Commit 1fecf86ebf

Jacob Young <jacobly0@users.noreply.github.com>
2023-10-29 02:06:32
x86_64: refactor codegen memory repr
Also refactor linker reloc lowering.
1 parent 20ade4c
src/arch/x86_64/bits.zig
@@ -181,6 +181,8 @@ pub const Register = enum(u7) {
 
     es, cs, ss, ds, fs, gs,
 
+    rip, eip, ip,
+
     none,
     // zig fmt: on
 
@@ -442,34 +444,58 @@ pub const FrameIndex = enum(u32) {
     }
 };
 
-pub const Memory = union(enum) {
-    sib: Sib,
-    rip: Rip,
-    moffs: Moffs,
+/// A linker symbol not yet allocated in VM.
+pub const Symbol = struct {
+    /// Index of the containing atom.
+    atom_index: u32,
+    /// Index into the linker's symbol table.
+    sym_index: u32,
+
+    pub fn format(
+        sym: Symbol,
+        comptime fmt: []const u8,
+        options: std.fmt.FormatOptions,
+        writer: anytype,
+    ) @TypeOf(writer).Error!void {
+        try writer.writeAll("Symbol(");
+        try std.fmt.formatType(sym.atom_index, fmt, options, writer, 0);
+        try writer.writeAll(", ");
+        try std.fmt.formatType(sym.sym_index, fmt, options, writer, 0);
+        try writer.writeByte(')');
+    }
+};
+
+pub const Memory = struct {
+    base: Base,
+    mod: Mod,
 
-    pub const Base = union(enum) {
+    pub const Base = union(enum(u2)) {
         none,
         reg: Register,
         frame: FrameIndex,
+        reloc: Symbol,
 
         pub const Tag = @typeInfo(Base).Union.tag_type.?;
 
         pub fn isExtended(self: Base) bool {
             return switch (self) {
-                .none, .frame => false, // neither rsp nor rbp are extended
+                .none, .frame, .reloc => false, // rsp, rbp, and rip are not extended
                 .reg => |reg| reg.isExtended(),
             };
         }
     };
 
-    pub const ScaleIndex = struct {
-        scale: u4,
-        index: Register,
-
-        const none = ScaleIndex{ .scale = 0, .index = undefined };
+    pub const Mod = union(enum(u1)) {
+        rm: struct {
+            size: Size,
+            index: Register = .none,
+            scale: Scale = .@"1",
+            disp: i32 = 0,
+        },
+        off: u64,
     };
 
-    pub const PtrSize = enum {
+    pub const Size = enum(u4) {
         none,
         byte,
         word,
@@ -480,7 +506,7 @@ pub const Memory = union(enum) {
         yword,
         zword,
 
-        pub fn fromSize(size: u32) PtrSize {
+        pub fn fromSize(size: u32) Size {
             return switch (size) {
                 1...1 => .byte,
                 2...2 => .word,
@@ -493,7 +519,7 @@ pub const Memory = union(enum) {
             };
         }
 
-        pub fn fromBitSize(bit_size: u64) PtrSize {
+        pub fn fromBitSize(bit_size: u64) Size {
             return switch (bit_size) {
                 8 => .byte,
                 16 => .word,
@@ -507,7 +533,7 @@ pub const Memory = union(enum) {
             };
         }
 
-        pub fn bitSize(s: PtrSize) u64 {
+        pub fn bitSize(s: Size) u64 {
             return switch (s) {
                 .none => 0,
                 .byte => 8,
@@ -522,7 +548,7 @@ pub const Memory = union(enum) {
         }
 
         pub fn format(
-            s: PtrSize,
+            s: Size,
             comptime _: []const u8,
             _: std.fmt.FormatOptions,
             writer: anytype,
@@ -533,79 +559,7 @@ pub const Memory = union(enum) {
         }
     };
 
-    pub const Sib = struct {
-        ptr_size: PtrSize,
-        base: Base,
-        scale_index: ScaleIndex,
-        disp: i32,
-    };
-
-    pub const Rip = struct {
-        ptr_size: PtrSize,
-        disp: i32,
-    };
-
-    pub const Moffs = struct {
-        seg: Register,
-        offset: u64,
-    };
-
-    pub fn moffs(reg: Register, offset: u64) Memory {
-        assert(reg.class() == .segment);
-        return .{ .moffs = .{ .seg = reg, .offset = offset } };
-    }
-
-    pub fn sib(ptr_size: PtrSize, args: struct {
-        disp: i32 = 0,
-        base: Base = .none,
-        scale_index: ?ScaleIndex = null,
-    }) Memory {
-        if (args.scale_index) |si| assert(std.math.isPowerOfTwo(si.scale));
-        return .{ .sib = .{
-            .base = args.base,
-            .disp = args.disp,
-            .ptr_size = ptr_size,
-            .scale_index = if (args.scale_index) |si| si else ScaleIndex.none,
-        } };
-    }
-
-    pub fn rip(ptr_size: PtrSize, disp: i32) Memory {
-        return .{ .rip = .{ .ptr_size = ptr_size, .disp = disp } };
-    }
-
-    pub fn isSegmentRegister(mem: Memory) bool {
-        return switch (mem) {
-            .moffs => true,
-            .rip => false,
-            .sib => |s| switch (s.base) {
-                .none, .frame => false,
-                .reg => |reg| reg.class() == .segment,
-            },
-        };
-    }
-
-    pub fn base(mem: Memory) Base {
-        return switch (mem) {
-            .moffs => |m| .{ .reg = m.seg },
-            .sib => |s| s.base,
-            .rip => .none,
-        };
-    }
-
-    pub fn scaleIndex(mem: Memory) ?ScaleIndex {
-        return switch (mem) {
-            .moffs, .rip => null,
-            .sib => |s| if (s.scale_index.scale > 0) s.scale_index else null,
-        };
-    }
-
-    pub fn bitSize(mem: Memory) u64 {
-        return switch (mem) {
-            .rip => |r| r.ptr_size.bitSize(),
-            .sib => |s| s.ptr_size.bitSize(),
-            .moffs => 64,
-        };
-    }
+    pub const Scale = enum(u2) { @"1", @"2", @"4", @"8" };
 };
 
 pub const Immediate = union(enum) {
src/arch/x86_64/CodeGen.zig
@@ -115,6 +115,7 @@ const mir_to_air_map_init = if (builtin.mode == .Debug) std.AutoHashMapUnmanaged
 
 const FrameAddr = struct { index: FrameIndex, off: i32 = 0 };
 const RegisterOffset = struct { reg: Register, off: i32 = 0 };
+const SymbolOffset = struct { sym: u32, off: i32 = 0 };
 
 const Owner = union(enum) {
     func_index: InternPool.Index,
@@ -195,9 +196,9 @@ pub const MCValue = union(enum) {
     memory: u64,
     /// The value is in memory at an address not-yet-allocated by the linker.
     /// This traditionally corresponds to a relocation emitted in a relocatable object file.
-    load_symbol: u32,
+    load_symbol: SymbolOffset,
     /// The address of the memory location not-yet-allocated by the linker.
-    lea_symbol: u32,
+    lea_symbol: SymbolOffset,
     /// The value is in memory at a constant offset from the address in a register.
     indirect: RegisterOffset,
     /// The value is in memory.
@@ -315,7 +316,7 @@ pub const MCValue = union(enum) {
             .load_got => |sym_index| .{ .lea_got = sym_index },
             .load_tlv => |sym_index| .{ .lea_tlv = sym_index },
             .load_frame => |frame_addr| .{ .lea_frame = frame_addr },
-            .load_symbol => |sym_index| .{ .lea_symbol = sym_index },
+            .load_symbol => |sym_off| .{ .lea_symbol = sym_off },
         };
     }
 
@@ -387,7 +388,7 @@ pub const MCValue = union(enum) {
         };
     }
 
-    fn mem(mcv: MCValue, ptr_size: Memory.PtrSize) Memory {
+    fn mem(mcv: MCValue, size: Memory.Size) Memory {
         return switch (mcv) {
             .none,
             .unreach,
@@ -411,18 +412,27 @@ pub const MCValue = union(enum) {
             .load_symbol,
             .lea_symbol,
             => unreachable,
-            .memory => |addr| if (math.cast(i32, @as(i64, @bitCast(addr)))) |small_addr|
-                Memory.sib(ptr_size, .{ .base = .{ .reg = .ds }, .disp = small_addr })
-            else
-                Memory.moffs(.ds, addr),
-            .indirect => |reg_off| Memory.sib(ptr_size, .{
+            .memory => |addr| if (math.cast(i32, @as(i64, @bitCast(addr)))) |small_addr| .{
+                .base = .{ .reg = .ds },
+                .mod = .{ .rm = .{
+                    .size = size,
+                    .disp = small_addr,
+                } },
+            } else .{ .base = .{ .reg = .ds }, .mod = .{ .off = addr } },
+            .indirect => |reg_off| .{
                 .base = .{ .reg = reg_off.reg },
-                .disp = reg_off.off,
-            }),
-            .load_frame => |frame_addr| Memory.sib(ptr_size, .{
+                .mod = .{ .rm = .{
+                    .size = size,
+                    .disp = reg_off.off,
+                } },
+            },
+            .load_frame => |frame_addr| .{
                 .base = .{ .frame = frame_addr.index },
-                .disp = frame_addr.off,
-            }),
+                .mod = .{ .rm = .{
+                    .size = size,
+                    .disp = frame_addr.off,
+                } },
+            },
         };
     }
 
@@ -442,6 +452,8 @@ pub const MCValue = union(enum) {
             .register_overflow => |pl| try writer.print("{s}:{s}", .{
                 @tagName(pl.eflags), @tagName(pl.reg),
             }),
+            .load_symbol => |pl| try writer.print("[{} + 0x{x}]", .{ pl.sym, pl.off }),
+            .lea_symbol => |pl| try writer.print("{} + 0x{x}", .{ pl.sym, pl.off }),
             .indirect => |pl| try writer.print("[{s} + 0x{x}]", .{ @tagName(pl.reg), pl.off }),
             .load_direct => |pl| try writer.print("[direct:{d}]", .{pl}),
             .lea_direct => |pl| try writer.print("direct:{d}", .{pl}),
@@ -453,8 +465,6 @@ pub const MCValue = union(enum) {
             .lea_frame => |pl| try writer.print("{} + 0x{x}", .{ pl.index, pl.off }),
             .reserved_frame => |pl| try writer.print("(dead:{})", .{pl}),
             .air_ref => |pl| try writer.print("(air:0x{x})", .{@intFromEnum(pl)}),
-            .load_symbol => |pl| try writer.print("[symbol:{d}]", .{pl}),
-            .lea_symbol => |pl| try writer.print("symbol:{d}", .{pl}),
         }
     }
 };
@@ -888,7 +898,6 @@ pub fn generate(
             .cc = cc,
             .src_loc = src_loc,
         },
-        .bin_file = bin_file,
         .debug_output = debug_output,
         .code = code,
         .prev_di_pc = 0,
@@ -976,7 +985,6 @@ pub fn generateLazy(
             .cc = abi.resolveCallingConvention(.Unspecified, function.target.*),
             .src_loc = src_loc,
         },
-        .bin_file = bin_file,
         .debug_output = debug_output,
         .code = code,
         .prev_di_pc = undefined, // no debug info yet
@@ -1139,7 +1147,7 @@ fn addExtraAssumeCapacity(self: *Self, extra: anytype) u32 {
     inline for (fields) |field| {
         self.mir_extra.appendAssumeCapacity(switch (field.type) {
             u32 => @field(extra, field.name),
-            i32 => @bitCast(@field(extra, field.name)),
+            i32, Mir.Memory.Info => @bitCast(@field(extra, field.name)),
             else => @compileError("bad field type: " ++ field.name ++ ": " ++ @typeName(field.type)),
         });
     }
@@ -1178,17 +1186,9 @@ fn asmCmovccRegisterMemory(self: *Self, cc: Condition, reg: Register, m: Memory)
             .nz_or_p => .pseudo,
         },
         .ops = switch (cc) {
-            else => switch (m) {
-                .sib => .rm_sib,
-                .rip => .rm_rip,
-                else => unreachable,
-            },
+            else => .rm,
             .z_and_np => unreachable,
-            .nz_or_p => switch (m) {
-                .sib => .pseudo_cmov_nz_or_p_rm_sib,
-                .rip => .pseudo_cmov_nz_or_p_rm_rip,
-                else => unreachable,
-            },
+            .nz_or_p => .pseudo_cmov_nz_or_p_rm,
         },
         .data = .{ .rx = .{
             .fixes = switch (cc) {
@@ -1197,11 +1197,7 @@ fn asmCmovccRegisterMemory(self: *Self, cc: Condition, reg: Register, m: Memory)
                 .nz_or_p => ._,
             },
             .r1 = reg,
-            .payload = switch (m) {
-                .sib => try self.addExtra(Mir.MemorySib.encode(m)),
-                .rip => try self.addExtra(Mir.MemoryRip.encode(m)),
-                else => unreachable,
-            },
+            .payload = try self.addExtra(Mir.Memory.encode(m)),
         } },
     });
 }
@@ -1231,32 +1227,16 @@ fn asmSetccRegister(self: *Self, cc: Condition, reg: Register) !void {
 }
 
 fn asmSetccMemory(self: *Self, cc: Condition, m: Memory) !void {
-    const payload = switch (m) {
-        .sib => try self.addExtra(Mir.MemorySib.encode(m)),
-        .rip => try self.addExtra(Mir.MemoryRip.encode(m)),
-        else => unreachable,
-    };
+    const payload = try self.addExtra(Mir.Memory.encode(m));
     _ = try self.addInst(.{
         .tag = switch (cc) {
             else => .set,
             .z_and_np, .nz_or_p => .pseudo,
         },
         .ops = switch (cc) {
-            else => switch (m) {
-                .sib => .m_sib,
-                .rip => .m_rip,
-                else => unreachable,
-            },
-            .z_and_np => switch (m) {
-                .sib => .pseudo_set_z_and_np_m_sib,
-                .rip => .pseudo_set_z_and_np_m_rip,
-                else => unreachable,
-            },
-            .nz_or_p => switch (m) {
-                .sib => .pseudo_set_nz_or_p_m_sib,
-                .rip => .pseudo_set_nz_or_p_m_rip,
-                else => unreachable,
-            },
+            else => .m,
+            .z_and_np => .pseudo_set_z_and_np_m,
+            .nz_or_p => .pseudo_set_nz_or_p_m,
         },
         .data = switch (cc) {
             else => .{ .x = .{
@@ -1504,20 +1484,12 @@ fn asmRegisterRegisterMemory(
 ) !void {
     _ = try self.addInst(.{
         .tag = tag[1],
-        .ops = switch (m) {
-            .sib => .rrm_sib,
-            .rip => .rrm_rip,
-            else => unreachable,
-        },
+        .ops = .rrm,
         .data = .{ .rrx = .{
             .fixes = tag[0],
             .r1 = reg1,
             .r2 = reg2,
-            .payload = switch (m) {
-                .sib => try self.addExtra(Mir.MemorySib.encode(m)),
-                .rip => try self.addExtra(Mir.MemoryRip.encode(m)),
-                else => unreachable,
-            },
+            .payload = try self.addExtra(Mir.Memory.encode(m)),
         } },
     });
 }
@@ -1525,18 +1497,10 @@ fn asmRegisterRegisterMemory(
 fn asmMemory(self: *Self, tag: Mir.Inst.FixedTag, m: Memory) !void {
     _ = try self.addInst(.{
         .tag = tag[1],
-        .ops = switch (m) {
-            .sib => .m_sib,
-            .rip => .m_rip,
-            else => unreachable,
-        },
+        .ops = .m,
         .data = .{ .x = .{
             .fixes = tag[0],
-            .payload = switch (m) {
-                .sib => try self.addExtra(Mir.MemorySib.encode(m)),
-                .rip => try self.addExtra(Mir.MemoryRip.encode(m)),
-                else => unreachable,
-            },
+            .payload = try self.addExtra(Mir.Memory.encode(m)),
         } },
     });
 }
@@ -1544,19 +1508,11 @@ fn asmMemory(self: *Self, tag: Mir.Inst.FixedTag, m: Memory) !void {
 fn asmRegisterMemory(self: *Self, tag: Mir.Inst.FixedTag, reg: Register, m: Memory) !void {
     _ = try self.addInst(.{
         .tag = tag[1],
-        .ops = switch (m) {
-            .sib => .rm_sib,
-            .rip => .rm_rip,
-            else => unreachable,
-        },
+        .ops = .rm,
         .data = .{ .rx = .{
             .fixes = tag[0],
             .r1 = reg,
-            .payload = switch (m) {
-                .sib => try self.addExtra(Mir.MemorySib.encode(m)),
-                .rip => try self.addExtra(Mir.MemoryRip.encode(m)),
-                else => unreachable,
-            },
+            .payload = try self.addExtra(Mir.Memory.encode(m)),
         } },
     });
 }
@@ -1574,20 +1530,12 @@ fn asmRegisterMemoryImmediate(
     }) |small_imm| {
         _ = try self.addInst(.{
             .tag = tag[1],
-            .ops = switch (m) {
-                .sib => .rmi_sib,
-                .rip => .rmi_rip,
-                else => unreachable,
-            },
+            .ops = .rmi,
             .data = .{ .rix = .{
                 .fixes = tag[0],
                 .r1 = reg,
                 .i = small_imm,
-                .payload = switch (m) {
-                    .sib => try self.addExtra(Mir.MemorySib.encode(m)),
-                    .rip => try self.addExtra(Mir.MemoryRip.encode(m)),
-                    else => unreachable,
-                },
+                .payload = try self.addExtra(Mir.Memory.encode(m)),
             } },
         });
     } else {
@@ -1595,23 +1543,12 @@ fn asmRegisterMemoryImmediate(
             .signed => |s| @bitCast(s),
             .unsigned => unreachable,
         } });
-        assert(payload + 1 == switch (m) {
-            .sib => try self.addExtra(Mir.MemorySib.encode(m)),
-            .rip => try self.addExtra(Mir.MemoryRip.encode(m)),
-            else => unreachable,
-        });
+        assert(payload + 1 == try self.addExtra(Mir.Memory.encode(m)));
         _ = try self.addInst(.{
             .tag = tag[1],
-            .ops = switch (m) {
-                .sib => switch (imm) {
-                    .signed => .rmi_sib_s,
-                    .unsigned => .rmi_sib_u,
-                },
-                .rip => switch (imm) {
-                    .signed => .rmi_rip_s,
-                    .unsigned => .rmi_rip_u,
-                },
-                else => unreachable,
+            .ops = switch (imm) {
+                .signed => .rmi_s,
+                .unsigned => .rmi_u,
             },
             .data = .{ .rx = .{
                 .fixes = tag[0],
@@ -1632,21 +1569,13 @@ fn asmRegisterRegisterMemoryImmediate(
 ) !void {
     _ = try self.addInst(.{
         .tag = tag[1],
-        .ops = switch (m) {
-            .sib => .rrmi_sib,
-            .rip => .rrmi_rip,
-            else => unreachable,
-        },
+        .ops = .rrmi,
         .data = .{ .rrix = .{
             .fixes = tag[0],
             .r1 = reg1,
             .r2 = reg2,
             .i = @intCast(imm.unsigned),
-            .payload = switch (m) {
-                .sib => try self.addExtra(Mir.MemorySib.encode(m)),
-                .rip => try self.addExtra(Mir.MemoryRip.encode(m)),
-                else => unreachable,
-            },
+            .payload = try self.addExtra(Mir.Memory.encode(m)),
         } },
     });
 }
@@ -1654,19 +1583,11 @@ fn asmRegisterRegisterMemoryImmediate(
 fn asmMemoryRegister(self: *Self, tag: Mir.Inst.FixedTag, m: Memory, reg: Register) !void {
     _ = try self.addInst(.{
         .tag = tag[1],
-        .ops = switch (m) {
-            .sib => .mr_sib,
-            .rip => .mr_rip,
-            else => unreachable,
-        },
+        .ops = .mr,
         .data = .{ .rx = .{
             .fixes = tag[0],
             .r1 = reg,
-            .payload = switch (m) {
-                .sib => try self.addExtra(Mir.MemorySib.encode(m)),
-                .rip => try self.addExtra(Mir.MemoryRip.encode(m)),
-                else => unreachable,
-            },
+            .payload = try self.addExtra(Mir.Memory.encode(m)),
         } },
     });
 }
@@ -1676,23 +1597,12 @@ fn asmMemoryImmediate(self: *Self, tag: Mir.Inst.FixedTag, m: Memory, imm: Immed
         .signed => |s| @bitCast(s),
         .unsigned => |u| @intCast(u),
     } });
-    assert(payload + 1 == switch (m) {
-        .sib => try self.addExtra(Mir.MemorySib.encode(m)),
-        .rip => try self.addExtra(Mir.MemoryRip.encode(m)),
-        else => unreachable,
-    });
+    assert(payload + 1 == try self.addExtra(Mir.Memory.encode(m)));
     _ = try self.addInst(.{
         .tag = tag[1],
-        .ops = switch (m) {
-            .sib => switch (imm) {
-                .signed => .mi_sib_s,
-                .unsigned => .mi_sib_u,
-            },
-            .rip => switch (imm) {
-                .signed => .mi_rip_s,
-                .unsigned => .mi_rip_u,
-            },
-            else => unreachable,
+        .ops = switch (imm) {
+            .signed => .mi_s,
+            .unsigned => .mi_u,
         },
         .data = .{ .x = .{
             .fixes = tag[0],
@@ -1710,20 +1620,12 @@ fn asmMemoryRegisterRegister(
 ) !void {
     _ = try self.addInst(.{
         .tag = tag[1],
-        .ops = switch (m) {
-            .sib => .mrr_sib,
-            .rip => .mrr_rip,
-            else => unreachable,
-        },
+        .ops = .mrr,
         .data = .{ .rrx = .{
             .fixes = tag[0],
             .r1 = reg1,
             .r2 = reg2,
-            .payload = switch (m) {
-                .sib => try self.addExtra(Mir.MemorySib.encode(m)),
-                .rip => try self.addExtra(Mir.MemoryRip.encode(m)),
-                else => unreachable,
-            },
+            .payload = try self.addExtra(Mir.Memory.encode(m)),
         } },
     });
 }
@@ -1737,20 +1639,12 @@ fn asmMemoryRegisterImmediate(
 ) !void {
     _ = try self.addInst(.{
         .tag = tag[1],
-        .ops = switch (m) {
-            .sib => .mri_sib,
-            .rip => .mri_rip,
-            else => unreachable,
-        },
+        .ops = .mri,
         .data = .{ .rix = .{
             .fixes = tag[0],
             .r1 = reg,
             .i = @intCast(imm.unsigned),
-            .payload = switch (m) {
-                .sib => try self.addExtra(Mir.MemorySib.encode(m)),
-                .rip => try self.addExtra(Mir.MemoryRip.encode(m)),
-                else => unreachable,
-            },
+            .payload = try self.addExtra(Mir.Memory.encode(m)),
         } },
     });
 }
@@ -1916,13 +1810,16 @@ fn gen(self: *Self) InnerError!void {
         if (need_frame_align or need_stack_adjust) {
             self.mir_instructions.set(backpatch_stack_dealloc, .{
                 .tag = .lea,
-                .ops = .rm_sib,
+                .ops = .rm,
                 .data = .{ .rx = .{
                     .r1 = .rsp,
-                    .payload = try self.addExtra(Mir.MemorySib.encode(Memory.sib(.qword, .{
+                    .payload = try self.addExtra(Mir.Memory.encode(.{
                         .base = .{ .reg = .rbp },
-                        .disp = -frame_layout.save_reg_list.size(),
-                    }))),
+                        .mod = .{ .rm = .{
+                            .size = .qword,
+                            .disp = -frame_layout.save_reg_list.size(),
+                        } },
+                    })),
                 } },
             });
         }
@@ -3098,14 +2995,14 @@ fn airTrunc(self: *Self, inst: Air.Inst.Index) !void {
                     .{ .vp_, .@"and" },
                     dst_reg,
                     dst_reg,
-                    splat_addr_mcv.deref().mem(Memory.PtrSize.fromSize(splat_abi_size)),
+                    splat_addr_mcv.deref().mem(Memory.Size.fromSize(splat_abi_size)),
                 );
                 try self.asmRegisterRegisterRegister(mir_tag, dst_reg, dst_reg, dst_reg);
             } else {
                 try self.asmRegisterMemory(
                     .{ .p_, .@"and" },
                     dst_reg,
-                    splat_addr_mcv.deref().mem(Memory.PtrSize.fromSize(splat_abi_size)),
+                    splat_addr_mcv.deref().mem(Memory.Size.fromSize(splat_abi_size)),
                 );
                 try self.asmRegisterRegister(mir_tag, dst_reg, dst_reg);
             }
@@ -3254,7 +3151,7 @@ fn airMulDivBinOp(self: *Self, inst: Air.Inst.Index) !void {
                     const frame_index = try self.allocFrameIndex(FrameAlloc.initType(Type.usize, mod));
                     try self.asmMemoryImmediate(
                         .{ ._, .mov },
-                        Memory.sib(.qword, .{ .base = .{ .frame = frame_index } }),
+                        .{ .base = .{ .frame = frame_index }, .mod = .{ .rm = .{ .size = .qword } } },
                         Immediate.u(0),
                     );
 
