[gcc.git] / gcc / sched-deps.c

/* Instruction scheduling pass.  This file computes dependencies between
   instructions.
   Copyright (C) 1992, 1993, 1994, 1995, 1996, 1997, 1998,
   1999, 2000 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 GNU CC.

GNU CC 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.

GNU CC 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 GNU CC; see the file COPYING.  If not, write to the Free
the Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA.  */
\f
#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 "sched-int.h"

extern char *reg_known_equiv_p;
extern rtx *reg_known_value;

static regset_head reg_pending_sets_head;
static regset_head reg_pending_clobbers_head;

static regset reg_pending_sets;
static regset reg_pending_clobbers;
static int reg_pending_sets_all;

/* To speed up the test for duplicate dependency links we keep a
   record of dependencies created by add_dependence when the average
   number of instructions in a basic block is very large.

   Studies have shown that there is typically around 5 instructions between
   branches for typical C code.  So we can make a guess that the average
   basic block is approximately 5 instructions long; we will choose 100X
   the average size as a very large basic block.

   Each insn has associated bitmaps for its dependencies.  Each bitmap
   has enough entries to represent a dependency on any other insn in
   the insn chain.  All bitmap for true dependencies cache is
   allocated then the rest two ones are also allocated. */
static sbitmap *true_dependency_cache;
static sbitmap *anti_dependency_cache;
static sbitmap *output_dependency_cache;

/* To speed up checking consistency of formed forward insn
   dependencies we use the following cache.  Another possible solution
   could be switching off checking duplication of insns in forward
   dependencies. */
#ifdef ENABLE_CHECKING
static sbitmap *forward_dependency_cache;
#endif

static int deps_may_trap_p PARAMS ((rtx));
static void remove_dependence PARAMS ((rtx, rtx));
static void set_sched_group_p PARAMS ((rtx));

static void flush_pending_lists PARAMS ((struct deps *, rtx, int));
static void sched_analyze_1 PARAMS ((struct deps *, rtx, rtx));
static void sched_analyze_2 PARAMS ((struct deps *, rtx, rtx));
static void sched_analyze_insn PARAMS ((struct deps *, rtx, rtx, rtx));
static rtx group_leader PARAMS ((rtx));

static rtx get_condition PARAMS ((rtx));
static int conditions_mutex_p PARAMS ((rtx, rtx));
\f
/* Return nonzero if a load of the memory reference MEM can cause a trap.  */

static int
deps_may_trap_p (mem)
     rtx mem;
{
  rtx addr = XEXP (mem, 0);

  if (REG_P (addr)
      && REGNO (addr) >= FIRST_PSEUDO_REGISTER
      && reg_known_value[REGNO (addr)])
    addr = reg_known_value[REGNO (addr)];
  return rtx_addr_can_trap_p (addr);
}
\f
/* Return the INSN_LIST containing INSN in LIST, or NULL
   if LIST does not contain INSN.  */

HAIFA_INLINE rtx
find_insn_list (insn, list)
     rtx insn;
     rtx list;
{
  while (list)
    {
      if (XEXP (list, 0) == insn)
        return list;
      list = XEXP (list, 1);
    }
  return 0;
}

/* Return 1 if the pair (insn, x) is found in (LIST, LIST1), or 0
   otherwise.  */

HAIFA_INLINE int
find_insn_mem_list (insn, x, list, list1)
     rtx insn, x;
     rtx list, list1;
{
  while (list)
    {
      if (XEXP (list, 0) == insn
          && XEXP (list1, 0) == x)
        return 1;
      list = XEXP (list, 1);
      list1 = XEXP (list1, 1);
    }
  return 0;
}
\f
/* Find the condition under which INSN is executed.  */

static rtx
get_condition (insn)
     rtx insn;
{
  rtx pat = PATTERN (insn);
  rtx cond;

  if (pat == 0)
    return 0;
  if (GET_CODE (pat) == COND_EXEC)
    return COND_EXEC_TEST (pat);
  if (GET_CODE (insn) != JUMP_INSN)
    return 0;
  if (GET_CODE (pat) != SET || SET_SRC (pat) != pc_rtx)
    return 0;
  if (GET_CODE (SET_DEST (pat)) != IF_THEN_ELSE)
    return 0;
  pat = SET_DEST (pat);
  cond = XEXP (pat, 0);
  if (GET_CODE (XEXP (cond, 1)) == LABEL_REF
      && XEXP (cond, 2) == pc_rtx)
    return cond;
  else if (GET_CODE (XEXP (cond, 2)) == LABEL_REF
           && XEXP (cond, 1) == pc_rtx)
    return gen_rtx_fmt_ee (reverse_condition (GET_CODE (cond)), GET_MODE (cond),
                           XEXP (cond, 0), XEXP (cond, 1));
  else
    return 0;
}

/* Return nonzero if conditions COND1 and COND2 can never be both true.  */

static int
conditions_mutex_p (cond1, cond2)
     rtx cond1, cond2;
{
  if (GET_RTX_CLASS (GET_CODE (cond1)) == '<'
      && GET_RTX_CLASS (GET_CODE (cond2)) == '<'
      && GET_CODE (cond1) == reverse_condition (GET_CODE (cond2))
      && XEXP (cond1, 0) == XEXP (cond2, 0)
      && XEXP (cond1, 1) == XEXP (cond2, 1))
    return 1;
  return 0;
}
\f
/* Add ELEM wrapped in an INSN_LIST with reg note kind DEP_TYPE to the
   LOG_LINKS of INSN, if not already there.  DEP_TYPE indicates the type
   of dependence that this link represents.  */

void
add_dependence (insn, elem, dep_type)
     rtx insn;
     rtx elem;
     enum reg_note dep_type;
{
  rtx link, next;
  int present_p;
  enum reg_note present_dep_type;
  rtx cond1, cond2;

  /* Don't depend an insn on itself.  */
  if (insn == elem)
    return;

  /* We can get a dependency on deleted insns due to optimizations in
     the register allocation and reloading or due to splitting.  Any
     such dependency is useless and can be ignored.  */
  if (GET_CODE (elem) == NOTE)
    return;

  /* flow.c doesn't handle conditional lifetimes entirely correctly;
     calls mess up the conditional lifetimes.  */
  if (GET_CODE (insn) != CALL_INSN && GET_CODE (elem) != CALL_INSN)
    {
      cond1 = get_condition (insn);
      cond2 = get_condition (elem);
      if (cond1 && cond2 && conditions_mutex_p (cond1, cond2))
        return;
    }

