Add native Windows binary for bison.

bison/src/bison/2.4.1/bison-2.4.1-src/lib/lbitset.c

+/* Functions to support link list bitsets.
+   Copyright (C) 2002, 2003, 2004, 2006 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 3 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, see <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+#include "lbitset.h"
+
+#include "obstack.h"
+#include <stddef.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+/* This file implements linked-list bitsets.  These bitsets can be of
+   arbitrary length and are more efficient than arrays of bits for
+   large sparse sets.
+
+   Usually if all the bits in an element are zero we remove the element
+   from the list.  However, a side effect of the bit caching is that we
+   do not always notice when an element becomes zero.  Hence the
+   lbitset_weed function which removes zero elements.  */
+
+
+/* Number of words to use for each element.  The larger the value the
+   greater the size of the cache and the shorter the time to find a given bit
+   but the more memory wasted for sparse bitsets and the longer the time
+   to search for set bits.
+
+   The routines that dominate timing profiles are lbitset_elt_find
+   and lbitset_elt_link, especially when accessing the bits randomly.  */
+
+#define LBITSET_ELT_WORDS 2
+
+typedef bitset_word lbitset_word;
+
+#define LBITSET_WORD_BITS BITSET_WORD_BITS
+
+/* Number of bits stored in each element.  */
+#define LBITSET_ELT_BITS \
+  ((unsigned int) (LBITSET_ELT_WORDS * LBITSET_WORD_BITS))
+
+/* Lbitset element.   We use an array of bits for each element.
+   These are linked together in a doubly-linked list.  */
+typedef struct lbitset_elt_struct
+{
+  struct lbitset_elt_struct *next;      /* Next element.  */
+  struct lbitset_elt_struct *prev;      /* Previous element.  */
+  bitset_windex index;  /* bitno / BITSET_WORD_BITS.  */
+  bitset_word words[LBITSET_ELT_WORDS]; /* Bits that are set.  */
+}
+lbitset_elt;
+
+
+enum lbitset_find_mode
+  { LBITSET_FIND, LBITSET_CREATE, LBITSET_SUBST };
+
+static lbitset_elt lbitset_zero_elts[3]; /* Elements of all zero bits.  */
+
+/* Obstack to allocate bitset elements from.  */
+static struct obstack lbitset_obstack;
+static bool lbitset_obstack_init = false;
+static lbitset_elt *lbitset_free_list;  /* Free list of bitset elements.  */
+
+extern void debug_lbitset (bitset);
+
+#define LBITSET_CURRENT1(X) \
+  ((lbitset_elt *) (void *) ((char *) (X) - offsetof (lbitset_elt, words)))
+
+#define LBITSET_CURRENT(X) LBITSET_CURRENT1((X)->b.cdata)
+
+#define LBITSET_HEAD(X) ((X)->l.head)
+#define LBITSET_TAIL(X) ((X)->l.tail)
+
+/* Allocate a lbitset element.  The bits are not cleared.  */
+static inline lbitset_elt *
+lbitset_elt_alloc (void)
+{
+  lbitset_elt *elt;
+
+  if (lbitset_free_list != 0)
+    {
+      elt = lbitset_free_list;
+      lbitset_free_list = elt->next;
+    }
+  else
+    {
+      if (!lbitset_obstack_init)
+        {
+          lbitset_obstack_init = true;
+
+          /* 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 (&lbitset_obstack, OBSTACK_CHUNK_SIZE,
+                                      __alignof__ (lbitset_elt),
+                                      OBSTACK_CHUNK_ALLOC,
+                                      OBSTACK_CHUNK_FREE);
+        }
+
+      /* Perhaps we should add a number of new elements to the free
+         list.  */
+      elt = (lbitset_elt *) obstack_alloc (&lbitset_obstack,
+                                           sizeof (lbitset_elt));
+    }
+
+  return elt;
+}
+
+
+/* Allocate a lbitset element.  The bits are cleared.  */
+static inline lbitset_elt *
+lbitset_elt_calloc (void)
+{
+  lbitset_elt *elt;
+
+  elt = lbitset_elt_alloc ();
+  memset (elt->words, 0, sizeof (elt->words));
+  return elt;
+}
+
+
+static inline void
+lbitset_elt_free (lbitset_elt *elt)
