1 files changed, 23 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 0b28fbb12a3..dc2348f6cb8 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -609,6 +609,29 @@ SDValue TargetLowering::SimplifyMultipleUseDemandedBits(
       return Op.getOperand(1);
     break;
   }
+  case ISD::VECTOR_SHUFFLE: {
+    ArrayRef<int> ShuffleMask = cast<ShuffleVectorSDNode>(Op)->getMask();
+
+    // If all the demanded elts are from one operand and are inline,
+    // then we can use the operand directly.
+    bool AllUndef = true, IdentityLHS = true, IdentityRHS = true;
+    for (unsigned i = 0, NumElts = ShuffleMask.size(); i != NumElts; ++i) {
+      int M = ShuffleMask[i];
+      if (M < 0 || !DemandedElts[i])
+        continue;
+      AllUndef = false;
+      IdentityLHS &= (M == (int)i);
+      IdentityRHS &= ((M - NumElts) == i);
+    }
+
+    if (AllUndef)
+      return DAG.getUNDEF(Op.getValueType());
+    if (IdentityLHS)
+      return Op.getOperand(0);
+    if (IdentityRHS)
+      return Op.getOperand(1);
+    break;
+  }
   default:
     if (Op.getOpcode() >= ISD::BUILTIN_OP_END)
       if (SDValue V = SimplifyMultipleUseDemandedBitsForTargetNode(