Bind,
-    lhs_ty: Type,
-    rhs_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) InnerError!MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    switch (lhs_ty.zigTypeTag(zcu)) {
-        .float => return self.fail("TODO ARM binary operations on floats", .{}),
-        .vector => return self.fail("TODO ARM binary operations on vectors", .{}),
-        .int => {
-            assert(lhs_ty.eql(rhs_ty, zcu));
-            const int_info = lhs_ty.intInfo(zcu);
-            if (int_info.bits <= 32) {
-                const lhs_immediate = try lhs_bind.resolveToImmediate(self);
-                const rhs_immediate = try rhs_bind.resolveToImmediate(self);
-
-                // Only say yes if the operation is
-                // commutative, i.e. we can swap both of the
-                // operands
-                const lhs_immediate_ok = switch (tag) {
-                    .add => if (lhs_immediate) |imm| Instruction.Operand.fromU32(imm) != null else false,
-                    .sub => false,
-                    else => unreachable,
-                };
-                const rhs_immediate_ok = switch (tag) {
-                    .add,
-                    .sub,
-                    => if (rhs_immediate) |imm| Instruction.Operand.fromU32(imm) != null else false,
-                    else => unreachable,
-                };
-
-                const mir_tag: Mir.Inst.Tag = switch (tag) {
-                    .add => .add,
-                    .sub => .sub,
-                    else => unreachable,
-                };
-
-                if (rhs_immediate_ok) {
-                    return try self.binOpImmediate(mir_tag, lhs_bind, rhs_immediate.?, lhs_ty, false, maybe_inst);
-                } else if (lhs_immediate_ok) {
-                    // swap lhs and rhs
-                    return try self.binOpImmediate(mir_tag, rhs_bind, lhs_immediate.?, rhs_ty, true, maybe_inst);
-                } else {
-                    return try self.binOpRegister(mir_tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, maybe_inst);
-                }
-            } else {
-                return self.fail("TODO ARM binary operations on integers > u32/i32", .{});
-            }
-        },
-        else => unreachable,
-    }
-}
-
-fn mul(
-    self: *Self,
-    lhs_bind: ReadArg.Bind,
-    rhs_bind: ReadArg.Bind,
-    lhs_ty: Type,
-    rhs_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) InnerError!MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    switch (lhs_ty.zigTypeTag(zcu)) {
-        .float => return self.fail("TODO ARM binary operations on floats", .{}),
-        .vector => return self.fail("TODO ARM binary operations on vectors", .{}),
-        .int => {
-            assert(lhs_ty.eql(rhs_ty, zcu));
-            const int_info = lhs_ty.intInfo(zcu);
-            if (int_info.bits <= 32) {
-                // TODO add optimisations for multiplication
-                // with immediates, for example a * 2 can be
-                // lowered to a << 1
-                return try self.binOpRegister(.mul, lhs_bind, rhs_bind, lhs_ty, rhs_ty, maybe_inst);
-            } else {
-                return self.fail("TODO ARM binary operations on integers > u32/i32", .{});
-            }
-        },
-        else => unreachable,
-    }
-}
-
-fn divFloat(
-    self: *Self,
-    lhs_bind: ReadArg.Bind,
-    rhs_bind: ReadArg.Bind,
-    lhs_ty: Type,
-    rhs_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) InnerError!MCValue {
-    _ = lhs_bind;
-    _ = rhs_bind;
-    _ = rhs_ty;
-    _ = maybe_inst;
-
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    switch (lhs_ty.zigTypeTag(zcu)) {
-        .float => return self.fail("TODO ARM binary operations on floats", .{}),
-        .vector => return self.fail("TODO ARM binary operations on vectors", .{}),
-        else => unreachable,
-    }
-}
-
-fn divTrunc(
-    self: *Self,
-    lhs_bind: ReadArg.Bind,
-    rhs_bind: ReadArg.Bind,
-    lhs_ty: Type,
-    rhs_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) InnerError!MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    switch (lhs_ty.zigTypeTag(zcu)) {
-        .float => return self.fail("TODO ARM binary operations on floats", .{}),
-        .vector => return self.fail("TODO ARM binary operations on vectors", .{}),
-        .int => {
-            assert(lhs_ty.eql(rhs_ty, zcu));
-            const int_info = lhs_ty.intInfo(zcu);
-            if (int_info.bits <= 32) {
-                switch (int_info.signedness) {
-                    .signed => {
-                        return self.fail("TODO ARM signed integer division", .{});
-                    },
-                    .unsigned => {
-                        const rhs_immediate = try rhs_bind.resolveToImmediate(self);
-
-                        if (rhs_immediate) |imm| {
-                            if (std.math.isPowerOfTwo(imm)) {
-                                const shift = std.math.log2_int(u32, imm);
-                                return try self.binOpImmediate(.lsr, lhs_bind, shift, lhs_ty, false, maybe_inst);
-                            } else {
-                                return self.fail("TODO ARM integer division by constants", .{});
-                            }
-                        } else {
-                            return self.fail("TODO ARM integer division", .{});
-                        }
-                    },
-                }
-            } else {
-                return self.fail("TODO ARM integer division for integers > u32/i32", .{});
-            }
-        },
-        else => unreachable,
-    }
-}
-
-fn divFloor(
-    self: *Self,
-    lhs_bind: ReadArg.Bind,
-    rhs_bind: ReadArg.Bind,
-    lhs_ty: Type,
-    rhs_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) InnerError!MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    switch (lhs_ty.zigTypeTag(zcu)) {
-        .float => return self.fail("TODO ARM binary operations on floats", .{}),
-        .vector => return self.fail("TODO ARM binary operations on vectors", .{}),
-        .int => {
-            assert(lhs_ty.eql(rhs_ty, zcu));
-            const int_info = lhs_ty.intInfo(zcu);
-            if (int_info.bits <= 32) {
-                switch (int_info.signedness) {
-                    .signed => {
-                        return self.fail("TODO ARM signed integer division", .{});
-                    },
-                    .unsigned => {
-                        const rhs_immediate = try rhs_bind.resolveToImmediate(self);
-
-                        if (rhs_immediate) |imm| {
-                            if (std.math.isPowerOfTwo(imm)) {
-                                const shift = std.math.log2_int(u32, imm);
-                                return try self.binOpImmediate(.lsr, lhs_bind, shift, lhs_ty, false, maybe_inst);
-                            } else {
-                                return self.fail("TODO ARM integer division by constants", .{});
-                            }
-                        } else {
-                            return self.fail("TODO ARM integer division", .{});
-                        }
-                    },
-                }
-            } else {
-                return self.fail("TODO ARM integer division for integers > u32/i32", .{});
-            }
-        },
-        else => unreachable,
-    }
-}
-
-fn divExact(
-    self: *Self,
-    lhs_bind: ReadArg.Bind,
-    rhs_bind: ReadArg.Bind,
-    lhs_ty: Type,
-    rhs_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) InnerError!MCValue {
-    _ = lhs_bind;
-    _ = rhs_bind;
-    _ = rhs_ty;
-    _ = maybe_inst;
-
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    switch (lhs_ty.zigTypeTag(zcu)) {
-        .float => return self.fail("TODO ARM binary operations on floats", .{}),
-        .vector => return self.fail("TODO ARM binary operations on vectors", .{}),
-        .int => return self.fail("TODO ARM div_exact", .{}),
-        else => unreachable,
-    }
-}
-
-fn rem(
-    self: *Self,
-    lhs_bind: ReadArg.Bind,
-    rhs_bind: ReadArg.Bind,
-    lhs_ty: Type,
-    rhs_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) InnerError!MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    switch (lhs_ty.zigTypeTag(zcu)) {
-        .float => return self.fail("TODO ARM binary operations on floats", .{}),
-        .vector => return self.fail("TODO ARM binary operations on vectors", .{}),
-        .int => {
-            assert(lhs_ty.eql(rhs_ty, zcu));
-            const int_info = lhs_ty.intInfo(zcu);
-            if (int_info.bits <= 32) {
-                switch (int_info.signedness) {
-                    .signed => {
-                        return self.fail("TODO ARM signed integer zcu", .{});
-                    },
-                    .unsigned => {
-                        const rhs_immediate = try rhs_bind.resolveToImmediate(self);
-
-                        if (rhs_immediate) |imm| {
-                            if (std.math.isPowerOfTwo(imm)) {
-                                const log2 = std.math.log2_int(u32, imm);
-
-                                var lhs_reg: Register = undefined;
-                                var dest_reg: Register = undefined;
-
-                                const read_args = [_]ReadArg{
-                                    .{ .ty = lhs_ty, .bind = lhs_bind, .class = gp, .reg = &lhs_reg },
-                                };
-                                const write_args = [_]WriteArg{
-                                    .{ .ty = lhs_ty, .bind = .none, .class = gp, .reg = &dest_reg },
-                                };
-                                try self.allocRegs(
-                                    &read_args,
-                                    &write_args,
-                                    if (maybe_inst) |inst| .{
-                                        .corresponding_inst = inst,
-                                        .operand_mapping = &.{0},
-                                    } else null,
-                                );
-
-                                try self.truncRegister(lhs_reg, dest_reg, int_info.signedness, log2);
-
-                                return MCValue{ .register = dest_reg };
-                            } else {
-                                return self.fail("TODO ARM integer zcu by constants", .{});
-                            }
-                        } else {
-                            return self.fail("TODO ARM integer zcu", .{});
-                        }
-                    },
-                }
-            } else {
-                return self.fail("TODO ARM integer division for integers > u32/i32", .{});
-            }
-        },
-        else => unreachable,
-    }
-}
-
-fn modulo(
-    self: *Self,
-    lhs_bind: ReadArg.Bind,
-    rhs_bind: ReadArg.Bind,
-    lhs_ty: Type,
-    rhs_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) InnerError!MCValue {
-    _ = lhs_bind;
-    _ = rhs_bind;
-    _ = rhs_ty;
-    _ = maybe_inst;
-
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    switch (lhs_ty.zigTypeTag(zcu)) {
-        .float => return self.fail("TODO ARM binary operations on floats", .{}),
-        .vector => return self.fail("TODO ARM binary operations on vectors", .{}),
-        .int => return self.fail("TODO ARM zcu", .{}),
-        else => unreachable,
-    }
-}
-
-fn wrappingArithmetic(
-    self: *Self,
-    tag: Air.Inst.Tag,
-    lhs_bind: ReadArg.Bind,
-    rhs_bind: ReadArg.Bind,
-    lhs_ty: Type,
-    rhs_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) InnerError!MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    switch (lhs_ty.zigTypeTag(zcu)) {
-        .vector => return self.fail("TODO ARM binary operations on vectors", .{}),
-        .int => {
-            const int_info = lhs_ty.intInfo(zcu);
-            if (int_info.bits <= 32) {
-                // Generate an add/sub/mul
-                const result: MCValue = switch (tag) {
-                    .add_wrap => try self.addSub(.add, lhs_bind, rhs_bind, lhs_ty, rhs_ty, maybe_inst),
-                    .sub_wrap => try self.addSub(.sub, lhs_bind, rhs_bind, lhs_ty, rhs_ty, maybe_inst),
-                    .mul_wrap => try self.mul(lhs_bind, rhs_bind, lhs_ty, rhs_ty, maybe_inst),
-                    else => unreachable,
-                };
-
-                // Truncate if necessary
-                const result_reg = result.register;
-                if (int_info.bits < 32) {
-                    try self.truncRegister(result_reg, result_reg, int_info.signedness, int_info.bits);
-                }
-
-                return result;
-            } else {
-                return self.fail("TODO ARM binary operations on integers > u32/i32", .{});
-            }
-        },
-        else => unreachable,
-    }
-}
-
-fn bitwise(
-    self: *Self,
-    tag: Air.Inst.Tag,
-    lhs_bind: ReadArg.Bind,
-    rhs_bind: ReadArg.Bind,
-    lhs_ty: Type,
-    rhs_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) InnerError!MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    switch (lhs_ty.zigTypeTag(zcu)) {
-        .vector => return self.fail("TODO ARM binary operations on vectors", .{}),
-        .int => {
-            assert(lhs_ty.eql(rhs_ty, zcu));
-            const int_info = lhs_ty.intInfo(zcu);
-            if (int_info.bits <= 32) {
-                const lhs_immediate = try lhs_bind.resolveToImmediate(self);
-                const rhs_immediate = try rhs_bind.resolveToImmediate(self);
-
-                const lhs_immediate_ok = if (lhs_immediate) |imm| Instruction.Operand.fromU32(imm) != null else false;
-                const rhs_immediate_ok = if (rhs_immediate) |imm| Instruction.Operand.fromU32(imm) != null else false;
-
-                const mir_tag: Mir.Inst.Tag = switch (tag) {
-                    .bit_and => .@"and",
-                    .bit_or => .orr,
-                    .xor => .eor,
-                    else => unreachable,
-                };
-
-                if (rhs_immediate_ok) {
-                    return try self.binOpImmediate(mir_tag, lhs_bind, rhs_immediate.?, lhs_ty, false, maybe_inst);
-                } else if (lhs_immediate_ok) {
-                    // swap lhs and rhs
-                    return try self.binOpImmediate(mir_tag, rhs_bind, lhs_immediate.?, rhs_ty, true, maybe_inst);
-                } else {
-                    return try self.binOpRegister(mir_tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, maybe_inst);
-                }
-            } else {
-                return self.fail("TODO ARM binary operations on integers > u32/i32", .{});
-            }
-        },
-        else => unreachable,
-    }
-}
-
-fn shiftExact(
-    self: *Self,
-    tag: Air.Inst.Tag,
-    lhs_bind: ReadArg.Bind,
-    rhs_bind: ReadArg.Bind,
-    lhs_ty: Type,
-    rhs_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) InnerError!MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    switch (lhs_ty.zigTypeTag(zcu)) {
-        .vector => if (!rhs_ty.isVector(zcu))
-            return self.fail("TODO ARM vector shift with scalar rhs", .{})
-        else
-            return self.fail("TODO ARM binary operations on vectors", .{}),
-        .int => {
-            const int_info = lhs_ty.intInfo(zcu);
-            if (int_info.bits <= 32) {
-                const rhs_immediate = try rhs_bind.resolveToImmediate(self);
-
-                const mir_tag: Mir.Inst.Tag = switch (tag) {
-                    .shl_exact => .lsl,
-                    .shr_exact => switch (lhs_ty.intInfo(zcu).signedness) {
-                        .signed => Mir.Inst.Tag.asr,
-                        .unsigned => Mir.Inst.Tag.lsr,
-                    },
-                    else => unreachable,
-                };
-
-                if (rhs_immediate) |imm| {
-                    return try self.binOpImmediate(mir_tag, lhs_bind, imm, lhs_ty, false, maybe_inst);
-                } else {
-                    return try self.binOpRegister(mir_tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, maybe_inst);
-                }
-            } else {
-                return self.fail("TODO ARM binary operations on integers > u32/i32", .{});
-            }
-        },
-        else => unreachable,
-    }
-}
-
-fn shiftNormal(
-    self: *Self,
-    tag: Air.Inst.Tag,
-    lhs_bind: ReadArg.Bind,
-    rhs_bind: ReadArg.Bind,
-    lhs_ty: Type,
-    rhs_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) InnerError!MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    switch (lhs_ty.zigTypeTag(zcu)) {
-        .vector => if (!rhs_ty.isVector(zcu))
-            return self.fail("TODO ARM vector shift with scalar rhs", .{})
-        else
-            return self.fail("TODO ARM binary operations on vectors", .{}),
-        .int => {
-            const int_info = lhs_ty.intInfo(zcu);
-            if (int_info.bits <= 32) {
-                // Generate a shl_exact/shr_exact
-                const result: MCValue = switch (tag) {
-                    .shl => try self.shiftExact(.shl_exact, lhs_bind, rhs_bind, lhs_ty, rhs_ty, maybe_inst),
-                    .shr => try self.shiftExact(.shr_exact, lhs_bind, rhs_bind, lhs_ty, rhs_ty, maybe_inst),
-                    else => unreachable,
-                };
-
-                // Truncate if necessary
-                switch (tag) {
-                    .shr => return result,
-                    .shl => {
-                        const result_reg = result.register;
-                        if (int_info.bits < 32) {
-                            try self.truncRegister(result_reg, result_reg, int_info.signedness, int_info.bits);
-                        }
-
-                        return result;
-                    },
-                    else => unreachable,
-                }
-            } else {
-                return self.fail("TODO ARM binary operations on integers > u32/i32", .{});
-            }
-        },
-        else => unreachable,
-    }
-}
-
-fn booleanOp(
-    self: *Self,
-    tag: Air.Inst.Tag,
-    lhs_bind: ReadArg.Bind,
-    rhs_bind: ReadArg.Bind,
-    lhs_ty: Type,
-    rhs_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) InnerError!MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    switch (lhs_ty.zigTypeTag(zcu)) {
-        .bool => {
-            const lhs_immediate = try lhs_bind.resolveToImmediate(self);
-            const rhs_immediate = try rhs_bind.resolveToImmediate(self);
