Index: lib/IR/ConstantFold.cpp
===================================================================
--- lib/IR/ConstantFold.cpp
+++ lib/IR/ConstantFold.cpp
@@ -2097,15 +2097,19 @@
       // Subsequent evaluation would get confused and produce erroneous results.
       //
       // The following prohibits such a GEP from being formed by checking to see
-      // if the index is in-range with respect to an array or vector.
+      // if the index is in-range with respect to an array.
+      // TODO: This code may be extended to handle vectors as well.
       bool PerformFold = false;
       if (Idx0->isNullValue())
         PerformFold = true;
       else if (LastI.isSequential())
         if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx0))
-          PerformFold =
-              !LastI.isBoundedSequential() ||
-              isIndexInRangeOfArrayType(LastI.getSequentialNumElements(), CI);
+          PerformFold = (!LastI.isBoundedSequential() ||
+                         isIndexInRangeOfArrayType(
+                             LastI.getSequentialNumElements(), CI)) &&
+                        !CE->getOperand(CE->getNumOperands() - 1)
+                             ->getType()
+                             ->isVectorTy();
 
       if (PerformFold) {
         SmallVector<Value*, 16> NewIndices;
Index: test/Transforms/InstSimplify/pr33957.ll
===================================================================
--- /dev/null
+++ test/Transforms/InstSimplify/pr33957.ll
@@ -0,0 +1,29 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -loop-unroll -S %s | FileCheck %s
+
+%struct.bar = type { i32 }
+
+@global = external constant [78 x %struct.bar], align 4
+
+define void @patatino(i32 %x) {
+; CHECK-LABEL: @patatino(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    br i1 true, label [[BB1_PREHEADER:%.*]], label [[BB3:%.*]]
+; CHECK:       bb1.preheader:
+; CHECK-NEXT:    br label [[BB1:%.*]]
+; CHECK:       bb1:
+; CHECK-NEXT:    br label [[BB3]]
+; CHECK:       bb3:
+; CHECK-NEXT:    ret void
+;
+bb:
+  br i1 true, label %bb1, label %bb3
+
+bb1:
+  %tmp = getelementptr inbounds [78 x %struct.bar], [78 x %struct.bar]* @global, i32 0, <4 x i32> undef
+  %tmp2 = getelementptr inbounds %struct.bar, <4 x %struct.bar*> %tmp, i32 1
+  br i1 true, label %bb3, label %bb1
+
+bb3:
+  ret void
+}