[PATCH] D95452: [LoopVectorize] use IR fast-math-flags exclusively (not function attributes)

[Sanjay Patel via Phabricator via llvm-commits]

spatel created this revision.
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I am trying to untangle the fast-math-flags propagation logic in the vectorizers (see a6f022127 <https://reviews.llvm.org/rGa6f02212764a76935ec5fb704fe86a1a76f65745> for SLP).

The loop vectorizer has a mix of checking FP function attributes, IR-level FMF, and just wrong assumptions.

I am trying to avoid regressions while fixing this, and I think the IR-level logic is good enough for that, but it's hard to say for sure. This would be the 1st step in the clean-up.

The existing test that I changed to include 'fast' actually shows a miscompile: the function only had the equivalent of `nnan`, but we created new instructions that had `fast` (all FMF set). This is similar to the example in https://llvm.org/PR35538


https://reviews.llvm.org/D95452

Files:
  llvm/include/llvm/Transforms/Vectorize/LoopVectorizationLegality.h
  llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
  llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
  llvm/lib/Transforms/Vectorize/VPlan.h
  llvm/test/Transforms/LoopVectorize/X86/float-induction-x86.ll
  llvm/unittests/Transforms/Vectorize/VPlanTest.cpp

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