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Support use of asm goto with outputs and options(noreturn)

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When labels are present, the `noreturn` option really means that asm block
won't fallthrough -- if labels are present, then outputs can still be
meaningfully used.
This commit is contained in:
Gary Guo 2024-10-11 00:26:21 +01:00
parent b8df869ebb
commit 73f8309300
5 changed files with 45 additions and 5 deletions
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5
compiler/rustc_builtin_macros/src/asm.rs
View file

@ -300,7 +300,10 @@ pub fn parse_asm_args<'a>(
if args.options.contains(ast::InlineAsmOptions::PURE) && !have_real_output {
dcx.emit_err(errors::AsmPureNoOutput { spans: args.options_spans.clone() });
}
if args.options.contains(ast::InlineAsmOptions::NORETURN) && !outputs_sp.is_empty() {
if args.options.contains(ast::InlineAsmOptions::NORETURN)
&& !outputs_sp.is_empty()
&& labels_sp.is_empty()
{
let err = dcx.create_err(errors::AsmNoReturn { outputs_sp });
// Bail out now since this is likely to confuse MIR
return Err(err);

9
compiler/rustc_codegen_llvm/src/asm.rs
View file

@ -343,7 +343,14 @@ impl<'ll, 'tcx> AsmBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
attributes::apply_to_callsite(result, llvm::AttributePlace::Function, &{ attrs });
// Write results to outputs. We need to do this for all possible control flow.
for block in Some(dest).into_iter().chain(labels.iter().copied().map(Some)) {
//
// 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);
}