@@ -3338,9 +3235,10 @@ fn airMulDivBinOp(self: *Self, inst: Air.Inst.Index) !void {
                             call_mcv.register_pair[0],
                             call_mcv.register_pair[1],
                         );
-                        try self.asmSetccMemory(.nz, Memory.sib(.byte, .{
+                        try self.asmSetccMemory(.nz, .{
                             .base = .{ .frame = signed_div_floor_state.frame_index },
-                        }));
+                            .mod = .{ .rm = .{ .size = .byte } },
+                        });
                         try self.performReloc(signed_div_floor_state.reloc);
                         const dst_mcv = try self.genCall(
                             .{ .lib = .{
@@ -3356,9 +3254,10 @@ fn airMulDivBinOp(self: *Self, inst: Air.Inst.Index) !void {
                         try self.asmRegisterMemory(
                             .{ ._, .sub },
                             dst_mcv.register_pair[0],
-                            Memory.sib(.qword, .{
+                            .{
                                 .base = .{ .frame = signed_div_floor_state.frame_index },
-                            }),
+                                .mod = .{ .rm = .{ .size = .qword } },
+                            },
                         );
                         try self.asmRegisterImmediate(
                             .{ ._, .sbb },
@@ -3891,7 +3790,7 @@ fn airMulWithOverflow(self: *Self, inst: Air.Inst.Index) !void {
                     );
                     try self.asmMemoryImmediate(
                         .{ ._, .cmp },
-                        overflow.mem(self.memPtrSize(Type.c_int)),
+                        overflow.mem(self.memSize(Type.c_int)),
                         Immediate.s(0),
                     );
                     try self.genSetMem(
@@ -4123,7 +4022,7 @@ fn genIntMulDivOpMir(self: *Self, tag: Mir.Inst.FixedTag, ty: Type, lhs: MCValue
         .register => |reg| try self.asmRegister(tag, registerAlias(reg, abi_size)),
         .memory, .indirect, .load_frame => try self.asmMemory(
             tag,
-            mat_rhs.mem(Memory.PtrSize.fromSize(abi_size)),
+            mat_rhs.mem(Memory.Size.fromSize(abi_size)),
         ),
         else => unreachable,
     }
@@ -4360,10 +4259,13 @@ fn airUnwrapErrUnionErrPtr(self: *Self, inst: Air.Inst.Index) !void {
     try self.asmRegisterMemory(
         .{ ._, .mov },
         registerAlias(dst_reg, err_abi_size),
-        Memory.sib(Memory.PtrSize.fromSize(err_abi_size), .{
+        .{
             .base = .{ .reg = src_reg },
-            .disp = err_off,
-        }),
+            .mod = .{ .rm = .{
+                .size = Memory.Size.fromSize(err_abi_size),
+                .disp = err_off,
+            } },
+        },
     );
 
     return self.finishAir(inst, dst_mcv, .{ ty_op.operand, .none, .none });
@@ -4398,10 +4300,13 @@ fn airErrUnionPayloadPtrSet(self: *Self, inst: Air.Inst.Index) !void {
         const err_abi_size: u32 = @intCast(err_ty.abiSize(mod));
         try self.asmMemoryImmediate(
             .{ ._, .mov },
-            Memory.sib(Memory.PtrSize.fromSize(err_abi_size), .{
+            .{
                 .base = .{ .reg = src_reg },
-                .disp = err_off,
-            }),
+                .mod = .{ .rm = .{
+                    .size = Memory.Size.fromSize(err_abi_size),
+                    .disp = err_off,
+                } },
+            },
             Immediate.u(0),
         );
 
@@ -4420,7 +4325,10 @@ fn airErrUnionPayloadPtrSet(self: *Self, inst: Air.Inst.Index) !void {
         try self.asmRegisterMemory(
             .{ ._, .lea },
             registerAlias(dst_reg, dst_abi_size),
-            Memory.sib(.qword, .{ .base = .{ .reg = src_reg }, .disp = pl_off }),
+            .{
+                .base = .{ .reg = src_reg },
+                .mod = .{ .rm = .{ .size = .qword, .disp = pl_off } },
+            },
         );
         break :result .{ .register = dst_reg };
     };
@@ -4542,10 +4450,13 @@ fn airWrapOptional(self: *Self, inst: Air.Inst.Index) !void {
 
                 .load_frame => |frame_addr| try self.asmMemoryImmediate(
                     .{ ._, .mov },
-                    Memory.sib(.byte, .{
+                    .{
                         .base = .{ .frame = frame_addr.index },
-                        .disp = frame_addr.off + pl_abi_size,
-                    }),
+                        .mod = .{ .rm = .{
+                            .size = .byte,
+                            .disp = frame_addr.off + pl_abi_size,
+                        } },
+                    },
                     Immediate.u(1),
                 ),
             }
@@ -4658,10 +4569,10 @@ fn airPtrSliceLenPtr(self: *Self, inst: Air.Inst.Index) !void {
     try self.asmRegisterMemory(
         .{ ._, .lea },
         registerAlias(dst_reg, dst_abi_size),
-        Memory.sib(.qword, .{
+        .{
             .base = .{ .reg = src_reg },
-            .disp = @divExact(self.target.ptrBitWidth(), 8),
-        }),
+            .mod = .{ .rm = .{ .size = .qword, .disp = 8 } },
+        },
     );
 
     return self.finishAir(inst, dst_mcv, .{ ty_op.operand, .none, .none });
@@ -4791,13 +4702,16 @@ fn airArrayElemVal(self: *Self, inst: Air.Inst.Index) !void {
             try self.asmRegisterMemory(
                 .{ ._, .lea },
                 addr_reg,
-                Memory.sib(.qword, .{ .base = .{ .frame = frame_index } }),
+                .{ .base = .{ .frame = frame_index }, .mod = .{ .rm = .{ .size = .qword } } },
             );
         },
         .load_frame => |frame_addr| try self.asmRegisterMemory(
             .{ ._, .lea },
             addr_reg,
-            Memory.sib(.qword, .{ .base = .{ .frame = frame_addr.index }, .disp = frame_addr.off }),
+            .{
+                .base = .{ .frame = frame_addr.index },
+                .mod = .{ .rm = .{ .size = .qword, .disp = frame_addr.off } },
+            },
         ),
         .memory,
         .load_symbol,
@@ -5610,10 +5524,14 @@ fn airBitReverse(self: *Self, inst: Air.Inst.Index) !void {
         try self.asmRegisterMemory(
             .{ ._, .lea },
             if (limb_abi_size > 4) tmp.to64() else tmp.to32(),
-            Memory.sib(.qword, .{
+            .{
                 .base = .{ .reg = dst.to64() },
-                .scale_index = .{ .index = tmp.to64(), .scale = 1 << 2 },
-            }),
+                .mod = .{ .rm = .{
+                    .size = .qword,
+                    .index = tmp.to64(),
+                    .scale = .@"4",
+                } },
+            },
         );
         // tmp = temp3 = ((temp2 >> 2) & 0x33...33) + ((temp2 & 0x33...33) << 2)
         try self.asmRegisterRegister(.{ ._, .mov }, dst, tmp);
@@ -5633,10 +5551,14 @@ fn airBitReverse(self: *Self, inst: Air.Inst.Index) !void {
         try self.asmRegisterMemory(
             .{ ._, .lea },
             if (limb_abi_size > 4) dst.to64() else dst.to32(),
-            Memory.sib(.qword, .{
+            .{
                 .base = .{ .reg = tmp.to64() },
-                .scale_index = .{ .index = dst.to64(), .scale = 1 << 1 },
-            }),
+                .mod = .{ .rm = .{
+                    .size = .qword,
+                    .index = dst.to64(),
+                    .scale = .@"2",
+                } },
+            },
         );
         // dst = ((temp3 >> 1) & 0x55...55) + ((temp3 & 0x55...55) << 1)
     }
@@ -5713,12 +5635,13 @@ fn floatSign(self: *Self, inst: Air.Inst.Index, operand: Air.Inst.Ref, ty: Type)
             .abs => try vec_ty.maxInt(mod, vec_ty),
             else => unreachable,
         } });
-        const sign_mem = if (sign_mcv.isMemory())
-            sign_mcv.mem(Memory.PtrSize.fromSize(abi_size))
+        const sign_mem: Memory = if (sign_mcv.isMemory())
+            sign_mcv.mem(Memory.Size.fromSize(abi_size))
         else
-            Memory.sib(Memory.PtrSize.fromSize(abi_size), .{
+            .{
                 .base = .{ .reg = try self.copyToTmpRegister(Type.usize, sign_mcv.address()) },
-            });
+                .mod = .{ .rm = .{ .size = Memory.Size.fromSize(abi_size) } },
+            };
 
         if (self.hasFeature(.avx)) try self.asmRegisterRegisterMemory(
             switch (scalar_bits) {
@@ -5896,7 +5819,7 @@ fn genRound(self: *Self, ty: Type, dst_reg: Register, src_mcv: MCValue, mode: Ro
             mir_tag,
             dst_alias,
             dst_alias,
-            src_mcv.mem(Memory.PtrSize.fromSize(abi_size)),
+            src_mcv.mem(Memory.Size.fromSize(abi_size)),
             Immediate.u(@as(u5, @bitCast(mode))),
         ) else try self.asmRegisterRegisterRegisterImmediate(
             mir_tag,
@@ -5911,7 +5834,7 @@ fn genRound(self: *Self, ty: Type, dst_reg: Register, src_mcv: MCValue, mode: Ro
         else => if (src_mcv.isMemory()) try self.asmRegisterMemoryImmediate(
             mir_tag,
             dst_alias,
-            src_mcv.mem(Memory.PtrSize.fromSize(abi_size)),
+            src_mcv.mem(Memory.Size.fromSize(abi_size)),
             Immediate.u(@as(u5, @bitCast(mode))),
         ) else try self.asmRegisterRegisterImmediate(
             mir_tag,
@@ -5951,7 +5874,7 @@ fn airAbs(self: *Self, inst: Air.Inst.Index) !void {
                         .memory, .indirect, .load_frame => try self.asmCmovccRegisterMemory(
                             .l,
                             registerAlias(dst_mcv.register, cmov_abi_size),
-                            src_mcv.mem(Memory.PtrSize.fromSize(cmov_abi_size)),
+                            src_mcv.mem(Memory.Size.fromSize(cmov_abi_size)),
                         ),
                         else => {
                             const val_reg = try self.copyToTmpRegister(ty, src_mcv);
@@ -6051,7 +5974,7 @@ fn airAbs(self: *Self, inst: Air.Inst.Index) !void {
         if (src_mcv.isMemory()) try self.asmRegisterMemory(
             mir_tag,
             dst_alias,
-            src_mcv.mem(self.memPtrSize(ty)),
+            src_mcv.mem(self.memSize(ty)),
         ) else try self.asmRegisterRegister(
             mir_tag,
             dst_alias,
@@ -6157,7 +6080,7 @@ fn airSqrt(self: *Self, inst: Air.Inst.Index) !void {
                             if (src_mcv.isMemory()) try self.asmRegisterMemory(
                                 .{ .v_ps, .cvtph2 },
                                 wide_reg,
-                                src_mcv.mem(Memory.PtrSize.fromSize(
+                                src_mcv.mem(Memory.Size.fromSize(
                                     @intCast(@divExact(wide_reg.bitSize(), 16)),
                                 )),
                             ) else try self.asmRegisterRegister(
@@ -6205,7 +6128,7 @@ fn airSqrt(self: *Self, inst: Air.Inst.Index) !void {
                 mir_tag,
                 dst_reg,
                 dst_reg,
-                src_mcv.mem(Memory.PtrSize.fromSize(abi_size)),
+                src_mcv.mem(Memory.Size.fromSize(abi_size)),
             ) else try self.asmRegisterRegisterRegister(
                 mir_tag,
                 dst_reg,
@@ -6218,7 +6141,7 @@ fn airSqrt(self: *Self, inst: Air.Inst.Index) !void {
             else => if (src_mcv.isMemory()) try self.asmRegisterMemory(
                 mir_tag,
                 dst_reg,
-                src_mcv.mem(Memory.PtrSize.fromSize(abi_size)),
+                src_mcv.mem(Memory.Size.fromSize(abi_size)),
             ) else try self.asmRegisterRegister(
                 mir_tag,
                 dst_reg,
@@ -6337,14 +6260,13 @@ fn packedLoad(self: *Self, dst_mcv: MCValue, ptr_ty: Type, ptr_mcv: MCValue) Inn
         if (val_bit_off < val_extra_bits) val_abi_size else val_abi_size * 2;
     if (load_abi_size <= 8) {
         const load_reg = registerAlias(dst_reg, load_abi_size);
-        try self.asmRegisterMemory(
-            .{ ._, .mov },
-            load_reg,
-            Memory.sib(Memory.PtrSize.fromSize(load_abi_size), .{
-                .base = .{ .reg = ptr_reg },
+        try self.asmRegisterMemory(.{ ._, .mov }, load_reg, .{
+            .base = .{ .reg = ptr_reg },
+            .mod = .{ .rm = .{
+                .size = Memory.Size.fromSize(load_abi_size),
                 .disp = val_byte_off,
-            }),
-        );
+            } },
+        });
         try self.asmRegisterImmediate(.{ ._r, .sh }, load_reg, Immediate.u(val_bit_off));
     } else {
         const tmp_reg =
@@ -6353,22 +6275,20 @@ fn packedLoad(self: *Self, dst_mcv: MCValue, ptr_ty: Type, ptr_mcv: MCValue) Inn
         defer self.register_manager.unlockReg(tmp_lock);
 
         const dst_alias = registerAlias(dst_reg, val_abi_size);
-        try self.asmRegisterMemory(
-            .{ ._, .mov },
-            dst_alias,
-            Memory.sib(Memory.PtrSize.fromSize(val_abi_size), .{
-                .base = .{ .reg = ptr_reg },
+        try self.asmRegisterMemory(.{ ._, .mov }, dst_alias, .{
+            .base = .{ .reg = ptr_reg },
+            .mod = .{ .rm = .{
+                .size = Memory.Size.fromSize(val_abi_size),
                 .disp = val_byte_off,
-            }),
-        );
-        try self.asmRegisterMemory(
-            .{ ._, .mov },
-            tmp_reg,
-            Memory.sib(Memory.PtrSize.fromSize(val_abi_size), .{
-                .base = .{ .reg = ptr_reg },
+            } },
+        });
+        try self.asmRegisterMemory(.{ ._, .mov }, tmp_reg, .{
+            .base = .{ .reg = ptr_reg },
+            .mod = .{ .rm = .{
+                .size = Memory.Size.fromSize(val_abi_size),
                 .disp = val_byte_off + 1,
-            }),
-        );
+            } },
+        });
         try self.asmRegisterRegisterImmediate(
             .{ ._rd, .sh },
             dst_alias,
@@ -6480,10 +6400,13 @@ fn packedStore(self: *Self, ptr_ty: Type, ptr_mcv: MCValue, src_mcv: MCValue) In
         const part_bit_off = if (limb_i == 0) src_bit_off else 0;
         const part_bit_size =
             @min(src_bit_off + src_bit_size - limb_i * limb_abi_bits, limb_abi_bits) - part_bit_off;
-        const limb_mem = Memory.sib(Memory.PtrSize.fromSize(limb_abi_size), .{
+        const limb_mem: Memory = .{
             .base = .{ .reg = ptr_reg },
-            .disp = src_byte_off + limb_i * limb_abi_bits,
-        });
+            .mod = .{ .rm = .{
+                .size = Memory.Size.fromSize(limb_abi_size),
+                .disp = src_byte_off + limb_i * limb_abi_bits,
+            } },
+        };
 
         const part_mask = (@as(u64, math.maxInt(u64)) >> @intCast(64 - part_bit_size)) <<
             @intCast(part_bit_off);
@@ -6814,7 +6737,7 @@ fn airStructFieldVal(self: *Self, inst: Air.Inst.Index) !void {
                     break :result dst_mcv;
                 }
 
-                const limb_abi_size: u32 = @min(field_abi_size, 8);
+                const limb_abi_size: u31 = @min(field_abi_size, 8);
                 const limb_abi_bits = limb_abi_size * 8;
                 const field_byte_off: i32 = @intCast(field_off / limb_abi_bits * limb_abi_size);
                 const field_bit_off = field_off % limb_abi_bits;
@@ -6832,14 +6755,13 @@ fn airStructFieldVal(self: *Self, inst: Air.Inst.Index) !void {
                     if (field_bit_off < field_extra_bits) field_abi_size else field_abi_size * 2;
                 if (load_abi_size <= 8) {
                     const load_reg = registerAlias(dst_reg, load_abi_size);
-                    try self.asmRegisterMemory(
-                        .{ ._, .mov },
-                        load_reg,
-                        Memory.sib(Memory.PtrSize.fromSize(load_abi_size), .{
-                            .base = .{ .frame = frame_addr.index },
+                    try self.asmRegisterMemory(.{ ._, .mov }, load_reg, .{
+                        .base = .{ .frame = frame_addr.index },
+                        .mod = .{ .rm = .{
+                            .size = Memory.Size.fromSize(load_abi_size),
                             .disp = frame_addr.off + field_byte_off,
-                        }),
-                    );
+                        } },
+                    });
                     try self.asmRegisterImmediate(.{ ._r, .sh }, load_reg, Immediate.u(field_bit_off));
                 } else {
                     const tmp_reg = registerAlias(
@@ -6853,19 +6775,21 @@ fn airStructFieldVal(self: *Self, inst: Air.Inst.Index) !void {
                     try self.asmRegisterMemory(
                         .{ ._, .mov },
                         dst_alias,
-                        Memory.sib(Memory.PtrSize.fromSize(field_abi_size), .{
+                        .{
                             .base = .{ .frame = frame_addr.index },
-                            .disp = frame_addr.off + field_byte_off,
-                        }),
-                    );
-                    try self.asmRegisterMemory(
-                        .{ ._, .mov },
-                        tmp_reg,
-                        Memory.sib(Memory.PtrSize.fromSize(field_abi_size), .{
-                            .base = .{ .frame = frame_addr.index },
-                            .disp = frame_addr.off + field_byte_off + @as(i32, @intCast(limb_abi_size)),
-                        }),
+                            .mod = .{ .rm = .{
+                                .size = Memory.Size.fromSize(field_abi_size),
+                                .disp = frame_addr.off + field_byte_off,
+                            } },
+                        },
                     );
+                    try self.asmRegisterMemory(.{ ._, .mov }, tmp_reg, .{
+                        .base = .{ .frame = frame_addr.index },
+                        .mod = .{ .rm = .{
+                            .size = Memory.Size.fromSize(field_abi_size),
+                            .disp = frame_addr.off + field_byte_off + limb_abi_size,
+                        } },
+                    });
                     try self.asmRegisterRegisterImmediate(
                         .{ ._rd, .sh },
                         dst_alias,
@@ -6998,14 +6922,13 @@ fn genUnOpMir(self: *Self, mir_tag: Mir.Inst.FixedTag, dst_ty: Type, dst_mcv: MC
             defer self.register_manager.unlockReg(addr_reg_lock);
 
             try self.genSetReg(addr_reg, Type.usize, dst_mcv.address());
-            try self.asmMemory(
-                mir_tag,
-                Memory.sib(Memory.PtrSize.fromSize(abi_size), .{ .base = .{ .reg = addr_reg } }),
-            );
+            try self.asmMemory(mir_tag, .{ .base = .{ .reg = addr_reg }, .mod = .{ .rm = .{
+                .size = Memory.Size.fromSize(abi_size),
+            } } });
         },
         .indirect, .load_frame => try self.asmMemory(
             mir_tag,
-            dst_mcv.mem(Memory.PtrSize.fromSize(abi_size)),
+            dst_mcv.mem(Memory.Size.fromSize(abi_size)),
         ),
     }
 }
@@ -7053,25 +6976,34 @@ fn genShiftBinOpMir(
                 }),
             },
             .memory, .indirect, .load_frame => {
-                const lhs_mem = Memory.sib(Memory.PtrSize.fromSize(abi_size), switch (lhs_mcv) {
+                const lhs_mem: Memory = switch (lhs_mcv) {
                     .memory => |addr| .{
                         .base = .{ .reg = .ds },
-                        .disp = math.cast(i32, @as(i64, @bitCast(addr))) orelse
-                            return self.fail("TODO genShiftBinOpMir between {s} and {s}", .{
-                            @tagName(lhs_mcv),
-                            @tagName(rhs_mcv),
-                        }),
+                        .mod = .{ .rm = .{
+                            .size = Memory.Size.fromSize(abi_size),
+                            .disp = math.cast(i32, @as(i64, @bitCast(addr))) orelse
+                                return self.fail("TODO genShiftBinOpMir between {s} and {s}", .{
+                                @tagName(lhs_mcv),
+                                @tagName(rhs_mcv),
+                            }),
+                        } },
                     },
                     .indirect => |reg_off| .{
                         .base = .{ .reg = reg_off.reg },
-                        .disp = reg_off.off,
+                        .mod = .{ .rm = .{
+                            .size = Memory.Size.fromSize(abi_size),
+                            .disp = reg_off.off,
+                        } },
                     },
                     .load_frame => |frame_addr| .{
                         .base = .{ .frame = frame_addr.index },
-                        .disp = frame_addr.off,
+                        .mod = .{ .rm = .{
+                            .size = Memory.Size.fromSize(abi_size),
+                            .disp = frame_addr.off,
+                        } },
                     },
                     else => unreachable,
-                });
+                };
                 switch (rhs_mcv) {
                     .immediate => |rhs_imm| try self.asmMemoryImmediate(
                         tag,
@@ -7187,26 +7119,35 @@ fn genShiftBinOpMir(
                         try self.asmRegisterMemory(
                             .{ ._, .mov },
                             tmp_reg,
-                            Memory.sib(.qword, .{
+                            .{
                                 .base = .{ .frame = dst_frame_addr.index },
-                                .disp = dst_frame_addr.off + info.indices[0] * 8,
-                            }),
+                                .mod = .{ .rm = .{
+                                    .size = .qword,
+                                    .disp = dst_frame_addr.off + info.indices[0] * 8,
+                                } },
+                            },
                         );
                         try self.asmMemoryRegisterImmediate(
                             info.double_tag,
-                            Memory.sib(.qword, .{
+                            .{
                                 .base = .{ .frame = dst_frame_addr.index },
-                                .disp = dst_frame_addr.off + info.indices[1] * 8,
-                            }),
+                                .mod = .{ .rm = .{
+                                    .size = .qword,
+                                    .disp = dst_frame_addr.off + info.indices[1] * 8,
+                                } },
+                            },
                             tmp_reg,
                             Immediate.u(rhs_imm),
                         );
                         try self.asmMemoryImmediate(
                             tag,
-                            Memory.sib(.qword, .{
+                            .{
                                 .base = .{ .frame = dst_frame_addr.index },
-                                .disp = dst_frame_addr.off + info.indices[0] * 8,
-                            }),
+                                .mod = .{ .rm = .{
+                                    .size = .qword,
+                                    .disp = dst_frame_addr.off + info.indices[0] * 8,
+                                } },
+                            },
                             Immediate.u(rhs_imm),
                         );
                     } else {
@@ -7214,10 +7155,13 @@ fn genShiftBinOpMir(
                         try self.asmRegisterMemory(
                             .{ ._, .mov },
                             tmp_reg,
-                            Memory.sib(.qword, .{
+                            .{
                                 .base = .{ .frame = dst_frame_addr.index },
-                                .disp = dst_frame_addr.off + info.indices[0] * 8,
-                            }),
+                                .mod = .{ .rm = .{
+                                    .size = .qword,
+                                    .disp = dst_frame_addr.off + info.indices[0] * 8,
+                                } },
+                            },
                         );
                         if (rhs_imm > 64) try self.asmRegisterImmediate(
                             tag,
@@ -7226,27 +7170,36 @@ fn genShiftBinOpMir(
                         );
                         try self.asmMemoryRegister(
                             .{ ._, .mov },
-                            Memory.sib(.qword, .{
+                            .{
                                 .base = .{ .frame = dst_frame_addr.index },
-                                .disp = dst_frame_addr.off + info.indices[1] * 8,
-                            }),
+                                .mod = .{ .rm = .{
+                                    .size = .qword,
+                                    .disp = dst_frame_addr.off + info.indices[1] * 8,
+                                } },
+                            },
                             tmp_reg,
                         );
                         if (tag[0] == ._r and tag[1] == .sa) try self.asmMemoryImmediate(
                             tag,
-                            Memory.sib(.qword, .{
+                            .{
                                 .base = .{ .frame = dst_frame_addr.index },
-                                .disp = dst_frame_addr.off + info.indices[0] * 8,
-                            }),
+                                .mod = .{ .rm = .{
+                                    .size = .qword,
+                                    .disp = dst_frame_addr.off + info.indices[0] * 8,
+                                } },
+                            },
                             Immediate.u(63),
                         ) else {
                             try self.asmRegisterRegister(.{ ._, .xor }, tmp_reg.to32(), tmp_reg.to32());
                             try self.asmMemoryRegister(
                                 .{ ._, .mov },
-                                Memory.sib(.qword, .{
+                                .{
                                     .base = .{ .frame = dst_frame_addr.index },
-                                    .disp = dst_frame_addr.off + info.indices[0] * 8,
-                                }),
+                                    .mod = .{ .rm = .{
+                                        .size = .qword,
+                                        .disp = dst_frame_addr.off + info.indices[0] * 8,
+                                    } },
+                                },
                                 tmp_reg,
                             );
                         }
@@ -7265,18 +7218,24 @@ fn genShiftBinOpMir(
                         try self.asmRegisterMemory(
                             .{ ._, .mov },
                             first_reg,
-                            Memory.sib(.qword, .{
+                            .{
                                 .base = .{ .frame = dst_frame_addr.index },
-                                .disp = dst_frame_addr.off + info.indices[0] * 8,
-                            }),
+                                .mod = .{ .rm = .{
+                                    .size = .qword,
+                                    .disp = dst_frame_addr.off + info.indices[0] * 8,
+                                } },
+                            },
                         );
                         try self.asmRegisterMemory(
                             .{ ._, .mov },
                             second_reg,
-                            Memory.sib(.qword, .{
+                            .{
                                 .base = .{ .frame = dst_frame_addr.index },
-                                .disp = dst_frame_addr.off + info.indices[1] * 8,
-                            }),
+                                .mod = .{ .rm = .{
+                                    .size = .qword,
+                                    .disp = dst_frame_addr.off + info.indices[1] * 8,
+                                } },
+                            },
                         );
                         if (tag[0] == ._r and tag[1] == .sa) {
                             try self.asmRegisterRegister(.{ ._, .mov }, tmp_reg, first_reg);
@@ -7302,18 +7261,24 @@ fn genShiftBinOpMir(
                         try self.asmCmovccRegisterRegister(.ae, first_reg, tmp_reg);
                         try self.asmMemoryRegister(
                             .{ ._, .mov },
-                            Memory.sib(.qword, .{
+                            .{
                                 .base = .{ .frame = dst_frame_addr.index },
-                                .disp = dst_frame_addr.off + info.indices[1] * 8,
-                            }),
+                                .mod = .{ .rm = .{
+                                    .size = .qword,
+                                    .disp = dst_frame_addr.off + info.indices[1] * 8,
+                                } },
+                            },
                             second_reg,
                         );
                         try self.asmMemoryRegister(
                             .{ ._, .mov },
-                            Memory.sib(.qword, .{
+                            .{
                                 .base = .{ .frame = dst_frame_addr.index },
-                                .disp = dst_frame_addr.off + info.indices[0] * 8,
-                            }),
+                                .mod = .{ .rm = .{
+                                    .size = .qword,
+                                    .disp = dst_frame_addr.off + info.indices[0] * 8,
+                                } },
+                            },
                             first_reg,
                         );
                     },
@@ -7541,22 +7506,20 @@ fn genMulDivBinOp(
             }, dst_abi_size) };
 
