* doc/bison.texinfo (Stack Overflow): xref to Recursion.

[bison.git] / src / LR0.c

diff --git a/src/LR0.c b/src/LR0.c
index 6a911f240f47fe0bc569729854dd6c9e820aa4dc..7dd7b441f461bf86739038d3cc41365a225847b4 100644 (file)
--- a/src/LR0.c
+++ b/src/LR0.c
@@ -1,5 +1,7 @@
 /* Generate the nondeterministic finite state machine for bison,
 /* Generate the nondeterministic finite state machine for bison,

-   Copyright 1984, 1986, 1989, 2000, 2001  Free Software Foundation, Inc.
+
+   Copyright (C) 1984, 1986, 1989, 2000, 2001, 2002 Free Software
+   Foundation, Inc.

 
    This file is part of Bison, the GNU Compiler Compiler.
 
 
    This file is part of Bison, the GNU Compiler Compiler.
 


@@ -23,7 +25,10 @@
    The entry point is generate_states.  */
 
 #include "system.h"
    The entry point is generate_states.  */
 
 #include "system.h"

+#include "bitset.h"
+#include "quotearg.h"

 #include "symtab.h"
 #include "symtab.h"

+#include "gram.h"

 #include "getargs.h"
 #include "reader.h"
 #include "gram.h"
 #include "getargs.h"
 #include "reader.h"
 #include "gram.h"


@@ -34,40 +39,66 @@
 #include "lalr.h"
 #include "reduce.h"
 
 #include "lalr.h"
 #include "reduce.h"
 

-int nstates;
-/* Initialize the final state to -1, otherwise, it might be set to 0
-   by default, and since we don't compute the reductions of the final
-   state, we end up not computing the reductions of the initial state,
-   which is of course needed.
+typedef struct state_list_s
+{
+  struct state_list_s *next;
+  state_t *state;
+} state_list_t;

 
 

-   FINAL_STATE is properly set by new_state when it recognizes the
-   accessing symbol: EOF.  */
-int final_state = -1;
-static state_t *first_state = NULL;
+static state_list_t *first_state = NULL;
+static state_list_t *last_state = NULL;

 
 

-static state_t *this_state = NULL;
-static state_t *last_state = NULL;

 
 

-static int nshifts;
-static short *shift_symbol = NULL;
+/*------------------------------------------------------------------.
+| A state was just discovered from another state.  Queue it for     |
+| later examination, in order to find its transitions.  Return it.  |
+`------------------------------------------------------------------*/

 
 

-static short *redset = NULL;
-static short *shiftset = NULL;
+static state_t *
+state_list_append (symbol_number_t symbol,
+                  size_t core_size, item_number_t *core)
+{
+  state_list_t *node = XMALLOC (state_list_t, 1);
+  state_t *state = state_new (symbol, core_size, core);

 
 

-static short **kernel_base = NULL;
-static int *kernel_size = NULL;
-static short *kernel_items = NULL;
+  if (trace_flag & trace_automaton)
+    fprintf (stderr, "state_list_append (state = %d, symbol = %d (%s))\n",
+            nstates, symbol, symbols[symbol]->tag);

 
 

-/* hash table for states, to recognize equivalent ones.  */
+  /* If this is the endtoken, and this is not the initial state, then
+     this is the final state.  */
+  if (symbol == 0 && first_state)
+    final_state = state;

 
 

-#define        STATE_HASH_SIZE 1009
-static state_t **state_hash = NULL;
+  node->next = NULL;
+  node->state = state;
+
+  if (!first_state)
+    first_state = node;
+  if (last_state)
+    last_state->next = node;
+  last_state = node;
+
+  return state;
+}
+
+static int nshifts;
+static symbol_number_t *shift_symbol = NULL;
+
+static rule_t **redset = NULL;
+static state_t **shiftset = NULL;
+
+static item_number_t **kernel_base = NULL;
+static int *kernel_size = NULL;
+static item_number_t *kernel_items = NULL;

 
 \f
 static void
 allocate_itemsets (void)
 {
 
 \f
 static void
 allocate_itemsets (void)
 {

-  int i;
+  symbol_number_t i;
+  rule_number_t r;
+  item_number_t *rhsp;

