Commit 370662c565
Changed files (3)
src
codegen
test
behavior
src/codegen/llvm.zig
@@ -6179,7 +6179,6 @@ pub const FuncGen = struct {
const elem_alignment = elem_ty.abiAlignment(mod).toLlvm();
return self.loadByRef(elem_ptr, elem_ty, elem_alignment, .normal);
} else {
- const elem_llvm_ty = try o.lowerType(elem_ty);
if (Air.refToIndex(bin_op.lhs)) |lhs_index| {
if (self.air.instructions.items(.tag)[lhs_index] == .load) {
const load_data = self.air.instructions.items(.data)[lhs_index];
@@ -6201,7 +6200,7 @@ pub const FuncGen = struct {
&indices,
"",
);
- return self.wip.load(.normal, elem_llvm_ty, gep, .default, "");
+ return self.loadTruncate(.normal, elem_ty, gep, .default);
},
else => {},
}
@@ -6210,7 +6209,7 @@ pub const FuncGen = struct {
}
const elem_ptr =
try self.wip.gep(.inbounds, array_llvm_ty, array_llvm_val, &indices, "");
- return self.wip.load(.normal, elem_llvm_ty, elem_ptr, .default, "");
+ return self.loadTruncate(.normal, elem_ty, elem_ptr, .default);
}
}
@@ -6378,13 +6377,12 @@ pub const FuncGen = struct {
const payload_index = @intFromBool(layout.tag_align.compare(.gte, layout.payload_align));
const field_ptr =
try self.wip.gepStruct(union_llvm_ty, struct_llvm_val, payload_index, "");
- const llvm_field_ty = try o.lowerType(field_ty);
const payload_alignment = layout.payload_align.toLlvm();
if (isByRef(field_ty, mod)) {
if (canElideLoad(self, body_tail)) return field_ptr;
return self.loadByRef(field_ptr, field_ty, payload_alignment, .normal);
} else {
- return self.wip.load(.normal, llvm_field_ty, field_ptr, payload_alignment, "");
+ return self.loadTruncate(.normal, field_ty, field_ptr, payload_alignment);
}
},
else => unreachable,
@@ -10219,8 +10217,7 @@ pub const FuncGen = struct {
return fg.loadByRef(payload_ptr, payload_ty, payload_alignment, .normal);
}
- const payload_llvm_ty = try o.lowerType(payload_ty);
- return fg.wip.load(.normal, payload_llvm_ty, payload_ptr, payload_alignment, "");
+ return fg.loadTruncate(.normal, payload_ty, payload_ptr, payload_alignment);
}
assert(!isByRef(payload_ty, mod));
@@ -10321,6 +10318,36 @@ pub const FuncGen = struct {
}
}
+ /// Load a value and, if needed, mask out padding bits for non byte-sized integer values.
+ fn loadTruncate(
+ fg: *FuncGen,
+ access_kind: Builder.MemoryAccessKind,
+ payload_ty: Type,
+ payload_ptr: Builder.Value,
+ payload_alignment: Builder.Alignment,
+ ) !Builder.Value {
+ // from https://llvm.org/docs/LangRef.html#load-instruction :
+ // "When loading a value of a type like i20 with a size that is not an integral number of bytes, the result is undefined if the value was not originally written using a store of the same type. "
+ // => so load the byte aligned value and trunc the unwanted bits.
+
+ const o = fg.dg.object;
+ const mod = o.module;
+ const payload_llvm_ty = try o.lowerType(payload_ty);
+ const load_llvm_ty = if (payload_ty.isAbiInt(mod))
+ try o.builder.intType(@intCast(payload_ty.abiSize(mod) * 8))
+ else
+ payload_llvm_ty;
+ const loaded = try fg.wip.load(access_kind, load_llvm_ty, payload_ptr, payload_alignment, "");
+ const shifted = if (payload_llvm_ty != load_llvm_ty and o.target.cpu.arch.endian() == .Big)
+ try fg.wip.bin(.lshr, loaded, try o.builder.intValue(
+ load_llvm_ty,
+ (payload_ty.abiSize(mod) - (std.math.divCeil(u64, payload_ty.bitSize(mod), 8) catch unreachable)) * 8,
+ ), "")
+ else
+ loaded;
+ return fg.wip.conv(.unneeded, shifted, payload_llvm_ty, "");
+ }
+
/// Load a by-ref type by constructing a new alloca and performing a memcpy.