             const dst_mcv = try self.allocRegOrMemAdvanced(dst_ty, maybe_inst, false);
-            try self.asmMemoryRegister(
-                .{ ._, .mov },
-                Memory.sib(.qword, .{
-                    .base = .{ .frame = dst_mcv.load_frame.index },
+            try self.asmMemoryRegister(.{ ._, .mov }, .{
+                .base = .{ .frame = dst_mcv.load_frame.index },
+                .mod = .{ .rm = .{
+                    .size = .qword,
                     .disp = dst_mcv.load_frame.off,
-                }),
-                .rax,
-            );
-            try self.asmMemoryRegister(
-                .{ ._, .mov },
-                Memory.sib(.qword, .{
-                    .base = .{ .frame = dst_mcv.load_frame.index },
+                } },
+            }, .rax);
+            try self.asmMemoryRegister(.{ ._, .mov }, .{
+                .base = .{ .frame = dst_mcv.load_frame.index },
+                .mod = .{ .rm = .{
+                    .size = .qword,
                     .disp = dst_mcv.load_frame.off + 8,
-                }),
-                .rdx,
-            );
+                } },
+            }, .rdx);
             return dst_mcv;
         },
 
@@ -7768,7 +7731,7 @@ fn genBinOp(
                                 mir_tag,
                                 dst_reg,
                                 dst_reg,
-                                src_mcv.mem(Memory.PtrSize.fromBitSize(float_bits)),
+                                src_mcv.mem(Memory.Size.fromBitSize(float_bits)),
                             ) else try self.asmRegisterRegisterRegister(
                                 mir_tag,
                                 dst_reg,
@@ -7787,7 +7750,7 @@ fn genBinOp(
                             if (src_mcv.isMemory()) try self.asmRegisterMemory(
                                 mir_tag,
                                 dst_reg,
-                                src_mcv.mem(Memory.PtrSize.fromBitSize(float_bits)),
+                                src_mcv.mem(Memory.Size.fromBitSize(float_bits)),
                             ) else try self.asmRegisterRegister(
                                 mir_tag,
                                 dst_reg,
@@ -8149,21 +8112,30 @@ fn genBinOp(
                         .memory, .indirect, .load_frame => try self.asmCmovccRegisterMemory(
                             cc,
                             registerAlias(tmp_reg, cmov_abi_size),
-                            Memory.sib(Memory.PtrSize.fromSize(cmov_abi_size), switch (mat_src_mcv) {
+                            switch (mat_src_mcv) {
                                 .memory => |addr| .{
                                     .base = .{ .reg = .ds },
-                                    .disp = @intCast(@as(i64, @bitCast(addr))),
+                                    .mod = .{ .rm = .{
+                                        .size = Memory.Size.fromSize(cmov_abi_size),
+                                        .disp = @intCast(@as(i64, @bitCast(addr))),
+                                    } },
                                 },
                                 .indirect => |reg_off| .{
                                     .base = .{ .reg = reg_off.reg },
-                                    .disp = reg_off.off,
+                                    .mod = .{ .rm = .{
+                                        .size = Memory.Size.fromSize(cmov_abi_size),
+                                        .disp = reg_off.off,
+                                    } },
                                 },
                                 .load_frame => |frame_addr| .{
                                     .base = .{ .frame = frame_addr.index },
-                                    .disp = frame_addr.off,
+                                    .mod = .{ .rm = .{
+                                        .size = Memory.Size.fromSize(cmov_abi_size),
+                                        .disp = frame_addr.off,
+                                    } },
                                 },
                                 else => unreachable,
-                            }),
+                            },
                         ),
                     }
                     try self.genCopy(lhs_ty, dst_mcv, .{ .register = tmp_reg });
@@ -8912,8 +8884,8 @@ fn genBinOp(
             dst_reg,
             lhs_reg,
             src_mcv.mem(switch (lhs_ty.zigTypeTag(mod)) {
-                else => Memory.PtrSize.fromSize(abi_size),
-                .Vector => Memory.PtrSize.fromBitSize(dst_reg.bitSize()),
+                else => Memory.Size.fromSize(abi_size),
+                .Vector => Memory.Size.fromBitSize(dst_reg.bitSize()),
             }),
         ) else try self.asmRegisterRegisterRegister(
             mir_tag,
@@ -8930,8 +8902,8 @@ fn genBinOp(
             mir_tag,
             dst_reg,
             src_mcv.mem(switch (lhs_ty.zigTypeTag(mod)) {
-                else => Memory.PtrSize.fromSize(abi_size),
-                .Vector => Memory.PtrSize.fromBitSize(dst_reg.bitSize()),
+                else => Memory.Size.fromSize(abi_size),
+                .Vector => Memory.Size.fromBitSize(dst_reg.bitSize()),
             }),
         ) else try self.asmRegisterRegister(
             mir_tag,
@@ -9202,12 +9174,12 @@ fn genBinOp(
                         .ty = lhs_ty,
                         .val = try unsigned_ty.maxInt(mod, unsigned_ty),
                     });
-                    const not_mem = if (not_mcv.isMemory())
-                        not_mcv.mem(Memory.PtrSize.fromSize(abi_size))
+                    const not_mem: Memory = if (not_mcv.isMemory())
+                        not_mcv.mem(Memory.Size.fromSize(abi_size))
                     else
-                        Memory.sib(Memory.PtrSize.fromSize(abi_size), .{ .base = .{
+                        .{ .base = .{
                             .reg = try self.copyToTmpRegister(Type.usize, not_mcv.address()),
-                        } });
+                        }, .mod = .{ .rm = .{ .size = Memory.Size.fromSize(abi_size) } } };
                     switch (mir_tag[0]) {
                         .vp_b, .vp_d, .vp_q, .vp_w => try self.asmRegisterRegisterMemory(
                             .{ .vp_, .xor },
@@ -9359,25 +9331,30 @@ fn genBinOpMir(
                     .lea_frame,
                     => {
                         blk: {
-                            return self.asmRegisterMemory(
-                                mir_limb_tag,
-                                dst_alias,
-                                Memory.sib(Memory.PtrSize.fromSize(limb_abi_size), switch (src_mcv) {
-                                    .memory => |addr| .{
-                                        .base = .{ .reg = .ds },
+                            return self.asmRegisterMemory(mir_limb_tag, dst_alias, switch (src_mcv) {
+                                .memory => |addr| .{
+                                    .base = .{ .reg = .ds },
+                                    .mod = .{ .rm = .{
+                                        .size = Memory.Size.fromSize(limb_abi_size),
                                         .disp = math.cast(i32, addr + off) orelse break :blk,
-                                    },
-                                    .indirect => |reg_off| .{
-                                        .base = .{ .reg = reg_off.reg },
+                                    } },
+                                },
+                                .indirect => |reg_off| .{
+                                    .base = .{ .reg = reg_off.reg },
+                                    .mod = .{ .rm = .{
+                                        .size = Memory.Size.fromSize(limb_abi_size),
                                         .disp = reg_off.off + off,
-                                    },
-                                    .load_frame => |frame_addr| .{
-                                        .base = .{ .frame = frame_addr.index },
+                                    } },
+                                },
+                                .load_frame => |frame_addr| .{
+                                    .base = .{ .frame = frame_addr.index },
+                                    .mod = .{ .rm = .{
+                                        .size = Memory.Size.fromSize(limb_abi_size),
                                         .disp = frame_addr.off + off,
-                                    },
-                                    else => break :blk,
-                                }),
-                            );
+                                    } },
+                                },
+                                else => break :blk,
+                            });
                         }
 
                         switch (src_mcv) {
@@ -9510,26 +9487,35 @@ fn genBinOpMir(
                         }),
                     },
                 };
-                const dst_limb_mem = Memory.sib(
-                    Memory.PtrSize.fromSize(limb_abi_size),
-                    switch (dst_mcv) {
-                        .memory,
-                        .load_symbol,
-                        .load_got,
-                        .load_direct,
-                        .load_tlv,
-                        => .{ .base = .{ .reg = dst_info.?.addr_reg }, .disp = off },
-                        .indirect => |reg_off| .{
-                            .base = .{ .reg = reg_off.reg },
+                const dst_limb_mem: Memory = switch (dst_mcv) {
+                    .memory,
+                    .load_symbol,
+                    .load_got,
+                    .load_direct,
+                    .load_tlv,
+                    => .{
+                        .base = .{ .reg = dst_info.?.addr_reg },
+                        .mod = .{ .rm = .{
+                            .size = Memory.Size.fromSize(limb_abi_size),
+                            .disp = off,
+                        } },
+                    },
+                    .indirect => |reg_off| .{
+                        .base = .{ .reg = reg_off.reg },
+                        .mod = .{ .rm = .{
+                            .size = Memory.Size.fromSize(limb_abi_size),
                             .disp = reg_off.off + off,
-                        },
-                        .load_frame => |frame_addr| .{
-                            .base = .{ .frame = frame_addr.index },
+                        } },
+                    },
+                    .load_frame => |frame_addr| .{
+                        .base = .{ .frame = frame_addr.index },
+                        .mod = .{ .rm = .{
+                            .size = Memory.Size.fromSize(limb_abi_size),
                             .disp = frame_addr.off + off,
-                        },
-                        else => unreachable,
+                        } },
                     },
-                );
+                    else => unreachable,
+                };
                 switch (resolved_src_mcv) {
                     .none,
                     .unreach,
@@ -9730,29 +9716,38 @@ fn genIntMulComplexOpMir(self: *Self, dst_ty: Type, dst_mcv: MCValue, src_mcv: M
                 .memory, .indirect, .load_frame => try self.asmRegisterMemory(
                     .{ .i_, .mul },
                     dst_alias,
-                    Memory.sib(Memory.PtrSize.fromSize(abi_size), switch (resolved_src_mcv) {
+                    switch (resolved_src_mcv) {
                         .memory => |addr| .{
                             .base = .{ .reg = .ds },
-                            .disp = math.cast(i32, @as(i64, @bitCast(addr))) orelse
-                                return self.asmRegisterRegister(
-                                .{ .i_, .mul },
-                                dst_alias,
-                                registerAlias(
-                                    try self.copyToTmpRegister(dst_ty, resolved_src_mcv),
-                                    abi_size,
+                            .mod = .{ .rm = .{
+                                .size = Memory.Size.fromSize(abi_size),
+                                .disp = math.cast(i32, @as(i64, @bitCast(addr))) orelse
+                                    return self.asmRegisterRegister(
+                                    .{ .i_, .mul },
+                                    dst_alias,
+                                    registerAlias(
+                                        try self.copyToTmpRegister(dst_ty, resolved_src_mcv),
+                                        abi_size,
+                                    ),
                                 ),
-                            ),
+                            } },
                         },
                         .indirect => |reg_off| .{
                             .base = .{ .reg = reg_off.reg },
-                            .disp = reg_off.off,
+                            .mod = .{ .rm = .{
+                                .size = Memory.Size.fromSize(abi_size),
+                                .disp = reg_off.off,
+                            } },
                         },
                         .load_frame => |frame_addr| .{
                             .base = .{ .frame = frame_addr.index },
-                            .disp = frame_addr.off,
+                            .mod = .{ .rm = .{
+                                .size = Memory.Size.fromSize(abi_size),
+                                .disp = frame_addr.off,
+                            } },
                         },
                         else => unreachable,
-                    }),
+                    },
                 ),
             }
         },
@@ -9857,9 +9852,14 @@ fn genVarDbgInfo(
                 //    .offset = -off,
                 //} },
                 .memory => |address| .{ .memory = address },
-                .load_symbol => |sym_index| .{ .linker_load = .{ .type = .direct, .sym_index = sym_index } }, // TODO
+                .load_symbol => |sym_off| loc: {
+                    assert(sym_off.off == 0);
+                    break :loc .{ .linker_load = .{ .type = .direct, .sym_index = sym_off.sym } };
+                }, // TODO
                 .load_got => |sym_index| .{ .linker_load = .{ .type = .got, .sym_index = sym_index } },
-                .load_direct => |sym_index| .{ .linker_load = .{ .type = .direct, .sym_index = sym_index } },
+                .load_direct => |sym_index| .{
+                    .linker_load = .{ .type = .direct, .sym_index = sym_index },
+                },
                 .immediate => |x| .{ .immediate = x },
                 .undef => .undef,
                 .none => .none,
@@ -10123,19 +10123,16 @@ fn genCall(self: *Self, info: union(enum) {
                             try self.genSetReg(
                                 callee_reg,
                                 Type.usize,
-                                .{ .load_symbol = sym.esym_index },
+                                .{ .load_symbol = .{ .sym = sym.esym_index } },
                             );
                             try self.asmRegister(.{ ._, .call }, callee_reg);
-                        } else {
-                            _ = try self.addInst(.{
-                                .tag = .call,
-                                .ops = .linker_reloc,
-                                .data = .{ .reloc = .{
-                                    .atom_index = try self.owner.getSymbolIndex(self),
-                                    .sym_index = sym.esym_index,
-                                } },
-                            });
-                        }
+                        } else try self.asmMemory(.{ ._, .call }, .{
+                            .base = .{ .reloc = .{
+                                .atom_index = try self.owner.getSymbolIndex(self),
+                                .sym_index = sym.esym_index,
+                            } },
+                            .mod = .{ .rm = .{ .size = .qword } },
+                        });
                     } else if (self.bin_file.cast(link.File.Coff)) |coff_file| {
                         const atom = try coff_file.getOrCreateAtomForDecl(func.owner_decl);
                         const sym_index = coff_file.getAtom(atom).getSymbolIndex().?;
@@ -10149,10 +10146,13 @@ fn genCall(self: *Self, info: union(enum) {
                     } else if (self.bin_file.cast(link.File.Plan9)) |p9| {
                         const atom_index = try p9.seeDecl(func.owner_decl);
                         const atom = p9.getAtom(atom_index);
-                        try self.asmMemory(.{ ._, .call }, Memory.sib(.qword, .{
+                        try self.asmMemory(.{ ._, .call }, .{
                             .base = .{ .reg = .ds },
-                            .disp = @intCast(atom.getOffsetTableAddress(p9)),
-                        }));
+                            .mod = .{ .rm = .{
+                                .size = .qword,
+                                .disp = @intCast(atom.getOffsetTableAddress(p9)),
+                            } },
+                        });
                     } else unreachable;
                 },
                 .extern_func => |extern_func| {
@@ -10637,7 +10637,10 @@ fn airCmpLtErrorsLen(self: *Self, inst: Air.Inst.Index) !void {
     try self.asmRegisterMemory(
         .{ ._, .cmp },
         registerAlias(dst_reg, op_abi_size),
-        Memory.sib(Memory.PtrSize.fromSize(op_abi_size), .{ .base = .{ .reg = addr_reg } }),
+        .{
+            .base = .{ .reg = addr_reg },
+            .mod = .{ .rm = .{ .size = Memory.Size.fromSize(op_abi_size) } },
+        },
     );
 
     self.eflags_inst = inst;
@@ -10891,10 +10894,13 @@ fn isNull(self: *Self, inst: Air.Inst.Index, opt_ty: Type, opt_mcv: MCValue) !MC
             const some_abi_size: u32 = @intCast(some_info.ty.abiSize(mod));
             try self.asmMemoryImmediate(
                 .{ ._, .cmp },
-                Memory.sib(Memory.PtrSize.fromSize(some_abi_size), .{
+                .{
                     .base = .{ .reg = addr_reg },
-                    .disp = some_info.off,
-                }),
+                    .mod = .{ .rm = .{
+                        .size = Memory.Size.fromSize(some_abi_size),
+                        .disp = some_info.off,
+                    } },
+                },
                 Immediate.u(0),
             );
             return .{ .eflags = .e };
@@ -10904,17 +10910,23 @@ fn isNull(self: *Self, inst: Air.Inst.Index, opt_ty: Type, opt_mcv: MCValue) !MC
             const some_abi_size: u32 = @intCast(some_info.ty.abiSize(mod));
             try self.asmMemoryImmediate(
                 .{ ._, .cmp },
-                Memory.sib(Memory.PtrSize.fromSize(some_abi_size), switch (opt_mcv) {
+                switch (opt_mcv) {
                     .indirect => |reg_off| .{
                         .base = .{ .reg = reg_off.reg },
-                        .disp = reg_off.off + some_info.off,
+                        .mod = .{ .rm = .{
+                            .size = Memory.Size.fromSize(some_abi_size),
+                            .disp = reg_off.off + some_info.off,
+                        } },
                     },
                     .load_frame => |frame_addr| .{
                         .base = .{ .frame = frame_addr.index },
-                        .disp = frame_addr.off + some_info.off,
+                        .mod = .{ .rm = .{
+                            .size = Memory.Size.fromSize(some_abi_size),
+                            .disp = frame_addr.off + some_info.off,
+                        } },
                     },
                     else => unreachable,
-                }),
+                },
                 Immediate.u(0),
             );
             return .{ .eflags = .e };
@@ -10944,10 +10956,13 @@ fn isNullPtr(self: *Self, inst: Air.Inst.Index, ptr_ty: Type, ptr_mcv: MCValue)
     const some_abi_size: u32 = @intCast(some_info.ty.abiSize(mod));
     try self.asmMemoryImmediate(
         .{ ._, .cmp },
-        Memory.sib(Memory.PtrSize.fromSize(some_abi_size), .{
+        .{
             .base = .{ .reg = ptr_reg },
-            .disp = some_info.off,
-        }),
+            .mod = .{ .rm = .{
+                .size = Memory.Size.fromSize(some_abi_size),
+                .disp = some_info.off,
+            } },
+        },
         Immediate.u(0),
     );
 
@@ -11020,10 +11035,13 @@ fn isErrPtr(self: *Self, maybe_inst: ?Air.Inst.Index, ptr_ty: Type, ptr_mcv: MCV
     const err_off: u31 = @intCast(errUnionErrorOffset(eu_ty.errorUnionPayload(mod), mod));
     try self.asmMemoryImmediate(
         .{ ._, .cmp },
-        Memory.sib(self.memPtrSize(Type.anyerror), .{
+        .{
             .base = .{ .reg = ptr_reg },
-            .disp = err_off,
-        }),
+            .mod = .{ .rm = .{
+                .size = self.memSize(Type.anyerror),
+                .disp = err_off,
+            } },
+        },
         Immediate.u(0),
     );
 
@@ -11601,7 +11619,7 @@ fn airAsm(self: *Self, inst: Air.Inst.Index) !void {
             label_gop.value_ptr.target = @intCast(self.mir_instructions.len);
         } else continue;
 
