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-rw-r--r--llvm/lib/Target/X86/X86ISelLowering.cpp32
1 files changed, 25 insertions, 7 deletions
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index ba443dcbea9..72a91241d8d 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -27386,22 +27386,40 @@ 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 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,
TargetLowering::DAGCombinerInfo &DCI) {
+ if (!ISD::isBuildVectorOfConstantSDNodes(ML->getMask().getNode()))
+ return SDValue();
+
+ SDLoc DL(ML);
+ EVT VT = ML->getValueType(0);
+
+ // If we are loading the first and last elements of a vector, it is safe and
+ // always faster to load the whole vector. Replace the masked load with a
+ // vector load and select.
+ unsigned NumElts = VT.getVectorNumElements();
+ BuildVectorSDNode *MaskBV = cast<BuildVectorSDNode>(ML->getMask());
+ bool LoadFirstElt = !isNullConstant(MaskBV->getOperand(0));
+ bool LoadLastElt = !isNullConstant(MaskBV->getOperand(NumElts - 1));
+ if (LoadFirstElt && LoadLastElt) {
+ SDValue VecLd = DAG.getLoad(VT, DL, ML->getChain(), ML->getBasePtr(),
+ ML->getMemOperand());
+ SDValue Blend = DAG.getSelect(DL, VT, ML->getMask(), VecLd, ML->getSrc0());
+ return DCI.CombineTo(ML, Blend, VecLd.getValue(1), true);
+ }
+
+ // 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 select instruction
+ // (for example, vblendvps -> vblendps).
+
// Don't try this if the pass-through operand is already undefined. That would
// cause an infinite loop because that's what we're about to create.
- if (!ISD::isBuildVectorOfConstantSDNodes(ML->getMask().getNode()) ||
- ML->getSrc0().getOpcode() == ISD::UNDEF)
+ if (ML->getSrc0().isUndef())
return SDValue();
// 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(),
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