[PATCH] D124293: [SLP][NFC] Pre-commit test showing deficiency in current roots selection algorithm

[Valeriy Dmitriev via Phabricator via llvm-commits]

vdmitrie added inline comments.


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Comment at: llvm/test/Transforms/SLPVectorizer/X86/vectorize-pair-path.ll:48
+  %i03 = fmul fast double undef, %i02
+  %i04 = fsub fast double %i03, undef
+  %i05 = fmul fast double %i04, 4.0
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ABataev wrote:
> RKSimon wrote:
> > Why are there undef float-ops? Is this the only way to expose the issue? If you run this through opt -O3 all you get is a posion result.
> It is ok for SLP to have some undefs unless you do not use instcombine. You can treat undef here as a specific op kind, different from others. Just to reduce the size of the test.
Yeah, this shouldn't go through instcombine. There were even more undefs after bugpoint reduced the original case so I had to step beck a bit and replaced some with FP constants to make tracing SLP vectorizer behavior easier. 



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https://reviews.llvm.org/D124293