-        var mnem_size: ?Memory.PtrSize = null;
+        var mnem_size: ?Memory.Size = null;
         const mnem_tag = mnem: {
             mnem_size = if (mem.endsWith(u8, mnem_str, "b"))
                 .byte
@@ -11620,7 +11638,7 @@ fn airAsm(self: *Self, inst: Air.Inst.Index) !void {
             mnem_size = null;
             break :mnem std.meta.stringToEnum(Instruction.Mnemonic, mnem_str);
         } orelse return self.fail("invalid mnemonic: '{s}'", .{mnem_str});
-        if (@as(?Memory.PtrSize, switch (mnem_tag) {
+        if (@as(?Memory.Size, switch (mnem_tag) {
             .fldenv, .fnstenv, .fstenv => .none,
             .ldmxcsr, .stmxcsr, .vldmxcsr, .vstmxcsr => .dword,
             else => null,
@@ -11685,10 +11703,13 @@ fn airAsm(self: *Self, inst: Air.Inst.Index) !void {
                 if (colon) |colon_pos| {
                     const disp = std.fmt.parseInt(i32, op_str[colon_pos + ":".len ..], 0) catch
                         return self.fail("invalid displacement: '{s}'", .{op_str});
-                    op.* = .{ .mem = Memory.sib(
-                        mnem_size orelse return self.fail("unknown size: '{s}'", .{op_str}),
-                        .{ .base = .{ .reg = reg }, .disp = disp },
-                    ) };
+                    op.* = .{ .mem = .{
+                        .base = .{ .reg = reg },
+                        .mod = .{ .rm = .{
+                            .size = mnem_size orelse return self.fail("unknown size: '{s}'", .{op_str}),
+                            .disp = disp,
+                        } },
+                    } };
                 } else {
                     if (mnem_size) |size| if (reg.bitSize() != size.bitSize())
                         return self.fail("invalid register size: '{s}'", .{op_str});
@@ -11712,34 +11733,45 @@ fn airAsm(self: *Self, inst: Air.Inst.Index) !void {
                         .{ .reg = reg }
                     else
                         return self.fail("invalid modifier: '{s}'", .{modifier}),
-                    .memory => |addr| if (mem.eql(u8, modifier, "") or
-                        mem.eql(u8, modifier, "P"))
-                        .{ .mem = Memory.sib(
-                            mnem_size orelse return self.fail("unknown size: '{s}'", .{op_str}),
-                            .{ .base = .{ .reg = .ds }, .disp = @intCast(@as(i64, @bitCast(addr))) },
-                        ) }
+                    .memory => |addr| if (mem.eql(u8, modifier, "") or mem.eql(u8, modifier, "P"))
+                        .{ .mem = .{
+                            .base = .{ .reg = .ds },
+                            .mod = .{ .rm = .{
+                                .size = mnem_size orelse
+                                    return self.fail("unknown size: '{s}'", .{op_str}),
+                                .disp = @intCast(@as(i64, @bitCast(addr))),
+                            } },
+                        } }
                     else
                         return self.fail("invalid modifier: '{s}'", .{modifier}),
                     .indirect => |reg_off| if (mem.eql(u8, modifier, ""))
-                        .{ .mem = Memory.sib(
-                            mnem_size orelse return self.fail("unknown size: '{s}'", .{op_str}),
-                            .{ .base = .{ .reg = reg_off.reg }, .disp = reg_off.off },
-                        ) }
+                        .{ .mem = .{
+                            .base = .{ .reg = reg_off.reg },
+                            .mod = .{ .rm = .{
+                                .size = mnem_size orelse
+                                    return self.fail("unknown size: '{s}'", .{op_str}),
+                                .disp = reg_off.off,
+                            } },
+                        } }
                     else
                         return self.fail("invalid modifier: '{s}'", .{modifier}),
                     .load_frame => |frame_addr| if (mem.eql(u8, modifier, ""))
-                        .{ .mem = Memory.sib(
-                            mnem_size orelse return self.fail("unknown size: '{s}'", .{op_str}),
-                            .{ .base = .{ .frame = frame_addr.index }, .disp = frame_addr.off },
-                        ) }
+                        .{ .mem = .{
+                            .base = .{ .frame = frame_addr.index },
+                            .mod = .{ .rm = .{
+                                .size = mnem_size orelse
+                                    return self.fail("unknown size: '{s}'", .{op_str}),
+                                .disp = frame_addr.off,
+                            } },
+                        } }
                     else
                         return self.fail("invalid modifier: '{s}'", .{modifier}),
                     .lea_got => |sym_index| if (mem.eql(u8, modifier, "P"))
                         .{ .reg = try self.copyToTmpRegister(Type.usize, .{ .lea_got = sym_index }) }
                     else
                         return self.fail("invalid modifier: '{s}'", .{modifier}),
-                    .load_symbol => |sym_index| if (mem.eql(u8, modifier, "P"))
-                        .{ .reg = try self.copyToTmpRegister(Type.usize, .{ .load_symbol = sym_index }) }
+                    .load_symbol => |sym_off| if (mem.eql(u8, modifier, "P"))
+                        .{ .reg = try self.copyToTmpRegister(Type.usize, .{ .load_symbol = sym_off }) }
                     else
                         return self.fail("invalid modifier: '{s}'", .{modifier}),
                     else => return self.fail("invalid constraint: '{s}'", .{op_str}),
@@ -11774,47 +11806,61 @@ fn airAsm(self: *Self, inst: Air.Inst.Index) !void {
                 const scale_str = sib_it.next() orelse "";
                 if (index_str.len == 0 and scale_str.len > 0)
                     return self.fail("invalid memory operand: '{s}'", .{op_str});
-                const scale = if (scale_str.len > 0) switch (std.fmt.parseInt(u4, scale_str, 10) catch
-                    return self.fail("invalid scale: '{s}'", .{op_str})) {
-                    1, 2, 4, 8 => |scale| scale,
-                    else => return self.fail("invalid scale: '{s}'", .{op_str}),
-                } else 1;
+                const scale: Memory.Scale = if (scale_str.len > 0)
+                    switch (std.fmt.parseInt(u4, scale_str, 10) catch
+                        return self.fail("invalid scale: '{s}'", .{op_str})) {
+                        1 => .@"1",
+                        2 => .@"2",
+                        4 => .@"4",
+                        8 => .@"8",
+                        else => return self.fail("invalid scale: '{s}'", .{op_str}),
+                    }
+                else
+                    .@"1";
                 if (sib_it.next()) |_| return self.fail("invalid memory operand: '{s}'", .{op_str});
-                op.* = .{ .mem = Memory.sib(mnem_size orelse
-                    return self.fail("unknown size: '{s}'", .{op_str}), .{
-                    .disp = if (mem.startsWith(u8, op_str[0..open], "%[") and
-                        mem.endsWith(u8, op_str[0..open], "]"))
-                    disp: {
-                        const colon = mem.indexOfScalarPos(u8, op_str[0..open], "%[".len, ':');
-                        const modifier = if (colon) |colon_pos|
-                            op_str[colon_pos + ":".len .. open - "]".len]
+                op.* = .{
+                    .mem = .{
+                        .base = if (base_str.len > 0)
+                            .{ .reg = parseRegName(base_str["%%".len..]) orelse
+                                return self.fail("invalid base register: '{s}'", .{base_str}) }
                         else
-                            "";
-                        break :disp switch (args.items[
-                            arg_map.get(op_str["%[".len .. colon orelse open - "]".len]) orelse
-                                return self.fail("no matching constraint: '{s}'", .{op_str})
-                        ]) {
-                            .immediate => |imm| if (mem.eql(u8, modifier, "") or
-                                mem.eql(u8, modifier, "c"))
-                                math.cast(i32, @as(i64, @bitCast(imm))) orelse
+                            .none,
+                        .mod = .{ .rm = .{
+                            .size = mnem_size orelse return self.fail("unknown size: '{s}'", .{op_str}),
+                            .index = if (index_str.len > 0)
+                                parseRegName(index_str["%%".len..]) orelse
+                                    return self.fail("invalid index register: '{s}'", .{op_str})
+                            else
+                                .none,
+                            .scale = scale,
+                            .disp = if (mem.startsWith(u8, op_str[0..open], "%[") and
+                                mem.endsWith(u8, op_str[0..open], "]"))
+                            disp: {
+                                const colon = mem.indexOfScalarPos(u8, op_str[0..open], "%[".len, ':');
+                                const modifier = if (colon) |colon_pos|
+                                    op_str[colon_pos + ":".len .. open - "]".len]
+                                else
+                                    "";
+                                break :disp switch (args.items[
+                                    arg_map.get(op_str["%[".len .. colon orelse open - "]".len]) orelse
+                                        return self.fail("no matching constraint: '{s}'", .{op_str})
+                                ]) {
+                                    .immediate => |imm| if (mem.eql(u8, modifier, "") or
+                                        mem.eql(u8, modifier, "c"))
+                                        math.cast(i32, @as(i64, @bitCast(imm))) orelse
+                                            return self.fail("invalid displacement: '{s}'", .{op_str})
+                                    else
+                                        return self.fail("invalid modifier: '{s}'", .{modifier}),
+                                    else => return self.fail("invalid constraint: '{s}'", .{op_str}),
+                                };
+                            } else if (open > 0)
+                                std.fmt.parseInt(i32, op_str[0..open], 0) catch
                                     return self.fail("invalid displacement: '{s}'", .{op_str})
                             else
-                                return self.fail("invalid modifier: '{s}'", .{modifier}),
-                            else => return self.fail("invalid constraint: '{s}'", .{op_str}),
-                        };
-                    } else if (open > 0)
-                        std.fmt.parseInt(i32, op_str[0..open], 0) catch
-                            return self.fail("invalid displacement: '{s}'", .{op_str})
-                    else
-                        0,
-                    .base = if (base_str.len > 0) .{ .reg = parseRegName(base_str["%%".len..]) orelse
-                        return self.fail("invalid base register: '{s}'", .{base_str}) } else .none,
-                    .scale_index = if (index_str.len > 0) .{
-                        .index = parseRegName(index_str["%%".len..]) orelse
-                            return self.fail("invalid index register: '{s}'", .{op_str}),
-                        .scale = scale,
-                    } else null,
-                }) };
+                                0,
+                        } },
+                    },
+                };
             } else if (Label.isValid(.reference, op_str)) {
                 const anon = std.ascii.isDigit(op_str[0]);
                 const label_gop = try labels.getOrPut(self.gpa, op_str[0..if (anon) 1 else op_str.len]);
@@ -12534,20 +12580,23 @@ fn genSetReg(self: *Self, dst_reg: Register, ty: Type, src_mcv: MCValue) InnerEr
             ),
             .lea_frame => .{ .move = .{ ._, .lea } },
             else => unreachable,
-        }).read(self, registerAlias(dst_reg, abi_size), Memory.sib(
-            self.memPtrSize(ty),
-            switch (src_mcv) {
-                .register_offset, .indirect => |reg_off| .{
-                    .base = .{ .reg = reg_off.reg },
+        }).read(self, registerAlias(dst_reg, abi_size), switch (src_mcv) {
+            .register_offset, .indirect => |reg_off| .{
+                .base = .{ .reg = reg_off.reg },
+                .mod = .{ .rm = .{
+                    .size = self.memSize(ty),
                     .disp = reg_off.off,
-                },
-                .load_frame, .lea_frame => |frame_addr| .{
-                    .base = .{ .frame = frame_addr.index },
+                } },
+            },
+            .load_frame, .lea_frame => |frame_addr| .{
+                .base = .{ .frame = frame_addr.index },
+                .mod = .{ .rm = .{
+                    .size = self.memSize(ty),
                     .disp = frame_addr.off,
-                },
-                else => unreachable,
+                } },
             },
-        )),
+            else => unreachable,
+        }),
         .memory, .load_symbol, .load_direct, .load_got, .load_tlv => {
             switch (src_mcv) {
                 .memory => |addr| if (math.cast(i32, @as(i64, @bitCast(addr)))) |small_addr|
@@ -12555,20 +12604,40 @@ fn genSetReg(self: *Self, dst_reg: Register, ty: Type, src_mcv: MCValue) InnerEr
                         ty,
                         dst_reg.class(),
                         ty.abiAlignment(mod).check(@as(u32, @bitCast(small_addr))),
-                    )).read(self, registerAlias(dst_reg, abi_size), Memory.sib(
-                        self.memPtrSize(ty),
-                        .{ .base = .{ .reg = .ds }, .disp = small_addr },
-                    )),
+                    )).read(self, registerAlias(dst_reg, abi_size), .{
+                        .base = .{ .reg = .ds },
+                        .mod = .{ .rm = .{
+                            .size = self.memSize(ty),
+                            .disp = small_addr,
+                        } },
+                    }),
+                .load_symbol => |sym_off| switch (dst_reg.class()) {
+                    .general_purpose => {
+                        assert(sym_off.off == 0);
+                        try self.asmRegisterMemory(.{ ._, .mov }, registerAlias(dst_reg, abi_size), .{
+                            .base = .{ .reloc = .{
+                                .atom_index = try self.owner.getSymbolIndex(self),
+                                .sym_index = sym_off.sym,
+                            } },
+                            .mod = .{ .rm = .{
+                                .size = self.memSize(ty),
+                                .disp = sym_off.off,
+                            } },
+                        });
+                        return;
+                    },
+                    .segment, .mmx => unreachable,
+                    .x87, .sse => {},
+                },
                 .load_direct => |sym_index| switch (dst_reg.class()) {
                     .general_purpose => {
-                        const atom_index = try self.owner.getSymbolIndex(self);
                         _ = try self.addInst(.{
                             .tag = .mov,
                             .ops = .direct_reloc,
                             .data = .{ .rx = .{
-                                .r1 = dst_reg.to64(),
-                                .payload = try self.addExtra(Mir.Reloc{
-                                    .atom_index = atom_index,
+                                .r1 = registerAlias(dst_reg, abi_size),
+                                .payload = try self.addExtra(bits.Symbol{
+                                    .atom_index = try self.owner.getSymbolIndex(self),
                                     .sym_index = sym_index,
                                 }),
                             } },
@@ -12578,7 +12647,7 @@ fn genSetReg(self: *Self, dst_reg: Register, ty: Type, src_mcv: MCValue) InnerEr
                     .segment, .mmx => unreachable,
                     .x87, .sse => {},
                 },
-                .load_symbol, .load_got, .load_tlv => {},
+                .load_got, .load_tlv => {},
                 else => unreachable,
             }
 
@@ -12589,22 +12658,42 @@ fn genSetReg(self: *Self, dst_reg: Register, ty: Type, src_mcv: MCValue) InnerEr
             try (try self.moveStrategy(ty, dst_reg.class(), false)).read(
                 self,
                 registerAlias(dst_reg, abi_size),
-                Memory.sib(Memory.PtrSize.fromSize(abi_size), .{ .base = .{ .reg = addr_reg } }),
+                .{
+                    .base = .{ .reg = addr_reg },
+                    .mod = .{ .rm = .{ .size = Memory.Size.fromSize(abi_size) } },
+                },
             );
         },
-        .lea_symbol, .lea_direct, .lea_got => |sym_index| {
+        .lea_symbol => |sym_index| {
             const atom_index = try self.owner.getSymbolIndex(self);
             if (self.bin_file.cast(link.File.Elf)) |_| {
-                _ = try self.addInst(.{
-                    .tag = .lea,
-                    .ops = .linker_reloc,
-                    .data = .{ .rx = .{
-                        .r1 = dst_reg.to64(),
-                        .payload = try self.addExtra(Mir.Reloc{
+                try self.asmRegisterMemory(
+                    .{ ._, .lea },
+                    dst_reg.to64(),
+                    .{
+                        .base = .{ .reloc = .{
                             .atom_index = atom_index,
-                            .sym_index = sym_index,
-                        }),
+                            .sym_index = sym_index.sym,
+                        } },
+                        .mod = .{ .rm = .{
+                            .size = .qword,
+                            .disp = sym_index.off,
+                        } },
+                    },
+                );
+            } else return self.fail("TODO emit symbol sequence on {s}", .{
+                @tagName(self.bin_file.tag),
+            });
+        },
+        .lea_direct, .lea_got => |sym_index| {
+            const atom_index = try self.owner.getSymbolIndex(self);
+            if (self.bin_file.cast(link.File.Elf)) |_| {
+                try self.asmRegisterMemory(.{ ._, .lea }, dst_reg.to64(), .{
+                    .base = .{ .reloc = .{
+                        .atom_index = atom_index,
+                        .sym_index = sym_index,
                     } },
+                    .mod = .{ .rm = .{ .size = .qword } },
                 });
             } else {
                 _ = try self.addInst(.{
@@ -12620,7 +12709,7 @@ fn genSetReg(self: *Self, dst_reg: Register, ty: Type, src_mcv: MCValue) InnerEr
                     },
                     .data = .{ .rx = .{
                         .r1 = dst_reg.to64(),
-                        .payload = try self.addExtra(Mir.Reloc{
+                        .payload = try self.addExtra(bits.Symbol{
                             .atom_index = atom_index,
                             .sym_index = sym_index,
                         }),
@@ -12636,14 +12725,17 @@ fn genSetReg(self: *Self, dst_reg: Register, ty: Type, src_mcv: MCValue) InnerEr
                     .ops = .tlv_reloc,
                     .data = .{ .rx = .{
                         .r1 = .rdi,
-                        .payload = try self.addExtra(Mir.Reloc{
+                        .payload = try self.addExtra(bits.Symbol{
                             .atom_index = atom_index,
                             .sym_index = sym_index,
                         }),
                     } },
                 });
                 // TODO: spill registers before calling
-                try self.asmMemory(.{ ._, .call }, Memory.sib(.qword, .{ .base = .{ .reg = .rdi } }));
+                try self.asmMemory(.{ ._, .call }, .{
+                    .base = .{ .reg = .rdi },
+                    .mod = .{ .rm = .{ .size = .qword } },
+                });
                 try self.genSetReg(dst_reg.to64(), Type.usize, .{ .register = .rax });
             } else return self.fail("TODO emit ptr to TLV sequence on {s}", .{
                 @tagName(self.bin_file.tag),
@@ -12660,6 +12752,7 @@ fn genSetMem(self: *Self, base: Memory.Base, disp: i32, ty: Type, src_mcv: MCVal
         .none => .{ .immediate = @bitCast(@as(i64, disp)) },
         .reg => |base_reg| .{ .register_offset = .{ .reg = base_reg, .off = disp } },
         .frame => |base_frame_index| .{ .lea_frame = .{ .index = base_frame_index, .off = disp } },
+        .reloc => |base_symbol| .{ .lea_symbol = .{ .sym = base_symbol.sym_index, .off = disp } },
     };
     switch (src_mcv) {
         .none, .unreach, .dead, .reserved_frame => unreachable,
@@ -12675,7 +12768,10 @@ fn genSetMem(self: *Self, base: Memory.Base, disp: i32, ty: Type, src_mcv: MCVal
                 };
                 try self.asmMemoryImmediate(
                     .{ ._, .mov },
-                    Memory.sib(Memory.PtrSize.fromSize(abi_size), .{ .base = base, .disp = disp }),
+                    .{ .base = base, .mod = .{ .rm = .{
+                        .size = Memory.Size.fromSize(abi_size),
+                        .disp = disp,
+                    } } },
                     immediate,
                 );
             },
@@ -12683,27 +12779,31 @@ fn genSetMem(self: *Self, base: Memory.Base, disp: i32, ty: Type, src_mcv: MCVal
             else => if (math.cast(i32, @as(i64, @bitCast(imm)))) |small| {
                 try self.asmMemoryImmediate(
                     .{ ._, .mov },
-                    Memory.sib(Memory.PtrSize.fromSize(abi_size), .{ .base = base, .disp = disp }),
+                    .{ .base = base, .mod = .{ .rm = .{
+                        .size = Memory.Size.fromSize(abi_size),
+                        .disp = disp,
+                    } } },
                     Immediate.s(small),
                 );
             } else {
                 var offset: i32 = 0;
                 while (offset < abi_size) : (offset += 4) try self.asmMemoryImmediate(
                     .{ ._, .mov },
-                    Memory.sib(.dword, .{ .base = base, .disp = disp + offset }),
-                    if (ty.isSignedInt(mod))
-                        Immediate.s(
-                            @truncate(@as(i64, @bitCast(imm)) >> (math.cast(u6, offset * 8) orelse 63)),
-                        )
-                    else
-                        Immediate.u(@as(
-                            u32,
-                            @truncate(if (math.cast(u6, offset * 8)) |shift| imm >> shift else 0),
-                        )),
+                    .{ .base = base, .mod = .{ .rm = .{
+                        .size = .dword,
+                        .disp = disp + offset,
+                    } } },
+                    if (ty.isSignedInt(mod)) Immediate.s(
+                        @truncate(@as(i64, @bitCast(imm)) >> (math.cast(u6, offset * 8) orelse 63)),
+                    ) else Immediate.u(
+                        @as(u32, @truncate(if (math.cast(u6, offset * 8)) |shift| imm >> shift else 0)),
+                    ),
                 );
             },
         },
-        .eflags => |cc| try self.asmSetccMemory(cc, Memory.sib(.byte, .{ .base = base, .disp = disp })),
+        .eflags => |cc| try self.asmSetccMemory(cc, .{ .base = base, .mod = .{
+            .rm = .{ .size = .byte, .disp = disp },
+        } }),
         .register => |src_reg| try (try self.moveStrategy(ty, src_reg.class(), switch (base) {
             .none => ty.abiAlignment(mod).check(@as(u32, @bitCast(disp))),
             .reg => |reg| switch (reg) {
@@ -12713,9 +12813,13 @@ fn genSetMem(self: *Self, base: Memory.Base, disp: i32, ty: Type, src_mcv: MCVal
             .frame => |frame_index| self.getFrameAddrAlignment(
                 .{ .index = frame_index, .off = disp },
             ).compare(.gte, ty.abiAlignment(mod)),
+            .reloc => false,
         })).write(
             self,
-            Memory.sib(self.memPtrSize(ty), .{ .base = base, .disp = disp }),
+            .{ .base = base, .mod = .{ .rm = .{
+                .size = self.memSize(ty),
+                .disp = disp,
+            } } },
             registerAlias(src_reg, abi_size),
         ),
         .register_pair => |src_regs| for (src_regs, 0..) |src_reg, src_reg_i| {
@@ -12732,11 +12836,12 @@ fn genSetMem(self: *Self, base: Memory.Base, disp: i32, ty: Type, src_mcv: MCVal
                     .frame => |frame_index| self.getFrameAddrAlignment(
                         .{ .index = frame_index, .off = disp },
                     ).compare(.gte, ty.abiAlignment(mod)),
+                    .reloc => false,
                 },
-            )).write(self, Memory.sib(
-                Memory.PtrSize.fromSize(part_size),
-                .{ .base = base, .disp = disp + @as(i32, @intCast(src_reg_i * 8)) },
-            ), registerAlias(src_reg, part_size));
+            )).write(self, .{ .base = base, .mod = .{ .rm = .{
+                .size = Memory.Size.fromSize(part_size),
+                .disp = disp + @as(i32, @intCast(src_reg_i * 8)),
+            } } }, registerAlias(src_reg, part_size));
         },
         .register_overflow => |ro| switch (ty.zigTypeTag(mod)) {
             .Struct => {
@@ -12834,7 +12939,7 @@ fn genExternSymbolRef(
             .ops = .import_reloc,
             .data = .{ .rx = .{
                 .r1 = .rax,
-                .payload = try self.addExtra(Mir.Reloc{
+                .payload = try self.addExtra(bits.Symbol{
                     .atom_index = atom_index,
                     .sym_index = try coff_file.getGlobalSymbol(callee, lib),
                 }),
@@ -12871,8 +12976,12 @@ fn genLazySymbolRef(
 
         if (self.bin_file.options.pic) {
             switch (tag) {
-                .lea, .call => try self.genSetReg(reg, Type.usize, .{ .load_symbol = sym.esym_index }),
-                .mov => try self.genSetReg(reg, Type.usize, .{ .load_symbol = sym.esym_index }),
+                .lea, .call => try self.genSetReg(reg, Type.usize, .{
+                    .load_symbol = .{ .sym = sym.esym_index },
+                }),
+                .mov => try self.genSetReg(reg, Type.usize, .{
+                    .load_symbol = .{ .sym = sym.esym_index },
+                }),
                 else => unreachable,
             }
             switch (tag) {
@@ -12881,23 +12990,18 @@ fn genLazySymbolRef(
                 else => unreachable,
             }
         } else {
-            const reloc = Mir.Reloc{
+            const reloc = bits.Symbol{
                 .atom_index = try self.owner.getSymbolIndex(self),
                 .sym_index = sym.esym_index,
             };
             switch (tag) {
-                .lea, .mov => _ = try self.addInst(.{
-                    .tag = .mov,
-                    .ops = .linker_reloc,
-                    .data = .{ .rx = .{
-                        .r1 = reg.to64(),
-                        .payload = try self.addExtra(reloc),
-                    } },
+                .lea, .mov => try self.asmRegisterMemory(.{ ._, .mov }, reg.to64(), .{
+                    .base = .{ .reloc = reloc },
+                    .mod = .{ .rm = .{ .size = .qword } },
                 }),
-                .call => _ = try self.addInst(.{
-                    .tag = .call,
-                    .ops = .linker_reloc,
-                    .data = .{ .reloc = reloc },
+                .call => try self.asmMemory(.{ ._, .call }, .{
+                    .base = .{ .reloc = reloc },
+                    .mod = .{ .rm = .{ .size = .qword } },
                 }),
                 else => unreachable,
             }
@@ -12908,8 +13012,13 @@ fn genLazySymbolRef(
         var atom = p9_file.getAtom(atom_index);
         _ = atom.getOrCreateOffsetTableEntry(p9_file);
         const got_addr = atom.getOffsetTableAddress(p9_file);
-        const got_mem =
-            Memory.sib(.qword, .{ .base = .{ .reg = .ds }, .disp = @intCast(got_addr) });
+        const got_mem: Memory = .{
+            .base = .{ .reg = .ds },
+            .mod = .{ .rm = .{
+                .size = .qword,
+                .disp = @intCast(got_addr),
+            } },
+        };
         switch (tag) {
             .lea, .mov => try self.asmRegisterMemory(.{ ._, .mov }, reg.to64(), got_mem),
             .call => try self.asmMemory(.{ ._, .call }, got_mem),
@@ -13255,19 +13364,20 @@ fn airCmpxchg(self: *Self, inst: Air.Inst.Index) !void {
     defer if (new_lock) |lock| self.register_manager.unlockReg(lock);
 