  /* If elem is part of a sequence that must be scheduled together, then
     make the dependence point to the last insn of the sequence.
     When HAVE_cc0, it is possible for NOTEs to exist between users and
     setters of the condition codes, so we must skip past notes here.
     Otherwise, NOTEs are impossible here.  */
  next = next_nonnote_insn (elem);
  if (next && SCHED_GROUP_P (next)
      && GET_CODE (next) != CODE_LABEL)
    {
      /* Notes will never intervene here though, so don't bother checking
         for them.  */
      /* Hah!  Wrong.  */
      /* We must reject CODE_LABELs, so that we don't get confused by one
         that has LABEL_PRESERVE_P set, which is represented by the same
         bit in the rtl as SCHED_GROUP_P.  A CODE_LABEL can never be
         SCHED_GROUP_P.  */

      rtx nnext;
      while ((nnext = next_nonnote_insn (next)) != NULL
             && SCHED_GROUP_P (nnext)
             && GET_CODE (nnext) != CODE_LABEL)
        next = nnext;

      /* Again, don't depend an insn on itself.  */
      if (insn == next)
        return;

      /* Make the dependence to NEXT, the last insn of the group, instead
         of the original ELEM.  */
      elem = next;
    }

  present_p = 1;
#ifdef INSN_SCHEDULING
  /* ??? No good way to tell from here whether we're doing interblock
     scheduling.  Possibly add another callback.  */
#if 0
  /* (This code is guarded by INSN_SCHEDULING, otherwise INSN_BB is undefined.)
     No need for interblock dependences with calls, since
     calls are not moved between blocks.   Note: the edge where
     elem is a CALL is still required.  */
  if (GET_CODE (insn) == CALL_INSN
      && (INSN_BB (elem) != INSN_BB (insn)))
    return;
#endif

  /* If we already have a dependency for ELEM, then we do not need to
     do anything.  Avoiding the list walk below can cut compile times
     dramatically for some code.  */
  if (true_dependency_cache != NULL)
    {
      if (anti_dependency_cache == NULL || output_dependency_cache == NULL)
        abort ();
      if (TEST_BIT (true_dependency_cache[INSN_LUID (insn)], INSN_LUID (elem)))
        present_dep_type = 0;
      else if (TEST_BIT (anti_dependency_cache[INSN_LUID (insn)],
                         INSN_LUID (elem)))
        present_dep_type = REG_DEP_ANTI;
      else if (TEST_BIT (output_dependency_cache[INSN_LUID (insn)],
                         INSN_LUID (elem)))
        present_dep_type = REG_DEP_OUTPUT;
      else 
        present_p = 0;
      if (present_p && (int) dep_type >= (int) present_dep_type)
        return;
    }
#endif

  /* Check that we don't already have this dependence.  */
  if (present_p)
    for (link = LOG_LINKS (insn); link; link = XEXP (link, 1))
      if (XEXP (link, 0) == elem)
        {
#ifdef INSN_SCHEDULING
          /* Clear corresponding cache entry because type of the link
             may be changed. */
          if (true_dependency_cache != NULL)
            {
              if (REG_NOTE_KIND (link) == REG_DEP_ANTI)
                RESET_BIT (anti_dependency_cache[INSN_LUID (insn)],
                           INSN_LUID (elem));
              else if (REG_NOTE_KIND (link) == REG_DEP_OUTPUT
                       && output_dependency_cache)
                RESET_BIT (output_dependency_cache[INSN_LUID (insn)],
                           INSN_LUID (elem));
              else
                abort ();
            }
#endif

          /* If this is a more restrictive type of dependence than the existing
             one, then change the existing dependence to this type.  */
          if ((int) dep_type < (int) REG_NOTE_KIND (link))
            PUT_REG_NOTE_KIND (link, dep_type);
          
#ifdef INSN_SCHEDULING
          /* If we are adding a dependency to INSN's LOG_LINKs, then
             note that in the bitmap caches of dependency information. */
          if (true_dependency_cache != NULL)
            {
              if ((int)REG_NOTE_KIND (link) == 0)
                SET_BIT (true_dependency_cache[INSN_LUID (insn)],
                         INSN_LUID (elem));
              else if (REG_NOTE_KIND (link) == REG_DEP_ANTI)
                SET_BIT (anti_dependency_cache[INSN_LUID (insn)],
                         INSN_LUID (elem));
              else if (REG_NOTE_KIND (link) == REG_DEP_OUTPUT)
                SET_BIT (output_dependency_cache[INSN_LUID (insn)],
                         INSN_LUID (elem));
            }
#endif
          return;
      }
  /* Might want to check one level of transitivity to save conses.  */

  link = alloc_INSN_LIST (elem, LOG_LINKS (insn));
  LOG_LINKS (insn) = link;

  /* Insn dependency, not data dependency.  */
  PUT_REG_NOTE_KIND (link, dep_type);

#ifdef INSN_SCHEDULING
  /* If we are adding a dependency to INSN's LOG_LINKs, then note that
     in the bitmap caches of dependency information. */
  if (true_dependency_cache != NULL)
    {
      if ((int)dep_type == 0)
        SET_BIT (true_dependency_cache[INSN_LUID (insn)], INSN_LUID (elem));
      else if (dep_type == REG_DEP_ANTI)
        SET_BIT (anti_dependency_cache[INSN_LUID (insn)], INSN_LUID (elem));
      else if (dep_type == REG_DEP_OUTPUT)
        SET_BIT (output_dependency_cache[INSN_LUID (insn)], INSN_LUID (elem));
    }
#endif
}

/* Remove ELEM wrapped in an INSN_LIST from the LOG_LINKS
   of INSN.  Abort if not found.  */

static void
remove_dependence (insn, elem)
     rtx insn;
     rtx elem;
{
  rtx prev, link, next;
  int found = 0;

  for (prev = 0, link = LOG_LINKS (insn); link; link = next)
    {
      next = XEXP (link, 1);
      if (XEXP (link, 0) == elem)
        {
          if (prev)
            XEXP (prev, 1) = next;
          else
            LOG_LINKS (insn) = next;

#ifdef INSN_SCHEDULING
          /* If we are removing a dependency from the LOG_LINKS list,
             make sure to remove it from the cache too.  */
          if (true_dependency_cache != NULL)
            {
              if (REG_NOTE_KIND (link) == 0)
                RESET_BIT (true_dependency_cache[INSN_LUID (insn)],
                           INSN_LUID (elem));
              else if (REG_NOTE_KIND (link) == REG_DEP_ANTI)
                RESET_BIT (anti_dependency_cache[INSN_LUID (insn)],
                           INSN_LUID (elem));
              else if (REG_NOTE_KIND (link) == REG_DEP_OUTPUT)
                RESET_BIT (output_dependency_cache[INSN_LUID (insn)],
                           INSN_LUID (elem));
            }
#endif

          free_INSN_LIST_node (link);

          found = 1;
        }
      else
        prev = link;
    }

  if (!found)
    abort ();
  return;
}

/* Return an insn which represents a SCHED_GROUP, which is
   the last insn in the group.  */

static rtx
group_leader (insn)
     rtx insn;
{
  rtx prev;

  do
    {
      prev = insn;
      insn = next_nonnote_insn (insn);
    }
  while (insn && SCHED_GROUP_P (insn) && (GET_CODE (insn) != CODE_LABEL));

  return prev;
}

/* Set SCHED_GROUP_P and care for the rest of the bookkeeping that
   goes along with that.  */

static void
set_sched_group_p (insn)
     rtx insn;
{
  rtx link, prev;