-
-            const mir_tag: Mir.Inst.Tag = switch (tag) {
-                .bool_and => .@"and",
-                .bool_or => .orr,
-                else => unreachable,
-            };
-
-            if (rhs_immediate) |imm| {
-                return try self.binOpImmediate(mir_tag, lhs_bind, imm, lhs_ty, false, maybe_inst);
-            } else if (lhs_immediate) |imm| {
-                // swap lhs and rhs
-                return try self.binOpImmediate(mir_tag, rhs_bind, imm, rhs_ty, true, maybe_inst);
-            } else {
-                return try self.binOpRegister(mir_tag, lhs_bind, rhs_bind, lhs_ty, rhs_ty, maybe_inst);
-            }
-        },
-        else => unreachable,
-    }
-}
-
-fn ptrArithmetic(
-    self: *Self,
-    tag: Air.Inst.Tag,
-    lhs_bind: ReadArg.Bind,
-    rhs_bind: ReadArg.Bind,
-    lhs_ty: Type,
-    rhs_ty: Type,
-    maybe_inst: ?Air.Inst.Index,
-) InnerError!MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    switch (lhs_ty.zigTypeTag(zcu)) {
-        .pointer => {
-            assert(rhs_ty.eql(Type.usize, zcu));
-
-            const ptr_ty = lhs_ty;
-            const elem_ty = switch (ptr_ty.ptrSize(zcu)) {
-                .one => ptr_ty.childType(zcu).childType(zcu), // ptr to array, so get array element type
-                else => ptr_ty.childType(zcu),
-            };
-            const elem_size: u32 = @intCast(elem_ty.abiSize(zcu));
-
-            const base_tag: Air.Inst.Tag = switch (tag) {
-                .ptr_add => .add,
-                .ptr_sub => .sub,
-                else => unreachable,
-            };
-
-            if (elem_size == 1) {
-                return try self.addSub(base_tag, lhs_bind, rhs_bind, Type.usize, Type.usize, maybe_inst);
-            } else {
-                // convert the offset into a byte offset by
-                // multiplying it with elem_size
-                const imm_bind = ReadArg.Bind{ .mcv = .{ .immediate = elem_size } };
-
-                const offset = try self.mul(rhs_bind, imm_bind, Type.usize, Type.usize, null);
-                const offset_bind = ReadArg.Bind{ .mcv = offset };
-
-                const addr = try self.addSub(base_tag, lhs_bind, offset_bind, Type.usize, Type.usize, null);
-                return addr;
-            }
-        },
-        else => unreachable,
-    }
-}
-
-fn genLdrRegister(self: *Self, dest_reg: Register, addr_reg: Register, ty: Type) !void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const abi_size = ty.abiSize(zcu);
-
-    const tag: Mir.Inst.Tag = switch (abi_size) {
-        1 => if (ty.isSignedInt(zcu)) Mir.Inst.Tag.ldrsb else .ldrb,
-        2 => if (ty.isSignedInt(zcu)) Mir.Inst.Tag.ldrsh else .ldrh,
-        3, 4 => .ldr,
-        else => unreachable,
-    };
-
-    const rr_offset: Mir.Inst.Data = .{ .rr_offset = .{
-        .rt = dest_reg,
-        .rn = addr_reg,
-        .offset = .{ .offset = Instruction.Offset.none },
-    } };
-    const rr_extra_offset: Mir.Inst.Data = .{ .rr_extra_offset = .{
-        .rt = dest_reg,
-        .rn = addr_reg,
-        .offset = .{ .offset = Instruction.ExtraLoadStoreOffset.none },
-    } };
-
-    const data: Mir.Inst.Data = switch (abi_size) {
-        1 => if (ty.isSignedInt(zcu)) rr_extra_offset else rr_offset,
-        2 => rr_extra_offset,
-        3, 4 => rr_offset,
-        else => unreachable,
-    };
-
-    _ = try self.addInst(.{
-        .tag = tag,
-        .data = data,
-    });
-}
-
-fn genStrRegister(self: *Self, source_reg: Register, addr_reg: Register, ty: Type) !void {
-    const pt = self.pt;
-    const abi_size = ty.abiSize(pt.zcu);
-
-    const tag: Mir.Inst.Tag = switch (abi_size) {
-        1 => .strb,
-        2 => .strh,
-        4 => .str,
-        3 => return self.fail("TODO: genStrRegister for abi_size={}", .{abi_size}),
-        else => unreachable,
-    };
-
-    const rr_offset: Mir.Inst.Data = .{ .rr_offset = .{
-        .rt = source_reg,
-        .rn = addr_reg,
-        .offset = .{ .offset = Instruction.Offset.none },
-    } };
-    const rr_extra_offset: Mir.Inst.Data = .{ .rr_extra_offset = .{
-        .rt = source_reg,
-        .rn = addr_reg,
-        .offset = .{ .offset = Instruction.ExtraLoadStoreOffset.none },
-    } };
-
-    const data: Mir.Inst.Data = switch (abi_size) {
-        1, 4 => rr_offset,
-        2 => rr_extra_offset,
-        else => unreachable,
-    };
-
-    _ = try self.addInst(.{
-        .tag = tag,
-        .data = data,
-    });
-}
-
-fn genInlineMemcpy(
-    self: *Self,
-    src: Register,
-    dst: Register,
-    len: Register,
-    count: Register,
-    tmp: Register,
-) !void {
-    // mov count, #0
-    _ = try self.addInst(.{
-        .tag = .mov,
-        .data = .{ .r_op_mov = .{
-            .rd = count,
-            .op = Instruction.Operand.imm(0, 0),
-        } },
-    });
-
-    // loop:
-    // cmp count, len
-    _ = try self.addInst(.{
-        .tag = .cmp,
-        .data = .{ .r_op_cmp = .{
-            .rn = count,
-            .op = Instruction.Operand.reg(len, Instruction.Operand.Shift.none),
-        } },
-    });
-
-    // bge end
-    _ = try self.addInst(.{
-        .tag = .b,
-        .cond = .ge,
-        .data = .{ .inst = @intCast(self.mir_instructions.len + 5) },
-    });
-
-    // ldrb tmp, [src, count]
-    _ = try self.addInst(.{
-        .tag = .ldrb,
-        .data = .{ .rr_offset = .{
-            .rt = tmp,
-            .rn = src,
-            .offset = .{ .offset = Instruction.Offset.reg(count, .none) },
-        } },
-    });
-
-    // strb tmp, [src, count]
-    _ = try self.addInst(.{
-        .tag = .strb,
-        .data = .{ .rr_offset = .{
-            .rt = tmp,
-            .rn = dst,
-            .offset = .{ .offset = Instruction.Offset.reg(count, .none) },
-        } },
-    });
-
-    // add count, count, #1
-    _ = try self.addInst(.{
-        .tag = .add,
-        .data = .{ .rr_op = .{
-            .rd = count,
-            .rn = count,
-            .op = Instruction.Operand.imm(1, 0),
-        } },
-    });
-
-    // b loop
-    _ = try self.addInst(.{
-        .tag = .b,
-        .data = .{ .inst = @intCast(self.mir_instructions.len - 5) },
-    });
-
-    // end:
-}
-
-fn genInlineMemset(
-    self: *Self,
-    dst: MCValue,
-    val: MCValue,
-    len: MCValue,
-) !void {
-    const dst_reg = switch (dst) {
-        .register => |r| r,
-        else => try self.copyToTmpRegister(Type.manyptr_u8, dst),
-    };
-    const dst_reg_lock = self.register_manager.lockReg(dst_reg);
-    defer if (dst_reg_lock) |lock| self.register_manager.unlockReg(lock);
-
-    const val_reg = switch (val) {
-        .register => |r| r,
-        else => try self.copyToTmpRegister(Type.u8, val),
-    };
-    const val_reg_lock = self.register_manager.lockReg(val_reg);
-    defer if (val_reg_lock) |lock| self.register_manager.unlockReg(lock);
-
-    const len_reg = switch (len) {
-        .register => |r| r,
-        else => try self.copyToTmpRegister(Type.usize, len),
-    };
-    const len_reg_lock = self.register_manager.lockReg(len_reg);
-    defer if (len_reg_lock) |lock| self.register_manager.unlockReg(lock);
-
-    const count_reg = try self.register_manager.allocReg(null, gp);
-
-    try self.genInlineMemsetCode(dst_reg, val_reg, len_reg, count_reg);
-}
-
-fn genInlineMemsetCode(
-    self: *Self,
-    dst: Register,
-    val: Register,
-    len: Register,
-    count: Register,
-) !void {
-    // mov count, #0
-    _ = try self.addInst(.{
-        .tag = .mov,
-        .data = .{ .r_op_mov = .{
-            .rd = count,
-            .op = Instruction.Operand.imm(0, 0),
-        } },
-    });
-
-    // loop:
-    // cmp count, len
-    _ = try self.addInst(.{
-        .tag = .cmp,
-        .data = .{ .r_op_cmp = .{
-            .rn = count,
-            .op = Instruction.Operand.reg(len, Instruction.Operand.Shift.none),
-        } },
-    });
-
-    // bge end
-    _ = try self.addInst(.{
-        .tag = .b,
-        .cond = .ge,
-        .data = .{ .inst = @intCast(self.mir_instructions.len + 4) },
-    });
-
-    // strb val, [src, count]
-    _ = try self.addInst(.{
-        .tag = .strb,
-        .data = .{ .rr_offset = .{
-            .rt = val,
-            .rn = dst,
-            .offset = .{ .offset = Instruction.Offset.reg(count, .none) },
-        } },
-    });
-
-    // add count, count, #1
-    _ = try self.addInst(.{
-        .tag = .add,
-        .data = .{ .rr_op = .{
-            .rd = count,
-            .rn = count,
-            .op = Instruction.Operand.imm(1, 0),
-        } },
-    });
-
-    // b loop
-    _ = try self.addInst(.{
-        .tag = .b,
-        .data = .{ .inst = @intCast(self.mir_instructions.len - 4) },
-    });
-
-    // end:
-}
-
-fn airArg(self: *Self, inst: Air.Inst.Index) !void {
-    // skip zero-bit arguments as they don't have a corresponding arg instruction
-    var arg_index = self.arg_index;
-    while (self.args[arg_index] == .none) arg_index += 1;
-    self.arg_index = arg_index + 1;
-
-    const zcu = self.pt.zcu;
-    const func_zir = zcu.funcInfo(self.func_index).zir_body_inst.resolveFull(&zcu.intern_pool).?;
-    const file = zcu.fileByIndex(func_zir.file);
-    if (!file.mod.?.strip) {
-        const tag = self.air.instructions.items(.tag)[@intFromEnum(inst)];
-        const arg = self.air.instructions.items(.data)[@intFromEnum(inst)].arg;
-        const ty = self.typeOfIndex(inst);
-        const zir = &file.zir.?;
-        const name = zir.nullTerminatedString(zir.getParamName(zir.getParamBody(func_zir.inst)[arg.zir_param_index]).?);
-        try self.dbg_info_relocs.append(self.gpa, .{
-            .tag = tag,
-            .ty = ty,
-            .name = name,
-            .mcv = self.args[arg_index],
-        });
-    }
-
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else self.args[arg_index];
-    return self.finishAir(inst, result, .{ .none, .none, .none });
-}
-
-fn airTrap(self: *Self) !void {
-    _ = try self.addInst(.{
-        .tag = .undefined_instruction,
-        .data = .{ .nop = {} },
-    });
-    return self.finishAirBookkeeping();
-}
-
-fn airBreakpoint(self: *Self) !void {
-    _ = try self.addInst(.{
-        .tag = .bkpt,
-        .data = .{ .imm16 = 0 },
-    });
-    return self.finishAirBookkeeping();
-}
-
-fn airRetAddr(self: *Self, inst: Air.Inst.Index) !void {
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement airRetAddr for arm", .{});
-    return self.finishAir(inst, result, .{ .none, .none, .none });
-}
-
-fn airFrameAddress(self: *Self, inst: Air.Inst.Index) !void {
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement airFrameAddress for arm", .{});
-    return self.finishAir(inst, result, .{ .none, .none, .none });
-}
-
-fn airCall(self: *Self, inst: Air.Inst.Index, modifier: std.builtin.CallModifier) !void {
-    if (modifier == .always_tail) return self.fail("TODO implement tail calls for arm", .{});
-    const pl_op = self.air.instructions.items(.data)[@intFromEnum(inst)].pl_op;
-    const callee = pl_op.operand;
-    const extra = self.air.extraData(Air.Call, pl_op.payload);
-    const args: []const Air.Inst.Ref = @ptrCast(self.air.extra.items[extra.end..][0..extra.data.args_len]);
-    const ty = self.typeOf(callee);
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const ip = &zcu.intern_pool;
-
-    const fn_ty = switch (ty.zigTypeTag(zcu)) {
-        .@"fn" => ty,
-        .pointer => ty.childType(zcu),
-        else => unreachable,
-    };
-
-    var info = try self.resolveCallingConventionValues(fn_ty);
-    defer info.deinit(self);
-
-    // According to the Procedure Call Standard for the ARM
-    // Architecture, compare flags are not preserved across
-    // calls. Therefore, if some value is currently stored there, we
-    // need to save it.
-    try self.spillCompareFlagsIfOccupied();
-
-    // Save caller-saved registers, but crucially *after* we save the
-    // compare flags as saving compare flags may require a new
-    // caller-saved register
-    for (caller_preserved_regs) |reg| {
-        try self.register_manager.getReg(reg, null);
-    }
-
-    // If returning by reference, r0 will contain the address of where
-    // to put the result into. In that case, make sure that r0 remains
-    // untouched by the parameter passing code
-    const r0_lock: ?RegisterLock = if (info.return_value == .stack_offset) blk: {
-        log.debug("airCall: return by reference", .{});
-        const ret_ty = fn_ty.fnReturnType(zcu);
-        const ret_abi_size: u32 = @intCast(ret_ty.abiSize(zcu));
-        const ret_abi_align = ret_ty.abiAlignment(zcu);
-        const stack_offset = try self.allocMem(ret_abi_size, ret_abi_align, inst);
-
-        const ptr_ty = try pt.singleMutPtrType(ret_ty);
-        try self.register_manager.getReg(.r0, null);
-        try self.genSetReg(ptr_ty, .r0, .{ .ptr_stack_offset = stack_offset });
-
-        info.return_value = .{ .stack_offset = stack_offset };
-
-        break :blk self.register_manager.lockRegAssumeUnused(.r0);
-    } else null;
-    defer if (r0_lock) |reg| self.register_manager.unlockReg(reg);
-
-    // Make space for the arguments passed via the stack
-    self.max_end_stack += info.stack_byte_count;
-
-    for (info.args, 0..) |mc_arg, arg_i| {
-        const arg = args[arg_i];
-        const arg_ty = self.typeOf(arg);
-        const arg_mcv = try self.resolveInst(args[arg_i]);
-
-        switch (mc_arg) {
-            .none => continue,
-            .register => |reg| {
-                try self.register_manager.getReg(reg, null);
-                try self.genSetReg(arg_ty, reg, arg_mcv);
-            },
-            .stack_offset => unreachable,
-            .stack_argument_offset => |offset| try self.genSetStackArgument(
-                arg_ty,
-                offset,
-                arg_mcv,
-            ),
-            else => unreachable,
-        }
-    }
-
-    // Due to incremental compilation, how function calls are generated depends
-    // on linking.
-    if (try self.air.value(callee, pt)) |func_value| switch (ip.indexToKey(func_value.toIntern())) {
-        .func => {
-            return self.fail("TODO implement calling functions", .{});
-        },
-        .@"extern" => {
-            return self.fail("TODO implement calling extern functions", .{});
-        },
-        else => {
-            return self.fail("TODO implement calling bitcasted functions", .{});
-        },
-    } else {
-        assert(ty.zigTypeTag(zcu) == .pointer);
-        const mcv = try self.resolveInst(callee);
-
-        try self.genSetReg(Type.usize, .lr, mcv);
-    }
-
-    // TODO: add Instruction.supportedOn
-    // function for ARM
-    if (self.target.cpu.has(.arm, .has_v5t)) {
-        _ = try self.addInst(.{
-            .tag = .blx,
-            .data = .{ .reg = .lr },
-        });
-    } else {
-        return self.fail("TODO fix blx emulation for ARM <v5", .{});
-        // _ = try self.addInst(.{
-        //     .tag = .mov,
-        //     .data = .{ .rr_op = .{
-        //         .rd = .lr,
-        //         .rn = .r0,
-        //         .op = Instruction.Operand.reg(.pc, Instruction.Operand.Shift.none),
-        //     } },
-        // });
-        // _ = try self.addInst(.{
-        //     .tag = .bx,
-        //     .data = .{ .reg = .lr },
-        // });
-    }
-
-    const result: MCValue = result: {
-        switch (info.return_value) {
-            .register => |reg| {
-                if (RegisterManager.indexOfRegIntoTracked(reg) == null) {
-                    // Save function return value into a tracked register
-                    log.debug("airCall: copying {} as it is not tracked", .{reg});
-                    const new_reg = try self.copyToTmpRegister(fn_ty.fnReturnType(zcu), info.return_value);
-                    break :result MCValue{ .register = new_reg };
-                }
-            },
-            else => {},
-        }
-        break :result info.return_value;
-    };
-
-    if (args.len <= Air.Liveness.bpi - 2) {
-        var buf = [1]Air.Inst.Ref{.none} ** (Air.Liveness.bpi - 1);
-        buf[0] = callee;
-        @memcpy(buf[1..][0..args.len], args);
-        return self.finishAir(inst, result, buf);
-    }
-    var bt = try self.iterateBigTomb(inst, 1 + args.len);
-    bt.feed(callee);
-    for (args) |arg| {
-        bt.feed(arg);
-    }
-    return bt.finishAir(result);
-}
-
-fn airRet(self: *Self, inst: Air.Inst.Index) !void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const un_op = self.air.instructions.items(.data)[@intFromEnum(inst)].un_op;
-    const operand = try self.resolveInst(un_op);
-    const ret_ty = self.fn_type.fnReturnType(zcu);
-
-    switch (self.ret_mcv) {
-        .none => {},
-        .immediate => {
-            assert(ret_ty.isError(zcu));
-        },
-        .register => |reg| {
-            // Return result by value
-            try self.genSetReg(ret_ty, reg, operand);
-        },
-        .stack_offset => {
-            // Return result by reference
-            //
-            // self.ret_mcv is an address to where this function
-            // should store its result into
-            const ptr_ty = try pt.singleMutPtrType(ret_ty);
-            try self.store(self.ret_mcv, operand, ptr_ty, ret_ty);
-        },
-        else => unreachable, // invalid return result
-    }
-
-    // Just add space for an instruction, patch this later
-    try self.exitlude_jump_relocs.append(self.gpa, try self.addNop());
-
-    return self.finishAir(inst, .dead, .{ un_op, .none, .none });
-}
-
-fn airRetLoad(self: *Self, inst: Air.Inst.Index) !void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const un_op = self.air.instructions.items(.data)[@intFromEnum(inst)].un_op;
-    const ptr = try self.resolveInst(un_op);
-    const ptr_ty = self.typeOf(un_op);
-    const ret_ty = self.fn_type.fnReturnType(zcu);
-
-    switch (self.ret_mcv) {
-        .none => {},
-        .register => {
-            // Return result by value
-            try self.load(self.ret_mcv, ptr, ptr_ty);
-        },
-        .stack_offset => {
-            // Return result by reference
-            //
-            // self.ret_mcv is an address to where this function
-            // should store its result into
-            //
-            // If the operand is a ret_ptr instruction, we are done
-            // here. Else we need to load the result from the location
-            // pointed to by the operand and store it to the result
-            // location.
