/* Compute look-ahead criteria for bison, Copyright (C) 1984, 1986, 1989 Free Software Foundation, Inc. This file is part of Bison, the GNU Compiler Compiler. Bison is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. Bison is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with Bison; see the file COPYING. If not, write to the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */ /* Compute how to make the finite state machine deterministic; find which rules need lookahead in each state, and which lookahead tokens they accept. lalr(), the entry point, builds these data structures: goto_map, from_state and to_state record each shift transition which accepts a variable (a nonterminal). ngotos is the number of such transitions. from_state[t] is the state number which a transition leads from and to_state[t] is the state number it leads to. All the transitions that accept a particular variable are grouped together and goto_map[i - ntokens] is the index in from_state and to_state of the first of them. consistent[s] is nonzero if no lookahead is needed to decide what to do in state s. LAruleno is a vector which records the rules that need lookahead in various states. The elements of LAruleno that apply to state s are those from lookaheads[s] through lookaheads[s+1]-1. Each element of LAruleno is a rule number. If lr is the length of LAruleno, then a number from 0 to lr-1 can specify both a rule and a state where the rule might be applied. LA is a lr by ntokens matrix of bits. LA[l, i] is 1 if the rule LAruleno[l] is applicable in the appropriate state when the next token is symbol i. If LA[l, i] and LA[l, j] are both 1 for i != j, it is a conflict. */ #include <stdio.h> #include "system.h" #include "machine.h" #include "types.h" #include "state.h" #include "new.h" #include "gram.h" extern short **derives; extern char *nullable; int tokensetsize; short *lookaheads; short *LAruleno; unsigned *LA; short *accessing_symbol; char *consistent; core **state_table; shifts **shift_table; reductions **reduction_table; short *goto_map; short *from_state; short *to_state; short **transpose(short**,int); void set_state_table(); void set_accessing_symbol(); void set_shift_table(); void set_reduction_table(); void set_maxrhs(); void initialize_LA(); void set_goto_map(); void initialize_F(); void build_relations(); void add_lookback_edge(int,int,int); void compute_FOLLOWS(); void compute_lookaheads(); void digraph(short**); void traverse(int); extern void toomany(char*); extern void berror(char*); static int infinity; static int maxrhs; static int ngotos; static unsigned *F; static short **includes; static shorts **lookback; static short **R; static short *INDEX; static short *VERTICES; static int top; void lalr() { tokensetsize = WORDSIZE(ntokens); set_state_table(); set_accessing_symbol(); set_shift_table(); set_reduction_table(); set_maxrhs(); initialize_LA(); set_goto_map(); initialize_F(); build_relations(); compute_FOLLOWS(); compute_lookaheads(); } void set_state_table() { register core *sp; state_table = NEW2(nstates, core *); for (sp = first_state; sp; sp = sp->next) state_table[sp->number] = sp; } void set_accessing_symbol() { register core *sp; accessing_symbol = NEW2(nstates, short); for (sp = first_state; sp; sp = sp->next) accessing_symbol[sp->number] = sp->accessing_symbol; } void set_shift_table() { register shifts *sp; shift_table = NEW2(nstates, shifts *); for (sp = first_shift; sp; sp = sp->next) shift_table[sp->number] = sp; } void set_reduction_table() { register reductions *rp; reduction_table = NEW2(nstates, reductions *); for (rp = first_reduction; rp; rp = rp->next) reduction_table[rp->number] = rp; } void set_maxrhs() { register short *itemp; register int length; register int max; length = 0; max = 0; for (itemp = ritem; *itemp; itemp++) { if (*itemp > 0) { length++; } else { if (length > max) max = length; length = 0; } } maxrhs = max; } void initialize_LA() { register int