708 lines
16 KiB
C
708 lines
16 KiB
C
/* Generate the nondeterministic finite state machine for bison,
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Copyright (C) 1984, 1986, 1989 Free Software Foundation, Inc.
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This file is part of Bison, the GNU Compiler Compiler.
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Bison is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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Bison is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with Bison; see the file COPYING. If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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/* See comments in state.h for the data structures that represent it.
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The entry point is generate_states. */
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#include <stdio.h>
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#include "system.h"
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#include "machine.h"
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#include "alloc.h"
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#include "gram.h"
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#include "state.h"
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extern char *nullable;
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extern short *itemset;
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extern short *itemsetend;
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int nstates;
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int final_state;
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core *first_state;
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shifts *first_shift;
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reductions *first_reduction;
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int get_state PARAMS((int));
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core *new_state PARAMS((int));
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void allocate_itemsets PARAMS((void));
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void allocate_storage PARAMS((void));
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void free_storage PARAMS((void));
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void generate_states PARAMS((void));
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void new_itemsets PARAMS((void));
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void append_states PARAMS((void));
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void initialize_states PARAMS((void));
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void save_shifts PARAMS((void));
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void save_reductions PARAMS((void));
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void augment_automaton PARAMS((void));
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void insert_start_shift PARAMS((void));
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extern void initialize_closure PARAMS((int));
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extern void closure PARAMS((short *, int));
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extern void finalize_closure PARAMS((void));
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extern void toomany PARAMS((char *));
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static core *this_state;
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static core *last_state;
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static shifts *last_shift;
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static reductions *last_reduction;
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static int nshifts;
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static short *shift_symbol;
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static short *redset;
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static short *shiftset;
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static short **kernel_base;
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static short **kernel_end;
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static short *kernel_items;
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/* hash table for states, to recognize equivalent ones. */
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#define STATE_TABLE_SIZE 1009
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static core **state_table;
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void
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allocate_itemsets (void)
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{
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register short *itemp;
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register int symbol;
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register int i;
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register int count;
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register short *symbol_count;
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count = 0;
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symbol_count = NEW2(nsyms, short);
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itemp = ritem;
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symbol = *itemp++;
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while (symbol)
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{
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if (symbol > 0)
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{
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count++;
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symbol_count[symbol]++;
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}
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symbol = *itemp++;
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}
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/* see comments before new_itemsets. All the vectors of items
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live inside kernel_items. The number of active items after
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some symbol cannot be more than the number of times that symbol
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appears as an item, which is symbol_count[symbol].
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We allocate that much space for each symbol. */
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kernel_base = NEW2(nsyms, short *);
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kernel_items = NEW2(count, short);
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count = 0;
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for (i = 0; i < nsyms; i++)
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{
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kernel_base[i] = kernel_items + count;
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count += symbol_count[i];
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}
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shift_symbol = symbol_count;
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kernel_end = NEW2(nsyms, short *);
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}
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void
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allocate_storage (void)
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{
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allocate_itemsets();
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shiftset = NEW2(nsyms, short);
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redset = NEW2(nrules + 1, short);
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state_table = NEW2(STATE_TABLE_SIZE, core *);
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}
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void
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free_storage (void)
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{
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FREE(shift_symbol);
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FREE(redset);
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FREE(shiftset);
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FREE(kernel_base);
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FREE(kernel_end);
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FREE(kernel_items);
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FREE(state_table);
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}
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/* compute the nondeterministic finite state machine (see state.h for details)
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from the grammar. */
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void
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generate_states (void)
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{
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allocate_storage();
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initialize_closure(nitems);
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initialize_states();
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while (this_state)
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{
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/* Set up ruleset and itemset for the transitions out of this state.
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ruleset gets a 1 bit for each rule that could reduce now.
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itemset gets a vector of all the items that could be accepted next. */
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closure(this_state->items, this_state->nitems);
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/* record the reductions allowed out of this state */
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save_reductions();
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/* find the itemsets of the states that shifts can reach */
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new_itemsets();
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/* find or create the core structures for those states */
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append_states();
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/* create the shifts structures for the shifts to those states,
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now that the state numbers transitioning to are known */
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if (nshifts > 0)
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save_shifts();
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/* states are queued when they are created; process them all */
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this_state = this_state->next;
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}
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/* discard various storage */
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finalize_closure();
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free_storage();
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/* set up initial and final states as parser wants them */
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augment_automaton();
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}
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/* Find which symbols can be shifted in the current state,
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and for each one record which items would be active after that shift.
