X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/37c82725c8235e260f68f14308370be2d75f56dd..30171f79ab0aaad06b88a66653789691c4ed4f2c:/src/LR0.c diff --git a/src/LR0.c b/src/LR0.c index 9de75782..c1a0a8c1 100644 --- a/src/LR0.c +++ b/src/LR0.c @@ -36,11 +36,9 @@ int nstates; int final_state; static state_t *first_state = NULL; -static shifts *first_shift = 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 +68,8 @@ 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]]++; @@ -154,7 +152,7 @@ new_itemsets (void) for (i = 0; i < nitemset; ++i) { int symbol = ritem[itemset[i]]; - if (symbol > 0) + if (symbol >= 0) { if (!kernel_size[symbol]) { @@ -198,6 +196,10 @@ 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; } @@ -318,235 +320,8 @@ static void save_shifts (void) { shifts *p = shifts_new (nshifts); - - p->number = this_state->number; shortcpy (p->shifts, shiftset, nshifts); this_state->shifts = p; - - 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. | -| | -| The task of this state consists in shifting (actually, it's a | -| goto, but shifts and gotos are both stored in SHIFTS) the start | -| symbols, hence the name. | -`------------------------------------------------------------------*/ - -static void -insert_start_shifting_state (void) -{ - state_t *statep; - shifts *sp; - - statep = STATE_ALLOC (0); - statep->number = nstates; - - /* The distinctive feature of this state from the - eof_shifting_state, is that it is labeled as post-start-symbol - shifting. I fail to understand why this state, and the - post-start-start can't be merged into one. But it does fail if - you try. --akim */ - 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); - statep->shifts = sp; - sp->number = nstates++; - sp->shifts[0] = nstates; - - last_shift->next = sp; - last_shift = sp; -} - - -/*-----------------------------------------------------------------. -| Subroutine of augment_automaton. Create the final state, which | -| shifts `0', the end of file. The initial state shifts the start | -| symbol, and goes to here. | -`-----------------------------------------------------------------*/ - -static void -insert_eof_shifting_state (void) -{ - state_t *statep; - shifts *sp; - - /* 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); - statep->shifts = sp; - sp->number = nstates++; - sp->shifts[0] = nstates; - - last_shift->next = sp; - last_shift = sp; -} - - -/*---------------------------------------------------------------. -| Subroutine of augment_automaton. Create the accepting state. | -`---------------------------------------------------------------*/ - -static void -insert_accepting_state (void) -{ - state_t *statep; - - /* 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; -} - - - - - -/*------------------------------------------------------------------. -| 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) -{ - if (!first_state->shifts->nshifts) - { - /* The first state has no shifts. Make one shift, from the - initial state to the next-to-final state. */ - - shifts *sp = shifts_new (1); - first_state->shifts = sp; - 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_shifting_state (); - } - else - { - state_t *statep = first_state->next; - shifts *sp = first_shift; - shifts *sp1 = NULL; - /* 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; - statep->shifts = sp2; - 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; - statep->shifts = sp2; - 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; - sp = first_shift; - - /* 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). */ - sp2 = shifts_new (sp->nshifts + 1); - first_state->shifts = sp2; - /* 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_shifting_state (); - } - } - - insert_eof_shifting_state (); - insert_accepting_state (); } @@ -559,12 +334,15 @@ 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]]; @@ -573,15 +351,8 @@ save_reductions (void) } /* Make a reductions structure and copy the data into it. */ - - if (count) - { - reductions *p = REDUCTIONS_ALLOC (count); - p->nreds = count; - shortcpy (p->rules, redset, count); - - this_state->reductions = p; - } + this_state->reductions = reductions_new (count); + shortcpy (this_state->reductions->rules, redset, count); } @@ -592,58 +363,23 @@ save_reductions (void) static void set_state_table (void) { - /* NSTATES + 1 because lookahead for the pseudo state number NSTATES - might be used (see conflicts.c). It is too opaque for me to - provide a probably less hacky implementation. --akim */ - state_table = XCALLOC (state_t *, nstates + 1); - - { - state_t *sp; - for (sp = first_state; sp; sp = sp->next) - state_table[sp->number] = sp; - } - - /* Pessimization, but simplification of the code: make sure all the - states have a shifts, even if reduced to 0 shifts. */ - { - int i; - for (i = 0; i < nstates; i++) - if (!state_table[i]->shifts) - state_table[i]->shifts = shifts_new (0); - } - - /* Initializing the lookaheads members. Please note that it must be - performed after having set some of the other members which are - used below. Change with extreme caution. */ - { - int i; - int count = 0; - for (i = 0; i < nstates; i++) - { - int k; - reductions *rp = state_table[i]->reductions; - shifts *sp = state_table[i]->shifts; - - state_table[i]->lookaheads = count; - - if (rp - && (rp->nreds > 1 || (sp->nshifts && SHIFT_IS_SHIFT (sp, 0)))) - count += rp->nreds; - else - state_table[i]->consistent = 1; + state_t *sp; + state_table = XCALLOC (state_t *, nstates); - for (k = 0; k < sp->nshifts; k++) - if (SHIFT_IS_ERROR (sp, k)) - { - state_table[i]->consistent = 0; - break; - } - } + 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); - /* Seems to be needed by conflicts.c. */ - state_table[nstates] = STATE_ALLOC (0); - state_table[nstates]->lookaheads = count; - } + state_table[sp->number] = sp; + } } /*-------------------------------------------------------------------. @@ -687,9 +423,6 @@ generate_states (void) free_closure (); free_storage (); - /* set up initial and final states as parser wants them */ - augment_automaton (); - /* Set up STATE_TABLE. */ set_state_table (); }