[libcxx] fix `>> 42` UB in <experimental/simd>

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@338325 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/std/experimental/simd/simd.access/default.pass.cpp b/test/std/experimental/simd/simd.access/default.pass.cpp
index 697035b..6ce32ca 100644
--- a/test/std/experimental/simd/simd.access/default.pass.cpp
+++ b/test/std/experimental/simd/simd.access/default.pass.cpp
@@ -161,7 +161,7 @@
     }
     {
       auto c = a;
-      (void)(a[0] + (c[0] >>= a[0]));
+      (void)(a[0] + (c[0] >>= b[0]));
     }
     {
       auto c = a;