2001-05-28 Philip Blundell <philb@gnu.org>

[binutils.git] / gprof / cg_print.c

/* cg_print.c -  Print routines for displaying call graphs.

   Copyright (C) 2000  Free Software Foundation, Inc.

   This file is part of GNU Binutils.

   This program 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 of the License, or
   (at your option) any later version.

   This program 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 this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
   02111-1307, USA.  */
\f
#include "libiberty.h"
#include "cg_arcs.h"
#include "cg_print.h"
#include "hist.h"
#include "utils.h"

/* Return value of comparison functions used to sort tables.  */
#define LESSTHAN        -1
#define EQUALTO         0
#define GREATERTHAN     1

static void order_and_dump_functions_by_arcs PARAMS ((Arc **, unsigned long,
                                                      int, Arc **,
                                                      unsigned long *));
/* Declarations of automatically generated functions to output blurbs.  */
extern void bsd_callg_blurb PARAMS ((FILE * fp));
extern void fsf_callg_blurb PARAMS ((FILE * fp));

double print_time = 0.0;


static void
DEFUN_VOID (print_header)
{
  if (first_output)
    first_output = FALSE;
  else
    printf ("\f\n");
  
  if (!bsd_style_output)
    {
      if (print_descriptions)
        printf (_("\t\t     Call graph (explanation follows)\n\n"));
      else
        printf (_("\t\t\tCall graph\n\n"));
    }
  
  printf (_("\ngranularity: each sample hit covers %ld byte(s)"),
          (long) hist_scale * sizeof (UNIT));
  
  if (print_time > 0.0)
    printf (_(" for %.2f%% of %.2f seconds\n\n"),
            100.0 / print_time, print_time / hz);
  else
    {
      printf (_(" no time propagated\n\n"));
      
      /* This doesn't hurt, since all the numerators will be 0.0.  */
      print_time = 1.0;
    }
  
  if (bsd_style_output)
    {
      printf ("%6.6s %5.5s %7.7s %11.11s %7.7s/%-7.7s     %-8.8s\n",
              "", "", "", "", _("called"), _("total"), _("parents"));
      printf ("%-6.6s %5.5s %7.7s %11.11s %7.7s+%-7.7s %-8.8s\t%5.5s\n",
              _("index"), _("%time"), _("self"), _("descendents"),
              _("called"), _("self"), _("name"), _("index"));
      printf ("%6.6s %5.5s %7.7s %11.11s %7.7s/%-7.7s     %-8.8s\n",
              "", "", "", "", _("called"), _("total"), _("children"));
      printf ("\n");
    }
  else
    {
      printf (_("index %% time    self  children    called     name\n"));
    }
}

/* Print a cycle header.  */

static void
DEFUN (print_cycle, (cyc), Sym * cyc)
{
  char buf[BUFSIZ];

  sprintf (buf, "[%d]", cyc->cg.index);
  printf (bsd_style_output
          ? "%-6.6s %5.1f %7.2f %11.2f %7lu"
          : "%-6.6s %5.1f %7.2f %7.2f %7lu", buf,
          100 * (cyc->cg.prop.self + cyc->cg.prop.child) / print_time,
          cyc->cg.prop.self / hz, cyc->cg.prop.child / hz, cyc->ncalls);
  
  if (cyc->cg.self_calls != 0)
    printf ("+%-7lu", cyc->cg.self_calls);
  else
    printf (" %7.7s", "");

  printf (_(" <cycle %d as a whole> [%d]\n"), cyc->cg.cyc.num, cyc->cg.index);
}

/* Compare LEFT and RIGHT membmer.  Major comparison key is
   CG.PROP.SELF+CG.PROP.CHILD, secondary key is NCALLS+CG.SELF_CALLS.  */

static int
DEFUN (cmp_member, (left, right), Sym * left AND Sym * right)
{
  double left_time = left->cg.prop.self + left->cg.prop.child;
  double right_time = right->cg.prop.self + right->cg.prop.child;
  unsigned long left_calls = left->ncalls + left->cg.self_calls;
  unsigned long right_calls = right->ncalls + right->cg.self_calls;

  if (left_time > right_time)
    return GREATERTHAN;

  if (left_time < right_time)
    return LESSTHAN;

  if (left_calls > right_calls)
    return GREATERTHAN;

  if (left_calls < right_calls)
    return LESSTHAN;

  return EQUALTO;
}

/* Sort members of a cycle.  */

static void
DEFUN (sort_members, (cyc), Sym * cyc)
{
  Sym *todo, *doing, *prev;
  
