X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/158e69f984ddc49f0d7febe20234482c8d3cfbb0..c826013fb38c98861ef0fc5d4dc3fb3fb4f555be:/src/lalr.c

diff --git a/src/lalr.c b/src/lalr.c
index f85347a3..6f099a8b 100644
--- a/src/lalr.c
+++ b/src/lalr.c
@@ -1,58 +1,61 @@
-/* Compute look-ahead criteria for bison,
-   Copyright (C) 1984, 1986, 1989, 2000, 2001, 2002
-   Free Software Foundation, Inc.
+/* Compute lookahead criteria for Bison.
+
+   Copyright (C) 1984, 1986, 1989, 2000-2010 Free Software Foundation,
+   Inc.
 
    This file is part of Bison, the GNU Compiler Compiler.
 
-   Bison is free software; you can redistribute it and/or modify
+   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, or (at your option)
-   any later version.
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
 
-   Bison is distributed in the hope that it will be useful,
+   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 Bison; see the file COPYING.  If not, write to
-   the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
-   Boston, MA 02111-1307, USA.  */
+   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
+/* 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 "relation.h"
-#include "quotearg.h"
-#include "symtab.h"
-#include "gram.h"
-#include "reader.h"
+
+#include <bitset.h>
+#include <bitsetv.h>
+#include <quotearg.h>
+
 #include "LR0.h"
 #include "complain.h"
-#include "lalr.h"
-#include "nullable.h"
 #include "derives.h"
 #include "getargs.h"
+#include "gram.h"
+#include "lalr.h"
+#include "muscle-tab.h"
+#include "nullable.h"
+#include "reader.h"
+#include "relation.h"
+#include "symtab.h"
 
-goto_number_t *goto_map = NULL;
-static goto_number_t ngotos = 0;
-state_number_t *from_state = NULL;
-state_number_t *to_state = NULL;
+goto_number *goto_map;
+goto_number ngotos;
+state_number *from_state;
+state_number *to_state;
+bitsetv goto_follows = NULL;
 
 /* Linked list of goto numbers.  */
-typedef struct goto_list_s
+typedef struct goto_list
 {
-  struct goto_list_s *next;
-  goto_number_t value;
-} goto_list_t;
+  struct goto_list *next;
+  goto_number value;
+} goto_list;
 
 
-/* LA is a LR by NTOKENS matrix of bits.  LA[l, i] is 1 if the rule
+/* 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.  */
@@ -61,163 +64,154 @@ 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 goto_number_t **includes;
-static goto_list_t **lookback;
 
 
 
-
-static void
+void
 set_goto_map (void)
 {
-  state_number_t state;
-  goto_number_t *temp_map;
+  state_number s;
+  goto_number *temp_map;
 
-  goto_map = XCALLOC (goto_number_t, nvars + 1) - ntokens;
-  temp_map = XCALLOC (goto_number_t, nvars + 1) - ntokens;
+  goto_map = xcalloc (nvars + 1, sizeof *goto_map);
+  temp_map = xnmalloc (nvars + 1, sizeof *temp_map);
 
   ngotos = 0;
-  for (state = 0; state < nstates; ++state)
+  for (s = 0; s < nstates; ++s)
     {
-      transitions_t *sp = states[state]->transitions;
+      transitions *sp = states[s]->transitions;
       int i;
       for (i = sp->num - 1; i >= 0 && TRANSITION_IS_GOTO (sp, i); --i)
 	{
-	  if (ngotos == GOTO_NUMBER_MAX)
-	    fatal (_("too many gotos (max %d)"), GOTO_NUMBER_MAX);
-
 	  ngotos++;
-	  goto_map[TRANSITION_SYMBOL (sp, i)]++;
+
+	  /* Abort if (ngotos + 1) would overflow.  */
+	  aver (ngotos != GOTO_NUMBER_MAXIMUM);
+
+	  goto_map[TRANSITION_SYMBOL (sp, i) - ntokens]++;
 	}
     }
 