-            const op_inst = un_op.toIndex().?;
-            if (self.air.instructions.items(.tag)[@intFromEnum(op_inst)] != .ret_ptr) {
-                const abi_size: u32 = @intCast(ret_ty.abiSize(zcu));
-                const abi_align = ret_ty.abiAlignment(zcu);
-
-                const offset = try self.allocMem(abi_size, abi_align, null);
-
-                const tmp_mcv = MCValue{ .stack_offset = offset };
-                try self.load(tmp_mcv, ptr, ptr_ty);
-                try self.store(self.ret_mcv, tmp_mcv, ptr_ty, ret_ty);
-            }
-        },
-        else => unreachable, // invalid return result
-    }
-
-    // Just add space for an instruction, patch this later
-    try self.exitlude_jump_relocs.append(self.gpa, try self.addNop());
-
-    return self.finishAir(inst, .dead, .{ un_op, .none, .none });
-}
-
-fn airCmp(self: *Self, inst: Air.Inst.Index, op: math.CompareOperator) !void {
-    const bin_op = self.air.instructions.items(.data)[@intFromEnum(inst)].bin_op;
-    const lhs_ty = self.typeOf(bin_op.lhs);
-
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else blk: {
-        break :blk try self.cmp(.{ .inst = bin_op.lhs }, .{ .inst = bin_op.rhs }, lhs_ty, op);
-    };
-
-    return self.finishAir(inst, result, .{ bin_op.lhs, bin_op.rhs, .none });
-}
-
-fn cmp(
-    self: *Self,
-    lhs: ReadArg.Bind,
-    rhs: ReadArg.Bind,
-    lhs_ty: Type,
-    op: math.CompareOperator,
-) !MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const int_ty = switch (lhs_ty.zigTypeTag(zcu)) {
-        .optional => blk: {
-            const payload_ty = lhs_ty.optionalChild(zcu);
-            if (!payload_ty.hasRuntimeBitsIgnoreComptime(zcu)) {
-                break :blk Type.u1;
-            } else if (lhs_ty.isPtrLikeOptional(zcu)) {
-                break :blk Type.usize;
-            } else {
-                return self.fail("TODO ARM cmp non-pointer optionals", .{});
-            }
-        },
-        .float => return self.fail("TODO ARM cmp floats", .{}),
-        .@"enum" => lhs_ty.intTagType(zcu),
-        .int => lhs_ty,
-        .bool => Type.u1,
-        .pointer => Type.usize,
-        .error_set => Type.u16,
-        else => unreachable,
-    };
-
-    const int_info = int_ty.intInfo(zcu);
-    if (int_info.bits <= 32) {
-        try self.spillCompareFlagsIfOccupied();
-
-        var lhs_reg: Register = undefined;
-        var rhs_reg: Register = undefined;
-
-        const rhs_immediate = try rhs.resolveToImmediate(self);
-        const rhs_immediate_ok = if (rhs_immediate) |imm| Instruction.Operand.fromU32(imm) != null else false;
-
-        if (rhs_immediate_ok) {
-            const read_args = [_]ReadArg{
-                .{ .ty = int_ty, .bind = lhs, .class = gp, .reg = &lhs_reg },
-            };
-            try self.allocRegs(
-                &read_args,
-                &.{},
-                null, // we won't be able to reuse a register as there are no write_regs
-            );
-
-            _ = try self.addInst(.{
-                .tag = .cmp,
-                .data = .{ .r_op_cmp = .{
-                    .rn = lhs_reg,
-                    .op = Instruction.Operand.fromU32(rhs_immediate.?).?,
-                } },
-            });
-        } else {
-            const read_args = [_]ReadArg{
-                .{ .ty = int_ty, .bind = lhs, .class = gp, .reg = &lhs_reg },
-                .{ .ty = int_ty, .bind = rhs, .class = gp, .reg = &rhs_reg },
-            };
-            try self.allocRegs(
-                &read_args,
-                &.{},
-                null, // we won't be able to reuse a register as there are no write_regs
-            );
-
-            _ = try self.addInst(.{
-                .tag = .cmp,
-                .data = .{ .r_op_cmp = .{
-                    .rn = lhs_reg,
-                    .op = Instruction.Operand.reg(rhs_reg, Instruction.Operand.Shift.none),
-                } },
-            });
-        }
-
-        return switch (int_info.signedness) {
-            .signed => MCValue{ .cpsr_flags = Condition.fromCompareOperatorSigned(op) },
-            .unsigned => MCValue{ .cpsr_flags = Condition.fromCompareOperatorUnsigned(op) },
-        };
-    } else {
-        return self.fail("TODO ARM cmp for ints > 32 bits", .{});
-    }
-}
-
-fn airCmpVector(self: *Self, inst: Air.Inst.Index) !void {
-    _ = inst;
-    return self.fail("TODO implement airCmpVector for {}", .{self.target.cpu.arch});
-}
-
-fn airCmpLtErrorsLen(self: *Self, inst: Air.Inst.Index) !void {
-    const un_op = self.air.instructions.items(.data)[@intFromEnum(inst)].un_op;
-    const operand = try self.resolveInst(un_op);
-    _ = operand;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement airCmpLtErrorsLen for {}", .{self.target.cpu.arch});
-    return self.finishAir(inst, result, .{ un_op, .none, .none });
-}
-
-fn airDbgStmt(self: *Self, inst: Air.Inst.Index) !void {
-    const dbg_stmt = self.air.instructions.items(.data)[@intFromEnum(inst)].dbg_stmt;
-
-    _ = try self.addInst(.{
-        .tag = .dbg_line,
-        .cond = undefined,
-        .data = .{ .dbg_line_column = .{
-            .line = dbg_stmt.line,
-            .column = dbg_stmt.column,
-        } },
-    });
-
-    return self.finishAirBookkeeping();
-}
-
-fn airDbgInlineBlock(self: *Self, inst: Air.Inst.Index) !void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const ty_pl = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_pl;
-    const extra = self.air.extraData(Air.DbgInlineBlock, ty_pl.payload);
-    const func = zcu.funcInfo(extra.data.func);
-    // TODO emit debug info for function change
-    _ = func;
-    try self.lowerBlock(inst, @ptrCast(self.air.extra.items[extra.end..][0..extra.data.body_len]));
-}
-
-fn airDbgVar(self: *Self, inst: Air.Inst.Index) !void {
-    const pl_op = self.air.instructions.items(.data)[@intFromEnum(inst)].pl_op;
-    const operand = pl_op.operand;
-    const tag = self.air.instructions.items(.tag)[@intFromEnum(inst)];
-    const ty = self.typeOf(operand);
-    const mcv = try self.resolveInst(operand);
-    const name: Air.NullTerminatedString = @enumFromInt(pl_op.payload);
-
-    log.debug("airDbgVar: %{d}: {}, {}", .{ inst, ty.fmtDebug(), mcv });
-
-    try self.dbg_info_relocs.append(self.gpa, .{
-        .tag = tag,
-        .ty = ty,
-        .name = name.toSlice(self.air),
-        .mcv = mcv,
-    });
-
-    return self.finishAir(inst, .dead, .{ operand, .none, .none });
-}
-
-/// Given a boolean condition, emit a jump that is taken when that
-/// condition is false.
-fn condBr(self: *Self, condition: MCValue) !Mir.Inst.Index {
-    const condition_code: Condition = switch (condition) {
-        .cpsr_flags => |cond| cond.negate(),
-        else => blk: {
-            const reg = switch (condition) {
-                .register => |r| r,
-                else => try self.copyToTmpRegister(Type.bool, condition),
-            };
-
-            try self.spillCompareFlagsIfOccupied();
-
-            // cmp reg, 1
-            // bne ...
-            _ = try self.addInst(.{
-                .tag = .cmp,
-                .data = .{ .r_op_cmp = .{
-                    .rn = reg,
-                    .op = Instruction.Operand.imm(1, 0),
-                } },
-            });
-
-            break :blk .ne;
-        },
-    };
-
-    return try self.addInst(.{
-        .tag = .b,
-        .cond = condition_code,
-        .data = .{ .inst = undefined }, // populated later through performReloc
-    });
-}
-
-fn airCondBr(self: *Self, inst: Air.Inst.Index) !void {
-    const pl_op = self.air.instructions.items(.data)[@intFromEnum(inst)].pl_op;
-    const cond_inst = try self.resolveInst(pl_op.operand);
-    const extra = self.air.extraData(Air.CondBr, pl_op.payload);
-    const then_body: []const Air.Inst.Index = @ptrCast(self.air.extra.items[extra.end..][0..extra.data.then_body_len]);
-    const else_body: []const Air.Inst.Index = @ptrCast(self.air.extra.items[extra.end + then_body.len ..][0..extra.data.else_body_len]);
-    const liveness_condbr = self.liveness.getCondBr(inst);
-
-    const reloc: Mir.Inst.Index = try self.condBr(cond_inst);
-
-    // If the condition dies here in this condbr instruction, process
-    // that death now instead of later as this has an effect on
-    // whether it needs to be spilled in the branches
-    if (self.liveness.operandDies(inst, 0)) {
-        if (pl_op.operand.toIndex()) |op_index| {
-            self.processDeath(op_index);
-        }
-    }
-
-    // Capture the state of register and stack allocation state so that we can revert to it.
-    const parent_next_stack_offset = self.next_stack_offset;
-    const parent_free_registers = self.register_manager.free_registers;
-    var parent_stack = try self.stack.clone(self.gpa);
-    defer parent_stack.deinit(self.gpa);
-    const parent_registers = self.register_manager.registers;
-    const parent_cpsr_flags_inst = self.cpsr_flags_inst;
-
-    try self.branch_stack.append(.{});
-    errdefer {
-        _ = self.branch_stack.pop().?;
-    }
-
-    try self.ensureProcessDeathCapacity(liveness_condbr.then_deaths.len);
-    for (liveness_condbr.then_deaths) |operand| {
-        self.processDeath(operand);
-    }
-    try self.genBody(then_body);
-
-    // Revert to the previous register and stack allocation state.
-
-    var saved_then_branch = self.branch_stack.pop().?;
-    defer saved_then_branch.deinit(self.gpa);
-
-    self.register_manager.registers = parent_registers;
-    self.cpsr_flags_inst = parent_cpsr_flags_inst;
-
-    self.stack.deinit(self.gpa);
-    self.stack = parent_stack;
-    parent_stack = .{};
-
-    self.next_stack_offset = parent_next_stack_offset;
-    self.register_manager.free_registers = parent_free_registers;
-
-    try self.performReloc(reloc);
-    const else_branch = self.branch_stack.addOneAssumeCapacity();
-    else_branch.* = .{};
-
-    try self.ensureProcessDeathCapacity(liveness_condbr.else_deaths.len);
-    for (liveness_condbr.else_deaths) |operand| {
-        self.processDeath(operand);
-    }
-    try self.genBody(else_body);
-
-    // At this point, each branch will possibly have conflicting values for where
-    // each instruction is stored. They agree, however, on which instructions are alive/dead.
-    // We use the first ("then") branch as canonical, and here emit
-    // instructions into the second ("else") branch to make it conform.
-    // We continue respect the data structure semantic guarantees of the else_branch so
-    // that we can use all the code emitting abstractions. This is why at the bottom we
-    // assert that parent_branch.free_registers equals the saved_then_branch.free_registers
-    // rather than assigning it.
-    const parent_branch = &self.branch_stack.items[self.branch_stack.items.len - 2];
-    try parent_branch.inst_table.ensureUnusedCapacity(self.gpa, else_branch.inst_table.count());
-
-    const else_slice = else_branch.inst_table.entries.slice();
-    const else_keys = else_slice.items(.key);
-    const else_values = else_slice.items(.value);
-    for (else_keys, 0..) |else_key, else_idx| {
-        const else_value = else_values[else_idx];
-        const canon_mcv = if (saved_then_branch.inst_table.fetchSwapRemove(else_key)) |then_entry| blk: {
-            // The instruction's MCValue is overridden in both branches.
-            parent_branch.inst_table.putAssumeCapacity(else_key, then_entry.value);
-            if (else_value == .dead) {
-                assert(then_entry.value == .dead);
-                continue;
-            }
-            break :blk then_entry.value;
-        } else blk: {
-            if (else_value == .dead)
-                continue;
-            // The instruction is only overridden in the else branch.
-            var i: usize = self.branch_stack.items.len - 1;
-            while (true) {
-                i -= 1; // If this overflows, the question is: why wasn't the instruction marked dead?
-                if (self.branch_stack.items[i].inst_table.get(else_key)) |mcv| {
-                    assert(mcv != .dead);
-                    break :blk mcv;
-                }
-            }
-        };
-        log.debug("consolidating else_entry {d} {}=>{}", .{ else_key, else_value, canon_mcv });
-        // TODO make sure the destination stack offset / register does not already have something
-        // going on there.
-        try self.setRegOrMem(self.typeOfIndex(else_key), canon_mcv, else_value);
-        // TODO track the new register / stack allocation
-    }
-    try parent_branch.inst_table.ensureUnusedCapacity(self.gpa, saved_then_branch.inst_table.count());
-    const then_slice = saved_then_branch.inst_table.entries.slice();
-    const then_keys = then_slice.items(.key);
-    const then_values = then_slice.items(.value);
-    for (then_keys, 0..) |then_key, then_idx| {
-        const then_value = then_values[then_idx];
-        // We already deleted the items from this table that matched the else_branch.
-        // So these are all instructions that are only overridden in the then branch.
-        parent_branch.inst_table.putAssumeCapacity(then_key, then_value);
-        if (then_value == .dead)
-            continue;
-        const parent_mcv = blk: {
-            var i: usize = self.branch_stack.items.len - 1;
-            while (true) {
-                i -= 1;
-                if (self.branch_stack.items[i].inst_table.get(then_key)) |mcv| {
-                    assert(mcv != .dead);
-                    break :blk mcv;
-                }
-            }
-        };
-        log.debug("consolidating then_entry {d} {}=>{}", .{ then_key, parent_mcv, then_value });
-        // TODO make sure the destination stack offset / register does not already have something
-        // going on there.
-        try self.setRegOrMem(self.typeOfIndex(then_key), parent_mcv, then_value);
-        // TODO track the new register / stack allocation
-    }
-
-    {
-        var item = self.branch_stack.pop().?;
-        item.deinit(self.gpa);
-    }
-
-    // We already took care of pl_op.operand earlier, so we're going
-    // to pass .none here
-    return self.finishAir(inst, .unreach, .{ .none, .none, .none });
-}
-
-fn isNull(
-    self: *Self,
-    operand_bind: ReadArg.Bind,
-    operand_ty: Type,
-) !MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    if (operand_ty.isPtrLikeOptional(zcu)) {
-        assert(operand_ty.abiSize(zcu) == 4);
-
-        const imm_bind: ReadArg.Bind = .{ .mcv = .{ .immediate = 0 } };
-        return self.cmp(operand_bind, imm_bind, Type.usize, .eq);
-    } else {
-        return self.fail("TODO implement non-pointer optionals", .{});
-    }
-}
-
-fn isNonNull(
-    self: *Self,
-    operand_bind: ReadArg.Bind,
-    operand_ty: Type,
-) !MCValue {
-    const is_null_result = try self.isNull(operand_bind, operand_ty);
-    assert(is_null_result.cpsr_flags == .eq);
-
-    return MCValue{ .cpsr_flags = .ne };
-}
-
-fn airIsNull(self: *Self, inst: Air.Inst.Index) !void {
-    const un_op = self.air.instructions.items(.data)[@intFromEnum(inst)].un_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const operand_bind: ReadArg.Bind = .{ .inst = un_op };
-        const operand_ty = self.typeOf(un_op);
-
-        break :result try self.isNull(operand_bind, operand_ty);
-    };
-    return self.finishAir(inst, result, .{ un_op, .none, .none });
-}
-
-fn airIsNullPtr(self: *Self, inst: Air.Inst.Index) !void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const un_op = self.air.instructions.items(.data)[@intFromEnum(inst)].un_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const operand_ptr = try self.resolveInst(un_op);
-        const ptr_ty = self.typeOf(un_op);
-        const elem_ty = ptr_ty.childType(zcu);
-
-        const operand = try self.allocRegOrMem(elem_ty, true, null);
-        try self.load(operand, operand_ptr, ptr_ty);
-
-        break :result try self.isNull(.{ .mcv = operand }, elem_ty);
-    };
-    return self.finishAir(inst, result, .{ un_op, .none, .none });
-}
-
-fn airIsNonNull(self: *Self, inst: Air.Inst.Index) !void {
-    const un_op = self.air.instructions.items(.data)[@intFromEnum(inst)].un_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const operand_bind: ReadArg.Bind = .{ .inst = un_op };
-        const operand_ty = self.typeOf(un_op);
-
-        break :result try self.isNonNull(operand_bind, operand_ty);
-    };
-    return self.finishAir(inst, result, .{ un_op, .none, .none });
-}
-
-fn airIsNonNullPtr(self: *Self, inst: Air.Inst.Index) !void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const un_op = self.air.instructions.items(.data)[@intFromEnum(inst)].un_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const operand_ptr = try self.resolveInst(un_op);
-        const ptr_ty = self.typeOf(un_op);
-        const elem_ty = ptr_ty.childType(zcu);
-
-        const operand = try self.allocRegOrMem(elem_ty, true, null);
-        try self.load(operand, operand_ptr, ptr_ty);
-
-        break :result try self.isNonNull(.{ .mcv = operand }, elem_ty);
-    };
-    return self.finishAir(inst, result, .{ un_op, .none, .none });
-}
-
-fn isErr(
-    self: *Self,
-    error_union_bind: ReadArg.Bind,
-    error_union_ty: Type,
-) !MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const error_type = error_union_ty.errorUnionSet(zcu);
-
-    if (error_type.errorSetIsEmpty(zcu)) {
-        return MCValue{ .immediate = 0 }; // always false
-    }
-
-    const error_mcv = try self.errUnionErr(error_union_bind, error_union_ty, null);
-    return try self.cmp(.{ .mcv = error_mcv }, .{ .mcv = .{ .immediate = 0 } }, error_type, .gt);
-}
-
-fn isNonErr(
-    self: *Self,
-    error_union_bind: ReadArg.Bind,
-    error_union_ty: Type,
-) !MCValue {
-    const is_err_result = try self.isErr(error_union_bind, error_union_ty);
-    switch (is_err_result) {
-        .cpsr_flags => |cond| {
-            assert(cond == .hi);
-            return MCValue{ .cpsr_flags = cond.negate() };
-        },
-        .immediate => |imm| {
-            assert(imm == 0);
-            return MCValue{ .immediate = 1 };
-        },
-        else => unreachable,
-    }
-}
-
-fn airIsErr(self: *Self, inst: Air.Inst.Index) !void {
-    const un_op = self.air.instructions.items(.data)[@intFromEnum(inst)].un_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const error_union_bind: ReadArg.Bind = .{ .inst = un_op };
-        const error_union_ty = self.typeOf(un_op);
-
-        break :result try self.isErr(error_union_bind, error_union_ty);
-    };
-    return self.finishAir(inst, result, .{ un_op, .none, .none });
-}
-
-fn airIsErrPtr(self: *Self, inst: Air.Inst.Index) !void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const un_op = self.air.instructions.items(.data)[@intFromEnum(inst)].un_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const operand_ptr = try self.resolveInst(un_op);
-        const ptr_ty = self.typeOf(un_op);
-        const elem_ty = ptr_ty.childType(zcu);
-
-        const operand = try self.allocRegOrMem(elem_ty, true, null);
-        try self.load(operand, operand_ptr, ptr_ty);
-
-        break :result try self.isErr(.{ .mcv = operand }, elem_ty);
-    };
-    return self.finishAir(inst, result, .{ un_op, .none, .none });
-}
-
-fn airIsNonErr(self: *Self, inst: Air.Inst.Index) !void {
-    const un_op = self.air.instructions.items(.data)[@intFromEnum(inst)].un_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const error_union_bind: ReadArg.Bind = .{ .inst = un_op };
-        const error_union_ty = self.typeOf(un_op);
-
-        break :result try self.isNonErr(error_union_bind, error_union_ty);
-    };
-    return self.finishAir(inst, result, .{ un_op, .none, .none });
-}
-
-fn airIsNonErrPtr(self: *Self, inst: Air.Inst.Index) !void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const un_op = self.air.instructions.items(.data)[@intFromEnum(inst)].un_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const operand_ptr = try self.resolveInst(un_op);
-        const ptr_ty = self.typeOf(un_op);
-        const elem_ty = ptr_ty.childType(zcu);
-
-        const operand = try self.allocRegOrMem(elem_ty, true, null);
-        try self.load(operand, operand_ptr, ptr_ty);
-
-        break :result try self.isNonErr(.{ .mcv = operand }, elem_ty);
-    };
-    return self.finishAir(inst, result, .{ un_op, .none, .none });
-}
-
-fn airLoop(self: *Self, inst: Air.Inst.Index) !void {
-    // A loop is a setup to be able to jump back to the beginning.
-    const ty_pl = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_pl;
-    const loop = self.air.extraData(Air.Block, ty_pl.payload);
-    const body: []const Air.Inst.Index = @ptrCast(self.air.extra.items[loop.end..][0..loop.data.body_len]);
-    const start_index: Mir.Inst.Index = @intCast(self.mir_instructions.len);
-
-    try self.genBody(body);
-    try self.jump(start_index);
-
-    return self.finishAirBookkeeping();
-}
-
-/// Send control flow to `inst`.
-fn jump(self: *Self, inst: Mir.Inst.Index) !void {
-    _ = try self.addInst(.{
-        .tag = .b,
-        .data = .{ .inst = inst },
-    });
-}
-
-fn airBlock(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_pl = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_pl;
-    const extra = self.air.extraData(Air.Block, ty_pl.payload);
-    try self.lowerBlock(inst, @ptrCast(self.air.extra.items[extra.end..][0..extra.data.body_len]));
-}
-
-fn lowerBlock(self: *Self, inst: Air.Inst.Index, body: []const Air.Inst.Index) !void {
-    try self.blocks.putNoClobber(self.gpa, inst, .{
-        // A block is a setup to be able to jump to the end.
-        .relocs = .{},
-        // It also acts as a receptacle for break operands.
-        // Here we use `MCValue.none` to represent a null value so that the first
-        // break instruction will choose a MCValue for the block result and overwrite
-        // this field. Following break instructions will use that MCValue to put their
-        // block results.
