No longer needed, since we're not using the stage stuff.

[bison.git] / lib / ebitset.c

/* Functions to support expandable bitsets.
   Copyright (C) 2002 Free Software Foundation, Inc.
   Contributed by Michael Hayes (m.hayes@elec.canterbury.ac.nz).

   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. 
*/

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "ebitset.h"
#include "obstack.h"
#include <stdlib.h>

/* This file implements expandable bitsets.  These bitsets can be of
   arbitrary length and are more efficient than arrays of bits for
   large sparse sets.

   Empty elements are represented by a NULL pointer in the table of
   element pointers.  An alternative is to point to a special zero
   element.  Similarly, we could represent an all 1's element with
   another special ones element pointer.

   Bitsets are commonly empty so we need to ensure that this special
   case is fast.  A zero bitset is indicated when cdata is 0.  This is
   conservative since cdata may be non zero and the bitset may still
   be zero. 

   The bitset cache can be disabled either by setting cindex to
   some large number or by setting csize to 0.  Here 
   we use the former approach since cindex needs to be updated whenever
   cdata is changed.   
*/


/* Number of words to use for each element.  */
#define EBITSET_ELT_WORDS 2

/* Number of bits stored in each element.  */
#define EBITSET_ELT_BITS \
  ((unsigned) (EBITSET_ELT_WORDS * BITSET_WORD_BITS))

/* Ebitset element.  We use an array of bits.  */
typedef struct ebitset_elt_struct
{
  union
  {
    bitset_word words[EBITSET_ELT_WORDS];	/* Bits that are set.  */
    struct ebitset_elt_struct *next;
  }
  u;
}
ebitset_elt;


typedef ebitset_elt *ebitset_elts;

/* Head of ebitset linked list.  */
typedef struct ebitset_struct
{
  unsigned int size;		/* Number of elements.  */
  ebitset_elts *elts;		/* Expanding array of pointers to elements.  */
}
*ebitset;


/* Number of elements to initially allocate.  */

#ifndef EBITSET_INITIAL_SIZE
#define EBITSET_INITIAL_SIZE 2
#endif

/* Minimum number of elements to grow table.  */

#ifndef EBITSET_GROW_SIZE
#define EBITSET_GROW_SIZE 4
#endif

struct bitset_struct
{
  struct bbitset_struct b;
  struct ebitset_struct e;
};

enum ebitset_find_mode
  { EBITSET_FIND, EBITSET_CREATE, EBITSET_SUBST };

static ebitset_elt ebitset_zero_elts[1]; /* Elements of all zero bits.  */

/* Obstack to allocate bitset elements from.  */
static struct obstack ebitset_obstack;
static int ebitset_obstack_init = 0;
static ebitset_elt *ebitset_free_list;	/* Free list of bitset elements.  */

static void ebitset_elts_grow PARAMS ((bitset, unsigned int));
static ebitset_elt *ebitset_elt_alloc PARAMS ((void));
static ebitset_elt *ebitset_elt_calloc PARAMS ((void));
static void ebitset_elt_add PARAMS ((bitset, ebitset_elt *, unsigned int));
static void ebitset_elt_remove PARAMS ((bitset, unsigned int));
static void ebitset_elt_free PARAMS ((ebitset_elt *));
static ebitset_elt *ebitset_elt_find PARAMS ((bitset, bitset_windex,
					      enum ebitset_find_mode));
static ebitset_elt *ebitset_elt_last PARAMS ((bitset));
static int ebitset_elt_zero_p PARAMS ((ebitset_elt *));

static int ebitset_weed PARAMS ((bitset));
static void ebitset_zero PARAMS ((bitset));
static int ebitset_equal_p PARAMS ((bitset, bitset));
static void ebitset_copy PARAMS ((bitset, bitset));
static int ebitset_copy_compare PARAMS ((bitset, bitset));
static void ebitset_set PARAMS ((bitset, bitset_bindex));
static void ebitset_reset PARAMS ((bitset, bitset_bindex));
static int ebitset_test PARAMS ((bitset, bitset_bindex));
static int ebitset_size PARAMS ((bitset));
static int ebitset_op1 PARAMS ((bitset, enum bitset_ops));
static int ebitset_op2 PARAMS ((bitset, bitset, enum bitset_ops));
static int ebitset_op3 PARAMS ((bitset, bitset, bitset, enum bitset_ops));
static int ebitset_list PARAMS ((bitset, bitset_bindex *, bitset_bindex,
				 bitset_bindex *));
static int ebitset_reverse_list
PARAMS ((bitset, bitset_bindex *, bitset_bindex, bitset_bindex *));
static void ebitset_free PARAMS ((bitset));