   {
-    int k = 0;
+    goto_number k = 0;
     int i;
     for (i = ntokens; i < nsyms; i++)
       {
-	temp_map[i] = k;
-	k += goto_map[i];
+	temp_map[i - ntokens] = k;
+	k += goto_map[i - ntokens];
       }
 
     for (i = ntokens; i < nsyms; i++)
-      goto_map[i] = temp_map[i];
+      goto_map[i - ntokens] = temp_map[i - ntokens];
 
-    goto_map[nsyms] = ngotos;
-    temp_map[nsyms] = ngotos;
+    goto_map[nsyms - ntokens] = ngotos;
+    temp_map[nsyms - ntokens] = ngotos;
   }
 
-  from_state = XCALLOC (state_number_t, ngotos);
-  to_state = XCALLOC (state_number_t, ngotos);
+  from_state = xcalloc (ngotos, sizeof *from_state);
+  to_state = xcalloc (ngotos, sizeof *to_state);
 
-  for (state = 0; state < nstates; ++state)
+  for (s = 0; s < nstates; ++s)
     {
-      transitions_t *sp = states[state]->transitions;
+      transitions *sp = states[s]->transitions;
       int i;
       for (i = sp->num - 1; i >= 0 && TRANSITION_IS_GOTO (sp, i); --i)
 	{
-	  int k = temp_map[TRANSITION_SYMBOL (sp, i)]++;
-	  from_state[k] = state;
+	  goto_number k = temp_map[TRANSITION_SYMBOL (sp, i) - ntokens]++;
+	  from_state[k] = s;
 	  to_state[k] = sp->states[i]->number;
 	}
     }
 
-  XFREE (temp_map + ntokens);
+  free (temp_map);
 }
 
 
-
-/*----------------------------------------------------------.
-| Map a state/symbol pair into its numeric representation.  |
-`----------------------------------------------------------*/
-
-static int
-map_goto (state_number_t state, symbol_number_t symbol)
+goto_number
+map_goto (state_number s0, symbol_number sym)
 {
-  int high;
-  int low;
-  int middle;
-  state_number_t s;
+  goto_number high;
+  goto_number low;
+  goto_number middle;
+  state_number s;
 
-  low = goto_map[symbol];
-  high = goto_map[symbol + 1] - 1;
+  low = goto_map[sym - ntokens];
+  high = goto_map[sym - ntokens + 1] - 1;
 
-  while (low <= high)
+  for (;;)
     {
+      aver (low <= high);
       middle = (low + high) / 2;
       s = from_state[middle];
-      if (s == state)
+      if (s == s0)
 	return middle;
-      else if (s < state)
+      else if (s < s0)
 	low = middle + 1;
       else
 	high = middle - 1;
     }
-
-  assert (0);
-  /* NOTREACHED */
-  return 0;
 }
 
 
 static void
 initialize_F (void)
 {
-  goto_number_t **reads = XCALLOC (goto_number_t *, ngotos);
-  goto_number_t *edge = XCALLOC (goto_number_t, ngotos + 1);
-  int nedges = 0;
+  goto_number **reads = xnmalloc (ngotos, sizeof *reads);
+  goto_number *edge = xnmalloc (ngotos + 1, sizeof *edge);
+  goto_number nedges = 0;
 
-  int i;
+  goto_number i;
 
-  F = bitsetv_create (ngotos, ntokens, BITSET_FIXED);
+  goto_follows = bitsetv_create (ngotos, ntokens, BITSET_FIXED);
 
   for (i = 0; i < ngotos; i++)
     {
-      state_number_t stateno = to_state[i];
-      transitions_t *sp = states[stateno]->transitions;
+      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));
+	bitset_set (goto_follows[i], TRANSITION_SYMBOL (sp, j));
 
       for (; j < sp->num; j++)
 	{
-	  symbol_number_t symbol = TRANSITION_SYMBOL (sp, j);
-	  if (nullable[symbol])
-	    edge[nedges++] = map_goto (stateno, symbol);
+	  symbol_number sym = TRANSITION_SYMBOL (sp, j);
+	  if (nullable[sym - ntokens])
+	    edge[nedges++] = map_goto (stateno, sym);
 	}
 
