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style: rename LR0.* as lr0.*
Let's stick to lower case for file names. * src/LR0.h, src/LR0.c: Rename as... * src/lr0.h, src/lr0.c: these.
This commit is contained in:
Akim Demaille
363
src/lr0.c
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363
src/lr0.c
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/* Generate the LR(0) parser states for Bison.
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Copyright (C) 1984, 1986, 1989, 2000-2002, 2004-2015, 2018-2019 Free
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Software Foundation, Inc.
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This file is part of Bison, the GNU Compiler Compiler.
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This program 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 3 of the License, or
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(at your option) any later version.
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This program 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 this program. If not, see <http://www.gnu.org/licenses/>. */
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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 <config.h>
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#include "system.h"
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#include <bitset.h>
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#include "closure.h"
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#include "complain.h"
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#include "getargs.h"
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#include "gram.h"
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#include "lalr.h"
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#include "lr0.h"
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#include "reader.h"
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#include "reduce.h"
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#include "state.h"
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#include "symtab.h"
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typedef struct state_list
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{
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struct state_list *next;
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state *state;
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} state_list;
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static state_list *first_state = NULL;
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static state_list *last_state = NULL;
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/*------------------------------------------------------------------.
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| A state was just discovered from another state. Queue it for |
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| later examination, in order to find its transitions. Return it. |
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`------------------------------------------------------------------*/
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static state *
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state_list_append (symbol_number sym, size_t core_size, item_number *core)
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{
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state_list *node = xmalloc (sizeof *node);
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state *s = state_new (sym, core_size, core);
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if (trace_flag & trace_automaton)
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fprintf (stderr, "state_list_append (state = %d, symbol = %d (%s))\n",
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nstates, sym, symbols[sym]->tag);
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node->next = NULL;
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node->state = s;
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if (!first_state)
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first_state = node;
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if (last_state)
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last_state->next = node;
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last_state = node;
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return s;
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}
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static int nshifts;
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static symbol_number *shift_symbol;
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static rule **redset;
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static state **shiftset;
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static item_number **kernel_base;
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static int *kernel_size;
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static item_number *kernel_items;
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static void
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allocate_itemsets (void)
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{
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/* Count the number of occurrences of all the symbols in RITEMS.
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Note that useless productions (hence useless nonterminals) are
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browsed too, hence we need to allocate room for _all_ the
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symbols. */
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size_t count = 0;
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size_t *symbol_count = xcalloc (nsyms + nuseless_nonterminals,
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sizeof *symbol_count);
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for (rule_number r = 0; r < nrules; ++r)
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for (item_number *rhsp = rules[r].rhs; *rhsp >= 0; ++rhsp)
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{
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count++;
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symbol_count[*rhsp]++;
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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 S cannot be more than the number of times that S
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appears as an item, which is SYMBOL_COUNT[S].
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We allocate that much space for each symbol. */
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kernel_base = xnmalloc (nsyms, sizeof *kernel_base);
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kernel_items = xnmalloc (count, sizeof *kernel_items);
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count = 0;
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for (symbol_number 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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free (symbol_count);
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kernel_size = xnmalloc (nsyms, sizeof *kernel_size);
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}
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static void
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allocate_storage (void)
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{
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allocate_itemsets ();
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shiftset = xnmalloc (nsyms, sizeof *shiftset);
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redset = xnmalloc (nrules, sizeof *redset);
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state_hash_new ();
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shift_symbol = xnmalloc (nsyms, sizeof *shift_symbol);
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}
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static 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_size);
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free (kernel_items);
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state_hash_free ();
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}
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/*---------------------------------------------------------------.
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| Find which symbols can be shifted in S, and for each one |
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| record which items would be active after that shift. Uses the |
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| contents of itemset. |
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| |
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| shift_symbol is set to a vector of the symbols that can be |
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| shifted. For each symbol in the grammar, kernel_base[symbol] |
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| points to a vector of item numbers activated if that symbol is |
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| shifted, and kernel_size[symbol] is their numbers. |
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| |
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| itemset is sorted on item index in ritem, which is sorted on |
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| rule number. Compute each kernel_base[symbol] with the same |
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| sort. |
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`---------------------------------------------------------------*/
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static void
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new_itemsets (state *s)
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{
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if (trace_flag & trace_automaton)
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fprintf (stderr, "Entering new_itemsets, state = %d\n", s->number);
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memset (kernel_size, 0, nsyms * sizeof *kernel_size);
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nshifts = 0;
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for (size_t i = 0; i < nitemset; ++i)
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if (item_number_is_symbol_number (ritem[itemset[i]]))
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{
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symbol_number sym = item_number_as_symbol_number (ritem[itemset[i]]);
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if (!kernel_size[sym])
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{
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shift_symbol[nshifts] = sym;
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nshifts++;
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}
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kernel_base[sym][kernel_size[sym]] = itemset[i] + 1;
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kernel_size[sym]++;
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}
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}
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/*--------------------------------------------------------------.
