Fix test case.

r230921 broke backend-optimization-failure.cpp: after
r230921, LLVM no longer emits an expression to compute 'Length - 1'
and this perturbs LoopSimplify enough to emit the warning on line 10
instead of line 9.  This is a review request to fix the test case once
I re-land r230921.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@231020 91177308-0d34-0410-b5e6-96231b3b80d8

test/Misc/backend-optimization-failure.cpp

@@ -6,8 +6,8 @@
 
 void test_switch(int *A, int *B, int Length) {
 #pragma clang loop vectorize(enable) unroll(disable)
-  /* expected-warning {{loop not vectorized: failed explicitly specified loop vectorization}} */ for (int i = 0; i < Length; i++) {
-    switch (A[i]) {
+  for (int i = 0; i < Length; i++) {
+/* expected-warning {{loop not vectorized: failed explicitly specified loop vectorization}} */ switch (A[i]) {
     case 0:
       B[i] = 1;
       break;