fn loadByRef(
fg: *FuncGen,
@@ -10378,21 +10405,7 @@ pub const FuncGen = struct {
if (isByRef(elem_ty, mod)) {
return self.loadByRef(ptr, elem_ty, ptr_alignment, access_kind);
}
- const llvm_elem_ty = try o.lowerType(elem_ty);
- const llvm_load_ty = if (elem_ty.isAbiInt(mod))
- try o.builder.intType(@intCast(elem_ty.abiSize(mod) * 8))
- else
- llvm_elem_ty;
- const loaded = try self.wip.load(access_kind, llvm_load_ty, ptr, ptr_alignment, "");
- const shifted = if (llvm_elem_ty != llvm_load_ty and o.target.cpu.arch.endian() == .Big)
- try self.wip.bin(.lshr, loaded, try o.builder.intValue(
- llvm_load_ty,
- (elem_ty.abiSize(mod) - (std.math.divCeil(u64, elem_ty.bitSize(mod), 8) catch
- unreachable)) * 8,
- ), "")
- else
- loaded;
- return self.wip.conv(.unneeded, shifted, llvm_elem_ty, "");
+ return self.loadTruncate(access_kind, elem_ty, ptr, ptr_alignment);
}
const containing_int_ty = try o.builder.intType(@intCast(info.packed_offset.host_size * 8));
test/behavior/cast_int.zig
@@ -120,3 +120,106 @@ test "coerce non byte-sized integers accross 32bits boundary" {
}
}
+const Piece = packed struct {
+ color: Color,
+ type: Type,
+
+ const Type = enum { KING, QUEEN, BISHOP, KNIGHT, ROOK, PAWN };
+ const Color = enum { WHITE, BLACK };
+
+ fn charToPiece(c: u8) !@This() {
+ return .{
+ .type = try charToPieceType(c),
+ .color = if (std.ascii.isUpper(c)) Color.WHITE else Color.BLACK,
+ };
+ }
+
+ fn charToPieceType(c: u8) !Type {
+ return switch (std.ascii.toLower(c)) {
+ 'p' => .PAWN,
+ 'k' => .KING,
+ 'q' => .QUEEN,
+ 'b' => .BISHOP,
+ 'n' => .KNIGHT,
+ 'r' => .ROOK,
+ else => error.UnexpectedCharError,
+ };
+ }
+};
+
+test "load non byte-sized optional value" {
+ // Originally reported at https://github.com/ziglang/zig/issues/14200
+ // note: this bug is triggered by the == operator, expectEqual will hide it
+ var opt: ?Piece = try Piece.charToPiece('p');
+ try expect(opt.?.type == .PAWN);
+ try expect(opt.?.color == .BLACK);
+
+ var p: Piece = undefined;
+ @as(*u8, @ptrCast(&p)).* = 0b11111011;
+ try expect(p.type == .PAWN);
+ try expect(p.color == .BLACK);
+}
+
+test "load non byte-sized value in struct" {
+ if (builtin.cpu.arch.endian() != .Little) return error.SkipZigTest; // packed struct TODO
+
+ // note: this bug is triggered by the == operator, expectEqual will hide it
+ // using ptrCast not to depend on unitialised memory state
+
+ var struct0: struct {
+ p: Piece,
+ int: u8,
+ } = undefined;
+ @as(*u8, @ptrCast(&struct0.p)).* = 0b11111011;
+ try expect(struct0.p.type == .PAWN);
+ try expect(struct0.p.color == .BLACK);
+
+ var struct1: packed struct {
+ p0: Piece,
+ p1: Piece,
+ pad: u1,
+ p2: Piece,
+ } = undefined;
+ @as(*u8, @ptrCast(&struct1.p0)).* = 0b11111011;
+ struct1.p1 = try Piece.charToPiece('p');
+ struct1.p2 = try Piece.charToPiece('p');
+ try expect(struct1.p0.type == .PAWN);
+ try expect(struct1.p0.color == .BLACK);
+ try expect(struct1.p1.type == .PAWN);
+ try expect(struct1.p1.color == .BLACK);
+ try expect(struct1.p2.type == .PAWN);
+ try expect(struct1.p2.color == .BLACK);
+}
+
+test "load non byte-sized value in union" {
+ if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
+ if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
+ if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest;
+ if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;
+ if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
+ if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
+
+ // note: this bug is triggered by the == operator, expectEqual will hide it
+ // using ptrCast not to depend on unitialised memory state
+
+ var union0: packed union {
+ p: Piece,
+ int: u8,
+ } = .{ .int = 0 };
+ union0.int = 0b11111011;
+ try expect(union0.p.type == .PAWN);
+ try expect(union0.p.color == .BLACK);
+
+ var union1: union {
+ p: Piece,
+ int: u8,
+ } = .{ .p = .{ .color = .WHITE, .type = .KING } };
+ @as(*u8, @ptrCast(&union1.p)).* = 0b11111011;
+ try expect(union1.p.type == .PAWN);
+ try expect(union1.p.color == .BLACK);
+
+ var pieces: [3]Piece = undefined;
+ @as(*u8, @ptrCast(&pieces[1])).* = 0b11111011;
+ try expect(pieces[1].type == .PAWN);
+ try expect(pieces[1].color == .BLACK);
+}
test/behavior/packed-struct.zig
@@ -991,7 +991,7 @@ test "bitcast back and forth" {
test "field access of packed struct smaller than its abi size inside struct initialized with rls" {
// Originally reported at https://github.com/ziglang/zig/issues/14200
- if (builtin.zig_backend == .stage2_llvm and builtin.cpu.arch == .arm) return error.SkipZigTest;
+
const S = struct {
ps: packed struct { x: i2, y: i2 },