  /* Detach cycle members from cyclehead,
     and insertion sort them back on.  */
  todo = cyc->cg.cyc.next;
  cyc->cg.cyc.next = 0;
  
  for (doing = todo; doing && doing->cg.cyc.next; doing = todo)
    {
      todo = doing->cg.cyc.next;
      
      for (prev = cyc; prev->cg.cyc.next; prev = prev->cg.cyc.next)
        {
          if (cmp_member (doing, prev->cg.cyc.next) == GREATERTHAN)
            break;
        }
      
      doing->cg.cyc.next = prev->cg.cyc.next;
      prev->cg.cyc.next = doing;
    }
}

/* Print the members of a cycle.  */

static void
DEFUN (print_members, (cyc), Sym * cyc)
{
  Sym *member;

  sort_members (cyc);
  
  for (member = cyc->cg.cyc.next; member; member = member->cg.cyc.next)
    {
      printf (bsd_style_output
              ? "%6.6s %5.5s %7.2f %11.2f %7lu"
              : "%6.6s %5.5s %7.2f %7.2f %7lu",
              "", "", member->cg.prop.self / hz, member->cg.prop.child / hz,
              member->ncalls);
      
      if (member->cg.self_calls != 0)
        printf ("+%-7lu", member->cg.self_calls);
      else
        printf (" %7.7s", "");

      printf ("     ");
      print_name (member);
      printf ("\n");
    }
}

/* Compare two arcs to/from the same child/parent.
        - if one arc is a self arc, it's least.
        - if one arc is within a cycle, it's less than.
        - if both arcs are within a cycle, compare arc counts.
        - if neither arc is within a cycle, compare with
                time + child_time as major key
                arc count as minor key.  */

static int
DEFUN (cmp_arc, (left, right), Arc * left AND Arc * right)
{
  Sym *left_parent = left->parent;
  Sym *left_child = left->child;
  Sym *right_parent = right->parent;
  Sym *right_child = right->child;
  double left_time, right_time;

  DBG (TIMEDEBUG,
       printf ("[cmp_arc] ");
       print_name (left_parent);
       printf (" calls ");
       print_name (left_child);
       printf (" %f + %f %lu/%lu\n", left->time, left->child_time,
               left->count, left_child->ncalls);
       printf ("[cmp_arc] ");
       print_name (right_parent);
       printf (" calls ");
       print_name (right_child);
       printf (" %f + %f %lu/%lu\n", right->time, right->child_time,
               right->count, right_child->ncalls);
       printf ("\n");
    );
  
  if (left_parent == left_child)
    return LESSTHAN;            /* Left is a self call.  */

  if (right_parent == right_child)
    return GREATERTHAN;         /* Right is a self call.  */

  if (left_parent->cg.cyc.num != 0 && left_child->cg.cyc.num != 0
      && left_parent->cg.cyc.num == left_child->cg.cyc.num)
    {
      /* Left is a call within a cycle.  */
      if (right_parent->cg.cyc.num != 0 && right_child->cg.cyc.num != 0
          && right_parent->cg.cyc.num == right_child->cg.cyc.num)
        {
          /* Right is a call within the cycle, too.  */
          if (left->count < right->count)
            return LESSTHAN;

          if (left->count > right->count)
            return GREATERTHAN;

          return EQUALTO;
        }
      else
        {
          /* Right isn't a call within the cycle.  */
          return LESSTHAN;
        }
    }
  else
    {
      /* Left isn't a call within a cycle.  */
      if (right_parent->cg.cyc.num != 0 && right_child->cg.cyc.num != 0
          && right_parent->cg.cyc.num == right_child->cg.cyc.num)
        {
          /* Right is a call within a cycle.  */
          return GREATERTHAN;
        }
      else
        {
          /* Neither is a call within a cycle.  */
          left_time = left->time + left->child_time;
          right_time = right->time + right->child_time;
          
          if (left_time < right_time)
            return LESSTHAN;

          if (left_time > right_time)
            return GREATERTHAN;

          if (left->count < right->count)
            return LESSTHAN;

          if (left->count > right->count)
            return GREATERTHAN;

          return EQUALTO;
        }
    }
}


static void
DEFUN (sort_parents, (child), Sym * child)
{
  Arc *arc, *detached, sorted, *prev;

  /* Unlink parents from child, then insertion sort back on to
     sorted's parents.
          *arc        the arc you have detached and are inserting.
          *detached   the rest of the arcs to be sorted.
          sorted      arc list onto which you insertion sort.
          *prev       arc before the arc you are comparing.  */
  sorted.next_parent = 0;
  
  for (arc = child->cg.parents; arc; arc = detached)
    {
      detached = arc->next_parent;

