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LoadStoreVectorizer: Split even sized illegal chains properly

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Implement isLegalToVectorizeLoadChain for AMDGPU to avoid
producing private address spaces accesses that will need to be
split up later. This was doing the wrong thing in the case
where the queried chain was an even number of elements.

A possible <4 x i32> store was being split into
store <2 x i32>
store i32
store i32

rather than
store <2 x i32>
store <2 x i32>

when legal.

llvm-svn: 295933
This commit is contained in:
Matt Arsenault
2017-02-23 03:58:53 +00:00
parent c8d0c7a0e3
commit f0a88dbaab
5 changed files with 227 additions and 9 deletions
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9
llvm/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp
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@@ -432,9 +432,12 @@ Vectorizer::splitOddVectorElts(ArrayRef<Instruction *> Chain,
unsigned ElementSizeBytes = ElementSizeBits / 8;
unsigned SizeBytes = ElementSizeBytes * Chain.size();
unsigned NumLeft = (SizeBytes - (SizeBytes % 4)) / ElementSizeBytes;
if (NumLeft == Chain.size())
--NumLeft;
else if (NumLeft == 0)
if (NumLeft == Chain.size()) {
if ((NumLeft & 1) == 0)
NumLeft /= 2; // Split even in half
else
--NumLeft; // Split off last element
} else if (NumLeft == 0)
NumLeft = 1;
return std::make_pair(Chain.slice(0, NumLeft), Chain.slice(NumLeft));
}