i386: Use the STC bb-reorder algorithm at -Os (PR67864)

For x86, STC still gives better results for optimise-for-size than
"simple" does.  So use STC at -Os as well.


	PR rtl-optimization/67864
	* common/config/i386/i386-common.c (ix86_option_optimization_table)
	<OPT_freorder_blocks_algorithm_>: Use REORDER_BLOCKS_ALGORITHM_STC
	at -Os and up.

From-SVN: r229937

gcc/ChangeLog

+2015-11-07  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR rtl-optimization/67864
+	* common/config/i386/i386-common.c (ix86_option_optimization_table)
+	<OPT_freorder_blocks_algorithm_>: Use REORDER_BLOCKS_ALGORITHM_STC
+	at -Os and up.
+
 2015-11-07  Richard Sandiford  <richard.sandiford@arm.com>
 
 	* trans-mem.c (is_tm_pure_call): Use gimple_call_flags for

gcc/common/config/i386/i386-common.c

@@ -997,6 +997,9 @@ static const struct default_options ix86_option_optimization_table[] =
     { OPT_LEVELS_2_PLUS, OPT_free, NULL, 1 },
     /* Enable function splitting at -O2 and higher.  */
     { OPT_LEVELS_2_PLUS, OPT_freorder_blocks_and_partition, NULL, 1 },
+    /* The STC algorithm produces the smallest code at -Os, for x86.  */
+    { OPT_LEVELS_2_PLUS, OPT_freorder_blocks_algorithm_, NULL,
+      REORDER_BLOCKS_ALGORITHM_STC },
     /* Turn off -fschedule-insns by default.  It tends to make the
        problem with not enough registers even worse.  */
     { OPT_LEVELS_ALL, OPT_fschedule_insns, NULL, 0 },