================
@@ -11012,6 +11012,50 @@ SDValue ReconstructShuffleWithRuntimeMask(SDValue Op,
SelectionDAG &DAG) {
MaskSourceVec);
}
+// Check if Op is a BUILD_VECTOR with 2 extracts and a load that is cheaper to
+// insert into a vector and use a shuffle. This improves lowering for loads of
+// <3 x i8>.
+static SDValue shuffleWithSingleLoad(SDValue Op, SelectionDAG &DAG) {
+ if (Op.getNumOperands() != 4 || Op.getValueType() != MVT::v4i16)
+ return SDValue();
+
+ SDValue V0 = Op.getOperand(0);
+ SDValue V1 = Op.getOperand(1);
+ SDValue V2 = Op.getOperand(2);
+ SDValue V3 = Op.getOperand(3);
+ if (V0.getOpcode() != ISD::EXTRACT_VECTOR_ELT ||
+ V1.getOpcode() != ISD::EXTRACT_VECTOR_ELT ||
+ V2.getOpcode() != ISD::LOAD ||
+ !(V3.isUndef() || V3.getOpcode() == ISD::EXTRACT_VECTOR_ELT))
+ return SDValue();
+
+ if (V0.getOperand(0) != V1.getOperand(0) ||
+ V0.getConstantOperandVal(1) != 0 || V1.getConstantOperandVal(1) != 1 ||
+ !(V3.isUndef() || V3.getConstantOperandVal(1) == 3))
----------------
TNorthover wrote:
We're not checking `V3.getOperand(0)` anywhere.
https://github.com/llvm/llvm-project/pull/78632
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