+{
+  elt->next = lbitset_free_list;
+  lbitset_free_list = elt;
+}
+
+
+/* Unlink element ELT from bitset BSET.  */
+static inline void
+lbitset_elt_unlink (bitset bset, lbitset_elt *elt)
+{
+  lbitset_elt *next = elt->next;
+  lbitset_elt *prev = elt->prev;
+
+  if (prev)
+    prev->next = next;
+
+  if (next)
+    next->prev = prev;
+
+  if (LBITSET_HEAD (bset) == elt)
+    LBITSET_HEAD (bset) = next;
+  if (LBITSET_TAIL (bset) == elt)
+    LBITSET_TAIL (bset) = prev;
+
+  /* Update cache pointer.  Since the first thing we try is to insert
+     before current, make current the next entry in preference to the
+     previous.  */
+  if (LBITSET_CURRENT (bset) == elt)
+    {
+      if (next)
+        {
+          bset->b.cdata = next->words;
+          bset->b.cindex = next->index;
+        }
+      else if (prev)
+        {
+          bset->b.cdata = prev->words;
+          bset->b.cindex = prev->index;
+        }
+      else
+        {
+          bset->b.csize = 0;
+          bset->b.cdata = 0;
+        }
+    }
+
+  lbitset_elt_free (elt);
+}
+
+
+/* Cut the chain of bitset BSET before element ELT and free the
+   elements.  */
+static inline void
+lbitset_prune (bitset bset, lbitset_elt *elt)
+{
+  lbitset_elt *next;
+
+  if (!elt)
+    return;
+
+  if (elt->prev)
+    {
+      LBITSET_TAIL (bset) = elt->prev;
+      bset->b.cdata = elt->prev->words;
+      bset->b.cindex = elt->prev->index;
+      elt->prev->next = 0;
+    }
+  else
+    {
+      LBITSET_HEAD (bset) = 0;
+      LBITSET_TAIL (bset) = 0;
+      bset->b.cdata = 0;
+      bset->b.csize = 0;
+    }
+
+  for (; elt; elt = next)
+    {
+      next = elt->next;
+      lbitset_elt_free (elt);
+    }
+}
+
+
+/* Are all bits in an element zero?  */
+static inline bool
+lbitset_elt_zero_p (lbitset_elt *elt)
+{
+  int i;
+
+  for (i = 0; i < LBITSET_ELT_WORDS; i++)
+    if (elt->words[i])
+      return false;
+
+  return true;
+}
+
+
+/* Link the bitset element into the current bitset linked list.  */
+static inline void
+lbitset_elt_link (bitset bset, lbitset_elt *elt)
+{
+  bitset_windex windex = elt->index;
+  lbitset_elt *ptr;
+  lbitset_elt *current;
+
+  if (bset->b.csize)
+    current = LBITSET_CURRENT (bset);
+  else
+    current = LBITSET_HEAD (bset);
+
+  /* If this is the first and only element, add it in.  */
+  if (LBITSET_HEAD (bset) == 0)
+    {
+      elt->next = elt->prev = 0;
+      LBITSET_HEAD (bset) = elt;
+      LBITSET_TAIL (bset) = elt;
+    }
+
+  /* If this index is less than that of the current element, it goes
+     somewhere before the current element.  */
+  else if (windex < bset->b.cindex)
+    {
+      for (ptr = current;
+           ptr->prev && ptr->prev->index > windex; ptr = ptr->prev)
+        continue;
+
+      if (ptr->prev)
+        ptr->prev->next = elt;
+      else
+        LBITSET_HEAD (bset) = elt;
+
+      elt->prev = ptr->prev;
+      elt->next = ptr;
+      ptr->prev = elt;
+    }
+
+  /* Otherwise, it must go somewhere after the current element.  */
+  else
+    {
+      for (ptr = current;
+           ptr->next && ptr->next->index < windex; ptr = ptr->next)
+        continue;
+
+      if (ptr->next)
+        ptr->next->prev = elt;
+      else
+        LBITSET_TAIL (bset) = elt;
+
+      elt->next = ptr->next;
+      elt->prev = ptr;
+      ptr->next = elt;
+    }
+
+  /* Set up so this is the first element searched.  */
+  bset->b.cindex = windex;
+  bset->b.csize = LBITSET_ELT_WORDS;
+  bset->b.cdata = elt->words;
+}
+
+
+static lbitset_elt *
+lbitset_elt_find (bitset bset, bitset_windex windex,
+                  enum lbitset_find_mode mode)
+{
+  lbitset_elt *elt;
+  lbitset_elt *current;
+
+  if (bset->b.csize)
+    {
+      current = LBITSET_CURRENT (bset);
+      /* Check if element is the cached element.  */
+      if ((windex - bset->b.cindex) < bset->b.csize)
