X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/49701457c2728ad7c77528205aa0bd1cb3379128..616429b50868bf9225d55143526442a024e32969:/src/LR0.c?ds=inline diff --git a/src/LR0.c b/src/LR0.c index 2dbd91e4..6a911f24 100644 --- a/src/LR0.c +++ b/src/LR0.c @@ -23,6 +23,7 @@ The entry point is generate_states. */ #include "system.h" +#include "symtab.h" #include "getargs.h" #include "reader.h" #include "gram.h" @@ -34,13 +35,18 @@ #include "reduce.h" int nstates; -int final_state; -state_t *first_state = NULL; -shifts *first_shift = NULL; +/* 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. + + 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_t *this_state = NULL; static state_t *last_state = NULL; -static shifts *last_shift = NULL; static int nshifts; static short *shift_symbol = NULL; @@ -70,8 +76,8 @@ allocate_itemsets (void) int count = 0; short *symbol_count = XCALLOC (short, nsyms + nuseless_nonterminals); - for (i = 0; ritem[i]; ++i) - if (ritem[i] > 0) + for (i = 0; i < nritems; ++i) + if (ritem[i] >= 0) { count++; symbol_count[ritem[i]]++; @@ -107,6 +113,7 @@ allocate_storage (void) shiftset = XCALLOC (short, nsyms); redset = XCALLOC (short, nrules + 1); state_hash = XCALLOC (state_t *, STATE_HASH_SIZE); + shift_symbol = XCALLOC (short, nsyms); } @@ -148,13 +155,12 @@ new_itemsets (void) for (i = 0; i < nsyms; i++) kernel_size[i] = 0; - shift_symbol = XCALLOC (short, nsyms); nshifts = 0; for (i = 0; i < nitemset; ++i) { int symbol = ritem[itemset[i]]; - if (symbol > 0) + if (symbol >= 0) { if (!kernel_size[symbol]) { @@ -182,7 +188,7 @@ new_state (int symbol) if (trace_flag) fprintf (stderr, "Entering new_state, state = %d, symbol = %d (%s)\n", - this_state->number, symbol, tags[symbol]); + this_state->number, symbol, symbols[symbol]->tag); if (nstates >= MAXSHORT) fatal (_("too many states (max %d)"), MAXSHORT); @@ -198,6 +204,10 @@ new_state (int symbol) last_state = p; nstates++; + /* If this is the eoftoken, then this is the final state. */ + if (symbol == 0) + final_state = p->number; + return p; } @@ -217,7 +227,7 @@ get_state (int symbol) if (trace_flag) fprintf (stderr, "Entering get_state, state = %d, symbol = %d (%s)\n", - this_state->number, symbol, tags[symbol]); + this_state->number, symbol, symbols[symbol]->tag); /* Add up the target state's active item numbers to get a hash key. */ @@ -318,208 +328,8 @@ static void save_shifts (void) { shifts *p = shifts_new (nshifts); - - p->number = this_state->number; - shortcpy (p->shifts, shiftset, nshifts); - - if (last_shift) - last_shift->next = p; - else - first_shift = p; - last_shift = p; -} - - -/*------------------------------------------------------------------. -| Subroutine of augment_automaton. Create the next-to-final state, | -| to which a shift has already been made in the initial state. | -`------------------------------------------------------------------*/ - -static void -insert_start_shift (void) -{ - state_t *statep; - shifts *sp; - - statep = STATE_ALLOC (0); - 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 = shifts_new (1); - sp->number = nstates++; - sp->shifts[0] = nstates; - - last_shift->next = sp; - last_shift = sp; -} - - -/*------------------------------------------------------------------. -| Make sure that the initial state has a shift that accepts the | -| grammar's start symbol and goes to the next-to-final state, which | -| has a shift going to the final state, which has a shift to the | -| termination state. Create such states and shifts if they don't | -| happen to exist already. | -`------------------------------------------------------------------*/ - -static void -augment_automaton (void) -{ - state_t *statep; - shifts *sp; - shifts *sp1 = NULL; - - sp = first_shift; - - if (!sp->nshifts) - { - /* There are no shifts for any state. Make one shift, from the - initial state to the next-to-final state. */ - - sp = shifts_new (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 (); - } - else if (sp->number == 0) - { - statep = first_state->next; - - /* The states reached by shifts from FIRST_STATE are numbered - 1..