Add native Windows binary for bison.

bison/src/bison/2.4.1/bison-2.4.1-src/src/lalr.c

+/* Compute lookahead criteria for Bison.
+
+   Copyright (C) 1984, 1986, 1989, 2000, 2001, 2002, 2003, 2004, 2005,
+   2006, 2007 Free Software Foundation, Inc.
+
+   This file is part of Bison, the GNU Compiler Compiler.
+
+   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/>.  */
+
+
+/* Compute how to make the finite state machine deterministic; find
+   which rules need lookahead in each state, and which lookahead
+   tokens they accept.  */
+
+#include <config.h>
+#include "system.h"
+
+#include <bitset.h>
+#include <bitsetv.h>
+#include <quotearg.h>
+
+#include "LR0.h"
+#include "complain.h"
+#include "derives.h"
+#include "getargs.h"
+#include "gram.h"
+#include "lalr.h"
+#include "nullable.h"
+#include "reader.h"
+#include "relation.h"
+#include "symtab.h"
+
+goto_number *goto_map;
+static goto_number ngotos;
+state_number *from_state;
+state_number *to_state;
+
+/* Linked list of goto numbers.  */
+typedef struct goto_list
+{
+  struct goto_list *next;
+  goto_number value;
+} goto_list;
+
+
+/* LA is an NLA by NTOKENS matrix of bits.  LA[l, i] is 1 if the rule
+   LArule[l] is applicable in the appropriate state when the next
+   token is symbol i.  If LA[l, i] and LA[l, j] are both 1 for i != j,
+   it is a conflict.  */
+
+static bitsetv LA = NULL;
+size_t nLA;
+
+
+/* And for the famous F variable, which name is so descriptive that a
+   comment is hardly needed.  <grin>.  */
+static bitsetv F = NULL;
+
+static goto_number **includes;
+static goto_list **lookback;
+
+
+
+
+static void
+set_goto_map (void)
+{
+  state_number s;
+  goto_number *temp_map;
+
+  goto_map = xcalloc (nvars + 1, sizeof *goto_map);
+  temp_map = xnmalloc (nvars + 1, sizeof *temp_map);
+
+  ngotos = 0;
+  for (s = 0; s < nstates; ++s)
+    {
+      transitions *sp = states[s]->transitions;
+      int i;
+      for (i = sp->num - 1; i >= 0 && TRANSITION_IS_GOTO (sp, i); --i)
+        {
+          ngotos++;
+
+          /* Abort if (ngotos + 1) would overflow.  */
+          aver (ngotos != GOTO_NUMBER_MAXIMUM);
+
+          goto_map[TRANSITION_SYMBOL (sp, i) - ntokens]++;
+        }
+    }
+
+  {
+    goto_number k = 0;
+    int i;
+    for (i = ntokens; i < nsyms; i++)
+      {
+        temp_map[i - ntokens] = k;
+        k += goto_map[i - ntokens];
+      }
+
+    for (i = ntokens; i < nsyms; i++)
+      goto_map[i - ntokens] = temp_map[i - ntokens];
+
+    goto_map[nsyms - ntokens] = ngotos;
+    temp_map[nsyms - ntokens] = ngotos;
+  }
+
+  from_state = xcalloc (ngotos, sizeof *from_state);
+  to_state = xcalloc (ngotos, sizeof *to_state);
+
+  for (s = 0; s < nstates; ++s)
+    {
+      transitions *sp = states[s]->transitions;
+      int i;
+      for (i = sp->num - 1; i >= 0 && TRANSITION_IS_GOTO (sp, i); --i)
+        {
+          goto_number k = temp_map[TRANSITION_SYMBOL (sp, i) - ntokens]++;
+          from_state[k] = s;
+          to_state[k] = sp->states[i]->number;
+        }
+    }
+
+  free (temp_map);
+}
+
+
+
+/*----------------------------------------------------------.
