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[x86] Teach the vector shuffle yet another step of canonicalization.

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No functionality changed yet, but this will prevent subsequent patches
from having to handle permutations of various interleaved shuffle
patterns.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222614 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chandler Carruth 2014-11-22 09:18:53 +00:00
parent 8ff39c5c44
commit e915b4b7c8
1 changed files with 13 additions and 2 deletions
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15
lib/Target/X86/X86ISelLowering.cpp
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@ -10833,7 +10833,8 @@ static SDValue lowerVectorShuffle(SDValue Op, const X86Subtarget *Subtarget,
// When the number of V1 and V2 elements are the same, try to minimize the
// number of uses of V2 in the low half of the vector. When that is tied,
// ensure that the sum of indices for V1 is equal to or lower than the sum
// indices for V2.
// indices for V2. When those are equal, try to ensure that the number of odd
// indices for V1 is lower than the number of odd indices for V2.
if (NumV1Elements == NumV2Elements) {
int LowV1Elements = 0, LowV2Elements = 0;
for (int M : SVOp->getMask().slice(0, NumElements / 2))
@ -10850,8 +10851,18 @@ static SDValue lowerVectorShuffle(SDValue Op, const X86Subtarget *Subtarget,
SumV2Indices += i;
else if (SVOp->getMask()[i] >= 0)
SumV1Indices += i;
if (SumV2Indices < SumV1Indices)
if (SumV2Indices < SumV1Indices) {
return DAG.getCommutedVectorShuffle(*SVOp);
} else if (SumV2Indices == SumV1Indices) {
int NumV1OddIndices = 0, NumV2OddIndices = 0;
for (int i = 0, Size = SVOp->getMask().size(); i < Size; ++i)
if (SVOp->getMask()[i] >= NumElements)
NumV2OddIndices += i % 2;
else if (SVOp->getMask()[i] >= 0)
NumV1OddIndices += i % 2;
if (NumV2OddIndices < NumV1OddIndices)
return DAG.getCommutedVectorShuffle(*SVOp);
}
}
}