 
   /* Count the number of occurrences of all the symbols in RITEMS.
      Note that useless productions (hence useless nonterminals) are
 
   /* Count the number of occurrences of all the symbols in RITEMS.
      Note that useless productions (hence useless nonterminals) are


@@ -76,22 +107,22 @@ allocate_itemsets (void)
   int count = 0;
   short *symbol_count = XCALLOC (short, nsyms + nuseless_nonterminals);
 
   int count = 0;
   short *symbol_count = XCALLOC (short, nsyms + nuseless_nonterminals);
 

-  for (i = 0; i < nritems; ++i)
-    if (ritem[i] >= 0)
+  for (r = 0; r < nrules; ++r)
+    for (rhsp = rules[r].rhs; *rhsp >= 0; ++rhsp)

       {
        count++;
       {
        count++;

-       symbol_count[ritem[i]]++;
+       symbol_count[*rhsp]++;

       }
 
   /* See comments before new_itemsets.  All the vectors of items
      live inside KERNEL_ITEMS.  The number of active items after
      some symbol cannot be more than the number of times that symbol
       }
 
   /* See comments before new_itemsets.  All the vectors of items
      live inside KERNEL_ITEMS.  The number of active items after
      some symbol cannot be more than the number of times that symbol

-     appears as an item, which is symbol_count[symbol].
+     appears as an item, which is SYMBOL_COUNT[SYMBOL].

      We allocate that much space for each symbol.  */
 
      We allocate that much space for each symbol.  */
 

-  kernel_base = XCALLOC (short *, nsyms);
+  kernel_base = XCALLOC (item_number_t *, nsyms);

   if (count)
   if (count)

-    kernel_items = XCALLOC (short, count);
+    kernel_items = XCALLOC (item_number_t, count);

 
   count = 0;
   for (i = 0; i < nsyms; i++)
 
   count = 0;
   for (i = 0; i < nsyms; i++)


@@ -110,10 +141,10 @@ allocate_storage (void)
 {
   allocate_itemsets ();
 
 {
   allocate_itemsets ();
 

-  shiftset = XCALLOC (short, nsyms);
-  redset = XCALLOC (short, nrules + 1);
-  state_hash = XCALLOC (state_t *, STATE_HASH_SIZE);
-  shift_symbol = XCALLOC (short, nsyms);
+  shiftset = XCALLOC (state_t *, nsyms);
+  redset = XCALLOC (rule_t *, nrules);
+  state_hash_new ();
+  shift_symbol = XCALLOC (symbol_number_t, nsyms);

 }
 
 
 }
 
 


@@ -126,172 +157,97 @@ free_storage (void)
   free (kernel_base);
   free (kernel_size);
   XFREE (kernel_items);
   free (kernel_base);
   free (kernel_size);
   XFREE (kernel_items);

-  free (state_hash);
+  state_hash_free ();

 }
 
 
 
 
 }
 
 
 
 

-/*----------------------------------------------------------------.
-| Find which symbols can be shifted in the current state, and for |
-| each one record which items would be active after that shift.   |
-| Uses the contents of itemset.                                   |
-|                                                                 |
-| shift_symbol is set to a vector of the symbols that can be      |
-| shifted.  For each symbol in the grammar, kernel_base[symbol]   |
-| points to a vector of item numbers activated if that symbol is  |
-| shifted, and kernel_size[symbol] is their numbers.              |
-`----------------------------------------------------------------*/
+/*---------------------------------------------------------------.
+| Find which symbols can be shifted in STATE, and for each one   |
+| record which items would be active after that shift.  Uses the |
+| contents of itemset.                                           |
+|                                                                |
+| shift_symbol is set to a vector of the symbols that can be     |
+| shifted.  For each symbol in the grammar, kernel_base[symbol]  |
+| points to a vector of item numbers activated if that symbol is |
+| shifted, and kernel_size[symbol] is their numbers.             |
+`---------------------------------------------------------------*/

 
 static void
 
 static void

-new_itemsets (void)
+new_itemsets (state_t *state)

 {
   int i;
 
 {
   int i;
 

-  if (trace_flag)
+  if (trace_flag & trace_automaton)

     fprintf (stderr, "Entering new_itemsets, state = %d\n",
     fprintf (stderr, "Entering new_itemsets, state = %d\n",

