[PATCH] D23446: [X86] Enable setcc to srl(ctlz) transformation on btver2 architectures.

[pierre gousseau via llvm-commits]

pgousseau updated this revision to Diff 74136.
pgousseau added a comment.

Following Simon's comments:

- Add an early return in case isCtlzFast is false
- Add a test checking that no transformations occurs on single input cases.
- Prevent transformation on 128-bit cases: int foo(__int128_t a, __int128_t b) { return a || b;} as this pessimized the codegen.
  - This requires constraining the pattern to the X86 form of an equality comparison with 0.
  - This remove the need from the earlier patch to modify isTypeDesirableForOp().


https://reviews.llvm.org/D23446

Files:
  lib/Target/X86/X86.td
  lib/Target/X86/X86ISelLowering.cpp
  lib/Target/X86/X86ISelLowering.h
  lib/Target/X86/X86InstrInfo.td
  lib/Target/X86/X86Subtarget.cpp
  lib/Target/X86/X86Subtarget.h
  test/CodeGen/X86/lzcnt-zext-cmp.ll

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