[PATCH] D87772: [SLP] sort candidates to increase chance of optimal compare reduction

[Sanjay Patel via Phabricator via llvm-commits]

spatel created this revision.
spatel added reviewers: dtemirbulatov, ABataev, RKSimon, lebedev.ri.
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This is one (small) part of improving PR41312:
https://llvm.org/PR41312

As shown there and in the smaller tests here, if we have some member of the reduction values that does not match the others, we want to push it to the end (bring the matching members forward and together).

In the examples here, we have 5 candidates for the 4 slots of the reduction. If the one "wrong" compare is grouped with the others, it prevents forming the ideal v4i1 compare reduction.


https://reviews.llvm.org/D87772

Files:
  llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
  llvm/test/Transforms/SLPVectorizer/X86/compare-reduce.ll

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