     const ptr_mcv = try self.resolveInst(extra.ptr);
-    const ptr_size = Memory.PtrSize.fromSize(val_abi_size);
-    const ptr_mem = switch (ptr_mcv) {
-        .immediate, .register, .register_offset, .lea_frame => ptr_mcv.deref().mem(ptr_size),
-        else => Memory.sib(ptr_size, .{
+    const mem_size = Memory.Size.fromSize(val_abi_size);
+    const ptr_mem: Memory = switch (ptr_mcv) {
+        .immediate, .register, .register_offset, .lea_frame => ptr_mcv.deref().mem(mem_size),
+        else => .{
             .base = .{ .reg = try self.copyToTmpRegister(ptr_ty, ptr_mcv) },
-        }),
+            .mod = .{ .rm = .{ .size = mem_size } },
+        },
     };
-    switch (ptr_mem) {
-        .sib, .rip => {},
-        .moffs => return self.fail("TODO airCmpxchg with {s}", .{@tagName(ptr_mcv)}),
+    switch (ptr_mem.mod) {
+        .rm => {},
+        .off => return self.fail("TODO airCmpxchg with {s}", .{@tagName(ptr_mcv)}),
     }
-    const ptr_lock = switch (ptr_mem.base()) {
-        .none, .frame => null,
+    const ptr_lock = switch (ptr_mem.base) {
+        .none, .frame, .reloc => null,
         .reg => |reg| self.register_manager.lockReg(reg),
     };
     defer if (ptr_lock) |lock| self.register_manager.unlockReg(lock);
@@ -13320,19 +13430,20 @@ fn atomicOp(
     defer if (val_lock) |lock| self.register_manager.unlockReg(lock);
 
     const val_abi_size: u32 = @intCast(val_ty.abiSize(mod));
-    const ptr_size = Memory.PtrSize.fromSize(val_abi_size);
-    const ptr_mem = switch (ptr_mcv) {
-        .immediate, .register, .register_offset, .lea_frame => ptr_mcv.deref().mem(ptr_size),
-        else => Memory.sib(ptr_size, .{
+    const mem_size = Memory.Size.fromSize(val_abi_size);
+    const ptr_mem: Memory = switch (ptr_mcv) {
+        .immediate, .register, .register_offset, .lea_frame => ptr_mcv.deref().mem(mem_size),
+        else => .{
             .base = .{ .reg = try self.copyToTmpRegister(ptr_ty, ptr_mcv) },
-        }),
+            .mod = .{ .rm = .{ .size = mem_size } },
+        },
     };
-    switch (ptr_mem) {
-        .sib, .rip => {},
-        .moffs => return self.fail("TODO airCmpxchg with {s}", .{@tagName(ptr_mcv)}),
+    switch (ptr_mem.mod) {
+        .rm => {},
+        .off => return self.fail("TODO airCmpxchg with {s}", .{@tagName(ptr_mcv)}),
     }
-    const mem_lock = switch (ptr_mem.base()) {
-        .none, .frame => null,
+    const mem_lock = switch (ptr_mem.base) {
+        .none, .frame, .reloc => null,
         .reg => |reg| self.register_manager.lockReg(reg),
     };
     defer if (mem_lock) |lock| self.register_manager.unlockReg(lock);
@@ -13440,7 +13551,7 @@ fn atomicOp(
                         .memory, .indirect, .load_frame => try self.asmCmovccRegisterMemory(
                             cc,
                             registerAlias(tmp_reg, cmov_abi_size),
-                            val_mcv.mem(Memory.PtrSize.fromSize(cmov_abi_size)),
+                            val_mcv.mem(Memory.Size.fromSize(cmov_abi_size)),
                         ),
                         else => {
                             const val_reg = try self.copyToTmpRegister(val_ty, val_mcv);
@@ -13461,16 +13572,24 @@ fn atomicOp(
             _ = try self.asmJccReloc(.ne, loop);
             return if (unused) .unreach else .{ .register = .rax };
         } else {
-            try self.asmRegisterMemory(.{ ._, .mov }, .rax, Memory.sib(.qword, .{
-                .base = ptr_mem.sib.base,
-                .scale_index = ptr_mem.scaleIndex(),
-                .disp = ptr_mem.sib.disp + 0,
-            }));
-            try self.asmRegisterMemory(.{ ._, .mov }, .rdx, Memory.sib(.qword, .{
-                .base = ptr_mem.sib.base,
-                .scale_index = ptr_mem.scaleIndex(),
-                .disp = ptr_mem.sib.disp + 8,
-            }));
+            try self.asmRegisterMemory(.{ ._, .mov }, .rax, .{
+                .base = ptr_mem.base,
+                .mod = .{ .rm = .{
+                    .size = .qword,
+                    .index = ptr_mem.mod.rm.index,
+                    .scale = ptr_mem.mod.rm.scale,
+                    .disp = ptr_mem.mod.rm.disp + 0,
+                } },
+            });
+            try self.asmRegisterMemory(.{ ._, .mov }, .rdx, .{
+                .base = ptr_mem.base,
+                .mod = .{ .rm = .{
+                    .size = .qword,
+                    .index = ptr_mem.mod.rm.index,
+                    .scale = ptr_mem.mod.rm.scale,
+                    .disp = ptr_mem.mod.rm.disp + 8,
+                } },
+            });
             const loop: Mir.Inst.Index = @intCast(self.mir_instructions.len);
             const val_mem_mcv: MCValue = switch (val_mcv) {
                 .memory, .indirect, .load_frame => val_mcv,
@@ -13524,22 +13643,20 @@ fn atomicOp(
 
             if (unused) return .unreach;
             const dst_mcv = try self.allocTempRegOrMem(val_ty, false);
-            try self.asmMemoryRegister(
-                .{ ._, .mov },
-                Memory.sib(.qword, .{
-                    .base = .{ .frame = dst_mcv.load_frame.index },
+            try self.asmMemoryRegister(.{ ._, .mov }, .{
+                .base = .{ .frame = dst_mcv.load_frame.index },
+                .mod = .{ .rm = .{
+                    .size = .qword,
                     .disp = dst_mcv.load_frame.off + 0,
-                }),
-                .rax,
-            );
-            try self.asmMemoryRegister(
-                .{ ._, .mov },
-                Memory.sib(.qword, .{
-                    .base = .{ .frame = dst_mcv.load_frame.index },
+                } },
+            }, .rax);
+            try self.asmMemoryRegister(.{ ._, .mov }, .{
+                .base = .{ .frame = dst_mcv.load_frame.index },
+                .mod = .{ .rm = .{
+                    .size = .qword,
                     .disp = dst_mcv.load_frame.off + 8,
-                }),
-                .rdx,
-            );
+                } },
+            }, .rdx);
             return dst_mcv;
         },
         .libcall => return self.fail("TODO implement x86 atomic libcall", .{}),
@@ -13845,55 +13962,74 @@ fn airErrorName(self: *Self, inst: Air.Inst.Index) !void {
     try self.asmRegisterMemory(
         .{ ._, .mov },
         start_reg.to32(),
-        Memory.sib(.dword, .{
+        .{
             .base = .{ .reg = addr_reg.to64() },
-            .scale_index = .{ .scale = 4, .index = err_reg.to64() },
-            .disp = 4,
-        }),
+            .mod = .{ .rm = .{
+                .size = .dword,
+                .index = err_reg.to64(),
+                .scale = .@"4",
+                .disp = 4,
+            } },
+        },
     );
     try self.asmRegisterMemory(
         .{ ._, .mov },
         end_reg.to32(),
-        Memory.sib(.dword, .{
+        .{
             .base = .{ .reg = addr_reg.to64() },
-            .scale_index = .{ .scale = 4, .index = err_reg.to64() },
-            .disp = 8,
-        }),
+            .mod = .{ .rm = .{
+                .size = .dword,
+                .index = err_reg.to64(),
+                .scale = .@"4",
+                .disp = 8,
+            } },
+        },
     );
     try self.asmRegisterRegister(.{ ._, .sub }, end_reg.to32(), start_reg.to32());
     try self.asmRegisterMemory(
         .{ ._, .lea },
         start_reg.to64(),
-        Memory.sib(.byte, .{
+        .{
             .base = .{ .reg = addr_reg.to64() },
-            .scale_index = .{ .scale = 1, .index = start_reg.to64() },
-            .disp = 0,
-        }),
+            .mod = .{ .rm = .{
+                .size = .dword,
+                .index = start_reg.to64(),
+            } },
+        },
     );
     try self.asmRegisterMemory(
         .{ ._, .lea },
         end_reg.to32(),
-        Memory.sib(.byte, .{
+        .{
             .base = .{ .reg = end_reg.to64() },
-            .disp = -1,
-        }),
+            .mod = .{ .rm = .{
+                .size = .byte,
+                .disp = -1,
+            } },
+        },
     );
 
     const dst_mcv = try self.allocRegOrMem(inst, false);
     try self.asmMemoryRegister(
         .{ ._, .mov },
-        Memory.sib(.qword, .{
+        .{
             .base = .{ .frame = dst_mcv.load_frame.index },
-            .disp = dst_mcv.load_frame.off,
-        }),
+            .mod = .{ .rm = .{
+                .size = .qword,
+                .disp = dst_mcv.load_frame.off,
+            } },
+        },
         start_reg.to64(),
     );
     try self.asmMemoryRegister(
         .{ ._, .mov },
-        Memory.sib(.qword, .{
+        .{
             .base = .{ .frame = dst_mcv.load_frame.index },
-            .disp = dst_mcv.load_frame.off + 8,
-        }),
+            .mod = .{ .rm = .{
+                .size = .qword,
+                .disp = dst_mcv.load_frame.off + 8,
+            } },
+        },
         end_reg.to64(),
     );
 
@@ -14130,7 +14266,7 @@ fn airReduce(self: *Self, inst: Air.Inst.Index) !void {
                 .Or => {
                     if (operand_mcv.isMemory()) try self.asmMemoryImmediate(
                         .{ ._, .@"test" },
-                        operand_mcv.mem(Memory.PtrSize.fromSize(abi_size)),
+                        operand_mcv.mem(Memory.Size.fromSize(abi_size)),
                         Immediate.u(mask),
                     ) else {
                         const operand_reg = registerAlias(if (operand_mcv.isRegister())
@@ -14522,7 +14658,7 @@ fn airMulAdd(self: *Self, inst: Air.Inst.Index) !void {
             mir_tag,
             mop1_reg,
             mop2_reg,
-            mops[2].mem(Memory.PtrSize.fromSize(abi_size)),
+            mops[2].mem(Memory.Size.fromSize(abi_size)),
         );
         break :result mops[0];
     };
@@ -14633,24 +14769,32 @@ fn airVaArg(self: *Self, inst: Air.Inst.Index) !void {
                     const mem_reloc = try self.asmJccReloc(.ae, undefined);
 
                     try self.genSetReg(addr_reg, ptr_anyopaque_ty, reg_save_area);
-                    if (!unused)
-                        try self.asmRegisterMemory(.{ ._, .lea }, addr_reg, Memory.sib(.qword, .{
-                            .base = .{ .reg = addr_reg },
-                            .scale_index = .{ .scale = 1, .index = offset_reg.to64() },
-                        }));
-                    try self.asmRegisterMemory(.{ ._, .lea }, offset_reg, Memory.sib(.qword, .{
+                    if (!unused) try self.asmRegisterMemory(.{ ._, .lea }, addr_reg, .{
+                        .base = .{ .reg = addr_reg },
+                        .mod = .{ .rm = .{
+                            .size = .qword,
+                            .index = offset_reg.to64(),
+                        } },
+                    });
+                    try self.asmRegisterMemory(.{ ._, .lea }, offset_reg, .{
                         .base = .{ .reg = offset_reg.to64() },
-                        .disp = 8,
-                    }));
+                        .mod = .{ .rm = .{
+                            .size = .qword,
+                            .disp = 8,
+                        } },
+                    });
                     try self.genCopy(Type.c_uint, gp_offset, .{ .register = offset_reg });
                     const done_reloc = try self.asmJmpReloc(undefined);
 
                     try self.performReloc(mem_reloc);
                     try self.genSetReg(addr_reg, ptr_anyopaque_ty, overflow_arg_area);
-                    try self.asmRegisterMemory(.{ ._, .lea }, offset_reg.to64(), Memory.sib(.qword, .{
+                    try self.asmRegisterMemory(.{ ._, .lea }, offset_reg.to64(), .{
                         .base = .{ .reg = addr_reg },
-                        .disp = @intCast(@max(promote_ty.abiSize(mod), 8)),
-                    }));
+                        .mod = .{ .rm = .{
+                            .size = .qword,
+                            .disp = @intCast(@max(promote_ty.abiSize(mod), 8)),
+                        } },
+                    });
                     try self.genCopy(
                         ptr_anyopaque_ty,
                         overflow_arg_area,
@@ -14672,24 +14816,32 @@ fn airVaArg(self: *Self, inst: Air.Inst.Index) !void {
                     const mem_reloc = try self.asmJccReloc(.ae, undefined);
 
                     try self.genSetReg(addr_reg, ptr_anyopaque_ty, reg_save_area);
-                    if (!unused)
-                        try self.asmRegisterMemory(.{ ._, .lea }, addr_reg, Memory.sib(.qword, .{
-                            .base = .{ .reg = addr_reg },
-                            .scale_index = .{ .scale = 1, .index = offset_reg.to64() },
-                        }));
-                    try self.asmRegisterMemory(.{ ._, .lea }, offset_reg, Memory.sib(.qword, .{
+                    if (!unused) try self.asmRegisterMemory(.{ ._, .lea }, addr_reg, .{
+                        .base = .{ .reg = addr_reg },
+                        .mod = .{ .rm = .{
+                            .size = .qword,
+                            .index = offset_reg.to64(),
+                        } },
+                    });
+                    try self.asmRegisterMemory(.{ ._, .lea }, offset_reg, .{
                         .base = .{ .reg = offset_reg.to64() },
-                        .disp = 16,
-                    }));
+                        .mod = .{ .rm = .{
+                            .size = .qword,
+                            .disp = 16,
+                        } },
+                    });
                     try self.genCopy(Type.c_uint, fp_offset, .{ .register = offset_reg });
                     const done_reloc = try self.asmJmpReloc(undefined);
 
                     try self.performReloc(mem_reloc);
                     try self.genSetReg(addr_reg, ptr_anyopaque_ty, overflow_arg_area);
-                    try self.asmRegisterMemory(.{ ._, .lea }, offset_reg.to64(), Memory.sib(.qword, .{
+                    try self.asmRegisterMemory(.{ ._, .lea }, offset_reg.to64(), .{
                         .base = .{ .reg = addr_reg },
-                        .disp = @intCast(@max(promote_ty.abiSize(mod), 8)),
-                    }));
+                        .mod = .{ .rm = .{
+                            .size = .qword,
+                            .disp = @intCast(@max(promote_ty.abiSize(mod), 8)),
+                        } },
+                    });
                     try self.genCopy(
                         ptr_anyopaque_ty,
                         overflow_arg_area,
@@ -14838,7 +14990,7 @@ fn genTypedValue(self: *Self, arg_tv: TypedValue) InnerError!MCValue {
             .undef => .undef,
             .immediate => |imm| .{ .immediate = imm },
             .memory => |addr| .{ .memory = addr },
-            .load_symbol => |sym_index| .{ .load_symbol = sym_index },
+            .load_symbol => |sym_index| .{ .load_symbol = .{ .sym = sym_index } },
             .load_direct => |sym_index| .{ .load_direct = sym_index },
             .load_got => |sym_index| .{ .lea_got = sym_index },
             .load_tlv => |sym_index| .{ .lea_tlv = sym_index },
@@ -15182,11 +15334,11 @@ fn registerAlias(reg: Register, size_bytes: u32) Register {
     };
 }
 
-fn memPtrSize(self: *Self, ty: Type) Memory.PtrSize {
+fn memSize(self: *Self, ty: Type) Memory.Size {
     const mod = self.bin_file.options.module.?;
     return switch (ty.zigTypeTag(mod)) {
-        .Float => Memory.PtrSize.fromBitSize(ty.floatBits(self.target.*)),
-        else => Memory.PtrSize.fromSize(@intCast(ty.abiSize(mod))),
+        .Float => Memory.Size.fromBitSize(ty.floatBits(self.target.*)),
+        else => Memory.Size.fromSize(@intCast(ty.abiSize(mod))),
     };
 }
 
src/arch/x86_64/Disassembler.zig
@@ -11,7 +11,7 @@ const Encoding = @import("Encoding.zig");
 const Immediate = bits.Immediate;
 const Instruction = encoder.Instruction;
 const LegacyPrefixes = encoder.LegacyPrefixes;
-const Memory = bits.Memory;
+const Memory = Instruction.Memory;
 const Register = bits.Register;
 const Rex = encoder.Rex;
 
src/arch/x86_64/Emit.zig
@@ -1,7 +1,6 @@
 //! This file contains the functionality for emitting x86_64 MIR as machine code
 
 lower: Lower,
-bin_file: *link.File,
 debug_output: DebugInfoOutput,
 code: *std.ArrayList(u8),
 
@@ -41,7 +40,7 @@ pub fn emitMir(emit: *Emit) Error!void {
                     .offset = end_offset - 4,
                     .length = @intCast(end_offset - start_offset),
                 }),
-                .linker_extern_fn => |symbol| if (emit.bin_file.cast(link.File.Elf)) |elf_file| {
+                .linker_extern_fn => |symbol| if (emit.lower.bin_file.cast(link.File.Elf)) |elf_file| {
                     // Add relocation to the decl.
                     const atom_ptr = elf_file.symbol(symbol.atom_index).atom(elf_file).?;
                     try atom_ptr.addReloc(elf_file, .{
@@ -49,9 +48,10 @@ pub fn emitMir(emit: *Emit) Error!void {
                         .r_info = (@as(u64, @intCast(symbol.sym_index)) << 32) | std.elf.R_X86_64_PLT32,
                         .r_addend = -4,
                     });
-                } else if (emit.bin_file.cast(link.File.MachO)) |macho_file| {
+                } else if (emit.lower.bin_file.cast(link.File.MachO)) |macho_file| {
                     // Add relocation to the decl.
-                    const atom_index = macho_file.getAtomIndexForSymbol(.{ .sym_index = symbol.atom_index }).?;
+                    const atom_index =
+                        macho_file.getAtomIndexForSymbol(.{ .sym_index = symbol.atom_index }).?;
                     const target = macho_file.getGlobalByIndex(symbol.sym_index);
                     try link.File.MachO.Atom.addRelocation(macho_file, atom_index, .{
                         .type = .branch,
@@ -61,7 +61,7 @@ pub fn emitMir(emit: *Emit) Error!void {
                         .pcrel = true,
                         .length = 2,
                     });
-                } else if (emit.bin_file.cast(link.File.Coff)) |coff_file| {
+                } else if (emit.lower.bin_file.cast(link.File.Coff)) |coff_file| {
                     // Add relocation to the decl.
                     const atom_index = coff_file.getAtomIndexForSymbol(
                         .{ .sym_index = symbol.atom_index, .file = null },
@@ -76,12 +76,12 @@ pub fn emitMir(emit: *Emit) Error!void {
                         .length = 2,
                     });
                 } else return emit.fail("TODO implement extern reloc for {s}", .{
-                    @tagName(emit.bin_file.tag),
+                    @tagName(emit.lower.bin_file.tag),
                 }),
-                .linker_reloc => |data| if (emit.bin_file.cast(link.File.Elf)) |elf_file| {
+                .linker_reloc => |data| if (emit.lower.bin_file.cast(link.File.Elf)) |elf_file| {
                     const atom = elf_file.symbol(data.atom_index).atom(elf_file).?;
                     const sym = elf_file.symbol(elf_file.zigModulePtr().symbol(data.sym_index));
-                    if (emit.bin_file.options.pic) {
+                    if (emit.lower.bin_file.options.pic) {
                         const r_type: u32 = if (sym.flags.has_zig_got)
                             link.File.Elf.R_X86_64_ZIG_GOTPCREL
                         else if (sym.flags.needs_got)
@@ -111,10 +111,11 @@ pub fn emitMir(emit: *Emit) Error!void {
                 .linker_direct,
                 .linker_import,
                 .linker_tlv,
-                => |symbol| if (emit.bin_file.cast(link.File.Elf)) |_| {
+                => |symbol| if (emit.lower.bin_file.cast(link.File.Elf)) |_| {
                     unreachable;
-                } else if (emit.bin_file.cast(link.File.MachO)) |macho_file| {
-                    const atom_index = macho_file.getAtomIndexForSymbol(.{ .sym_index = symbol.atom_index }).?;
+                } else if (emit.lower.bin_file.cast(link.File.MachO)) |macho_file| {
+                    const atom_index =
+                        macho_file.getAtomIndexForSymbol(.{ .sym_index = symbol.atom_index }).?;
                     try link.File.MachO.Atom.addRelocation(macho_file, atom_index, .{
                         .type = switch (lowered_relocs[0].target) {
                             .linker_got => .got,
@@ -128,7 +129,7 @@ pub fn emitMir(emit: *Emit) Error!void {
                         .pcrel = true,
                         .length = 2,
                     });
-                } else if (emit.bin_file.cast(link.File.Coff)) |coff_file| {
+                } else if (emit.lower.bin_file.cast(link.File.Coff)) |coff_file| {
                     const atom_index = coff_file.getAtomIndexForSymbol(.{
                         .sym_index = symbol.atom_index,
                         .file = null,
@@ -152,7 +153,7 @@ pub fn emitMir(emit: *Emit) Error!void {
                         .pcrel = true,
                         .length = 2,
                     });
-                } else if (emit.bin_file.cast(link.File.Plan9)) |p9_file| {
+                } else if (emit.lower.bin_file.cast(link.File.Plan9)) |p9_file| {
                     const atom_index = symbol.atom_index;
                     try p9_file.addReloc(atom_index, .{ // TODO we may need to add a .type field to the relocs if they are .linker_got instead of just .linker_direct
                         .target = symbol.sym_index, // we set sym_index to just be the atom index
@@ -161,7 +162,7 @@ pub fn emitMir(emit: *Emit) Error!void {
                         .type = .pcrel,
                     });
                 } else return emit.fail("TODO implement linker reloc for {s}", .{
-                    @tagName(emit.bin_file.tag),
+                    @tagName(emit.lower.bin_file.tag),
                 }),
             };
         }
src/arch/x86_64/encoder.zig
@@ -6,9 +6,10 @@ const testing = std.testing;
 
 const bits = @import("bits.zig");
 const Encoding = @import("Encoding.zig");
+const FrameIndex = bits.FrameIndex;
 const Immediate = bits.Immediate;
-const Memory = bits.Memory;
 const Register = bits.Register;
+const Symbol = bits.Symbol;
 
 pub const Instruction = struct {
     prefix: Prefix = .none,
@@ -27,6 +28,97 @@ pub const Instruction = struct {
         repnz,
     };
 
