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Implement ppc/ppc64 preserves_flags option for inline asm

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Implemented preserves_flags on powerpc by making it do
nothing. This prevents having two different ways to mark
`cr0` as clobbered. clang and gcc alias `cr0` to `cc`.

The gcc inline documentation does not state what this does
on powerpc* targets, but inspection of the source shows
it is equivalent to condition register field `cr0`, so it
should not be added.
This commit is contained in:
Paul Murphy
2025-09-22 09:28:21 -05:00
parent 3c09d4a582
commit 4945d21ed9
2 changed files with 45 additions and 3 deletions
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13
compiler/rustc_codegen_gcc/src/asm.rs
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@@ -546,9 +546,16 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
}
if !options.contains(InlineAsmOptions::PRESERVES_FLAGS) {
// TODO(@Commeownist): I'm not 100% sure this one clobber is sufficient
// on all architectures. For instance, what about FP stack?
extended_asm.add_clobber("cc");
match asm_arch {
InlineAsmArch::PowerPC | InlineAsmArch::PowerPC64 => {
// "cc" is cr0 on powerpc.
}
// TODO(@Commeownist): I'm not 100% sure this one clobber is sufficient
// on all architectures. For instance, what about FP stack?
_ => {
extended_asm.add_clobber("cc");
}
}
}
if !options.contains(InlineAsmOptions::NOMEM) {
extended_asm.add_clobber("memory");