mirror of
https://git.savannah.gnu.org/git/bison.git
synced 2026-03-10 04:43:03 +00:00
724 lines
12 KiB
C
724 lines
12 KiB
C
/* Compute look-ahead criteria for bison,
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Copyright 1984, 1986, 1989, 2000 Free Software Foundation, Inc.
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This file is part of Bison, the GNU Compiler Compiler.
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Bison is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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Bison is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with Bison; see the file COPYING. If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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/* Compute how to make the finite state machine deterministic; find
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which rules need lookahead in each state, and which lookahead
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tokens they accept. */
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#include "system.h"
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#include "types.h"
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#include "LR0.h"
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#include "xalloc.h"
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#include "gram.h"
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#include "complain.h"
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#include "lalr.h"
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#include "nullable.h"
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#include "derives.h"
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int tokensetsize;
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short *lookaheads;
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short *LAruleno;
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unsigned *LA;
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short *accessing_symbol;
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char *consistent;
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core **state_table;
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shifts **shift_table;
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reductions **reduction_table;
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short *goto_map;
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short *from_state;
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short *to_state;
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extern void berror PARAMS ((const char *));
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static int infinity;
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static int maxrhs;
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static int ngotos;
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static unsigned *F;
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static short **includes;
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static shorts **lookback;
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static short **R;
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static short *INDEX;
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static short *VERTICES;
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static int top;
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static void
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traverse (int i)
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{
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unsigned *fp1;
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unsigned *fp2;
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unsigned *fp3;
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int j;
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short *rp;
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int height;
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unsigned *base;
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VERTICES[++top] = i;
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INDEX[i] = height = top;
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base = F + i * tokensetsize;
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fp3 = base + tokensetsize;
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rp = R[i];
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if (rp)
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{
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while ((j = *rp++) >= 0)
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{
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if (INDEX[j] == 0)
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traverse (j);
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if (INDEX[i] > INDEX[j])
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INDEX[i] = INDEX[j];
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fp1 = base;
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fp2 = F + j * tokensetsize;
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while (fp1 < fp3)
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*fp1++ |= *fp2++;
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}
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}
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if (INDEX[i] == height)
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{
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for (;;)
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{
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j = VERTICES[top--];
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INDEX[j] = infinity;
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if (i == j)
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break;
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fp1 = base;
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fp2 = F + j * tokensetsize;
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while (fp1 < fp3)
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*fp2++ = *fp1++;
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}
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}
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}
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static void
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digraph (short **relation)
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{
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int i;
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infinity = ngotos + 2;
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INDEX = XCALLOC (short, ngotos + 1);
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VERTICES = XCALLOC (short, ngotos + 1);
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top = 0;
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R = relation;
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for (i = 0; i < ngotos; i++)
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INDEX[i] = 0;
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for (i = 0; i < ngotos; i++)
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{
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if (INDEX[i] == 0 && R[i])
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traverse (i);
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}
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XFREE (INDEX);
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XFREE (VERTICES);
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}
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static void
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set_state_table (void)
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{
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core *sp;
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state_table = XCALLOC (core *, nstates);
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for (sp = first_state; sp; sp = sp->next)
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state_table[sp->number] = sp;
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}
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static void
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set_accessing_symbol (void)
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{
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core *sp;
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accessing_symbol = XCALLOC (short, nstates);
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for (sp = first_state; sp; sp = sp->next)
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accessing_symbol[sp->number] = sp->accessing_symbol;
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}
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static void
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set_shift_table (void)
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{
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shifts *sp;
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shift_table = XCALLOC (shifts *, nstates);
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for (sp = first_shift; sp; sp = sp->next)
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shift_table[sp->number] = sp;
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}
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static void
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set_reduction_table (void)
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{
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reductions *rp;
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reduction_table = XCALLOC (reductions *, nstates);
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for (rp = first_reduction; rp; rp = rp->next)
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reduction_table[rp->number] = rp;
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}
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static void
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set_maxrhs (void)
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{
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short *itemp;
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int length;
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int max;
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length = 0;
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max = 0;
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for (itemp = ritem; *itemp; itemp++)
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{
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if (*itemp > 0)
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{
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length++;
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}
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else
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{
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if (length > max)
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max = length;
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length = 0;
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}
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}
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maxrhs = max;
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}
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static void
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initialize_LA (void)
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{
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int i;
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int j;
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int count;
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reductions *rp;
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shifts *sp;
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short *np;
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consistent = XCALLOC (char, nstates);