+    pub const Memory = union(enum) {
+        sib: Sib,
+        rip: Rip,
+        moffs: Moffs,
+
+        pub const Base = bits.Memory.Base;
+
+        pub const ScaleIndex = struct {
+            scale: u4,
+            index: Register,
+
+            const none = ScaleIndex{ .scale = 0, .index = undefined };
+        };
+
+        pub const PtrSize = bits.Memory.Size;
+
+        pub const Sib = struct {
+            ptr_size: PtrSize,
+            base: Base,
+            scale_index: ScaleIndex,
+            disp: i32,
+        };
+
+        pub const Rip = struct {
+            ptr_size: PtrSize,
+            disp: i32,
+        };
+
+        pub const Moffs = struct {
+            seg: Register,
+            offset: u64,
+        };
+
+        pub fn moffs(reg: Register, offset: u64) Memory {
+            assert(reg.class() == .segment);
+            return .{ .moffs = .{ .seg = reg, .offset = offset } };
+        }
+
+        pub fn sib(ptr_size: PtrSize, args: struct {
+            disp: i32 = 0,
+            base: Base = .none,
+            scale_index: ?ScaleIndex = null,
+        }) Memory {
+            if (args.scale_index) |si| assert(std.math.isPowerOfTwo(si.scale));
+            return .{ .sib = .{
+                .base = args.base,
+                .disp = args.disp,
+                .ptr_size = ptr_size,
+                .scale_index = if (args.scale_index) |si| si else ScaleIndex.none,
+            } };
+        }
+
+        pub fn rip(ptr_size: PtrSize, disp: i32) Memory {
+            return .{ .rip = .{ .ptr_size = ptr_size, .disp = disp } };
+        }
+
+        pub fn isSegmentRegister(mem: Memory) bool {
+            return switch (mem) {
+                .moffs => true,
+                .rip => false,
+                .sib => |s| switch (s.base) {
+                    .none, .frame, .reloc => false,
+                    .reg => |reg| reg.class() == .segment,
+                },
+            };
+        }
+
+        pub fn base(mem: Memory) Base {
+            return switch (mem) {
+                .moffs => |m| .{ .reg = m.seg },
+                .sib => |s| s.base,
+                .rip => .none,
+            };
+        }
+
+        pub fn scaleIndex(mem: Memory) ?ScaleIndex {
+            return switch (mem) {
+                .moffs, .rip => null,
+                .sib => |s| if (s.scale_index.scale > 0) s.scale_index else null,
+            };
+        }
+
+        pub fn bitSize(mem: Memory) u64 {
+            return switch (mem) {
+                .rip => |r| r.ptr_size.bitSize(),
+                .sib => |s| s.ptr_size.bitSize(),
+                .moffs => 64,
+            };
+        }
+    };
+
     pub const Operand = union(enum) {
         none,
         reg: Register,
@@ -125,8 +217,8 @@ pub const Instruction = struct {
                                 try writer.print("{s}", .{@tagName(reg)});
                                 any = true;
                             },
-                            .frame => |frame| {
-                                try writer.print("{}", .{frame});
+                            inline .frame, .reloc => |payload| {
+                                try writer.print("{}", .{payload});
                                 any = true;
                             },
                         }
@@ -498,7 +590,11 @@ pub const Instruction = struct {
                         }
                     }
                 },
-                .frame => if (@TypeOf(encoder).options.allow_frame_loc) {
+                .frame => if (@TypeOf(encoder).options.allow_frame_locs) {
+                    try encoder.modRm_indirectDisp32(operand_enc, undefined);
+                    try encoder.disp32(undefined);
+                } else return error.CannotEncode,
+                .reloc => if (@TypeOf(encoder).options.allow_symbols) {
                     try encoder.modRm_indirectDisp32(operand_enc, undefined);
                     try encoder.disp32(undefined);
                 } else return error.CannotEncode,
@@ -570,7 +666,7 @@ pub const LegacyPrefixes = packed struct {
     }
 };
 
-pub const Options = struct { allow_frame_loc: bool = false };
+pub const Options = struct { allow_frame_locs: bool = false, allow_symbols: bool = false };
 
 fn Encoder(comptime T: type, comptime opts: Options) type {
     return struct {
@@ -1085,7 +1181,7 @@ test "lower MI encoding" {
     try expectEqualHexStrings("\x49\xC7\xC4\x00\x10\x00\x00", enc.code(), "mov r12, 0x1000");
 
     try enc.encode(.mov, &.{
-        .{ .mem = Memory.sib(.byte, .{ .base = .r12 }) },
+        .{ .mem = Instruction.Memory.sib(.byte, .{ .base = .r12 }) },
         .{ .imm = Immediate.u(0x10) },
     });
     try expectEqualHexStrings("\x41\xC6\x04\x24\x10", enc.code(), "mov BYTE PTR [r12], 0x10");
@@ -1109,13 +1205,13 @@ test "lower MI encoding" {
     try expectEqualHexStrings("\x48\xc7\xc0\x10\x00\x00\x00", enc.code(), "mov rax, 0x10");
 
     try enc.encode(.mov, &.{
-        .{ .mem = Memory.sib(.dword, .{ .base = .r11 }) },
+        .{ .mem = Instruction.Memory.sib(.dword, .{ .base = .r11 }) },
         .{ .imm = Immediate.u(0x10) },
     });
     try expectEqualHexStrings("\x41\xc7\x03\x10\x00\x00\x00", enc.code(), "mov DWORD PTR [r11], 0x10");
 
     try enc.encode(.mov, &.{
-        .{ .mem = Memory.rip(.qword, 0x10) },
+        .{ .mem = Instruction.Memory.rip(.qword, 0x10) },
         .{ .imm = Immediate.u(0x10) },
     });
     try expectEqualHexStrings(
@@ -1125,25 +1221,25 @@ test "lower MI encoding" {
     );
 
     try enc.encode(.mov, &.{
-        .{ .mem = Memory.sib(.qword, .{ .base = .rbp, .disp = -8 }) },
+        .{ .mem = Instruction.Memory.sib(.qword, .{ .base = .rbp, .disp = -8 }) },
         .{ .imm = Immediate.u(0x10) },
     });
     try expectEqualHexStrings("\x48\xc7\x45\xf8\x10\x00\x00\x00", enc.code(), "mov QWORD PTR [rbp - 8], 0x10");
 
     try enc.encode(.mov, &.{
-        .{ .mem = Memory.sib(.word, .{ .base = .rbp, .disp = -2 }) },
+        .{ .mem = Instruction.Memory.sib(.word, .{ .base = .rbp, .disp = -2 }) },
         .{ .imm = Immediate.s(-16) },
     });
     try expectEqualHexStrings("\x66\xC7\x45\xFE\xF0\xFF", enc.code(), "mov WORD PTR [rbp - 2], -16");
 
     try enc.encode(.mov, &.{
-        .{ .mem = Memory.sib(.byte, .{ .base = .rbp, .disp = -1 }) },
+        .{ .mem = Instruction.Memory.sib(.byte, .{ .base = .rbp, .disp = -1 }) },
         .{ .imm = Immediate.u(0x10) },
     });
     try expectEqualHexStrings("\xC6\x45\xFF\x10", enc.code(), "mov BYTE PTR [rbp - 1], 0x10");
 
     try enc.encode(.mov, &.{
-        .{ .mem = Memory.sib(.qword, .{
+        .{ .mem = Instruction.Memory.sib(.qword, .{
             .base = .ds,
             .disp = 0x10000000,
             .scale_index = .{ .scale = 2, .index = .rcx },
@@ -1157,13 +1253,13 @@ test "lower MI encoding" {
     );
 
     try enc.encode(.adc, &.{
-        .{ .mem = Memory.sib(.byte, .{ .base = .rbp, .disp = -0x10 }) },
+        .{ .mem = Instruction.Memory.sib(.byte, .{ .base = .rbp, .disp = -0x10 }) },
         .{ .imm = Immediate.u(0x10) },
     });
     try expectEqualHexStrings("\x80\x55\xF0\x10", enc.code(), "adc BYTE PTR [rbp - 0x10], 0x10");
 
     try enc.encode(.adc, &.{
-        .{ .mem = Memory.rip(.qword, 0) },
+        .{ .mem = Instruction.Memory.rip(.qword, 0) },
         .{ .imm = Immediate.u(0x10) },
     });
     try expectEqualHexStrings("\x48\x83\x15\x00\x00\x00\x00\x10", enc.code(), "adc QWORD PTR [rip], 0x10");
@@ -1175,7 +1271,7 @@ test "lower MI encoding" {
     try expectEqualHexStrings("\x48\x83\xD0\x10", enc.code(), "adc rax, 0x10");
 
     try enc.encode(.add, &.{
-        .{ .mem = Memory.sib(.dword, .{ .base = .rdx, .disp = -8 }) },
+        .{ .mem = Instruction.Memory.sib(.dword, .{ .base = .rdx, .disp = -8 }) },
         .{ .imm = Immediate.u(0x10) },
     });
     try expectEqualHexStrings("\x83\x42\xF8\x10", enc.code(), "add DWORD PTR [rdx - 8], 0x10");
@@ -1187,13 +1283,13 @@ test "lower MI encoding" {
     try expectEqualHexStrings("\x48\x83\xC0\x10", enc.code(), "add rax, 0x10");
 
     try enc.encode(.add, &.{
-        .{ .mem = Memory.sib(.qword, .{ .base = .rbp, .disp = -0x10 }) },
+        .{ .mem = Instruction.Memory.sib(.qword, .{ .base = .rbp, .disp = -0x10 }) },
         .{ .imm = Immediate.s(-0x10) },
     });
     try expectEqualHexStrings("\x48\x83\x45\xF0\xF0", enc.code(), "add QWORD PTR [rbp - 0x10], -0x10");
 
     try enc.encode(.@"and", &.{
-        .{ .mem = Memory.sib(.dword, .{ .base = .ds, .disp = 0x10000000 }) },
+        .{ .mem = Instruction.Memory.sib(.dword, .{ .base = .ds, .disp = 0x10000000 }) },
         .{ .imm = Immediate.u(0x10) },
     });
     try expectEqualHexStrings(
@@ -1203,7 +1299,7 @@ test "lower MI encoding" {
     );
 
     try enc.encode(.@"and", &.{
-        .{ .mem = Memory.sib(.dword, .{ .base = .es, .disp = 0x10000000 }) },
+        .{ .mem = Instruction.Memory.sib(.dword, .{ .base = .es, .disp = 0x10000000 }) },
         .{ .imm = Immediate.u(0x10) },
     });
     try expectEqualHexStrings(
@@ -1213,7 +1309,7 @@ test "lower MI encoding" {
     );
 
     try enc.encode(.@"and", &.{
-        .{ .mem = Memory.sib(.dword, .{ .base = .r12, .disp = 0x10000000 }) },
+        .{ .mem = Instruction.Memory.sib(.dword, .{ .base = .r12, .disp = 0x10000000 }) },
         .{ .imm = Immediate.u(0x10) },
     });
     try expectEqualHexStrings(
@@ -1223,7 +1319,7 @@ test "lower MI encoding" {
     );
 
     try enc.encode(.sub, &.{
-        .{ .mem = Memory.sib(.dword, .{ .base = .r11, .disp = 0x10000000 }) },
+        .{ .mem = Instruction.Memory.sib(.dword, .{ .base = .r11, .disp = 0x10000000 }) },
         .{ .imm = Immediate.u(0x10) },
     });
     try expectEqualHexStrings(
@@ -1238,25 +1334,25 @@ test "lower RM encoding" {
 
     try enc.encode(.mov, &.{
         .{ .reg = .rax },
-        .{ .mem = Memory.sib(.qword, .{ .base = .r11 }) },
+        .{ .mem = Instruction.Memory.sib(.qword, .{ .base = .r11 }) },
     });
     try expectEqualHexStrings("\x49\x8b\x03", enc.code(), "mov rax, QWORD PTR [r11]");
 
     try enc.encode(.mov, &.{
         .{ .reg = .rbx },
-        .{ .mem = Memory.sib(.qword, .{ .base = .ds, .disp = 0x10 }) },
+        .{ .mem = Instruction.Memory.sib(.qword, .{ .base = .ds, .disp = 0x10 }) },
     });
     try expectEqualHexStrings("\x48\x8B\x1C\x25\x10\x00\x00\x00", enc.code(), "mov rbx, QWORD PTR ds:0x10");
 
     try enc.encode(.mov, &.{
         .{ .reg = .rax },
-        .{ .mem = Memory.sib(.qword, .{ .base = .rbp, .disp = -4 }) },
+        .{ .mem = Instruction.Memory.sib(.qword, .{ .base = .rbp, .disp = -4 }) },
     });
     try expectEqualHexStrings("\x48\x8B\x45\xFC", enc.code(), "mov rax, QWORD PTR [rbp - 4]");
 
     try enc.encode(.mov, &.{
         .{ .reg = .rax },
-        .{ .mem = Memory.sib(.qword, .{
+        .{ .mem = Instruction.Memory.sib(.qword, .{
             .base = .rbp,
             .scale_index = .{ .scale = 1, .index = .rcx },
             .disp = -8,
@@ -1266,7 +1362,7 @@ test "lower RM encoding" {
 
     try enc.encode(.mov, &.{
         .{ .reg = .eax },
-        .{ .mem = Memory.sib(.dword, .{
+        .{ .mem = Instruction.Memory.sib(.dword, .{
             .base = .rbp,
             .scale_index = .{ .scale = 4, .index = .rdx },
             .disp = -4,
@@ -1276,7 +1372,7 @@ test "lower RM encoding" {
 
     try enc.encode(.mov, &.{
         .{ .reg = .rax },
-        .{ .mem = Memory.sib(.qword, .{
+        .{ .mem = Instruction.Memory.sib(.qword, .{
             .base = .rbp,
             .scale_index = .{ .scale = 8, .index = .rcx },
             .disp = -8,
@@ -1286,7 +1382,7 @@ test "lower RM encoding" {
 
     try enc.encode(.mov, &.{
         .{ .reg = .r8b },
-        .{ .mem = Memory.sib(.byte, .{
+        .{ .mem = Instruction.Memory.sib(.byte, .{
             .base = .rsi,
             .scale_index = .{ .scale = 1, .index = .rcx },
             .disp = -24,
@@ -1302,7 +1398,7 @@ test "lower RM encoding" {
     try expectEqualHexStrings("\x48\x8C\xC8", enc.code(), "mov rax, cs");
 
     try enc.encode(.mov, &.{
-        .{ .mem = Memory.sib(.qword, .{ .base = .rbp, .disp = -16 }) },
+        .{ .mem = Instruction.Memory.sib(.qword, .{ .base = .rbp, .disp = -16 }) },
         .{ .reg = .fs },
     });
     try expectEqualHexStrings("\x48\x8C\x65\xF0", enc.code(), "mov QWORD PTR [rbp - 16], fs");
@@ -1314,7 +1410,7 @@ test "lower RM encoding" {
     try expectEqualHexStrings("\x66\x41\x8C\xCC", enc.code(), "mov r12w, cs");
 
     try enc.encode(.mov, &.{
-        .{ .mem = Memory.sib(.word, .{ .base = .rbp, .disp = -16 }) },
+        .{ .mem = Instruction.Memory.sib(.word, .{ .base = .rbp, .disp = -16 }) },
         .{ .reg = .fs },
     });
     try expectEqualHexStrings("\x66\x8C\x65\xF0", enc.code(), "mov WORD PTR [rbp - 16], fs");
@@ -1339,19 +1435,19 @@ test "lower RM encoding" {
 
     try enc.encode(.movsx, &.{
         .{ .reg = .eax },
-        .{ .mem = Memory.sib(.word, .{ .base = .rbp }) },
+        .{ .mem = Instruction.Memory.sib(.word, .{ .base = .rbp }) },
     });
     try expectEqualHexStrings("\x0F\xBF\x45\x00", enc.code(), "movsx eax, BYTE PTR [rbp]");
 
     try enc.encode(.movsx, &.{
         .{ .reg = .eax },
-        .{ .mem = Memory.sib(.byte, .{ .scale_index = .{ .index = .rax, .scale = 2 } }) },
+        .{ .mem = Instruction.Memory.sib(.byte, .{ .scale_index = .{ .index = .rax, .scale = 2 } }) },
     });
     try expectEqualHexStrings("\x0F\xBE\x04\x45\x00\x00\x00\x00", enc.code(), "movsx eax, BYTE PTR [rax * 2]");
 
     try enc.encode(.movsx, &.{
         .{ .reg = .ax },
-        .{ .mem = Memory.rip(.byte, 0x10) },
+        .{ .mem = Instruction.Memory.rip(.byte, 0x10) },
     });
     try expectEqualHexStrings("\x66\x0F\xBE\x05\x10\x00\x00\x00", enc.code(), "movsx ax, BYTE PTR [rip + 0x10]");
 
@@ -1369,37 +1465,37 @@ test "lower RM encoding" {
 
     try enc.encode(.lea, &.{
         .{ .reg = .rax },
-        .{ .mem = Memory.rip(.qword, 0x10) },
+        .{ .mem = Instruction.Memory.rip(.qword, 0x10) },
     });
     try expectEqualHexStrings("\x48\x8D\x05\x10\x00\x00\x00", enc.code(), "lea rax, QWORD PTR [rip + 0x10]");
 
     try enc.encode(.lea, &.{
         .{ .reg = .rax },
-        .{ .mem = Memory.rip(.dword, 0x10) },
+        .{ .mem = Instruction.Memory.rip(.dword, 0x10) },
     });
     try expectEqualHexStrings("\x48\x8D\x05\x10\x00\x00\x00", enc.code(), "lea rax, DWORD PTR [rip + 0x10]");
 
     try enc.encode(.lea, &.{
         .{ .reg = .eax },
-        .{ .mem = Memory.rip(.dword, 0x10) },
+        .{ .mem = Instruction.Memory.rip(.dword, 0x10) },
     });
     try expectEqualHexStrings("\x8D\x05\x10\x00\x00\x00", enc.code(), "lea eax, DWORD PTR [rip + 0x10]");
 
     try enc.encode(.lea, &.{
         .{ .reg = .eax },
-        .{ .mem = Memory.rip(.word, 0x10) },
+        .{ .mem = Instruction.Memory.rip(.word, 0x10) },
     });
     try expectEqualHexStrings("\x8D\x05\x10\x00\x00\x00", enc.code(), "lea eax, WORD PTR [rip + 0x10]");
 
     try enc.encode(.lea, &.{
         .{ .reg = .ax },
-        .{ .mem = Memory.rip(.byte, 0x10) },
+        .{ .mem = Instruction.Memory.rip(.byte, 0x10) },
     });
     try expectEqualHexStrings("\x66\x8D\x05\x10\x00\x00\x00", enc.code(), "lea ax, BYTE PTR [rip + 0x10]");
 
     try enc.encode(.lea, &.{
         .{ .reg = .rsi },
-        .{ .mem = Memory.sib(.qword, .{
+        .{ .mem = Instruction.Memory.sib(.qword, .{
             .base = .rbp,
             .scale_index = .{ .scale = 1, .index = .rcx },
         }) },
@@ -1408,31 +1504,31 @@ test "lower RM encoding" {
 
     try enc.encode(.add, &.{
         .{ .reg = .r11 },
-        .{ .mem = Memory.sib(.qword, .{ .base = .ds, .disp = 0x10000000 }) },
+        .{ .mem = Instruction.Memory.sib(.qword, .{ .base = .ds, .disp = 0x10000000 }) },
     });
     try expectEqualHexStrings("\x4C\x03\x1C\x25\x00\x00\x00\x10", enc.code(), "add r11, QWORD PTR ds:0x10000000");
 
     try enc.encode(.add, &.{
         .{ .reg = .r12b },
-        .{ .mem = Memory.sib(.byte, .{ .base = .ds, .disp = 0x10000000 }) },
+        .{ .mem = Instruction.Memory.sib(.byte, .{ .base = .ds, .disp = 0x10000000 }) },
     });
     try expectEqualHexStrings("\x44\x02\x24\x25\x00\x00\x00\x10", enc.code(), "add r11b, BYTE PTR ds:0x10000000");
 
     try enc.encode(.add, &.{
         .{ .reg = .r12b },
-        .{ .mem = Memory.sib(.byte, .{ .base = .fs, .disp = 0x10000000 }) },
+        .{ .mem = Instruction.Memory.sib(.byte, .{ .base = .fs, .disp = 0x10000000 }) },
     });
     try expectEqualHexStrings("\x64\x44\x02\x24\x25\x00\x00\x00\x10", enc.code(), "add r11b, BYTE PTR fs:0x10000000");
 
     try enc.encode(.sub, &.{
         .{ .reg = .r11 },
-        .{ .mem = Memory.sib(.qword, .{ .base = .r13, .disp = 0x10000000 }) },
+        .{ .mem = Instruction.Memory.sib(.qword, .{ .base = .r13, .disp = 0x10000000 }) },
     });
     try expectEqualHexStrings("\x4D\x2B\x9D\x00\x00\x00\x10", enc.code(), "sub r11, QWORD PTR [r13 + 0x10000000]");
 
     try enc.encode(.sub, &.{
         .{ .reg = .r11 },
-        .{ .mem = Memory.sib(.qword, .{ .base = .r12, .disp = 0x10000000 }) },
+        .{ .mem = Instruction.Memory.sib(.qword, .{ .base = .r12, .disp = 0x10000000 }) },
     });
     try expectEqualHexStrings("\x4D\x2B\x9C\x24\x00\x00\x00\x10", enc.code(), "sub r11, QWORD PTR [r12 + 0x10000000]");
 
@@ -1455,7 +1551,7 @@ test "lower RMI encoding" {
 
     try enc.encode(.imul, &.{
         .{ .reg = .r11 },
-        .{ .mem = Memory.rip(.qword, -16) },
+        .{ .mem = Instruction.Memory.rip(.qword, -16) },
         .{ .imm = Immediate.s(-1024) },
     });
     try expectEqualHexStrings(
@@ -1466,7 +1562,7 @@ test "lower RMI encoding" {
 
     try enc.encode(.imul, &.{
         .{ .reg = .bx },
-        .{ .mem = Memory.sib(.word, .{ .base = .rbp, .disp = -16 }) },
+        .{ .mem = Instruction.Memory.sib(.word, .{ .base = .rbp, .disp = -16 }) },
         .{ .imm = Immediate.s(-1024) },
     });
     try expectEqualHexStrings(
@@ -1477,7 +1573,7 @@ test "lower RMI encoding" {
 
     try enc.encode(.imul, &.{
         .{ .reg = .bx },
-        .{ .mem = Memory.sib(.word, .{ .base = .rbp, .disp = -16 }) },
+        .{ .mem = Instruction.Memory.sib(.word, .{ .base = .rbp, .disp = -16 }) },
         .{ .imm = Immediate.u(1024) },
     });
     try expectEqualHexStrings(
@@ -1497,19 +1593,19 @@ test "lower MR encoding" {
     try expectEqualHexStrings("\x48\x89\xD8", enc.code(), "mov rax, rbx");
 
     try enc.encode(.mov, &.{
-        .{ .mem = Memory.sib(.qword, .{ .base = .rbp, .disp = -4 }) },
+        .{ .mem = Instruction.Memory.sib(.qword, .{ .base = .rbp, .disp = -4 }) },
         .{ .reg = .r11 },
     });
     try expectEqualHexStrings("\x4c\x89\x5d\xfc", enc.code(), "mov QWORD PTR [rbp - 4], r11");
 
     try enc.encode(.mov, &.{
-        .{ .mem = Memory.rip(.qword, 0x10) },
+        .{ .mem = Instruction.Memory.rip(.qword, 0x10) },
         .{ .reg = .r12 },
     });
     try expectEqualHexStrings("\x4C\x89\x25\x10\x00\x00\x00", enc.code(), "mov QWORD PTR [rip + 0x10], r12");
 
     try enc.encode(.mov, &.{
-        .{ .mem = Memory.sib(.qword, .{
+        .{ .mem = Instruction.Memory.sib(.qword, .{
             .base = .r11,
             .scale_index = .{ .scale = 2, .index = .r12 },
             .disp = 0x10,
@@ -1519,13 +1615,13 @@ test "lower MR encoding" {
     try expectEqualHexStrings("\x4F\x89\x6C\x63\x10", enc.code(), "mov QWORD PTR [r11 + 2 * r12 + 0x10], r13");
 
     try enc.encode(.mov, &.{
-        .{ .mem = Memory.rip(.word, -0x10) },
+        .{ .mem = Instruction.Memory.rip(.word, -0x10) },
         .{ .reg = .r12w },
     });
     try expectEqualHexStrings("\x66\x44\x89\x25\xF0\xFF\xFF\xFF", enc.code(), "mov WORD PTR [rip - 0x10], r12w");
 
     try enc.encode(.mov, &.{
-        .{ .mem = Memory.sib(.byte, .{
+        .{ .mem = Instruction.Memory.sib(.byte, .{
             .base = .r11,
             .scale_index = .{ .scale = 2, .index = .r12 },
             .disp = 0x10,
@@ -1535,25 +1631,25 @@ test "lower MR encoding" {
     try expectEqualHexStrings("\x47\x88\x6C\x63\x10", enc.code(), "mov BYTE PTR [r11 + 2 * r12 + 0x10], r13b");
 
     try enc.encode(.add, &.{
-        .{ .mem = Memory.sib(.byte, .{ .base = .ds, .disp = 0x10000000 }) },
+        .{ .mem = Instruction.Memory.sib(.byte, .{ .base = .ds, .disp = 0x10000000 }) },
         .{ .reg = .r12b },
     });
     try expectEqualHexStrings("\x44\x00\x24\x25\x00\x00\x00\x10", enc.code(), "add BYTE PTR ds:0x10000000, r12b");
 
     try enc.encode(.add, &.{
-        .{ .mem = Memory.sib(.dword, .{ .base = .ds, .disp = 0x10000000 }) },
+        .{ .mem = Instruction.Memory.sib(.dword, .{ .base = .ds, .disp = 0x10000000 }) },
         .{ .reg = .r12d },
     });
     try expectEqualHexStrings("\x44\x01\x24\x25\x00\x00\x00\x10", enc.code(), "add DWORD PTR [ds:0x10000000], r12d");
 
     try enc.encode(.add, &.{
-        .{ .mem = Memory.sib(.dword, .{ .base = .gs, .disp = 0x10000000 }) },
+        .{ .mem = Instruction.Memory.sib(.dword, .{ .base = .gs, .disp = 0x10000000 }) },
         .{ .reg = .r12d },
     });
     try expectEqualHexStrings("\x65\x44\x01\x24\x25\x00\x00\x00\x10", enc.code(), "add DWORD PTR [gs:0x10000000], r12d");
 
     try enc.encode(.sub, &.{
-        .{ .mem = Memory.sib(.qword, .{ .base = .r11, .disp = 0x10000000 }) },
+        .{ .mem = Instruction.Memory.sib(.qword, .{ .base = .r11, .disp = 0x10000000 }) },
         .{ .reg = .r12 },
     });
     try expectEqualHexStrings("\x4D\x29\xA3\x00\x00\x00\x10", enc.code(), "sub QWORD PTR [r11 + 0x10000000], r12");
@@ -1568,12 +1664,12 @@ test "lower M encoding" {
     try expectEqualHexStrings("\x41\xFF\xD4", enc.code(), "call r12");
 
     try enc.encode(.call, &.{
-        .{ .mem = Memory.sib(.qword, .{ .base = .r12 }) },
+        .{ .mem = Instruction.Memory.sib(.qword, .{ .base = .r12 }) },
     });
     try expectEqualHexStrings("\x41\xFF\x14\x24", enc.code(), "call QWORD PTR [r12]");
 
     try enc.encode(.call, &.{
-        .{ .mem = Memory.sib(.qword, .{
+        .{ .mem = Instruction.Memory.sib(.qword, .{
             .base = null,
             .scale_index = .{ .index = .r11, .scale = 2 },
         }) },
@@ -1581,7 +1677,7 @@ test "lower M encoding" {
     try expectEqualHexStrings("\x42\xFF\x14\x5D\x00\x00\x00\x00", enc.code(), "call QWORD PTR [r11 * 2]");
 
     try enc.encode(.call, &.{
-        .{ .mem = Memory.sib(.qword, .{
+        .{ .mem = Instruction.Memory.sib(.qword, .{
             .base = null,
             .scale_index = .{ .index = .r12, .scale = 2 },
         }) },
@@ -1589,7 +1685,7 @@ test "lower M encoding" {
     try expectEqualHexStrings("\x42\xFF\x14\x65\x00\x00\x00\x00", enc.code(), "call QWORD PTR [r12 * 2]");
 
     try enc.encode(.call, &.{
-        .{ .mem = Memory.sib(.qword, .{ .base = .gs }) },
+        .{ .mem = Instruction.Memory.sib(.qword, .{ .base = .gs }) },
     });
     try expectEqualHexStrings("\x65\xFF\x14\x25\x00\x00\x00\x00", enc.code(), "call gs:0x0");
 