-      if (nedges)
+      if (nedges == 0)
+	reads[i] = NULL;
+      else
 	{
-	  reads[i] = XCALLOC (goto_number_t, nedges + 1);
-	  memcpy (reads[i], edge, nedges * sizeof (edge[0]));
-	  reads[i][nedges] = -1;
+	  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);
+  relation_digraph (reads, ngotos, &goto_follows);
 
   for (i = 0; i < ngotos; i++)
-    XFREE (reads[i]);
+    free (reads[i]);
 
-  XFREE (reads);
-  XFREE (edge);
+  free (reads);
+  free (edge);
 }
 
 
 static void
-add_lookback_edge (state_t *state, rule_t *rule, int gotono)
+add_lookback_edge (state *s, rule *r, goto_number gotono)
 {
-  int r = state_reduction_find (state, rule);
-  goto_list_t *sp = XCALLOC (goto_list_t, 1);
-  sp->next = lookback[(state->reductions->lookaheads - LA) + r];
+  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[(state->reductions->lookaheads - LA) + r] = sp;
+  lookback[(s->reductions->lookahead_tokens - LA) + ri] = sp;
 }
 
 
@@ -225,66 +219,70 @@ add_lookback_edge (state_t *state, rule_t *rule, int gotono)
 static void
 build_relations (void)
 {
-  goto_number_t *edge = XCALLOC (goto_number_t, ngotos + 1);
-  state_number_t *states1 = XCALLOC (state_number_t, ritem_longest_rhs () + 1);
-  int i;
+  goto_number *edge = xnmalloc (ngotos + 1, sizeof *edge);
+  state_number *states1 = xnmalloc (ritem_longest_rhs () + 1, sizeof *states1);
+  goto_number i;
 
-  includes = XCALLOC (goto_number_t *, ngotos);
+  includes = xnmalloc (ngotos, sizeof *includes);
 
   for (i = 0; i < ngotos; i++)
     {
       int nedges = 0;
-      symbol_number_t symbol1 = states[to_state[i]]->accessing_symbol;
-      rule_t **rulep;
+      symbol_number symbol1 = states[to_state[i]]->accessing_symbol;
+      rule **rulep;
 
-      for (rulep = derives[symbol1]; *rulep; rulep++)
+      for (rulep = derives[symbol1 - ntokens]; *rulep; rulep++)
 	{
-	  int done;
+	  bool done;
 	  int length = 1;
-	  item_number_t *rp;
-	  state_t *state = states[from_state[i]];
-	  states1[0] = state->number;
+	  item_number const *rp;
+	  state *s = states[from_state[i]];
+	  states1[0] = s->number;
 
-	  for (rp = (*rulep)->rhs; *rp >= 0; rp++)
+	  for (rp = (*rulep)->rhs; ! item_number_is_rule_number (*rp); rp++)
 	    {
-	      state = transitions_to (state->transitions,
-				      item_number_as_symbol_number (*rp));
-	      states1[length++] = state->number;
+	      s = transitions_to (s->transitions,
+				  item_number_as_symbol_number (*rp));
+	      states1[length++] = s->number;
 	    }
 
-	  if (!state->consistent)
-	    add_lookback_edge (state, *rulep, i);
+	  if (!s->consistent)
+	    add_lookback_edge (s, *rulep, i);
 
 	  length--;
-	  done = 0;
+	  done = false;
 	  while (!done)
 	    {
-	      done = 1;
+	      done = true;
+	      /* Each rhs ends in a rule number, and there is a
+		 sentinel (ritem[-1]=0) before the first rhs, so it is safe to
+		 decrement RP here.  */
 	      rp--;
-	      /* JF added rp>=ritem &&   I hope to god its right! */
-	      if (rp >= ritem && ISVAR (*rp))
+	      if (ISVAR (*rp))
 		{
-		  /* Downcasting from item_number_t to symbol_number_t. */
+		  /* Downcasting from item_number to symbol_number.  */
 		  edge[nedges++] = map_goto (states1[--length],
 					     item_number_as_symbol_number (*rp));
-		  if (nullable[*rp])
-		    done = 0;
+		  if (nullable[*rp - ntokens])
+		    done = false;
 		}
 	    }
 	}
 
