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

[Craig Topper via Phabricator via llvm-commits]

craig.topper added inline comments.


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Comment at: llvm/test/CodeGen/X86/dagcombine-select.ll:310
 ; NOBMI-NEXT:    movq $-1, %rax
 ; NOBMI-NEXT:    cmovneq %rcx, %rax
 ; NOBMI-NEXT:    addq $6, %rax
----------------
This is incorrect. If the instruction is detected as tzcnt, the cmov would need to be cmovaeq not cmovneq. Since we can't know at compile time which CPU we'll be running on. We can't do this transform if the flags are used.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D130956/new/

https://reviews.llvm.org/D130956