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Uses the contents of itemset.
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shift_symbol is set to a vector of the symbols that can be shifted.
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For each symbol in the grammar, kernel_base[symbol] points to
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a vector of item numbers activated if that symbol is shifted,
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and kernel_end[symbol] points after the end of that vector. */
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void
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new_itemsets (void)
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{
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register int i;
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register int shiftcount;
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register short *isp;
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register short *ksp;
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register int symbol;
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#ifdef TRACE
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fprintf(stderr, "Entering new_itemsets\n");
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#endif
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for (i = 0; i < nsyms; i++)
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kernel_end[i] = NULL;
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shiftcount = 0;
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isp = itemset;
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while (isp < itemsetend)
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{
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i = *isp++;
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symbol = ritem[i];
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if (symbol > 0)
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{
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ksp = kernel_end[symbol];
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if (!ksp)
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{
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shift_symbol[shiftcount++] = symbol;
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ksp = kernel_base[symbol];
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}
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*ksp++ = i + 1;
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kernel_end[symbol] = ksp;
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}
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}
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nshifts = shiftcount;
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}
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/* Use the information computed by new_itemsets to find the state numbers
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reached by each shift transition from the current state.
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shiftset is set up as a vector of state numbers of those states. */
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void
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append_states (void)
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{
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register int i;
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register int j;
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register int symbol;
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#ifdef TRACE
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fprintf(stderr, "Entering append_states\n");
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#endif
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/* first sort shift_symbol into increasing order */
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for (i = 1; i < nshifts; i++)
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{
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symbol = shift_symbol[i];
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j = i;
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while (j > 0 && shift_symbol[j - 1] > symbol)
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{
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shift_symbol[j] = shift_symbol[j - 1];
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j--;
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}
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shift_symbol[j] = symbol;
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}
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for (i = 0; i < nshifts; i++)
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{
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symbol = shift_symbol[i];
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shiftset[i] = get_state(symbol);
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}
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}
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/* find the state number for the state we would get to
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(from the current state) by shifting symbol.
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Create a new state if no equivalent one exists already.
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Used by append_states */
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int
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get_state (int symbol)
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{
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register int key;
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register short *isp1;
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register short *isp2;
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register short *iend;
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register core *sp;
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register int found;
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int n;
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#ifdef TRACE
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fprintf(stderr, "Entering get_state, symbol = %d\n", symbol);
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#endif
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isp1 = kernel_base[symbol];
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iend = kernel_end[symbol];
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n = iend - isp1;
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/* add up the target state's active item numbers to get a hash key */
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key = 0;
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while (isp1 < iend)
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key += *isp1++;
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key = key % STATE_TABLE_SIZE;
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sp = state_table[key];
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if (sp)
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{
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found = 0;
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while (!found)
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{
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if (sp->nitems == n)
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{
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found = 1;
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isp1 = kernel_base[symbol];
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isp2 = sp->items;
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while (found && isp1 < iend)
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{
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if (*isp1++ != *isp2++)
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found = 0;
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}
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}
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if (!found)
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{
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if (sp->link)
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{
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sp = sp->link;
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}
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else /* bucket exhausted and no match */
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{
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sp = sp->link = new_state(symbol);
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found = 1;
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}
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}
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}
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}
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else /* bucket is empty */
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{
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state_table[key] = sp = new_state(symbol);
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}
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return (sp->number);
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}
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/* subroutine of get_state. create a new state for those items, if necessary. */
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core *
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new_state (int symbol)
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{
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register int n;
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register core *p;
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register short *isp1;
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register short *isp2;
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register short *iend;