  SCHED_GROUP_P (insn) = 1;

  /* There may be a note before this insn now, but all notes will
     be removed before we actually try to schedule the insns, so
     it won't cause a problem later.  We must avoid it here though.  */
  prev = prev_nonnote_insn (insn);

  /* Make a copy of all dependencies on the immediately previous insn,
     and add to this insn.  This is so that all the dependencies will
     apply to the group.  Remove an explicit dependence on this insn
     as SCHED_GROUP_P now represents it.  */

  if (find_insn_list (prev, LOG_LINKS (insn)))
    remove_dependence (insn, prev);

  for (link = LOG_LINKS (prev); link; link = XEXP (link, 1))
    add_dependence (insn, XEXP (link, 0), REG_NOTE_KIND (link));
}
\f
/* Process an insn's memory dependencies.  There are four kinds of
   dependencies:

   (0) read dependence: read follows read
   (1) true dependence: read follows write
   (2) anti dependence: write follows read
   (3) output dependence: write follows write

   We are careful to build only dependencies which actually exist, and
   use transitivity to avoid building too many links.  */

/* Add an INSN and MEM reference pair to a pending INSN_LIST and MEM_LIST.
   The MEM is a memory reference contained within INSN, which we are saving
   so that we can do memory aliasing on it.  */

void
add_insn_mem_dependence (deps, insn_list, mem_list, insn, mem)
     struct deps *deps;
     rtx *insn_list, *mem_list, insn, mem;
{
  register rtx link;

  link = alloc_INSN_LIST (insn, *insn_list);
  *insn_list = link;

  link = alloc_EXPR_LIST (VOIDmode, mem, *mem_list);
  *mem_list = link;

  deps->pending_lists_length++;
}

/* Make a dependency between every memory reference on the pending lists
   and INSN, thus flushing the pending lists.  If ONLY_WRITE, don't flush
   the read list.  */

static void
flush_pending_lists (deps, insn, only_write)
     struct deps *deps;
     rtx insn;
     int only_write;
{
  rtx u;
  rtx link;

  while (deps->pending_read_insns && ! only_write)
    {
      add_dependence (insn, XEXP (deps->pending_read_insns, 0),
                      REG_DEP_ANTI);

      link = deps->pending_read_insns;
      deps->pending_read_insns = XEXP (deps->pending_read_insns, 1);
      free_INSN_LIST_node (link);

      link = deps->pending_read_mems;
      deps->pending_read_mems = XEXP (deps->pending_read_mems, 1);
      free_EXPR_LIST_node (link);
    }
  while (deps->pending_write_insns)
    {
      add_dependence (insn, XEXP (deps->pending_write_insns, 0),
                      REG_DEP_ANTI);

      link = deps->pending_write_insns;
      deps->pending_write_insns = XEXP (deps->pending_write_insns, 1);
      free_INSN_LIST_node (link);

      link = deps->pending_write_mems;
      deps->pending_write_mems = XEXP (deps->pending_write_mems, 1);
      free_EXPR_LIST_node (link);
    }
  deps->pending_lists_length = 0;

  /* last_pending_memory_flush is now a list of insns.  */
  for (u = deps->last_pending_memory_flush; u; u = XEXP (u, 1))
    add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);

  free_INSN_LIST_list (&deps->last_pending_memory_flush);
  deps->last_pending_memory_flush = alloc_INSN_LIST (insn, NULL_RTX);
}
\f
/* Analyze a single SET, CLOBBER, PRE_DEC, POST_DEC, PRE_INC or POST_INC
   rtx, X, creating all dependencies generated by the write to the
   destination of X, and reads of everything mentioned.  */

static void
sched_analyze_1 (deps, x, insn)
     struct deps *deps;
     rtx x;
     rtx insn;
{
  register int regno;
  register rtx dest = XEXP (x, 0);
  enum rtx_code code = GET_CODE (x);

  if (dest == 0)
    return;

  if (GET_CODE (dest) == PARALLEL)
    {
      register int i;

      for (i = XVECLEN (dest, 0) - 1; i >= 0; i--)
        if (XEXP (XVECEXP (dest, 0, i), 0) != 0)
          sched_analyze_1 (deps,
                           gen_rtx_CLOBBER (VOIDmode,
                                            XEXP (XVECEXP (dest, 0, i), 0)),
                           insn);

      if (GET_CODE (x) == SET)
        sched_analyze_2 (deps, SET_SRC (x), insn);
      return;
    }

  while (GET_CODE (dest) == STRICT_LOW_PART || GET_CODE (dest) == SUBREG
         || GET_CODE (dest) == ZERO_EXTRACT || GET_CODE (dest) == SIGN_EXTRACT)
    {
      if (GET_CODE (dest) == ZERO_EXTRACT || GET_CODE (dest) == SIGN_EXTRACT)
        {
          /* The second and third arguments are values read by this insn.  */
          sched_analyze_2 (deps, XEXP (dest, 1), insn);
          sched_analyze_2 (deps, XEXP (dest, 2), insn);
        }
      dest = XEXP (dest, 0);
    }

  if (GET_CODE (dest) == REG)
    {
      register int i;

      regno = REGNO (dest);

      /* A hard reg in a wide mode may really be multiple registers.
         If so, mark all of them just like the first.  */
      if (regno < FIRST_PSEUDO_REGISTER)
        {
          i = HARD_REGNO_NREGS (regno, GET_MODE (dest));
          while (--i >= 0)
            {
              int r = regno + i;
              rtx u;

              for (u = deps->reg_last[r].uses; u; u = XEXP (u, 1))
                add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);

              for (u = deps->reg_last[r].sets; u; u = XEXP (u, 1))
                add_dependence (insn, XEXP (u, 0), REG_DEP_OUTPUT);

              /* Clobbers need not be ordered with respect to one
                 another, but sets must be ordered with respect to a
                 pending clobber.  */
              if (code == SET)
                {
                  if (GET_CODE (PATTERN (insn)) != COND_EXEC)
                    free_INSN_LIST_list (&deps->reg_last[r].uses);
                  for (u = deps->reg_last[r].clobbers; u; u = XEXP (u, 1))
                    add_dependence (insn, XEXP (u, 0), REG_DEP_OUTPUT);
                  SET_REGNO_REG_SET (reg_pending_sets, r);
                }
              else
                SET_REGNO_REG_SET (reg_pending_clobbers, r);

