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/*

 * Copyright (c) 1983, 1993

 *      The Regents of the University of California.  All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 3. Neither the name of the University nor the names of its contributors

 *    may be used to endorse or promote products derived from this software

 *    without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

 * SUCH DAMAGE.

 */

#include "libiberty.h"

#include "gprof.h"

#include "search_list.h"

#include "source.h"

#include "symtab.h"

#include "cg_arcs.h"

#include "cg_dfn.h"

#include "utils.h"

#define DFN_INCR_DEPTH (128)

typedef struct

  {

    Sym *sym;

    int cycle_top;

  }

DFN_Stack;

static bfd_boolean is_numbered (Sym *);

static bfd_boolean is_busy (Sym *);

static void find_cycle (Sym *);

static void pre_visit (Sym *);

static void post_visit (Sym *);

DFN_Stack *dfn_stack = NULL;

int dfn_maxdepth = 0;

int dfn_depth = 0;

int dfn_counter = DFN_NAN;

/*

 * Is CHILD already numbered?

 */

static bfd_boolean

is_numbered (Sym *child)

{

  return child->cg.top_order != DFN_NAN && child->cg.top_order != DFN_BUSY;

}

/*

 * Is CHILD already busy?

 */

static bfd_boolean

is_busy (Sym *child)

{

  if (child->cg.top_order == DFN_NAN)

    {

      return FALSE;

    }

  return TRUE;

}

/*

 * CHILD is part of a cycle.  Find the top caller into this cycle

 * that is not part of the cycle and make all functions in cycle

 * members of that cycle (top caller == caller with smallest

 * depth-first number).

 */

static void

find_cycle (Sym *child)

{

  Sym *head = 0;

  Sym *tail;

  int cycle_top;

  int index;

  for (cycle_top = dfn_depth; cycle_top > 0; --cycle_top)

    {

      head = dfn_stack[cycle_top].sym;

      if (child == head)

        {

          break;

        }

      if (child->cg.cyc.head != child && child->cg.cyc.head == head)

        {

          break;

        }

    }

  if (cycle_top <= 0)

    {

      fprintf (stderr, "[find_cycle] couldn't find head of cycle\n");

      done (1);

    }

#ifdef DEBUG

  if (debug_level & DFNDEBUG)

    {

      printf ("[find_cycle] dfn_depth %d cycle_top %d ",

              dfn_depth, cycle_top);

      if (head)

        {

          print_name (head);

        }

      else

        {

          printf ("<unknown>");

        }

      printf ("\n");

    }

#endif

  if (cycle_top == dfn_depth)

    {

      /*

       * This is previous function, e.g. this calls itself.  Sort of

       * boring.

       *

       * Since we are taking out self-cycles elsewhere no need for

       * the special case, here.

       */

      DBG (DFNDEBUG,

           printf ("[find_cycle] ");

           print_name (child);

           printf ("\n"));

    }

  else

    {

      /*

       * Glom intervening functions that aren't already glommed into

       * this cycle.  Things have been glommed when their cyclehead

       * field points to the head of the cycle they are glommed

       * into.

       */

      for (tail = head; tail->cg.cyc.next; tail = tail->cg.cyc.next)

        {

          /* void: chase down to tail of things already glommed */

          DBG (DFNDEBUG,

               printf ("[find_cycle] tail ");

               print_name (tail);

               printf ("\n"));

        }

      /*

       * If what we think is the top of the cycle has a cyclehead

       * field, then it's not really the head of the cycle, which is

       * really what we want.

       */

      if (head->cg.cyc.head != head)

        {

          head = head->cg.cyc.head;

          DBG (DFNDEBUG, printf ("[find_cycle] new cyclehead ");

               print_name (head);

               printf ("\n"));

        }

      for (index = cycle_top + 1; index <= dfn_depth; ++index)

        {

          child = dfn_stack[index].sym;

          if (child->cg.cyc.head == child)

            {

              /*

               * Not yet glommed anywhere, glom it and fix any

               * children it has glommed.

               */

              tail->cg.cyc.next = child;

              child->cg.cyc.head = head;

              DBG (DFNDEBUG, printf ("[find_cycle] glomming ");

                   print_name (child);

                   printf (" onto ");

                   print_name (head);

                   printf ("\n"));

              for (tail = child; tail->cg.cyc.next; tail = tail->cg.cyc.next)

                {

                  tail->cg.cyc.next->cg.cyc.head = head;

                  DBG (DFNDEBUG, printf ("[find_cycle] and its tail ");

                       print_name (tail->cg.cyc.next);

                       printf (" onto ");

                       print_name (head);

                       printf ("\n"));

                }

            }

          else if (child->cg.cyc.head != head /* firewall */ )

            {

              fprintf (stderr, "[find_cycle] glommed, but not to head\n");

              done (1);

            }

        }

    }

}

/*

 * Prepare for visiting the children of PARENT.  Push a parent onto

 * the stack and mark it busy.

 */

static void

pre_visit (Sym *parent)

{

  ++dfn_depth;

  if (dfn_depth >= dfn_maxdepth)

    {

      dfn_maxdepth += DFN_INCR_DEPTH;

      dfn_stack = xrealloc (dfn_stack, dfn_maxdepth * sizeof *dfn_stack);

    }

  dfn_stack[dfn_depth].sym = parent;

  dfn_stack[dfn_depth].cycle_top = dfn_depth;

  parent->cg.top_order = DFN_BUSY;

  DBG (DFNDEBUG, printf ("[pre_visit]\t\t%d:", dfn_depth);

       print_name (parent);

       printf ("\n"));

}

/*

 * Done with visiting node PARENT.  Pop PARENT off dfn_stack

 * and number functions if PARENT is head of a cycle.

 */

static void

post_visit (Sym *parent)

{

  Sym *member;

  DBG (DFNDEBUG, printf ("[post_visit]\t%d: ", dfn_depth);

       print_name (parent);

       printf ("\n"));

  /*

   * Number functions and things in their cycles unless the function

   * is itself part of a cycle:

   */

  if (parent->cg.cyc.head == parent)

    {

      ++dfn_counter;

      for (member = parent; member; member = member->cg.cyc.next)

        {

          member->cg.top_order = dfn_counter;

          DBG (DFNDEBUG, printf ("[post_visit]\t\tmember ");

               print_name (member);

               printf ("-> cg.top_order = %d\n", dfn_counter));

        }

    }

  else

    {

      DBG (DFNDEBUG, printf ("[post_visit]\t\tis part of a cycle\n"));

    }

  --dfn_depth;

}

/*

 * Given this PARENT, depth first number its children.

 */

void

cg_dfn (Sym *parent)

{

  Arc *arc;

  DBG (DFNDEBUG, printf ("[dfn] dfn( ");

       print_name (parent);

       printf (")\n"));

  /*

   * If we're already numbered, no need to look any further:

   */

  if (is_numbered (parent))

    {

      return;

    }

  /*

   * If we're already busy, must be a cycle:

   */

  if (is_busy (parent))

    {

      find_cycle (parent);

      return;

    }

  pre_visit (parent);

  /*

   * Recursively visit children:

   */

  for (arc = parent->cg.children; arc; arc = arc->next_child)

    {

      cg_dfn (arc->child);

    }

  post_visit (parent);

}