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abi: implement simple unions (MaybeUninit especially).

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Eduard-Mihai Burtescu 2023-03-17 21:13:25 +02:00 committed by Eduard-Mihai Burtescu
parent 3b42427834
commit 396adcaf59
1 changed files with 17 additions and 9 deletions
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26
crates/rustc_codegen_spirv/src/abi.rs
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@ -593,6 +593,8 @@ fn dig_scalar_pointee<'tcx>(
})
}
// FIXME(eddyb) all `ty: TyAndLayout` variables should be `layout: TyAndLayout`,
// the type is really more "Layout with Ty" (`.ty` field + `Deref`s to `Layout`).
fn trans_aggregate<'tcx>(cx: &CodegenCx<'tcx>, span: Span, ty: TyAndLayout<'tcx>) -> Word {
fn create_zst<'tcx>(cx: &CodegenCx<'tcx>, span: Span, ty: TyAndLayout<'tcx>) -> Word {
SpirvType::Adt {
@ -613,16 +615,22 @@ fn trans_aggregate<'tcx>(cx: &CodegenCx<'tcx>, span: Span, ty: TyAndLayout<'tcx>
),
FieldsShape::Union(_) => {
assert!(!ty.is_unsized(), "{ty:#?}");
if ty.size.bytes() == 0 {
create_zst(cx, span, ty)
// Represent the `union` with its largest case, which should work
// for at least `MaybeUninit<T>` (which is between `T` and `()`),
// but also potentially some other ones as well.
// NOTE(eddyb) even if long-term this may become a byte array, that
// only works for "data types" and not "opaque handles" (images etc.).
let largest_case = (0..ty.fields.count())
.map(|i| ty.field(cx, i))
.max_by_key(|case| case.size);
if let Some(case) = largest_case {
assert_eq!(ty.size, case.size);
case.spirv_type(span, cx)
} else {
let byte = SpirvType::Integer(8, false).def(span, cx);
let count = cx.constant_u32(span, ty.size.bytes() as u32);
SpirvType::Array {
element: byte,
count,
}
.def(span, cx)
assert_eq!(ty.size, Size::ZERO);
create_zst(cx, span, ty)
}
}
FieldsShape::Array { stride, count } => {