[PATCH] D26905: [SLP] Vectorize loads of consecutive memory accesses, accessed in non-consecutive (jumbled) way.

[Matthew Simpson via Phabricator via llvm-commits]

mssimpso added inline comments.


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Comment at: lib/Transforms/Vectorize/SLPVectorizer.cpp:2565
+      // must be followed by a 'shuffle' with the required jumbled mask.
+      if (E->NeedToShuffle && (VL.size() == E->Scalars.size())) {
+        SmallVector<Constant *, 8> Mask;
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ashahid wrote:
> mssimpso wrote:
> > ashahid wrote:
> > > mssimpso wrote:
> > > > I probably missed this, but why are we checking the sizes? Does this mean there will be cases where E->NeedToShuffle is true but we don't generate the shuffle?
> > > No, I want to ensure that resulting vector type is not differing due to the length of the vector value.
> > I don't think I fully understand this yet. Can you please make the comment more detailed. In particular, when does VL.size() not equal Scalars.size()? Is this the case when a bundle gets split up into smaller chunks? And then if this is true, what does it imply for the jumbled accesses. It looks like we will end up with a vector load still, but then when are they placed in the right order? Sorry if this should all be obvious!
> As such I don't expect VL.size() not equal to Scalars.size(), but if it is so, the compiler may throw assertion for incorrect vector types. I just wanted to avoid that. May be I am presuming it. I will check by avoiding this specific check.
Should we make the size check an assertion?


https://reviews.llvm.org/D26905