X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/6b98e4b5636203b60c2a43ddaa988562616b4c69..49f801e6fecc97549486b15513c68f17496463c5:/src/LR0.c diff --git a/src/LR0.c b/src/LR0.c index 95200d53..7dd7b441 100644 --- a/src/LR0.c +++ b/src/LR0.c @@ -1,5 +1,7 @@ /* Generate the nondeterministic finite state machine for bison, - Copyright 1984, 1986, 1989, 2000, 2001, 2002 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. @@ -37,40 +39,65 @@ #include "lalr.h" #include "reduce.h" -unsigned int nstates = 0; -/* 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; + +static state_list_t *first_state = NULL; +static state_list_t *last_state = NULL; + + +/*------------------------------------------------------------------. +| A state was just discovered from another state. Queue it for | +| later examination, in order to find its transitions. Return it. | +`------------------------------------------------------------------*/ + +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); + + if (trace_flag & trace_automaton) + fprintf (stderr, "state_list_append (state = %d, symbol = %d (%s))\n", + nstates, symbol, symbols[symbol]->tag); + + /* 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; - 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; + node->next = NULL; + node->state = state; -static state_t *this_state = NULL; -static state_t *last_state = NULL; + 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 short *redset = NULL; -static short *shiftset = 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; -/* hash table for states, to recognize equivalent ones. */ - -#define STATE_HASH_SIZE 1009 -static state_t **state_hash = NULL; - static void allocate_itemsets (void) { - int i, r; + symbol_number_t i; + rule_number_t r; item_number_t *rhsp; /* Count the number of occurrences of all the symbols in RITEMS. @@ -80,7 +107,7 @@ allocate_itemsets (void) int count = 0; short *symbol_count = XCALLOC (short, nsyms + nuseless_nonterminals); - for (r = 1; r < nrules + 1; ++r) + for (r = 0; r < nrules; ++r) for (rhsp = rules[r].rhs; *rhsp >= 0; ++rhsp) { count++; @@ -90,7 +117,7 @@ allocate_itemsets (void) /* 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. */ kernel_base = XCALLOC (item_number_t *, nsyms); @@ -114,9 +141,9 @@ allocate_storage (void) { allocate_itemsets (); - shiftset = XCALLOC (short, nsyms); - redset = XCALLOC (short, nrules + 1); - state_hash = XCALLOC (state_t *, STATE_HASH_SIZE); + shiftset = XCALLOC (state_t *, nsyms); + redset = XCALLOC (rule_t *, nrules); + state_hash_new (); shift_symbol = XCALLOC (symbol_number_t, nsyms); } @@ -130,31 +157,31 @@ free_storage (void) 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 -new_itemsets (void) +new_itemsets (state_t *state) { int i; - if (trace_flag) + if (trace_flag & trace_automaton) fprintf (stderr, "Entering new_itemsets, state = %d\n", - this_state->number); + state->number); for (i = 0; i < nsyms; i++) kernel_size[i] = 0; @@ -180,128 +207,47 @@ new_itemsets (void) /*-----------------------------------------------------------------. -| 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 * -new_state (symbol_number_t symbol, size_t core_size, item_number_t *core) -{ - state_t *p; - - if (trace_flag) - fprintf (stderr, "Entering new_state, state = %d, symbol = %d (%s)\n", - nstates, symbol, symbol_tag_get (symbols[symbol])); - - if (nstates >= SHRT_MAX) - fatal (_("too many states (max %d)"), SHRT_MAX); - - p = STATE_ALLOC (core_size); - p->accessing_symbol = symbol; - p->number = nstates; - p->solved_conflicts = NULL; - - p->nitems = core_size; - memcpy (p->items, core, core_size * sizeof (core[0])); - - /* If this is the eoftoken, and this is not the initial state, then - this is the final state. */ - if (symbol == 0 && first_state) - final_state = p->number; - - if (!first_state) - first_state = p; - if (last_state) - last_state->next = p; - last_state = p; - - nstates++; - - 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 (symbol_number_t symbol, size_t core_size, item_number_t *core) { - int key; - size_t i; state_t *sp; - if (trace_flag) - fprintf (stderr, "Entering get_state, state = %d, symbol = %d (%s)\n", - this_state->number, symbol, - symbol_tag_get (symbols[symbol])); + 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 < core_size; ++i) - key += core[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 == core_size) - { - found = 1; - for (i = 0; i < core_size; ++i) - if (core[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, core_size, core); - found = 1; - } - } - } - } - else /* bucket is empty */ - { - state_hash[key] = sp = new_state (symbol, core_size, core); - } - - if (trace_flag) + if (trace_flag & trace_automaton) 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 -append_states (void) +append_states (state_t *state) { int i; int j; symbol_number_t symbol; - if (trace_flag) + if (trace_flag & trace_automaton) fprintf (stderr, "Entering append_states, state = %d\n", - this_state->number); + state->number); /* first sort shift_symbol into increasing order */ @@ -326,29 +272,6 @@ append_states (void) } -static void -new_states (void) -{ - /* The 0 at the lhs is the index of the item of this initial rule. */ - kernel_base[0][0] = 0; - kernel_size[0] = 1; - this_state = new_state (0, kernel_size[0], kernel_base[0]); -} - - -/*------------------------------------------------------------. -| Save the NSHIFTS of SHIFTSET into the current linked list. | -`------------------------------------------------------------*/ - -static void -save_shifts (void) -{ - shifts *p = shifts_new (nshifts); - memcpy (p->shifts, shiftset, nshifts * sizeof (shiftset[0])); - this_state->shifts = p; -} - - /*----------------------------------------------------------------. | Find which rules can be used for reduction transitions from the | | current state and make a reductions structure for the state to | @@ -356,27 +279,21 @@ save_shifts (void) `----------------------------------------------------------------*/ static void -save_reductions (void) +save_reductions (state_t *state) { 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. */ for (i = 0; i < nritemset; ++i) { 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. */ - this_state->reductions = reductions_new (count); - memcpy (this_state->reductions->rules, redset, count * sizeof (redset[0])); + state_reductions_set (state, count, redset); } @@ -387,25 +304,32 @@ save_reductions (void) static void set_states (void) { - state_t *sp; 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 - 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. | @@ -414,34 +338,44 @@ set_states (void) void generate_states (void) { + state_list_t *list = NULL; 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", - this_state->number, - symbol_tag_get (symbols[this_state->accessing_symbol])); + 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. */ - 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 */