[InstSimplify] Check for in range extraction index before calling APInt::getZExtValue()

Reduced from oss-fuzz #4768 test case

llvm-svn: 321454

2 files changed, 16 insertions, 2 deletions

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 3ce1281743c..fac6a917dc9 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -3897,8 +3897,9 @@ 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 (Value *Elt = findScalarElement(Vec, IdxC->getZExtValue()))
-      return Elt;
+    if (IdxC->getValue().ule(Vec->getType()->getVectorNumElements()))
+      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.
diff --git a/llvm/test/Transforms/InstSimplify/extract-element.ll b/llvm/test/Transforms/InstSimplify/extract-element.ll
new file mode 100644
index 00000000000..8ee75a603cd
--- /dev/null
+++ b/llvm/test/Transforms/InstSimplify/extract-element.ll
@@ -0,0 +1,13 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -instsimplify -S | FileCheck %s
+
+; Weird Types
+
+define i129 @vec_extract_negidx(<3 x i129> %a) {
+; CHECK-LABEL: @vec_extract_negidx(
+; CHECK-NEXT:    [[E1:%.*]] = extractelement <3 x i129> [[A:%.*]], i129 -1
+; CHECK-NEXT:    ret i129 [[E1]]
+;
+  %E1 = extractelement <3 x i129> %a, i129 -1
+  ret i129 %E1
+}