schedule-ebbs and trapping insns

["David S. Miller" <davem at redhat dot com>]

How can the init_ready_list used by sched-ebb.c legally not
take into consideration trapping instructions like the
sched-rgn.c version does?  You can't move trapping instructions
between basic blocks.

I hit this because I tried to start using sched-ebb on Sparc
and things blew up when schedule_ebbs swapped the order of
these two tests in expmed.c:extract_bit_field

        && GET_MODE_SIZE (mode1) != 0
        && byte_offset % GET_MODE_SIZE (mode1) == 0)

Such a transformation is obviously illegal and this results
in a divide by zero while building libobjc.

I guess this doesn't get hit on IA64 (which is the only current port
in the tree using schedule_ebbs) because of predication.  If that is
true then it shouldn't hurt code generated on that platform if we put
the necessary checks in.

I guess there are properties we can depend upon for extended basic
blocks that would allow the "exception free" test to be more leanient
than the one in sched-rgn.c, particularly for loads/stores.

For reference here is the patch I am using to make Sparc use
schedule_ebbs.

2002-06-26  David S. Miller  <davem@redhat.com>

	* config/sparc/sparc.h (MASK_NORMAL_SCHED2, TARGET_NORMAL_SCHED2):
	Define.
	(TARGET_SWITCHED): Add -mnormal-sched2.
	(MACHINE_DEPENDENT_REORG): Define.
	* config/sparc/sparc-protos.h (sparc_reorg): Declare.
	* config/sparc/sparc.c: Include basic-block.h, timevar.h
	(sparc_flag_schedule_insns2): New.
	(sparc_override_options): If not TARGET_NORMAL_SCHED2, propagate
	flag_schedule_insns_after_reload setting to
	sparc_flag_schedule_insn2 and then clear the former.
	(sparc_reorg): New, run schedule_ebbs pass if
	sparc_flag_schedule_insns2 is set.

--- ./config/sparc/sparc.c.~1~	Tue Jun  4 14:08:55 2002
+++ ./config/sparc/sparc.c	Wed Jun 26 21:22:03 2002
@@ -41,6 +41,8 @@ Boston, MA 02111-1307, USA.  */
 #include "recog.h"
 #include "toplev.h"
 #include "ggc.h"
+#include "basic-block.h"
+#include "timevar.h"
 #include "tm_p.h"
 #include "debug.h"
 #include "target.h"
@@ -125,6 +127,12 @@ char sparc_leaf_regs[] =
 static const char *frame_base_name;
 static int frame_base_offset;
 
+/* Determines whether we run our own second scheduling pass or not.
+   The user can choose the normal sched2 pass if he wants by specifying
+   -mnormal-sched2 on the command line.  */
+
+static int sparc_flag_schedule_insns2;
+
 static void sparc_init_modes	PARAMS ((void));
 static int save_regs		PARAMS ((FILE *, int, int, const char *,
 				       int, int, int));
@@ -435,6 +443,12 @@ sparc_override_options ()
   if (!TARGET_ARCH64)
     targetm.asm_out.unaligned_op.di = NULL;
 
+  if (!TARGET_NORMAL_SCHED2)
+    {
+      sparc_flag_schedule_insns2 = flag_schedule_insns_after_reload;
+      flag_schedule_insns_after_reload = 0;
+    }
+
   /* Do various machine dependent initializations.  */
   sparc_init_modes ();
 }
@@ -8511,6 +8525,35 @@ sparc_output_mi_thunk (file, thunk_fndec
 
   reload_completed = 0;
   no_new_pseudos = 0;
+}
+
+/* Perform machine dependent operations on the rtl chain INSNS.  */
+
+void
+sparc_reorg (insns)
+     rtx insns ATTRIBUTE_UNUSED;
+{
+  if (TARGET_NORMAL_SCHED2)
+    return;
+
+  /* We are freeing block_for_insn in the toplev to keep compatibility
+     with old MDEP_REORGS that are not CFG based.  Recompute it now.  */
+  compute_bb_for_insn ();
+
+  /* If optimizing, we'll have split before scheduling.  */
+  if (optimize == 0)
+    split_all_insns (0);
+
+  /* ??? update_life_info_in_dirty_blocks fails to terminate during
+     non-optimizing bootstrap.  */
+  update_life_info (NULL, UPDATE_LIFE_GLOBAL_RM_NOTES, PROP_DEATH_NOTES);
+
+  if (sparc_flag_schedule_insns2)
+    {
+      timevar_push (TV_SCHED2);
+      schedule_ebbs (rtl_dump_file);
+      timevar_pop (TV_SCHED2);
+    }
 }
 
 #include "gt-sparc.h"
--- ./config/sparc/sparc.h.~1~	Mon Jun 24 01:20:25 2002
+++ ./config/sparc/sparc.h	Wed Jun 26 01:08:37 2002
@@ -496,6 +496,10 @@ extern int target_flags;
 #define MASK_LONG_DOUBLE_128 0x8000000
 #define TARGET_LONG_DOUBLE_128 (target_flags & MASK_LONG_DOUBLE_128)
 
+/* Use normal second scheduling pass instead of schedule_ebbs.  */
+#define MASK_NORMAL_SCHED2 0x10000000
+#define TARGET_NORMAL_SCHED2 (target_flags & MASK_NORMAL_SCHED2)
+
 /* TARGET_HARD_MUL: Use hardware multiply instructions but not %y.
    TARGET_HARD_MUL32: Use hardware multiply instructions with rd %y
    to get high 32 bits.  False in V8+ or V9 because multiply stores
@@ -590,6 +594,8 @@ extern int target_flags;
      N_("Optimize tail call instructions in assembler and linker") },	\
     {"no-relax", 0,							\
      N_("Do not optimize tail call instructions in assembler or linker") }, \
+    {"normal-sched2", MASK_NORMAL_SCHED2,				\
+     N_("Do not use extended basic block scheduling") }, \
     SUBTARGET_SWITCHES			\
     { "", TARGET_DEFAULT, ""}}
 
@@ -2667,6 +2673,12 @@ case LABEL_REF: case SYMBOL_REF: case CO
          ? 2 \
          : (sparc_cpu == PROCESSOR_ULTRASPARC3 \
             ? 8 : 3))
+
+/* Run schedule_ebbs instead of the normal second scheduling pass
+   if the second scheduling pass was enabled.  */
+
+#define MACHINE_DEPENDENT_REORG(INSN) sparc_reorg (INSN)
+
 
 /* Control the assembler format that we output.  */
 
--- ./config/sparc/sparc-protos.h.~1~	Mon May 27 03:54:36 2002
+++ ./config/sparc/sparc-protos.h	Wed Jun 26 01:01:16 2002
@@ -121,6 +121,7 @@ extern int sparc_check_64 PARAMS ((rtx, 
 extern rtx gen_df_reg PARAMS ((rtx, int));
 extern int sparc_extra_constraint_check PARAMS ((rtx, int, int));
 extern int sparc_rtx_costs PARAMS ((rtx, enum rtx_code, enum rtx_code));
+extern void sparc_reorg PARAMS((rtx));
 #endif /* RTX_CODE */
 
 extern void sparc_output_mi_thunk PARAMS ((FILE *, tree, HOST_WIDE_INT, tree));