              /* Function calls clobber all call_used regs.  */
              if (global_regs[r] || (code == SET && call_used_regs[r]))
                for (u = deps->last_function_call; u; u = XEXP (u, 1))
                  add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);
            }
        }
      /* ??? Reload sometimes emits USEs and CLOBBERs of pseudos that
         it does not reload.  Ignore these as they have served their
         purpose already.  */
      else if (regno >= deps->max_reg)
        {
          if (GET_CODE (PATTERN (insn)) != USE
              && GET_CODE (PATTERN (insn)) != CLOBBER)
            abort ();
        }
      else
        {
          rtx u;

          for (u = deps->reg_last[regno].uses; u; u = XEXP (u, 1))
            add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);

          for (u = deps->reg_last[regno].sets; u; u = XEXP (u, 1))
            add_dependence (insn, XEXP (u, 0), REG_DEP_OUTPUT);

          if (code == SET)
            {
              if (GET_CODE (PATTERN (insn)) != COND_EXEC)
                free_INSN_LIST_list (&deps->reg_last[regno].uses);
              for (u = deps->reg_last[regno].clobbers; u; u = XEXP (u, 1))
                add_dependence (insn, XEXP (u, 0), REG_DEP_OUTPUT);
              SET_REGNO_REG_SET (reg_pending_sets, regno);
            }
          else
            SET_REGNO_REG_SET (reg_pending_clobbers, regno);

          /* Pseudos that are REG_EQUIV to something may be replaced
             by that during reloading.  We need only add dependencies for
             the address in the REG_EQUIV note.  */
          if (!reload_completed
              && reg_known_equiv_p[regno]
              && GET_CODE (reg_known_value[regno]) == MEM)
            sched_analyze_2 (deps, XEXP (reg_known_value[regno], 0), insn);

          /* Don't let it cross a call after scheduling if it doesn't
             already cross one.  */

          if (REG_N_CALLS_CROSSED (regno) == 0)
            for (u = deps->last_function_call; u; u = XEXP (u, 1))
              add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);
        }
    }
  else if (GET_CODE (dest) == MEM)
    {
      /* Writing memory.  */

      if (deps->pending_lists_length > 32)
        {
          /* Flush all pending reads and writes to prevent the pending lists
             from getting any larger.  Insn scheduling runs too slowly when
             these lists get long.  The number 32 was chosen because it
             seems like a reasonable number.  When compiling GCC with itself,
             this flush occurs 8 times for sparc, and 10 times for m88k using
             the number 32.  */
          flush_pending_lists (deps, insn, 0);
        }
      else
        {
          rtx u;
          rtx pending, pending_mem;

          pending = deps->pending_read_insns;
          pending_mem = deps->pending_read_mems;
          while (pending)
            {
              if (anti_dependence (XEXP (pending_mem, 0), dest))
                add_dependence (insn, XEXP (pending, 0), REG_DEP_ANTI);

              pending = XEXP (pending, 1);
              pending_mem = XEXP (pending_mem, 1);
            }

          pending = deps->pending_write_insns;
          pending_mem = deps->pending_write_mems;
          while (pending)
            {
              if (output_dependence (XEXP (pending_mem, 0), dest))
                add_dependence (insn, XEXP (pending, 0), REG_DEP_OUTPUT);

              pending = XEXP (pending, 1);
              pending_mem = XEXP (pending_mem, 1);
            }

          for (u = deps->last_pending_memory_flush; u; u = XEXP (u, 1))
            add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);

          add_insn_mem_dependence (deps, &deps->pending_write_insns,
                                   &deps->pending_write_mems, insn, dest);
        }
      sched_analyze_2 (deps, XEXP (dest, 0), insn);
    }

  /* Analyze reads.  */
  if (GET_CODE (x) == SET)
    sched_analyze_2 (deps, SET_SRC (x), insn);
}

/* Analyze the uses of memory and registers in rtx X in INSN.  */

static void
sched_analyze_2 (deps, x, insn)
     struct deps *deps;
     rtx x;
     rtx insn;
{
  register int i;
  register int j;
  register enum rtx_code code;
  register const char *fmt;

  if (x == 0)
    return;

  code = GET_CODE (x);

  switch (code)
    {
    case CONST_INT:
    case CONST_DOUBLE:
    case SYMBOL_REF:
    case CONST:
    case LABEL_REF:
      /* Ignore constants.  Note that we must handle CONST_DOUBLE here
         because it may have a cc0_rtx in its CONST_DOUBLE_CHAIN field, but
         this does not mean that this insn is using cc0.  */
      return;

#ifdef HAVE_cc0
    case CC0:
      /* User of CC0 depends on immediately preceding insn.  */
      set_sched_group_p (insn);
      return;
#endif

    case REG:
      {
        rtx u;
        int regno = REGNO (x);
        if (regno < FIRST_PSEUDO_REGISTER)
          {
            int i;

            i = HARD_REGNO_NREGS (regno, GET_MODE (x));
            while (--i >= 0)
              {
                int r = regno + i;
                deps->reg_last[r].uses
                  = alloc_INSN_LIST (insn, deps->reg_last[r].uses);
                SET_REGNO_REG_SET (&deps->reg_last_in_use, r);

                for (u = deps->reg_last[r].sets; u; u = XEXP (u, 1))
                  add_dependence (insn, XEXP (u, 0), 0);

                /* ??? This should never happen.  */
                for (u = deps->reg_last[r].clobbers; u; u = XEXP (u, 1))
                  add_dependence (insn, XEXP (u, 0), 0);

                if (call_used_regs[r] || global_regs[r])
                  /* Function calls clobber all call_used regs.  */
                  for (u = deps->last_function_call; u; u = XEXP (u, 1))
                    add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);
              }
          }
        /* ??? Reload sometimes emits USEs and CLOBBERs of pseudos that
           it does not reload.  Ignore these as they have served their
           purpose already.  */
        else if (regno >= deps->max_reg)
          {
            if (GET_CODE (PATTERN (insn)) != USE
                && GET_CODE (PATTERN (insn)) != CLOBBER)
              abort ();
          }
        else
          {
            deps->reg_last[regno].uses
              = alloc_INSN_LIST (insn, deps->reg_last[regno].uses);
            SET_REGNO_REG_SET (&deps->reg_last_in_use, regno);

            for (u = deps->reg_last[regno].sets; u; u = XEXP (u, 1))
              add_dependence (insn, XEXP (u, 0), 0);

            /* ??? This should never happen.  */
            for (u = deps->reg_last[regno].clobbers; u; u = XEXP (u, 1))
              add_dependence (insn, XEXP (u, 0), 0);

