6948602: Disable use of SSE4.2 in String.indexOf intrinsic until 6942326 is fixed

Summary: Disable the use of pcmpestri until it can be guaranteed that the load doesn't cross in to the uncommited space. See 6942326.
Reviewed-by: never, kvn

src/share/vm/opto/library_call.cpp

@@ -1175,7 +1175,9 @@ bool LibraryCallKit::inline_string_indexOf() {
   Node *receiver = pop();
 
   Node* result;
-  if (Matcher::has_match_rule(Op_StrIndexOf) &&
+  // Disable the use of pcmpestri until it can be guaranteed that
+  // the load doesn't cross into the uncommited space.
+  if (false && Matcher::has_match_rule(Op_StrIndexOf) &&
       UseSSE42Intrinsics) {
     // Generate SSE4.2 version of indexOf
     // We currently only have match rules that use SSE4.2