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#ifdef TRACE
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fprintf(stderr, "Entering new_state, symbol = %d\n", symbol);
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#endif
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if (nstates >= MAXSHORT)
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toomany("states");
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isp1 = kernel_base[symbol];
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iend = kernel_end[symbol];
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n = iend - isp1;
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p = (core *) xmalloc((unsigned) (sizeof(core) + (n - 1) * sizeof(short)));
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p->accessing_symbol = symbol;
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p->number = nstates;
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p->nitems = n;
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isp2 = p->items;
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while (isp1 < iend)
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*isp2++ = *isp1++;
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last_state->next = p;
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last_state = p;
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nstates++;
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return (p);
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}
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void
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initialize_states (void)
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{
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register core *p;
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/* register unsigned *rp1; JF unused */
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/* register unsigned *rp2; JF unused */
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/* register unsigned *rend; JF unused */
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p = (core *) xmalloc((unsigned) (sizeof(core) - sizeof(short)));
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first_state = last_state = this_state = p;
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nstates = 1;
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}
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void
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save_shifts (void)
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{
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register shifts *p;
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register short *sp1;
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register short *sp2;
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register short *send;
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p = (shifts *) xmalloc((unsigned) (sizeof(shifts) +
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(nshifts - 1) * sizeof(short)));
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p->number = this_state->number;
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p->nshifts = nshifts;
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sp1 = shiftset;
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sp2 = p->shifts;
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send = shiftset + nshifts;
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while (sp1 < send)
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*sp2++ = *sp1++;
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if (last_shift)
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{
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last_shift->next = p;
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last_shift = p;
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}
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else
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{
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first_shift = p;
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last_shift = p;
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}
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}
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/* find which rules can be used for reduction transitions from the current state
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and make a reductions structure for the state to record their rule numbers. */
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void
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save_reductions (void)
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{
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register short *isp;
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register short *rp1;
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register short *rp2;
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register int item;
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register int count;
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register reductions *p;
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short *rend;
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/* find and count the active items that represent ends of rules */
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count = 0;
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for (isp = itemset; isp < itemsetend; isp++)
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{
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item = ritem[*isp];
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if (item < 0)
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{
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redset[count++] = -item;
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}
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}
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/* make a reductions structure and copy the data into it. */
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if (count)
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{
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p = (reductions *) xmalloc((unsigned) (sizeof(reductions) +
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(count - 1) * sizeof(short)));
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p->number = this_state->number;
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p->nreds = count;
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rp1 = redset;
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rp2 = p->rules;
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rend = rp1 + count;
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while (rp1 < rend)
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*rp2++ = *rp1++;
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if (last_reduction)
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{
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last_reduction->next = p;
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last_reduction = p;
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}
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else
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{
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first_reduction = p;
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last_reduction = p;
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}
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}
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}
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/* Make sure that the initial state has a shift that accepts the
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grammar's start symbol and goes to the next-to-final state,
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which has a shift going to the final state, which has a shift
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to the termination state.
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Create such states and shifts if they don't happen to exist already. */
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void
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augment_automaton (void)
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{
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register int i;
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register int k;
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/* register int found; JF unused */
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register core *statep;
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register shifts *sp;
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register shifts *sp2;
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register shifts *sp1 = NULL;
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sp = first_shift;
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if (sp)
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{
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if (sp->number == 0)
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{
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k = sp->nshifts;
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statep = first_state->next;
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/* The states reached by shifts from first_state are numbered 1...K.
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Look for one reached by start_symbol. */
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while (statep->accessing_symbol < start_symbol
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&& statep->number < k)
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statep = statep->next;
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if (statep->accessing_symbol == start_symbol)
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{
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/* We already have a next-to-final state.
