1 files changed, 9 insertions, 0 deletions
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 14e54f0e4e2..a7560b70049 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -39689,6 +39689,15 @@ static SDValue combinePMULDQ(SDNode *N, SelectionDAG &DAG,
   SDValue LHS = N->getOperand(0);
   SDValue RHS = N->getOperand(1);
 
+  // Canonicalize constant to RHS.
+  if (DAG.isConstantIntBuildVectorOrConstantInt(LHS) &&
+      !DAG.isConstantIntBuildVectorOrConstantInt(RHS))
+    return DAG.getNode(N->getOpcode(), SDLoc(N), N->getValueType(0), RHS, LHS);
+
+  // Multiply by zero.
+  if (ISD::isBuildVectorAllZeros(RHS.getNode()))
+    return RHS;
+
   const TargetLowering &TLI = DAG.getTargetLoweringInfo();
   TargetLowering::TargetLoweringOpt TLO(DAG, !DCI.isBeforeLegalize(),
                                         !DCI.isBeforeLegalizeOps());