            /* Pseudos that are REG_EQUIV to something may be replaced
               by that during reloading.  We need only add dependencies for
               the address in the REG_EQUIV note.  */
            if (!reload_completed
                && reg_known_equiv_p[regno]
                && GET_CODE (reg_known_value[regno]) == MEM)
              sched_analyze_2 (deps, XEXP (reg_known_value[regno], 0), insn);

            /* If the register does not already cross any calls, then add this
               insn to the sched_before_next_call list so that it will still
               not cross calls after scheduling.  */
            if (REG_N_CALLS_CROSSED (regno) == 0)
              add_dependence (deps->sched_before_next_call, insn,
                              REG_DEP_ANTI);
          }
        return;
      }

    case MEM:
      {
        /* Reading memory.  */
        rtx u;
        rtx pending, pending_mem;

        pending = deps->pending_read_insns;
        pending_mem = deps->pending_read_mems;
        while (pending)
          {
            if (read_dependence (XEXP (pending_mem, 0), x))
              add_dependence (insn, XEXP (pending, 0), REG_DEP_ANTI);

            pending = XEXP (pending, 1);
            pending_mem = XEXP (pending_mem, 1);
          }

        pending = deps->pending_write_insns;
        pending_mem = deps->pending_write_mems;
        while (pending)
          {
            if (true_dependence (XEXP (pending_mem, 0), VOIDmode,
                                 x, rtx_varies_p))
              add_dependence (insn, XEXP (pending, 0), 0);

            pending = XEXP (pending, 1);
            pending_mem = XEXP (pending_mem, 1);
          }

        for (u = deps->last_pending_memory_flush; u; u = XEXP (u, 1))
          if (GET_CODE (XEXP (u, 0)) != JUMP_INSN
              || deps_may_trap_p (x))
            add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);

        /* Always add these dependencies to pending_reads, since
           this insn may be followed by a write.  */
        add_insn_mem_dependence (deps, &deps->pending_read_insns,
                                 &deps->pending_read_mems, insn, x);

        /* Take advantage of tail recursion here.  */
        sched_analyze_2 (deps, XEXP (x, 0), insn);
        return;
      }

    /* Force pending stores to memory in case a trap handler needs them.  */
    case TRAP_IF:
      flush_pending_lists (deps, insn, 1);
      break;

    case ASM_OPERANDS:
    case ASM_INPUT:
    case UNSPEC_VOLATILE:
      {
        rtx u;

        /* Traditional and volatile asm instructions must be considered to use
           and clobber all hard registers, all pseudo-registers and all of
           memory.  So must TRAP_IF and UNSPEC_VOLATILE operations.

           Consider for instance a volatile asm that changes the fpu rounding
           mode.  An insn should not be moved across this even if it only uses
           pseudo-regs because it might give an incorrectly rounded result.  */
        if (code != ASM_OPERANDS || MEM_VOLATILE_P (x))
          {
            for (i = 0; i < deps->max_reg; i++)
              {
                struct deps_reg *reg_last = &deps->reg_last[i];

                for (u = reg_last->uses; u; u = XEXP (u, 1))
                  add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);
                for (u = reg_last->sets; u; u = XEXP (u, 1))
                  add_dependence (insn, XEXP (u, 0), 0);
                for (u = reg_last->clobbers; u; u = XEXP (u, 1))
                  add_dependence (insn, XEXP (u, 0), 0);

                if (GET_CODE (PATTERN (insn)) != COND_EXEC)
                  free_INSN_LIST_list (&reg_last->uses);
              }
            reg_pending_sets_all = 1;

            flush_pending_lists (deps, insn, 0);
          }

        /* For all ASM_OPERANDS, we must traverse the vector of input operands.
           We can not just fall through here since then we would be confused
           by the ASM_INPUT rtx inside ASM_OPERANDS, which do not indicate
           traditional asms unlike their normal usage.  */

        if (code == ASM_OPERANDS)
          {
            for (j = 0; j < ASM_OPERANDS_INPUT_LENGTH (x); j++)
              sched_analyze_2 (deps, ASM_OPERANDS_INPUT (x, j), insn);
            return;
          }
        break;
      }

    case PRE_DEC:
    case POST_DEC:
    case PRE_INC:
    case POST_INC:
      /* These both read and modify the result.  We must handle them as writes
         to get proper dependencies for following instructions.  We must handle
         them as reads to get proper dependencies from this to previous
         instructions.  Thus we need to pass them to both sched_analyze_1
         and sched_analyze_2.  We must call sched_analyze_2 first in order
         to get the proper antecedent for the read.  */
      sched_analyze_2 (deps, XEXP (x, 0), insn);
      sched_analyze_1 (deps, x, insn);
      return;

    case POST_MODIFY:
    case PRE_MODIFY:
      /* op0 = op0 + op1 */
      sched_analyze_2 (deps, XEXP (x, 0), insn);
      sched_analyze_2 (deps, XEXP (x, 1), insn);
      sched_analyze_1 (deps, x, insn);
      return;

    default:
      break;
    }

  /* Other cases: walk the insn.  */
  fmt = GET_RTX_FORMAT (code);
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    {
      if (fmt[i] == 'e')
        sched_analyze_2 (deps, XEXP (x, i), insn);
      else if (fmt[i] == 'E')
        for (j = 0; j < XVECLEN (x, i); j++)
          sched_analyze_2 (deps, XVECEXP (x, i, j), insn);
    }
}

/* Analyze an INSN with pattern X to find all dependencies.  */

static void
sched_analyze_insn (deps, x, insn, loop_notes)
     struct deps *deps;
     rtx x, insn;
     rtx loop_notes;
{
  register RTX_CODE code = GET_CODE (x);
  int schedule_barrier_found = 0;
  rtx link;
  int i;

  if (code == COND_EXEC)
    {
      sched_analyze_2 (deps, COND_EXEC_TEST (x), insn);

      /* ??? Should be recording conditions so we reduce the number of
         false dependancies.  */
      x = COND_EXEC_CODE (x);
      code = GET_CODE (x);
    }
  if (code == SET || code == CLOBBER)
    sched_analyze_1 (deps, x, insn);
  else if (code == PARALLEL)
    {
      register int i;
      for (i = XVECLEN (x, 0) - 1; i >= 0; i--)
        {
          rtx sub = XVECEXP (x, 0, i);
          code = GET_CODE (sub);

          if (code == COND_EXEC)
            {
              sched_analyze_2 (deps, COND_EXEC_TEST (sub), insn);
              sub = COND_EXEC_CODE (sub);
              code = GET_CODE (sub);
            }
          if (code == SET || code == CLOBBER)
            sched_analyze_1 (deps, sub, insn);
          else
            sched_analyze_2 (deps, sub, insn);
        }
    }
  else
    sched_analyze_2 (deps, x, insn);

