X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/23cbcc6c19c08edbede56f177fdde9d6f74d4e4f..4ec8e00f609b4a44c3c9e5a25c82706b393a0e16:/src/LR0.c diff --git a/src/LR0.c b/src/LR0.c index f8fa5bd0..5e8caef0 100644 --- a/src/LR0.c +++ b/src/LR0.c @@ -30,18 +30,15 @@ #include "complain.h" #include "closure.h" #include "LR0.h" +#include "lalr.h" #include "reduce.h" int nstates; int final_state; -core *first_state = NULL; -shifts *first_shift = NULL; -reductions *first_reduction = NULL; +static state_t *first_state = NULL; -static core *this_state = NULL; -static core *last_state = NULL; -static shifts *last_shift = NULL; -static reductions *last_reduction = NULL; +static state_t *this_state = NULL; +static state_t *last_state = NULL; static int nshifts; static short *shift_symbol = NULL; @@ -55,8 +52,8 @@ static short *kernel_items = NULL; /* hash table for states, to recognize equivalent ones. */ -#define STATE_TABLE_SIZE 1009 -static core **state_table = NULL; +#define STATE_HASH_SIZE 1009 +static state_t **state_hash = NULL; static void @@ -107,7 +104,7 @@ allocate_storage (void) shiftset = XCALLOC (short, nsyms); redset = XCALLOC (short, nrules + 1); - state_table = XCALLOC (core *, STATE_TABLE_SIZE); + state_hash = XCALLOC (state_t *, STATE_HASH_SIZE); } @@ -120,7 +117,7 @@ free_storage (void) free (kernel_base); free (kernel_size); XFREE (kernel_items); - free (state_table); + free (state_hash); } @@ -141,7 +138,6 @@ static void new_itemsets (void) { int i; - int shiftcount; if (trace_flag) fprintf (stderr, "Entering new_itemsets, state = %d\n", @@ -151,25 +147,23 @@ new_itemsets (void) kernel_size[i] = 0; shift_symbol = XCALLOC (short, nsyms); - shiftcount = 0; + nshifts = 0; - for (i = 0; i < itemsetsize; ++i) + for (i = 0; i < nitemset; ++i) { int symbol = ritem[itemset[i]]; if (symbol > 0) { if (!kernel_size[symbol]) { - shift_symbol[shiftcount] = symbol; - shiftcount++; + shift_symbol[nshifts] = symbol; + nshifts++; } kernel_base[symbol][kernel_size[symbol]] = itemset[i] + 1; kernel_size[symbol]++; } } - - nshifts = shiftcount; } @@ -179,10 +173,10 @@ new_itemsets (void) | necessary. | `-----------------------------------------------------------------*/ -static core * +static state_t * new_state (int symbol) { - core *p; + state_t *p; if (trace_flag) fprintf (stderr, "Entering new_state, state = %d, symbol = %d (%s)\n", @@ -191,7 +185,7 @@ new_state (int symbol) if (nstates >= MAXSHORT) fatal (_("too many states (max %d)"), MAXSHORT); - p = CORE_ALLOC (kernel_size[symbol]); + p = STATE_ALLOC (kernel_size[symbol]); p->accessing_symbol = symbol; p->number = nstates; p->nitems = kernel_size[symbol]; @@ -217,7 +211,7 @@ get_state (int symbol) { int key; int i; - core *sp; + state_t *sp; if (trace_flag) fprintf (stderr, "Entering get_state, state = %d, symbol = %d (%s)\n", @@ -228,8 +222,8 @@ get_state (int symbol) key = 0; for (i = 0; i < kernel_size[symbol]; ++i) key += kernel_base[symbol][i]; - key = key % STATE_TABLE_SIZE; - sp = state_table[key]; + key = key % STATE_HASH_SIZE; + sp = state_hash[key]; if (sp) { @@ -260,7 +254,7 @@ get_state (int symbol) } else /* bucket is empty */ { - state_table[key] = sp = new_state (symbol); + state_hash[key] = sp = new_state (symbol); } if (trace_flag) @@ -309,7 +303,7 @@ append_states (void) static void new_states (void) { - first_state = last_state = this_state = CORE_ALLOC (0); + first_state = last_state = this_state = STATE_ALLOC (0); nstates = 1; } @@ -322,32 +316,34 @@ 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; + this_state->shifts = 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_shift (void) +insert_start_shifting_state (void) { - core *statep; + state_t *statep; shifts *sp; - statep = CORE_ALLOC (0); - statep->number = nstates; + 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; @@ -355,14 +351,63 @@ insert_start_shift (void) /* Make a shift from this state to (what will be) the final state. */ sp = shifts_new (1); - sp->number = nstates++; + statep->shifts = sp; + sp->shifts[0] = nstates; +} + + +/*-----------------------------------------------------------------. +| 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->shifts[0] = nstates; +} + + +/*---------------------------------------------------------------. +| 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; - last_shift->next = sp; - last_shift = sp; + /* 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 | @@ -374,156 +419,83 @@ insert_start_shift (void) static void augment_automaton (void) { - core *statep; - shifts *sp; - shifts *sp1 = NULL; - - sp = first_shift; - - if (!sp->nshifts) + if (!first_state->shifts->nshifts) { - /* There are no shifts for any state. Make one shift, from the + /* The first state has no shifts. Make one shift, from the initial state to the next-to-final state. */ - sp = shifts_new (1); + 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_shift (); + insert_start_shifting_state (); } - else if (sp->number == 0) + else { - statep = first_state->next; - + state_t *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) + 1..(SP->NSHIFTS). Look for one reached by START_SYMBOL. + This is typical of `start: start ... ;': there is a state + with the item `start: start . ...'. We want to add a `shift + on EOF to eof-shifting state here. */ + while (statep->accessing_symbol != start_symbol + && statep->number < first_state->shifts->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; - } + /* We already have STATEP, a next-to-final state for `start: + start . ...'. Make sure it has a shift to what will be + the final state. */ + int i; - 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; - } + /* Find the shift of the inital state that leads to STATEP. */ + shifts *sp = statep->shifts; + + shifts *sp1 = shifts_new (sp->nshifts + 1); + statep->shifts = sp1; + sp1->shifts[0] = nstates; + for (i = sp->nshifts; i > 0; i--) + sp1->shifts[i] = sp->shifts[i - 1]; + + XFREE (sp); + + insert_eof_shifting_state (); } else { + /* There is no state for `start: start . ...'. */ 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); + shifts *sp = first_state->shifts; + shifts *sp1 = NULL; + /* Add one more shift to the initial state, going to the + next-to-final state (yet to be made). */ + sp1 = shifts_new (sp->nshifts + 1); + first_state->shifts = sp1; /* 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]; + sp1->shifts[k++] = nstates; + sp1->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; + sp1->shifts[k++] = nstates; XFREE (sp); - /* Create the next-to-final state, with shift to - what will be the final state. */ - insert_start_shift (); + /* Create the next-to-final state, with shift to what will + be the final state. Corresponds to `start: start . ...'. */ + insert_start_shifting_state (); } } - 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 = CORE_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 = CORE_ALLOC (0); - statep->number = nstates++; - last_state->next = statep; - last_state = statep; + insert_accepting_state (); } @@ -542,7 +514,7 @@ save_reductions (void) /* Find and count the active items that represent ends of rules. */ count = 0; - for (i = 0; i < itemsetsize; ++i) + for (i = 0; i < nitemset; ++i) { int item = ritem[itemset[i]]; if (item < 0) @@ -554,21 +526,42 @@ save_reductions (void) if (count) { reductions *p = REDUCTIONS_ALLOC (count); - - p->number = this_state->number; p->nreds = count; - shortcpy (p->rules, redset, count); - if (last_reduction) - last_reduction->next = p; - else - first_reduction = p; - last_reduction = p; + this_state->reductions = p; } } +/*--------------------. +| Build STATE_TABLE. | +`--------------------*/ + +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); + } +} + /*-------------------------------------------------------------------. | Compute the nondeterministic finite state machine (see state.h for | | details) from the grammar. | @@ -612,4 +605,7 @@ generate_states (void) /* set up initial and final states as parser wants them */ augment_automaton (); + + /* Set up STATE_TABLE. */ + set_state_table (); }