Propagate zest through logical shift.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@91378 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 0 deletions

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 027348c0f6..52b7ed5f15 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3278,6 +3278,16 @@ SDValue DAGCombiner::visitZERO_EXTEND(SDNode *N) {
     if (SCC.getNode()) return SCC;
   }
 
+  // (zext (shl (zext x), y)) -> (shl (zext x), (zext y))
+  if ((N0.getOpcode() == ISD::SHL || N0.getOpcode() == ISD::SRL) &&
+      N0.getOperand(0).getOpcode() == ISD::ZERO_EXTEND &&
+      N0.hasOneUse()) {
+    DebugLoc dl = N->getDebugLoc();
+    return DAG.getNode(N0.getOpcode(), dl, VT,
+                       DAG.getNode(ISD::ZERO_EXTEND, dl, VT, N0.getOperand(0)),
+                       DAG.getNode(ISD::ZERO_EXTEND, dl, VT, N0.getOperand(1)));
+  }
+
   return SDValue();
 }