+        return current;
+    }
+  else
+    {
+      current = LBITSET_HEAD (bset);
+    }
+
+  if (current)
+    {
+      if (windex < bset->b.cindex)
+        {
+          for (elt = current;
+               elt->prev && elt->index > windex; elt = elt->prev)
+            continue;
+        }
+      else
+        {
+          for (elt = current;
+               elt->next && (elt->index + LBITSET_ELT_WORDS - 1) < windex;
+               elt = elt->next)
+            continue;
+        }
+
+      /* ELT is the nearest to the one we want.  If it's not the one
+         we want, the one we want does not exist.  */
+      if (elt && (windex - elt->index) < LBITSET_ELT_WORDS)
+        {
+          bset->b.cindex = elt->index;
+          bset->b.csize = LBITSET_ELT_WORDS;
+          bset->b.cdata = elt->words;
+          return elt;
+        }
+    }
+
+  switch (mode)
+    {
+    default:
+      abort ();
+
+    case LBITSET_FIND:
+      return 0;
+
+    case LBITSET_CREATE:
+      windex -= windex % LBITSET_ELT_WORDS;
+
+      elt = lbitset_elt_calloc ();
+      elt->index = windex;
+      lbitset_elt_link (bset, elt);
+      return elt;
+
+    case LBITSET_SUBST:
+      return &lbitset_zero_elts[0];
+    }
+}
+
+
+/* Weed out the zero elements from the list.  */
+static inline void
+lbitset_weed (bitset bset)
+{
+  lbitset_elt *elt;
+  lbitset_elt *next;
+
+  for (elt = LBITSET_HEAD (bset); elt; elt = next)
+    {
+      next = elt->next;
+      if (lbitset_elt_zero_p (elt))
+        lbitset_elt_unlink (bset, elt);
+    }
+}
+
+
+/* Set all bits in the bitset to zero.  */
+static void
+lbitset_zero (bitset bset)
+{
+  lbitset_elt *head;
+
+  head = LBITSET_HEAD (bset);
+  if (!head)
+    return;
+
+  /* Clear a bitset by freeing the linked list at the head element.  */
+  lbitset_prune (bset, head);
+}
+
+
+/* Is DST == SRC?  */
+static inline bool
+lbitset_equal_p (bitset dst, bitset src)
+{
+  lbitset_elt *selt;
+  lbitset_elt *delt;
+  int j;
+
+  if (src == dst)
+    return true;
+
+  lbitset_weed (src);
+  lbitset_weed (dst);
+  for (selt = LBITSET_HEAD (src), delt = LBITSET_HEAD (dst);
+       selt && delt; selt = selt->next, delt = delt->next)
+    {
+      if (selt->index != delt->index)
+        return false;
+
+      for (j = 0; j < LBITSET_ELT_WORDS; j++)
+        if (delt->words[j] != selt->words[j])
+          return false;
+    }
+  return !selt && !delt;
+}
+
+
+/* Copy bits from bitset SRC to bitset DST.  */
+static inline void
+lbitset_copy (bitset dst, bitset src)
+{
+  lbitset_elt *elt;
+  lbitset_elt *head;
+  lbitset_elt *prev;
+  lbitset_elt *tmp;
+
+  if (src == dst)
+    return;
+
+  lbitset_zero (dst);
+
+  head = LBITSET_HEAD (src);
+  if (!head)
+    return;
+
+  prev = 0;
+  for (elt = head; elt; elt = elt->next)
+    {
+      tmp = lbitset_elt_alloc ();
+      tmp->index = elt->index;
+      tmp->prev = prev;
+      tmp->next = 0;
+      if (prev)
+        prev->next = tmp;
+      else
+        LBITSET_HEAD (dst) = tmp;
+      prev = tmp;
+
+      memcpy (tmp->words, elt->words, sizeof (elt->words));
+    }
+  LBITSET_TAIL (dst) = tmp;
+
+  dst->b.csize = LBITSET_ELT_WORDS;
+  dst->b.cdata = LBITSET_HEAD (dst)->words;
+  dst->b.cindex = LBITSET_HEAD (dst)->index;
+}
+
+
+/* Copy bits from bitset SRC to bitset DST.  Return true if
+   bitsets different.  */
+static inline bool
+lbitset_copy_cmp (bitset dst, bitset src)
+{
+  if (src == dst)
+    return false;
+
+  if (!LBITSET_HEAD (dst))
+    {
+      lbitset_copy (dst, src);
+      return LBITSET_HEAD (src) != 0;
+    }
+
+  if (lbitset_equal_p (dst, src))
+    return false;
+
+  lbitset_copy (dst, src);
+  return true;
+}
+
+
+static bitset_bindex
+lbitset_resize (bitset src, bitset_bindex size)
+{
+    BITSET_NBITS_ (src) = size;
+
+    /* Need to prune any excess bits.  FIXME.  */
+    return size;
+}
+
