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llvm: implement packed unions

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Closes #13340
This commit is contained in:
Veikka Tuominen 2022-11-07 18:47:52 +02:00
parent 95f989a05b
commit 61842da9f7
2 changed files with 66 additions and 4 deletions
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48
src/codegen/llvm.zig
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@ -3013,6 +3013,13 @@ pub const DeclGen = struct {
const layout = t.unionGetLayout(target);
const union_obj = t.cast(Type.Payload.Union).?.data;
if (union_obj.layout == .Packed) {
const bitsize = @intCast(c_uint, t.bitSize(target));
const int_llvm_ty = dg.context.intType(bitsize);
gop.value_ptr.* = int_llvm_ty;
return int_llvm_ty;
}
if (layout.payload_size == 0) {
const enum_tag_llvm_ty = try dg.lowerType(union_obj.tag_ty);
gop.value_ptr.* = enum_tag_llvm_ty;
@ -3762,13 +3769,23 @@ pub const DeclGen = struct {
const field_index = tv.ty.unionTagFieldIndex(tag_and_val.tag, dg.module).?;
assert(union_obj.haveFieldTypes());
const field_ty = union_obj.fields.values()[field_index].ty;
if (union_obj.layout == .Packed) {
const non_int_val = try lowerValue(dg, .{ .ty = field_ty, .val = tag_and_val.val });
const ty_bit_size = @intCast(u16, field_ty.bitSize(target));
const small_int_ty = dg.context.intType(ty_bit_size);
const small_int_val = if (field_ty.isPtrAtRuntime())
non_int_val.constPtrToInt(small_int_ty)
else
non_int_val.constBitCast(small_int_ty);
return small_int_val.constZExtOrBitCast(llvm_union_ty);
}
// Sometimes we must make an unnamed struct because LLVM does
// not support bitcasting our payload struct to the true union payload type.
// Instead we use an unnamed struct and every reference to the global
// must pointer cast to the expected type before accessing the union.
var need_unnamed: bool = layout.most_aligned_field != field_index;
const field_ty = union_obj.fields.values()[field_index].ty;
const payload = p: {
if (!field_ty.hasRuntimeBitsIgnoreComptime()) {
const padding_len = @intCast(c_uint, layout.payload_size);
@ -3959,6 +3976,9 @@ pub const DeclGen = struct {
switch (parent_ty.zigTypeTag()) {
.Union => {
bitcast_needed = true;
if (parent_ty.containerLayout() == .Packed) {
break :blk parent_llvm_ptr;
}
const layout = parent_ty.unionGetLayout(target);
if (layout.payload_size == 0) {
@ -5768,7 +5788,21 @@ pub const FuncGen = struct {
},
},
.Union => {
return self.todo("airStructFieldVal byval union", .{});
assert(struct_ty.containerLayout() == .Packed);
const containing_int = struct_llvm_val;
const elem_llvm_ty = try self.dg.lowerType(field_ty);
if (field_ty.zigTypeTag() == .Float) {
const elem_bits = @intCast(c_uint, field_ty.bitSize(target));
const same_size_int = self.context.intType(elem_bits);
const truncated_int = self.builder.buildTrunc(containing_int, same_size_int, "");
return self.builder.buildBitCast(truncated_int, elem_llvm_ty, "");
} else if (field_ty.isPtrAtRuntime()) {
const elem_bits = @intCast(c_uint, field_ty.bitSize(target));
const same_size_int = self.context.intType(elem_bits);
const truncated_int = self.builder.buildTrunc(containing_int, same_size_int, "");
return self.builder.buildIntToPtr(truncated_int, elem_llvm_ty, "");
}
return self.builder.buildTrunc(containing_int, elem_llvm_ty, "");
},
else => unreachable,
}
@ -9510,6 +9544,9 @@ pub const FuncGen = struct {
if (layout.payload_size == 0) {
return self.builder.buildBitCast(union_ptr, result_llvm_ty, "");
}
if (union_ty.containerLayout() == .Packed) {
return self.builder.buildBitCast(union_ptr, result_llvm_ty, "");
}
const payload_index = @boolToInt(layout.tag_align >= layout.payload_align);
const union_llvm_ty = try self.dg.lowerType(union_ty);
const union_field_ptr = self.builder.buildStructGEP(union_llvm_ty, union_ptr, payload_index, "");
@ -10667,7 +10704,10 @@ fn isByRef(ty: Type) bool {
}
return false;
},
.Union => return ty.hasRuntimeBits(),
.Union => switch (ty.containerLayout()) {
.Packed => return false,
else => return ty.hasRuntimeBits(),
},
.ErrorUnion => {
const payload_ty = ty.errorUnionPayload();
if (!payload_ty.hasRuntimeBitsIgnoreComptime()) {

22
test/behavior/union.zig
View File

@ -1366,3 +1366,25 @@ test "union field ptr - zero sized field" {
var u: U = .{ .foo = {} };
U.bar(&u.foo);
}
test "packed union in packed struct" {
if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
const S = packed struct {
nested: packed union {
val: usize,
foo: u32,
},
bar: u32,
fn unpack(self: @This()) usize {
return self.nested.foo;
}
};
const a: S = .{ .nested = .{ .foo = 123 }, .bar = 5 };
try expect(a.unpack() == 123);
}