[llvm] [PowerPC] Replace vspltisw+vadduwm instructions with xxleqv+vsubuwm for adding the vector {1, 1, 1, 1} (PR #160882)

[via llvm-commits]

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@@ -19208,13 +19208,54 @@ static SDValue combineADDToMAT_PCREL_ADDR(SDNode *N, SelectionDAG &DAG,
   return MatPCRel;
 }
 
+static SDValue combineADDToSUB(SDNode *N, SelectionDAG &DAG,
+                               const PPCSubtarget &Subtarget) {
+  EVT VT = N->getValueType(0);
+
+  // Handle v2i64, v4i32, v8i16 and v16i8 types
+  if (!(VT == MVT::v8i16 || VT == MVT::v16i8 || VT == MVT::v4i32 ||
+        VT == MVT::v2i64))
+    return SDValue();
+
+  SDValue LHS = N->getOperand(0);
+  SDValue RHS = N->getOperand(1);
+
+  // Check if RHS is BUILD_VECTOR
+  // To satisfy commutative property a+b = b+a
+  if (RHS.getOpcode() != ISD::BUILD_VECTOR)
+    std::swap(LHS, RHS);
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Himadhith wrote:

Done.

https://github.com/llvm/llvm-project/pull/160882