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/* Instruction scheduling pass.

   Copyright (C) 1992, 1993, 1994, 1995, 1996, 1997, 1998,

   1999, 2000, 2001, 2002, 2003, 2004 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, 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301, USA.  */

#include "config.h"

#include "system.h"

#include "coretypes.h"

#include "tm.h"

#include "toplev.h"

#include "rtl.h"

#include "tm_p.h"

#include "hard-reg-set.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 "params.h"

#include "sched-int.h"

#include "target.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 (struct ready_list *);

static int can_schedule_ready_p (rtx);

static int new_ready (rtx);

static int schedule_more_p (void);

static const char *ebb_print_insn (rtx, int);

static int rank (rtx, rtx);

static int contributes_to_priority (rtx, rtx);

static void compute_jump_reg_dependencies (rtx, regset, regset, regset);

static basic_block earliest_block_with_similiar_load (basic_block, rtx);

static void add_deps_for_risky_insns (rtx, rtx);

static basic_block schedule_ebb (rtx, rtx);

static basic_block fix_basic_block_boundaries (basic_block, basic_block, rtx,

                                               rtx);

static void add_missing_bbs (rtx, basic_block, basic_block);

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

static int

schedule_more_p (void)

{

  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 (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))

    {

      if (INSN_DEP_COUNT (insn) == 0)

        ready_add (ready, 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 (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 (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 (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 (rtx insn1, rtx insn2)

{

  basic_block bb1 = BLOCK_FOR_INSN (insn1);

  basic_block bb2 = BLOCK_FOR_INSN (insn2);

  if (bb1->count > bb2->count

      || bb1->frequency > bb2->frequency)

    return -1;

  if (bb1->count < bb2->count

      || bb1->frequency < bb2->frequency)

    return 1;

  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 (rtx next ATTRIBUTE_UNUSED,

                         rtx insn ATTRIBUTE_UNUSED)

{

  return 1;

}

 /* INSN is a JUMP_INSN, COND_SET is the set of registers that are

    conditionally set before INSN.  Store the set of registers that

    must be considered as used by this jump in USED and that of

    registers that must be considered as set in SET.  */

static void

compute_jump_reg_dependencies (rtx insn, regset cond_set, regset used,

                               regset set)

{

  basic_block b = BLOCK_FOR_INSN (insn);

  edge e;

  edge_iterator ei;

  FOR_EACH_EDGE (e, ei, b->succs)

    if (e->flags & EDGE_FALLTHRU)

      /* The jump may be a by-product of a branch that has been merged

         in the main codepath after being conditionalized.  Therefore

         it may guard the fallthrough block from using a value that has

         conditionally overwritten that of the main codepath.  So we

         consider that it restores the value of the main codepath.  */

      bitmap_and (set, e->dest->il.rtl->global_live_at_start, cond_set);

    else

      bitmap_ior_into (used, e->dest->il.rtl->global_live_at_start);

}

/* 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, 0

};

/* It is possible that ebb scheduling eliminated some blocks.

   Place blocks from FIRST to LAST before BEFORE.  */

static void

add_missing_bbs (rtx before, basic_block first, basic_block last)

{

  for (; last != first->prev_bb; last = last->prev_bb)

    {

      before = emit_note_before (NOTE_INSN_BASIC_BLOCK, before);

      NOTE_BASIC_BLOCK (before) = last;

      BB_HEAD (last) = before;

      BB_END (last) = before;

      update_bb_for_insn (last);

    }

}

/* Fixup the CFG after EBB scheduling.  Re-recognize the basic

   block boundaries in between HEAD and TAIL and update basic block

   structures between BB and LAST.  */

static basic_block

fix_basic_block_boundaries (basic_block bb, basic_block last, rtx head,

                            rtx tail)

{

  rtx insn = head;

  rtx last_inside = BB_HEAD (bb);

  rtx aftertail = NEXT_INSN (tail);

  head = BB_HEAD (bb);

  for (; insn != aftertail; insn = NEXT_INSN (insn))

    {

      gcc_assert (!LABEL_P (insn));

      /* Create new basic blocks just before first insn.  */

      if (inside_basic_block_p (insn))

        {

          if (!last_inside)

            {

              rtx note;

              /* Re-emit the basic block note for newly found BB header.  */

              if (LABEL_P (insn))

                {

                  note = emit_note_after (NOTE_INSN_BASIC_BLOCK, insn);

                  head = insn;

                  last_inside = note;

                }

              else

                {

                  note = emit_note_before (NOTE_INSN_BASIC_BLOCK, insn);

                  head = note;

                  last_inside = insn;

                }

            }

          else

            last_inside = insn;

        }

      /* Control flow instruction terminate basic block.  It is possible

         that we've eliminated some basic blocks (made them empty).

