[PATCH] D153697: [LV] Freeze start value for select-reductions.
Florian Hahn via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Sat Jun 24 03:46:07 PDT 2023
fhahn created this revision.
fhahn added reviewers: Ayal, gilr, rengolin.
Herald added subscribers: artagnon, StephenFan, rogfer01, hiraditya.
Herald added a project: All.
fhahn requested review of this revision.
Herald added a subscriber: vkmr.
Herald added a project: LLVM.
When creating select-reductions, we are introducing multiple new uses of
the reduction start value. If the start value may be undef or poison,
then differnet uses (e.g in the final select or vector compares) can
evaluate to different values, leading to incorrect results.
To avoid this, freeze the start value in the preheader by introducing a
new Freeze VPInstruction.
Depends on D153696 <https://reviews.llvm.org/D153696>.
Fixes #62565.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D153697
Files:
llvm/include/llvm/Transforms/Utils/LoopUtils.h
llvm/lib/Transforms/Utils/LoopUtils.cpp
llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
llvm/test/Transforms/LoopVectorize/AArch64/sve-select-cmp.ll
llvm/test/Transforms/LoopVectorize/select-cmp.ll
llvm/test/Transforms/LoopVectorize/select-reduction-start-value-may-be-undef-or-poison.ll
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