A patch making GCC with -O0 to run combiner and RA.  After applying
the patch all other otimization levels -On (n >= 1) still work as the
same before.

Index: combine.c
===================================================================
--- combine.c	(revision 254608)
+++ combine.c	(working copy)
@@ -14841,7 +14841,7 @@
   {}
 
   /* opt_pass methods: */
-  virtual bool gate (function *) { return (optimize > 0); }
+  virtual bool gate (function *) { return (1||optimize > 0); }
   virtual unsigned int execute (function *)
     {
       return rest_of_handle_combine ();
Index: df-core.c
===================================================================
--- df-core.c	(revision 254608)
+++ df-core.c	(working copy)
@@ -741,7 +741,7 @@
   {}
 
   /* opt_pass methods: */
-  virtual bool gate (function *) { return optimize > 0; }
+  virtual bool gate (function *) { return 1||optimize > 0; }
   virtual unsigned int execute (function *)
     {
       return rest_of_handle_df_initialize ();
@@ -781,7 +781,7 @@
   {}
 
   /* opt_pass methods: */
-  virtual bool gate (function *) { return optimize == 0; }
+  virtual bool gate (function *) { return 0&&optimize == 0; }
   virtual unsigned int execute (function *)
     {
       return rest_of_handle_df_initialize ();
Index: function.c
===================================================================
--- function.c	(revision 254608)
+++ function.c	(working copy)
@@ -2214,7 +2214,7 @@
   if (DECL_IGNORED_P (decl))
     return true;
 
-  if (optimize)
+  if (1||optimize)
     return true;
 
   if (!DECL_REGISTER (decl))
Index: init-regs.c
===================================================================
--- init-regs.c	(revision 254608)
+++ init-regs.c	(working copy)
@@ -50,7 +50,7 @@
   basic_block bb;
   auto_bitmap already_genned;
 
-  if (optimize == 1)
+  if (1||optimize == 1)
     {
       df_live_add_problem ();
       df_live_set_all_dirty ();
@@ -119,7 +119,7 @@
 	}
     }
 
-  if (optimize == 1)
+  if (1||optimize == 1)
     {
       if (dump_file)
 	df_dump (dump_file);
@@ -150,7 +150,7 @@
   {}
 
   /* opt_pass methods: */
-  virtual bool gate (function *) { return optimize > 0; }
+  virtual bool gate (function *) { return 1||optimize > 0; }
   virtual unsigned int execute (function *)
     {
       initialize_uninitialized_regs ();
Index: ira.c
===================================================================
--- ira.c	(revision 254608)
+++ ira.c	(working copy)
@@ -5141,7 +5141,7 @@
   /* Perform target specific PIC register initialization.  */
   targetm.init_pic_reg ();
 
-  ira_conflicts_p = optimize > 0;
+  ira_conflicts_p = 1||optimize > 0;
 
   /* If there are too many pseudos and/or basic blocks (e.g. 10K
      pseudos and 10K blocks or 100K pseudos and 1K blocks), we will