         Find the proper basic block using BLOCK_FOR_INSN and arrange things in

         a sensible way by inserting empty basic blocks as needed.  */

      if (control_flow_insn_p (insn) || (insn == tail && last_inside))

        {

          basic_block curr_bb = BLOCK_FOR_INSN (insn);

          rtx note;

          if (!control_flow_insn_p (insn))

            curr_bb = last;

          if (bb == last->next_bb)

            {

              edge f;

              rtx h;

              edge_iterator ei;

              /* An obscure special case, where we do have partially dead

                 instruction scheduled after last control flow instruction.

                 In this case we can create new basic block.  It is

                 always exactly one basic block last in the sequence.  Handle

                 it by splitting the edge and repositioning the block.

                 This is somewhat hackish, but at least avoid cut&paste

                 A safer solution can be to bring the code into sequence,

                 do the split and re-emit it back in case this will ever

                 trigger problem.  */

              FOR_EACH_EDGE (f, ei, bb->prev_bb->succs)

                if (f->flags & EDGE_FALLTHRU)

                  break;

              if (f)

                {

                  last = curr_bb = split_edge (f);

                  h = BB_HEAD (curr_bb);

                  BB_HEAD (curr_bb) = head;

                  BB_END (curr_bb) = insn;

                  /* Edge splitting created misplaced BASIC_BLOCK note, kill

                     it.  */

                  delete_insn (h);

                }

              /* It may happen that code got moved past unconditional jump in

                 case the code is completely dead.  Kill it.  */

              else

                {

                  rtx next = next_nonnote_insn (insn);

                  delete_insn_chain (head, insn);

                  /* We keep some notes in the way that may split barrier from the

                     jump.  */

                  if (BARRIER_P (next))

                     {

                       emit_barrier_after (prev_nonnote_insn (head));

                       delete_insn (next);

                     }

                  insn = NULL;

                }

            }

          else

            {

              BB_HEAD (curr_bb) = head;

              BB_END (curr_bb) = insn;

              add_missing_bbs (BB_HEAD (curr_bb), bb, curr_bb->prev_bb);

            }

          note = LABEL_P (head) ? NEXT_INSN (head) : head;

          NOTE_BASIC_BLOCK (note) = curr_bb;

          update_bb_for_insn (curr_bb);

          bb = curr_bb->next_bb;

          last_inside = NULL;

          if (!insn)

             break;

        }

    }

  add_missing_bbs (BB_HEAD (last->next_bb), bb, last);

  return bb->prev_bb;

}

/* Returns the earliest block in EBB currently being processed where a

   "similar load" 'insn2' is found, and hence LOAD_INSN can move

   speculatively into the found block.  All the following must hold:

   (1) both loads have 1 base register (PFREE_CANDIDATEs).

   (2) load_insn and load2 have a def-use dependence upon

   the same insn 'insn1'.

   From all these we can conclude that the two loads access memory

   addresses that differ at most by a constant, and hence if moving

   load_insn would cause an exception, it would have been caused by

   load2 anyhow.

   The function uses list (given by LAST_BLOCK) of already processed

   blocks in EBB.  The list is formed in `add_deps_for_risky_insns'.  */

static basic_block

earliest_block_with_similiar_load (basic_block last_block, rtx load_insn)

{

  rtx back_link;

  basic_block bb, earliest_block = NULL;

  for (back_link = LOG_LINKS (load_insn);

       back_link;

       back_link = XEXP (back_link, 1))

    {

      rtx insn1 = XEXP (back_link, 0);

      if (GET_MODE (back_link) == VOIDmode)

        {

          /* Found a DEF-USE dependence (insn1, load_insn).  */

          rtx fore_link;

          for (fore_link = INSN_DEPEND (insn1);

               fore_link;

               fore_link = XEXP (fore_link, 1))

            {

              rtx insn2 = XEXP (fore_link, 0);

              basic_block insn2_block = BLOCK_FOR_INSN (insn2);

              if (GET_MODE (fore_link) == VOIDmode)

                {

                  if (earliest_block != NULL

                      && earliest_block->index < insn2_block->index)

                    continue;

                  /* Found a DEF-USE dependence (insn1, insn2).  */

                  if (haifa_classify_insn (insn2) != PFREE_CANDIDATE)

                    /* insn2 not guaranteed to be a 1 base reg load.  */

                    continue;

                  for (bb = last_block; bb; bb = bb->aux)

                    if (insn2_block == bb)

                      break;

                  if (!bb)

                    /* insn2 is the similar load.  */

                    earliest_block = insn2_block;

                }

            }

        }

    }

  return earliest_block;

