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Rollup merge of #131523 - nbdd0121:asm, r=compiler-errors

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Fix asm goto with outputs and move it to a separate feature gate

Tracking issue: #119364

This PR addresses 3 aspects of asm goto with outputs:
* Codegen is fixed. My initial implementation has an oversight which cause the output to be only stored in fallthrough path, but not in label blocks.
* Outputs can now be used with `options(noreturn)` if a label block is given.
* All of this is moved to a new feature gate, because we likely want to stabilise `asm_goto` before asm goto with outputs.

`@rustbot` labels: +A-inline-assembly +F-asm
This commit is contained in:
Matthias Krüger 2024-11-25 07:01:37 +01:00 • committed by GitHub
commit c5230d1148
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11 changed files with 178 additions and 50 deletions
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42
compiler/rustc_codegen_llvm/src/asm.rs
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@ -342,24 +342,32 @@ impl<'ll, 'tcx> AsmBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
}
attributes::apply_to_callsite(result, llvm::AttributePlace::Function, &{ attrs });
// Switch to the 'normal' basic block if we did an `invoke` instead of a `call`
if let Some(dest) = dest {
self.switch_to_block(dest);
}
// Write results to outputs. We need to do this for all possible control flow.
//
// Note that `dest` maybe populated with unreachable_block when asm goto with outputs
// is used (because we need to codegen callbr which always needs a destination), so
// here we use the NORETURN option to determine if `dest` should be used.
for block in (if options.contains(InlineAsmOptions::NORETURN) { None } else { Some(dest) })
.into_iter()
.chain(labels.iter().copied().map(Some))
{
if let Some(block) = block {
self.switch_to_block(block);
}
// Write results to outputs
for (idx, op) in operands.iter().enumerate() {
if let InlineAsmOperandRef::Out { reg, place: Some(place), .. }
| InlineAsmOperandRef::InOut { reg, out_place: Some(place), .. } = *op
{
let value = if output_types.len() == 1 {
result
} else {
self.extract_value(result, op_idx[&idx] as u64)
};
let value =
llvm_fixup_output(self, value, reg.reg_class(), &place.layout, instance);
OperandValue::Immediate(value).store(self, place);
for (idx, op) in operands.iter().enumerate() {
if let InlineAsmOperandRef::Out { reg, place: Some(place), .. }
| InlineAsmOperandRef::InOut { reg, out_place: Some(place), .. } = *op
{
let value = if output_types.len() == 1 {
result
} else {
self.extract_value(result, op_idx[&idx] as u64)
};
let value =
llvm_fixup_output(self, value, reg.reg_class(), &place.layout, instance);
OperandValue::Immediate(value).store(self, place);
}
}
}
}