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lookaheads = XCALLOC (short, nstates + 1);
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count = 0;
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for (i = 0; i < nstates; i++)
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{
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int k;
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lookaheads[i] = count;
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rp = reduction_table[i];
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sp = shift_table[i];
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if (rp && (rp->nreds > 1
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|| (sp && !ISVAR (accessing_symbol[sp->shifts[0]]))))
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count += rp->nreds;
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else
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consistent[i] = 1;
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if (sp)
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for (k = 0; k < sp->nshifts; k++)
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{
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if (accessing_symbol[sp->shifts[k]] == error_token_number)
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{
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consistent[i] = 0;
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break;
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}
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}
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}
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lookaheads[nstates] = count;
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if (count == 0)
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{
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LA = XCALLOC (unsigned, 1 * tokensetsize);
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LAruleno = XCALLOC (short, 1);
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lookback = XCALLOC (shorts *, 1);
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}
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else
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{
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LA = XCALLOC (unsigned, count * tokensetsize);
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LAruleno = XCALLOC (short, count);
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lookback = XCALLOC (shorts *, count);
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}
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np = LAruleno;
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for (i = 0; i < nstates; i++)
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{
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if (!consistent[i])
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{
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if ((rp = reduction_table[i]))
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for (j = 0; j < rp->nreds; j++)
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*np++ = rp->rules[j];
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}
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}
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}
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static void
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set_goto_map (void)
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{
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shifts *sp;
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int i;
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int symbol;
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int k;
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short *temp_map;
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int state2;
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int state1;
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goto_map = XCALLOC (short, nvars + 1) - ntokens;
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temp_map = XCALLOC (short, nvars + 1) - ntokens;
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ngotos = 0;
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for (sp = first_shift; sp; sp = sp->next)
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{
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for (i = sp->nshifts - 1; i >= 0; i--)
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{
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symbol = accessing_symbol[sp->shifts[i]];
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if (ISTOKEN (symbol))
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break;
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if (ngotos == MAXSHORT)
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fatal (_("too many gotos (max %d)"), MAXSHORT);
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ngotos++;
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goto_map[symbol]++;
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}
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}
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k = 0;
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for (i = ntokens; i < nsyms; i++)
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{
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temp_map[i] = k;
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k += goto_map[i];
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}
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for (i = ntokens; i < nsyms; i++)
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goto_map[i] = temp_map[i];
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goto_map[nsyms] = ngotos;
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temp_map[nsyms] = ngotos;
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from_state = XCALLOC (short, ngotos);
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to_state = XCALLOC (short, ngotos);
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for (sp = first_shift; sp; sp = sp->next)
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{
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state1 = sp->number;
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for (i = sp->nshifts - 1; i >= 0; i--)
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{
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state2 = sp->shifts[i];
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symbol = accessing_symbol[state2];
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if (ISTOKEN (symbol))
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break;
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k = temp_map[symbol]++;
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from_state[k] = state1;
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to_state[k] = state2;
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}
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}
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XFREE (temp_map + ntokens);
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}
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/*----------------------------------------------------------.
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| Map a state/symbol pair into its numeric representation. |
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`----------------------------------------------------------*/
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static int
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map_goto (int state, int symbol)
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{
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int high;
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int low;
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int middle;
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int s;
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low = goto_map[symbol];
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high = goto_map[symbol + 1] - 1;
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while (low <= high)
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{
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middle = (low + high) / 2;
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s = from_state[middle];
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if (s == state)
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return middle;
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else if (s < state)
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low = middle + 1;
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else
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high = middle - 1;
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}
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assert (0);
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/* NOTREACHED */
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return 0;
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}
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static void
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initialize_F (void)
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{
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int i;
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int j;
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int k;
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shifts *sp;
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short *edge;
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unsigned *rowp;
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short *rp;
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short **reads;
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int nedges;
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int stateno;
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int symbol;
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int nwords;
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nwords = ngotos * tokensetsize;
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F = XCALLOC (unsigned, nwords);
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reads = XCALLOC (short *, ngotos);
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edge = XCALLOC (short, ngotos + 1);
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nedges = 0;
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rowp = F;
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for (i = 0; i < ngotos; i++)
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{
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stateno = to_state[i];
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sp = shift_table[stateno];
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if (sp)
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{
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k = sp->nshifts;
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for (j = 0; j < k; j++)
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{
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symbol = accessing_symbol[sp->shifts[j]];
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if (ISVAR (symbol))
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break;
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SETBIT (rowp, symbol);
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}
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for (; j < k; j++)
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{
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symbol = accessing_symbol[sp->shifts[j]];
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if (nullable[symbol])
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edge[nedges++] = map_goto (stateno, symbol);
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}
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if (nedges)