-        .mcv = MCValue{ .none = {} },
-    });
-    defer self.blocks.getPtr(inst).?.relocs.deinit(self.gpa);
-
-    // TODO emit debug info lexical block
-    try self.genBody(body);
-
-    // relocations for `br` instructions
-    const relocs = &self.blocks.getPtr(inst).?.relocs;
-    if (relocs.items.len > 0 and relocs.items[relocs.items.len - 1] == self.mir_instructions.len - 1) {
-        // If the last Mir instruction is the last relocation (which
-        // would just jump one instruction further), it can be safely
-        // removed
-        self.mir_instructions.orderedRemove(relocs.pop().?);
-    }
-    for (relocs.items) |reloc| {
-        try self.performReloc(reloc);
-    }
-
-    const result = self.blocks.getPtr(inst).?.mcv;
-    return self.finishAir(inst, result, .{ .none, .none, .none });
-}
-
-fn airSwitch(self: *Self, inst: Air.Inst.Index) !void {
-    const switch_br = self.air.unwrapSwitch(inst);
-    const condition_ty = self.typeOf(switch_br.operand);
-    const liveness = try self.liveness.getSwitchBr(
-        self.gpa,
-        inst,
-        switch_br.cases_len + 1,
-    );
-    defer self.gpa.free(liveness.deaths);
-
-    var it = switch_br.iterateCases();
-    while (it.next()) |case| {
-        if (case.ranges.len > 0) return self.fail("TODO: switch with ranges", .{});
-        // For every item, we compare it to condition and branch into
-        // the prong if they are equal. After we compared to all
-        // items, we branch into the next prong (or if no other prongs
-        // exist out of the switch statement).
-        //
-        //             cmp condition, item1
-        //             beq prong
-        //             cmp condition, item2
-        //             beq prong
-        //             cmp condition, item3
-        //             beq prong
-        //             b out
-        // prong:      ...
-        //             ...
-        // out:        ...
-        const branch_into_prong_relocs = try self.gpa.alloc(u32, case.items.len);
-        defer self.gpa.free(branch_into_prong_relocs);
-
-        for (case.items, 0..) |item, idx| {
-            const cmp_result = try self.cmp(.{ .inst = switch_br.operand }, .{ .inst = item }, condition_ty, .neq);
-            branch_into_prong_relocs[idx] = try self.condBr(cmp_result);
-        }
-
-        const branch_away_from_prong_reloc = try self.addInst(.{
-            .tag = .b,
-            .data = .{ .inst = undefined }, // populated later through performReloc
-        });
-
-        for (branch_into_prong_relocs) |reloc| {
-            try self.performReloc(reloc);
-        }
-
-        // Capture the state of register and stack allocation state so that we can revert to it.
-        const parent_next_stack_offset = self.next_stack_offset;
-        const parent_free_registers = self.register_manager.free_registers;
-        const parent_cpsr_flags_inst = self.cpsr_flags_inst;
-        var parent_stack = try self.stack.clone(self.gpa);
-        defer parent_stack.deinit(self.gpa);
-        const parent_registers = self.register_manager.registers;
-
-        try self.branch_stack.append(.{});
-        errdefer {
-            _ = self.branch_stack.pop().?;
-        }
-
-        try self.ensureProcessDeathCapacity(liveness.deaths[case.idx].len);
-        for (liveness.deaths[case.idx]) |operand| {
-            self.processDeath(operand);
-        }
-        try self.genBody(case.body);
-
-        // Revert to the previous register and stack allocation state.
-        var saved_case_branch = self.branch_stack.pop().?;
-        defer saved_case_branch.deinit(self.gpa);
-
-        self.register_manager.registers = parent_registers;
-        self.cpsr_flags_inst = parent_cpsr_flags_inst;
-        self.stack.deinit(self.gpa);
-        self.stack = parent_stack;
-        parent_stack = .{};
-
-        self.next_stack_offset = parent_next_stack_offset;
-        self.register_manager.free_registers = parent_free_registers;
-
-        try self.performReloc(branch_away_from_prong_reloc);
-    }
-
-    if (switch_br.else_body_len > 0) {
-        const else_body = it.elseBody();
-
-        // Capture the state of register and stack allocation state so that we can revert to it.
-        const parent_next_stack_offset = self.next_stack_offset;
-        const parent_free_registers = self.register_manager.free_registers;
-        const parent_cpsr_flags_inst = self.cpsr_flags_inst;
-        var parent_stack = try self.stack.clone(self.gpa);
-        defer parent_stack.deinit(self.gpa);
-        const parent_registers = self.register_manager.registers;
-
-        try self.branch_stack.append(.{});
-        errdefer {
-            _ = self.branch_stack.pop().?;
-        }
-
-        const else_deaths = liveness.deaths.len - 1;
-        try self.ensureProcessDeathCapacity(liveness.deaths[else_deaths].len);
-        for (liveness.deaths[else_deaths]) |operand| {
-            self.processDeath(operand);
-        }
-        try self.genBody(else_body);
-
-        // Revert to the previous register and stack allocation state.
-        var saved_case_branch = self.branch_stack.pop().?;
-        defer saved_case_branch.deinit(self.gpa);
-
-        self.register_manager.registers = parent_registers;
-        self.cpsr_flags_inst = parent_cpsr_flags_inst;
-        self.stack.deinit(self.gpa);
-        self.stack = parent_stack;
-        parent_stack = .{};
-
-        self.next_stack_offset = parent_next_stack_offset;
-        self.register_manager.free_registers = parent_free_registers;
-
-        // TODO consolidate returned MCValues between prongs and else branch like we do
-        // in airCondBr.
-    }
-
-    return self.finishAir(inst, .unreach, .{ switch_br.operand, .none, .none });
-}
-
-fn performReloc(self: *Self, inst: Mir.Inst.Index) !void {
-    const tag = self.mir_instructions.items(.tag)[inst];
-    switch (tag) {
-        .b => self.mir_instructions.items(.data)[inst].inst = @intCast(self.mir_instructions.len),
-        else => unreachable,
-    }
-}
-
-fn airBr(self: *Self, inst: Air.Inst.Index) !void {
-    const branch = self.air.instructions.items(.data)[@intFromEnum(inst)].br;
-    try self.br(branch.block_inst, branch.operand);
-    return self.finishAir(inst, .dead, .{ branch.operand, .none, .none });
-}
-
-fn br(self: *Self, block: Air.Inst.Index, operand: Air.Inst.Ref) !void {
-    const zcu = self.pt.zcu;
-    const block_data = self.blocks.getPtr(block).?;
-
-    if (self.typeOf(operand).hasRuntimeBits(zcu)) {
-        const operand_mcv = try self.resolveInst(operand);
-        const block_mcv = block_data.mcv;
-        if (block_mcv == .none) {
-            block_data.mcv = switch (operand_mcv) {
-                .none, .dead, .unreach => unreachable,
-                .register, .stack_offset, .memory => operand_mcv,
-                .immediate, .stack_argument_offset, .cpsr_flags => blk: {
-                    const new_mcv = try self.allocRegOrMem(self.typeOfIndex(block), true, block);
-                    try self.setRegOrMem(self.typeOfIndex(block), new_mcv, operand_mcv);
-                    break :blk new_mcv;
-                },
-                else => return self.fail("TODO implement block_data.mcv = operand_mcv for {}", .{operand_mcv}),
-            };
-        } else {
-            try self.setRegOrMem(self.typeOfIndex(block), block_mcv, operand_mcv);
-        }
-    }
-    return self.brVoid(block);
-}
-
-fn brVoid(self: *Self, block: Air.Inst.Index) !void {
-    const block_data = self.blocks.getPtr(block).?;
-
-    // Emit a jump with a relocation. It will be patched up after the block ends.
-    try block_data.relocs.append(self.gpa, try self.addInst(.{
-        .tag = .b,
-        .data = .{ .inst = undefined }, // populated later through performReloc
-    }));
-}
-
-fn airAsm(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_pl = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_pl;
-    const extra = self.air.extraData(Air.Asm, ty_pl.payload);
-    const is_volatile = @as(u1, @truncate(extra.data.flags >> 31)) != 0;
-    const clobbers_len: u31 = @truncate(extra.data.flags);
-    var extra_i: usize = extra.end;
-    const outputs: []const Air.Inst.Ref = @ptrCast(self.air.extra.items[extra_i..][0..extra.data.outputs_len]);
-    extra_i += outputs.len;
-    const inputs: []const Air.Inst.Ref = @ptrCast(self.air.extra.items[extra_i..][0..extra.data.inputs_len]);
-    extra_i += inputs.len;
-
-    const dead = !is_volatile and self.liveness.isUnused(inst);
-    const result: MCValue = if (dead) .dead else result: {
-        if (outputs.len > 1) {
-            return self.fail("TODO implement codegen for asm with more than 1 output", .{});
-        }
-
-        const output_constraint: ?[]const u8 = for (outputs) |output| {
-            if (output != .none) {
-                return self.fail("TODO implement codegen for non-expr asm", .{});
-            }
-            const extra_bytes = std.mem.sliceAsBytes(self.air.extra.items[extra_i..]);
-            const constraint = std.mem.sliceTo(std.mem.sliceAsBytes(self.air.extra.items[extra_i..]), 0);
-            const name = std.mem.sliceTo(extra_bytes[constraint.len + 1 ..], 0);
-            // This equation accounts for the fact that even if we have exactly 4 bytes
-            // for the string, we still use the next u32 for the null terminator.
-            extra_i += (constraint.len + name.len + (2 + 3)) / 4;
-
-            break constraint;
-        } else null;
-
-        for (inputs) |input| {
-            const input_bytes = std.mem.sliceAsBytes(self.air.extra.items[extra_i..]);
-            const constraint = std.mem.sliceTo(input_bytes, 0);
-            const name = std.mem.sliceTo(input_bytes[constraint.len + 1 ..], 0);
-            // This equation accounts for the fact that even if we have exactly 4 bytes
-            // for the string, we still use the next u32 for the null terminator.
-            extra_i += (constraint.len + name.len + (2 + 3)) / 4;
-
-            if (constraint.len < 3 or constraint[0] != '{' or constraint[constraint.len - 1] != '}') {
-                return self.fail("unrecognized asm input constraint: '{s}'", .{constraint});
-            }
-            const reg_name = constraint[1 .. constraint.len - 1];
-            const reg = parseRegName(reg_name) orelse
-                return self.fail("unrecognized register: '{s}'", .{reg_name});
-
-            const arg_mcv = try self.resolveInst(input);
-            try self.register_manager.getReg(reg, null);
-            try self.genSetReg(self.typeOf(input), reg, arg_mcv);
-        }
-
-        {
-            var clobber_i: u32 = 0;
-            while (clobber_i < clobbers_len) : (clobber_i += 1) {
-                const clobber = std.mem.sliceTo(std.mem.sliceAsBytes(self.air.extra.items[extra_i..]), 0);
-                // This equation accounts for the fact that even if we have exactly 4 bytes
-                // for the string, we still use the next u32 for the null terminator.
-                extra_i += clobber.len / 4 + 1;
-
-                // TODO honor these
-            }
-        }
-
-        const asm_source = std.mem.sliceAsBytes(self.air.extra.items[extra_i..])[0..extra.data.source_len];
-
-        if (mem.eql(u8, asm_source, "svc #0")) {
-            _ = try self.addInst(.{
-                .tag = .svc,
-                .data = .{ .imm24 = 0 },
-            });
-        } else {
-            return self.fail("TODO implement support for more arm assembly instructions", .{});
-        }
-
-        if (output_constraint) |output| {
-            if (output.len < 4 or output[0] != '=' or output[1] != '{' or output[output.len - 1] != '}') {
-                return self.fail("unrecognized asm output constraint: '{s}'", .{output});
-            }
-            const reg_name = output[2 .. output.len - 1];
-            const reg = parseRegName(reg_name) orelse
-                return self.fail("unrecognized register: '{s}'", .{reg_name});
-
-            break :result MCValue{ .register = reg };
-        } else {
-            break :result MCValue{ .none = {} };
-        }
-    };
-
-    simple: {
-        var buf = [1]Air.Inst.Ref{.none} ** (Air.Liveness.bpi - 1);
-        var buf_index: usize = 0;
-        for (outputs) |output| {
-            if (output == .none) continue;
-
-            if (buf_index >= buf.len) break :simple;
-            buf[buf_index] = output;
-            buf_index += 1;
-        }
-        if (buf_index + inputs.len > buf.len) break :simple;
-        @memcpy(buf[buf_index..][0..inputs.len], inputs);
-        return self.finishAir(inst, result, buf);
-    }
-    var bt = try self.iterateBigTomb(inst, outputs.len + inputs.len);
-    for (outputs) |output| {
-        if (output == .none) continue;
-
-        bt.feed(output);
-    }
-    for (inputs) |input| {
-        bt.feed(input);
-    }
-    return bt.finishAir(result);
-}
-
-fn iterateBigTomb(self: *Self, inst: Air.Inst.Index, operand_count: usize) !BigTomb {
-    try self.ensureProcessDeathCapacity(operand_count + 1);
-    return BigTomb{
-        .function = self,
-        .inst = inst,
-        .lbt = self.liveness.iterateBigTomb(inst),
-    };
-}
-
-/// Sets the value without any modifications to register allocation metadata or stack allocation metadata.
-fn setRegOrMem(self: *Self, ty: Type, loc: MCValue, val: MCValue) !void {
-    switch (loc) {
-        .none => return,
-        .register => |reg| return self.genSetReg(ty, reg, val),
-        .stack_offset => |off| return self.genSetStack(ty, off, val),
-        .memory => {
-            return self.fail("TODO implement setRegOrMem for memory", .{});
-        },
-        else => unreachable,
-    }
-}
-
-fn genSetStack(self: *Self, ty: Type, stack_offset: u32, mcv: MCValue) InnerError!void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const abi_size: u32 = @intCast(ty.abiSize(zcu));
-    switch (mcv) {
-        .dead => unreachable,
-        .unreach, .none => return, // Nothing to do.
-        .undef => {
-            if (!self.wantSafety())
-                return; // The already existing value will do just fine.
-            // TODO Upgrade this to a memset call when we have that available.
-            switch (abi_size) {
-                1 => try self.genSetStack(ty, stack_offset, .{ .immediate = 0xaa }),
-                2 => try self.genSetStack(ty, stack_offset, .{ .immediate = 0xaaaa }),
-                4 => try self.genSetStack(ty, stack_offset, .{ .immediate = 0xaaaaaaaa }),
-                else => try self.genInlineMemset(
-                    .{ .ptr_stack_offset = stack_offset },
-                    .{ .immediate = 0xaa },
-                    .{ .immediate = abi_size },
-                ),
-            }
-        },
-        .cpsr_flags,
-        .immediate,
-        .ptr_stack_offset,
-        => {
-            const reg = try self.copyToTmpRegister(ty, mcv);
-            return self.genSetStack(ty, stack_offset, MCValue{ .register = reg });
-        },
-        .register => |reg| {
-            switch (abi_size) {
-                1, 4 => {
-                    const offset = if (math.cast(u12, stack_offset)) |imm| blk: {
-                        break :blk Instruction.Offset.imm(imm);
-                    } else Instruction.Offset.reg(try self.copyToTmpRegister(Type.u32, MCValue{ .immediate = stack_offset }), .none);
-
-                    const tag: Mir.Inst.Tag = switch (abi_size) {
-                        1 => .strb,
-                        4 => .str,
-                        else => unreachable,
-                    };
-
-                    _ = try self.addInst(.{
-                        .tag = tag,
-                        .data = .{ .rr_offset = .{
-                            .rt = reg,
-                            .rn = .fp,
-                            .offset = .{
-                                .offset = offset,
-                                .positive = false,
-                            },
-                        } },
-                    });
-                },
-                2 => {
-                    const offset = if (stack_offset <= math.maxInt(u8)) blk: {
-                        break :blk Instruction.ExtraLoadStoreOffset.imm(@intCast(stack_offset));
-                    } else Instruction.ExtraLoadStoreOffset.reg(try self.copyToTmpRegister(Type.u32, MCValue{ .immediate = stack_offset }));
-
-                    _ = try self.addInst(.{
-                        .tag = .strh,
-                        .data = .{ .rr_extra_offset = .{
-                            .rt = reg,
-                            .rn = .fp,
-                            .offset = .{
-                                .offset = offset,
-                                .positive = false,
-                            },
-                        } },
-                    });
-                },
-                else => return self.fail("TODO implement storing other types abi_size={}", .{abi_size}),
-            }
-        },
-        .register_c_flag,
-        .register_v_flag,
-        => |reg| {
-            const reg_lock = self.register_manager.lockReg(reg);
-            defer if (reg_lock) |locked_reg| self.register_manager.unlockReg(locked_reg);
-
-            const wrapped_ty = ty.fieldType(0, zcu);
-            try self.genSetStack(wrapped_ty, stack_offset, .{ .register = reg });
-
-            const overflow_bit_ty = ty.fieldType(1, zcu);
-            const overflow_bit_offset: u32 = @intCast(ty.structFieldOffset(1, zcu));
-            const cond_reg = try self.register_manager.allocReg(null, gp);
-
-            // C flag: movcs reg, #1
-            // V flag: movvs reg, #1
-            _ = try self.addInst(.{
-                .tag = .mov,
-                .cond = switch (mcv) {
-                    .register_c_flag => .cs,
-                    .register_v_flag => .vs,
-                    else => unreachable,
-                },
-                .data = .{ .r_op_mov = .{
-                    .rd = cond_reg,
-                    .op = Instruction.Operand.fromU32(1).?,
-                } },
-            });
-
-            try self.genSetStack(overflow_bit_ty, stack_offset - overflow_bit_offset, .{
-                .register = cond_reg,
-            });
-        },
-        .memory,
-        .stack_argument_offset,
-        .stack_offset,
-        => {
-            switch (mcv) {
-                .stack_offset => |off| {
-                    if (stack_offset == off)
-                        return; // Copy stack variable to itself; nothing to do.
-                },
-                else => {},
-            }
-
-            if (abi_size <= 4) {
-                const reg = try self.copyToTmpRegister(ty, mcv);
-                return self.genSetStack(ty, stack_offset, MCValue{ .register = reg });
-            } else {
-                const ptr_ty = try pt.singleMutPtrType(ty);
-
-                // TODO call extern memcpy
-                const regs = try self.register_manager.allocRegs(5, .{ null, null, null, null, null }, gp);
-                const src_reg = regs[0];
-                const dst_reg = regs[1];
-                const len_reg = regs[2];
-                const count_reg = regs[3];
-                const tmp_reg = regs[4];
-
-                switch (mcv) {
-                    .stack_offset => |off| {
-                        // sub src_reg, fp, #off
-                        try self.genSetReg(ptr_ty, src_reg, .{ .ptr_stack_offset = off });
-                    },
-                    .memory => |addr| try self.genSetReg(ptr_ty, src_reg, .{ .immediate = @intCast(addr) }),
-                    .stack_argument_offset => |off| {
-                        _ = try self.addInst(.{
-                            .tag = .ldr_ptr_stack_argument,
-                            .data = .{ .r_stack_offset = .{
-                                .rt = src_reg,
-                                .stack_offset = off,
-                            } },
-                        });
-                    },
-                    else => unreachable,
-                }
-
-                // sub dst_reg, fp, #stack_offset
-                try self.genSetReg(ptr_ty, dst_reg, .{ .ptr_stack_offset = stack_offset });
-
-                // mov len, #abi_size
-                try self.genSetReg(Type.usize, len_reg, .{ .immediate = abi_size });
-
-                // memcpy(src, dst, len)
-                try self.genInlineMemcpy(src_reg, dst_reg, len_reg, count_reg, tmp_reg);
-            }
-        },
-    }
-}
-
-fn genSetReg(self: *Self, ty: Type, reg: Register, mcv: MCValue) InnerError!void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    switch (mcv) {
-        .dead => unreachable,
-        .unreach, .none => return, // Nothing to do.