      /* Consider *arc as disconnected; insert it into sorted.  */
      for (prev = &sorted; prev->next_parent; prev = prev->next_parent)
        {
          if (cmp_arc (arc, prev->next_parent) != GREATERTHAN)
            break;
        }
      
      arc->next_parent = prev->next_parent;
      prev->next_parent = arc;
    }

  /* Reattach sorted arcs to child.  */
  child->cg.parents = sorted.next_parent;
}


static void
DEFUN (print_parents, (child), Sym * child)
{
  Sym *parent;
  Arc *arc;
  Sym *cycle_head;

  if (child->cg.cyc.head != 0)
    cycle_head = child->cg.cyc.head;
  else
    cycle_head = child;
  
  if (!child->cg.parents)
    {
      printf (bsd_style_output
              ? _("%6.6s %5.5s %7.7s %11.11s %7.7s %7.7s     <spontaneous>\n")
              : _("%6.6s %5.5s %7.7s %7.7s %7.7s %7.7s     <spontaneous>\n"),
              "", "", "", "", "", "");
      return;
    }
  
  sort_parents (child);
  
  for (arc = child->cg.parents; arc; arc = arc->next_parent)
    {
      parent = arc->parent;
      if (child == parent || (child->cg.cyc.num != 0
                              && parent->cg.cyc.num == child->cg.cyc.num))
        {
          /* Selfcall or call among siblings.  */
          printf (bsd_style_output
                  ? "%6.6s %5.5s %7.7s %11.11s %7lu %7.7s     "
                  : "%6.6s %5.5s %7.7s %7.7s %7lu %7.7s     ",
                  "", "", "", "",
                  arc->count, "");
          print_name (parent);
          printf ("\n");
        }
      else
        {
          /* Regular parent of child.  */
          printf (bsd_style_output
                  ? "%6.6s %5.5s %7.2f %11.2f %7lu/%-7lu     "
                  : "%6.6s %5.5s %7.2f %7.2f %7lu/%-7lu     ",
                  "", "",
                  arc->time / hz, arc->child_time / hz,
                  arc->count, cycle_head->ncalls);
          print_name (parent);
          printf ("\n");
        }
    }
}


static void
DEFUN (sort_children, (parent), Sym * parent)
{
  Arc *arc, *detached, sorted, *prev;
  
  /* Unlink children from parent, then insertion sort back on to
     sorted's children.
          *arc        the arc you have detached and are inserting.
          *detached   the rest of the arcs to be sorted.
          sorted      arc list onto which you insertion sort.
          *prev       arc before the arc you are comparing.  */
  sorted.next_child = 0;
  
  for (arc = parent->cg.children; arc; arc = detached)
    {
      detached = arc->next_child;

      /* Consider *arc as disconnected; insert it into sorted.  */
      for (prev = &sorted; prev->next_child; prev = prev->next_child)
        {
          if (cmp_arc (arc, prev->next_child) != LESSTHAN)
            break;
        }
      
      arc->next_child = prev->next_child;
      prev->next_child = arc;
    }

  /* Reattach sorted children to parent.  */
  parent->cg.children = sorted.next_child;
}


static void
DEFUN (print_children, (parent), Sym * parent)
{
  Sym *child;
  Arc *arc;

  sort_children (parent);
  arc = parent->cg.children;
  
  for (arc = parent->cg.children; arc; arc = arc->next_child)
    {
      child = arc->child;
      if (child == parent || (child->cg.cyc.num != 0
                              && child->cg.cyc.num == parent->cg.cyc.num))
        {
          /* Self call or call to sibling.  */
          printf (bsd_style_output
                  ? "%6.6s %5.5s %7.7s %11.11s %7lu %7.7s     "
                  : "%6.6s %5.5s %7.7s %7.7s %7lu %7.7s     ",
                  "", "", "", "", arc->count, "");
          print_name (child);
          printf ("\n");
        }
      else
        {
          /* Regular child of parent.  */
          printf (bsd_style_output
                  ? "%6.6s %5.5s %7.2f %11.2f %7lu/%-7lu     "
                  : "%6.6s %5.5s %7.2f %7.2f %7lu/%-7lu     ",
                  "", "",
                  arc->time / hz, arc->child_time / hz,
                  arc->count, child->cg.cyc.head->ncalls);
          print_name (child);
          printf ("\n");
        }
    }
}


static void
DEFUN (print_line, (np), Sym * np)
{
  char buf[BUFSIZ];

  sprintf (buf, "[%d]", np->cg.index);
  printf (bsd_style_output
          ? "%-6.6s %5.1f %7.2f %11.2f"
          : "%-6.6s %5.1f %7.2f %7.2f", buf,
          100 * (np->cg.prop.self + np->cg.prop.child) / print_time,
          np->cg.prop.self / hz, np->cg.prop.child / hz);
  