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{
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reads[i] = rp = XCALLOC (short, nedges + 1);
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for (j = 0; j < nedges; j++)
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rp[j] = edge[j];
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rp[nedges] = -1;
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nedges = 0;
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}
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}
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rowp += tokensetsize;
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}
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digraph (reads);
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for (i = 0; i < ngotos; i++)
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{
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if (reads[i])
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XFREE (reads[i]);
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}
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XFREE (reads);
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XFREE (edge);
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}
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static void
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add_lookback_edge (int stateno, int ruleno, int gotono)
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{
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int i;
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int k;
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int found;
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shorts *sp;
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i = lookaheads[stateno];
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k = lookaheads[stateno + 1];
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found = 0;
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while (!found && i < k)
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{
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if (LAruleno[i] == ruleno)
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found = 1;
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else
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i++;
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}
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assert (found);
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sp = XCALLOC (shorts, 1);
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sp->next = lookback[i];
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sp->value = gotono;
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lookback[i] = sp;
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}
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static short **
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transpose (short **R_arg, int n)
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{
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short **new_R;
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short **temp_R;
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short *nedges;
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short *sp;
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int i;
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int k;
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nedges = XCALLOC (short, n);
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for (i = 0; i < n; i++)
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{
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sp = R_arg[i];
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if (sp)
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{
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while (*sp >= 0)
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nedges[*sp++]++;
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}
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}
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new_R = XCALLOC (short *, n);
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temp_R = XCALLOC (short *, n);
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for (i = 0; i < n; i++)
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{
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k = nedges[i];
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if (k > 0)
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{
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sp = XCALLOC (short, k + 1);
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new_R[i] = sp;
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temp_R[i] = sp;
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sp[k] = -1;
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}
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}
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XFREE (nedges);
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for (i = 0; i < n; i++)
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{
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sp = R_arg[i];
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if (sp)
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{
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while (*sp >= 0)
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*temp_R[*sp++]++ = i;
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}
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}
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XFREE (temp_R);
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return new_R;
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}
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static void
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build_relations (void)
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{
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int i;
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int j;
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int k;
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short *rulep;
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short *rp;
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shifts *sp;
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int length;
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int nedges;
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int done;
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int state1;
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int stateno;
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int symbol1;
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int symbol2;
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short *shortp;
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short *edge;
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short *states;
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short **new_includes;
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includes = XCALLOC (short *, ngotos);
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edge = XCALLOC (short, ngotos + 1);
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states = XCALLOC (short, maxrhs + 1);
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for (i = 0; i < ngotos; i++)
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{
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nedges = 0;
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state1 = from_state[i];
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symbol1 = accessing_symbol[to_state[i]];
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for (rulep = derives[symbol1]; *rulep > 0; rulep++)
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{
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length = 1;
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states[0] = state1;
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stateno = state1;
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for (rp = ritem + rrhs[*rulep]; *rp > 0; rp++)
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{
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symbol2 = *rp;
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sp = shift_table[stateno];
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k = sp->nshifts;
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for (j = 0; j < k; j++)
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{
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stateno = sp->shifts[j];
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if (accessing_symbol[stateno] == symbol2)
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break;
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}
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states[length++] = stateno;
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}
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|
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if (!consistent[stateno])
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add_lookback_edge (stateno, *rulep, i);
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length--;
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done = 0;
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while (!done)
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{
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done = 1;
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rp--;
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/* JF added rp>=ritem && I hope to god its right! */
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if (rp >= ritem && ISVAR (*rp))
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{
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stateno = states[--length];
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edge[nedges++] = map_goto (stateno, *rp);
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if (nullable[*rp])
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done = 0;
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}
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}
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}
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if (nedges)
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{
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includes[i] = shortp = XCALLOC (short, nedges + 1);
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for (j = 0; j < nedges; j++)
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shortp[j] = edge[j];
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shortp[nedges] = -1;
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}
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}
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new_includes = transpose (includes, ngotos);
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|
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for (i = 0; i < ngotos; i++)
|
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if (includes[i])
|
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XFREE (includes[i]);
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|
|
XFREE (includes);
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|
|
includes = new_includes;
|
|
|
|
XFREE (edge);
|
|
XFREE (states);
|
|
}
|
|
|
|
|
|
|
|
static void
|
|
compute_FOLLOWS (void)
|
|
{
|
|
int i;
|
|
|
|
digraph (includes);
|
|
|
|
for (i = 0; i < ngotos; i++)
|
|
{
|
|
if (includes[i])
|
|
XFREE (includes[i]);
|
|
}
|
|
|
|
XFREE (includes);
|
|
}
|
|
|
|
|
|
static void
|
|
compute_lookaheads (void)
|
|
{
|
|
int i;
|
|
int n;
|
|
unsigned *fp1;
|
|
unsigned *fp2;
|
|
unsigned *fp3;
|
|
shorts *sp;
|
|
unsigned *rowp;
|
|
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;
|
|
XFREE (sp);
|
|
}
|
|
}
|
|
|
|
XFREE (lookback);
|
|
XFREE (F);
|
|
}
|
|
|
|
|
|
void
|
|
lalr (void)
|
|
{
|
|
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 ();
|
|
}
|