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Make sure it has a shift to what will be the final state. */
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k = statep->number;
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while (sp && sp->number < k)
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{
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sp1 = sp;
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sp = sp->next;
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}
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if (sp && sp->number == k)
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{
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sp2 = (shifts *) xmalloc((unsigned) (sizeof(shifts)
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+ sp->nshifts * sizeof(short)));
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sp2->number = k;
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sp2->nshifts = sp->nshifts + 1;
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sp2->shifts[0] = nstates;
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for (i = sp->nshifts; i > 0; i--)
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sp2->shifts[i] = sp->shifts[i - 1];
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/* Patch sp2 into the chain of shifts in place of sp,
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following sp1. */
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sp2->next = sp->next;
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sp1->next = sp2;
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if (sp == last_shift)
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last_shift = sp2;
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FREE(sp);
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}
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else
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{
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sp2 = NEW(shifts);
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sp2->number = k;
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sp2->nshifts = 1;
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sp2->shifts[0] = nstates;
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/* Patch sp2 into the chain of shifts between sp1 and sp. */
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sp2->next = sp;
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sp1->next = sp2;
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if (sp == 0)
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last_shift = sp2;
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}
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}
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else
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{
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/* There is no next-to-final state as yet. */
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/* Add one more shift in first_shift,
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going to the next-to-final state (yet to be made). */
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sp = first_shift;
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sp2 = (shifts *) xmalloc(sizeof(shifts)
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+ sp->nshifts * sizeof(short));
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sp2->nshifts = sp->nshifts + 1;
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/* Stick this shift into the vector at the proper place. */
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statep = first_state->next;
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for (k = 0, i = 0; i < sp->nshifts; k++, i++)
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{
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if (statep->accessing_symbol > start_symbol && i == k)
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sp2->shifts[k++] = nstates;
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sp2->shifts[k] = sp->shifts[i];
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statep = statep->next;
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}
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if (i == k)
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sp2->shifts[k++] = nstates;
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/* Patch sp2 into the chain of shifts
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in place of sp, at the beginning. */
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sp2->next = sp->next;
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first_shift = sp2;
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if (last_shift == sp)
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last_shift = sp2;
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FREE(sp);
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/* Create the next-to-final state, with shift to
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what will be the final state. */
|
|
insert_start_shift();
|
|
}
|
|
}
|
|
else
|
|
{
|
|
/* The initial state didn't even have any shifts.
|
|
Give it one shift, to the next-to-final state. */
|
|
sp = NEW(shifts);
|
|
sp->nshifts = 1;
|
|
sp->shifts[0] = nstates;
|
|
|
|
/* Patch sp into the chain of shifts at the beginning. */
|
|
sp->next = first_shift;
|
|
first_shift = sp;
|
|
|
|
/* Create the next-to-final state, with shift to
|
|
what will be the final state. */
|
|
insert_start_shift();
|
|
}
|
|
}
|
|
else
|
|
{
|
|
/* There are no shifts for any state.
|
|
Make one shift, from the initial state to the next-to-final state. */
|
|
|
|
sp = NEW(shifts);
|
|
sp->nshifts = 1;
|
|
sp->shifts[0] = nstates;
|
|
|
|
/* Initialize the chain of shifts with sp. */
|
|
first_shift = sp;
|
|
last_shift = sp;
|
|
|
|
/* Create the next-to-final state, with shift to
|
|
what will be the final state. */
|
|
insert_start_shift();
|
|
}
|
|
|
|
/* Make the final state--the one that follows a shift from the
|
|
next-to-final state.
|
|
The symbol for that shift is 0 (end-of-file). */
|
|
statep = (core *) xmalloc((unsigned) (sizeof(core) - sizeof(short)));
|
|
statep->number = nstates;
|
|
last_state->next = statep;
|
|
last_state = statep;
|
|
|
|
/* Make the shift from the final state to the termination state. */
|
|
sp = NEW(shifts);
|
|
sp->number = nstates++;
|
|
sp->nshifts = 1;
|
|
sp->shifts[0] = nstates;
|
|
last_shift->next = sp;
|
|
last_shift = sp;
|
|
|
|
/* Note that the variable `final_state' refers to what we sometimes call
|
|
the termination state. */
|
|
final_state = nstates;
|
|
|
|
/* Make the termination state. */
|
|
statep = (core *) xmalloc((unsigned) (sizeof(core) - sizeof(short)));
|
|
statep->number = nstates++;
|
|
last_state->next = statep;
|
|
last_state = statep;
|
|
}
|
|
|
|
|
|
/* subroutine of augment_automaton.
|
|
Create the next-to-final state, to which a shift has already been made in
|
|
the initial state. */
|
|
void
|
|
insert_start_shift (void)
|
|
{
|
|
register core *statep;
|
|
register shifts *sp;
|
|
|
|
statep = (core *) xmalloc((unsigned) (sizeof(core) - sizeof(short)));
|
|
statep->number = nstates;
|
|
statep->accessing_symbol = start_symbol;
|
|
|
|
last_state->next = statep;
|
|
last_state = statep;
|
|
|
|
/* Make a shift from this state to (what will be) the final state. */
|
|
sp = NEW(shifts);
|
|
sp->number = nstates++;
|
|
sp->nshifts = 1;
|
|
sp->shifts[0] = nstates;
|
|
|
|
last_shift->next = sp;
|
|
last_shift = sp;
|
|
}
|