  if ((np->ncalls + np->cg.self_calls) != 0)
    {
      printf (" %7lu", np->ncalls);
      
      if (np->cg.self_calls != 0)
          printf ("+%-7lu ", np->cg.self_calls);
      else
          printf (" %7.7s ", "");
    }
  else
    {
      printf (" %7.7s %7.7s ", "", "");
    }
  
  print_name (np);
  printf ("\n");
}


/* Print dynamic call graph.  */

void
DEFUN (cg_print, (timesortsym), Sym ** timesortsym)
{
  unsigned int index;
  Sym *parent;

  if (print_descriptions && bsd_style_output)
    bsd_callg_blurb (stdout);

  print_header ();

  for (index = 0; index < symtab.len + num_cycles; ++index)
    {
      parent = timesortsym[index];
      
      if ((ignore_zeros && parent->ncalls == 0
           && parent->cg.self_calls == 0 && parent->cg.prop.self == 0
           && parent->cg.prop.child == 0)
          || !parent->cg.print_flag
          || (line_granularity && ! parent->is_func))
        continue;
      
      if (!parent->name && parent->cg.cyc.num != 0)
        {
          /* Cycle header.  */
          print_cycle (parent);
          print_members (parent);
        }
      else
        {
          print_parents (parent);
          print_line (parent);
          print_children (parent);
        }
      
      if (bsd_style_output)
        printf ("\n");
      
      printf ("-----------------------------------------------\n");
      
      if (bsd_style_output)
        printf ("\n");
    }
  
  free (timesortsym);
  
  if (print_descriptions && !bsd_style_output)
    fsf_callg_blurb (stdout);
}


static int
DEFUN (cmp_name, (left, right), const PTR left AND const PTR right)
{
  const Sym **npp1 = (const Sym **) left;
  const Sym **npp2 = (const Sym **) right;

  return strcmp ((*npp1)->name, (*npp2)->name);
}


void
DEFUN_VOID (cg_print_index)
{
  unsigned int index;
  unsigned int nnames, todo, i, j;
  int col, starting_col;
  Sym **name_sorted_syms, *sym;
  const char *filename;
  char buf[20];
  int column_width = (output_width - 1) / 3;    /* Don't write in last col!  */
  
  /* Now, sort regular function name
     alphabetically to create an index.  */
  name_sorted_syms = (Sym **) xmalloc ((symtab.len + num_cycles) * sizeof (Sym *));
  
  for (index = 0, nnames = 0; index < symtab.len; index++)
    {
      if (ignore_zeros && symtab.base[index].ncalls == 0
          && symtab.base[index].hist.time == 0)
        continue;

      name_sorted_syms[nnames++] = &symtab.base[index];
    }
  
  qsort (name_sorted_syms, nnames, sizeof (Sym *), cmp_name);
  
  for (index = 1, todo = nnames; index <= num_cycles; index++)
    name_sorted_syms[todo++] = &cycle_header[index];

  printf ("\f\n");
  printf (_("Index by function name\n\n"));
  index = (todo + 2) / 3;
  
  for (i = 0; i < index; i++)
    {
      col = 0;
      starting_col = 0;
      
      for (j = i; j < todo; j += index)
        {
          sym = name_sorted_syms[j];
          
          if (sym->cg.print_flag)
            sprintf (buf, "[%d]", sym->cg.index);
          else
            sprintf (buf, "(%d)", sym->cg.index);

          if (j < nnames)
            {
              if (bsd_style_output)
                {
                  printf ("%6.6s %-19.19s", buf, sym->name);
                }
              else
                {
                  col += strlen (buf);
                  
                  for (; col < starting_col + 5; ++col)
                    putchar (' ');

                  printf (" %s ", buf);
                  col += print_name_only (sym);
                  
                  if (!line_granularity && sym->is_static && sym->file)
                    {
                      filename = sym->file->name;
                      
                      if (!print_path)
                        {
                          filename = strrchr (filename, '/');
                          
                          if (filename)
                            ++filename;
                          else
                            filename = sym->file->name;
                        }
                      
                      printf (" (%s)", filename);
                      col += strlen (filename) + 3;
                    }
                }
            }
          else
            {
              if (bsd_style_output)
                {
                  printf ("%6.6s ", buf);
                  sprintf (buf, _("<cycle %d>"), sym->cg.cyc.num);
                  printf ("%-19.19s", buf);
                }
              else
                {
                  col += strlen (buf);
                  for (; col < starting_col + 5; ++col)
                    putchar (' ');
                  printf (" %s ", buf);
                  sprintf (buf, _("<cycle %d>"), sym->cg.cyc.num);
                  printf ("%s", buf);
                  col += strlen (buf);
                }
            }
          
          starting_col += column_width;
        }
      
      printf ("\n");
    }
  
  free (name_sorted_syms);
}

/* Compare two arcs based on their usage counts.
   We want to sort in descending order.  */

static int
DEFUN (cmp_arc_count, (left, right), const PTR left AND const PTR right)
{
  const Arc **npp1 = (const Arc **) left;
  const Arc **npp2 = (const Arc **) right;

  if ((*npp1)->count > (*npp2)->count)
    return -1;
  else if ((*npp1)->count < (*npp2)->count)
    return 1;
  else
    return 0;
}

