[PATCH] unbreak attribute((optimize(...))) on m68k (PR47908)

[Mikael Pettersson]

On m68k-linux, gcc ICEs on any occurrence of attribute((optimize(...)))
ever since gcc-4.4.  Default optimization flags enable scheduling, which
the backend doesn't support for non-ColdFire targets.  The backend disables
scheduling for non-ColdFire targets when processing command-line options,
but fails to do so for the attribute optimize case, causing the ICE.

The fix for 4.6/4.7 is to hook TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE and
disable scheduling for non-ColdFire CPUs.

Tested on 4.6/4.7, no regressions but several test cases (see PR47908)
that previosuly failed now succeed.

Ok for trunk and 4.6?

(4.5 and 4.4 need a slightly different fix which I can provide if needed.)

/Mikael


gcc/

2011-07-28  Mikael Pettersson  <mi...@it.uu.se>

        PR target/47908
        * config/m68k/m68k.c (m68k_override_options_after_change): New function.
        Disable instruction scheduling for non-ColdFire targets.
        (TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE): Define.

--- gcc-4.7-20110716/gcc/config/m68k/m68k.c.~1~ 2011-06-16 15:45:47.000000000 
+0200
+++ gcc-4.7-20110716/gcc/config/m68k/m68k.c     2011-07-28 11:26:57.000000000 
+0200
@@ -136,6 +136,7 @@ static bool m68k_can_eliminate (const in
 static void m68k_conditional_register_usage (void);
 static bool m68k_legitimate_address_p (enum machine_mode, rtx, bool);
 static void m68k_option_override (void);
+static void m68k_override_options_after_change (void);
 static rtx find_addr_reg (rtx);
 static const char *singlemove_string (rtx *);
 static void m68k_output_mi_thunk (FILE *, tree, HOST_WIDE_INT,
@@ -235,6 +236,9 @@ static bool m68k_cannot_force_const_mem 
 #undef TARGET_OPTION_OVERRIDE
 #define TARGET_OPTION_OVERRIDE m68k_option_override
 
+#undef TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE
+#define TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE m68k_override_options_after_change
+
 #undef TARGET_RTX_COSTS
 #define TARGET_RTX_COSTS m68k_rtx_costs
 
@@ -634,6 +638,17 @@ m68k_option_override (void)
     }
 }
 
+static void
+m68k_override_options_after_change (void)
+{
+  if (m68k_sched_cpu == CPU_UNKNOWN)
+    {
+      flag_schedule_insns = 0;
+      flag_schedule_insns_after_reload = 0;
+      flag_modulo_sched = 0;
+    }
+}
+
 /* Generate a macro of the form __mPREFIX_cpu_NAME, where PREFIX is the
    given argument and NAME is the argument passed to -mcpu.  Return NULL
    if -mcpu was not passed.  */