-      if (nedges)
+      if (nedges == 0)
+	includes[i] = NULL;
+      else
 	{
 	  int j;
-	  includes[i] = XCALLOC (goto_number_t, nedges + 1);
+	  includes[i] = xnmalloc (nedges + 1, sizeof includes[i][0]);
 	  for (j = 0; j < nedges; j++)
 	    includes[i][j] = edge[j];
-	  includes[i][nedges] = -1;
+	  includes[i][nedges] = END_NODE;
 	}
     }
 
-  XFREE (edge);
-  XFREE (states1);
+  free (edge);
+  free (states1);
 
   relation_transpose (&includes, ngotos);
 }
@@ -294,140 +292,154 @@ build_relations (void)
 static void
 compute_FOLLOWS (void)
 {
-  int i;
+  goto_number i;
 
-  relation_digraph (includes, ngotos, &F);
+  relation_digraph (includes, ngotos, &goto_follows);
 
   for (i = 0; i < ngotos; i++)
-    XFREE (includes[i]);
+    free (includes[i]);
 
-  XFREE (includes);
+  free (includes);
 }
 
 
 static void
-compute_lookaheads (void)
+compute_lookahead_tokens (void)
 {
   size_t i;
-  goto_list_t *sp;
+  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]);
+      bitset_or (LA[i], LA[i], goto_follows[sp->value]);
 
   /* Free LOOKBACK. */
   for (i = 0; i < nLA; i++)
-    LIST_FREE (goto_list_t, lookback[i]);
+    LIST_FREE (goto_list, lookback[i]);
 
-  XFREE (lookback);
-  bitsetv_free (F);
+  free (lookback);
 }
 
 
-/*---------------------------------------------------------------.
-| Count the number of lookaheads required for STATE (NLOOKAHEADS |
-| member).                                                       |
-`---------------------------------------------------------------*/
+/*----------------------------------------------------.
+| Count the number of lookahead tokens required for S |
+| (N_LOOKAHEAD_TOKENS member).                        |
+`----------------------------------------------------*/
 
 static int
-state_lookaheads_count (state_t *state)
+state_lookahead_tokens_count (state *s, bool default_reduction_only_for_accept)
 {
-  int k;
-  int nlookaheads = 0;
-  reductions_t *rp = state->reductions;
-  transitions_t *sp = state->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'.  */
+  int n_lookahead_tokens = 0;
+  reductions *rp = s->reductions;
+  transitions *sp = s->transitions;
+
+  /* Transitions are only disabled during conflict resolution, and that
+     hasn't happened yet, so there should be no need to check that
+     transition 0 hasn't been disabled before checking if it is a shift.
+     However, this check was performed at one time, so we leave it as an
+     aver.  */
+  aver (sp->num == 0 || !TRANSITION_IS_DISABLED (sp, 0));
+
+  /* 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'.  However, do not treat a state with any reductions as
+     consistent unless it is the accepting state (because there is never
+     a lookahead token that makes sense there, and so no lookahead token
+     should be read) if the user has otherwise disabled default
+     reductions.  */
   if (rp->num > 1
-      || (rp->num == 1 && sp->num &&
-	  !TRANSITION_IS_DISABLED (sp, 0) && TRANSITION_IS_SHIFT (sp, 0)))
-    nlookaheads += rp->num;
+      || (rp->num == 1 && sp->num && TRANSITION_IS_SHIFT (sp, 0))
+      || (rp->num == 1 && rp->rules[0]->number != 0
+          && default_reduction_only_for_accept))
+    n_lookahead_tokens += rp->num;
   else
-    state->consistent = 1;
-
-  for (k = 0; k < sp->num; k++)
-    if (!TRANSITION_IS_DISABLED (sp, k) && TRANSITION_IS_ERROR (sp, k))
-      {
-	state->consistent = 0;
-	break;
-      }
+    s->consistent = 1;
 
-  return nlookaheads;
+  return n_lookahead_tokens;
 }
 
 
-/*----------------------------------------------.
-| Compute LA, NLA, and the lookaheads members.  |
-`----------------------------------------------*/
+/*----------------------------------------------------.
+| Compute LA, NLA, and the lookahead_tokens members.  |
+`----------------------------------------------------*/
 
