path: root/gcc/sched-ebb.c

/* Instruction scheduling pass.
   Copyright (C) 1992, 1993, 1994, 1995, 1996, 1997, 1998,
   1999, 2000, 2001, 2002 Free Software Foundation, Inc.
   Contributed by Michael Tiemann (tiemann@cygnus.com) Enhanced by,
   and currently maintained by, Jim Wilson (wilson@cygnus.com)

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 2, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING.  If not, write to the Free
Software Foundation, 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA.  */

#include "config.h"
#include "system.h"
#include "toplev.h"
#include "rtl.h"
#include "tm_p.h"
#include "hard-reg-set.h"
#include "basic-block.h"
#include "regs.h"
#include "function.h"
#include "flags.h"
#include "insn-config.h"
#include "insn-attr.h"
#include "except.h"
#include "toplev.h"
#include "recog.h"
#include "cfglayout.h"
#include "sched-int.h"

/* The number of insns to be scheduled in total.  */
static int target_n_insns;
/* The number of insns scheduled so far.  */
static int sched_n_insns;

/* Implementations of the sched_info functions for region scheduling.  */
static void init_ready_list PARAMS ((struct ready_list *));
static int can_schedule_ready_p PARAMS ((rtx));
static int new_ready PARAMS ((rtx));
static int schedule_more_p PARAMS ((void));
static const char *ebb_print_insn PARAMS ((rtx, int));
static int rank PARAMS ((rtx, rtx));
static int contributes_to_priority PARAMS ((rtx, rtx));
static void compute_jump_reg_dependencies PARAMS ((rtx, regset));
static void schedule_ebb PARAMS ((rtx, rtx));

/* Return nonzero if there are more insns that should be scheduled.  */

static int
schedule_more_p ()
{
  return sched_n_insns < target_n_insns;
}

/* Add all insns that are initially ready to the ready list READY.  Called
   once before scheduling a set of insns.  */

static void
init_ready_list (ready)
     struct ready_list *ready;
{
  rtx prev_head = current_sched_info->prev_head;
  rtx next_tail = current_sched_info->next_tail;
  rtx insn;

  target_n_insns = 0;
  sched_n_insns = 0;

#if 0
  /* Print debugging information.  */
  if (sched_verbose >= 5)
    debug_dependencies ();
#endif

  /* Initialize ready list with all 'ready' insns in target block.
     Count number of insns in the target block being scheduled.  */
  for (insn = NEXT_INSN (prev_head); insn != next_tail; insn = NEXT_INSN (insn))
    {
      rtx next;

      if (! INSN_P (insn))
	continue;
      next = NEXT_INSN (insn);

      if (INSN_DEP_COUNT (insn) == 0
	  && (SCHED_GROUP_P (next) == 0 || ! INSN_P (next)))
	ready_add (ready, insn);
      if (!(SCHED_GROUP_P (insn)))
	target_n_insns++;
    }
}

/* Called after taking INSN from the ready list.  Returns nonzero if this
   insn can be scheduled, nonzero if we should silently discard it.  */

static int
can_schedule_ready_p (insn)
     rtx insn ATTRIBUTE_UNUSED;
{
  sched_n_insns++;
  return 1;
}

/* Called after INSN has all its dependencies resolved.  Return nonzero
   if it should be moved to the ready list or the queue, or zero if we
   should silently discard it.  */
static int
new_ready (next)
     rtx next ATTRIBUTE_UNUSED;
{
  return 1;
}

/* Return a string that contains the insn uid and optionally anything else
   necessary to identify this insn in an output.  It's valid to use a
   static buffer for this.  The ALIGNED parameter should cause the string
   to be formatted so that multiple output lines will line up nicely.  */

static const char *
ebb_print_insn (insn, aligned)
     rtx insn;
     int aligned ATTRIBUTE_UNUSED;
{
  static char tmp[80];

  sprintf (tmp, "%4d", INSN_UID (insn));
  return tmp;
}

/* Compare priority of two insns.  Return a positive number if the second
   insn is to be preferred for scheduling, and a negative one if the first
   is to be preferred.  Zero if they are equally good.  */

static int
rank (insn1, insn2)
     rtx insn1 ATTRIBUTE_UNUSED, insn2 ATTRIBUTE_UNUSED;
{
  return 0;
}

/* NEXT is an instruction that depends on INSN (a backward dependence);
   return nonzero if we should include this dependence in priority
   calculations.  */

static int
contributes_to_priority (next, insn)
     rtx next ATTRIBUTE_UNUSED, insn ATTRIBUTE_UNUSED;
{
  return 1;
}

/* INSN is a JUMP_INSN.  Store the set of registers that must be considered
   to be set by this jump in SET.  */

static void
compute_jump_reg_dependencies (insn, set)
     rtx insn;
     regset set;
{
  basic_block b = BLOCK_FOR_INSN (insn);
  edge e;
  for (e = b->succ; e; e = e->succ_next)
    if ((e->flags & EDGE_FALLTHRU) == 0)
      {
	bitmap_operation (set, set, e->dest->global_live_at_start,
			  BITMAP_IOR);
      }
}