+| Map a state/symbol pair into its numeric representation.  |
+`----------------------------------------------------------*/
+
+static goto_number
+map_goto (state_number s0, symbol_number sym)
+{
+  goto_number high;
+  goto_number low;
+  goto_number middle;
+  state_number s;
+
+  low = goto_map[sym - ntokens];
+  high = goto_map[sym - ntokens + 1] - 1;
+
+  for (;;)
+    {
+      aver (low <= high);
+      middle = (low + high) / 2;
+      s = from_state[middle];
+      if (s == s0)
+        return middle;
+      else if (s < s0)
+        low = middle + 1;
+      else
+        high = middle - 1;
+    }
+}
+
+
+static void
+initialize_F (void)
+{
+  goto_number **reads = xnmalloc (ngotos, sizeof *reads);
+  goto_number *edge = xnmalloc (ngotos + 1, sizeof *edge);
+  goto_number nedges = 0;
+
+  goto_number i;
+
+  F = bitsetv_create (ngotos, ntokens, BITSET_FIXED);
+
+  for (i = 0; i < ngotos; i++)
+    {
+      state_number stateno = to_state[i];
+      transitions *sp = states[stateno]->transitions;
+
+      int j;
+      FOR_EACH_SHIFT (sp, j)
+        bitset_set (F[i], TRANSITION_SYMBOL (sp, j));
+
+      for (; j < sp->num; j++)
+        {
+          symbol_number sym = TRANSITION_SYMBOL (sp, j);
+          if (nullable[sym - ntokens])
+            edge[nedges++] = map_goto (stateno, sym);
+        }
+
+      if (nedges == 0)
+        reads[i] = NULL;
+      else
+        {
+          reads[i] = xnmalloc (nedges + 1, sizeof reads[i][0]);
+          memcpy (reads[i], edge, nedges * sizeof edge[0]);
+          reads[i][nedges] = END_NODE;
+          nedges = 0;
+        }
+    }
+
+  relation_digraph (reads, ngotos, &F);
+
+  for (i = 0; i < ngotos; i++)
+    free (reads[i]);
+
+  free (reads);
+  free (edge);
+}
+
+
+static void
+add_lookback_edge (state *s, rule *r, goto_number gotono)
+{
+  int ri = state_reduction_find (s, r);
+  goto_list *sp = xmalloc (sizeof *sp);
+  sp->next = lookback[(s->reductions->lookahead_tokens - LA) + ri];
+  sp->value = gotono;
+  lookback[(s->reductions->lookahead_tokens - LA) + ri] = sp;
+}
+
+
+
+static void
+build_relations (void)
+{
+  goto_number *edge = xnmalloc (ngotos + 1, sizeof *edge);
+  state_number *states1 = xnmalloc (ritem_longest_rhs () + 1, sizeof *states1);
+  goto_number i;
+
+  includes = xnmalloc (ngotos, sizeof *includes);
+
+  for (i = 0; i < ngotos; i++)
+    {
+      int nedges = 0;
+      symbol_number symbol1 = states[to_state[i]]->accessing_symbol;
+      rule **rulep;
+
+      for (rulep = derives[symbol1 - ntokens]; *rulep; rulep++)
+        {
+          bool done;
+          int length = 1;
+          item_number const *rp;
+          state *s = states[from_state[i]];
+          states1[0] = s->number;
+
+          for (rp = (*rulep)->rhs; ! item_number_is_rule_number (*rp); rp++)
+            {
+              s = transitions_to (s->transitions,
+                                  item_number_as_symbol_number (*rp));
+              states1[length++] = s->number;
+            }
+
+          if (!s->consistent)
+            add_lookback_edge (s, *rulep, i);
+
+          length--;
+          done = false;
+          while (!done)
+            {
+              done = true;
+              /* Each rhs ends in a rule number, and there is a
+                 sentinel before the first rhs, so it is safe to
+                 decrement RP here.  */
+              rp--;
+              if (ISVAR (*rp))
+                {
+                  /* Downcasting from item_number to symbol_number.  */
+                  edge[nedges++] = map_goto (states1[--length],
+                                             item_number_as_symbol_number (*rp));
+                  if (nullable[*rp - ntokens])
+                    done = false;
+                }
+            }
+        }
+
+      if (nedges == 0)
+        includes[i] = NULL;
+      else
+        {
+          int j;
+          includes[i] = xnmalloc (nedges + 1, sizeof includes[i][0]);
+          for (j = 0; j < nedges; j++)
+            includes[i][j] = edge[j];
+          includes[i][nedges] = END_NODE;
+        }
+    }
+
+  free (edge);
+  free (states1);
+
+  relation_transpose (&includes, ngotos);
+}
+
+
+
+static void
+compute_FOLLOWS (void)
+{
+  goto_number i;
+
+  relation_digraph (includes, ngotos, &F);
+
+  for (i = 0; i < ngotos; i++)
+    free (includes[i]);
+
+  free (includes);
+}
+
+
+static void
+compute_lookahead_tokens (void)
+{
+  size_t i;
+  goto_list *sp;
+
+  for (i = 0; i < nLA; i++)
+    for (sp = lookback[i]; sp; sp = sp->next)
+      bitset_or (LA[i], LA[i], F[sp->value]);
+
+  /* Free LOOKBACK. */
+  for (i = 0; i < nLA; i++)
+    LIST_FREE (goto_list, lookback[i]);
+
+  free (lookback);
+  bitsetv_free (F);
+}
+
+
+/*----------------------------------------------------.