-        .undef => {
-            if (!self.wantSafety())
-                return; // The already existing value will do just fine.
-            // Write the debug undefined value.
-            return self.genSetReg(ty, reg, .{ .immediate = 0xaaaaaaaa });
-        },
-        .ptr_stack_offset => |off| {
-            // TODO: maybe addressing from sp instead of fp
-            const op = Instruction.Operand.fromU32(off) orelse
-                return self.fail("TODO larger stack offsets", .{});
-
-            _ = try self.addInst(.{
-                .tag = .sub,
-                .data = .{ .rr_op = .{
-                    .rd = reg,
-                    .rn = .fp,
-                    .op = op,
-                } },
-            });
-        },
-        .cpsr_flags => |condition| {
-            const zero = Instruction.Operand.imm(0, 0);
-            const one = Instruction.Operand.imm(1, 0);
-
-            // mov reg, 0
-            _ = try self.addInst(.{
-                .tag = .mov,
-                .data = .{ .r_op_mov = .{
-                    .rd = reg,
-                    .op = zero,
-                } },
-            });
-
-            // moveq reg, 1
-            _ = try self.addInst(.{
-                .tag = .mov,
-                .cond = condition,
-                .data = .{ .r_op_mov = .{
-                    .rd = reg,
-                    .op = one,
-                } },
-            });
-        },
-        .immediate => |x| {
-            if (Instruction.Operand.fromU32(x)) |op| {
-                _ = try self.addInst(.{
-                    .tag = .mov,
-                    .data = .{ .r_op_mov = .{
-                        .rd = reg,
-                        .op = op,
-                    } },
-                });
-            } else if (Instruction.Operand.fromU32(~x)) |op| {
-                _ = try self.addInst(.{
-                    .tag = .mvn,
-                    .data = .{ .r_op_mov = .{
-                        .rd = reg,
-                        .op = op,
-                    } },
-                });
-            } else if (x <= math.maxInt(u16)) {
-                if (self.target.cpu.has(.arm, .has_v7)) {
-                    _ = try self.addInst(.{
-                        .tag = .movw,
-                        .data = .{ .r_imm16 = .{
-                            .rd = reg,
-                            .imm16 = @intCast(x),
-                        } },
-                    });
-                } else {
-                    _ = try self.addInst(.{
-                        .tag = .mov,
-                        .data = .{ .r_op_mov = .{
-                            .rd = reg,
-                            .op = Instruction.Operand.imm(@truncate(x), 0),
-                        } },
-                    });
-                    _ = try self.addInst(.{
-                        .tag = .orr,
-                        .data = .{ .rr_op = .{
-                            .rd = reg,
-                            .rn = reg,
-                            .op = Instruction.Operand.imm(@truncate(x >> 8), 12),
-                        } },
-                    });
-                }
-            } else {
-                // TODO write constant to code and load
-                // relative to pc
-                if (self.target.cpu.has(.arm, .has_v7)) {
-                    // immediate: 0xaaaabbbb
-                    // movw reg, #0xbbbb
-                    // movt reg, #0xaaaa
-                    _ = try self.addInst(.{
-                        .tag = .movw,
-                        .data = .{ .r_imm16 = .{
-                            .rd = reg,
-                            .imm16 = @truncate(x),
-                        } },
-                    });
-                    _ = try self.addInst(.{
-                        .tag = .movt,
-                        .data = .{ .r_imm16 = .{
-                            .rd = reg,
-                            .imm16 = @truncate(x >> 16),
-                        } },
-                    });
-                } else {
-                    // immediate: 0xaabbccdd
-                    // mov reg, #0xaa
-                    // orr reg, reg, #0xbb, 24
-                    // orr reg, reg, #0xcc, 16
-                    // orr reg, reg, #0xdd, 8
-                    _ = try self.addInst(.{
-                        .tag = .mov,
-                        .data = .{ .r_op_mov = .{
-                            .rd = reg,
-                            .op = Instruction.Operand.imm(@truncate(x), 0),
-                        } },
-                    });
-                    _ = try self.addInst(.{
-                        .tag = .orr,
-                        .data = .{ .rr_op = .{
-                            .rd = reg,
-                            .rn = reg,
-                            .op = Instruction.Operand.imm(@truncate(x >> 8), 12),
-                        } },
-                    });
-                    _ = try self.addInst(.{
-                        .tag = .orr,
-                        .data = .{ .rr_op = .{
-                            .rd = reg,
-                            .rn = reg,
-                            .op = Instruction.Operand.imm(@truncate(x >> 16), 8),
-                        } },
-                    });
-                    _ = try self.addInst(.{
-                        .tag = .orr,
-                        .data = .{ .rr_op = .{
-                            .rd = reg,
-                            .rn = reg,
-                            .op = Instruction.Operand.imm(@truncate(x >> 24), 4),
-                        } },
-                    });
-                }
-            }
-        },
-        .register => |src_reg| {
-            // If the registers are the same, nothing to do.
-            if (src_reg.id() == reg.id())
-                return;
-
-            // mov reg, src_reg
-            _ = try self.addInst(.{
-                .tag = .mov,
-                .data = .{ .r_op_mov = .{
-                    .rd = reg,
-                    .op = Instruction.Operand.reg(src_reg, Instruction.Operand.Shift.none),
-                } },
-            });
-        },
-        .register_c_flag => unreachable, // doesn't fit into a register
-        .register_v_flag => unreachable, // doesn't fit into a register
-        .memory => |addr| {
-            // The value is in memory at a hard-coded address.
-            // If the type is a pointer, it means the pointer address is at this memory location.
-            try self.genSetReg(ty, reg, .{ .immediate = @intCast(addr) });
-            try self.genLdrRegister(reg, reg, ty);
-        },
-        .stack_offset => |off| {
-            // TODO: maybe addressing from sp instead of fp
-            const abi_size: u32 = @intCast(ty.abiSize(zcu));
-
-            const tag: Mir.Inst.Tag = switch (abi_size) {
-                1 => if (ty.isSignedInt(zcu)) Mir.Inst.Tag.ldrsb else .ldrb,
-                2 => if (ty.isSignedInt(zcu)) Mir.Inst.Tag.ldrsh else .ldrh,
-                3, 4 => .ldr,
-                else => unreachable,
-            };
-
-            const extra_offset = switch (abi_size) {
-                1 => ty.isSignedInt(zcu),
-                2 => true,
-                3, 4 => false,
-                else => unreachable,
-            };
-
-            if (extra_offset) {
-                const offset = if (off <= math.maxInt(u8)) blk: {
-                    break :blk Instruction.ExtraLoadStoreOffset.imm(@intCast(off));
-                } else Instruction.ExtraLoadStoreOffset.reg(try self.copyToTmpRegister(Type.usize, MCValue{ .immediate = off }));
-
-                _ = try self.addInst(.{
-                    .tag = tag,
-                    .data = .{ .rr_extra_offset = .{
-                        .rt = reg,
-                        .rn = .fp,
-                        .offset = .{
-                            .offset = offset,
-                            .positive = false,
-                        },
-                    } },
-                });
-            } else {
-                const offset = if (off <= math.maxInt(u12)) blk: {
-                    break :blk Instruction.Offset.imm(@intCast(off));
-                } else Instruction.Offset.reg(try self.copyToTmpRegister(Type.usize, MCValue{ .immediate = off }), .none);
-
-                _ = try self.addInst(.{
-                    .tag = tag,
-                    .data = .{ .rr_offset = .{
-                        .rt = reg,
-                        .rn = .fp,
-                        .offset = .{
-                            .offset = offset,
-                            .positive = false,
-                        },
-                    } },
-                });
-            }
-        },
-        .stack_argument_offset => |off| {
-            const abi_size = ty.abiSize(zcu);
-
-            const tag: Mir.Inst.Tag = switch (abi_size) {
-                1 => if (ty.isSignedInt(zcu)) Mir.Inst.Tag.ldrsb_stack_argument else .ldrb_stack_argument,
-                2 => if (ty.isSignedInt(zcu)) Mir.Inst.Tag.ldrsh_stack_argument else .ldrh_stack_argument,
-                3, 4 => .ldr_stack_argument,
-                else => unreachable,
-            };
-
-            _ = try self.addInst(.{
-                .tag = tag,
-                .data = .{ .r_stack_offset = .{
-                    .rt = reg,
-                    .stack_offset = off,
-                } },
-            });
-        },
-    }
-}
-
-fn genSetStackArgument(self: *Self, ty: Type, stack_offset: u32, mcv: MCValue) InnerError!void {
-    const pt = self.pt;
-    const abi_size: u32 = @intCast(ty.abiSize(pt.zcu));
-    switch (mcv) {
-        .dead => unreachable,
-        .none, .unreach => return,
-        .undef => {
-            if (!self.wantSafety())
-                return; // The already existing value will do just fine.
-            // TODO Upgrade this to a memset call when we have that available.
-            switch (abi_size) {
-                1 => try self.genSetStackArgument(ty, stack_offset, .{ .immediate = 0xaa }),
-                2 => try self.genSetStackArgument(ty, stack_offset, .{ .immediate = 0xaaaa }),
-                4 => try self.genSetStackArgument(ty, stack_offset, .{ .immediate = 0xaaaaaaaa }),
-                else => return self.fail("TODO implement memset", .{}),
-            }
-        },
-        .register => |reg| {
-            switch (abi_size) {
-                1, 4 => {
-                    const offset = if (math.cast(u12, stack_offset)) |imm| blk: {
-                        break :blk Instruction.Offset.imm(imm);
-                    } else Instruction.Offset.reg(try self.copyToTmpRegister(Type.u32, MCValue{ .immediate = stack_offset }), .none);
-
-                    const tag: Mir.Inst.Tag = switch (abi_size) {
-                        1 => .strb,
-                        4 => .str,
-                        else => unreachable,
-                    };
-
-                    _ = try self.addInst(.{
-                        .tag = tag,
-                        .data = .{ .rr_offset = .{
-                            .rt = reg,
-                            .rn = .sp,
-                            .offset = .{ .offset = offset },
-                        } },
-                    });
-                },
-                2 => {
-                    const offset = if (stack_offset <= math.maxInt(u8)) blk: {
-                        break :blk Instruction.ExtraLoadStoreOffset.imm(@intCast(stack_offset));
-                    } else Instruction.ExtraLoadStoreOffset.reg(try self.copyToTmpRegister(Type.u32, MCValue{ .immediate = stack_offset }));
-
-                    _ = try self.addInst(.{
-                        .tag = .strh,
-                        .data = .{ .rr_extra_offset = .{
-                            .rt = reg,
-                            .rn = .sp,
-                            .offset = .{ .offset = offset },
-                        } },
-                    });
-                },
-                else => return self.fail("TODO implement storing other types abi_size={}", .{abi_size}),
-            }
-        },
-        .register_c_flag,
-        .register_v_flag,
-        => {
-            return self.fail("TODO implement genSetStack {}", .{mcv});
-        },
-        .stack_offset,
-        .memory,
-        .stack_argument_offset,
-        => {
-            if (abi_size <= 4) {
-                const reg = try self.copyToTmpRegister(ty, mcv);
-                return self.genSetStackArgument(ty, stack_offset, MCValue{ .register = reg });
-            } else {
-                const ptr_ty = try pt.singleMutPtrType(ty);
-
-                // TODO call extern memcpy
-                const regs = try self.register_manager.allocRegs(5, .{ null, null, null, null, null }, gp);
-                const src_reg = regs[0];
-                const dst_reg = regs[1];
-                const len_reg = regs[2];
-                const count_reg = regs[3];
-                const tmp_reg = regs[4];
-
-                switch (mcv) {
-                    .stack_offset => |off| {
-                        // sub src_reg, fp, #off
-                        try self.genSetReg(ptr_ty, src_reg, .{ .ptr_stack_offset = off });
-                    },
-                    .memory => |addr| try self.genSetReg(ptr_ty, src_reg, .{ .immediate = @intCast(addr) }),
-                    .stack_argument_offset => |off| {
-                        _ = try self.addInst(.{
-                            .tag = .ldr_ptr_stack_argument,
-                            .data = .{ .r_stack_offset = .{
-                                .rt = src_reg,
-                                .stack_offset = off,
-                            } },
-                        });
-                    },
-                    else => unreachable,
-                }
-
-                // add dst_reg, sp, #stack_offset
-                const dst_offset_op: Instruction.Operand = if (Instruction.Operand.fromU32(stack_offset)) |x| x else {
-                    return self.fail("TODO load: set reg to stack offset with all possible offsets", .{});
-                };
-                _ = try self.addInst(.{
-                    .tag = .add,
-                    .data = .{ .rr_op = .{
-                        .rd = dst_reg,
-                        .rn = .sp,
-                        .op = dst_offset_op,
-                    } },
-                });
-
-                // mov len, #abi_size
-                try self.genSetReg(Type.usize, len_reg, .{ .immediate = abi_size });
-
-                // memcpy(src, dst, len)
-                try self.genInlineMemcpy(src_reg, dst_reg, len_reg, count_reg, tmp_reg);
-            }
-        },
-        .cpsr_flags,
-        .immediate,
-        .ptr_stack_offset,
-        => {
-            const reg = try self.copyToTmpRegister(ty, mcv);
-            return self.genSetStackArgument(ty, stack_offset, MCValue{ .register = reg });
-        },
-    }
-}
-
-fn airBitCast(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result = if (self.liveness.isUnused(inst)) .dead else result: {
-        const operand = try self.resolveInst(ty_op.operand);
-        if (self.reuseOperand(inst, ty_op.operand, 0, operand)) break :result operand;
-
-        const operand_lock = switch (operand) {
-            .register,
-            .register_c_flag,
-            .register_v_flag,
-            => |reg| self.register_manager.lockReg(reg),
-            else => null,
-        };
-        defer if (operand_lock) |lock| self.register_manager.unlockReg(lock);
-
-        const dest_ty = self.typeOfIndex(inst);
-        const dest = try self.allocRegOrMem(dest_ty, true, inst);
-        try self.setRegOrMem(dest_ty, dest, operand);
-        break :result dest;
-    };
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airArrayToSlice(self: *Self, inst: Air.Inst.Index) !void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
-        const ptr_ty = self.typeOf(ty_op.operand);
-        const ptr = try self.resolveInst(ty_op.operand);
-        const array_ty = ptr_ty.childType(zcu);
-        const array_len: u32 = @intCast(array_ty.arrayLen(zcu));
-
-        const stack_offset = try self.allocMem(8, .@"8", inst);
-        try self.genSetStack(ptr_ty, stack_offset, ptr);
-        try self.genSetStack(Type.usize, stack_offset - 4, .{ .immediate = array_len });
-        break :result MCValue{ .stack_offset = stack_offset };
-    };
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airFloatFromInt(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement airFloatFromInt for {}", .{
-        self.target.cpu.arch,
-    });
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airIntFromFloat(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement airIntFromFloat for {}", .{
-        self.target.cpu.arch,
-    });
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airCmpxchg(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_pl = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_pl;
-    const extra = self.air.extraData(Air.Block, ty_pl.payload);
-    _ = extra;
-
-    return self.fail("TODO implement airCmpxchg for {}", .{
-        self.target.cpu.arch,
-    });
-}
-
-fn airAtomicRmw(self: *Self, inst: Air.Inst.Index) !void {
-    _ = inst;
-    return self.fail("TODO implement airCmpxchg for {}", .{self.target.cpu.arch});
-}
-
-fn airAtomicLoad(self: *Self, inst: Air.Inst.Index) !void {
-    _ = inst;
-    return self.fail("TODO implement airAtomicLoad for {}", .{self.target.cpu.arch});
-}
-
-fn airAtomicStore(self: *Self, inst: Air.Inst.Index, order: std.builtin.AtomicOrder) !void {
-    _ = inst;
-    _ = order;
-    return self.fail("TODO implement airAtomicStore for {}", .{self.target.cpu.arch});
-}
-
-fn airMemset(self: *Self, inst: Air.Inst.Index, safety: bool) !void {
-    if (safety) {
-        // TODO if the value is undef, write 0xaa bytes to dest
-    } else {
-        // TODO if the value is undef, don't lower this instruction
-    }
-    _ = inst;
-    return self.fail("TODO implement airMemset for {}", .{self.target.cpu.arch});
-}
-
-fn airMemcpy(self: *Self, inst: Air.Inst.Index) !void {
-    _ = inst;
-    return self.fail("TODO implement airMemcpy for {}", .{self.target.cpu.arch});
-}
-
-fn airMemmove(self: *Self, inst: Air.Inst.Index) !void {
-    _ = inst;
-    return self.fail("TODO implement airMemmove for {}", .{self.target.cpu.arch});
-}
-
-fn airTagName(self: *Self, inst: Air.Inst.Index) !void {
-    const un_op = self.air.instructions.items(.data)[@intFromEnum(inst)].un_op;
-    const operand = try self.resolveInst(un_op);
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else {
-        _ = operand;
-        return self.fail("TODO implement airTagName for arm", .{});
-    };
-    return self.finishAir(inst, result, .{ un_op, .none, .none });
-}
-
-fn airErrorName(self: *Self, inst: Air.Inst.Index) !void {
-    const un_op = self.air.instructions.items(.data)[@intFromEnum(inst)].un_op;
-    const operand = try self.resolveInst(un_op);
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else {
-        _ = operand;
-        return self.fail("TODO implement airErrorName for arm", .{});
-    };
-    return self.finishAir(inst, result, .{ un_op, .none, .none });
-}
-
-fn airSplat(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_op = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement airSplat for arm", .{});
-    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
-}
-
-fn airSelect(self: *Self, inst: Air.Inst.Index) !void {
-    const pl_op = self.air.instructions.items(.data)[@intFromEnum(inst)].pl_op;
-    const extra = self.air.extraData(Air.Bin, pl_op.payload).data;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement airSelect for arm", .{});
-    return self.finishAir(inst, result, .{ pl_op.operand, extra.lhs, extra.rhs });
-}
-
-fn airShuffleOne(self: *Self, inst: Air.Inst.Index) !void {
-    _ = inst;
-    return self.fail("TODO implement airShuffleOne for arm", .{});
-}
-
-fn airShuffleTwo(self: *Self, inst: Air.Inst.Index) !void {
-    _ = inst;
-    return self.fail("TODO implement airShuffleTwo for arm", .{});
-}
-
-fn airReduce(self: *Self, inst: Air.Inst.Index) !void {
-    const reduce = self.air.instructions.items(.data)[@intFromEnum(inst)].reduce;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement airReduce for arm", .{});
-    return self.finishAir(inst, result, .{ reduce.operand, .none, .none });
-}
-
-fn airAggregateInit(self: *Self, inst: Air.Inst.Index) !void {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const vector_ty = self.typeOfIndex(inst);
-    const len = vector_ty.vectorLen(zcu);
-    const ty_pl = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_pl;
-    const elements: []const Air.Inst.Ref = @ptrCast(self.air.extra.items[ty_pl.payload..][0..len]);
-    const result: MCValue = res: {
-        if (self.liveness.isUnused(inst)) break :res MCValue.dead;
-        return self.fail("TODO implement airAggregateInit for arm", .{});
-    };
-
-    if (elements.len <= Air.Liveness.bpi - 1) {
-        var buf = [1]Air.Inst.Ref{.none} ** (Air.Liveness.bpi - 1);
-        @memcpy(buf[0..elements.len], elements);
-        return self.finishAir(inst, result, buf);
-    }
-    var bt = try self.iterateBigTomb(inst, elements.len);
-    for (elements) |elem| {
-        bt.feed(elem);
-    }
-    return bt.finishAir(result);
-}
-
-fn airUnionInit(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_pl = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_pl;
-    const extra = self.air.extraData(Air.UnionInit, ty_pl.payload).data;
-    _ = extra;
-
-    return self.fail("TODO implement airUnionInit for arm", .{});
-}
-
-fn airPrefetch(self: *Self, inst: Air.Inst.Index) !void {
-    const prefetch = self.air.instructions.items(.data)[@intFromEnum(inst)].prefetch;
-    return self.finishAir(inst, MCValue.dead, .{ prefetch.ptr, .none, .none });
-}
-
-fn airMulAdd(self: *Self, inst: Air.Inst.Index) !void {
-    const pl_op = self.air.instructions.items(.data)[@intFromEnum(inst)].pl_op;
-    const extra = self.air.extraData(Air.Bin, pl_op.payload).data;
-    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else {
-        return self.fail("TODO implement airMulAdd for arm", .{});
-    };
-    return self.finishAir(inst, result, .{ extra.lhs, extra.rhs, pl_op.operand });
-}
-
-fn airTry(self: *Self, inst: Air.Inst.Index) !void {
-    const pt = self.pt;
-    const pl_op = self.air.instructions.items(.data)[@intFromEnum(inst)].pl_op;
-    const extra = self.air.extraData(Air.Try, pl_op.payload);
-    const body: []const Air.Inst.Index = @ptrCast(self.air.extra.items[extra.end..][0..extra.data.body_len]);
-    const result: MCValue = result: {
-        const error_union_bind: ReadArg.Bind = .{ .inst = pl_op.operand };
-        const error_union_ty = self.typeOf(pl_op.operand);
-        const error_union_size: u32 = @intCast(error_union_ty.abiSize(pt.zcu));
-        const error_union_align = error_union_ty.abiAlignment(pt.zcu);
-
-        // The error union will die in the body. However, we need the
-        // error union after the body in order to extract the payload
-        // of the error union, so we create a copy of it
-        const error_union_copy = try self.allocMem(error_union_size, error_union_align, null);
-        try self.genSetStack(error_union_ty, error_union_copy, try error_union_bind.resolveToMcv(self));
-
-        const is_err_result = try self.isErr(error_union_bind, error_union_ty);
-        const reloc = try self.condBr(is_err_result);
-
-        try self.genBody(body);
-        try self.performReloc(reloc);
-
-        break :result try self.errUnionPayload(.{ .mcv = .{ .stack_offset = error_union_copy } }, error_union_ty, null);
-    };
-    return self.finishAir(inst, result, .{ pl_op.operand, .none, .none });
-}
-
-fn airTryPtr(self: *Self, inst: Air.Inst.Index) !void {
-    const ty_pl = self.air.instructions.items(.data)[@intFromEnum(inst)].ty_pl;
-    const extra = self.air.extraData(Air.TryPtr, ty_pl.payload);
-    const body = self.air.extra.items[extra.end..][0..extra.data.body_len];
-    _ = body;
-    return self.fail("TODO implement airTryPtr for arm", .{});
-    // return self.finishAir(inst, result, .{ extra.data.ptr, .none, .none });
-}
-
-fn resolveInst(self: *Self, inst: Air.Inst.Ref) InnerError!MCValue {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-
-    // If the type has no codegen bits, no need to store it.