#define EBITSET_ELTS(BSET) ((BSET)->e.elts)
#define EBITSET_SIZE(BSET) ((BSET)->e.size)

#define EBITSET_NEXT(ELT) ((ELT)->u.next)
#define EBITSET_WORDS(ELT) ((ELT)->u.words)

/* Disable bitset cache and mark BSET as being zero.  */
#define EBITSET_OP_ZERO_SET(BSET) ((BSET)->b.cindex = BITSET_INDEX_MAX, \
        (BSET)->b.cdata = 0)

#define EBITSET_CACHE_DISABLE(BSET)  ((BSET)->b.cindex = BITSET_INDEX_MAX)

/* Disable bitset cache and mark BSET as being possibly non-zero.  */
#define EBITSET_NONZERO_SET(BSET) \
 (EBITSET_CACHE_DISABLE (BSET), (BSET)->b.cdata = (bitset_word *)~0)

/* A conservative estimate of whether the bitset is zero.
   This is non-zero only if we know for sure that the bitset is zero.  */
#define EBITSET_OP_ZERO_P(BSET) ((BSET)->b.cdata == 0)

/* Enable cache to point to element with table index EINDEX. 
   The element must exist.  */
#define EBITSET_CACHE_SET(BSET, EINDEX) \
 ((BSET)->b.cindex = (EINDEX) * EBITSET_ELT_WORDS, \
  (BSET)->b.cdata = EBITSET_WORDS (EBITSET_ELTS (BSET) [EINDEX]))


/* Grow the expandable table for BSET by SIZE elements.  */
static void
ebitset_elts_grow (bset, size)
     bitset bset;
     unsigned int size;
{
  unsigned int oldsize;
  unsigned int newsize;

  oldsize = EBITSET_SIZE (bset);
  newsize = oldsize + size;

  EBITSET_ELTS (bset) = xrealloc (EBITSET_ELTS (bset),
				  newsize * sizeof (ebitset_elt *));
  EBITSET_SIZE (bset) = newsize;

  memset (EBITSET_ELTS (bset) + oldsize, 0, size * sizeof (ebitset_elt *));
}


/* Allocate a ebitset element.  The bits are not cleared.  */
static inline ebitset_elt *
ebitset_elt_alloc ()
{
  ebitset_elt *elt;

  if (ebitset_free_list != 0)
    {
      elt = ebitset_free_list;
      ebitset_free_list = EBITSET_NEXT (elt);
    }
  else
    {
      if (!ebitset_obstack_init)
	{
	  ebitset_obstack_init = 1;

	  /* Let particular systems override the size of a chunk.  */

#ifndef OBSTACK_CHUNK_SIZE
#define OBSTACK_CHUNK_SIZE 0
#endif

	  /* Let them override the alloc and free routines too.  */

#ifndef OBSTACK_CHUNK_ALLOC
#define OBSTACK_CHUNK_ALLOC xmalloc
#endif

#ifndef OBSTACK_CHUNK_FREE
#define OBSTACK_CHUNK_FREE free
#endif

#if !defined(__GNUC__) || (__GNUC__ < 2)
#define __alignof__(type) 0
#endif

	  obstack_specify_allocation (&ebitset_obstack, OBSTACK_CHUNK_SIZE,
				      __alignof__ (ebitset_elt),
				      (void *(*)PARAMS ((long)))
				      OBSTACK_CHUNK_ALLOC,
				      (void (*)PARAMS ((void *)))
				      OBSTACK_CHUNK_FREE);
	}

      /* Perhaps we should add a number of new elements to the free
	 list.  */
      elt = (ebitset_elt *) obstack_alloc (&ebitset_obstack,
					   sizeof (ebitset_elt));
    }

  return elt;
}


/* Allocate a ebitset element.  The bits are cleared.  */
static inline ebitset_elt *
ebitset_elt_calloc ()
{
  ebitset_elt *elt;

  elt = ebitset_elt_alloc ();
  memset (EBITSET_WORDS (elt), 0, sizeof (EBITSET_WORDS (elt)));
  return elt;
}


static inline void
ebitset_elt_free (elt)
     ebitset_elt *elt;
{
  EBITSET_NEXT (elt) = ebitset_free_list;
  ebitset_free_list = elt;
}