+/* Set bit BITNO in bitset DST.  */
+static void
+lbitset_set (bitset dst, bitset_bindex bitno)
+{
+  bitset_windex windex = bitno / BITSET_WORD_BITS;
+
+  lbitset_elt_find (dst, windex, LBITSET_CREATE);
+
+  dst->b.cdata[windex - dst->b.cindex] |=
+    (bitset_word) 1 << (bitno % BITSET_WORD_BITS);
+}
+
+
+/* Reset bit BITNO in bitset DST.  */
+static void
+lbitset_reset (bitset dst, bitset_bindex bitno)
+{
+  bitset_windex windex = bitno / BITSET_WORD_BITS;
+
+  if (!lbitset_elt_find (dst, windex, LBITSET_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 unlink it now...  */
+}
+
+
+/* Test bit BITNO in bitset SRC.  */
+static bool
+lbitset_test (bitset src, bitset_bindex bitno)
+{
+  bitset_windex windex = bitno / BITSET_WORD_BITS;
+
+  return (lbitset_elt_find (src, windex, LBITSET_FIND)
+          && ((src->b.cdata[windex - src->b.cindex]
+               >> (bitno % BITSET_WORD_BITS))
+              & 1));
+}
+
+
+static void
+lbitset_free (bitset bset)
+{
+  lbitset_zero (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 bitset_bindex
+lbitset_list_reverse (bitset bset, bitset_bindex *list,
+                      bitset_bindex num, bitset_bindex *next)
+{
+  bitset_bindex rbitno;
+  bitset_bindex bitno;
+  unsigned int bcount;
+  bitset_bindex boffset;
+  bitset_windex windex;
+  bitset_bindex count;
+  lbitset_elt *elt;
+  bitset_word word;
+  bitset_bindex n_bits;
+
+  elt = LBITSET_TAIL (bset);
+  if (!elt)
+    return 0;
+
+  n_bits = (elt->index + LBITSET_ELT_WORDS) * BITSET_WORD_BITS;
+  rbitno = *next;
+
+  if (rbitno >= n_bits)
+    return 0;
+
+  bitno = n_bits - (rbitno + 1);
+
+  windex = bitno / BITSET_WORD_BITS;
+
+  /* Skip back to starting element.  */
+  for (; elt && elt->index > windex; elt = elt->prev)
+    continue;
+
+  if (!elt)
+    return 0;
+
+  if (windex >= elt->index + LBITSET_ELT_WORDS)
+    {
+      /* We are trying to start in no-mans land so start
+         at end of current elt.  */
+      bcount = BITSET_WORD_BITS - 1;
+      windex = elt->index + LBITSET_ELT_WORDS - 1;
+    }
+  else
+    {
+      bcount = bitno % BITSET_WORD_BITS;
+    }
+
+  count = 0;
+  boffset = windex * BITSET_WORD_BITS;
+
+  /* If num is 1, we could speed things up with a binary search
+     of the word of interest.  */
+
+  while (elt)
+    {
+      bitset_word *srcp = elt->words;
+
+      for (; (windex - elt->index) < LBITSET_ELT_WORDS;
+           windex--, boffset -= BITSET_WORD_BITS,
+             bcount = BITSET_WORD_BITS - 1)
+        {
+          word =
+            srcp[windex - elt->index] << (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;
+            }
+        }
+
+      elt = elt->prev;
+      if (elt)
+        {
+          windex = elt->index + LBITSET_ELT_WORDS - 1;
+          boffset = windex * BITSET_WORD_BITS;
+        }
+    }
+
+  *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 bitset_bindex
+lbitset_list (bitset bset, bitset_bindex *list,
+              bitset_bindex num, bitset_bindex *next)
+{
+  bitset_bindex bitno;
+  bitset_windex windex;
+  bitset_bindex count;
+  lbitset_elt *elt;
+  lbitset_elt *head;
+  bitset_word word;
+
+  head = LBITSET_HEAD (bset);
+  if (!head)
+    return 0;
+
+  bitno = *next;
+  count = 0;
+
+  if (!bitno)
+    {
+      /* This is the most common case.  */
+
+      /* Start with the first element.  */
+      elt = head;
+      windex = elt->index;
+      bitno = windex * BITSET_WORD_BITS;
+    }
+  else
+    {
+      windex = bitno / BITSET_WORD_BITS;
+
+      /* Skip to starting element.  */
+      for (elt = head;
+           elt && (elt->index + LBITSET_ELT_WORDS - 1) < windex;
+           elt = elt->next)
+        continue;
+
+      if (!elt)
+        return 0;
+
+      if (windex < elt->index)
+        {
+          windex = elt->index;
+          bitno = windex * BITSET_WORD_BITS;
+        }
+      else
