8032634: Add #ifdef PPC64 around OrderAccess operations on _thread_state.

Reviewed-by: dholmes, kvn

src/share/vm/runtime/thread.hpp

@@ -1044,6 +1044,10 @@ class JavaThread: public Thread {
   address last_Java_pc(void)                     { return _anchor.last_Java_pc(); }
 
   // Safepoint support
+#ifndef PPC64
+  JavaThreadState thread_state() const           { return _thread_state; }
+  void set_thread_state(JavaThreadState s)       { _thread_state = s;    }
+#else
   // Use membars when accessing volatile _thread_state. See
   // Threads::create_vm() for size checks.
   JavaThreadState thread_state() const           {
@@ -1052,6 +1056,7 @@ class JavaThread: public Thread {
   void set_thread_state(JavaThreadState s)       {
     OrderAccess::release_store((volatile jint*)&_thread_state, (jint)s);
   }
+#endif
   ThreadSafepointState *safepoint_state() const  { return _safepoint_state; }
   void set_safepoint_state(ThreadSafepointState *state) { _safepoint_state = state; }
   bool is_at_poll_safepoint()                    { return _safepoint_state->is_at_poll_safepoint(); }