@@ -1599,22 +1695,22 @@ test "lower M encoding" {
     try expectEqualHexStrings("\xE8\x00\x00\x00\x00", enc.code(), "call 0x0");
 
     try enc.encode(.push, &.{
-        .{ .mem = Memory.sib(.qword, .{ .base = .rbp }) },
+        .{ .mem = Instruction.Memory.sib(.qword, .{ .base = .rbp }) },
     });
     try expectEqualHexStrings("\xFF\x75\x00", enc.code(), "push QWORD PTR [rbp]");
 
     try enc.encode(.push, &.{
-        .{ .mem = Memory.sib(.word, .{ .base = .rbp }) },
+        .{ .mem = Instruction.Memory.sib(.word, .{ .base = .rbp }) },
     });
     try expectEqualHexStrings("\x66\xFF\x75\x00", enc.code(), "push QWORD PTR [rbp]");
 
     try enc.encode(.pop, &.{
-        .{ .mem = Memory.rip(.qword, 0) },
+        .{ .mem = Instruction.Memory.rip(.qword, 0) },
     });
     try expectEqualHexStrings("\x8F\x05\x00\x00\x00\x00", enc.code(), "pop QWORD PTR [rip]");
 
     try enc.encode(.pop, &.{
-        .{ .mem = Memory.rip(.word, 0) },
+        .{ .mem = Instruction.Memory.rip(.word, 0) },
     });
     try expectEqualHexStrings("\x66\x8F\x05\x00\x00\x00\x00", enc.code(), "pop WORD PTR [rbp]");
 
@@ -1695,48 +1791,48 @@ test "lower FD/TD encoding" {
 
     try enc.encode(.mov, &.{
         .{ .reg = .rax },
-        .{ .mem = Memory.moffs(.cs, 0x10) },
+        .{ .mem = Instruction.Memory.moffs(.cs, 0x10) },
     });
     try expectEqualHexStrings("\x2E\x48\xA1\x10\x00\x00\x00\x00\x00\x00\x00", enc.code(), "movabs rax, cs:0x10");
 
     try enc.encode(.mov, &.{
         .{ .reg = .eax },
-        .{ .mem = Memory.moffs(.fs, 0x10) },
+        .{ .mem = Instruction.Memory.moffs(.fs, 0x10) },
     });
     try expectEqualHexStrings("\x64\xA1\x10\x00\x00\x00\x00\x00\x00\x00", enc.code(), "movabs eax, fs:0x10");
 
     try enc.encode(.mov, &.{
         .{ .reg = .ax },
-        .{ .mem = Memory.moffs(.gs, 0x10) },
+        .{ .mem = Instruction.Memory.moffs(.gs, 0x10) },
     });
     try expectEqualHexStrings("\x65\x66\xA1\x10\x00\x00\x00\x00\x00\x00\x00", enc.code(), "movabs ax, gs:0x10");
 
     try enc.encode(.mov, &.{
         .{ .reg = .al },
-        .{ .mem = Memory.moffs(.ds, 0x10) },
+        .{ .mem = Instruction.Memory.moffs(.ds, 0x10) },
     });
     try expectEqualHexStrings("\xA0\x10\x00\x00\x00\x00\x00\x00\x00", enc.code(), "movabs al, ds:0x10");
 
     try enc.encode(.mov, &.{
-        .{ .mem = Memory.moffs(.cs, 0x10) },
+        .{ .mem = Instruction.Memory.moffs(.cs, 0x10) },
         .{ .reg = .rax },
     });
     try expectEqualHexStrings("\x2E\x48\xA3\x10\x00\x00\x00\x00\x00\x00\x00", enc.code(), "movabs cs:0x10, rax");
 
     try enc.encode(.mov, &.{
-        .{ .mem = Memory.moffs(.fs, 0x10) },
+        .{ .mem = Instruction.Memory.moffs(.fs, 0x10) },
         .{ .reg = .eax },
     });
     try expectEqualHexStrings("\x64\xA3\x10\x00\x00\x00\x00\x00\x00\x00", enc.code(), "movabs fs:0x10, eax");
 
     try enc.encode(.mov, &.{
-        .{ .mem = Memory.moffs(.gs, 0x10) },
+        .{ .mem = Instruction.Memory.moffs(.gs, 0x10) },
         .{ .reg = .ax },
     });
     try expectEqualHexStrings("\x65\x66\xA3\x10\x00\x00\x00\x00\x00\x00\x00", enc.code(), "movabs gs:0x10, ax");
 
     try enc.encode(.mov, &.{
-        .{ .mem = Memory.moffs(.ds, 0x10) },
+        .{ .mem = Instruction.Memory.moffs(.ds, 0x10) },
         .{ .reg = .al },
     });
     try expectEqualHexStrings("\xA2\x10\x00\x00\x00\x00\x00\x00\x00", enc.code(), "movabs ds:0x10, al");
@@ -1774,16 +1870,16 @@ test "invalid instruction" {
         .{ .reg = .al },
     });
     try invalidInstruction(.call, &.{
-        .{ .mem = Memory.rip(.dword, 0) },
+        .{ .mem = Instruction.Memory.rip(.dword, 0) },
     });
     try invalidInstruction(.call, &.{
-        .{ .mem = Memory.rip(.word, 0) },
+        .{ .mem = Instruction.Memory.rip(.word, 0) },
     });
     try invalidInstruction(.call, &.{
-        .{ .mem = Memory.rip(.byte, 0) },
+        .{ .mem = Instruction.Memory.rip(.byte, 0) },
     });
     try invalidInstruction(.mov, &.{
-        .{ .mem = Memory.rip(.word, 0x10) },
+        .{ .mem = Instruction.Memory.rip(.word, 0x10) },
         .{ .reg = .r12 },
     });
     try invalidInstruction(.lea, &.{
@@ -1792,7 +1888,7 @@ test "invalid instruction" {
     });
     try invalidInstruction(.lea, &.{
         .{ .reg = .al },
-        .{ .mem = Memory.rip(.byte, 0) },
+        .{ .mem = Instruction.Memory.rip(.byte, 0) },
     });
     try invalidInstruction(.pop, &.{
         .{ .reg = .r12b },
@@ -1817,7 +1913,7 @@ fn cannotEncode(mnemonic: Instruction.Mnemonic, ops: []const Instruction.Operand
 
 test "cannot encode" {
     try cannotEncode(.@"test", &.{
-        .{ .mem = Memory.sib(.byte, .{ .base = .r12 }) },
+        .{ .mem = Instruction.Memory.sib(.byte, .{ .base = .r12 }) },
         .{ .reg = .ah },
     });
     try cannotEncode(.@"test", &.{
@@ -2149,8 +2245,8 @@ const Assembler = struct {
         return null;
     }
 
-    fn parseMemory(as: *Assembler) ParseError!Memory {
-        const ptr_size: ?Memory.PtrSize = blk: {
+    fn parseMemory(as: *Assembler) ParseError!Instruction.Memory {
+        const ptr_size: ?Instruction.Memory.PtrSize = blk: {
             const pos = as.it.pos;
             const ptr_size = as.parsePtrSize() catch |err| switch (err) {
                 error.UnexpectedToken => {
@@ -2194,7 +2290,7 @@ const Assembler = struct {
                 if (res.rip) {
                     if (res.base != null or res.scale_index != null or res.offset != null)
                         return error.InvalidMemoryOperand;
-                    return Memory.rip(ptr_size orelse .qword, res.disp orelse 0);
+                    return Instruction.Memory.rip(ptr_size orelse .qword, res.disp orelse 0);
                 }
                 if (res.base) |base| {
                     if (res.rip)
@@ -2202,9 +2298,9 @@ const Assembler = struct {
                     if (res.offset) |offset| {
                         if (res.scale_index != null or res.disp != null)
                             return error.InvalidMemoryOperand;
-                        return Memory.moffs(base, offset);
+                        return Instruction.Memory.moffs(base, offset);
                     }
-                    return Memory.sib(ptr_size orelse .qword, .{
+                    return Instruction.Memory.sib(ptr_size orelse .qword, .{
                         .base = base,
                         .scale_index = res.scale_index,
                         .disp = res.disp orelse 0,
@@ -2222,12 +2318,12 @@ const Assembler = struct {
     const MemoryParseResult = struct {
         rip: bool = false,
         base: ?Register = null,
-        scale_index: ?Memory.ScaleIndex = null,
+        scale_index: ?Instruction.Memory.ScaleIndex = null,
         disp: ?i32 = null,
         offset: ?u64 = null,
     };
 
-    fn parseMemoryRule(as: *Assembler, rule: anytype) ParseError!MemoryParseResult {
+    fn parseMemoryRule(as: *Assembler, rule: anytype) ParseError!Instruction.MemoryParseResult {
         var res: MemoryParseResult = .{};
         inline for (rule, 0..) |cond, i| {
             if (@typeInfo(@TypeOf(cond)) != .EnumLiteral) {
@@ -2294,7 +2390,7 @@ const Assembler = struct {
         return res;
     }
 
-    fn parsePtrSize(as: *Assembler) ParseError!Memory.PtrSize {
+    fn parsePtrSize(as: *Assembler) ParseError!Instruction.Memory.PtrSize {
         const size = try as.expect(.string);
         try as.skip(1, .{.space});
         const ptr = try as.expect(.string);
src/arch/x86_64/Encoding.zig
@@ -803,7 +803,10 @@ fn estimateInstructionLength(prefix: Prefix, encoding: Encoding, ops: []const Op
     @memcpy(inst.ops[0..ops.len], ops);
 
     var cwriter = std.io.countingWriter(std.io.null_writer);
-    inst.encode(cwriter.writer(), .{ .allow_frame_loc = true }) catch unreachable; // Not allowed to fail here unless OOM.
+    inst.encode(cwriter.writer(), .{
+        .allow_frame_locs = true,
+        .allow_symbols = true,
+    }) catch unreachable; // Not allowed to fail here unless OOM.
     return @as(usize, @intCast(cwriter.bytes_written));
 }
 
src/arch/x86_64/Lower.zig
@@ -50,12 +50,12 @@ pub const Reloc = struct {
 
     const Target = union(enum) {
         inst: Mir.Inst.Index,
-        linker_reloc: Mir.Reloc,
-        linker_extern_fn: Mir.Reloc,
-        linker_got: Mir.Reloc,
-        linker_direct: Mir.Reloc,
-        linker_import: Mir.Reloc,
-        linker_tlv: Mir.Reloc,
+        linker_reloc: bits.Symbol,
+        linker_extern_fn: bits.Symbol,
+        linker_got: bits.Symbol,
+        linker_direct: bits.Symbol,
+        linker_import: bits.Symbol,
+        linker_tlv: bits.Symbol,
     };
 };
 
@@ -99,17 +99,15 @@ pub fn lowerMir(lower: *Lower, index: Mir.Inst.Index) Error!struct {
                     .{ .reg = inst.data.rr.r2 },
                 });
             },
-            .pseudo_cmov_nz_or_p_rm_sib,
-            .pseudo_cmov_nz_or_p_rm_rip,
-            => {
+            .pseudo_cmov_nz_or_p_rm => {
                 assert(inst.data.rx.fixes == ._);
                 try lower.emit(.none, .cmovnz, &.{
                     .{ .reg = inst.data.rx.r1 },
-                    .{ .mem = lower.mem(inst.ops, inst.data.rx.payload) },
+                    .{ .mem = lower.mem(inst.data.rx.payload) },
                 });
                 try lower.emit(.none, .cmovp, &.{
                     .{ .reg = inst.data.rx.r1 },
-                    .{ .mem = lower.mem(inst.ops, inst.data.rx.payload) },
+                    .{ .mem = lower.mem(inst.data.rx.payload) },
                 });
             },
             .pseudo_set_z_and_np_r => {
@@ -125,18 +123,16 @@ pub fn lowerMir(lower: *Lower, index: Mir.Inst.Index) Error!struct {
                     .{ .reg = inst.data.rr.r2 },
                 });
             },
-            .pseudo_set_z_and_np_m_sib,
-            .pseudo_set_z_and_np_m_rip,
-            => {
+            .pseudo_set_z_and_np_m => {
                 assert(inst.data.rx.fixes == ._);
                 try lower.emit(.none, .setz, &.{
-                    .{ .mem = lower.mem(inst.ops, inst.data.rx.payload) },
+                    .{ .mem = lower.mem(inst.data.rx.payload) },
                 });
                 try lower.emit(.none, .setnp, &.{
                     .{ .reg = inst.data.rx.r1 },
                 });
                 try lower.emit(.none, .@"and", &.{
-                    .{ .mem = lower.mem(inst.ops, inst.data.rx.payload) },
+                    .{ .mem = lower.mem(inst.data.rx.payload) },
                     .{ .reg = inst.data.rx.r1 },
                 });
             },
@@ -153,18 +149,16 @@ pub fn lowerMir(lower: *Lower, index: Mir.Inst.Index) Error!struct {
                     .{ .reg = inst.data.rr.r2 },
                 });
             },
-            .pseudo_set_nz_or_p_m_sib,
-            .pseudo_set_nz_or_p_m_rip,
-            => {
+            .pseudo_set_nz_or_p_m => {
                 assert(inst.data.rx.fixes == ._);
                 try lower.emit(.none, .setnz, &.{
-                    .{ .mem = lower.mem(inst.ops, inst.data.rx.payload) },
+                    .{ .mem = lower.mem(inst.data.rx.payload) },
                 });
                 try lower.emit(.none, .setp, &.{
                     .{ .reg = inst.data.rx.r1 },
                 });
                 try lower.emit(.none, .@"or", &.{
-                    .{ .mem = lower.mem(inst.ops, inst.data.rx.payload) },
+                    .{ .mem = lower.mem(inst.data.rx.payload) },
                     .{ .reg = inst.data.rx.r1 },
                 });
             },
@@ -289,28 +283,20 @@ fn imm(lower: Lower, ops: Mir.Inst.Ops, i: u32) Immediate {
         .rri_s,
         .ri_s,
         .i_s,
-        .mi_sib_s,
-        .mi_rip_s,
-        .rmi_sib_s,
-        .rmi_rip_s,
+        .mi_s,
+        .rmi_s,
         => Immediate.s(@bitCast(i)),
 
         .rrri,
         .rri_u,
         .ri_u,
         .i_u,
-        .mi_sib_u,
-        .mi_rip_u,
-        .rmi_sib,
-        .rmi_rip,
-        .rmi_sib_u,
-        .rmi_rip_u,
-        .mri_sib,
-        .mri_rip,
-        .rrm_sib,
-        .rrm_rip,
-        .rrmi_sib,
-        .rrmi_rip,
+        .mi_u,
+        .rmi,
+        .rmi_u,
+        .mri,
+        .rrm,
+        .rrmi,
         => Immediate.u(i),
 
         .ri64 => Immediate.u(lower.mir.extraData(Mir.Imm64, i).data.decode()),
@@ -319,50 +305,8 @@ fn imm(lower: Lower, ops: Mir.Inst.Ops, i: u32) Immediate {
     };
 }
 
-fn mem(lower: Lower, ops: Mir.Inst.Ops, payload: u32) Memory {
-    return lower.mir.resolveFrameLoc(switch (ops) {
-        .rm_sib,
-        .rmi_sib,
-        .rmi_sib_s,
-        .rmi_sib_u,
-        .m_sib,
-        .mi_sib_u,
-        .mi_sib_s,
-        .mr_sib,
-        .mrr_sib,
-        .mri_sib,
-        .rrm_sib,
-        .rrmi_sib,
-
-        .pseudo_cmov_nz_or_p_rm_sib,
-        .pseudo_set_z_and_np_m_sib,
-        .pseudo_set_nz_or_p_m_sib,
-        => lower.mir.extraData(Mir.MemorySib, payload).data.decode(),
-
-        .rm_rip,
-        .rmi_rip,
-        .rmi_rip_s,
-        .rmi_rip_u,
-        .m_rip,
-        .mi_rip_u,
-        .mi_rip_s,
-        .mr_rip,
-        .mrr_rip,
-        .mri_rip,
-        .rrm_rip,
-        .rrmi_rip,
-
-        .pseudo_cmov_nz_or_p_rm_rip,
-        .pseudo_set_z_and_np_m_rip,
-        .pseudo_set_nz_or_p_m_rip,
-        => lower.mir.extraData(Mir.MemoryRip, payload).data.decode(),
-
-        .rax_moffs,
-        .moffs_rax,
-        => lower.mir.extraData(Mir.MemoryMoffs, payload).data.decode(),
-
-        else => unreachable,
-    });
+fn mem(lower: Lower, payload: u32) Memory {
+    return lower.mir.resolveFrameLoc(lower.mir.extraData(Mir.Memory, payload).data).decode();
 }
 
 fn reloc(lower: *Lower, target: Reloc.Target) Immediate {
@@ -375,7 +319,42 @@ fn reloc(lower: *Lower, target: Reloc.Target) Immediate {
 }
 
 fn emit(lower: *Lower, prefix: Prefix, mnemonic: Mnemonic, ops: []const Operand) Error!void {
-    lower.result_insts[lower.result_insts_len] = try Instruction.new(prefix, mnemonic, ops);
+    var emit_prefix = prefix;
+    var emit_mnemonic = mnemonic;
+    var emit_ops_storage: [4]Operand = undefined;
+    const emit_ops = emit_ops_storage[0..ops.len];
+    for (emit_ops, ops) |*emit_op, op| {
+        emit_op.* = switch (op) {
+            else => op,
+            .mem => |mem_op| switch (mem_op.base()) {
+                else => op,
+                .reloc => |sym| op: {
+                    assert(prefix == .none);
+                    assert(mem_op.sib.disp == 0);
+                    assert(mem_op.sib.scale_index.scale == 0);
+                    _ = lower.reloc(.{ .linker_reloc = sym });
+                    break :op if (lower.bin_file.options.pic) switch (mnemonic) {
+                        .mov, .lea => .{ .mem = Memory.rip(mem_op.sib.ptr_size, 0) },
+                        else => unreachable,
+                    } else switch (mnemonic) {
+                        .call => .{ .mem = Memory.sib(mem_op.sib.ptr_size, .{
+                            .base = .{ .reg = .ds },
+                        }) },
+                        .lea => {
+                            emit_mnemonic = .mov;
+                            break :op .{ .imm = Immediate.s(0) };
+                        },
+                        .mov => .{ .mem = Memory.sib(mem_op.sib.ptr_size, .{
+                            .base = .{ .reg = .ds },
+                        }) },
+                        else => unreachable,
+                    };
+                },
+            },
+        };
+    }
+    lower.result_insts[lower.result_insts_len] =
+        try Instruction.new(emit_prefix, emit_mnemonic, emit_ops);
     lower.result_insts_len += 1;
 }
 