-    const inst_ty = self.typeOf(inst);
-    if (!inst_ty.hasRuntimeBitsIgnoreComptime(zcu) and !inst_ty.isError(zcu))
-        return MCValue{ .none = {} };
-
-    const inst_index = inst.toIndex() orelse return self.genTypedValue((try self.air.value(inst, pt)).?);
-
-    return self.getResolvedInstValue(inst_index);
-}
-
-fn getResolvedInstValue(self: *Self, inst: Air.Inst.Index) MCValue {
-    // Treat each stack item as a "layer" on top of the previous one.
-    var i: usize = self.branch_stack.items.len;
-    while (true) {
-        i -= 1;
-        if (self.branch_stack.items[i].inst_table.get(inst)) |mcv| {
-            assert(mcv != .dead);
-            return mcv;
-        }
-    }
-}
-
-fn genTypedValue(self: *Self, val: Value) InnerError!MCValue {
-    const pt = self.pt;
-    const mcv: MCValue = switch (try codegen.genTypedValue(
-        self.bin_file,
-        pt,
-        self.src_loc,
-        val,
-        self.target,
-    )) {
-        .mcv => |mcv| switch (mcv) {
-            .none => .none,
-            .undef => .undef,
-            .load_got, .load_symbol, .load_direct, .lea_symbol, .lea_direct => unreachable, // TODO
-            .immediate => |imm| .{ .immediate = @truncate(imm) },
-            .memory => |addr| .{ .memory = addr },
-        },
-        .fail => |msg| {
-            self.err_msg = msg;
-            return error.CodegenFail;
-        },
-    };
-    return mcv;
-}
-
-const CallMCValues = struct {
-    args: []MCValue,
-    return_value: MCValue,
-    stack_byte_count: u32,
-    stack_align: u32,
-
-    fn deinit(self: *CallMCValues, func: *Self) void {
-        func.gpa.free(self.args);
-        self.* = undefined;
-    }
-};
-
-/// Caller must call `CallMCValues.deinit`.
-fn resolveCallingConventionValues(self: *Self, fn_ty: Type) !CallMCValues {
-    const pt = self.pt;
-    const zcu = pt.zcu;
-    const ip = &zcu.intern_pool;
-    const fn_info = zcu.typeToFunc(fn_ty).?;
-    const cc = fn_info.cc;
-    var result: CallMCValues = .{
-        .args = try self.gpa.alloc(MCValue, fn_info.param_types.len),
-        // These undefined values must be populated before returning from this function.
-        .return_value = undefined,
-        .stack_byte_count = undefined,
-        .stack_align = undefined,
-    };
-    errdefer self.gpa.free(result.args);
-
-    const ret_ty = fn_ty.fnReturnType(zcu);
-
-    switch (cc) {
-        .naked => {
-            assert(result.args.len == 0);
-            result.return_value = .{ .unreach = {} };
-            result.stack_byte_count = 0;
-            result.stack_align = 1;
-            return result;
-        },
-        .arm_aapcs => {
-            // ARM Procedure Call Standard, Chapter 6.5
-            var ncrn: usize = 0; // Next Core Register Number
-            var nsaa: u32 = 0; // Next stacked argument address
-
-            if (ret_ty.zigTypeTag(zcu) == .noreturn) {
-                result.return_value = .{ .unreach = {} };
-            } else if (!ret_ty.hasRuntimeBitsIgnoreComptime(zcu)) {
-                result.return_value = .{ .none = {} };
-            } else {
-                const ret_ty_size: u32 = @intCast(ret_ty.abiSize(zcu));
-                // TODO handle cases where multiple registers are used
-                if (ret_ty_size <= 4) {
-                    result.return_value = .{ .register = c_abi_int_return_regs[0] };
-                } else {
-                    // The result is returned by reference, not by
-                    // value. This means that r0 will contain the
-                    // address of where this function should write the
-                    // result into.
-                    result.return_value = .{ .stack_offset = 0 };
-                    ncrn = 1;
-                }
-            }
-
-            for (fn_info.param_types.get(ip), result.args) |ty, *result_arg| {
-                if (Type.fromInterned(ty).abiAlignment(zcu) == .@"8")
-                    ncrn = std.mem.alignForward(usize, ncrn, 2);
-
-                const param_size: u32 = @intCast(Type.fromInterned(ty).abiSize(zcu));
-                if (std.math.divCeil(u32, param_size, 4) catch unreachable <= 4 - ncrn) {
-                    if (param_size <= 4) {
-                        result_arg.* = .{ .register = c_abi_int_param_regs[ncrn] };
-                        ncrn += 1;
-                    } else {
-                        return self.fail("TODO MCValues with multiple registers", .{});
-                    }
-                } else if (ncrn < 4 and nsaa == 0) {
-                    return self.fail("TODO MCValues split between registers and stack", .{});
-                } else {
-                    ncrn = 4;
-                    if (Type.fromInterned(ty).abiAlignment(zcu) == .@"8")
-                        nsaa = std.mem.alignForward(u32, nsaa, 8);
-
-                    result_arg.* = .{ .stack_argument_offset = nsaa };
-                    nsaa += param_size;
-                }
-            }
-
-            result.stack_byte_count = nsaa;
-            result.stack_align = 8;
-        },
-        .auto => {
-            if (ret_ty.zigTypeTag(zcu) == .noreturn) {
-                result.return_value = .{ .unreach = {} };
-            } else if (!ret_ty.hasRuntimeBitsIgnoreComptime(zcu) and !ret_ty.isError(zcu)) {
-                result.return_value = .{ .none = {} };
-            } else {
-                const ret_ty_size: u32 = @intCast(ret_ty.abiSize(zcu));
-                if (ret_ty_size == 0) {
-                    assert(ret_ty.isError(zcu));
-                    result.return_value = .{ .immediate = 0 };
-                } else if (ret_ty_size <= 4) {
-                    result.return_value = .{ .register = .r0 };
-                } else {
-                    // The result is returned by reference, not by
-                    // value. This means that r0 will contain the
-                    // address of where this function should write the
-                    // result into.
-                    result.return_value = .{ .stack_offset = 0 };
-                }
-            }
-
-            var stack_offset: u32 = 0;
-
-            for (fn_info.param_types.get(ip), result.args) |ty, *result_arg| {
-                if (Type.fromInterned(ty).abiSize(zcu) > 0) {
-                    const param_size: u32 = @intCast(Type.fromInterned(ty).abiSize(zcu));
-                    const param_alignment = Type.fromInterned(ty).abiAlignment(zcu);
-
-                    stack_offset = @intCast(param_alignment.forward(stack_offset));
-                    result_arg.* = .{ .stack_argument_offset = stack_offset };
-                    stack_offset += param_size;
-                } else {
-                    result_arg.* = .{ .none = {} };
-                }
-            }
-
-            result.stack_byte_count = stack_offset;
-            result.stack_align = 8;
-        },
-        else => return self.fail("TODO implement function parameters for {} on arm", .{cc}),
-    }
-
-    return result;
-}
-
-/// TODO support scope overrides. Also note this logic is duplicated with `Zcu.wantSafety`.
-fn wantSafety(self: *Self) bool {
-    return switch (self.bin_file.comp.root_mod.optimize_mode) {
-        .Debug => true,
-        .ReleaseSafe => true,
-        .ReleaseFast => false,
-        .ReleaseSmall => false,
-    };
-}
-
-fn fail(self: *Self, comptime format: []const u8, args: anytype) error{ OutOfMemory, CodegenFail } {
-    @branchHint(.cold);
-    const zcu = self.pt.zcu;
-    const func = zcu.funcInfo(self.func_index);
-    const msg = try ErrorMsg.create(zcu.gpa, self.src_loc, format, args);
-    return zcu.codegenFailMsg(func.owner_nav, msg);
-}
-
-fn failMsg(self: *Self, msg: *ErrorMsg) error{ OutOfMemory, CodegenFail } {
-    @branchHint(.cold);
-    const zcu = self.pt.zcu;
-    const func = zcu.funcInfo(self.func_index);
-    return zcu.codegenFailMsg(func.owner_nav, msg);
-}
-
-fn parseRegName(name: []const u8) ?Register {
-    if (@hasDecl(Register, "parseRegName")) {
-        return Register.parseRegName(name);
-    }
-    return std.meta.stringToEnum(Register, name);
-}
-
-fn typeOf(self: *Self, inst: Air.Inst.Ref) Type {
-    return self.air.typeOf(inst, &self.pt.zcu.intern_pool);
-}
-
-fn typeOfIndex(self: *Self, inst: Air.Inst.Index) Type {
-    return self.air.typeOfIndex(inst, &self.pt.zcu.intern_pool);
-}
src/arch/arm/Emit.zig
@@ -1,712 +0,0 @@
-//! This file contains the functionality for lowering AArch32 MIR into
-//! machine code
-
-const Emit = @This();
-const builtin = @import("builtin");
-const std = @import("std");
-const math = std.math;
-const Mir = @import("Mir.zig");
-const bits = @import("bits.zig");
-const link = @import("../../link.zig");
-const Zcu = @import("../../Zcu.zig");
-const Type = @import("../../Type.zig");
-const ErrorMsg = Zcu.ErrorMsg;
-const Target = std.Target;
-const assert = std.debug.assert;
-const Instruction = bits.Instruction;
-const Register = bits.Register;
-const log = std.log.scoped(.aarch32_emit);
-const CodeGen = @import("CodeGen.zig");
-
-mir: Mir,
-bin_file: *link.File,
-debug_output: link.File.DebugInfoOutput,
-target: *const std.Target,
-err_msg: ?*ErrorMsg = null,
-src_loc: Zcu.LazySrcLoc,
-code: *std.ArrayListUnmanaged(u8),
-
-prev_di_line: u32,
-prev_di_column: u32,
-/// Relative to the beginning of `code`.
-prev_di_pc: usize,
-
-/// The amount of stack space consumed by the saved callee-saved
-/// registers in bytes
-saved_regs_stack_space: u32,
-
-/// The final stack frame size of the function (already aligned to the
-/// respective stack alignment). Does not include prologue stack space.
-stack_size: u32,
-
-/// The branch type of every branch
-branch_types: std.AutoHashMapUnmanaged(Mir.Inst.Index, BranchType) = .empty,
-/// For every forward branch, maps the target instruction to a list of
-/// branches which branch to this target instruction
-branch_forward_origins: std.AutoHashMapUnmanaged(Mir.Inst.Index, std.ArrayListUnmanaged(Mir.Inst.Index)) = .empty,
-/// For backward branches: stores the code offset of the target
-/// instruction
-///
-/// For forward branches: stores the code offset of the branch
-/// instruction
-code_offset_mapping: std.AutoHashMapUnmanaged(Mir.Inst.Index, usize) = .empty,
-
-const InnerError = error{
-    OutOfMemory,
-    EmitFail,
-};
-
-const BranchType = enum {
-    b,
-
-    fn default(tag: Mir.Inst.Tag) BranchType {
-        return switch (tag) {
-            .b => .b,
-            else => unreachable,
-        };
-    }
-};
-
-pub fn emitMir(
-    emit: *Emit,
-) !void {
-    const mir_tags = emit.mir.instructions.items(.tag);
-
-    // Find smallest lowerings for branch instructions
-    try emit.lowerBranches();
-
-    // Emit machine code
-    for (mir_tags, 0..) |tag, index| {
-        const inst = @as(u32, @intCast(index));
-        switch (tag) {
-            .add => try emit.mirDataProcessing(inst),
-            .adds => try emit.mirDataProcessing(inst),
-            .@"and" => try emit.mirDataProcessing(inst),
-            .cmp => try emit.mirDataProcessing(inst),
-            .eor => try emit.mirDataProcessing(inst),
-            .mov => try emit.mirDataProcessing(inst),
-            .mvn => try emit.mirDataProcessing(inst),
-            .orr => try emit.mirDataProcessing(inst),
-            .rsb => try emit.mirDataProcessing(inst),
-            .sub => try emit.mirDataProcessing(inst),
-            .subs => try emit.mirDataProcessing(inst),
-
-            .sub_sp_scratch_r4 => try emit.mirSubStackPointer(inst),
-
-            .asr => try emit.mirShift(inst),
-            .lsl => try emit.mirShift(inst),
-            .lsr => try emit.mirShift(inst),
-
-            .b => try emit.mirBranch(inst),
-
-            .undefined_instruction => try emit.mirUndefinedInstruction(),
-            .bkpt => try emit.mirExceptionGeneration(inst),
-
-            .blx => try emit.mirBranchExchange(inst),
-            .bx => try emit.mirBranchExchange(inst),
-
-            .dbg_line => try emit.mirDbgLine(inst),
-
-            .dbg_prologue_end => try emit.mirDebugPrologueEnd(),
-
-            .dbg_epilogue_begin => try emit.mirDebugEpilogueBegin(),
-
-            .ldr => try emit.mirLoadStore(inst),
-            .ldrb => try emit.mirLoadStore(inst),
-            .str => try emit.mirLoadStore(inst),
-            .strb => try emit.mirLoadStore(inst),
-
-            .ldr_ptr_stack_argument => try emit.mirLoadStackArgument(inst),
-            .ldr_stack_argument => try emit.mirLoadStackArgument(inst),
-            .ldrb_stack_argument => try emit.mirLoadStackArgument(inst),
-            .ldrh_stack_argument => try emit.mirLoadStackArgument(inst),
-            .ldrsb_stack_argument => try emit.mirLoadStackArgument(inst),
-            .ldrsh_stack_argument => try emit.mirLoadStackArgument(inst),
-
-            .ldrh => try emit.mirLoadStoreExtra(inst),
-            .ldrsb => try emit.mirLoadStoreExtra(inst),
-            .ldrsh => try emit.mirLoadStoreExtra(inst),
-            .strh => try emit.mirLoadStoreExtra(inst),
-
-            .movw => try emit.mirSpecialMove(inst),
-            .movt => try emit.mirSpecialMove(inst),
-
-            .mul => try emit.mirMultiply(inst),
-            .smulbb => try emit.mirMultiply(inst),
-
-            .smull => try emit.mirMultiplyLong(inst),
-            .umull => try emit.mirMultiplyLong(inst),
-
-            .nop => try emit.mirNop(),
-
-            .pop => try emit.mirBlockDataTransfer(inst),
-            .push => try emit.mirBlockDataTransfer(inst),
-
-            .svc => try emit.mirSupervisorCall(inst),
-
-            .sbfx => try emit.mirBitFieldExtract(inst),
-            .ubfx => try emit.mirBitFieldExtract(inst),
-        }
-    }
-}
-
-pub fn deinit(emit: *Emit) void {
-    const comp = emit.bin_file.comp;
-    const gpa = comp.gpa;
-
-    var iter = emit.branch_forward_origins.valueIterator();
-    while (iter.next()) |origin_list| {
-        origin_list.deinit(gpa);
-    }
-
-    emit.branch_types.deinit(gpa);
-    emit.branch_forward_origins.deinit(gpa);
-    emit.code_offset_mapping.deinit(gpa);
-    emit.* = undefined;
-}
-
-fn optimalBranchType(emit: *Emit, tag: Mir.Inst.Tag, offset: i64) !BranchType {
-    assert(std.mem.isAlignedGeneric(i64, offset, 4)); // misaligned offset
-
-    switch (tag) {
-        .b => {
-            if (std.math.cast(i24, @divExact(offset, 4))) |_| {
-                return BranchType.b;
-            } else {
-                return emit.fail("TODO support larger branches", .{});
-            }
-        },
-        else => unreachable,
-    }
-}
-
-fn instructionSize(emit: *Emit, inst: Mir.Inst.Index) usize {
-    const tag = emit.mir.instructions.items(.tag)[inst];
-
-    if (isBranch(tag)) {
-        switch (emit.branch_types.get(inst).?) {
-            .b => return 4,
-        }
-    }
-
-    switch (tag) {
-        .dbg_line,
-        .dbg_epilogue_begin,
-        .dbg_prologue_end,
-        => return 0,
-
-        .sub_sp_scratch_r4 => {
-            const imm32 = emit.mir.instructions.items(.data)[inst].imm32;
-
-            if (imm32 == 0) {
-                return 0 * 4;
-            } else if (Instruction.Operand.fromU32(imm32) != null) {
-                // sub
-                return 1 * 4;
-            } else if (emit.target.cpu.has(.arm, .has_v7)) {
-                // movw; movt; sub
-                return 3 * 4;
-            } else {
-                // mov; orr; orr; orr; sub
-                return 5 * 4;
-            }
-        },
-
-        else => return 4,
-    }
-}
-
-fn isBranch(tag: Mir.Inst.Tag) bool {
-    return switch (tag) {
-        .b => true,
-        else => false,
-    };
-}
-
-fn branchTarget(emit: *Emit, inst: Mir.Inst.Index) Mir.Inst.Index {
-    const tag = emit.mir.instructions.items(.tag)[inst];
-
-    switch (tag) {
-        .b => return emit.mir.instructions.items(.data)[inst].inst,
-        else => unreachable,
-    }
-}
-
-fn lowerBranches(emit: *Emit) !void {
-    const comp = emit.bin_file.comp;
-    const gpa = comp.gpa;
-    const mir_tags = emit.mir.instructions.items(.tag);
-
-    // First pass: Note down all branches and their target
-    // instructions, i.e. populate branch_types,
-    // branch_forward_origins, and code_offset_mapping
-    //
-    // TODO optimization opportunity: do this in codegen while
-    // generating MIR
-    for (mir_tags, 0..) |tag, index| {
-        const inst = @as(u32, @intCast(index));
-        if (isBranch(tag)) {
-            const target_inst = emit.branchTarget(inst);
-
-            // Remember this branch instruction
-            try emit.branch_types.put(gpa, inst, BranchType.default(tag));
-
-            // Forward branches require some extra stuff: We only
-            // know their offset once we arrive at the target
-            // instruction. Therefore, we need to be able to
-            // access the branch instruction when we visit the
-            // target instruction in order to manipulate its type
-            // etc.
