1 files changed, 10 insertions, 6 deletions
diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index 93fb1143e50..c94429f5521 100644
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -3838,12 +3838,13 @@ Value *llvm::SimplifyInsertElementInst(Value *Vec, Value *Val, Value *Idx,
   // Fold into undef if index is out of bounds.
   if (auto *CI = dyn_cast<ConstantInt>(Idx)) {
     uint64_t NumElements = cast<VectorType>(Vec->getType())->getNumElements();
-
     if (CI->uge(NumElements))
       return UndefValue::get(Vec->getType());
   }
 
-  // TODO: We should also fold if index is iteslf an undef.
+  // If index is undef, it might be out of bounds (see above case)
+  if (isa<UndefValue>(Idx))
+    return UndefValue::get(Vec->getType());
 
   return nullptr;
 }
@@ -3896,10 +3897,13 @@ static Value *SimplifyExtractElementInst(Value *Vec, Value *Idx, const SimplifyQ
 
   // If extracting a specified index from the vector, see if we can recursively
   // find a previously computed scalar that was inserted into the vector.
-  if (auto *IdxC = dyn_cast<ConstantInt>(Idx))
-    if (IdxC->getValue().ule(Vec->getType()->getVectorNumElements()))
-      if (Value *Elt = findScalarElement(Vec, IdxC->getZExtValue()))
-        return Elt;
+  if (auto *IdxC = dyn_cast<ConstantInt>(Idx)) {
+    if (IdxC->getValue().uge(Vec->getType()->getVectorNumElements()))
+      // definitely out of bounds, thus undefined result
+      return UndefValue::get(Vec->getType()->getVectorElementType());
+    if (Value *Elt = findScalarElement(Vec, IdxC->getZExtValue()))
+      return Elt;
+  }
 
   // An undef extract index can be arbitrarily chosen to be an out-of-range
   // index value, which would result in the instruction being undef.