-            this_state->number);
+            state->number);

 
   for (i = 0; i < nsyms; i++)
     kernel_size[i] = 0;
 
   nshifts = 0;
 
 
   for (i = 0; i < nsyms; i++)
     kernel_size[i] = 0;
 
   nshifts = 0;
 

-  for (i = 0; i < nitemset; ++i)
-    {
-      int symbol = ritem[itemset[i]];
-      if (symbol >= 0)
-       {
-         if (!kernel_size[symbol])
-           {
-             shift_symbol[nshifts] = symbol;
-             nshifts++;
-           }
-
-         kernel_base[symbol][kernel_size[symbol]] = itemset[i] + 1;
-         kernel_size[symbol]++;
-       }
-    }
+  for (i = 0; i < nritemset; ++i)
+    if (ritem[itemset[i]] >= 0)
+      {
+       symbol_number_t symbol
+         = item_number_as_symbol_number (ritem[itemset[i]]);
+       if (!kernel_size[symbol])
+         {
+           shift_symbol[nshifts] = symbol;
+           nshifts++;
+         }
+
+       kernel_base[symbol][kernel_size[symbol]] = itemset[i] + 1;
+       kernel_size[symbol]++;
+      }

 }
 
 
 
 /*-----------------------------------------------------------------.
 }
 
 
 
 /*-----------------------------------------------------------------.

-| Subroutine of get_state.  Create a new state for those items, if |
-| necessary.                                                       |
+| Find the state we would get to (from the current state) by       |
+| shifting SYMBOL.  Create a new state if no equivalent one exists |
+| already.  Used by append_states.                                 |

 `-----------------------------------------------------------------*/
 
 static state_t *
 `-----------------------------------------------------------------*/
 
 static state_t *

-new_state (int symbol)
-{
-  state_t *p;
-
-  if (trace_flag)
-    fprintf (stderr, "Entering new_state, state = %d, symbol = %d (%s)\n",
-            this_state->number, symbol, symbols[symbol]->tag);
-
-  if (nstates >= MAXSHORT)
-    fatal (_("too many states (max %d)"), MAXSHORT);
-
-  p = STATE_ALLOC (kernel_size[symbol]);
-  p->accessing_symbol = symbol;
-  p->number = nstates;
-  p->nitems = kernel_size[symbol];
-
-  shortcpy (p->items, kernel_base[symbol], kernel_size[symbol]);
-
-  last_state->next = p;
-  last_state = p;
-  nstates++;
-
-  /* If this is the eoftoken, then this is the final state. */
-  if (symbol == 0)
-    final_state = p->number;
-
-  return p;
-}
-
-
-/*--------------------------------------------------------------.
-| Find the state number for the state we would get to (from the |
-| current state) by shifting symbol.  Create a new state if no  |
-| equivalent one exists already.  Used by append_states.        |
-`--------------------------------------------------------------*/
-
-static int
-get_state (int symbol)
+get_state (symbol_number_t symbol, size_t core_size, item_number_t *core)

 {
 {

-  int key;
-  int i;

   state_t *sp;
 
   state_t *sp;
 

-  if (trace_flag)
-    fprintf (stderr, "Entering get_state, state = %d, symbol = %d (%s)\n",
-            this_state->number, symbol, symbols[symbol]->tag);
+  if (trace_flag & trace_automaton)
+    fprintf (stderr, "Entering get_state, symbol = %d (%s)\n",
+            symbol, symbols[symbol]->tag);

 
 

-  /* Add up the target state's active item numbers to get a hash key.
-     */
-  key = 0;
-  for (i = 0; i < kernel_size[symbol]; ++i)
-    key += kernel_base[symbol][i];
-  key = key % STATE_HASH_SIZE;
-  sp = state_hash[key];
+  sp = state_hash_lookup (core_size, core);
+  if (!sp)
+    sp = state_list_append (symbol, core_size, core);

 
 

