[PATCH] D59818: [x86] avoid cmov in movmsk reduction

[Sanjay Patel via Phabricator via llvm-commits]

spatel created this revision.
spatel added reviewers: RKSimon, craig.topper.
Herald added subscribers: jdoerfert, hiraditya, mcrosier.
Herald added a project: LLVM.

This is probably the least important of our movmsk problems, but I'm starting at the bottom to reduce distractions.

We were creating a select_cc which bypasses the select and bitmask codegen optimizations that we have now. If we produce a compare+negate instead, we allow things like neg/sbb carry bit hacks, and in all cases we avoid a cmov. There's no partial register update danger in these sequences because we always produce the zero-register xor ahead of the 'set' if needed.

There seems to be a missing fold for sext of a bool bit here:

  negl %ecx
  movslq %ecx, %rax

...but that's an independent transform.


https://reviews.llvm.org/D59818

Files:
  llvm/lib/Target/X86/X86ISelLowering.cpp
  llvm/test/CodeGen/X86/vector-compare-all_of.ll
  llvm/test/CodeGen/X86/vector-compare-any_of.ll

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