-            if (target_inst > inst) {
-                // Remember the branch instruction index
-                try emit.code_offset_mapping.put(gpa, inst, 0);
-
-                if (emit.branch_forward_origins.getPtr(target_inst)) |origin_list| {
-                    try origin_list.append(gpa, inst);
-                } else {
-                    var origin_list: std.ArrayListUnmanaged(Mir.Inst.Index) = .empty;
-                    try origin_list.append(gpa, inst);
-                    try emit.branch_forward_origins.put(gpa, target_inst, origin_list);
-                }
-            }
-
-            // Remember the target instruction index so that we
-            // update the real code offset in all future passes
-            //
-            // putNoClobber may not be used as the put operation
-            // may clobber the entry when multiple branches branch
-            // to the same target instruction
-            try emit.code_offset_mapping.put(gpa, target_inst, 0);
-        }
-    }
-
-    // Further passes: Until all branches are lowered, interate
-    // through all instructions and calculate new offsets and
-    // potentially new branch types
-    var all_branches_lowered = false;
-    while (!all_branches_lowered) {
-        all_branches_lowered = true;
-        var current_code_offset: usize = 0;
-
-        for (mir_tags, 0..) |tag, index| {
-            const inst = @as(u32, @intCast(index));
-
-            // If this instruction contained in the code offset
-            // mapping (when it is a target of a branch or if it is a
-            // forward branch), update the code offset
-            if (emit.code_offset_mapping.getPtr(inst)) |offset| {
-                offset.* = current_code_offset;
-            }
-
-            // If this instruction is a backward branch, calculate the
-            // offset, which may potentially update the branch type
-            if (isBranch(tag)) {
-                const target_inst = emit.branchTarget(inst);
-                if (target_inst < inst) {
-                    const target_offset = emit.code_offset_mapping.get(target_inst).?;
-                    const offset = @as(i64, @intCast(target_offset)) - @as(i64, @intCast(current_code_offset + 8));
-                    const branch_type = emit.branch_types.getPtr(inst).?;
-                    const optimal_branch_type = try emit.optimalBranchType(tag, offset);
-                    if (branch_type.* != optimal_branch_type) {
-                        branch_type.* = optimal_branch_type;
-                        all_branches_lowered = false;
-                    }
-
-                    log.debug("lowerBranches: branch {} has offset {}", .{ inst, offset });
-                }
-            }
-
-            // If this instruction is the target of one or more
-            // forward branches, calculate the offset, which may
-            // potentially update the branch type
-            if (emit.branch_forward_origins.get(inst)) |origin_list| {
-                for (origin_list.items) |forward_branch_inst| {
-                    const branch_tag = emit.mir.instructions.items(.tag)[forward_branch_inst];
-                    const forward_branch_inst_offset = emit.code_offset_mapping.get(forward_branch_inst).?;
-                    const offset = @as(i64, @intCast(current_code_offset)) - @as(i64, @intCast(forward_branch_inst_offset + 8));
-                    const branch_type = emit.branch_types.getPtr(forward_branch_inst).?;
-                    const optimal_branch_type = try emit.optimalBranchType(branch_tag, offset);
-                    if (branch_type.* != optimal_branch_type) {
-                        branch_type.* = optimal_branch_type;
-                        all_branches_lowered = false;
-                    }
-
-                    log.debug("lowerBranches: branch {} has offset {}", .{ forward_branch_inst, offset });
-                }
-            }
-
-            // Increment code offset
-            current_code_offset += emit.instructionSize(inst);
-        }
-    }
-}
-
-fn writeInstruction(emit: *Emit, instruction: Instruction) !void {
-    const comp = emit.bin_file.comp;
-    const gpa = comp.gpa;
-    const endian = emit.target.cpu.arch.endian();
-    std.mem.writeInt(u32, try emit.code.addManyAsArray(gpa, 4), instruction.toU32(), endian);
-}
-
-fn fail(emit: *Emit, comptime format: []const u8, args: anytype) InnerError {
-    @branchHint(.cold);
-    assert(emit.err_msg == null);
-    const comp = emit.bin_file.comp;
-    const gpa = comp.gpa;
-    emit.err_msg = try ErrorMsg.create(gpa, emit.src_loc, format, args);
-    return error.EmitFail;
-}
-
-fn dbgAdvancePCAndLine(self: *Emit, line: u32, column: u32) !void {
-    const delta_line = @as(i32, @intCast(line)) - @as(i32, @intCast(self.prev_di_line));
-    const delta_pc: usize = self.code.items.len - self.prev_di_pc;
-    switch (self.debug_output) {
-        .dwarf => |dw| {
-            try dw.advancePCAndLine(delta_line, delta_pc);
-            self.prev_di_line = line;
-            self.prev_di_column = column;
-            self.prev_di_pc = self.code.items.len;
-        },
-        .plan9 => |dbg_out| {
-            if (delta_pc <= 0) return; // only do this when the pc changes
-
-            // increasing the line number
-            try link.File.Plan9.changeLine(&dbg_out.dbg_line, delta_line);
-            // increasing the pc
-            const d_pc_p9 = @as(i64, @intCast(delta_pc)) - dbg_out.pc_quanta;
-            if (d_pc_p9 > 0) {
-                // minus one because if its the last one, we want to leave space to change the line which is one pc quanta
-                try dbg_out.dbg_line.append(@as(u8, @intCast(@divExact(d_pc_p9, dbg_out.pc_quanta) + 128)) - dbg_out.pc_quanta);
-                if (dbg_out.pcop_change_index) |pci|
-                    dbg_out.dbg_line.items[pci] += 1;
-                dbg_out.pcop_change_index = @as(u32, @intCast(dbg_out.dbg_line.items.len - 1));
-            } else if (d_pc_p9 == 0) {
-                // we don't need to do anything, because adding the pc quanta does it for us
-            } else unreachable;
-            if (dbg_out.start_line == null)
-                dbg_out.start_line = self.prev_di_line;
-            dbg_out.end_line = line;
-            // only do this if the pc changed
-            self.prev_di_line = line;
-            self.prev_di_column = column;
-            self.prev_di_pc = self.code.items.len;
-        },
-        .none => {},
-    }
-}
-
-fn mirDataProcessing(emit: *Emit, inst: Mir.Inst.Index) !void {
-    const tag = emit.mir.instructions.items(.tag)[inst];
-    const cond = emit.mir.instructions.items(.cond)[inst];
-
-    switch (tag) {
-        .add,
-        .adds,
-        .@"and",
-        .eor,
-        .orr,
-        .rsb,
-        .sub,
-        .subs,
-        => {
-            const rr_op = emit.mir.instructions.items(.data)[inst].rr_op;
-            switch (tag) {
-                .add => try emit.writeInstruction(Instruction.add(cond, rr_op.rd, rr_op.rn, rr_op.op)),
-                .adds => try emit.writeInstruction(Instruction.adds(cond, rr_op.rd, rr_op.rn, rr_op.op)),
-                .@"and" => try emit.writeInstruction(Instruction.@"and"(cond, rr_op.rd, rr_op.rn, rr_op.op)),
-                .eor => try emit.writeInstruction(Instruction.eor(cond, rr_op.rd, rr_op.rn, rr_op.op)),
-                .orr => try emit.writeInstruction(Instruction.orr(cond, rr_op.rd, rr_op.rn, rr_op.op)),
-                .rsb => try emit.writeInstruction(Instruction.rsb(cond, rr_op.rd, rr_op.rn, rr_op.op)),
-                .sub => try emit.writeInstruction(Instruction.sub(cond, rr_op.rd, rr_op.rn, rr_op.op)),
-                .subs => try emit.writeInstruction(Instruction.subs(cond, rr_op.rd, rr_op.rn, rr_op.op)),
-                else => unreachable,
-            }
-        },
-        .cmp => {
-            const r_op_cmp = emit.mir.instructions.items(.data)[inst].r_op_cmp;
-            try emit.writeInstruction(Instruction.cmp(cond, r_op_cmp.rn, r_op_cmp.op));
-        },
-        .mov,
-        .mvn,
-        => {
-            const r_op_mov = emit.mir.instructions.items(.data)[inst].r_op_mov;
-            switch (tag) {
-                .mov => try emit.writeInstruction(Instruction.mov(cond, r_op_mov.rd, r_op_mov.op)),
-                .mvn => try emit.writeInstruction(Instruction.mvn(cond, r_op_mov.rd, r_op_mov.op)),
-                else => unreachable,
-            }
-        },
-        else => unreachable,
-    }
-}
-
-fn mirSubStackPointer(emit: *Emit, inst: Mir.Inst.Index) !void {
-    const tag = emit.mir.instructions.items(.tag)[inst];
-    const cond = emit.mir.instructions.items(.cond)[inst];
-    const imm32 = emit.mir.instructions.items(.data)[inst].imm32;
-
-    switch (tag) {
-        .sub_sp_scratch_r4 => {
-            if (imm32 == 0) return;
-
-            const operand = Instruction.Operand.fromU32(imm32) orelse blk: {
-                const scratch: Register = .r4;
-
-                if (emit.target.cpu.has(.arm, .has_v7)) {
-                    try emit.writeInstruction(Instruction.movw(cond, scratch, @as(u16, @truncate(imm32))));
-                    try emit.writeInstruction(Instruction.movt(cond, scratch, @as(u16, @truncate(imm32 >> 16))));
-                } else {
-                    try emit.writeInstruction(Instruction.mov(cond, scratch, Instruction.Operand.imm(@as(u8, @truncate(imm32)), 0)));
-                    try emit.writeInstruction(Instruction.orr(cond, scratch, scratch, Instruction.Operand.imm(@as(u8, @truncate(imm32 >> 8)), 12)));
-                    try emit.writeInstruction(Instruction.orr(cond, scratch, scratch, Instruction.Operand.imm(@as(u8, @truncate(imm32 >> 16)), 8)));
-                    try emit.writeInstruction(Instruction.orr(cond, scratch, scratch, Instruction.Operand.imm(@as(u8, @truncate(imm32 >> 24)), 4)));
-                }
-
-                break :blk Instruction.Operand.reg(scratch, Instruction.Operand.Shift.none);
-            };
-
-            try emit.writeInstruction(Instruction.sub(cond, .sp, .sp, operand));
-        },
-        else => unreachable,
-    }
-}
-
-fn mirShift(emit: *Emit, inst: Mir.Inst.Index) !void {
-    const tag = emit.mir.instructions.items(.tag)[inst];
-    const cond = emit.mir.instructions.items(.cond)[inst];
-    const rr_shift = emit.mir.instructions.items(.data)[inst].rr_shift;
-
-    switch (tag) {
-        .asr => try emit.writeInstruction(Instruction.asr(cond, rr_shift.rd, rr_shift.rm, rr_shift.shift_amount)),
-        .lsl => try emit.writeInstruction(Instruction.lsl(cond, rr_shift.rd, rr_shift.rm, rr_shift.shift_amount)),
-        .lsr => try emit.writeInstruction(Instruction.lsr(cond, rr_shift.rd, rr_shift.rm, rr_shift.shift_amount)),
-        else => unreachable,
-    }
-}
-
-fn mirBranch(emit: *Emit, inst: Mir.Inst.Index) !void {
-    const tag = emit.mir.instructions.items(.tag)[inst];
-    const cond = emit.mir.instructions.items(.cond)[inst];
-    const target_inst = emit.mir.instructions.items(.data)[inst].inst;
-
-    const offset = @as(i64, @intCast(emit.code_offset_mapping.get(target_inst).?)) - @as(i64, @intCast(emit.code.items.len + 8));
-    const branch_type = emit.branch_types.get(inst).?;
-
-    switch (branch_type) {
-        .b => switch (tag) {
-            .b => try emit.writeInstruction(Instruction.b(cond, @as(i26, @intCast(offset)))),
-            else => unreachable,
-        },
-    }
-}
-
-fn mirUndefinedInstruction(emit: *Emit) !void {
-    try emit.writeInstruction(Instruction.undefinedInstruction());
-}
-
-fn mirExceptionGeneration(emit: *Emit, inst: Mir.Inst.Index) !void {
-    const tag = emit.mir.instructions.items(.tag)[inst];
-    const imm16 = emit.mir.instructions.items(.data)[inst].imm16;
-
-    switch (tag) {
-        .bkpt => try emit.writeInstruction(Instruction.bkpt(imm16)),
-        else => unreachable,
-    }
-}
-
-fn mirBranchExchange(emit: *Emit, inst: Mir.Inst.Index) !void {
-    const tag = emit.mir.instructions.items(.tag)[inst];
-    const cond = emit.mir.instructions.items(.cond)[inst];
-    const reg = emit.mir.instructions.items(.data)[inst].reg;
-
-    switch (tag) {
-        .blx => try emit.writeInstruction(Instruction.blx(cond, reg)),
-        .bx => try emit.writeInstruction(Instruction.bx(cond, reg)),
-        else => unreachable,
-    }
-}
-
-fn mirDbgLine(emit: *Emit, inst: Mir.Inst.Index) !void {
-    const tag = emit.mir.instructions.items(.tag)[inst];
-    const dbg_line_column = emit.mir.instructions.items(.data)[inst].dbg_line_column;
-
-    switch (tag) {
-        .dbg_line => try emit.dbgAdvancePCAndLine(dbg_line_column.line, dbg_line_column.column),
-        else => unreachable,
-    }
-}
-
-fn mirDebugPrologueEnd(emit: *Emit) !void {
-    switch (emit.debug_output) {
-        .dwarf => |dw| {
-            try dw.setPrologueEnd();
-            try emit.dbgAdvancePCAndLine(emit.prev_di_line, emit.prev_di_column);
-        },
-        .plan9 => {},
-        .none => {},
-    }
-}
-
-fn mirDebugEpilogueBegin(emit: *Emit) !void {
-    switch (emit.debug_output) {
-        .dwarf => |dw| {
-            try dw.setEpilogueBegin();
-            try emit.dbgAdvancePCAndLine(emit.prev_di_line, emit.prev_di_column);
-        },
-        .plan9 => {},
-        .none => {},
-    }
-}
-
-fn mirLoadStore(emit: *Emit, inst: Mir.Inst.Index) !void {
-    const tag = emit.mir.instructions.items(.tag)[inst];
-    const cond = emit.mir.instructions.items(.cond)[inst];
-    const rr_offset = emit.mir.instructions.items(.data)[inst].rr_offset;
-
-    switch (tag) {
-        .ldr => try emit.writeInstruction(Instruction.ldr(cond, rr_offset.rt, rr_offset.rn, rr_offset.offset)),
-        .ldrb => try emit.writeInstruction(Instruction.ldrb(cond, rr_offset.rt, rr_offset.rn, rr_offset.offset)),
-        .str => try emit.writeInstruction(Instruction.str(cond, rr_offset.rt, rr_offset.rn, rr_offset.offset)),
-        .strb => try emit.writeInstruction(Instruction.strb(cond, rr_offset.rt, rr_offset.rn, rr_offset.offset)),
-        else => unreachable,
-    }
-}
-
-fn mirLoadStackArgument(emit: *Emit, inst: Mir.Inst.Index) !void {
-    const tag = emit.mir.instructions.items(.tag)[inst];
-    const cond = emit.mir.instructions.items(.cond)[inst];
-    const r_stack_offset = emit.mir.instructions.items(.data)[inst].r_stack_offset;
-    const rt = r_stack_offset.rt;
-
-    const raw_offset = emit.stack_size + emit.saved_regs_stack_space + r_stack_offset.stack_offset;
-    switch (tag) {
-        .ldr_ptr_stack_argument => {
-            const operand = Instruction.Operand.fromU32(raw_offset) orelse
-                return emit.fail("TODO mirLoadStack larger offsets", .{});
-
-            try emit.writeInstruction(Instruction.add(cond, rt, .sp, operand));
-        },
-        .ldr_stack_argument,
-        .ldrb_stack_argument,
-        => {
-            const offset = if (raw_offset <= math.maxInt(u12)) blk: {
-                break :blk Instruction.Offset.imm(@as(u12, @intCast(raw_offset)));
-            } else return emit.fail("TODO mirLoadStack larger offsets", .{});
-
-            switch (tag) {
-                .ldr_stack_argument => try emit.writeInstruction(Instruction.ldr(cond, rt, .sp, .{ .offset = offset })),
-                .ldrb_stack_argument => try emit.writeInstruction(Instruction.ldrb(cond, rt, .sp, .{ .offset = offset })),
-                else => unreachable,
-            }
-        },
-        .ldrh_stack_argument,
-        .ldrsb_stack_argument,
-        .ldrsh_stack_argument,
-        => {
-            const offset = if (raw_offset <= math.maxInt(u8)) blk: {
-                break :blk Instruction.ExtraLoadStoreOffset.imm(@as(u8, @intCast(raw_offset)));
-            } else return emit.fail("TODO mirLoadStack larger offsets", .{});
-
-            switch (tag) {
-                .ldrh_stack_argument => try emit.writeInstruction(Instruction.ldrh(cond, rt, .sp, .{ .offset = offset })),
-                .ldrsb_stack_argument => try emit.writeInstruction(Instruction.ldrsb(cond, rt, .sp, .{ .offset = offset })),
-                .ldrsh_stack_argument => try emit.writeInstruction(Instruction.ldrsh(cond, rt, .sp, .{ .offset = offset })),
-                else => unreachable,
-            }
-        },
-        else => unreachable,
-    }
-}
-
-fn mirLoadStoreExtra(emit: *Emit, inst: Mir.Inst.Index) !void {
-    const tag = emit.mir.instructions.items(.tag)[inst];
-    const cond = emit.mir.instructions.items(.cond)[inst];
-    const rr_extra_offset = emit.mir.instructions.items(.data)[inst].rr_extra_offset;
-
-    switch (tag) {
-        .ldrh => try emit.writeInstruction(Instruction.ldrh(cond, rr_extra_offset.rt, rr_extra_offset.rn, rr_extra_offset.offset)),
-        .ldrsb => try emit.writeInstruction(Instruction.ldrsb(cond, rr_extra_offset.rt, rr_extra_offset.rn, rr_extra_offset.offset)),
-        .ldrsh => try emit.writeInstruction(Instruction.ldrsh(cond, rr_extra_offset.rt, rr_extra_offset.rn, rr_extra_offset.offset)),
-        .strh => try emit.writeInstruction(Instruction.strh(cond, rr_extra_offset.rt, rr_extra_offset.rn, rr_extra_offset.offset)),
-        else => unreachable,
-    }
-}
-
-fn mirSpecialMove(emit: *Emit, inst: Mir.Inst.Index) !void {
-    const tag = emit.mir.instructions.items(.tag)[inst];
-    const cond = emit.mir.instructions.items(.cond)[inst];
-    const r_imm16 = emit.mir.instructions.items(.data)[inst].r_imm16;
-
-    switch (tag) {
-        .movw => try emit.writeInstruction(Instruction.movw(cond, r_imm16.rd, r_imm16.imm16)),
-        .movt => try emit.writeInstruction(Instruction.movt(cond, r_imm16.rd, r_imm16.imm16)),
-        else => unreachable,
-    }
-}
-
-fn mirMultiply(emit: *Emit, inst: Mir.Inst.Index) !void {
-    const tag = emit.mir.instructions.items(.tag)[inst];
-    const cond = emit.mir.instructions.items(.cond)[inst];
-    const rrr = emit.mir.instructions.items(.data)[inst].rrr;
-
-    switch (tag) {
-        .mul => try emit.writeInstruction(Instruction.mul(cond, rrr.rd, rrr.rn, rrr.rm)),
-        .smulbb => try emit.writeInstruction(Instruction.smulbb(cond, rrr.rd, rrr.rn, rrr.rm)),
-        else => unreachable,
-    }
-}
-
-fn mirMultiplyLong(emit: *Emit, inst: Mir.Inst.Index) !void {
-    const tag = emit.mir.instructions.items(.tag)[inst];
-    const cond = emit.mir.instructions.items(.cond)[inst];
-    const rrrr = emit.mir.instructions.items(.data)[inst].rrrr;
-
-    switch (tag) {
-        .smull => try emit.writeInstruction(Instruction.smull(cond, rrrr.rdlo, rrrr.rdhi, rrrr.rn, rrrr.rm)),
-        .umull => try emit.writeInstruction(Instruction.umull(cond, rrrr.rdlo, rrrr.rdhi, rrrr.rn, rrrr.rm)),
-        else => unreachable,
-    }
-}
-
-fn mirNop(emit: *Emit) !void {
-    try emit.writeInstruction(Instruction.nop());
-}
-
-fn mirBlockDataTransfer(emit: *Emit, inst: Mir.Inst.Index) !void {
-    const tag = emit.mir.instructions.items(.tag)[inst];
-    const cond = emit.mir.instructions.items(.cond)[inst];
-    const register_list = emit.mir.instructions.items(.data)[inst].register_list;
-
-    switch (tag) {
-        .pop => try emit.writeInstruction(Instruction.ldm(cond, .sp, true, register_list)),
-        .push => try emit.writeInstruction(Instruction.stmdb(cond, .sp, true, register_list)),
-        else => unreachable,
-    }
-}
-
-fn mirSupervisorCall(emit: *Emit, inst: Mir.Inst.Index) !void {
-    const tag = emit.mir.instructions.items(.tag)[inst];
-    const cond = emit.mir.instructions.items(.cond)[inst];
-    const imm24 = emit.mir.instructions.items(.data)[inst].imm24;
-
-    switch (tag) {
-        .svc => try emit.writeInstruction(Instruction.svc(cond, imm24)),
-        else => unreachable,
-    }
-}
-
-fn mirBitFieldExtract(emit: *Emit, inst: Mir.Inst.Index) !void {
-    const tag = emit.mir.instructions.items(.tag)[inst];
-    const cond = emit.mir.instructions.items(.cond)[inst];
-    const rr_lsb_width = emit.mir.instructions.items(.data)[inst].rr_lsb_width;
-    const rd = rr_lsb_width.rd;
-    const rn = rr_lsb_width.rn;
-    const lsb = rr_lsb_width.lsb;
-    const width = rr_lsb_width.width;
-
-    switch (tag) {
-        .sbfx => try emit.writeInstruction(Instruction.sbfx(cond, rd, rn, lsb, width)),
-        .ubfx => try emit.writeInstruction(Instruction.ubfx(cond, rd, rn, lsb, width)),
-        else => unreachable,
-    }
-}
src/arch/arm/Mir.zig
@@ -1,340 +0,0 @@
-//! Machine Intermediate Representation.