/* Compare two funtions based on their usage counts.
   We want to sort in descending order.  */

static int
DEFUN (cmp_fun_nuses, (left, right), const PTR left AND const PTR right)
{
  const Sym **npp1 = (const Sym **) left;
  const Sym **npp2 = (const Sym **) right;

  if ((*npp1)->nuses > (*npp2)->nuses)
    return -1;
  else if ((*npp1)->nuses < (*npp2)->nuses)
    return 1;
  else
    return 0;
}

/* Print a suggested function ordering based on the profiling data.

   We perform 4 major steps when ordering functions:

        * Group unused functions together and place them at the
        end of the function order.

        * Search the highest use arcs (those which account for 90% of
        the total arc count) for functions which have several parents.

        Group those with the most call sites together (currently the
        top 1.25% which have at least five different call sites).

        These are emitted at the start of the function order.

        * Use a greedy placement algorithm to place functions which
        occur in the top 99% of the arcs in the profile.  Some provisions
        are made to handle high usage arcs where the parent and/or
        child has already been placed.

        * Run the same greedy placement algorithm on the remaining
        arcs to place the leftover functions.


   The various "magic numbers" should (one day) be tuneable by command
   line options.  They were arrived at by benchmarking a few applications
   with various values to see which values produced better overall function
   orderings.

   Of course, profiling errors, machine limitations (PA long calls), and
   poor cutoff values for the placement algorithm may limit the usefullness
   of the resulting function order.  Improvements would be greatly appreciated.
   
   Suggestions:

        * Place the functions with many callers near the middle of the
        list to reduce long calls.

        * Propagate arc usage changes as functions are placed.  Ie if
        func1 and func2 are placed together, arcs to/from those arcs
        to the same parent/child should be combined, then resort the
        arcs to choose the next one.

        * Implement some global positioning algorithm to place the
        chains made by the greedy local positioning algorithm.  Probably
        by examining arcs which haven't been placed yet to tie two
        chains together.

        * Take a function's size and time into account in the algorithm;
        size in particular is important on the PA (long calls).  Placing
        many small functions onto their own page may be wise.

        * Use better profiling information; many published algorithms
        are based on call sequences through time, rather than just
        arc counts.

        * Prodecure cloning could improve performance when a small number
        of arcs account for most of the calls to a particular function.

        * Use relocation information to avoid moving unused functions
        completely out of the code stream; this would avoid severe lossage
        when the profile data bears little resemblance to actual runs.

        * Propagation of arc usages should also improve .o link line
        ordering which shares the same arc placement algorithm with
        the function ordering code (in fact it is a degenerate case
        of function ordering).  */
        
void
DEFUN_VOID (cg_print_function_ordering)
{
  unsigned long index, used, unused, scratch_index;
  unsigned long  unplaced_arc_count, high_arc_count, scratch_arc_count;
#ifdef __GNUC__
  unsigned long long total_arcs, tmp_arcs_count;
#else
  unsigned long total_arcs, tmp_arcs_count;
#endif
  Sym **unused_syms, **used_syms, **scratch_syms;
  Arc **unplaced_arcs, **high_arcs, **scratch_arcs;

  index = 0;
  used = 0;
  unused = 0;
  scratch_index = 0;
  unplaced_arc_count = 0;
  high_arc_count = 0;
  scratch_arc_count = 0;

  /* First group all the unused functions together.  */
  unused_syms = (Sym **) xmalloc (symtab.len * sizeof (Sym *));
  used_syms = (Sym **) xmalloc (symtab.len * sizeof (Sym *));
  scratch_syms = (Sym **) xmalloc (symtab.len * sizeof (Sym *));
  high_arcs = (Arc **) xmalloc (numarcs * sizeof (Arc *));
  scratch_arcs = (Arc **) xmalloc (numarcs * sizeof (Arc *));
  unplaced_arcs = (Arc **) xmalloc (numarcs * sizeof (Arc *));