-static void
+void
 initialize_LA (void)
 {
-  state_number_t i;
+  state_number i;
   bitsetv pLA;
+  bool default_reduction_only_for_accept;
+  {
+    char *default_reductions =
+      muscle_percent_define_get ("lr.default-reductions");
+    default_reduction_only_for_accept =
+      0 == strcmp (default_reductions, "accepting");
+    free (default_reductions);
+  }
 
   /* Compute the total number of reductions requiring a lookahead.  */
   nLA = 0;
   for (i = 0; i < nstates; i++)
-    nLA += state_lookaheads_count (states[i]);
+    nLA +=
+      state_lookahead_tokens_count (states[i],
+                                    default_reduction_only_for_accept);
   /* Avoid having to special case 0.  */
   if (!nLA)
     nLA = 1;
 
   pLA = LA = bitsetv_create (nLA, ntokens, BITSET_FIXED);
-  lookback = XCALLOC (goto_list_t *, nLA);
 
-  /* Initialize the members LOOKAHEADS for each state which reductions
-     require lookaheads.  */
+  /* Initialize the members LOOKAHEAD_TOKENS for each state whose reductions
+     require lookahead tokens.  */
   for (i = 0; i < nstates; i++)
     {
-      int count = state_lookaheads_count (states[i]);
+      int count =
+        state_lookahead_tokens_count (states[i],
+                                      default_reduction_only_for_accept);
       if (count)
 	{
-	  states[i]->reductions->lookaheads = pLA;
+	  states[i]->reductions->lookahead_tokens = pLA;
 	  pLA += count;
 	}
     }
 }
 
 
-/*---------------------------------------.
-| Output the lookaheads for each state.  |
-`---------------------------------------*/
+/*---------------------------------------------.
+| Output the lookahead tokens for each state.  |
+`---------------------------------------------*/
 
 static void
-lookaheads_print (FILE *out)
+lookahead_tokens_print (FILE *out)
 {
-  state_number_t i;
+  state_number i;
   int j, k;
-  fprintf (out, _("Lookaheads: BEGIN\n"));
+  fprintf (out, "Lookahead tokens: BEGIN\n");
   for (i = 0; i < nstates; ++i)
     {
-      reductions_t *reds = states[i]->reductions;
+      reductions *reds = states[i]->reductions;
       bitset_iterator iter;
-      int nlookaheads = 0;
+      int n_lookahead_tokens = 0;
 
-      if (reds->lookaheads)
+      if (reds->lookahead_tokens)
 	for (k = 0; k < reds->num; ++k)
-	  if (reds->lookaheads[k])
-	    ++nlookaheads;
+	  if (reds->lookahead_tokens[k])
+	    ++n_lookahead_tokens;
 
-      fprintf (out, _("State %d: %d lookaheads\n"),
-	       i, nlookaheads);
+      fprintf (out, "State %d: %d lookahead tokens\n",
+	       i, n_lookahead_tokens);
 
-      if (reds->lookaheads)
+      if (reds->lookahead_tokens)
 	for (j = 0; j < reds->num; ++j)
-	  BITSET_FOR_EACH (iter, reds->lookaheads[j], k, 0)
+	  BITSET_FOR_EACH (iter, reds->lookahead_tokens[j], k, 0)
 	  {
-	    fprintf (out, _("   on %d (%s) -> rule %d\n"),
+	    fprintf (out, "   on %d (%s) -> rule %d\n",
 		     k, symbols[k]->tag,
 		     reds->rules[j]->number);
 	  };
     }
-  fprintf (out, _("Lookaheads: END\n"));
+  fprintf (out, "Lookahead tokens: END\n");
 }
 
 void
@@ -436,20 +448,55 @@ lalr (void)
   initialize_LA ();
   set_goto_map ();
   initialize_F ();
+  lookback = xcalloc (nLA, sizeof *lookback);
   build_relations ();
   compute_FOLLOWS ();
-  compute_lookaheads ();
+  compute_lookahead_tokens ();
 
   if (trace_flag & trace_sets)
-    lookaheads_print (stderr);
+    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_t s;
+  state_number s;
   for (s = 0; s < nstates; ++s)
-    states[s]->reductions->lookaheads = NULL;
+    states[s]->reductions->lookahead_tokens = NULL;
   bitsetv_free (LA);
 }