[PATCH] D142783: [InstCombine][LV][WIP] Fold (add (zext (add X, -1)), 1) -> (zext X) if X is non-zero.

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
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This artifact can appear from the vectorizer. (add X, -1) is the
backedge taken count. It gets zero extended and then 1 is added to
it to get the trip count.

There is usually a dominating branch that rules out X being zero.

Alternatively, we could try to fix this in the vectorizer or the
SCEV expander maybe?


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D142783

Files:
  llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
  llvm/test/Transforms/LoopVectorize/AArch64/intrinsiccost.ll
  llvm/test/Transforms/LoopVectorize/X86/intrinsiccost.ll
  llvm/test/Transforms/LoopVectorize/X86/small-size.ll
  llvm/test/Transforms/LoopVectorize/float-induction.ll
  llvm/test/Transforms/LoopVectorize/if-conversion-nest.ll
  llvm/test/Transforms/LoopVectorize/runtime-check.ll

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