[PATCH] D154157: [LV] Cost model for out-of-loop reductions

[Anna Thomas via Phabricator via llvm-commits]

anna created this revision.
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When we have small trip count loops, the cost of out of loop reduction
becomes significant. We do not consider the cost of out of loop
reductions in loop vectorizer (in-loop vectorizations are handled in
cost modelling).

This patch introduces a TTI hook to consider if we should vectorize
small trip counts when we have reductions being vectorized.

Added an X86 test which shows the patch avoids vectorizing the loop.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D154157

Files:
  llvm/include/llvm/Analysis/TargetTransformInfo.h
  llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
  llvm/lib/Analysis/TargetTransformInfo.cpp
  llvm/lib/Target/X86/X86TargetTransformInfo.cpp
  llvm/lib/Target/X86/X86TargetTransformInfo.h
  llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
  llvm/test/Transforms/LoopVectorize/X86/reduction-small-trip-count.ll

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