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[x86] don't use a shuffle when a vselect will do; NFCI

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Looking at the IR definition of a masked load made me realize
there was no reason to use a shuffle here, so we don't need
to convert the format of the mask at all.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@263167 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjay Patel 2016-03-10 22:35:33 +00:00
parent 578acc5b53
commit 444e7f9783
1 changed files with 5 additions and 16 deletions
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21
lib/Target/X86/X86ISelLowering.cpp
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@ -27336,8 +27336,8 @@ reduceMaskedLoadToScalarLoad(MaskedLoadSDNode *ML, SelectionDAG &DAG,
return DCI.CombineTo(ML, Insert, Load.getValue(1), true);
}
/// Convert a masked load with a constant mask into a masked load and a shuffle.
/// This allows the blend operation to use a faster kind of shuffle instruction
/// Convert a masked load with a constant mask into a masked load and a select.
/// This allows the select operation to use a faster kind of shuffle instruction
/// (for example, vblendvps -> vblendps).
static SDValue
combineMaskedLoadConstantMask(MaskedLoadSDNode *ML, SelectionDAG &DAG,
@ -27348,26 +27348,15 @@ combineMaskedLoadConstantMask(MaskedLoadSDNode *ML, SelectionDAG &DAG,
ML->getSrc0().getOpcode() == ISD::UNDEF)
return SDValue();
// Convert the masked load's mask into a blend mask for a vector shuffle node.
EVT VT = ML->getValueType(0);
unsigned NumElts = VT.getVectorNumElements();
BuildVectorSDNode *MaskBV = cast<BuildVectorSDNode>(ML->getMask());
SmallVector<int, 16> ShufMask(NumElts, SM_SentinelUndef);
for (unsigned i = 0; i < NumElts; ++i) {
// If this mask bit of the masked load is false, the pass-through vector
// (Src0) element will be selected for that vector lane.
if (MaskBV->getOperand(i).getOpcode() != ISD::UNDEF)
ShufMask[i] = isNullConstant(MaskBV->getOperand(i)) ? i + NumElts : i;
}
// The new masked load has an undef pass-through operand. The shuffle uses the
// The new masked load has an undef pass-through operand. The select uses the
// original pass-through operand.
SDLoc DL(ML);
EVT VT = ML->getValueType(0);
SDValue NewML = DAG.getMaskedLoad(VT, DL, ML->getChain(), ML->getBasePtr(),
ML->getMask(), DAG.getUNDEF(VT),
ML->getMemoryVT(), ML->getMemOperand(),
ML->getExtensionType());
SDValue Blend = DAG.getVectorShuffle(VT, DL, NewML, ML->getSrc0(), ShufMask);
SDValue Blend = DAG.getSelect(DL, VT, ML->getMask(), NewML, ML->getSrc0());
return DCI.CombineTo(ML, Blend, NewML.getValue(1), true);
}