+        {
+          bitset_word *srcp = elt->words;
+
+          /* We are starting within an element.  */
+
+          for (; (windex - elt->index) < LBITSET_ELT_WORDS; windex++)
+            {
+              word = srcp[windex - elt->index] >> (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;
+            }
+
+          elt = elt->next;
+          if (elt)
+            {
+              windex = elt->index;
+              bitno = windex * BITSET_WORD_BITS;
+            }
+        }
+    }
+
+
+  /* If num is 1, we could speed things up with a binary search
+     of the word of interest.  */
+
+  while (elt)
+    {
+      int i;
+      bitset_word *srcp = elt->words;
+
+      if ((count + LBITSET_ELT_BITS) < num)
+        {
+          /* The coast is clear, plant boot!  */
+
+#if LBITSET_ELT_WORDS == 2
+          word = srcp[0];
+          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;
+                }
+            }
+          windex++;
+          bitno = windex * BITSET_WORD_BITS;
+
+          word = srcp[1];
+          if (word)
+            {
+              if (!(word & 0xffff))
+                {
+                  word >>= 16;
+                  bitno += 16;
+                }
+              for (; word; bitno++)
+                {
+                  if (word & 1)
+                    list[count++] = bitno;
+                  word >>= 1;
+                }
+            }
+          windex++;
+          bitno = windex * BITSET_WORD_BITS;
+#else
+          for (i = 0; i < LBITSET_ELT_WORDS; i++)
+            {
+              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;
+                    }
+                }
+              windex++;
+              bitno = windex * BITSET_WORD_BITS;
+            }
+#endif
+        }
+      else
+        {
+          /* Tread more carefully since we need to check
+             if array overflows.  */
+
+          for (i = 0; i < LBITSET_ELT_WORDS; i++)
+            {
+              for (word = srcp[i]; word; bitno++)
+                {
+                  if (word & 1)
+                    {
+                      list[count++] = bitno;
+                      if (count >= num)
+                        {
+                          *next = bitno + 1;
+                          return count;
+                        }
+                    }
+                  word >>= 1;
+                }
+              windex++;
+              bitno = windex * BITSET_WORD_BITS;
+            }
+        }
+
+      elt = elt->next;
+      if (elt)
+        {
+          windex = elt->index;
+          bitno = windex * BITSET_WORD_BITS;
+        }
+    }
+
+  *next = bitno;
+  return count;
+}
+
+
+static bool
+lbitset_empty_p (bitset dst)
+{
+  lbitset_elt *elt;
+  lbitset_elt *next;
+
+  for (elt = LBITSET_HEAD (dst); elt; elt = next)
+    {
+      next = elt->next;
+      if (!lbitset_elt_zero_p (elt))
+        return 0;
+      /* Weed as we go.  */
+      lbitset_elt_unlink (dst, elt);
+    }
+
+  return 1;
+}
+
+
+/* Ensure that any unused bits within the last element are clear.  */
+static inline void
+lbitset_unused_clear (bitset dst)
+{
+  unsigned int last_bit;
+  bitset_bindex n_bits;
+
+  n_bits = BITSET_SIZE_ (dst);
+  last_bit = n_bits % LBITSET_ELT_BITS;
+
+  if (last_bit)
+    {
+      lbitset_elt *elt;
+      bitset_windex windex;
+      bitset_word *srcp;
+
+      elt = LBITSET_TAIL (dst);
+      srcp = elt->words;
+      windex = n_bits / BITSET_WORD_BITS;
+
+      srcp[windex - elt->index] &= ((bitset_word) 1 << last_bit) - 1;
+      windex++;
+
+      for (; (windex - elt->index) < LBITSET_ELT_WORDS; windex++)
+        srcp[windex - elt->index] = 0;
+    }
+}
+
+
+static void
+lbitset_ones (bitset dst)
+{
+  bitset_windex i;
+  bitset_windex windex;
+  lbitset_elt *elt;
+
+  /* This is a decidedly unfriendly operation for a linked list
