s390.c (override_options): Adopt prefetching at -O3 to handle…

s390.c (override_options): Adopt prefetching at -O3 to handle flag_prefetch_loop_arrays as a tristate.

2010-07-02  Christian Borntraeger  <borntraeger@de.ibm.com>
 
	* config/s390/s390.c (override_options): Adopt prefetching
	at -O3 to handle flag_prefetch_loop_arrays as a tristate.

From-SVN: r161709

gcc/ChangeLog

+2010-07-02  Christian Borntraeger  <borntraeger@de.ibm.com>
+
+	* config/s390/s390.c (override_options): Adopt prefetching
+	at -O3 to handle flag_prefetch_loop_arrays as a tristate.
+
 2010-07-02  Jan Hubicka  <jh@suse.cz>
 
 	* df-problems.c (df_kill_notes): Do not collect dead  notes.

gcc/config/s390/s390.c

@@ -1675,8 +1675,9 @@ override_options (void)
     set_param_value ("simultaneous-prefetches", 6);
 
   /* This cannot reside in optimization_options since HAVE_prefetch
-     requires the arch flags to be evaluated already.  */
-  if (HAVE_prefetch && optimize >= 3)
+     requires the arch flags to be evaluated already.  Since prefetching
+     is beneficial on s390, we enable it if available.  */
+  if (flag_prefetch_loop_arrays < 0 && HAVE_prefetch && optimize >= 3)
     flag_prefetch_loop_arrays = 1;
 }