  /* Walk through all the functions; mark those which are never
     called as placed (we'll emit them as a group later).  */
  for (index = 0, used = 0, unused = 0; index < symtab.len; index++)
    {
      if (symtab.base[index].ncalls == 0)
        {
          /* Filter out gprof generated names.  */
          if (strcmp (symtab.base[index].name, "<locore>")
              && strcmp (symtab.base[index].name, "<hicore>"))
            {
              unused_syms[unused++] = &symtab.base[index];
              symtab.base[index].has_been_placed = 1;
            }
        }
      else
        {
          used_syms[used++] = &symtab.base[index];
          symtab.base[index].has_been_placed = 0;
          symtab.base[index].next = 0;
          symtab.base[index].prev = 0;
          symtab.base[index].nuses = 0;
        }
    }

  /* Sort the arcs from most used to least used.  */
  qsort (arcs, numarcs, sizeof (Arc *), cmp_arc_count);

  /* Compute the total arc count.  Also mark arcs as unplaced.

     Note we don't compensate for overflow if that happens!
     Overflow is much less likely when this file is compiled
     with GCC as it can double-wide integers via long long.  */
  total_arcs = 0;
  for (index = 0; index < numarcs; index++)
    {
      total_arcs += arcs[index]->count;
      arcs[index]->has_been_placed = 0;
    }

  /* We want to pull out those functions which are referenced
     by many highly used arcs and emit them as a group.  This
     could probably use some tuning.  */
  tmp_arcs_count = 0;
  for (index = 0; index < numarcs; index++)
    {
      tmp_arcs_count += arcs[index]->count;

      /* Count how many times each parent and child are used up
         to our threshhold of arcs (90%).  */
      if ((double)tmp_arcs_count / (double)total_arcs > 0.90)
        break;

      arcs[index]->child->nuses++;
    }

  /* Now sort a temporary symbol table based on the number of
     times each function was used in the highest used arcs.  */
  memcpy (scratch_syms, used_syms, used * sizeof (Sym *));
  qsort (scratch_syms, used, sizeof (Sym *), cmp_fun_nuses);

  /* Now pick out those symbols we're going to emit as
     a group.  We take up to 1.25% of the used symbols.  */
  for (index = 0; index < used / 80; index++)
    {
      Sym *sym = scratch_syms[index];
      Arc *arc;

      /* If we hit symbols that aren't used from many call sites,
         then we can quit.  We choose five as the low limit for
         no particular reason.  */
      if (sym->nuses == 5)
        break;

      /* We're going to need the arcs between these functions.
         Unfortunately, we don't know all these functions
         until we're done.  So we keep track of all the arcs
         to the functions we care about, then prune out those
         which are uninteresting. 

         An interesting variation would be to quit when we found
         multi-call site functions which account for some percentage
         of the arcs.  */
      arc = sym->cg.children;
      
      while (arc)
        {
          if (arc->parent != arc->child)
            scratch_arcs[scratch_arc_count++] = arc;
          arc->has_been_placed = 1;
          arc = arc->next_child;
        }

      arc = sym->cg.parents;
      
      while (arc)
        {
          if (arc->parent != arc->child)
            scratch_arcs[scratch_arc_count++] = arc;
          arc->has_been_placed = 1;
          arc = arc->next_parent;
        }

      /* Keep track of how many symbols we're going to place.  */
      scratch_index = index;

      /* A lie, but it makes identifying
         these functions easier later.  */
      sym->has_been_placed = 1;
    }

  /* Now walk through the temporary arcs and copy
     those we care about into the high arcs array.  */
  for (index = 0; index < scratch_arc_count; index++)
    {
      Arc *arc = scratch_arcs[index];

      /* If this arc refers to highly used functions, then
         then we want to keep it.  */
      if (arc->child->has_been_placed
          && arc->parent->has_been_placed)
        {
          high_arcs[high_arc_count++] = scratch_arcs[index];

          /* We need to turn of has_been_placed since we're going to
             use the main arc placement algorithm on these arcs.  */
          arc->child->has_been_placed = 0;
          arc->parent->has_been_placed = 0;
        }
    }

  /* Dump the multi-site high usage functions which are not
     going to be ordered by the main ordering algorithm.  */
  for (index = 0; index < scratch_index; index++)
    {
      if (scratch_syms[index]->has_been_placed)
        printf ("%s\n", scratch_syms[index]->name);
    }

  /* Now we can order the multi-site high use
     functions based on the arcs between them.  */
  qsort (high_arcs, high_arc_count, sizeof (Arc *), cmp_arc_count);
  order_and_dump_functions_by_arcs (high_arcs, high_arc_count, 1,
                                    unplaced_arcs, &unplaced_arc_count);

  /* Order and dump the high use functions left,
     these typically have only a few call sites.  */
  order_and_dump_functions_by_arcs (arcs, numarcs, 0,
                                    unplaced_arcs, &unplaced_arc_count);

