[cherrypick][LV] Vectorize Epilogues for loops with small VF but high IC #9666
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…incoming values (llvm#113915) This patch aims to strengthen collection of loop guards by processing PHI nodes with multiple incoming values as follows: collect guards for all incoming values/blocks and try to merge them into a single one for the PHI node. The goal is to determine tighter bounds on the trip counts of scalar tail loops after vectorization, helping to avoid unnecessary transforms. In particular we'd like to avoid vectorizing scalar tails of hand-vectorized loops, for example in [Transforms/PhaseOrdering/X86/pr38280.ll](https://github.com/llvm/llvm-project/blob/231e03ba7e82896847dbc27d457dbb208f04699c/llvm/test/Transforms/PhaseOrdering/X86/pr38280.ll), discovered via llvm#108190 Compile-time impact: https://llvm-compile-time-tracker.com/compare.php?from=a55248789ed3f653740e0723d016203b9d585f26&to=500e4c46e79f60b93b11a752698c520e345948e3&stat=instructions:u PR: llvm#113915 (cherry picked from commit 7c8e05a)
Address post-commit comments for llvm#113915. (cherry picked from commit feb9b37)
…8190) - Consider MainLoopVF * IC when determining whether Epilogue Vectorization is profitable - Allow the same VF for the Epilogue as for the main loop - Use an upper bound for the trip count of the Epilogue when choosing the Epilogue VF PR: llvm#108190 --------- Co-authored-by: Florian Hahn <[email protected]> (cherry picked from commit a8538b9)
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@swift-ci please test |
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@swift-ci please test |
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Cherry pick epilogue vectorization improvements from llvm#108190. Also needs llvm#113915 as a supporting change.