[PATCH] D144284: [X86] Add transform for `(and/or (icmp eq/ne A,-1),(icmp eq/ne A,-1+C))`->`(and/or (icmp eq/ne (and ~A,-1+C),0))`

[Noah Goldstein via Phabricator via llvm-commits]

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This works of `-1+C` is a negative power of 2.

This can be more useful than the `AddAnd` case as `~A` does not
necessarily require materializing a constant. This makes the transform
worth it for X86 vector types.

Alive2 Links:
EQ: https://alive2.llvm.org/ce/z/P6u8cq
NE: https://alive2.llvm.org/ce/z/_Kkqp1


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D144284

Files:
  llvm/include/llvm/CodeGen/TargetLowering.h
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/lib/Target/X86/X86ISelLowering.cpp
  llvm/test/CodeGen/X86/icmp-pow2-dif.ll

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