/* Remove element with index EINDEX from bitset BSET.  */
static inline void
ebitset_elt_remove (bset, eindex)
     bitset bset;
     unsigned int eindex;
{
  ebitset_elts *elts;
  ebitset_elt *elt;

  elts = EBITSET_ELTS (bset);

  elt = elts[eindex];

  elts[eindex] = 0;
  ebitset_elt_free (elt);
}


/* Add ELT into elts at index EINDEX of bitset BSET.  */
static inline void
ebitset_elt_add (bset, elt, eindex)
     bitset bset;
     ebitset_elt *elt;
     unsigned int eindex;
{
  ebitset_elts *elts;

  elts = EBITSET_ELTS (bset);
  /* Assume that the elts entry not allocated.  */
  elts[eindex] = elt;
}


/* Return nonzero if all bits in an element are zero.  */
static inline int
ebitset_elt_zero_p (elt)
     ebitset_elt *elt;
{
  int i;

  for (i = 0; i < EBITSET_ELT_WORDS; i++)
    if (EBITSET_WORDS (elt)[i])
      return 0;

  return 1;
}


static ebitset_elt *
ebitset_elt_find (bset, windex, mode)
     bitset bset;
     bitset_windex windex;
     enum ebitset_find_mode mode;
{
  ebitset_elt *elt;
  bitset_windex size;
  unsigned int eindex;
  ebitset_elts *elts;

  eindex = windex / EBITSET_ELT_WORDS;

  elts = EBITSET_ELTS (bset);
  size = EBITSET_SIZE (bset);

  if (eindex < size)
    {
      if ((elt = elts[eindex]))
	{
	  if (EBITSET_WORDS (elt) == bset->b.cdata)
	    return elt;

	  EBITSET_CACHE_SET (bset, eindex);
	  return elt;
	}
    }

  /* The element could not be found.  */

  switch (mode)
    {
    case EBITSET_FIND:
      return 0;

    case EBITSET_CREATE:
      if (eindex >= size)
	{
	  unsigned int extra;

	  extra = eindex - size + 1;

	  /* We need to expand the table by EXTRA elements.  It may be
	     better with large bitsets to grow the number of
	     elements by some fraction of the current size otherwise
	     we can spend a lot of time slowly increasing the size of the
	     bitset.  */
	  if (extra < EBITSET_GROW_SIZE)
	    extra = EBITSET_GROW_SIZE;

	  ebitset_elts_grow (bset, extra);
	}

      /* Create a new element.  */
      elt = ebitset_elt_calloc ();
      ebitset_elt_add (bset, elt, eindex);
      EBITSET_CACHE_SET (bset, eindex);
      return elt;

    case EBITSET_SUBST:
      return &ebitset_zero_elts[0];

    default:
      abort ();
    }
}


static inline ebitset_elt *
ebitset_elt_last (bset)
     bitset bset;
{
  ebitset_elts *elts;

  elts = EBITSET_ELTS (bset);

  /* Assume that have at least one element in elts.  */
  return elts[EBITSET_SIZE (bset) - 1];
}


/* Weed out the zero elements from the elts.  */
static inline int
ebitset_weed (bset)
     bitset bset;
{
  ebitset_elts *elts;
  bitset_windex j;
  int count;

  if (EBITSET_OP_ZERO_P (bset))
    return 0;

  elts = EBITSET_ELTS (bset);
  count = 0;
  for (j = 0; j < EBITSET_SIZE (bset); j++)
    {
      ebitset_elt *elt = elts[j];

      if (elt)
	{
	  if (elt && ebitset_elt_zero_p (elt))
	    {
	      ebitset_elt_remove (bset, j);
	      count++;
	    }
	}
      else
	count++;
    }

  count = j - count;
  if (!count)
    {
      /* All the bits are zero.  We could shrink the elts. 
	 For now just mark BSET as known to be zero.  */
      EBITSET_OP_ZERO_SET (bset);
    }
  else
    EBITSET_NONZERO_SET (bset);

