[DAGCombiner] after simplifying demanded elements of vector operand of extract, revisit the extract

Differential Revision: https://reviews.llvm.org/D55655

llvm-svn: 349051

1 files changed, 6 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 7768d12c75c..b364b1baea7 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -15698,8 +15698,13 @@ SDValue DAGCombiner::visitEXTRACT_VECTOR_ELT(SDNode *N) {
       if (CstElt->getAPIntValue().ult(VT.getVectorNumElements()))
         DemandedElts.setBit(CstElt->getZExtValue());
     }
-    if (SimplifyDemandedVectorElts(InVec, DemandedElts, true))
+    if (SimplifyDemandedVectorElts(InVec, DemandedElts, true)) {
+      // We simplified the operands of this extract element, but if this extract
+      // is still alive, visit it again to ensure that it is folded properly.
+      if (!N->use_empty())
+        AddToWorklist(N);
       return SDValue(N, 0);
+    }
   }
 
   bool BCNumEltsChanged = false;