[SPARC] Enable REE at -O2 by default in 64-bit mode

[Eric Botcazou]

Tests showed that it helps to eliminates redundant 32-to-64-bit extensions.

Tested on SPARC/Solaris, applied on the mainline.


2016-11-24  Eric Botcazou  <ebotca...@adacore.com>

        * common/config/sparc/sparc-common.c (option_optimization_table):
        Enable REE at -O2 and higher.
        * config/sparc/sparc.c (sparc_option_override): Disable it by default
        in 32-bit mode.

-- 
Eric Botcazou
Index: common/config/sparc/sparc-common.c
===================================================================
--- common/config/sparc/sparc-common.c	(revision 242632)
+++ common/config/sparc/sparc-common.c	(working copy)
@@ -28,6 +28,8 @@ along with GCC; see the file COPYING3.
 static const struct default_options sparc_option_optimization_table[] =
   {
     { OPT_LEVELS_1_PLUS, OPT_fomit_frame_pointer, NULL, 1 },
+    /* Enable redundant extension instructions removal at -O2 and higher.  */
+    { OPT_LEVELS_2_PLUS, OPT_free, NULL, 1 },
     { OPT_LEVELS_NONE, 0, NULL, 0 }
   };
 
Index: config/sparc/sparc.c
===================================================================
--- config/sparc/sparc.c	(revision 242632)
+++ config/sparc/sparc.c	(working copy)
@@ -1713,6 +1713,11 @@ sparc_option_override (void)
      pessimizes for double floating-point registers.  */
   if (!global_options_set.x_flag_ira_share_save_slots)
     flag_ira_share_save_slots = 0;
+
+  /* Only enable REE by default in 64-bit mode where it helps to eliminate
+     redundant 32-to-64-bit extensions.  */
+  if (!global_options_set.x_flag_ree && TARGET_ARCH32)
+    flag_ree = 0;
 }
 
 /* Miscellaneous utilities.  */