  return count;
}


/* Set all bits in the bitset to zero.  */
static inline void
ebitset_zero (bset)
     bitset bset;
{
  ebitset_elts *elts;
  bitset_windex j;

  if (EBITSET_OP_ZERO_P (bset))
    return;

  elts = EBITSET_ELTS (bset);
  for (j = 0; j < EBITSET_SIZE (bset); j++)
    {
      ebitset_elt *elt = elts[j];

      if (elt)
	ebitset_elt_remove (bset, j);
    }

  /* All the bits are zero.  We could shrink the elts. 
     For now just mark BSET as known to be zero.  */
  EBITSET_OP_ZERO_SET (bset);
}


static inline int
ebitset_equal_p (dst, src)
     bitset dst;
     bitset src;
{
  ebitset_elts *selts;
  ebitset_elts *delts;
  bitset_windex j;

  if (src == dst)
    return 1;

  ebitset_weed (dst);
  ebitset_weed (src);

  if (EBITSET_SIZE (src) != EBITSET_SIZE (dst))
    return 0;

  selts = EBITSET_ELTS (src);
  delts = EBITSET_ELTS (dst);

  for (j = 0; j < EBITSET_SIZE (src); j++)
    {
      unsigned int i;
      ebitset_elt *selt = selts[j];
      ebitset_elt *delt = delts[j];

      if (!selt && !delt)
	continue;
      if ((selt && !delt) || (!selt && delt))
	return 0;

      for (i = 0; i < EBITSET_ELT_WORDS; i++)
	if (EBITSET_WORDS (selt)[i] != EBITSET_WORDS (delt)[i])
	  return 0;
    }
  return 1;
}


/* Copy bits from bitset SRC to bitset DST.  */
static inline void
ebitset_copy (dst, src)
     bitset dst;
     bitset src;
{
  ebitset_elts *selts;
  ebitset_elts *delts;
  bitset_windex j;

  if (src == dst)
    return;

  ebitset_zero (dst);

  if (EBITSET_SIZE (dst) < EBITSET_SIZE (src))
    ebitset_elts_grow (dst, EBITSET_SIZE (src) - EBITSET_SIZE (dst));

  selts = EBITSET_ELTS (src);
  delts = EBITSET_ELTS (dst);
  for (j = 0; j < EBITSET_SIZE (src); j++)
    {
      ebitset_elt *selt = selts[j];

      if (selt)
	{
	  ebitset_elt *tmp;

	  tmp = ebitset_elt_alloc ();
	  delts[j] = tmp;
	  memcpy (EBITSET_WORDS (tmp), EBITSET_WORDS (selt),
		  sizeof (EBITSET_WORDS (selt)));
	}
    }
  EBITSET_NONZERO_SET (dst);
}


/* Copy bits from bitset SRC to bitset DST.  Return non-zero if
   bitsets different.  */
static inline int
ebitset_copy_compare (dst, src)
     bitset dst;
     bitset src;
{
  if (src == dst)
    return 0;

  if (EBITSET_OP_ZERO_P (dst))
    {
      ebitset_copy (dst, src);
      return !EBITSET_OP_ZERO_P (src);
    }

  if (ebitset_equal_p (dst, src))
    return 0;

  ebitset_copy (dst, src);
  return 1;
}


/* Return size in bits of bitset SRC.  */
static int
ebitset_size (src)
     bitset src;
{
  /* Return current size of bitset in bits.  */
  return EBITSET_SIZE (src) * EBITSET_ELT_BITS;
}


/* Set bit BITNO in bitset DST.  */
static void
ebitset_set (dst, bitno)
     bitset dst;
     bitset_bindex bitno;
{
  bitset_windex windex = bitno / BITSET_WORD_BITS;

  ebitset_elt_find (dst, windex, EBITSET_CREATE);

  dst->b.cdata[windex - dst->b.cindex] |=
    (bitset_word) 1 << (bitno % BITSET_WORD_BITS);
}


/* Reset bit BITNO in bitset DST.  */
static void
ebitset_reset (dst, bitno)
     bitset dst;
     bitset_bindex bitno;
{
  bitset_windex windex = bitno / BITSET_WORD_BITS;

  if (!ebitset_elt_find (dst, windex, EBITSET_FIND))
    return;

  dst->b.cdata[windex - dst->b.cindex] &=
    ~((bitset_word) 1 << (bitno % BITSET_WORD_BITS));