+      bitset!  It makes a sparse bitset become dense.  An alternative
+      is to have a flag that indicates that the bitset stores the
+      complement of what it indicates.  */
+
+  windex = (BITSET_SIZE_ (dst) + BITSET_WORD_BITS - 1) / BITSET_WORD_BITS;
+
+  for (i = 0; i < windex; i += LBITSET_ELT_WORDS)
+    {
+      /* Create new elements if they cannot be found.  */
+      elt = lbitset_elt_find (dst, i, LBITSET_CREATE);
+      memset (elt->words, -1, sizeof (elt->words));
+    }
+
+  lbitset_unused_clear (dst);
+}
+
+
+static void
+lbitset_not (bitset dst, bitset src)
+{
+  lbitset_elt *elt;
+  lbitset_elt *selt;
+  lbitset_elt *delt;
+  bitset_windex i;
+  unsigned int j;
+  bitset_windex windex;
+
+  /* This is another unfriendly operation for a linked list
+     bitset!  */
+  elt = LBITSET_TAIL (dst);
+
+  windex = (BITSET_SIZE_ (dst) + BITSET_WORD_BITS - 1) / BITSET_WORD_BITS;
+
+  for (i = 0; i < windex; i += LBITSET_ELT_WORDS)
+    {
+      /* Create new elements for dst if they cannot be found
+         or substitute zero elements if src elements not found.  */
+      selt = lbitset_elt_find (src, i, LBITSET_SUBST);
+      delt = lbitset_elt_find (dst, i, LBITSET_CREATE);
+
+      for (j = 0; j < LBITSET_ELT_WORDS; j++)
+        delt->words[j] = ~selt->words[j];
+    }
+  lbitset_unused_clear (dst);
+  lbitset_weed (dst);
+  return;
+}
+
+
+/* Is DST == DST | SRC?  */
+static bool
+lbitset_subset_p (bitset dst, bitset src)
+{
+  lbitset_elt *selt;
+  lbitset_elt *delt;
+  unsigned int j;
+
+  for (selt = LBITSET_HEAD (src), delt = LBITSET_HEAD (dst);
+       selt || delt; selt = selt->next, delt = delt->next)
+    {
+      if (!selt)
+        selt = &lbitset_zero_elts[0];
+      else if (!delt)
+        delt = &lbitset_zero_elts[0];
+      else if (selt->index != delt->index)
+        {
+          if (selt->index < delt->index)
+            {
+              lbitset_zero_elts[2].next = delt;
+              delt = &lbitset_zero_elts[2];
+            }
+          else
+            {
+              lbitset_zero_elts[1].next = selt;
+              selt = &lbitset_zero_elts[1];
+            }
+        }
+
+      for (j = 0; j < LBITSET_ELT_WORDS; j++)
+        if (delt->words[j] != (selt->words[j] | delt->words[j]))
+          return false;
+    }
+  return true;
+}
+
+
+/* Is DST & SRC == 0?  */
+static bool
+lbitset_disjoint_p (bitset dst, bitset src)
+{
+  lbitset_elt *selt;
+  lbitset_elt *delt;
+  unsigned int j;
+
+  for (selt = LBITSET_HEAD (src), delt = LBITSET_HEAD (dst);
+       selt && delt; selt = selt->next, delt = delt->next)
+    {
+      if (selt->index != delt->index)
+        {
+          if (selt->index < delt->index)
+            {
+              lbitset_zero_elts[2].next = delt;
+              delt = &lbitset_zero_elts[2];
+            }
+          else
+            {
+              lbitset_zero_elts[1].next = selt;
+              selt = &lbitset_zero_elts[1];
+            }
+          /* Since the elements are different, there is no
+             intersection of these elements.  */
+          continue;
+        }
+
+      for (j = 0; j < LBITSET_ELT_WORDS; j++)
+        if (selt->words[j] & delt->words[j])
+          return false;
+    }
+  return true;
+}
+
+
+static bool
+lbitset_op3_cmp (bitset dst, bitset src1, bitset src2, enum bitset_ops op)
+{
+  lbitset_elt *selt1 = LBITSET_HEAD (src1);
+  lbitset_elt *selt2 = LBITSET_HEAD (src2);
+  lbitset_elt *delt = LBITSET_HEAD (dst);
+  bitset_windex windex1;
+  bitset_windex windex2;
+  bitset_windex windex;
+  lbitset_elt *stmp1;
+  lbitset_elt *stmp2;
+  lbitset_elt *dtmp;
+  bitset_word *srcp1;
+  bitset_word *srcp2;
+  bitset_word *dstp;
+  bool changed = false;
+  unsigned int i;
+
+  LBITSET_HEAD (dst) = 0;
+  dst->b.csize = 0;
+
+  windex1 = (selt1) ? selt1->index : BITSET_WINDEX_MAX;