  /* Mark registers CLOBBERED or used by called function.  */
  if (GET_CODE (insn) == CALL_INSN)
    for (link = CALL_INSN_FUNCTION_USAGE (insn); link; link = XEXP (link, 1))
      {
        if (GET_CODE (XEXP (link, 0)) == CLOBBER)
          sched_analyze_1 (deps, XEXP (link, 0), insn);
        else
          sched_analyze_2 (deps, XEXP (link, 0), insn);
      }

  if (GET_CODE (insn) == JUMP_INSN)
    {
      rtx next;
      next = next_nonnote_insn (insn);
      if (next && GET_CODE (next) == BARRIER)
        schedule_barrier_found = 1;
      else
        {
          rtx pending, pending_mem, u;
          regset_head tmp;
          INIT_REG_SET (&tmp);

          (*current_sched_info->compute_jump_reg_dependencies) (insn, &tmp);
          EXECUTE_IF_SET_IN_REG_SET (&tmp, 0, i,
            {
              struct deps_reg *reg_last = &deps->reg_last[i];
              for (u = reg_last->sets; u; u = XEXP (u, 1))
                add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);
              reg_last->uses = alloc_INSN_LIST (insn, reg_last->uses);
              SET_REGNO_REG_SET (&deps->reg_last_in_use, i);
            });

          CLEAR_REG_SET (&tmp);

          pending = deps->pending_write_insns;
          pending_mem = deps->pending_write_mems;
          while (pending)
            {
              add_dependence (insn, XEXP (pending, 0), REG_DEP_OUTPUT);

              pending = XEXP (pending, 1);
              pending_mem = XEXP (pending_mem, 1);
            }

          for (u = deps->last_pending_memory_flush; u; u = XEXP (u, 1))
            add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);
        }
    }

  /* If there is a {LOOP,EHREGION}_{BEG,END} note in the middle of a basic
     block, then we must be sure that no instructions are scheduled across it.
     Otherwise, the reg_n_refs info (which depends on loop_depth) would
     become incorrect.  */
  if (loop_notes)
    {
      rtx link;

      /* Update loop_notes with any notes from this insn.  Also determine
         if any of the notes on the list correspond to instruction scheduling
         barriers (loop, eh & setjmp notes, but not range notes).  */
      link = loop_notes;
      while (XEXP (link, 1))
        {
          if (INTVAL (XEXP (link, 0)) == NOTE_INSN_LOOP_BEG
              || INTVAL (XEXP (link, 0)) == NOTE_INSN_LOOP_END
              || INTVAL (XEXP (link, 0)) == NOTE_INSN_EH_REGION_BEG
              || INTVAL (XEXP (link, 0)) == NOTE_INSN_EH_REGION_END
              || INTVAL (XEXP (link, 0)) == NOTE_INSN_SETJMP)
            schedule_barrier_found = 1;

          link = XEXP (link, 1);
        }
      XEXP (link, 1) = REG_NOTES (insn);
      REG_NOTES (insn) = loop_notes;
    }

  /* If this instruction can throw an exception, then moving it changes
     where block boundaries fall.  This is mighty confusing elsewhere. 
     Therefore, prevent such an instruction from being moved.  */
  if (flag_non_call_exceptions && can_throw_internal (insn))
    schedule_barrier_found = 1;

  /* Add dependencies if a scheduling barrier was found.  */
  if (schedule_barrier_found)
    {
      rtx u, pending, pending_mem;

      for (i = 0; i < deps->max_reg; i++)
        {
          struct deps_reg *reg_last = &deps->reg_last[i];

          for (u = reg_last->uses; u; u = XEXP (u, 1))
            add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);
          for (u = reg_last->sets; u; u = XEXP (u, 1))
            add_dependence (insn, XEXP (u, 0), 0);
          for (u = reg_last->clobbers; u; u = XEXP (u, 1))
            add_dependence (insn, XEXP (u, 0), 0);

          if (GET_CODE (PATTERN (insn)) != COND_EXEC)
            free_INSN_LIST_list (&reg_last->uses);
        }
      flush_pending_lists (deps, insn, 0);

      pending = deps->pending_write_insns;
      pending_mem = deps->pending_write_mems;
      while (pending)
        {
          add_dependence (insn, XEXP (pending, 0), 0);
          pending = XEXP (pending, 1);
          pending_mem = XEXP (pending_mem, 1);
        }

      for (u = deps->last_pending_memory_flush; u; u = XEXP (u, 1))
        add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);

      reg_pending_sets_all = 1;
    }

  /* Accumulate clobbers until the next set so that it will be output
     dependent on all of them.  At the next set we can clear the clobber
     list, since subsequent sets will be output dependent on it.  */
  if (reg_pending_sets_all)
    {
      reg_pending_sets_all = 0;
      for (i = 0; i < deps->max_reg; i++)
        {
          struct deps_reg *reg_last = &deps->reg_last[i];
          if (GET_CODE (PATTERN (insn)) != COND_EXEC)
            {
              free_INSN_LIST_list (&reg_last->sets);
              free_INSN_LIST_list (&reg_last->clobbers);
            }
          reg_last->sets = alloc_INSN_LIST (insn, reg_last->sets);
          SET_REGNO_REG_SET (&deps->reg_last_in_use, i);
        }
    }
  else
    {
      EXECUTE_IF_SET_IN_REG_SET (reg_pending_sets, 0, i,
        {
          struct deps_reg *reg_last = &deps->reg_last[i];
          if (GET_CODE (PATTERN (insn)) != COND_EXEC)
            {
              free_INSN_LIST_list (&reg_last->sets);
              free_INSN_LIST_list (&reg_last->clobbers);
            }
          reg_last->sets = alloc_INSN_LIST (insn, reg_last->sets);
          SET_REGNO_REG_SET (&deps->reg_last_in_use, i);
        });
      EXECUTE_IF_SET_IN_REG_SET (reg_pending_clobbers, 0, i,
        {
          struct deps_reg *reg_last = &deps->reg_last[i];
          reg_last->clobbers = alloc_INSN_LIST (insn, reg_last->clobbers);
          SET_REGNO_REG_SET (&deps->reg_last_in_use, i);
        });
    }
  CLEAR_REG_SET (reg_pending_sets);
  CLEAR_REG_SET (reg_pending_clobbers);

  /* If a post-call group is still open, see if it should remain so.
     This insn must be a simple move of a hard reg to a pseudo or
     vice-versa.

