PR9218: SimplifyDemandedVectorElts can return a non-null value that is not

the instruction passed in.  Make sure to account for this correctly, instead
of looping infinitely.

llvm-svn: 126058

1 files changed, 7 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
index 4aa1328f134..5caa12dfdfa 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -426,8 +426,11 @@ Instruction *InstCombiner::visitInsertElementInst(InsertElementInst &IE) {
   unsigned VWidth = cast<VectorType>(VecOp->getType())->getNumElements();
   APInt UndefElts(VWidth, 0);
   APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
-  if (SimplifyDemandedVectorElts(&IE, AllOnesEltMask, UndefElts))
+  if (Value *V = SimplifyDemandedVectorElts(&IE, AllOnesEltMask, UndefElts)) {
+    if (V != &IE)
+      return ReplaceInstUsesWith(IE, V);
     return &IE;
+  }
 
   return 0;
 }
@@ -451,7 +454,9 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
 
   APInt UndefElts(VWidth, 0);
   APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
-  if (SimplifyDemandedVectorElts(&SVI, AllOnesEltMask, UndefElts)) {
+  if (Value *V = SimplifyDemandedVectorElts(&SVI, AllOnesEltMask, UndefElts)) {
+    if (V != &SVI)
+      return ReplaceInstUsesWith(SVI, V);
     LHS = SVI.getOperand(0);
     RHS = SVI.getOperand(1);
     MadeChange = true;