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Current File : //usr/src/usr.bin/yacc/lr0.c |
/* * Copyright (c) 1989 The Regents of the University of California. * All rights reserved. * * This code is derived from software contributed to Berkeley by * Robert Paul Corbett. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #if 0 #ifndef lint static char sccsid[] = "@(#)lr0.c 5.3 (Berkeley) 1/20/91"; #endif #endif #include <sys/cdefs.h> __FBSDID("$FreeBSD: release/9.1.0/usr.bin/yacc/lr0.c 216370 2010-12-11 08:32:16Z joel $"); #include <limits.h> #include <stdlib.h> #include "defs.h" extern short *itemset; extern short *itemsetend; extern unsigned *ruleset; int nstates; core *first_state; shifts *first_shift; reductions *first_reduction; static void allocate_itemsets(void); static void allocate_storage(void); static void append_states(void); static void free_storage(void); static void generate_states(void); static int get_state(int); static void initialize_states(void); static void new_itemsets(void); static core *new_state(int); #ifdef DEBUG static void print_derives(void); #endif static void save_reductions(void); static void save_shifts(void); static void set_derives(void); static void set_nullable(void); static core **state_set; static core *this_state; static core *last_state; static shifts *last_shift; static reductions *last_reduction; static int nshifts; static short *shift_symbol; static short *redset; static short *shiftset; static short **kernel_base; static short **kernel_end; static short *kernel_items; static void allocate_itemsets(void) { short *itemp; short *item_end; int symbol; int i; int count; int max; short *symbol_count; count = 0; symbol_count = NEW2(nsyms, short); item_end = ritem + nitems; for (itemp = ritem; itemp < item_end; itemp++) { symbol = *itemp; if (symbol >= 0) { count++; symbol_count[symbol]++; } } kernel_base = NEW2(nsyms, short *); kernel_items = NEW2(count, short); count = 0; max = 0; for (i = 0; i < nsyms; i++) { kernel_base[i] = kernel_items + count; count += symbol_count[i]; if (max < symbol_count[i]) max = symbol_count[i]; } shift_symbol = symbol_count; kernel_end = NEW2(nsyms, short *); } static void allocate_storage(void) { allocate_itemsets(); shiftset = NEW2(nsyms, short); redset = NEW2(nrules + 1, short); state_set = NEW2(nitems, core *); } static void append_states(void) { int i; int j; int symbol; #ifdef TRACE fprintf(stderr, "Entering append_states()\n"); #endif for (i = 1; i < nshifts; i++) { symbol = shift_symbol[i]; j = i; while (j > 0 && shift_symbol[j - 1] > symbol) { shift_symbol[j] = shift_symbol[j - 1]; j--; } shift_symbol[j] = symbol; } for (i = 0; i < nshifts; i++) { symbol = shift_symbol[i]; shiftset[i] = get_state(symbol); } } static void free_storage(void) { free(shift_symbol); free(redset); free(shiftset); free(kernel_base); free(kernel_end); free(kernel_items); free(state_set); } static void generate_states(void) { allocate_storage(); itemset = NEW2(nitems, short); ruleset = NEW2(WORDSIZE(nrules), unsigned); set_first_derives(); initialize_states(); while (this_state) { closure(this_state->items, this_state->nitems); save_reductions(); new_itemsets(); append_states(); if (nshifts > 0) save_shifts(); this_state = this_state->next; } finalize_closure(); free_storage(); } static int get_state(int symbol) { int key; short *isp1; short *isp2; short *iend; core *sp; int found; int n; #ifdef TRACE fprintf(stderr, "Entering get_state(%d)\n", symbol); #endif isp1 = kernel_base[symbol]; iend = kernel_end[symbol]; n = iend - isp1; key = *isp1; assert(0 <= key && key < nitems); sp = state_set[key]; if (sp) { found = 0; while (!found) { if (sp->nitems == n) { found = 1; isp1 = kernel_base[symbol]; isp2 = sp->items; while (found && isp1 < iend) { if (*isp1++ != *isp2++) found = 0; } } if (!found) { if (sp->link) { sp = sp->link; } else { sp = sp->link = new_state(symbol); found = 1; } } } } else { state_set[key] = sp = new_state(symbol); } return (sp->number); } static void initialize_states(void) { int i; short *start_derives; core *p; start_derives = derives[start_symbol]; for (i = 0; start_derives[i] >= 0; ++i) continue; p = malloc(sizeof(core) + i*sizeof(short)); if (p == 0) no_space(); p->next = 0; p->link = 0; p->number = 0; p->accessing_symbol = 0; p->nitems = i; for (i = 0; start_derives[i] >= 0; ++i) p->items[i] = rrhs[start_derives[i]]; first_state = last_state = this_state = p; nstates = 1; } static void new_itemsets(void) { int i; int shiftcount; short *isp; short *ksp; int