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Allow MaybeUninit in input and output of inline assembly #1481

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Apr 14, 2024
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25 changes: 23 additions & 2 deletions src/inline_asm.rs
Original file line number Diff line number Diff line change
Expand Up @@ -785,9 +785,9 @@ fn call_inline_asm<'tcx>(
for (offset, place) in outputs {
let ty = if place.layout().ty.is_simd() {
let (lane_count, lane_type) = place.layout().ty.simd_size_and_type(fx.tcx);
fx.clif_type(lane_type).unwrap().by(lane_count.try_into().unwrap()).unwrap()
asm_clif_type(fx, lane_type).unwrap().by(lane_count.try_into().unwrap()).unwrap()
} else {
fx.clif_type(place.layout().ty).unwrap()
asm_clif_type(fx, place.layout().ty).unwrap()
};
let value = stack_slot.offset(fx, i32::try_from(offset.bytes()).unwrap().into()).load(
fx,
Expand All @@ -797,3 +797,24 @@ fn call_inline_asm<'tcx>(
place.write_cvalue(fx, CValue::by_val(value, place.layout()));
}
}

fn asm_clif_type<'tcx>(fx: &FunctionCx<'_, '_, 'tcx>, ty: Ty<'tcx>) -> Option<types::Type> {
match ty.kind() {
// Adapted from https://github.com/rust-lang/rust/blob/f3c66088610c1b80110297c2d9a8b5f9265b013f/compiler/rustc_hir_analysis/src/check/intrinsicck.rs#L136-L151
ty::Adt(adt, args) if Some(adt.did()) == fx.tcx.lang_items().maybe_uninit() => {
let fields = &adt.non_enum_variant().fields;
let ty = fields[FieldIdx::from_u32(1)].ty(fx.tcx, args);
let ty::Adt(ty, args) = ty.kind() else {
unreachable!("expected first field of `MaybeUninit` to be an ADT")
};
assert!(
ty.is_manually_drop(),
"expected first field of `MaybeUninit` to be `ManuallyDrop`"
);
let fields = &ty.non_enum_variant().fields;
let ty = fields[FieldIdx::ZERO].ty(fx.tcx, args);
fx.clif_type(ty)
}
_ => fx.clif_type(ty),
}
}