}

/* The following function adds dependencies between jumps and risky

   insns in given ebb.  */

static void

add_deps_for_risky_insns (rtx head, rtx tail)

{

  rtx insn, prev;

  int class;

  rtx last_jump = NULL_RTX;

  rtx next_tail = NEXT_INSN (tail);

  basic_block last_block = NULL, bb;

  for (insn = head; insn != next_tail; insn = NEXT_INSN (insn))

    if (JUMP_P (insn))

      {

        bb = BLOCK_FOR_INSN (insn);

        bb->aux = last_block;

        last_block = bb;

        last_jump = insn;

      }

    else if (INSN_P (insn) && last_jump != NULL_RTX)

      {

        class = haifa_classify_insn (insn);

        prev = last_jump;

        switch (class)

          {

          case PFREE_CANDIDATE:

            if (flag_schedule_speculative_load)

              {

                bb = earliest_block_with_similiar_load (last_block, insn);

                if (bb)

                  {

                    bb = bb->aux;

                    if (!bb)

                      break;

                    prev = BB_END (bb);

                  }

              }

            /* Fall through.  */

          case TRAP_RISKY:

          case IRISKY:

          case PRISKY_CANDIDATE:

            /* ??? We could implement better checking PRISKY_CANDIDATEs

               analogous to sched-rgn.c.  */

            /* We can not change the mode of the backward

               dependency because REG_DEP_ANTI has the lowest

               rank.  */

            if (! sched_insns_conditions_mutex_p (insn, prev)

                && add_dependence (insn, prev, REG_DEP_ANTI))

              add_forward_dependence (prev, insn, REG_DEP_ANTI);

            break;

          default:

            break;

          }

      }

  /* Maintain the invariant that bb->aux is clear after use.  */

  while (last_block)

    {

      bb = last_block->aux;

      last_block->aux = NULL;

      last_block = bb;

    }

}

/* Schedule a single extended basic block, defined by the boundaries HEAD

   and TAIL.  */

static basic_block

schedule_ebb (rtx head, rtx tail)

{

  int n_insns;

  basic_block b;

  struct deps tmp_deps;

  basic_block first_bb = BLOCK_FOR_INSN (head);

  basic_block last_bb = BLOCK_FOR_INSN (tail);

  if (no_real_insns_p (head, tail))

    return BLOCK_FOR_INSN (tail);

  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);

  add_deps_for_risky_insns (head, tail);

  if (targetm.sched.dependencies_evaluation_hook)

    targetm.sched.dependencies_evaluation_hook (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 (first_bb->index, 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);

    }

  /* 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.  */

  gcc_assert (sched_n_insns == n_insns);

  head = current_sched_info->head;

  tail = current_sched_info->tail;

  if (write_symbols != NO_DEBUG)

    restore_line_notes (head, tail);

  b = fix_basic_block_boundaries (first_bb, last_bb, head, tail);

  finish_deps_global ();

  return b;

}

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

   this pass.  */

void

schedule_ebbs (FILE *dump_file)

{

  basic_block bb;

  int probability_cutoff;

  if (profile_info && flag_branch_probabilities)

    probability_cutoff = PARAM_VALUE (TRACER_MIN_BRANCH_PROBABILITY_FEEDBACK);

  else

    probability_cutoff = PARAM_VALUE (TRACER_MIN_BRANCH_PROBABILITY);

  probability_cutoff = REG_BR_PROB_BASE / 100 * probability_cutoff;

  /* Taking care of this degenerate case makes the rest of

     this code simpler.  */

  if (n_basic_blocks == 0)

    return;

  sched_init (dump_file);

  current_sched_info = &ebb_sched_info;

  compute_bb_for_insn ();

  /* Schedule every region in the subroutine.  */

  FOR_EACH_BB (bb)

    {

      rtx head = BB_HEAD (bb);

      rtx tail;

      for (;;)

        {

          edge e;

          edge_iterator ei;

          tail = BB_END (bb);

          if (bb->next_bb == EXIT_BLOCK_PTR

              || LABEL_P (BB_HEAD (bb->next_bb)))

            break;

          FOR_EACH_EDGE (e, ei, bb->succs)

            if ((e->flags & EDGE_FALLTHRU) != 0)

              break;

          if (! e)

            break;

          if (e->probability <= probability_cutoff)

            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 (NOTE_P (head))

            head = NEXT_INSN (head);

          else if (NOTE_P (tail))

            tail = PREV_INSN (tail);

          else if (LABEL_P (head))

            head = NEXT_INSN (head);

          else

            break;

        }

      bb = schedule_ebb (head, tail);

    }

  /* Updating life info can be done by local propagation over the modified

     superblocks.  */

  /* 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 ();

  sched_finish ();

}