[PATCH] D57779: [SLP] Add support for throttling.

Thu Sep 19 12:45:10 PDT 2019

dtemirbulatov marked an inline comment as done.
dtemirbulatov added inline comments.

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Comment at: lib/Transforms/Vectorize/SLPVectorizer.cpp:645
+  /// Save seed instructions to try partially vectorize later.
+  void recordSeeds(ArrayRef<Value *> Ops);
+
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vporpo wrote:
> dtemirbulatov wrote:
> > vporpo wrote:
> > > Why are we collecting the seeds specifically for partial vectorization? Is this really needed? Why don't you just call tryPartialVectorization(Seeds) within vectorizeStorChain() etc. ?
> > Ok, Imagine that we could do partial vectorization with vector size 4 for 30% of the tree, but for the same tree, we could have full vectorization with vector size 2. I think that it would be serious regression if we could do it with just 30%. Or for example, for the same tree, we could do reduction later for the whole tree.
> Yes, but this problem is not specific to throttling. As it is now, SLP will greedily accept 4-wide vectorization if profitable, without comparing it against 2x 2-wide. I think this problem should be addressed separately.
Let's change that behavior separately or this change grows even further. BTW, I measured the SLP run-time change on SPEC2k6 compilation and it is about ~10% on average.

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  https://reviews.llvm.org/D57779/new/

https://reviews.llvm.org/D57779