[PATCH] D124867: [SLP][NFC] Pre-commit test showing horizontal reduction preventing FMA

[Bill Schmidt via Phabricator via llvm-commits]

wjschmidt added inline comments.


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Comment at: llvm/test/Transforms/SLPVectorizer/X86/slp-reduc-fma-loss.ll:40
+  %x.616 = fadd fast double %x.615, %x.597
+  br i1 undef, label %exit, label %loop
+
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fhahn wrote:
> wjschmidt wrote:
> > vporpo wrote:
> > > The test should still work without the loop
> > Sadly, it does not.  If I remove the loop branches and the phi and replace the phi uses with undef, the vectorizer no longer finds the horizontal reduction profitable.
> Please avoid using undef. In most cases, it prevents automatic verification or at least makes it more difficult. 
OK, will replace all undefs with constants.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D124867/new/

https://reviews.llvm.org/D124867