i; register int j; register int count; register reductions *rp; register shifts *sp; register short *np; consistent = NEW2(nstates, char); lookaheads = NEW2(nstates + 1, short); count = 0; for (i = 0; i < nstates; i++) { register int k; lookaheads[i] = count; rp = reduction_table[i]; sp = shift_table[i]; if (rp && (rp->nreds > 1 || (sp && ! ISVAR(accessing_symbol[sp->internalShifts[0]])))) count += rp->nreds; else consistent[i] = 1; if (sp) for (k = 0; k < sp->nshifts; k++) { if (accessing_symbol[sp->internalShifts[k]] == error_token_number) { consistent[i] = 0; break; } } } lookaheads[nstates] = count; if (count == 0) { LA = NEW2(1 * tokensetsize, unsigned); LAruleno = NEW2(1, short); lookback = NEW2(1, shorts *); } else { LA = NEW2(count * tokensetsize, unsigned); LAruleno = NEW2(count, short); lookback = NEW2(count, shorts *); } np = LAruleno; for (i = 0; i < nstates; i++) { if (!consistent[i]) { if (rp = reduction_table[i]) for (j = 0; j < rp->nreds; j++) *np++ = rp->rules[j]; } } } void set_goto_map() { register shifts *sp; register int i; register int symbol; register int k; register short *temp_map; register int state2; register int state1; goto_map = NEW2(nvars + 1, short) - ntokens; temp_map = NEW2(nvars + 1, short) - ntokens; ngotos = 0; for (sp = first_shift; sp; sp = sp->next) { for (i = sp->nshifts - 1; i >= 0; i--) { symbol = accessing_symbol[sp->internalShifts[i]]; if (ISTOKEN(symbol)) break; if (ngotos == MAXSHORT) toomany("gotos"); ngotos++; goto_map[symbol]++; } } k = 0; for (i = ntokens; i < nsyms; i++) { temp_map[i] = k; k += goto_map[i]; } for (i = ntokens; i < nsyms; i++) goto_map[i] = temp_map[i]; goto_map[nsyms] = ngotos; temp_map[nsyms] = ngotos; from_state = NEW2(ngotos, short); to_state = NEW2(ngotos, short); for (sp = first_shift; sp; sp = sp->next) { state1 = sp->number; for (i = sp->nshifts - 1; i >= 0; i--) { state2 = sp->internalShifts[i]; symbol = accessing_symbol[state2]; if (ISTOKEN(symbol)) break; k = temp_map[symbol]++; from_state[k] = state1; to_state[k] = state2; } } FREE(temp_map + ntokens); } /* Map_goto maps a state/symbol pair into its numeric representation. */ int map_goto(int state, int symbol) { register int high; register int low; register int middle; register int s; low = goto_map[symbol]; high = goto_map[symbol + 1] - 1; while (low <= high) { middle = (low + high) / 2; s = from_state[middle]; if (s == state) return (middle); else if (s < state) low = middle + 1; else high = middle - 1; } berror("map_goto"); /* NOTREACHED */ return 0; } void initialize_F() { register int i; register int j; register int k; register shifts *sp; register short *edge; register unsigned *rowp; register short *rp; register short **reads; register int nedges; register int stateno; register int symbol; register int nwords; nwords = ngotos * tokensetsize; F = NEW2(nwords, unsigned); reads = NEW2(ngotos, short *); edge = NEW2(ngotos + 1, short); nedges = 0; rowp = F; for (i = 0; i < ngotos; i++) { stateno = to_state[i]; sp = shift_table[stateno]; if (sp) { k = sp->nshifts; for (j = 0; j < k; j++) { symbol = accessing_symbol[sp->internalShifts[j]]; if (ISVAR(symbol)) break; SETBIT(rowp, symbol); } for (; j < k; j++) { symbol = accessing_symbol[sp->internalShifts[j]]; if (nullable[symbol]) edge[nedges++] = map_goto(stateno, symbol); } if (nedges) { reads[i] = rp = NEW2(nedges + 1, short); for (j = 0; j < nedges; j++) rp[j] = edge[j]; rp[nedges] = -1; nedges = 0; } } rowp += tokensetsize; } digraph(reads); for (i = 0; i < ngotos; i++) { if (reads[i]) FREE(reads[i]); } FREE(reads); FREE(edge); } void build_relations() { register int i; register int j; register int k; register short *rulep; register short *rp; register shifts *sp; register int length; register int nedges; register int done; register int state1; register int stateno; register int symbol1; register int symbol2; register short *shortp; register short *edge; register short *states; register short **new_includes; includes = NEW2(ngotos, short *); edge = NEW2(ngotos + 1, short); states = NEW2(maxrhs + 1, short); for (i = 0; i < ngotos; i++) { nedges = 0; state1 = from_state[i]; symbol1 = accessing_symbol[to_state[i]]; for (rulep = derives[symbol1]; *rulep > 0; rulep++) { length = 1; states[0] = state1; stateno = state1; for (rp = ritem + rrhs[*rulep]; *rp > 0; rp++) { symbol2 = *rp; sp = shift_table[stateno]; k = sp->nshifts; for (j = 0; j < k; j++) { stateno = sp->internalShifts[j]; if (accessing_symbol[stateno] == symbol2) break; } states[length++] = stateno; } if (!consistent[stateno]) add_lookback_edge(stateno, *rulep, i); length--; done = 0; while (!done) { done = 1; rp--; /* JF added rp>=ritem && I hope to god its right! */ if (rp>=ritem && ISVAR(*rp)) { stateno = states[--length]; edge[nedges++] = map_goto(stateno, *rp); if (nullable[*rp]) done = 0; } } } if (nedges) { includes[i] = shortp = NEW2(nedges + 1, short); for (j = 0; j < nedges; j++) shortp[j] = edge[j]; shortp[nedges] = -1; } } new_includes = transpose(includes, ngotos); for (i = 0; i < ngotos; i++) if (includes[i]) FREE(includes[i]); FREE(includes); includes = new_includes; FREE(edge); FREE(states); } void add_lookback_edge(int stateno, int ruleno, int gotono) { register int i; register int k; register int found; register shorts *sp; i = lookaheads[stateno]; k = lookaheads[stateno + 1]; found = 0; while (!found && i < k) { if (LAruleno[i] == ruleno) found = 1; else i++; } if (found == 0) berror("add_lookback_edge"); sp = NEW(shorts); sp->next = lookback[i]; sp->value = gotono; lookback[i] = sp; } short ** transpose(short** R_arg, int n) { register short **new_R; register short **temp_R; register short *nedges; register short *sp; register int i; register int k; nedges = NEW2(n, short); for (i = 0; i < n; i++) { sp = R_arg[i]; if (sp) { while (*sp >= 0) nedges[*sp++]++; } } new_R = NEW2(n, short *); temp_R = NEW2(n, short *); for (i = 0; i < n; i++) { k = nedges[i]; if (k > 0) { sp = NEW2(k + 1, short); new_R[i] = sp; temp_R[i] = sp; sp[k] = -1; } } FREE(nedges); for (i = 0; i < n; i++) { sp = R_arg[i]; if (sp) { while (*sp >= 0) *temp_R[*sp++]++ = i; } } FREE(temp_R); return (new_R); } void compute_FOLLOWS() { register int i; digraph(includes); for (i = 0; i < ngotos; i++) { if (includes[i]) FREE(includes[i]); } FREE(includes); } void compute_lookaheads() { register int i; register int n; register unsigned *fp1; register unsigned *fp2; register unsigned *fp3; register shorts *sp; register unsigned *rowp; /* register short *rulep; JF unused */ /* register int count; JF unused */ register shorts *sptmp;/* JF */ rowp = LA; n = lookaheads[nstates]; for (i = 0; i < n; i++) { fp3 = rowp + tokensetsize; for (sp = lookback[i]; sp; sp = sp->next) { fp1 = rowp; fp2 = F + tokensetsize * sp->value; while (fp1 < fp3) *fp1++ |= *fp2++; } rowp = fp3; } for (i = 0; i < n; i++) {/* JF removed ref to freed storage */ for (sp = lookback[i]; sp; sp = sptmp) { sptmp=sp->next; FREE(sp); } } FREE(lookback); FREE(F); } void digraph(short** relation) { register int i; infinity = ngotos + 2; INDEX = NEW2(ngotos + 1, short); VERTICES = NEW2(ngotos + 1, short); top = 0; R = relation; for (i = 0; i < ngotos; i++) INDEX[i] = 0; for (i = 0; i < ngotos; i++) { if (INDEX[i] == 0 && R[i]) traverse(i); } FREE(INDEX); FREE(VERTICES); } void traverse(int i) { register unsigned *fp1; register unsigned *fp2; register unsigned *fp3; register int j; register short *rp; int height; unsigned *base; VERTICES[++top] = i; INDEX[i] = height = top; base = F + i * tokensetsize; fp3 = base + tokensetsize; rp = R[i]; if (rp) { while ((j = *rp++) >= 0) { if (INDEX[j] == 0) traverse(j); if (INDEX[i] > INDEX[j]) INDEX[i] = INDEX[j]; fp1 = base; fp2 = F + j * tokensetsize; while (fp1 < fp3) *fp1++ |= *fp2++; } } if (INDEX[i] == height) { for (;;) { j = VERTICES[top--]; INDEX[j] = infinity; if (i == j) break; fp1 = base; fp2 = F + j * tokensetsize; while (fp1 < fp3) *fp2++ = *fp1++; } } }