@@ -391,74 +370,13 @@ fn generic(lower: *Lower, inst: Mir.Inst) Error!void {
         .rrri => inst.data.rrri.fixes,
         .rri_s, .rri_u => inst.data.rri.fixes,
         .ri_s, .ri_u => inst.data.ri.fixes,
-        .ri64,
-        .rm_sib,
-        .rm_rip,
-        .rmi_sib_s,
-        .rmi_sib_u,
-        .rmi_rip_s,
-        .rmi_rip_u,
-        .mr_sib,
-        .mr_rip,
-        => inst.data.rx.fixes,
-        .mrr_sib, .mrr_rip, .rrm_sib, .rrm_rip => inst.data.rrx.fixes,
-        .rmi_sib, .rmi_rip, .mri_sib, .mri_rip => inst.data.rix.fixes,
-        .rrmi_sib, .rrmi_rip => inst.data.rrix.fixes,
-        .mi_sib_u, .mi_rip_u, .mi_sib_s, .mi_rip_s => inst.data.x.fixes,
-        .m_sib, .m_rip, .rax_moffs, .moffs_rax => inst.data.x.fixes,
-        .extern_fn_reloc,
-        .got_reloc,
-        .direct_reloc,
-        .import_reloc,
-        .tlv_reloc,
-        => ._,
-        .linker_reloc => {
-            if (lower.bin_file.options.pic) {
-                assert(inst.data.rx.fixes == ._);
-                const reg = inst.data.rx.r1;
-                const extra = lower.mir.extraData(Mir.Reloc, inst.data.rx.payload).data;
-                _ = lower.reloc(.{ .linker_reloc = extra });
-                const mnemonic: Mnemonic = switch (inst.tag) {
-                    .mov => .mov,
-                    .lea => .lea,
-                    else => unreachable,
-                };
-                try lower.emit(.none, mnemonic, &.{
-                    .{ .reg = reg },
-                    .{ .mem = Memory.rip(Memory.PtrSize.fromBitSize(reg.bitSize()), 0) },
-                });
-            } else {
-                switch (inst.tag) {
-                    .call => {
-                        _ = lower.reloc(.{ .linker_reloc = inst.data.reloc });
-                        try lower.emit(.none, .call, &.{
-                            .{ .mem = Memory.sib(.qword, .{ .base = .{ .reg = .ds }, .disp = 0 }) },
-                        });
-                    },
-                    .lea => {
-                        assert(inst.data.rx.fixes == ._);
-                        const reg = inst.data.rx.r1;
-                        const extra = lower.mir.extraData(Mir.Reloc, inst.data.rx.payload).data;
-                        try lower.emit(.none, .mov, &.{
-                            .{ .reg = reg },
-                            .{ .imm = lower.reloc(.{ .linker_reloc = extra }) },
-                        });
-                    },
-                    .mov => {
-                        assert(inst.data.rx.fixes == ._);
-                        const reg = inst.data.rx.r1;
-                        const extra = lower.mir.extraData(Mir.Reloc, inst.data.rx.payload).data;
-                        _ = lower.reloc(.{ .linker_reloc = extra });
-                        try lower.emit(.none, .mov, &.{
-                            .{ .reg = reg },
-                            .{ .mem = Memory.sib(.qword, .{ .base = .{ .reg = .ds }, .disp = 0 }) },
-                        });
-                    },
-                    else => return lower.fail("TODO lower {s} {s}", .{ @tagName(inst.tag), @tagName(inst.ops) }),
-                }
-            }
-            return;
-        },
+        .ri64, .rm, .rmi_s, .mr => inst.data.rx.fixes,
+        .mrr, .rrm => inst.data.rrx.fixes,
+        .rmi, .mri => inst.data.rix.fixes,
+        .rrmi => inst.data.rrix.fixes,
+        .mi_u, .mi_s => inst.data.x.fixes,
+        .m => inst.data.x.fixes,
+        .extern_fn_reloc, .got_reloc, .direct_reloc, .import_reloc, .tlv_reloc => ._,
         else => return lower.fail("TODO lower .{s}", .{@tagName(inst.ops)}),
     };
     try lower.emit(switch (fixes) {
@@ -527,73 +445,64 @@ fn generic(lower: *Lower, inst: Mir.Inst) Error!void {
             .{ .reg = inst.data.rri.r2 },
             .{ .imm = lower.imm(inst.ops, inst.data.rri.i) },
         },
-        .m_sib, .m_rip => &.{
-            .{ .mem = lower.mem(inst.ops, inst.data.x.payload) },
+        .m => &.{
+            .{ .mem = lower.mem(inst.data.x.payload) },
         },
-        .mi_sib_s, .mi_sib_u, .mi_rip_s, .mi_rip_u => &.{
-            .{ .mem = lower.mem(inst.ops, inst.data.x.payload + 1) },
+        .mi_s, .mi_u => &.{
+            .{ .mem = lower.mem(inst.data.x.payload + 1) },
             .{ .imm = lower.imm(
                 inst.ops,
                 lower.mir.extraData(Mir.Imm32, inst.data.x.payload).data.imm,
             ) },
         },
-        .rm_sib, .rm_rip => &.{
+        .rm => &.{
             .{ .reg = inst.data.rx.r1 },
-            .{ .mem = lower.mem(inst.ops, inst.data.rx.payload) },
+            .{ .mem = lower.mem(inst.data.rx.payload) },
         },
-        .rmi_sib, .rmi_rip => &.{
+        .rmi => &.{
             .{ .reg = inst.data.rix.r1 },
-            .{ .mem = lower.mem(inst.ops, inst.data.rix.payload) },
+            .{ .mem = lower.mem(inst.data.rix.payload) },
             .{ .imm = lower.imm(inst.ops, inst.data.rix.i) },
         },
-        .rmi_sib_s, .rmi_sib_u, .rmi_rip_s, .rmi_rip_u => &.{
+        .rmi_s, .rmi_u => &.{
             .{ .reg = inst.data.rx.r1 },
-            .{ .mem = lower.mem(inst.ops, inst.data.rx.payload + 1) },
+            .{ .mem = lower.mem(inst.data.rx.payload + 1) },
             .{ .imm = lower.imm(
                 inst.ops,
                 lower.mir.extraData(Mir.Imm32, inst.data.rx.payload).data.imm,
             ) },
         },
-        .mr_sib, .mr_rip => &.{
-            .{ .mem = lower.mem(inst.ops, inst.data.rx.payload) },
+        .mr => &.{
+            .{ .mem = lower.mem(inst.data.rx.payload) },
             .{ .reg = inst.data.rx.r1 },
         },
-        .mrr_sib, .mrr_rip => &.{
-            .{ .mem = lower.mem(inst.ops, inst.data.rrx.payload) },
+        .mrr => &.{
+            .{ .mem = lower.mem(inst.data.rrx.payload) },
             .{ .reg = inst.data.rrx.r1 },
             .{ .reg = inst.data.rrx.r2 },
         },
-        .mri_sib, .mri_rip => &.{
-            .{ .mem = lower.mem(inst.ops, inst.data.rix.payload) },
+        .mri => &.{
+            .{ .mem = lower.mem(inst.data.rix.payload) },
             .{ .reg = inst.data.rix.r1 },
             .{ .imm = lower.imm(inst.ops, inst.data.rix.i) },
         },
-        .rrm_sib, .rrm_rip => &.{
+        .rrm => &.{
             .{ .reg = inst.data.rrx.r1 },
             .{ .reg = inst.data.rrx.r2 },
-            .{ .mem = lower.mem(inst.ops, inst.data.rrx.payload) },
+            .{ .mem = lower.mem(inst.data.rrx.payload) },
         },
-        .rrmi_sib, .rrmi_rip => &.{
+        .rrmi => &.{
             .{ .reg = inst.data.rrix.r1 },
             .{ .reg = inst.data.rrix.r2 },
-            .{ .mem = lower.mem(inst.ops, inst.data.rrix.payload) },
+            .{ .mem = lower.mem(inst.data.rrix.payload) },
             .{ .imm = lower.imm(inst.ops, inst.data.rrix.i) },
         },
-        .rax_moffs => &.{
-            .{ .reg = .rax },
-            .{ .mem = lower.mem(inst.ops, inst.data.x.payload) },
-        },
-        .moffs_rax => &.{
-            .{ .mem = lower.mem(inst.ops, inst.data.x.payload) },
-            .{ .reg = .rax },
-        },
         .extern_fn_reloc => &.{
             .{ .imm = lower.reloc(.{ .linker_extern_fn = inst.data.reloc }) },
         },
-        .linker_reloc => unreachable,
         .got_reloc, .direct_reloc, .import_reloc, .tlv_reloc => ops: {
             const reg = inst.data.rx.r1;
-            const extra = lower.mir.extraData(Mir.Reloc, inst.data.rx.payload).data;
+            const extra = lower.mir.extraData(bits.Symbol, inst.data.rx.payload).data;
             _ = lower.reloc(switch (inst.ops) {
                 .got_reloc => .{ .linker_got = extra },
                 .direct_reloc => .{ .linker_direct = extra },
@@ -635,7 +544,7 @@ const ErrorMsg = Module.ErrorMsg;
 const Immediate = bits.Immediate;
 const Instruction = encoder.Instruction;
 const Lower = @This();
-const Memory = bits.Memory;
+const Memory = Instruction.Memory;
 const Mir = @import("Mir.zig");
 const Mnemonic = Instruction.Mnemonic;
 const Module = @import("../../Module.zig");
src/arch/x86_64/Mir.zig
@@ -17,7 +17,6 @@ const encoder = @import("encoder.zig");
 const Air = @import("../../Air.zig");
 const CodeGen = @import("CodeGen.zig");
 const IntegerBitSet = std.bit_set.IntegerBitSet;
-const Memory = bits.Memory;
 const Register = bits.Register;
 
 instructions: std.MultiArrayList(Inst).Slice,
@@ -767,84 +766,42 @@ pub const Inst = struct {
         /// Relative displacement operand.
         /// Uses `imm` payload.
         rel,
-        /// Register, memory (SIB) operands.
+        /// Register, memory operands.
         /// Uses `rx` payload.
-        rm_sib,
-        /// Register, memory (RIP) operands.
-        /// Uses `rx` payload.
-        rm_rip,
-        /// Register, memory (SIB), immediate (word) operands.
-        /// Uses `rix` payload with extra data of type `MemorySib`.
-        rmi_sib,
-        /// Register, memory (RIP), immediate (word) operands.
-        /// Uses `rix` payload with extra data of type `MemoryRip`.
-        rmi_rip,
-        /// Register, memory (SIB), immediate (signed) operands.
-        /// Uses `rx` payload with extra data of type `Imm32` followed by `MemorySib`.
-        rmi_sib_s,
-        /// Register, memory (SIB), immediate (unsigned) operands.
-        /// Uses `rx` payload with extra data of type `Imm32` followed by `MemorySib`.
-        rmi_sib_u,
-        /// Register, memory (RIP), immediate (signed) operands.
-        /// Uses `rx` payload with extra data of type `Imm32` followed by `MemoryRip`.
-        rmi_rip_s,
-        /// Register, memory (RIP), immediate (unsigned) operands.
-        /// Uses `rx` payload with extra data of type `Imm32` followed by `MemoryRip`.
-        rmi_rip_u,
-        /// Register, register, memory (RIP).
-        /// Uses `rrix` payload with extra data of type `MemoryRip`.
-        rrm_rip,
-        /// Register, register, memory (SIB).
-        /// Uses `rrix` payload with extra data of type `MemorySib`.
-        rrm_sib,
-        /// Register, register, memory (RIP), immediate (byte) operands.
-        /// Uses `rrix` payload with extra data of type `MemoryRip`.
-        rrmi_rip,
-        /// Register, register, memory (SIB), immediate (byte) operands.
-        /// Uses `rrix` payload with extra data of type `MemorySib`.
-        rrmi_sib,
-        /// Single memory (SIB) operand.
-        /// Uses `x` with extra data of type `MemorySib`.
-        m_sib,
-        /// Single memory (RIP) operand.
-        /// Uses `x` with extra data of type `MemoryRip`.
-        m_rip,
-        /// Memory (SIB), immediate (sign-extend) operands.
-        /// Uses `x` payload with extra data of type `Imm32` followed by `MemorySib`.
-        mi_sib_s,
-        /// Memory (SIB), immediate (unsigned) operands.
-        /// Uses `x` payload with extra data of type `Imm32` followed by `MemorySib`.
-        mi_sib_u,
-        /// Memory (RIP), immediate (sign-extend) operands.
-        /// Uses `x` payload with extra data of type `Imm32` followed by `MemoryRip`.
-        mi_rip_s,
-        /// Memory (RIP), immediate (unsigned) operands.
-        /// Uses `x` payload with extra data of type `Imm32` followed by `MemoryRip`.
-        mi_rip_u,
-        /// Memory (SIB), register operands.
-        /// Uses `rx` payload with extra data of type `MemorySib`.
-        mr_sib,
-        /// Memory (RIP), register operands.
-        /// Uses `rx` payload with extra data of type `MemoryRip`.
-        mr_rip,
-        /// Memory (SIB), register, register operands.
-        /// Uses `rrx` payload with extra data of type `MemorySib`.
-        mrr_sib,
-        /// Memory (RIP), register, register operands.
-        /// Uses `rrx` payload with extra data of type `MemoryRip`.
-        mrr_rip,
-        /// Memory (SIB), register, immediate (word) operands.
-        /// Uses `rix` payload with extra data of type `MemorySib`.
-        mri_sib,
-        /// Memory (RIP), register, immediate (word) operands.
-        /// Uses `rix` payload with extra data of type `MemoryRip`.
-        mri_rip,
-        /// Rax, Memory moffs.
-        /// Uses `x` with extra data of type `MemoryMoffs`.
-        rax_moffs,
-        /// Memory moffs, rax.
-        /// Uses `x` with extra data of type `MemoryMoffs`.
-        moffs_rax,
+        rm,
+        /// Register, memory, immediate (word) operands.
+        /// Uses `rix` payload with extra data of type `Memory`.
+        rmi,
+        /// Register, memory, immediate (signed) operands.
+        /// Uses `rx` payload with extra data of type `Imm32` followed by `Memory`.
+        rmi_s,
+        /// Register, memory, immediate (unsigned) operands.
+        /// Uses `rx` payload with extra data of type `Imm32` followed by `Memory`.
+        rmi_u,
+        /// Register, register, memory.
+        /// Uses `rrix` payload with extra data of type `Memory`.
+        rrm,
+        /// Register, register, memory, immediate (byte) operands.
+        /// Uses `rrix` payload with extra data of type `Memory`.
+        rrmi,
+        /// Single memory operand.
+        /// Uses `x` with extra data of type `Memory`.
+        m,
+        /// Memory, immediate (sign-extend) operands.
+        /// Uses `x` payload with extra data of type `Imm32` followed by `Memory`.
+        mi_s,
+        /// Memory, immediate (unsigned) operands.
+        /// Uses `x` payload with extra data of type `Imm32` followed by `Memory`.
+        mi_u,
+        /// Memory, register operands.
+        /// Uses `rx` payload with extra data of type `Memory`.
+        mr,
+        /// Memory, register, register operands.
+        /// Uses `rrx` payload with extra data of type `Memory`.
+        mrr,
+        /// Memory, register, immediate (word) operands.
+        /// Uses `rix` payload with extra data of type `Memory`.
+        mri,
         /// References another Mir instruction directly.
         /// Uses `inst` payload.
         inst,
@@ -852,20 +809,17 @@ pub const Inst = struct {
         /// Uses `reloc` payload.
         extern_fn_reloc,
         /// Linker relocation - GOT indirection.
-        /// Uses `rx` payload with extra data of type `Reloc`.
+        /// Uses `rx` payload with extra data of type `bits.Symbol`.
         got_reloc,
         /// Linker relocation - direct reference.
-        /// Uses `rx` payload with extra data of type `Reloc`.
+        /// Uses `rx` payload with extra data of type `bits.Symbol`.
         direct_reloc,
         /// Linker relocation - imports table indirection (binding).
-        /// Uses `rx` payload with extra data of type `Reloc`.
+        /// Uses `rx` payload with extra data of type `bits.Symbol`.
         import_reloc,
         /// Linker relocation - threadlocal variable via GOT indirection.
-        /// Uses `rx` payload with extra data of type `Reloc`.
+        /// Uses `rx` payload with extra data of type `bits.Symbol`.
         tlv_reloc,
-        /// Linker relocation.
-        /// Uses `rx` payload with extra data of type `Reloc`.
-        linker_reloc,
 
         // Pseudo instructions:
 
@@ -878,10 +832,7 @@ pub const Inst = struct {
         pseudo_cmov_nz_or_p_rr,
         /// Conditional move if zero flag not set or parity flag set
         /// Uses `rx` payload.
-        pseudo_cmov_nz_or_p_rm_sib,
-        /// Conditional move if zero flag not set or parity flag set
-        /// Uses `rx` payload.
-        pseudo_cmov_nz_or_p_rm_rip,
+        pseudo_cmov_nz_or_p_rm,
         /// Set byte if zero flag set and parity flag not set
         /// Requires a scratch register!
         /// Uses `rr` payload.
@@ -889,11 +840,7 @@ pub const Inst = struct {
         /// Set byte if zero flag set and parity flag not set
         /// Requires a scratch register!
         /// Uses `rx` payload.
-        pseudo_set_z_and_np_m_sib,
-        /// Set byte if zero flag set and parity flag not set
-        /// Requires a scratch register!
-        /// Uses `rx` payload.
-        pseudo_set_z_and_np_m_rip,
+        pseudo_set_z_and_np_m,
         /// Set byte if zero flag not set or parity flag set
         /// Requires a scratch register!
         /// Uses `rr` payload.
@@ -901,11 +848,7 @@ pub const Inst = struct {
         /// Set byte if zero flag not set or parity flag set
         /// Requires a scratch register!
         /// Uses `rx` payload.
-        pseudo_set_nz_or_p_m_sib,
-        /// Set byte if zero flag not set or parity flag set
-        /// Requires a scratch register!
-        /// Uses `rx` payload.
-        pseudo_set_nz_or_p_m_rip,
+        pseudo_set_nz_or_p_m,
         /// Jump if zero flag set and parity flag not set
         /// Uses `inst` payload.
         pseudo_j_z_and_np_inst,
@@ -1036,7 +979,7 @@ pub const Inst = struct {
         /// Relocation for the linker where:
         /// * `atom_index` is the index of the source
         /// * `sym_index` is the index of the target
-        reloc: Reloc,
+        reloc: bits.Symbol,
         /// Debug line and column position
         line_column: struct {
             line: u32,
@@ -1055,14 +998,6 @@ pub const Inst = struct {
     }
 };
 
-/// A linker symbol not yet allocated in VM.
-pub const Reloc = struct {
-    /// Index of the containing atom.
-    atom_index: u32,
-    /// Index into the linker's symbol table.
-    sym_index: u32,
-};
-
 /// Used in conjunction with payload to transfer a list of used registers in a compact manner.
 pub const RegisterList = struct {
     bitset: BitSet = BitSet.initEmpty(),
@@ -1123,100 +1058,94 @@ pub const Imm64 = struct {
     }
 };
 
-// TODO this can be further compacted using packed struct
-pub const MemorySib = struct {
-    /// Size of the pointer.
-    ptr_size: u32,
-    /// Base register tag of type Memory.Base.Tag
-    base_tag: u32,
-    /// Base register of type Register or FrameIndex
+pub const Memory = struct {
+    info: Info,
     base: u32,
-    /// Scale starting at bit 0 and index register starting at bit 4.
-    scale_index: u32,
-    /// Displacement value.
-    disp: i32,
+    off: u32,
+    extra: u32,
+
+    pub const Info = packed struct(u32) {
+        base: @typeInfo(bits.Memory.Base).Union.tag_type.?,
+        mod: @typeInfo(bits.Memory.Mod).Union.tag_type.?,
+        size: bits.Memory.Size,
+        index: Register,
+        scale: bits.Memory.Scale,
+        _: u16 = undefined,
+    };
 
-    pub fn encode(mem: Memory) MemorySib {
-        const sib = mem.sib;
-        assert(sib.scale_index.scale == 0 or std.math.isPowerOfTwo(sib.scale_index.scale));
+    pub fn encode(mem: bits.Memory) Memory {
+        assert(mem.base != .reloc or mem.mod != .off);
         return .{
-            .ptr_size = @intFromEnum(sib.ptr_size),
-            .base_tag = @intFromEnum(sib.base),
-            .base = switch (sib.base) {
+            .info = .{
+                .base = mem.base,
+                .mod = mem.mod,
+                .size = switch (mem.mod) {
+                    .rm => |rm| rm.size,
+                    .off => undefined,
+                },
+                .index = switch (mem.mod) {
+                    .rm => |rm| rm.index,
+                    .off => undefined,
+                },
+                .scale = switch (mem.mod) {
+                    .rm => |rm| rm.scale,
+                    .off => undefined,
+                },
+            },
+            .base = switch (mem.base) {
                 .none => undefined,
-                .reg => |r| @intFromEnum(r),
-                .frame => |fi| @intFromEnum(fi),
+                .reg => |reg| @intFromEnum(reg),
+                .frame => |frame_index| @intFromEnum(frame_index),
+                .reloc => |symbol| symbol.sym_index,
+            },
+            .off = switch (mem.mod) {
+                .rm => |rm| @bitCast(rm.disp),
+                .off => |off| @truncate(off),
             },
-            .scale_index = @as(u32, sib.scale_index.scale) << 0 |
-                @as(u32, if (sib.scale_index.scale > 0)
-                @intFromEnum(sib.scale_index.index)
+            .extra = if (mem.base == .reloc)
+                mem.base.reloc.atom_index
+            else if (mem.mod == .off)
+                @intCast(mem.mod.off >> 32)
             else
-                undefined) << 4,
-            .disp = sib.disp,
+                undefined,
         };
     }
 
-    pub fn decode(msib: MemorySib) Memory {
-        const scale: u4 = @truncate(msib.scale_index);
-        assert(scale == 0 or std.math.isPowerOfTwo(scale));
-        return .{ .sib = .{
-            .ptr_size = @enumFromInt(msib.ptr_size),
-            .base = switch (@as(Memory.Base.Tag, @enumFromInt(msib.base_tag))) {
-                .none => .none,
-                .reg => .{ .reg = @enumFromInt(msib.base) },
-                .frame => .{ .frame = @enumFromInt(msib.base) },
+    pub fn decode(mem: Memory) encoder.Instruction.Memory {
+        switch (mem.info.mod) {
+            .rm => {
+                if (mem.info.base == .reg and @as(Register, @enumFromInt(mem.base)) == .rip) {
+                    assert(mem.info.index == .none and mem.info.scale == .@"1");
+                    return encoder.Instruction.Memory.rip(mem.info.size, @bitCast(mem.off));
+                }
+                return encoder.Instruction.Memory.sib(mem.info.size, .{
+                    .disp = @bitCast(mem.off),
+                    .base = switch (mem.info.base) {
+                        .none => .none,
+                        .reg => .{ .reg = @enumFromInt(mem.base) },
+                        .frame => .{ .frame = @enumFromInt(mem.base) },
+                        .reloc => .{ .reloc = .{ .atom_index = mem.extra, .sym_index = mem.base } },
+                    },
+                    .scale_index = switch (mem.info.index) {
+                        .none => null,
+                        else => |index| .{ .scale = switch (mem.info.scale) {
+                            inline else => |scale| comptime std.fmt.parseInt(
+                                u4,
+                                @tagName(scale),
+                                10,
+                            ) catch unreachable,
+                        }, .index = index },
+                    },
+                });
             },
-            .scale_index = .{
-                .scale = scale,
-                .index = if (scale > 0) @enumFromInt(msib.scale_index >> 4) else undefined,
+            .off => {
+                assert(mem.info.base == .reg);
+                return encoder.Instruction.Memory.moffs(
+                    @enumFromInt(mem.base),
+                    @as(u64, mem.extra) << 32 | mem.off,
+                );
             },
-            .disp = msib.disp,
-        } };
-    }
-};
-
-pub const MemoryRip = struct {
-    /// Size of the pointer.
-    ptr_size: u32,
-    /// Displacement value.
-    disp: i32,
-
-    pub fn encode(mem: Memory) MemoryRip {
-        return .{
-            .ptr_size = @intFromEnum(mem.rip.ptr_size),
-            .disp = mem.rip.disp,
-        };
-    }
-
-    pub fn decode(mrip: MemoryRip) Memory {
-        return .{ .rip = .{
-            .ptr_size = @enumFromInt(mrip.ptr_size),
-            .disp = mrip.disp,
-        } };
-    }
-};
-
-pub const MemoryMoffs = struct {
-    /// Segment register.
-    seg: u32,
-    /// Absolute offset wrt to the segment register split between MSB and LSB parts much like
-    /// `Imm64` payload.
-    msb: u32,
-    lsb: u32,
-
-    pub fn encode(seg: Register, offset: u64) MemoryMoffs {
-        return .{
-            .seg = @intFromEnum(seg),
-            .msb = @truncate(offset >> 32),
-            .lsb = @truncate(offset >> 0),
-        };
-    }
-
-    pub fn decode(moffs: MemoryMoffs) Memory {
-        return .{ .moffs = .{
-            .seg = @enumFromInt(moffs.seg),
-            .offset = @as(u64, moffs.msb) << 32 | @as(u64, moffs.lsb) << 0,
-        } };
+        }
     }
 };
 
@@ -1234,8 +1163,8 @@ pub fn extraData(mir: Mir, comptime T: type, index: u32) struct { data: T, end:
     inline for (fields) |field| {
         @field(result, field.name) = switch (field.type) {
             u32 => mir.extra[i],
-            i32 => @bitCast(mir.extra[i]),
-            else => @compileError("bad field type"),
+            i32, Memory.Info => @bitCast(mir.extra[i]),
+            else => @compileError("bad field type: " ++ field.name ++ ": " ++ @typeName(field.type)),
         };
         i += 1;
     }
@@ -1251,15 +1180,19 @@ pub const FrameLoc = struct {
 };
 
 pub fn resolveFrameLoc(mir: Mir, mem: Memory) Memory {
-    return switch (mem) {
-        .sib => |sib| switch (sib.base) {
-            .none, .reg => mem,
-            .frame => |index| if (mir.frame_locs.len > 0) Memory.sib(sib.ptr_size, .{
-                .base = .{ .reg = mir.frame_locs.items(.base)[@intFromEnum(index)] },
-                .disp = mir.frame_locs.items(.disp)[@intFromEnum(index)] + sib.disp,
-                .scale_index = mem.scaleIndex(),
-            }) else mem,
-        },
-        .rip, .moffs => mem,
+    return switch (mem.info.base) {
+        .none, .reg, .reloc => mem,
+        .frame => if (mir.frame_locs.len > 0) Memory{
+            .info = .{
+                .base = .reg,
+                .mod = mem.info.mod,
+                .size = mem.info.size,
+                .index = mem.info.index,
+                .scale = mem.info.scale,
+            },
+            .base = @intFromEnum(mir.frame_locs.items(.base)[mem.base]),
+            .off = @bitCast(mir.frame_locs.items(.disp)[mem.base] + @as(i32, @bitCast(mem.off))),
+            .extra = mem.extra,
+        } else mem,
     };
 }