(SP->NSHIFTS). Look for one reached by START_SYMBOL. */ - while (statep->accessing_symbol < start_symbol - && statep->number < sp->nshifts) - statep = statep->next; - - if (statep->accessing_symbol == start_symbol) - { - /* We already have a next-to-final state. - Make sure it has a shift to what will be the final state. */ - while (sp && sp->number < statep->number) - { - sp1 = sp; - sp = sp->next; - } - - if (sp && sp->number == statep->number) - { - int i; - shifts *sp2 = shifts_new (sp->nshifts + 1); - sp2->number = statep->number; - sp2->shifts[0] = nstates; - for (i = sp->nshifts; i > 0; i--) - sp2->shifts[i] = sp->shifts[i - 1]; - - /* Patch sp2 into the chain of shifts in place of sp, - following sp1. */ - sp2->next = sp->next; - sp1->next = sp2; - if (sp == last_shift) - last_shift = sp2; - XFREE (sp); - } - else - { - shifts *sp2 = shifts_new (1); - sp2->number = statep->number; - sp2->shifts[0] = nstates; - - /* Patch sp2 into the chain of shifts between sp1 and sp. */ - sp2->next = sp; - sp1->next = sp2; - if (sp == 0) - last_shift = sp2; - } - } - else - { - int i, k; - shifts *sp2; - - /* There is no next-to-final state as yet. */ - /* Add one more shift in first_shift, - going to the next-to-final state (yet to be made). */ - sp = first_shift; - - sp2 = shifts_new (sp->nshifts + 1); - - /* Stick this shift into the vector at the proper place. */ - statep = first_state->next; - for (k = 0, i = 0; i < sp->nshifts; k++, i++) - { - if (statep->accessing_symbol > start_symbol && i == k) - sp2->shifts[k++] = nstates; - sp2->shifts[k] = sp->shifts[i]; - statep = statep->next; - } - if (i == k) - sp2->shifts[k++] = nstates; - - /* Patch sp2 into the chain of shifts - in place of sp, at the beginning. */ - sp2->next = sp->next; - first_shift = sp2; - if (last_shift == sp) - last_shift = sp2; - - XFREE (sp); - - /* Create the next-to-final state, with shift to - 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 = shifts_new (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 (); - } - - /* 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 = STATE_ALLOC (0); - statep->number = nstates; - last_state->next = statep; - last_state = statep; - - /* Make the shift from the final state to the termination state. */ - sp = shifts_new (1); - sp->number = nstates++; - 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 = STATE_ALLOC (0); - statep->number = nstates++; - last_state->next = statep; - last_state = statep; + this_state->shifts = p; } @@ -532,12 +342,15 @@ augment_automaton (void) static void save_reductions (void) { - int count; + int count = 0; int i; - /* Find and count the active items that represent ends of rules. */ + /* 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; - count = 0; + /* Find and count the active items that represent ends of rules. */ for (i = 0; i < nitemset; ++i) { int item = ritem[itemset[i]]; @@ -546,18 +359,37 @@ save_reductions (void) } /* Make a reductions structure and copy the data into it. */ + this_state->reductions = reductions_new (count); + shortcpy (this_state->reductions->rules, redset, count); +} - if (count) - { - reductions *p = REDUCTIONS_ALLOC (count); - p->nreds = count; - shortcpy (p->rules, redset, count); + +/*---------------. +| Build STATES. | +`---------------*/ - this_state->reductions = p; +static void +set_states (void) +{ + state_t *sp; + states = XCALLOC (state_t *, nstates); + + for (sp = first_state; sp; sp = sp->next) + { + /* 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; } } - /*-------------------------------------------------------------------. | Compute the nondeterministic finite state machine (see state.h for | | details) from the grammar. | @@ -567,14 +399,15 @@ void generate_states (void) { allocate_storage (); - new_closure (nitems); + new_closure (nritems); new_states (); while (this_state) { if (trace_flag) fprintf (stderr, "Processing state %d (reached by %s)\n", - this_state->number, tags[this_state->accessing_symbol]); + this_state->number, + symbols[this_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 @@ -599,6 +432,6 @@ generate_states (void) free_closure (); free_storage (); - /* set up initial and final states as parser wants them */ - augment_automaton (); + /* Set up STATES. */ + set_states (); }