  /* Now place the rarely used functions.  */
  order_and_dump_functions_by_arcs (unplaced_arcs, unplaced_arc_count, 1,
                                    scratch_arcs, &scratch_arc_count);

  /* Output any functions not emitted by the order_and_dump calls.  */
  for (index = 0; index < used; index++)
    if (used_syms[index]->has_been_placed == 0)
      printf("%s\n", used_syms[index]->name);

  /* Output the unused functions.  */
  for (index = 0; index < unused; index++)
    printf("%s\n", unused_syms[index]->name);

  unused_syms = (Sym **) xmalloc (symtab.len * sizeof (Sym *));
  used_syms = (Sym **) xmalloc (symtab.len * sizeof (Sym *));
  scratch_syms = (Sym **) xmalloc (symtab.len * sizeof (Sym *));
  high_arcs = (Arc **) xmalloc (numarcs * sizeof (Arc *));
  scratch_arcs = (Arc **) xmalloc (numarcs * sizeof (Arc *));
  unplaced_arcs = (Arc **) xmalloc (numarcs * sizeof (Arc *));

  free (unused_syms);
  free (used_syms);
  free (scratch_syms);
  free (high_arcs);
  free (scratch_arcs);
  free (unplaced_arcs);
}

/* Place functions based on the arcs in ARCS with NUMARCS entries;
   place unused arcs into UNPLACED_ARCS/UNPLACED_ARC_COUNT.

   If ALL is nonzero, then place all functions referenced by ARCS,
   else only place those referenced in the top 99% of the arcs in ARCS.  */

#define MOST 0.99
static void
order_and_dump_functions_by_arcs (arcs, numarcs, all,
                                  unplaced_arcs, unplaced_arc_count)
     Arc **arcs;
     unsigned long numarcs;
     int all;
     Arc **unplaced_arcs;
     unsigned long *unplaced_arc_count;
{
#ifdef __GNUC__
  unsigned long long tmp_arcs, total_arcs;
#else
  unsigned long tmp_arcs, total_arcs;
#endif
  unsigned int index;

  /* If needed, compute the total arc count.

     Note we don't compensate for overflow if that happens!  */
  if (! all)
    {
      total_arcs = 0;
      for (index = 0; index < numarcs; index++)
        total_arcs += arcs[index]->count;
    }
  else
    total_arcs = 0;

  tmp_arcs = 0;
  
  for (index = 0; index < numarcs; index++)
    {
      Sym *sym1, *sym2;
      Sym *child, *parent;

      tmp_arcs += arcs[index]->count;

      /* Ignore this arc if it's already been placed.  */
      if (arcs[index]->has_been_placed)
        continue;

      child = arcs[index]->child;
      parent = arcs[index]->parent;

      /* If we're not using all arcs, and this is a rarely used
         arc, then put it on the unplaced_arc list.  Similarly
         if both the parent and child of this arc have been placed.  */
      if ((! all && (double)tmp_arcs / (double)total_arcs > MOST)
          || child->has_been_placed || parent->has_been_placed)
        {
          unplaced_arcs[(*unplaced_arc_count)++] = arcs[index];
          continue;
        }

      /* If all slots in the parent and child are full, then there isn't
         anything we can do right now.  We'll place this arc on the
         unplaced arc list in the hope that a global positioning
         algorithm can use it to place function chains.  */
      if (parent->next && parent->prev && child->next && child->prev)
        {
          unplaced_arcs[(*unplaced_arc_count)++] = arcs[index];
          continue;
        }

      /* If the parent is unattached, then find the closest
         place to attach it onto child's chain.   Similarly
         for the opposite case.  */
      if (!parent->next && !parent->prev)
        {
          int next_count = 0;
          int prev_count = 0;
          Sym *prev = child;
          Sym *next = child;

          /* Walk to the beginning and end of the child's chain.  */
          while (next->next)
            {
              next = next->next;
              next_count++;
            }

          while (prev->prev)
            {
              prev = prev->prev;
              prev_count++;
            }
          
          /* Choose the closest.  */
          child = next_count < prev_count ? next : prev;
        }
      else if (! child->next && !child->prev)
        {
          int next_count = 0;
          int prev_count = 0;
          Sym *prev = parent;
          Sym *next = parent;

          while (next->next)
            {
              next = next->next;
              next_count++;
            }

          while (prev->prev)
            {
              prev = prev->prev;
              prev_count++;
            }

          parent = prev_count < next_count ? prev : next;
        }
      else
        {
          /* Couldn't find anywhere to attach the functions,
             put the arc on the unplaced arc list.  */
          unplaced_arcs[(*unplaced_arc_count)++] = arcs[index];
          continue;
        }

