[PATCH] D116811: [SCEVExpander] Skip creating <u 0 check, which is always false.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: reames, nikic, lebedev.ri, mkazantsev.
Herald added a subscriber: hiraditya.
fhahn requested review of this revision.
Herald added a project: LLVM.

Unsigned compares of the form <u 0 are always false. Do not create such
a redundant check in generateOverflowCheck.

The patch introduces a new lambda to create the check, so we can
exit early conveniently and skip creating some instructions feeding the
check.

I am planning to sink a few additional instructions as follow-ups, but I
would prefer to do this separately, to keep the changes and diff
smaller.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D116811

Files:
  llvm/include/llvm/Transforms/Utils/ScalarEvolutionExpander.h
  llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
  llvm/test/Transforms/LoopDistribute/scev-inserted-runtime-check.ll
  llvm/test/Transforms/LoopVectorize/runtime-check-small-clamped-bounds.ll
  llvm/test/Transforms/LoopVersioning/wrapping-pointer-versioning.ll

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