     We must avoid moving these insns for correctness on
     SMALL_REGISTER_CLASS machines, and for special registers like
     PIC_OFFSET_TABLE_REGNUM.  For simplicity, extend this to all
     hard regs for all targets.  */

  if (deps->in_post_call_group_p)
    {
      rtx tmp, set = single_set (insn);
      int src_regno, dest_regno;

      if (set == NULL)
        goto end_call_group;

      tmp = SET_DEST (set);
      if (GET_CODE (tmp) == SUBREG)
        tmp = SUBREG_REG (tmp);
      if (GET_CODE (tmp) == REG)
        dest_regno = REGNO (tmp);
      else
        goto end_call_group;

      tmp = SET_SRC (set);
      if (GET_CODE (tmp) == SUBREG)
        tmp = SUBREG_REG (tmp);
      if (GET_CODE (tmp) == REG)
        src_regno = REGNO (tmp);
      else
        goto end_call_group;

      if (src_regno < FIRST_PSEUDO_REGISTER
          || dest_regno < FIRST_PSEUDO_REGISTER)
        {
          set_sched_group_p (insn);
          CANT_MOVE (insn) = 1;
        }
      else
        {
        end_call_group:
          deps->in_post_call_group_p = 0;
        }
    }
}

/* Analyze every insn between HEAD and TAIL inclusive, creating LOG_LINKS
   for every dependency.  */

void
sched_analyze (deps, head, tail)
     struct deps *deps;
     rtx head, tail;
{
  register rtx insn;
  register rtx u;
  rtx loop_notes = 0;

  for (insn = head;; insn = NEXT_INSN (insn))
    {
      if (GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN)
        {
          /* Clear out the stale LOG_LINKS from flow.  */
          free_INSN_LIST_list (&LOG_LINKS (insn));

          /* Clear out stale SCHED_GROUP_P.  */
          SCHED_GROUP_P (insn) = 0;

          /* Make each JUMP_INSN a scheduling barrier for memory
             references.  */
          if (GET_CODE (insn) == JUMP_INSN)
            deps->last_pending_memory_flush
              = alloc_INSN_LIST (insn, deps->last_pending_memory_flush);
          sched_analyze_insn (deps, PATTERN (insn), insn, loop_notes);
          loop_notes = 0;
        }
      else if (GET_CODE (insn) == CALL_INSN)
        {
          rtx x;
          register int i;

          /* Clear out stale SCHED_GROUP_P.  */
          SCHED_GROUP_P (insn) = 0;

          CANT_MOVE (insn) = 1;

          /* Clear out the stale LOG_LINKS from flow.  */
          free_INSN_LIST_list (&LOG_LINKS (insn));

          /* Any instruction using a hard register which may get clobbered
             by a call needs to be marked as dependent on this call.
             This prevents a use of a hard return reg from being moved
             past a void call (i.e. it does not explicitly set the hard
             return reg).  */

          /* If this call is followed by a NOTE_INSN_SETJMP, then assume that
             all registers, not just hard registers, may be clobbered by this
             call.  */

          /* Insn, being a CALL_INSN, magically depends on
             `last_function_call' already.  */

          if (NEXT_INSN (insn) && GET_CODE (NEXT_INSN (insn)) == NOTE
              && NOTE_LINE_NUMBER (NEXT_INSN (insn)) == NOTE_INSN_SETJMP)
            {
              for (i = 0; i < deps->max_reg; i++)
                {
                  struct deps_reg *reg_last = &deps->reg_last[i];
                
                  for (u = reg_last->uses; u; u = XEXP (u, 1))
                    add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);
                  for (u = reg_last->sets; u; u = XEXP (u, 1))
                    add_dependence (insn, XEXP (u, 0), 0);
                  for (u = reg_last->clobbers; u; u = XEXP (u, 1))
                    add_dependence (insn, XEXP (u, 0), 0);

                  free_INSN_LIST_list (&reg_last->uses);
                }
              reg_pending_sets_all = 1;

              /* Add a pair of REG_SAVE_NOTEs which we will later
                 convert back into a NOTE_INSN_SETJMP note.  See
                 reemit_notes for why we use a pair of NOTEs.  */
              REG_NOTES (insn) = alloc_EXPR_LIST (REG_SAVE_NOTE,
                                                  GEN_INT (0),
                                                  REG_NOTES (insn));
              REG_NOTES (insn) = alloc_EXPR_LIST (REG_SAVE_NOTE,
                                                  GEN_INT (NOTE_INSN_SETJMP),
                                                  REG_NOTES (insn));
            }
          else
            {
              for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
                if (call_used_regs[i] || global_regs[i])
                  {
                    for (u = deps->reg_last[i].uses; u; u = XEXP (u, 1))
                      add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);
                    for (u = deps->reg_last[i].sets; u; u = XEXP (u, 1))
                      add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);

                    SET_REGNO_REG_SET (reg_pending_clobbers, i);
                  }
            }

          /* For each insn which shouldn't cross a call, add a dependence
             between that insn and this call insn.  */
          x = LOG_LINKS (deps->sched_before_next_call);
          while (x)
            {
              add_dependence (insn, XEXP (x, 0), REG_DEP_ANTI);
              x = XEXP (x, 1);
            }
          free_INSN_LIST_list (&LOG_LINKS (deps->sched_before_next_call));

          sched_analyze_insn (deps, PATTERN (insn), insn, loop_notes);
          loop_notes = 0;

          /* In the absence of interprocedural alias analysis, we must flush
             all pending reads and writes, and start new dependencies starting
             from here.  But only flush writes for constant calls (which may
             be passed a pointer to something we haven't written yet).  */
          flush_pending_lists (deps, insn, CONST_CALL_P (insn));

          /* Depend this function call (actually, the user of this
             function call) on all hard register clobberage.  */

          /* last_function_call is now a list of insns.  */
          free_INSN_LIST_list (&deps->last_function_call);
          deps->last_function_call = alloc_INSN_LIST (insn, NULL_RTX);

          /* Before reload, begin a post-call group, so as to keep the
             lifetimes of hard registers correct.  */
          if (! reload_completed)
            deps->in_post_call_group_p = 1;
        }