+  windex2 = (selt2) ? selt2->index : BITSET_WINDEX_MAX;
+
+  while (selt1 || selt2)
+    {
+      /* Figure out whether we need to substitute zero elements for
+         missing links.  */
+      if (windex1 == windex2)
+        {
+          windex = windex1;
+          stmp1 = selt1;
+          stmp2 = selt2;
+          selt1 = selt1->next;
+          windex1 = (selt1) ? selt1->index : BITSET_WINDEX_MAX;
+          selt2 = selt2->next;
+          windex2 = (selt2) ? selt2->index : BITSET_WINDEX_MAX;
+        }
+      else if (windex1 < windex2)
+        {
+          windex = windex1;
+          stmp1 = selt1;
+          stmp2 = &lbitset_zero_elts[0];
+          selt1 = selt1->next;
+          windex1 = (selt1) ? selt1->index : BITSET_WINDEX_MAX;
+        }
+      else
+        {
+          windex = windex2;
+          stmp1 = &lbitset_zero_elts[0];
+          stmp2 = selt2;
+          selt2 = selt2->next;
+          windex2 = (selt2) ? selt2->index : BITSET_WINDEX_MAX;
+        }
+
+      /* Find the appropriate element from DST.  Begin by discarding
+         elements that we've skipped.  */
+      while (delt && delt->index < windex)
+        {
+          changed = true;
+          dtmp = delt;
+          delt = delt->next;
+          lbitset_elt_free (dtmp);
+        }
+      if (delt && delt->index == windex)
+        {
+          dtmp = delt;
+          delt = delt->next;
+        }
+      else
+        dtmp = lbitset_elt_calloc ();
+
+      /* Do the operation, and if any bits are set, link it into the
+         linked list.  */
+      srcp1 = stmp1->words;
+      srcp2 = stmp2->words;
+      dstp = dtmp->words;
+      switch (op)
+        {
+        default:
+          abort ();
+
+        case BITSET_OP_OR:
+          for (i = 0; i < LBITSET_ELT_WORDS; i++, dstp++)
+            {
+              bitset_word tmp = *srcp1++ | *srcp2++;
+
+              if (*dstp != tmp)
+                {
+                  changed = true;
+                  *dstp = tmp;
+                }
+            }
+          break;
+
+        case BITSET_OP_AND:
+          for (i = 0; i < LBITSET_ELT_WORDS; i++, dstp++)
+            {
+              bitset_word tmp = *srcp1++ & *srcp2++;
+
+              if (*dstp != tmp)
+                {
+                  changed = true;
+                  *dstp = tmp;
+                }
+            }
+          break;
+
+        case BITSET_OP_XOR:
+          for (i = 0; i < LBITSET_ELT_WORDS; i++, dstp++)
+            {
+              bitset_word tmp = *srcp1++ ^ *srcp2++;
+
+              if (*dstp != tmp)
+                {
+                  changed = true;
+                  *dstp = tmp;
+                }
+            }
+          break;
+
+        case BITSET_OP_ANDN:
+          for (i = 0; i < LBITSET_ELT_WORDS; i++, dstp++)
+            {
+              bitset_word tmp = *srcp1++ & ~(*srcp2++);
+
+              if (*dstp != tmp)
+                {
+                  changed = true;
+                  *dstp = tmp;
+                }
+            }
+          break;
+        }
+
+      if (!lbitset_elt_zero_p (dtmp))
+        {
+          dtmp->index = windex;
+          /* Perhaps this could be optimised...  */
+          lbitset_elt_link (dst, dtmp);
+        }
+      else
+        {
+          lbitset_elt_free (dtmp);
+        }
+    }
+
+  /* If we have elements of DST left over, free them all.  */
+  if (delt)
+    {
+      changed = true;
+      lbitset_prune (dst, delt);
+    }
+
+  return changed;
+}
+
+
+static bool
+lbitset_and_cmp (bitset dst, bitset src1, bitset src2)
+{
+  lbitset_elt *selt1 = LBITSET_HEAD (src1);
+  lbitset_elt *selt2 = LBITSET_HEAD (src2);
+  bool changed;
+
+  if (!selt2)
+    {
+      lbitset_weed (dst);
+      changed = !LBITSET_HEAD (dst);
+      lbitset_zero (dst);
+      return changed;
+    }
+  else if (!selt1)
+    {