-  if (sp)
-    {
-      int found = 0;
-      while (!found)
-       {
-         if (sp->nitems == kernel_size[symbol])
-           {
-             found = 1;
-             for (i = 0; i < kernel_size[symbol]; ++i)
-               if (kernel_base[symbol][i] != sp->items[i])
-                 found = 0;
-           }
-
-         if (!found)
-           {
-             if (sp->link)
-               {
-                 sp = sp->link;
-               }
-             else              /* bucket exhausted and no match */
-               {
-                 sp = sp->link = new_state (symbol);
-                 found = 1;
-               }
-           }
-       }
-    }
-  else                         /* bucket is empty */
-    {
-      state_hash[key] = sp = new_state (symbol);
-    }
-
-  if (trace_flag)
+  if (trace_flag & trace_automaton)

     fprintf (stderr, "Exiting get_state => %d\n", sp->number);
 
     fprintf (stderr, "Exiting get_state => %d\n", sp->number);
 

-  return sp->number;
+  return sp;

 }
 
 }
 

-/*------------------------------------------------------------------.
-| Use the information computed by new_itemsets to find the state    |
-| numbers reached by each shift transition from the current state.  |
-|                                                                   |
-| shiftset is set up as a vector of state numbers of those states.  |
-`------------------------------------------------------------------*/
+/*---------------------------------------------------------------.
+| Use the information computed by new_itemsets to find the state |
+| numbers reached by each shift transition from STATE.           |
+|                                                                |
+| SHIFTSET is set up as a vector of those states.                |
+`---------------------------------------------------------------*/

 
 static void
 
 static void

-append_states (void)
+append_states (state_t *state)

 {
   int i;
   int j;
 {
   int i;
   int j;

-  int symbol;
+  symbol_number_t symbol;

 
 

-  if (trace_flag)
+  if (trace_flag & trace_automaton)

     fprintf (stderr, "Entering append_states, state = %d\n",
     fprintf (stderr, "Entering append_states, state = %d\n",

-            this_state->number);
+            state->number);

 
   /* first sort shift_symbol into increasing order */
 
 
   /* first sort shift_symbol into increasing order */
 


@@ -308,28 +264,11 @@ append_states (void)
     }
 
   for (i = 0; i < nshifts; i++)
     }
 
   for (i = 0; i < nshifts; i++)

-    shiftset[i] = get_state (shift_symbol[i]);
-}
-
-
-static void
-new_states (void)
-{
-  first_state = last_state = this_state = STATE_ALLOC (0);
-  nstates = 1;
-}
-
-
-/*------------------------------------------------------------.
-| Save the NSHIFTS of SHIFTSET into the current linked list.  |
-`------------------------------------------------------------*/
-
-static void
-save_shifts (void)
-{
-  shifts *p = shifts_new (nshifts);
-  shortcpy (p->shifts, shiftset, nshifts);
-  this_state->shifts = p;
+    {
+      symbol = shift_symbol[i];
+      shiftset[i] = get_state (symbol,
+                              kernel_size[symbol], kernel_base[symbol]);
+    }

 }
 
 
 }
 
 


@@ -340,27 +279,21 @@ save_shifts (void)
 `----------------------------------------------------------------*/
 
 static void
 `----------------------------------------------------------------*/
 
 static void

-save_reductions (void)
+save_reductions (state_t *state)

 {
   int count = 0;
   int i;
 
 {
   int count = 0;
   int i;
 

-  /* If this is the final state, we want it to have no reductions at
-     all, although it has one for `START_SYMBOL EOF .'.  */
-  if (this_state->number == final_state)
-    return;
-

   /* Find and count the active items that represent ends of rules. */
   /* Find and count the active items that represent ends of rules. */

-  for (i = 0; i < nitemset; ++i)
+  for (i = 0; i < nritemset; ++i)

     {
       int item = ritem[itemset[i]];
       if (item < 0)
     {
       int item = ritem[itemset[i]];
       if (item < 0)

-       redset[count++] = -item;
+       redset[count++] = &rules[item_number_as_rule_number (item)];

     }
 
   /* Make a reductions structure and copy the data into it.  */
     }
 
   /* Make a reductions structure and copy the data into it.  */

-  this_state->reductions = reductions_new (count);
-  shortcpy (this_state->reductions->rules, redset, count);
+  state_reductions_set (state, count, redset);