-//! This data is produced by ARM Codegen or ARM assembly parsing
-//! These instructions have a 1:1 correspondence with machine code instructions
-//! for the target. MIR can be lowered to source-annotated textual assembly code
-//! instructions, or it can be lowered to machine code.
-//! The main purpose of MIR is to postpone the assignment of offsets until Isel,
-//! so that, for example, the smaller encodings of jump instructions can be used.
-
-const Mir = @This();
-const std = @import("std");
-const builtin = @import("builtin");
-const assert = std.debug.assert;
-
-const bits = @import("bits.zig");
-const Register = bits.Register;
-const InternPool = @import("../../InternPool.zig");
-const Emit = @import("Emit.zig");
-const codegen = @import("../../codegen.zig");
-const link = @import("../../link.zig");
-const Zcu = @import("../../Zcu.zig");
-
-max_end_stack: u32,
-saved_regs_stack_space: u32,
-
-instructions: std.MultiArrayList(Inst).Slice,
-/// The meaning of this data is determined by `Inst.Tag` value.
-extra: []const u32,
-
-pub const Inst = struct {
-    tag: Tag,
-    cond: bits.Condition = .al,
-    /// The meaning of this depends on `tag`.
-    data: Data,
-
-    pub const Tag = enum(u16) {
-        /// Add
-        add,
-        /// Add, update condition flags
-        adds,
-        /// Bitwise AND
-        @"and",
-        /// Arithmetic Shift Right
-        asr,
-        /// Branch
-        b,
-        /// Undefined instruction
-        undefined_instruction,
-        /// Breakpoint
-        bkpt,
-        /// Branch with Link and Exchange
-        blx,
-        /// Branch and Exchange
-        bx,
-        /// Compare
-        cmp,
-        /// Pseudo-instruction: End of prologue
-        dbg_prologue_end,
-        /// Pseudo-instruction: Beginning of epilogue
-        dbg_epilogue_begin,
-        /// Pseudo-instruction: Update debug line
-        dbg_line,
-        /// Bitwise Exclusive OR
-        eor,
-        /// Load Register
-        ldr,
-        /// Pseudo-instruction: Load pointer to stack argument offset
-        ldr_ptr_stack_argument,
-        /// Load Register
-        ldr_stack_argument,
-        /// Load Register Byte
-        ldrb,
-        /// Load Register Byte
-        ldrb_stack_argument,
-        /// Load Register Halfword
-        ldrh,
-        /// Load Register Halfword
-        ldrh_stack_argument,
-        /// Load Register Signed Byte
-        ldrsb,
-        /// Load Register Signed Byte
-        ldrsb_stack_argument,
-        /// Load Register Signed Halfword
-        ldrsh,
-        /// Load Register Signed Halfword
-        ldrsh_stack_argument,
-        /// Logical Shift Left
-        lsl,
-        /// Logical Shift Right
-        lsr,
-        /// Move
-        mov,
-        /// Move
-        movw,
-        /// Move Top
-        movt,
-        /// Multiply
-        mul,
-        /// Bitwise NOT
-        mvn,
-        /// No Operation
-        nop,
-        /// Bitwise OR
-        orr,
-        /// Pop multiple registers from Stack
-        pop,
-        /// Push multiple registers to Stack
-        push,
-        /// Reverse Subtract
-        rsb,
-        /// Signed Bit Field Extract
-        sbfx,
-        /// Signed Multiply (halfwords), bottom half, bottom half
-        smulbb,
-        /// Signed Multiply Long
-        smull,
-        /// Store Register
-        str,
-        /// Store Register Byte
-        strb,
-        /// Store Register Halfword
-        strh,
-        /// Subtract
-        sub,
-        /// Pseudo-instruction: Subtract 32-bit immediate from stack
-        ///
-        /// r4 can be used by Emit as a scratch register for loading
-        /// the immediate
-        sub_sp_scratch_r4,
-        /// Subtract, update condition flags
-        subs,
-        /// Supervisor Call
-        svc,
-        /// Unsigned Bit Field Extract
-        ubfx,
-        /// Unsigned Multiply Long
-        umull,
-    };
-
-    /// The position of an MIR instruction within the `Mir` instructions array.
-    pub const Index = u32;
-
-    /// All instructions have a 8-byte payload, which is contained within
-    /// this union. `Tag` determines which union field is active, as well as
-    /// how to interpret the data within.
-    pub const Data = union {
-        /// No additional data
-        ///
-        /// Used by e.g. nop
-        nop: void,
-        /// Another instruction
-        ///
-        /// Used by e.g. b
-        inst: Index,
-        /// A 16-bit immediate value.
-        ///
-        /// Used by e.g. bkpt
-        imm16: u16,
-        /// A 24-bit immediate value.
-        ///
-        /// Used by e.g. svc
-        imm24: u24,
-        /// A 32-bit immediate value.
-        ///
-        /// Used by e.g. sub_sp_scratch_r0
-        imm32: u32,
-        /// Index into `extra`. Meaning of what can be found there is context-dependent.
-        ///
-        /// Used by e.g. load_memory
-        payload: u32,
-        /// A register
-        ///
-        /// Used by e.g. blx
-        reg: Register,
-        /// A register and a stack offset
-        ///
-        /// Used by e.g. ldr_stack_argument
-        r_stack_offset: struct {
-            rt: Register,
-            stack_offset: u32,
-        },
-        /// A register and a 16-bit unsigned immediate
-        ///
-        /// Used by e.g. movw
-        r_imm16: struct {
-            rd: Register,
-            imm16: u16,
-        },
-        /// A register and an operand
-        ///
-        /// Used by mov and mvn
-        r_op_mov: struct {
-            rd: Register,
-            op: bits.Instruction.Operand,
-        },
-        /// A register and an operand
-        ///
-        /// Used by cmp
-        r_op_cmp: struct {
-            rn: Register,
-            op: bits.Instruction.Operand,
-        },
-        /// Two registers and a shift amount
-        ///
-        /// Used by e.g. lsl
-        rr_shift: struct {
-            rd: Register,
-            rm: Register,
-            shift_amount: bits.Instruction.ShiftAmount,
-        },
-        /// Two registers and an operand
-        ///
-        /// Used by e.g. sub
-        rr_op: struct {
-            rd: Register,
-            rn: Register,
-            op: bits.Instruction.Operand,
-        },
-        /// Two registers and an offset
-        ///
-        /// Used by e.g. ldr
-        rr_offset: struct {
-            rt: Register,
-            rn: Register,
-            offset: bits.Instruction.OffsetArgs,
-        },
-        /// Two registers and an extra load/store offset
-        ///
-        /// Used by e.g. ldrh
-        rr_extra_offset: struct {
-            rt: Register,
-            rn: Register,
-            offset: bits.Instruction.ExtraLoadStoreOffsetArgs,
-        },
-        /// Two registers and a lsb (range 0-31) and a width (range
-        /// 1-32)
-        ///
-        /// Used by e.g. sbfx
-        rr_lsb_width: struct {
-            rd: Register,
-            rn: Register,
-            lsb: u5,
-            width: u6,
-        },
-        /// Three registers
-        ///
-        /// Used by e.g. mul
-        rrr: struct {
-            rd: Register,
-            rn: Register,
-            rm: Register,
-        },
-        /// Four registers
-        ///
-        /// Used by e.g. smull
-        rrrr: struct {
-            rdlo: Register,
-            rdhi: Register,
-            rn: Register,
-            rm: Register,
-        },
-        /// An unordered list of registers
-        ///
-        /// Used by e.g. push
-        register_list: bits.Instruction.RegisterList,
-        /// Debug info: line and column
-        ///
-        /// Used by e.g. dbg_line
-        dbg_line_column: struct {
-            line: u32,
-            column: u32,
-        },
-    };
-
-    // Make sure we don't accidentally make instructions bigger than expected.
-    // Note that in safety builds, Zig is allowed to insert a secret field for safety checks.
-    comptime {
-        if (!std.debug.runtime_safety) {
-            assert(@sizeOf(Data) == 8);
-        }
-    }
-};
-
-pub fn deinit(mir: *Mir, gpa: std.mem.Allocator) void {
-    mir.instructions.deinit(gpa);
-    gpa.free(mir.extra);
-    mir.* = undefined;
-}
-
-pub fn emit(
-    mir: Mir,
-    lf: *link.File,
-    pt: Zcu.PerThread,
-    src_loc: Zcu.LazySrcLoc,
-    func_index: InternPool.Index,
-    code: *std.ArrayListUnmanaged(u8),
-    debug_output: link.File.DebugInfoOutput,
-) codegen.CodeGenError!void {
-    const zcu = pt.zcu;
-    const func = zcu.funcInfo(func_index);
-    const nav = func.owner_nav;
-    const mod = zcu.navFileScope(nav).mod.?;
-    var e: Emit = .{
-        .mir = mir,
-        .bin_file = lf,
-        .debug_output = debug_output,
-        .target = &mod.resolved_target.result,
-        .src_loc = src_loc,
-        .code = code,
-        .prev_di_pc = 0,
-        .prev_di_line = func.lbrace_line,
-        .prev_di_column = func.lbrace_column,
-        .stack_size = mir.max_end_stack,
-        .saved_regs_stack_space = mir.saved_regs_stack_space,
-    };
-    defer e.deinit();
-    e.emitMir() catch |err| switch (err) {
-        error.EmitFail => return zcu.codegenFailMsg(nav, e.err_msg.?),
-        else => |e1| return e1,
-    };
-}
-
-/// Returns the requested data, as well as the new index which is at the start of the
-/// trailers for the object.
-pub fn extraData(mir: Mir, comptime T: type, index: usize) struct { data: T, end: usize } {
-    const fields = std.meta.fields(T);
-    var i: usize = index;
-    var result: T = undefined;
-    inline for (fields) |field| {
-        @field(result, field.name) = switch (field.type) {
-            u32 => mir.extra[i],
-            i32 => @as(i32, @bitCast(mir.extra[i])),
-            else => @compileError("bad field type"),
-        };
-        i += 1;
-    }
-    return .{
-        .data = result,
-        .end = i,
-    };
-}
src/arch/arm/abi.zig → src/codegen/arm/abi.zig
@@ -1,7 +1,5 @@
 const std = @import("std");
 const assert = std.debug.assert;
-const bits = @import("bits.zig");
-const Register = bits.Register;
 const RegisterManagerFn = @import("../../register_manager.zig").RegisterManager;
 const Type = @import("../../Type.zig");
 const Zcu = @import("../../Zcu.zig");
@@ -163,25 +161,3 @@ fn countFloats(ty: Type, zcu: *Zcu, maybe_float_bits: *?u16) u32 {
         else => return invalid,
     }
 }
-
-pub const callee_preserved_regs = [_]Register{ .r4, .r5, .r6, .r7, .r8, .r10 };
-pub const caller_preserved_regs = [_]Register{ .r0, .r1, .r2, .r3 };
-
-pub const c_abi_int_param_regs = [_]Register{ .r0, .r1, .r2, .r3 };
-pub const c_abi_int_return_regs = [_]Register{ .r0, .r1 };
-
-const allocatable_registers = callee_preserved_regs ++ caller_preserved_regs;
-pub const RegisterManager = RegisterManagerFn(@import("CodeGen.zig"), Register, &allocatable_registers);
-
-// Register classes
-const RegisterBitSet = RegisterManager.RegisterBitSet;
-pub const RegisterClass = struct {
-    pub const gp: RegisterBitSet = blk: {
-        var set = RegisterBitSet.initEmpty();
-        set.setRangeValue(.{
-            .start = 0,
-            .end = caller_preserved_regs.len + callee_preserved_regs.len,
-        }, true);
-        break :blk set;
-    };
-};
src/codegen/llvm.zig
@@ -23,7 +23,7 @@ const Type = @import("../Type.zig");
 const x86_64_abi = @import("../arch/x86_64/abi.zig");
 const wasm_c_abi = @import("../arch/wasm/abi.zig");
 const aarch64_c_abi = @import("aarch64/abi.zig");
-const arm_c_abi = @import("../arch/arm/abi.zig");
+const arm_c_abi = @import("arm/abi.zig");
 const riscv_c_abi = @import("../arch/riscv64/abi.zig");
 const mips_c_abi = @import("../arch/mips/abi.zig");
 const dev = @import("../dev.zig");
src/codegen.zig
@@ -49,7 +49,7 @@ fn importBackend(comptime backend: std.builtin.CompilerBackend) type {
     return switch (backend) {
         .other, .stage1 => unreachable,
         .stage2_aarch64 => unreachable,
-        .stage2_arm => @import("arch/arm/CodeGen.zig"),
+        .stage2_arm => unreachable,
         .stage2_c => @import("codegen/c.zig"),
         .stage2_llvm => @import("codegen/llvm.zig"),
         .stage2_powerpc => unreachable,
@@ -70,7 +70,6 @@ pub fn legalizeFeatures(pt: Zcu.PerThread, nav_index: InternPool.Nav.Index) ?*co
         inline .stage2_llvm,
         .stage2_c,
         .stage2_wasm,
-        .stage2_arm,
         .stage2_x86_64,
         .stage2_x86,
         .stage2_riscv64,
@@ -87,7 +86,6 @@ pub fn legalizeFeatures(pt: Zcu.PerThread, nav_index: InternPool.Nav.Index) ?*co
 /// MIR from codegen to the linker *regardless* of which backend is in use. So, we use this: a
 /// union of all MIR types. The active tag is known from the backend in use; see `AnyMir.tag`.
 pub const AnyMir = union {
-    arm: @import("arch/arm/Mir.zig"),
     riscv64: @import("arch/riscv64/Mir.zig"),
     sparc64: @import("arch/sparc64/Mir.zig"),
     x86_64: @import("arch/x86_64/Mir.zig"),
@@ -112,8 +110,7 @@ pub const AnyMir = union {
         const backend = target_util.zigBackend(&zcu.root_mod.resolved_target.result, zcu.comp.config.use_llvm);
         switch (backend) {
             else => unreachable,
-            inline .stage2_arm,
-            .stage2_riscv64,
+            inline .stage2_riscv64,
             .stage2_sparc64,
             .stage2_x86_64,
             .stage2_wasm,
@@ -141,8 +138,7 @@ pub fn generateFunction(
     const target = &zcu.navFileScope(func.owner_nav).mod.?.resolved_target.result;
     switch (target_util.zigBackend(target, false)) {
         else => unreachable,
-        inline .stage2_arm,
-        .stage2_riscv64,
+        inline .stage2_riscv64,
         .stage2_sparc64,
         .stage2_x86_64,
         .stage2_wasm,
@@ -177,8 +173,7 @@ pub fn emitFunction(
     const target = &zcu.navFileScope(func.owner_nav).mod.?.resolved_target.result;
     switch (target_util.zigBackend(target, zcu.comp.config.use_llvm)) {
         else => unreachable,
-        inline .stage2_arm,
-        .stage2_riscv64,
+        inline .stage2_riscv64,
         .stage2_sparc64,
         .stage2_x86_64,
         => |backend| {
CMakeLists.txt
@@ -549,11 +549,6 @@ set(ZIG_STAGE2_SOURCES
     src/Value.zig
     src/Zcu.zig
     src/Zcu/PerThread.zig
-    src/arch/arm/CodeGen.zig
-    src/arch/arm/Emit.zig
-    src/arch/arm/Mir.zig
-    src/arch/arm/abi.zig
-    src/arch/arm/bits.zig
     src/arch/riscv64/abi.zig
     src/arch/riscv64/bits.zig
     src/arch/riscv64/CodeGen.zig