  /* If all the data is zero, perhaps we should remove it now... 
     However, there is a good chance that the element will be needed
     again soon.  */
}


/* Test bit BITNO in bitset SRC.  */
static int
ebitset_test (src, bitno)
     bitset src;
     bitset_bindex bitno;
{
  bitset_windex windex = bitno / BITSET_WORD_BITS;

  if (!ebitset_elt_find (src, windex, EBITSET_FIND))
    return 0;

  return (src->b.
	  cdata[windex - src->b.cindex] >> (bitno % BITSET_WORD_BITS)) & 1;
}


static void
ebitset_free (bset)
     bitset bset;
{
  ebitset_zero (bset);
  free (EBITSET_ELTS (bset));
}


/* Find list of up to NUM bits set in BSET starting from and including
 *NEXT and store in array LIST.  Return with actual number of bits
 found and with *NEXT indicating where search stopped.  */
static int
ebitset_reverse_list (bset, list, num, next)
     bitset bset;
     bitset_bindex *list;
     bitset_bindex num;
     bitset_bindex *next;
{
  bitset_bindex n_bits;
  bitset_bindex bitno;
  bitset_bindex rbitno;
  unsigned int bcount;
  bitset_bindex boffset;
  bitset_windex windex;
  unsigned int eindex;
  bitset_windex woffset;
  bitset_bindex count;
  bitset_windex size;
  ebitset_elts *elts;

  if (EBITSET_OP_ZERO_P (bset))
    return 0;

  size = EBITSET_SIZE (bset);
  n_bits = size * EBITSET_ELT_BITS;
  rbitno = *next;

  if (rbitno >= n_bits)
    return 0;

  elts = EBITSET_ELTS (bset);

  bitno = n_bits - (rbitno + 1);

  windex = bitno / BITSET_WORD_BITS;
  eindex = bitno / EBITSET_ELT_BITS;
  woffset = windex - eindex * EBITSET_ELT_WORDS;

  /* If num is 1, we could speed things up with a binary search
     of the word of interest.  */

  count = 0;
  bcount = bitno % BITSET_WORD_BITS;
  boffset = windex * BITSET_WORD_BITS;

  do
    {
      ebitset_elt *elt;

      elt = elts[eindex];
      if (elt)
	{
	  bitset_word *srcp;

	  srcp = EBITSET_WORDS (elt);

	  do
	    {
	      bitset_word word;

	      word = srcp[woffset] << (BITSET_WORD_BITS - 1 - bcount);

	      for (; word; bcount--)
		{
		  if (word & BITSET_MSB)
		    {
		      list[count++] = boffset + bcount;
		      if (count >= num)
			{
			  *next = n_bits - (boffset + bcount);
			  return count;
			}
		    }
		  word <<= 1;
		}

	      boffset -= BITSET_WORD_BITS;
	      bcount = BITSET_WORD_BITS - 1;
	    }
	  while (woffset--);

	  woffset = EBITSET_ELT_WORDS;
	}

      boffset = eindex * EBITSET_ELT_BITS - BITSET_WORD_BITS;
    }
  while (eindex--);

  *next = n_bits - (boffset + 1);
  return count;
}


/* Find list of up to NUM bits set in BSET starting from and including
 *NEXT and store in array LIST.  Return with actual number of bits
 found and with *NEXT indicating where search stopped.  */
static int
ebitset_list (bset, list, num, next)
     bitset bset;
     bitset_bindex *list;
     bitset_bindex num;
     bitset_bindex *next;
{
  bitset_bindex bitno;
  bitset_windex windex;
  unsigned int eindex;
  bitset_bindex count;
  bitset_windex size;
  ebitset_elt *elt;
  bitset_word word;
  ebitset_elts *elts;

  if (EBITSET_OP_ZERO_P (bset))
    return 0;

  bitno = *next;
  count = 0;

  elts = EBITSET_ELTS (bset);
  size = EBITSET_SIZE (bset);
  eindex = bitno / EBITSET_ELT_BITS;

  if (bitno % EBITSET_ELT_BITS)
    {
      /* We need to start within an element.  This is not very common.  */