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| Find the state we would get to (from the current state) by |
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| shifting SYM. Create a new state if no equivalent one exists |
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| already. Used by append_states. |
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`--------------------------------------------------------------*/
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static state *
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get_state (symbol_number sym, size_t core_size, item_number *core)
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{
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if (trace_flag & trace_automaton)
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fprintf (stderr, "Entering get_state, symbol = %d (%s)\n",
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sym, symbols[sym]->tag);
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state *s = state_hash_lookup (core_size, core);
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if (!s)
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s = state_list_append (sym, core_size, core);
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if (trace_flag & trace_automaton)
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fprintf (stderr, "Exiting get_state => %d\n", s->number);
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return s;
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}
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/*---------------------------------------------------------------.
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| Use the information computed by new_itemsets to find the state |
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| numbers reached by each shift transition from S. |
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| |
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| SHIFTSET is set up as a vector of those states. |
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`---------------------------------------------------------------*/
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static void
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append_states (state *s)
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{
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if (trace_flag & trace_automaton)
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fprintf (stderr, "Entering append_states, state = %d\n", s->number);
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/* First sort shift_symbol into increasing order. */
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for (int i = 1; i < nshifts; i++)
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{
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const symbol_number sym = shift_symbol[i];
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int j = i;
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for (; 0 < j && sym < shift_symbol[j - 1]; j--)
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shift_symbol[j] = shift_symbol[j - 1];
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shift_symbol[j] = sym;
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}
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for (int i = 0; i < nshifts; i++)
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{
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const symbol_number sym = shift_symbol[i];
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shiftset[i] = get_state (sym, kernel_size[sym], kernel_base[sym]);
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}
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}
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/*----------------------------------------------------------------.
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| Find which rules can be used for reduction transitions from the |
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| current state and make a reductions structure for the state to |
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| record their rule numbers. |
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`----------------------------------------------------------------*/
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static void
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save_reductions (state *s)
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{
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int count = 0;
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/* Find and count the active items that represent ends of rules. */
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for (size_t i = 0; i < nitemset; ++i)
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{
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item_number item = ritem[itemset[i]];
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if (item_number_is_rule_number (item))
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{
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rule_number r = item_number_as_rule_number (item);
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redset[count++] = &rules[r];
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if (r == 0)
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{
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/* This is "reduce 0", i.e., accept. */
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aver (!final_state);
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final_state = s;
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}
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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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state_reductions_set (s, count, redset);
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}
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/*---------------.
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| Build STATES. |
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`---------------*/
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static void
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set_states (void)
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{
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states = xcalloc (nstates, sizeof *states);
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while (first_state)
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{
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state_list *this = first_state;
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/* Pessimization, but simplification of the code: make sure all
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the states have valid transitions and reductions members,
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even if reduced to 0. It is too soon for errs, which are
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computed later, but set_conflicts. */
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state *s = this->state;
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if (!s->transitions)
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state_transitions_set (s, 0, 0);
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if (!s->reductions)
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state_reductions_set (s, 0, 0);
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states[s->number] = s;
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first_state = this->next;
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free (this);
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}
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first_state = NULL;
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last_state = NULL;
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}
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/*-------------------------------------------------------------------.
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| Compute the LR(0) parser states (see state.h for details) from the |
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| grammar. |
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`-------------------------------------------------------------------*/
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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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new_closure (nritems);
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/* Create the initial state. The 0 at the lhs is the index of the
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item of this initial rule. */
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item_number initial_core = 0;
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state_list_append (0, 1, &initial_core);
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/* States are queued when they are created; process them all. */
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for (state_list *list = first_state; list; list = list->next)
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{
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state *s = list->state;
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if (trace_flag & trace_automaton)
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fprintf (stderr, "Processing state %d (reached by %s)\n",
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s->number,
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symbols[s->accessing_symbol]->tag);
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/* Set up itemset for the transitions out of this state. itemset gets a
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vector of all the items that could be accepted next. */
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closure (s->items, s->nitems);
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/* Record the reductions allowed out of this state. */
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save_reductions (s);
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/* Find the itemsets of the states that shifts can reach. */
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new_itemsets (s);
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/* Find or create the core structures for those states. */
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append_states (s);
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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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state_transitions_set (s, nshifts, shiftset);
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}
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/* discard various storage */
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free_closure ();
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free_storage ();
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/* Set up STATES. */
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set_states ();
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}
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