 }
 
 \f
 }
 
 \f


@@ -371,25 +304,32 @@ save_reductions (void)
 static void
 set_states (void)
 {
 static void
 set_states (void)
 {

-  state_t *sp;

   states = XCALLOC (state_t *, nstates);
 
   states = XCALLOC (state_t *, nstates);
 

-  for (sp = first_state; sp; sp = sp->next)
+  while (first_state)

     {
     {

+      state_list_t *this = first_state;
+

       /* Pessimization, but simplification of the code: make sure all
       /* Pessimization, but simplification of the code: make sure all

-        the states have a shifts, errs, and reductions, even if
-        reduced to 0.  */
-      if (!sp->shifts)
-       sp->shifts = shifts_new (0);
-      if (!sp->errs)
-       sp->errs = errs_new (0);
-      if (!sp->reductions)
-       sp->reductions = reductions_new (0);
-
-      states[sp->number] = sp;
+        the states have valid transitions and reductions members,
+        even if reduced to 0.  It is too soon for errs, which are
+        computed later, but set_conflicts.  */
+      state_t *state = this->state;
+      if (!state->transitions)
+       state_transitions_set (state, 0, 0);
+      if (!state->reductions)
+       state_reductions_set (state, 0, 0);
+
+      states[state->number] = state;
+
+      first_state = this->next;
+      free (this);

     }
     }

+  first_state = NULL;
+  last_state = NULL;

 }
 
 }
 

+

 /*-------------------------------------------------------------------.
 | Compute the nondeterministic finite state machine (see state.h for |
 | details) from the grammar.                                         |
 /*-------------------------------------------------------------------.
 | Compute the nondeterministic finite state machine (see state.h for |
 | details) from the grammar.                                         |


@@ -398,34 +338,44 @@ set_states (void)
 void
 generate_states (void)
 {
 void
 generate_states (void)
 {

+  state_list_t *list = NULL;

   allocate_storage ();
   new_closure (nritems);
   allocate_storage ();
   new_closure (nritems);

-  new_states ();

 
 

-  while (this_state)
+  /* Create the initial state.  The 0 at the lhs is the index of the
+     item of this initial rule.  */
+  kernel_base[0][0] = 0;
+  kernel_size[0] = 1;
+  state_list_append (0, kernel_size[0], kernel_base[0]);
+
+  list = first_state;
+
+  while (list)

     {
     {

-      if (trace_flag)
+      state_t *state = list->state;
+      if (trace_flag & trace_automaton)

        fprintf (stderr, "Processing state %d (reached by %s)\n",
        fprintf (stderr, "Processing state %d (reached by %s)\n",

-                this_state->number,
-                symbols[this_state->accessing_symbol]->tag);
+                state->number,
+                symbols[state->accessing_symbol]->tag);

       /* Set up ruleset and itemset for the transitions out of this
          state.  ruleset gets a 1 bit for each rule that could reduce
          now.  itemset gets a vector of all the items that could be
          accepted next.  */
       /* Set up ruleset and itemset for the transitions out of this
          state.  ruleset gets a 1 bit for each rule that could reduce
          now.  itemset gets a vector of all the items that could be
          accepted next.  */

-      closure (this_state->items, this_state->nitems);
-      /* record the reductions allowed out of this state */
-      save_reductions ();
-      /* find the itemsets of the states that shifts can reach */
-      new_itemsets ();
-      /* find or create the core structures for those states */
-      append_states ();
-
-      /* create the shifts structures for the shifts to those states,
-         now that the state numbers transitioning to are known */
-      save_shifts ();
-
-      /* states are queued when they are created; process them all */
-      this_state = this_state->next;
+      closure (state->items, state->nitems);
+      /* Record the reductions allowed out of this state.  */
+      save_reductions (state);
+      /* Find the itemsets of the states that shifts can reach.  */
+      new_itemsets (state);
+      /* Find or create the core structures for those states.  */
+      append_states (state);
+
+      /* Create the shifts structures for the shifts to those states,
+        now that the state numbers transitioning to are known.  */
+      state_transitions_set (state, nshifts, shiftset);
+
+      /* States are queued when they are created; process them all.
+        */
+      list = list->next;

     }
 
   /* discard various storage */
     }
 
   /* discard various storage */