[PATCH] D130956: [X86][MC] Always emit `rep` prefix for `bsf`

[Aaron Puchert via Phabricator via llvm-commits]

aaronpuchert added a comment.

By the way, the original bug for this is #34191 <https://github.com/llvm/llvm-project/issues/34191>.



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Comment at: llvm/test/CodeGen/X86/peephole-na-phys-copy-folding.ll:376
   %cmp = icmp sgt i32 %val, 0
   %res = tail call i32 asm "bsfl $1,$0", "=r,r,~{cc},~{dirflag},~{fpsr},~{flags}"(i32 %val)
   store i32 %res, ptr %mem, align 4
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Goes a bit too far I think. We can turn a generic builtin into `rep; bsf`, but if the inline assembly explicitly asks for `bsf` I think we should emit that.


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https://reviews.llvm.org/D130956