+      lbitset_weed (dst);
+      changed = !LBITSET_HEAD (dst);
+      lbitset_zero (dst);
+      return changed;
+    }
+  return lbitset_op3_cmp (dst, src1, src2, BITSET_OP_AND);
+}
+
+
+static void
+lbitset_and (bitset dst, bitset src1, bitset src2)
+{
+  lbitset_and_cmp (dst, src1, src2);
+}
+
+
+static bool
+lbitset_andn_cmp (bitset dst, bitset src1, bitset src2)
+{
+  lbitset_elt *selt1 = LBITSET_HEAD (src1);
+  lbitset_elt *selt2 = LBITSET_HEAD (src2);
+  bool changed;
+
+  if (!selt2)
+    {
+      return lbitset_copy_cmp (dst, src1);
+    }
+  else if (!selt1)
+    {
+      lbitset_weed (dst);
+      changed = !LBITSET_HEAD (dst);
+      lbitset_zero (dst);
+      return changed;
+    }
+  return lbitset_op3_cmp (dst, src1, src2, BITSET_OP_ANDN);
+}
+
+
+static void
+lbitset_andn (bitset dst, bitset src1, bitset src2)
+{
+  lbitset_andn_cmp (dst, src1, src2);
+}
+
+
+static bool
+lbitset_or_cmp (bitset dst, bitset src1, bitset src2)
+{
+  lbitset_elt *selt1 = LBITSET_HEAD (src1);
+  lbitset_elt *selt2 = LBITSET_HEAD (src2);
+
+  if (!selt2)
+    {
+      return lbitset_copy_cmp (dst, src1);
+    }
+  else if (!selt1)
+    {
+      return lbitset_copy_cmp (dst, src2);
+    }
+  return lbitset_op3_cmp (dst, src1, src2, BITSET_OP_OR);
+}
+
+
+static void
+lbitset_or (bitset dst, bitset src1, bitset src2)
+{
+  lbitset_or_cmp (dst, src1, src2);
+}
+
+
+static bool
+lbitset_xor_cmp (bitset dst, bitset src1, bitset src2)
+{
+  lbitset_elt *selt1 = LBITSET_HEAD (src1);
+  lbitset_elt *selt2 = LBITSET_HEAD (src2);
+
+  if (!selt2)
+    {
+      return lbitset_copy_cmp (dst, src1);
+    }
+  else if (!selt1)
+    {
+      return lbitset_copy_cmp (dst, src2);
+    }
+  return lbitset_op3_cmp (dst, src1, src2, BITSET_OP_XOR);
+}
+
+
+static void
+lbitset_xor (bitset dst, bitset src1, bitset src2)
+{
+  lbitset_xor_cmp (dst, src1, src2);
+}
+
+
+
+/* Vector of operations for linked-list bitsets.  */
+struct bitset_vtable lbitset_vtable = {
+  lbitset_set,
+  lbitset_reset,
+  bitset_toggle_,
+  lbitset_test,
+  lbitset_resize,
+  bitset_size_,
+  bitset_count_,
+  lbitset_empty_p,
+  lbitset_ones,
+  lbitset_zero,
+  lbitset_copy,
+  lbitset_disjoint_p,
+  lbitset_equal_p,
+  lbitset_not,
+  lbitset_subset_p,
+  lbitset_and,
+  lbitset_and_cmp,
+  lbitset_andn,
+  lbitset_andn_cmp,
+  lbitset_or,
+  lbitset_or_cmp,
+  lbitset_xor,
+  lbitset_xor_cmp,
+  bitset_and_or_,
+  bitset_and_or_cmp_,
+  bitset_andn_or_,
+  bitset_andn_or_cmp_,
+  bitset_or_and_,
+  bitset_or_and_cmp_,
+  lbitset_list,
+  lbitset_list_reverse,
+  lbitset_free,
+  BITSET_LIST
+};
+
+
+/* Return size of initial structure.  */
+size_t
+lbitset_bytes (bitset_bindex n_bits ATTRIBUTE_UNUSED)
+{
+  return sizeof (struct lbitset_struct);
+}
+
+
+/* Initialize a bitset.  */
+bitset
+lbitset_init (bitset bset, bitset_bindex n_bits ATTRIBUTE_UNUSED)
+{
+  BITSET_NBITS_ (bset) = n_bits;
+  bset->b.vtable = &lbitset_vtable;
+  return bset;
+}
+
+
+void
+lbitset_release_memory (void)
+{
+  lbitset_free_list = 0;
+  if (lbitset_obstack_init)
+    {
+      lbitset_obstack_init = false;
+      obstack_free (&lbitset_obstack, NULL);
+    }
+}
+
+
+/* Function to be called from debugger to debug lbitset.  */
+void
+debug_lbitset (bitset bset)
+{
+  lbitset_elt *elt;
+  unsigned int i;
+
+  if (!bset)
+    return;
+
+  for (elt = LBITSET_HEAD (bset); elt; elt = elt->next)
+    {
+      fprintf (stderr, "Elt %lu\n", (unsigned long int) elt->index);
+      for (i = 0; i < LBITSET_ELT_WORDS; i++)
+        {
+          unsigned int j;
+          bitset_word word;
+
+          word = elt->words[i];
+
+          fprintf (stderr, "  Word %u:", i);
+          for (j = 0; j < LBITSET_WORD_BITS; j++)
+            if ((word & ((bitset_word) 1 << j)))
+              fprintf (stderr, " %u", j);
+          fprintf (stderr, "\n");
+        }
+    }
+}