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LLVM: use unnamed struct llvm type for unions when necessary

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The constant value lowering for unions was missing a check for whether
the payload was itself an unnamed struct. Lowerings of other types
already handle this case.

closes #11971
This commit is contained in:
Andrew Kelley 2022-06-30 15:58:51 -07:00
parent 67db2b85b7
commit c030ec1884
1 changed files with 8 additions and 6 deletions
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14
src/codegen/llvm.zig
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@ -3401,6 +3401,13 @@ pub const DeclGen = struct {
const union_obj = tv.ty.cast(Type.Payload.Union).?.data;
const field_index = union_obj.tag_ty.enumTagFieldIndex(tag_and_val.tag, dg.module).?;
assert(union_obj.haveFieldTypes());
// 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()) {
@ -3408,6 +3415,7 @@ pub const DeclGen = struct {
break :p dg.context.intType(8).arrayType(padding_len).getUndef();
}
const field = try lowerValue(dg, .{ .ty = field_ty, .val = tag_and_val.val });
need_unnamed = need_unnamed or dg.isUnnamedType(field_ty, field);
const field_size = field_ty.abiSize(target);
if (field_size == layout.payload_size) {
break :p field;
@ -3419,12 +3427,6 @@ pub const DeclGen = struct {
break :p dg.context.constStruct(&fields, fields.len, .True);
};
// In this case 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.
const need_unnamed = layout.most_aligned_field != field_index;
if (layout.tag_size == 0) {
const fields: [1]*const llvm.Value = .{payload};
if (need_unnamed) {