symbol; for (i = 0; i < nsyms; i++) kernel_end[i] = 0; shiftcount = 0; isp = itemset; while (isp < itemsetend) { i = *isp++; symbol = ritem[i]; if (symbol > 0) { ksp = kernel_end[symbol]; if (!ksp) { shift_symbol[shiftcount++] = symbol; ksp = kernel_base[symbol]; } *ksp++ = i + 1; kernel_end[symbol] = ksp; } } nshifts = shiftcount; } static core * new_state(int symbol) { int n; core *p; short *isp1; short *isp2; short *iend; #ifdef TRACE fprintf(stderr, "Entering new_state(%d)\n", symbol); #endif if (nstates >= SHRT_MAX) fatal("too many states"); isp1 = kernel_base[symbol]; iend = kernel_end[symbol]; n = iend - isp1; p = (core *) allocate((unsigned) (sizeof(core) + (n - 1) * sizeof(short))); p->accessing_symbol = symbol; p->number = nstates; p->nitems = n; isp2 = p->items; while (isp1 < iend) *isp2++ = *isp1++; last_state->next = p; last_state = p; nstates++; return (p); } #if 0 /* show_cores is used for debugging */ show_cores(void) { core *p; int i, j, k, n; int itemno; k = 0; for (p = first_state; p; ++k, p = p->next) { if (k) printf("\n"); printf("state %d, number = %d, accessing symbol = %s\n", k, p->number, symbol_name[p->accessing_symbol]); n = p->nitems; for (i = 0; i < n; ++i) { itemno = p->items[i]; printf("%4d ", itemno); j = itemno; while (ritem[j] >= 0) ++j; printf("%s :", symbol_name[rlhs[-ritem[j]]]); j = rrhs[-ritem[j]]; while (j < itemno) printf(" %s", symbol_name[ritem[j++]]); printf(" ."); while (ritem[j] >= 0) printf(" %s", symbol_name[ritem[j++]]); printf("\n"); fflush(stdout); } } } /* show_ritems is used for debugging */ show_ritems(void) { int i; for (i = 0; i < nitems; ++i) printf("ritem[%d] = %d\n", i, ritem[i]); } /* show_rrhs is used for debugging */ show_rrhs(void) { int i; for (i = 0; i < nrules; ++i) printf("rrhs[%d] = %d\n", i, rrhs[i]); } /* show_shifts is used for debugging */ show_shifts(void) { shifts *p; int i, j, k; k = 0; for (p = first_shift; p; ++k, p = p->next) { if (k) printf("\n"); printf("shift %d, number = %d, nshifts = %d\n", k, p->number, p->nshifts); j = p->nshifts; for (i = 0; i < j; ++i) printf("\t%d\n", p->shift[i]); } } #endif static void save_shifts(void) { shifts *p; short *sp1; short *sp2; short *send; p = (shifts *) allocate((unsigned) (sizeof(shifts) + (nshifts - 1) * sizeof(short))); p->number = this_state->number; p->nshifts = nshifts; sp1 = shiftset; sp2 = p->shift; send = shiftset + nshifts; while (sp1 < send) *sp2++ = *sp1++; if (last_shift) { last_shift->next = p; last_shift = p; } else { first_shift = p; last_shift = p; } } static void save_reductions(void) { short *isp; short *rp1; short *rp2; int item; int count; reductions *p; short *rend; count = 0; for (isp = itemset; isp < itemsetend; isp++) { item = ritem[*isp]; if (item < 0) { redset[count++] = -item; } } if (count) { p = (reductions *) allocate((unsigned) (sizeof(reductions) + (count - 1) * sizeof(short))); p->number = this_state->number; p->nreds = count; rp1 = redset; rp2 = p->rules; rend = rp1 + count; while (rp1 < rend) *rp2++ = *rp1++; if (last_reduction) { last_reduction->next = p; last_reduction = p; } else { first_reduction = p; last_reduction = p; } } } static void set_derives(void) { int i, k; int lhs; short *rules; derives = NEW2(nsyms, short *); rules = NEW2(nvars + nrules, short); k = 0; for (lhs = start_symbol; lhs < nsyms; lhs++) { derives[lhs] = rules + k; for (i = 0; i < nrules; i++) { if (rlhs[i] == lhs) { rules[k] = i; k++; } } rules[k] = -1; k++; } #ifdef DEBUG print_derives(); #endif } #if 0 free_derives() { free(derives[start_symbol]); free(derives); } #endif #ifdef DEBUG static void print_derives(void) { int i; short *sp; printf("\nDERIVES\n\n"); for (i = start_symbol; i < nsyms; i++) { printf("%s derives ", symbol_name[i]); for (sp = derives[i]; *sp >= 0; sp++) { printf(" %d", *sp); } putchar('\n'); } putchar('\n'); } #endif static void set_nullable(void) { int i, j; int empty; int done1; nullable = malloc(nsyms); if (nullable == 0) no_space(); for (i = 0; i < nsyms; ++i) nullable[i] = 0; done1 = 0; while (!done1) { done1 = 1; for (i = 1; i < nitems; i++) { empty = 1; while ((j = ritem[i]) >= 0) { if (!nullable[j]) empty = 0; ++i; } if (empty) { j = rlhs[-j]; if (!nullable[j]) { nullable[j] = 1; done1 = 0; } } } } #ifdef DEBUG for (i = 0; i < nsyms; i++) { if (nullable[i]) printf("%s is nullable\n", symbol_name[i]); else printf("%s is not nullable\n", symbol_name[i]); } #endif } #if 0 free_nullable(void) { free(nullable); } #endif void lr0(void) { set_derives(); set_nullable(); generate_states(); }