      /* See comments on reemit_notes as to why we do this.
         ??? Actually, the reemit_notes just say what is done, not why.  */

      else if (GET_CODE (insn) == NOTE
               && (NOTE_LINE_NUMBER (insn) == NOTE_INSN_RANGE_BEG
                   || NOTE_LINE_NUMBER (insn) == NOTE_INSN_RANGE_END))
        {
          loop_notes = alloc_EXPR_LIST (REG_SAVE_NOTE, NOTE_RANGE_INFO (insn),
                                        loop_notes);
          loop_notes = alloc_EXPR_LIST (REG_SAVE_NOTE,
                                        GEN_INT (NOTE_LINE_NUMBER (insn)),
                                        loop_notes);
        }
      else if (GET_CODE (insn) == NOTE
               && (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG
                   || NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END
                   || NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG
                   || NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END
                   || (NOTE_LINE_NUMBER (insn) == NOTE_INSN_SETJMP
                       && GET_CODE (PREV_INSN (insn)) != CALL_INSN)))
        {
          rtx rtx_region;

          if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG
              || NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END)
            rtx_region = GEN_INT (NOTE_EH_HANDLER (insn));
          else
            rtx_region = GEN_INT (0);

          loop_notes = alloc_EXPR_LIST (REG_SAVE_NOTE,
                                        rtx_region,
                                        loop_notes);
          loop_notes = alloc_EXPR_LIST (REG_SAVE_NOTE,
                                        GEN_INT (NOTE_LINE_NUMBER (insn)),
                                        loop_notes);
          CONST_CALL_P (loop_notes) = CONST_CALL_P (insn);
        }

      if (insn == tail)
        return;
    }
  abort ();
}
\f
/* Examine insns in the range [ HEAD, TAIL ] and Use the backward
   dependences from LOG_LINKS to build forward dependences in
   INSN_DEPEND.  */

void
compute_forward_dependences (head, tail)
     rtx head, tail;
{
  rtx insn, link;
  rtx next_tail;
  enum reg_note dep_type;

  next_tail = NEXT_INSN (tail);
  for (insn = head; insn != next_tail; insn = NEXT_INSN (insn))
    {
      if (! INSN_P (insn))
        continue;

      insn = group_leader (insn);

      for (link = LOG_LINKS (insn); link; link = XEXP (link, 1))
        {
          rtx x = group_leader (XEXP (link, 0));
          rtx new_link;

          if (x != XEXP (link, 0))
            continue;

#ifdef ENABLE_CHECKING
          /* If add_dependence is working properly there should never
             be notes, deleted insns or duplicates in the backward
             links.  Thus we need not check for them here.

             However, if we have enabled checking we might as well go
             ahead and verify that add_dependence worked properly.  */
          if (GET_CODE (x) == NOTE
              || INSN_DELETED_P (x)
              || (forward_dependency_cache != NULL
                  && TEST_BIT (forward_dependency_cache[INSN_LUID (x)],
                               INSN_LUID (insn)))
              || (forward_dependency_cache == NULL
                  && find_insn_list (insn, INSN_DEPEND (x))))
            abort ();
          if (forward_dependency_cache != NULL)
            SET_BIT (forward_dependency_cache[INSN_LUID (x)],
                     INSN_LUID (insn));
#endif

          new_link = alloc_INSN_LIST (insn, INSN_DEPEND (x));

          dep_type = REG_NOTE_KIND (link);
          PUT_REG_NOTE_KIND (new_link, dep_type);

          INSN_DEPEND (x) = new_link;
          INSN_DEP_COUNT (insn) += 1;
        }
    }
}
\f
/* Initialize variables for region data dependence analysis.
   n_bbs is the number of region blocks.  */

void
init_deps (deps)
     struct deps *deps;
{
  int max_reg = (reload_completed ? FIRST_PSEUDO_REGISTER : max_reg_num ());

  deps->max_reg = max_reg;
  deps->reg_last = (struct deps_reg *)
    xcalloc (max_reg, sizeof (struct deps_reg));
  INIT_REG_SET (&deps->reg_last_in_use);

  deps->pending_read_insns = 0;
  deps->pending_read_mems = 0;
  deps->pending_write_insns = 0;
  deps->pending_write_mems = 0;
  deps->pending_lists_length = 0;
  deps->last_pending_memory_flush = 0;
  deps->last_function_call = 0;
  deps->in_post_call_group_p = 0;

  deps->sched_before_next_call
    = gen_rtx_INSN (VOIDmode, 0, NULL_RTX, NULL_RTX,
                    NULL_RTX, 0, NULL_RTX, NULL_RTX);
  LOG_LINKS (deps->sched_before_next_call) = 0;
}

/* Free insn lists found in DEPS.  */

void
free_deps (deps)
     struct deps *deps;
{
  int i;

  /* Without the EXECUTE_IF_SET, this loop is executed max_reg * nr_regions
     times.  For a test case with 42000 regs and 8000 small basic blocks,
     this loop accounted for nearly 60% (84 sec) of the total -O2 runtime.  */
  EXECUTE_IF_SET_IN_REG_SET (&deps->reg_last_in_use, 0, i,
    {
      struct deps_reg *reg_last = &deps->reg_last[i];
      free_INSN_LIST_list (&reg_last->uses);
      free_INSN_LIST_list (&reg_last->sets);
      free_INSN_LIST_list (&reg_last->clobbers);
    });
  CLEAR_REG_SET (&deps->reg_last_in_use);

  free (deps->reg_last);
  deps->reg_last = NULL;
}

/* If it is profitable to use them, initialize caches for tracking
   dependency informatino.  LUID is the number of insns to be scheduled,
   it is used in the estimate of profitability.  */

void
init_dependency_caches (luid)
     int luid;
{
  /* ?!? We could save some memory by computing a per-region luid mapping
     which could reduce both the number of vectors in the cache and the size
     of each vector.  Instead we just avoid the cache entirely unless the
     average number of instructions in a basic block is very high.  See
     the comment before the declaration of true_dependency_cache for
     what we consider "very high".  */
  if (luid / n_basic_blocks > 100 * 5)
    {
      true_dependency_cache = sbitmap_vector_alloc (luid, luid);
      sbitmap_vector_zero (true_dependency_cache, luid);
      anti_dependency_cache = sbitmap_vector_alloc (luid, luid);
      sbitmap_vector_zero (anti_dependency_cache, luid);
      output_dependency_cache = sbitmap_vector_alloc (luid, luid);
      sbitmap_vector_zero (output_dependency_cache, luid);
#ifdef ENABLE_CHECKING
      forward_dependency_cache = sbitmap_vector_alloc (luid, luid);
      sbitmap_vector_zero (forward_dependency_cache, luid);
#endif
    }
}

/* Free the caches allocated in init_dependency_caches.  */

void
free_dependency_caches ()
{
  if (true_dependency_cache)
    {
      free (true_dependency_cache);
      true_dependency_cache = NULL;
      free (anti_dependency_cache);
      anti_dependency_cache = NULL;
      free (output_dependency_cache);
      output_dependency_cache = NULL;
#ifdef ENABLE_CHECKING
      free (forward_dependency_cache);
      forward_dependency_cache = NULL;
#endif
    }
}

/* Initialize some global variables needed by the dependency analysis
   code.  */

void
init_deps_global ()
{
  reg_pending_sets = INITIALIZE_REG_SET (reg_pending_sets_head);
  reg_pending_clobbers = INITIALIZE_REG_SET (reg_pending_clobbers_head);
  reg_pending_sets_all = 0;
}

/* Free everything used by the dependency analysis code.  */

void
finish_deps_global ()
{
  FREE_REG_SET (reg_pending_sets);
  FREE_REG_SET (reg_pending_clobbers);
}