+| Count the number of lookahead tokens required for S |
+| (N_LOOKAHEAD_TOKENS member).                        |
+`----------------------------------------------------*/
+
+static int
+state_lookahead_tokens_count (state *s)
+{
+  int n_lookahead_tokens = 0;
+  reductions *rp = s->reductions;
+  transitions *sp = s->transitions;
+
+  /* We need a lookahead either to distinguish different
+     reductions (i.e., there are two or more), or to distinguish a
+     reduction from a shift.  Otherwise, it is straightforward,
+     and the state is `consistent'.  There is no need to check that
+     transition 0 hasn't been disabled before checking if it is a
+     shift since transitions are only disabled during conflict
+     resolution, and that hasn't happened yet.  */
+  aver (sp->num == 0 || !TRANSITION_IS_DISABLED (sp, 0));
+  if (rp->num > 1
+      || (rp->num == 1 && sp->num && TRANSITION_IS_SHIFT (sp, 0)))
+    n_lookahead_tokens += rp->num;
+  else
+    s->consistent = 1;
+
+  return n_lookahead_tokens;
+}
+
+
+/*----------------------------------------------------.
+| Compute LA, NLA, and the lookahead_tokens members.  |
+`----------------------------------------------------*/
+
+static void
+initialize_LA (void)
+{
+  state_number i;
+  bitsetv pLA;
+
+  /* Compute the total number of reductions requiring a lookahead.  */
+  nLA = 0;
+  for (i = 0; i < nstates; i++)
+    nLA += state_lookahead_tokens_count (states[i]);
+  /* Avoid having to special case 0.  */
+  if (!nLA)
+    nLA = 1;
+
+  pLA = LA = bitsetv_create (nLA, ntokens, BITSET_FIXED);
+  lookback = xcalloc (nLA, sizeof *lookback);
+
+  /* Initialize the members LOOKAHEAD_TOKENS for each state whose reductions
+     require lookahead tokens.  */
+  for (i = 0; i < nstates; i++)
+    {
+      int count = state_lookahead_tokens_count (states[i]);
+      if (count)
+        {
+          states[i]->reductions->lookahead_tokens = pLA;
+          pLA += count;
+        }
+    }
+}
+
+
+/*---------------------------------------------.
+| Output the lookahead tokens for each state.  |
+`---------------------------------------------*/
+
+static void
+lookahead_tokens_print (FILE *out)
+{
+  state_number i;
+  int j, k;
+  fprintf (out, "Lookahead tokens: BEGIN\n");
+  for (i = 0; i < nstates; ++i)
+    {
+      reductions *reds = states[i]->reductions;
+      bitset_iterator iter;
+      int n_lookahead_tokens = 0;
+
+      if (reds->lookahead_tokens)
+        for (k = 0; k < reds->num; ++k)
+          if (reds->lookahead_tokens[k])
+            ++n_lookahead_tokens;
+
+      fprintf (out, "State %d: %d lookahead tokens\n",
+               i, n_lookahead_tokens);
+
+      if (reds->lookahead_tokens)
+        for (j = 0; j < reds->num; ++j)
+          BITSET_FOR_EACH (iter, reds->lookahead_tokens[j], k, 0)
+          {
+            fprintf (out, "   on %d (%s) -> rule %d\n",
+                     k, symbols[k]->tag,
+                     reds->rules[j]->number);
+          };
+    }
+  fprintf (out, "Lookahead tokens: END\n");
+}
+
+void
+lalr (void)
+{
+  initialize_LA ();
+  set_goto_map ();
+  initialize_F ();
+  build_relations ();
+  compute_FOLLOWS ();
+  compute_lookahead_tokens ();
+
+  if (trace_flag & trace_sets)
+    lookahead_tokens_print (stderr);
+}
+
+
+void
+lalr_update_state_numbers (state_number old_to_new[], state_number nstates_old)
+{
+  goto_number ngotos_reachable = 0;
+  symbol_number nonterminal = 0;
+  aver (nsyms == nvars + ntokens);
+  {
+    goto_number i;
+    for (i = 0; i < ngotos; ++i)
+      {
+        while (i == goto_map[nonterminal])
+          goto_map[nonterminal++] = ngotos_reachable;
+        /* If old_to_new[from_state[i]] = nstates_old, remove this goto
+           entry.  */
+        if (old_to_new[from_state[i]] != nstates_old)
+          {
+            /* from_state[i] is not removed, so it and thus to_state[i] are
+               reachable, so to_state[i] != nstates_old.  */
+            aver (old_to_new[to_state[i]] != nstates_old);
+            from_state[ngotos_reachable] = old_to_new[from_state[i]];
+            to_state[ngotos_reachable] = old_to_new[to_state[i]];
+            ++ngotos_reachable;
+          }
+      }
+  }
+  while (nonterminal <= nvars)
+    {
+      aver (ngotos == goto_map[nonterminal]);
+      goto_map[nonterminal++] = ngotos_reachable;
+    }
+  ngotos = ngotos_reachable;
+}
+
+
+void
+lalr_free (void)
+{
+  state_number s;
+  for (s = 0; s < nstates; ++s)
+    states[s]->reductions->lookahead_tokens = NULL;
+  bitsetv_free (LA);
+}