[PATCH] D142542: [InstSimplify] Simplify icmp between Left-Shifted VScale Calls

[Matt Devereau via Phabricator via llvm-commits]

MattDevereau created this revision.
MattDevereau added reviewers: sdesmalen, dtemirbulatov, peterwaller-arm, spatel.
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[InstSimplify] Simplify icmp between Left-Shifted VScale Calls

      

define i1 @compare_vscales() {

  %vscale = call i64 @llvm.vscale.i64()
  %vscalex2 = shl nuw nsw i64 %vscale, 1
  %vscalex4 = shl nuw nsw i64 %vscale, 2
  %cmp = icmp ult i64 %vscalex2, %vscalex4
  ret i1 %cmp

}

      

This IR is currently emitted by LLVM. This icmp is redundant as this snippet
can be simplified to true or false as both operands originate from the same
@llvm.vscale.i64() call.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D142542

Files:
  llvm/lib/Analysis/InstructionSimplify.cpp
  llvm/test/Transforms/InstSimplify/compare.ll

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