      elt = elts[eindex];
      if (elt)
	{
	  bitset_windex woffset;
	  bitset_word *srcp = EBITSET_WORDS (elt);

	  windex = bitno / BITSET_WORD_BITS;
	  woffset = eindex / EBITSET_ELT_WORDS;

	  for (; (windex - woffset) < EBITSET_ELT_WORDS; windex++)
	    {
	      word = srcp[windex - woffset] >> (bitno % BITSET_WORD_BITS);

	      for (; word; bitno++)
		{
		  if (word & 1)
		    {
		      list[count++] = bitno;
		      if (count >= num)
			{
			  *next = bitno + 1;
			  return count;
			}
		    }
		  word >>= 1;
		}
	      bitno = (windex + 1) * BITSET_WORD_BITS;
	    }
	}

      /* Skip to next element.  */
      eindex++;
    }

  /* If num is 1, we could speed things up with a binary search
     of the word of interest.  */

  for (; eindex < size; eindex++)
    {
      int i;
      bitset_word *srcp;

      elt = elts[eindex];
      if (!elt)
	continue;

      srcp = EBITSET_WORDS (elt);
      windex = eindex * EBITSET_ELT_WORDS;

      if ((count + EBITSET_ELT_BITS) < num)
	{
	  /* The coast is clear, plant boot!  */

	  for (i = 0; i < EBITSET_ELT_WORDS; i++, windex++)
	    {
	      bitno = windex * BITSET_WORD_BITS;

	      word = srcp[i];
	      if (word)
		{
		  if (!(word & 0xffff))
		    {
		      word >>= 16;
		      bitno += 16;
		    }
		  if (!(word & 0xff))
		    {
		      word >>= 8;
		      bitno += 8;
		    }
		  for (; word; bitno++)
		    {
		      if (word & 1)
			list[count++] = bitno;
		      word >>= 1;
		    }
		}
	    }
	}
      else
	{
	  /* Tread more carefully since we need to check
	     if array overflows.  */

	  for (i = 0; i < EBITSET_ELT_WORDS; i++, windex++)
	    {
	      bitno = windex * BITSET_WORD_BITS;

	      for (word = srcp[i]; word; bitno++)
		{
		  if (word & 1)
		    {
		      list[count++] = bitno;
		      if (count >= num)
			{
			  *next = bitno + 1;
			  return count;
			}
		    }
		  word >>= 1;
		}
	    }
	}
    }

  *next = bitno;
  return count;
}


static int
ebitset_op1 (dst, op)
     bitset dst;
     enum bitset_ops op;
{
  bitset_windex j;
  ebitset_elt *elt;

  switch (op)
    {
    case BITSET_OP_ZERO:
      ebitset_zero (dst);
      return 1;

    case BITSET_OP_ONES:
      for (j = 0; j < EBITSET_SIZE (dst); j++)
	{
	  /* Create new elements if they cannot be found.  Perhaps
	     we should just add pointers to a ones element.  */
	  elt =
	    ebitset_elt_find (dst, j * EBITSET_ELT_WORDS, EBITSET_CREATE);
	  memset (EBITSET_WORDS (elt), -1, sizeof (EBITSET_WORDS (elt)));
	}
      break;

    case BITSET_OP_EMPTY_P:
      return !ebitset_weed (dst);

    default:
      abort ();
    }

  EBITSET_NONZERO_SET (dst);
  return 1;
}


static int
ebitset_op2 (dst, src, op)
     bitset dst;
     bitset src;
     enum bitset_ops op;
{
  ebitset_elt *selt;
  ebitset_elt *delt;
  unsigned int i;
  bitset_windex j;

  switch (op)
    {
    case BITSET_OP_COPY:
      ebitset_copy (dst, src);
      break;

    case BITSET_OP_NOT:
      for (j = 0; j < EBITSET_SIZE (src); j++)
	{
	  /* Create new elements for dst if they cannot be found
	     or substitute zero elements if src elements not found.  */
	  selt =
	    ebitset_elt_find (dst, j * EBITSET_ELT_WORDS, EBITSET_SUBST);
	  delt =
	    ebitset_elt_find (dst, j * EBITSET_ELT_WORDS, EBITSET_CREATE);

	  for (i = 0; i < EBITSET_ELT_WORDS; i++)
	    EBITSET_WORDS (delt)[i] = ~EBITSET_WORDS (selt)[i];
	}
      break;

