[PATCH] D63675: [InstCombine] Simplify icmp ult/uge (shl %x, C2), C1 iff C1 is power of two -> icmp eq/ne (and %x, (lshr -C1, C2)), 0.

[Huihui Zhang via Phabricator via llvm-commits]

huihuiz created this revision.
huihuiz added reviewers: lebedev.ri, efriedma.
huihuiz added a project: LLVM.
Herald added a subscriber: hiraditya.

Simplify 'shl' inequality test into 'and' equality test.

This pattern happens in the middle-end while simplifying bitfield access,
Exposed in https://reviews.llvm.org/D63505


Repository:
  rL LLVM

https://reviews.llvm.org/D63675

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
  llvm/test/Transforms/InstCombine/pr17827.ll
  llvm/test/Transforms/InstCombine/shl-and-unsigned-cmp-const.ll
  llvm/test/Transforms/InstCombine/shl-unsigned-cmp-const.ll

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