/* Used in schedule_insns to initialize current_sched_info for scheduling
   regions (or single basic blocks).  */

static struct sched_info ebb_sched_info =
{
  init_ready_list,
  can_schedule_ready_p,
  schedule_more_p,
  new_ready,
  rank,
  ebb_print_insn,
  contributes_to_priority,
  compute_jump_reg_dependencies,

  NULL, NULL,
  NULL, NULL,
  0, 1
};

/* Schedule a single extended basic block, defined by the boundaries HEAD
   and TAIL.  */

static void
schedule_ebb (head, tail)
     rtx head, tail;
{
  int n_insns;
  struct deps tmp_deps;

  if (no_real_insns_p (head, tail))
    return;

  init_deps_global ();

  /* Compute LOG_LINKS.  */
  init_deps (&tmp_deps);
  sched_analyze (&tmp_deps, head, tail);
  free_deps (&tmp_deps);

  /* Compute INSN_DEPEND.  */
  compute_forward_dependences (head, tail);

  /* Set priorities.  */
  n_insns = set_priorities (head, tail);

  current_sched_info->prev_head = PREV_INSN (head);
  current_sched_info->next_tail = NEXT_INSN (tail);

  if (write_symbols != NO_DEBUG)
    {
      save_line_notes (0, head, tail);
      rm_line_notes (head, tail);
    }

  /* rm_other_notes only removes notes which are _inside_ the
     block---that is, it won't remove notes before the first real insn
     or after the last real insn of the block.  So if the first insn
     has a REG_SAVE_NOTE which would otherwise be emitted before the
     insn, it is redundant with the note before the start of the
     block, and so we have to take it out.  */
  if (INSN_P (head))
    {
      rtx note;

      for (note = REG_NOTES (head); note; note = XEXP (note, 1))
	if (REG_NOTE_KIND (note) == REG_SAVE_NOTE)
	  {
	    remove_note (head, note);
	    note = XEXP (note, 1);
	    remove_note (head, note);
	  }
    }

  /* Remove remaining note insns from the block, save them in
     note_list.  These notes are restored at the end of
     schedule_block ().  */
  rm_other_notes (head, tail);

  current_sched_info->queue_must_finish_empty = 1;

  schedule_block (-1, n_insns);

  /* Sanity check: verify that all region insns were scheduled.  */
  if (sched_n_insns != n_insns)
    abort ();
  head = current_sched_info->head;
  tail = current_sched_info->tail;

  if (write_symbols != NO_DEBUG)
    restore_line_notes (head, tail);

  finish_deps_global ();
}

/* The one entry point in this file.  DUMP_FILE is the dump file for
   this pass.  */

void
schedule_ebbs (dump_file)
     FILE *dump_file;
{
  basic_block bb;

  /* Taking care of this degenerate case makes the rest of
     this code simpler.  */
  if (n_basic_blocks == 0)
    return;

  scope_to_insns_initialize ();

  sched_init (dump_file);

  current_sched_info = &ebb_sched_info;

  allocate_reg_life_data ();
  compute_bb_for_insn (get_max_uid ());

  /* Schedule every region in the subroutine.  */
  FOR_EACH_BB (bb)
    {
      rtx head = bb->head;
      rtx tail;

      for (;;)
	{
	  edge e;
	  tail = bb->end;
	  if (bb->next_bb == EXIT_BLOCK_PTR
	      || GET_CODE (bb->next_bb->head) == CODE_LABEL)
	    break;
	  for (e = bb->succ; e; e = e->succ_next)
	    if ((e->flags & EDGE_FALLTHRU) != 0)
	      break;
	  if (! e)
	    break;
	  if (GET_CODE (tail) == JUMP_INSN)
	    {
	      rtx x = find_reg_note (tail, REG_BR_PROB, 0);
	      if (x)
		{
		  int pred_val = INTVAL (XEXP (x, 0));
		  if (pred_val > REG_BR_PROB_BASE / 2)
		    break;
		}
	    }

	  bb = bb->next_bb;
	}

      /* Blah.  We should fix the rest of the code not to get confused by
	 a note or two.  */
      while (head != tail)
	{
	  if (GET_CODE (head) == NOTE)
	    head = NEXT_INSN (head);
	  else if (GET_CODE (tail) == NOTE)
	    tail = PREV_INSN (tail);
	  else if (GET_CODE (head) == CODE_LABEL)
	    head = NEXT_INSN (head);
	  else
	    break;
	}

      schedule_ebb (head, tail);
    }

  /* It doesn't make much sense to try and update life information here - we
     probably messed up even the flow graph.  */

  /* Reposition the prologue and epilogue notes in case we moved the
     prologue/epilogue insns.  */
  if (reload_completed)
    reposition_prologue_and_epilogue_notes (get_insns ());

  if (write_symbols != NO_DEBUG)
    rm_redundant_line_notes ();

  scope_to_insns_finalize ();

  sched_finish ();
}