      /* Return 1 if DST == SRC.  */
    case BITSET_OP_EQUAL_P:
      return ebitset_equal_p (dst, src);

      /* Return 1 if DST == DST | SRC.  */
    case BITSET_OP_SUBSET_P:
      {
	ebitset_elts *selts;
	ebitset_elts *delts;
	bitset_windex ssize;
	bitset_windex dsize;

	selts = EBITSET_ELTS (src);
	delts = EBITSET_ELTS (dst);

	ssize = EBITSET_SIZE (src);
	dsize = EBITSET_SIZE (dst);

	for (j = 0; j < ssize; j++)
	  {
	    selt = j < ssize ? selts[j] : 0;
	    delt = j < dsize ? delts[j] : 0;

	    if (!selt && !delt)
	      continue;

	    if (!selt)
	      selt = &ebitset_zero_elts[0];
	    if (!delt)
	      delt = &ebitset_zero_elts[0];

	    for (i = 0; i < EBITSET_ELT_WORDS; i++)
	      if (EBITSET_WORDS (delt)[i]
		  != (EBITSET_WORDS (selt)[i] | EBITSET_WORDS (delt)[i]))
		return 0;
	  }
	return 1;
      }
      break;

      /* Return 1 if DST & SRC == 0.  */
    case BITSET_OP_DISJOINT_P:
      {
	ebitset_elts *selts;
	ebitset_elts *delts;
	bitset_windex ssize;
	bitset_windex dsize;

	selts = EBITSET_ELTS (src);
	delts = EBITSET_ELTS (dst);

	ssize = EBITSET_SIZE (src);
	dsize = EBITSET_SIZE (dst);

	for (j = 0; j < ssize; j++)
	  {
	    selt = j < ssize ? selts[j] : 0;
	    delt = j < dsize ? delts[j] : 0;

	    if (!selt || !delt)
	      continue;

	    for (i = 0; i < EBITSET_ELT_WORDS; i++)
	      if ((EBITSET_WORDS (selt)[i] & EBITSET_WORDS (delt)[i]))
		return 0;
	  }
	return 1;
      }
      break;

    default:
      abort ();
    }

  EBITSET_NONZERO_SET (dst);
  return 1;
}


static int
ebitset_op3 (dst, src1, src2, op)
     bitset dst;
     bitset src1;
     bitset src2;
     enum bitset_ops op;
{
  bitset_windex ssize1;
  bitset_windex ssize2;
  bitset_windex dsize;
  bitset_windex size;
  ebitset_elts *selts1;
  ebitset_elts *selts2;
  ebitset_elts *delts;
  bitset_word *srcp1;
  bitset_word *srcp2;
  bitset_word *dstp;
  int changed = 0;
  unsigned int i;
  bitset_windex j;

  /* Fast track common, simple cases.  */
  if (EBITSET_OP_ZERO_P (src2))
    {
      if (op == BITSET_OP_AND)
	{
	  ebitset_weed (dst);
	  changed = EBITSET_OP_ZERO_P (dst);
	  ebitset_zero (dst);
	  return changed;
	}
      else if (op == BITSET_OP_ANDN || op == BITSET_OP_OR
	       || op == BITSET_OP_XOR)
	{
	  return ebitset_copy_compare (dst, src1);
	}
    }
  else if (EBITSET_OP_ZERO_P (src1))
    {
      if (op == BITSET_OP_AND || op == BITSET_OP_ANDN)
	{
	  ebitset_weed (dst);
	  changed = EBITSET_OP_ZERO_P (dst);
	  ebitset_zero (dst);
	  return changed;
	}
      else if (op == BITSET_OP_OR || op == BITSET_OP_XOR)
	{
	  return ebitset_copy_compare (dst, src2);
	}
    }

  ssize1 = EBITSET_SIZE (src1);
  ssize2 = EBITSET_SIZE (src2);
  dsize = EBITSET_SIZE (dst);
  size = ssize1;
  if (size < ssize2)
    size = ssize2;

  if (size > dsize)
    ebitset_elts_grow (dst, size - dsize);

  selts1 = EBITSET_ELTS (src1);
  selts2 = EBITSET_ELTS (src2);
  delts = EBITSET_ELTS (dst);