      /* Make sure we don't tie two ends together.  */
      sym1 = parent;
      if (sym1->next)
        while (sym1->next)
          sym1 = sym1->next;
      else
        while (sym1->prev)
          sym1 = sym1->prev;

      sym2 = child;
      if (sym2->next)
        while (sym2->next)
          sym2 = sym2->next;
      else
        while (sym2->prev)
          sym2 = sym2->prev;

      if (sym1 == child
          && sym2 == parent)
        {
          /* This would tie two ends together.  */
          unplaced_arcs[(*unplaced_arc_count)++] = arcs[index];
          continue;
        }

      if (parent->next)
        {
          /* Must attach to the parent's prev field.  */
          if (! child->next)
            {
              /* parent-prev and child-next */
              parent->prev = child;
              child->next = parent;
              arcs[index]->has_been_placed = 1;
            }
        }
      else if (parent->prev)
        {
          /* Must attach to the parent's next field.  */
          if (! child->prev)
            {
              /* parent-next and child-prev */
              parent->next = child;
              child->prev = parent;
              arcs[index]->has_been_placed = 1;
            }
        }
      else
        {
          /* Can attach to either field in the parent, depends
             on where we've got space in the child.  */
          if (child->prev)
            {
              /* parent-prev and child-next.  */
              parent->prev = child;
              child->next = parent;
              arcs[index]->has_been_placed = 1;
            }
          else
            {
              /* parent-next and child-prev.  */
              parent->next = child;
              child->prev = parent;
              arcs[index]->has_been_placed = 1;
            }
        }
    }

  /* Dump the chains of functions we've made.  */
  for (index = 0; index < numarcs; index++)
    {
      Sym *sym;
      if (arcs[index]->parent->has_been_placed
          || arcs[index]->child->has_been_placed)
        continue;

      sym = arcs[index]->parent;

      /* If this symbol isn't attached to any other
         symbols, then we've got a rarely used arc.

         Skip it for now, we'll deal with them later.  */
      if (sym->next == NULL
          && sym->prev == NULL)
        continue;

      /* Get to the start of this chain.  */
      while (sym->prev)
        sym = sym->prev;

      while (sym)
        {
          /* Mark it as placed.  */
          sym->has_been_placed = 1;
          printf ("%s\n", sym->name);
          sym = sym->next;
        }
    }

  /* If we want to place all the arcs, then output
     those which weren't placed by the main algorithm.  */
  if (all)
    for (index = 0; index < numarcs; index++)
      {
        Sym *sym;
        if (arcs[index]->parent->has_been_placed
            || arcs[index]->child->has_been_placed)
          continue;

        sym = arcs[index]->parent;

        sym->has_been_placed = 1;
        printf ("%s\n", sym->name);
      }
}

/* Print a suggested .o ordering for files on a link line based
   on profiling information.  This uses the function placement
   code for the bulk of its work.  */

struct function_map
{
  char *function_name;
  char *file_name;
};

void
DEFUN_VOID (cg_print_file_ordering)
{
  unsigned long scratch_arc_count, index;
  Arc **scratch_arcs;
  extern struct function_map *symbol_map;
  extern unsigned int symbol_map_count;
  char *last;

  scratch_arc_count = 0;

  scratch_arcs = (Arc **) xmalloc (numarcs * sizeof (Arc *));
  for (index = 0; index < numarcs; index++)
    {
      if (! arcs[index]->parent->mapped
          || ! arcs[index]->child->mapped)
        arcs[index]->has_been_placed = 1;
    }

  order_and_dump_functions_by_arcs (arcs, numarcs, 0,
                                    scratch_arcs, &scratch_arc_count);

  /* Output .o's not handled by the main placement algorithm.  */
  for (index = 0; index < symtab.len; index++)
    {
      if (symtab.base[index].mapped
          && ! symtab.base[index].has_been_placed)
        printf ("%s\n", symtab.base[index].name);
    }

  /* Now output any .o's that didn't have any text symbols.  */
  last = NULL;
  for (index = 0; index < symbol_map_count; index++)
    {
      unsigned int index2;

      /* Don't bother searching if this symbol
         is the same as the previous one.  */
      if (last && !strcmp (last, symbol_map[index].file_name))
        continue;

      for (index2 = 0; index2 < symtab.len; index2++)
        {
          if (! symtab.base[index2].mapped)
            continue;

          if (!strcmp (symtab.base[index2].name, symbol_map[index].file_name))
            break;
        }

      /* If we didn't find it in the symbol table, then it must
         be a .o with no text symbols.  Output it last.  */
      if (index2 == symtab.len)
        printf ("%s\n", symbol_map[index].file_name);
      last = symbol_map[index].file_name;
    } 
}