  for (j = 0; j < size; j++)
    {
      ebitset_elt *selt1;
      ebitset_elt *selt2;
      ebitset_elt *delt;

      selt1 = j < ssize1 ? selts1[j] : 0;
      selt2 = j < ssize2 ? selts2[j] : 0;
      delt = j < dsize ? delts[j] : 0;

      if (!selt1 && !selt2)
	{
	  if (delt)
	    {
	      changed = 1;
	      ebitset_elt_remove (dst, j);
	    }
	  continue;
	}

      if (!selt1)
	selt1 = &ebitset_zero_elts[0];
      if (!selt2)
	selt2 = &ebitset_zero_elts[0];
      if (!delt)
	delt = ebitset_elt_calloc ();
      else
	delts[j] = 0;

      srcp1 = EBITSET_WORDS (selt1);
      srcp2 = EBITSET_WORDS (selt2);
      dstp = EBITSET_WORDS (delt);
      switch (op)
	{
	case BITSET_OP_OR:
	  for (i = 0; i < EBITSET_ELT_WORDS; i++, dstp++)
	    {
	      bitset_word tmp = *srcp1++ | *srcp2++;

	      if (*dstp != tmp)
		{
		  changed = 1;
		  *dstp = tmp;
		}
	    }
	  break;

	case BITSET_OP_AND:
	  for (i = 0; i < EBITSET_ELT_WORDS; i++, dstp++)
	    {
	      bitset_word tmp = *srcp1++ & *srcp2++;

	      if (*dstp != tmp)
		{
		  changed = 1;
		  *dstp = tmp;
		}
	    }
	  break;

	case BITSET_OP_XOR:
	  for (i = 0; i < EBITSET_ELT_WORDS; i++, dstp++)
	    {
	      bitset_word tmp = *srcp1++ ^ *srcp2++;

	      if (*dstp != tmp)
		{
		  changed = 1;
		  *dstp = tmp;
		}
	    }
	  break;

	case BITSET_OP_ANDN:
	  for (i = 0; i < EBITSET_ELT_WORDS; i++, dstp++)
	    {
	      bitset_word tmp = *srcp1++ & ~(*srcp2++);

	      if (*dstp != tmp)
		{
		  changed = 1;
		  *dstp = tmp;
		}
	    }
	  break;

	default:
	  abort ();
	}

      if (!ebitset_elt_zero_p (delt))
	{
	  ebitset_elt_add (dst, delt, j);
	}
      else
	{
	  ebitset_elt_free (delt);
	}
    }

  /* If we have elements of DST left over, free them all.  */
  for (; j < dsize; j++)
    {
      ebitset_elt *delt;

      changed = 1;

      delt = delts[j];

      if (delt)
	ebitset_elt_remove (dst, j);
    }

  EBITSET_NONZERO_SET (dst);
  return changed;
}


/* Vector of operations for linked-list bitsets.  */
struct bitset_ops_struct ebitset_ops = {
  ebitset_set,
  ebitset_reset,
  ebitset_test,
  ebitset_size,
  ebitset_op1,
  ebitset_op2,
  ebitset_op3,
  bitset_op4,
  ebitset_list,
  ebitset_reverse_list,
  ebitset_free,
  BITSET_TABLE
};


/* Return size of initial structure.  */
int
ebitset_bytes (n_bits)
     bitset_bindex n_bits ATTRIBUTE_UNUSED;
{
  return sizeof (struct bitset_struct);
}


/* Initialize a bitset.  */

bitset
ebitset_init (bset, n_bits)
     bitset bset;
     bitset_bindex n_bits;
{
  unsigned int size;

  bset->b.ops = &ebitset_ops;

  bset->b.csize = EBITSET_ELT_WORDS;

  EBITSET_OP_ZERO_SET (bset);

  size = n_bits ? (n_bits + EBITSET_ELT_BITS - 1) / EBITSET_ELT_BITS
    : EBITSET_INITIAL_SIZE;

  EBITSET_SIZE (bset) = 0;
  EBITSET_ELTS (bset) = 0;
  ebitset_elts_grow (bset, size);

  return bset;
}


void
ebitset_release_memory ()
{
  ebitset_free_list = 0;
  if (ebitset_obstack_init)
    {
      ebitset_obstack_init = 0;
      obstack_free (&ebitset_obstack, NULL);
    }
}