-/* Compute look-ahead criteria for bison,
- Copyright 1984, 1986, 1989, 2000 Free Software Foundation, Inc.
+/* Compute look-ahead criteria for Bison.
+
+ Copyright (C) 1984, 1986, 1989, 2000, 2001, 2002, 2003, 2004
+ Free Software Foundation, Inc.
This file is part of Bison, the GNU Compiler Compiler.
/* Compute how to make the finite state machine deterministic; find
- which rules need lookahead in each state, and which lookahead
+ which rules need look-ahead in each state, and which look-ahead
tokens they accept. */
#include "system.h"
-#include "types.h"
+
+#include <bitset.h>
+#include <bitsetv.h>
+#include <quotearg.h>
+
#include "LR0.h"
-#include "gram.h"
#include "complain.h"
+#include "derives.h"
+#include "getargs.h"
+#include "gram.h"
#include "lalr.h"
#include "nullable.h"
-#include "derives.h"
+#include "reader.h"
+#include "relation.h"
+#include "symtab.h"
-/* All the decorated states, indexed by the state number. Warning:
- there is a state_TABLE in LR0.c, but it is different and static.
- */
-state_t *state_table = NULL;
+goto_number *goto_map;
+static goto_number ngotos;
+state_number *from_state;
+state_number *to_state;
-int tokensetsize;
-short *LAruleno;
-unsigned *LA;
-
-short *goto_map;
-short *from_state;
-short *to_state;
-
-extern void berror PARAMS ((const 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;
-
-
-static void
-traverse (int i)
+/* Linked list of goto numbers. */
+typedef struct goto_list
{
- unsigned *fp1;
- unsigned *fp2;
- unsigned *fp3;
- int j;
- short *rp;
-
- int height;
- unsigned *base;
+ struct goto_list *next;
+ goto_number value;
+} goto_list;
- VERTICES[++top] = i;
- INDEX[i] = height = top;
- base = F + i * tokensetsize;
- fp3 = base + tokensetsize;
+/* LA is a LR by NTOKENS matrix of bits. LA[l, i] is 1 if the rule
+ LArule[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. */
- rp = R[i];
- if (rp)
- {
- while ((j = *rp++) >= 0)
- {
- if (INDEX[j] == 0)
- traverse (j);
+static bitsetv LA = NULL;
+size_t nLA;
- 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;
+/* And for the famous F variable, which name is so descriptive that a
+ comment is hardly needed. <grin>. */
+static bitsetv F = NULL;
- if (i == j)
- break;
+static goto_number **includes;
+static goto_list **lookback;
- fp1 = base;
- fp2 = F + j * tokensetsize;
- while (fp1 < fp3)
- *fp2++ = *fp1++;
- }
- }
-}
-
-
-static void
-digraph (short **relation)
-{
- int i;
-
- infinity = ngotos + 2;
- INDEX = XCALLOC (short, ngotos + 1);
- VERTICES = XCALLOC (short, ngotos + 1);
- 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);
- }
-
- XFREE (INDEX);
- XFREE (VERTICES);
-}
-
-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);
-
- {
- core *sp;
- for (sp = first_state; sp; sp = sp->next)
- {
- state_table[sp->number].state = sp;
- state_table[sp->number].accessing_symbol = sp->accessing_symbol;
- }
- }
-
- {
- shifts *sp;
- for (sp = first_shift; sp; sp = sp->next)
- state_table[sp->number].shift_table = sp;
- }
-
- {
- reductions *rp;
- for (rp = first_reduction; rp; rp = rp->next)
- state_table[rp->number].reduction_table = rp;
- }
-}
-
-
-static void
-set_maxrhs (void)
-{
- short *itemp;
- int length;
- 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;
-}
-
-
-static void
-initialize_LA (void)
-{
- int i;
- int j;
- int count = 0;
- reductions *rp;
- shifts *sp;
- short *np;
-
- for (i = 0; i < nstates; i++)
- {
- int k;
-
- state_table[i].lookaheads = count;
-
- rp = state_table[i].reduction_table;
- sp = state_table[i].shift_table;
- if (rp
- && (rp->nreds > 1
- || (sp && !ISVAR (state_table[sp->shifts[0]].accessing_symbol))))
- count += rp->nreds;
- else
- state_table[i].consistent = 1;
-
- if (sp)
- for (k = 0; k < sp->nshifts; k++)
- if (state_table[sp->shifts[k]].accessing_symbol
- == error_token_number)
- {
- state_table[i].consistent = 0;
- break;
- }
- }
-
- state_table[nstates].lookaheads = count;
-
- if (count == 0)
- {
- LA = XCALLOC (unsigned, 1 * tokensetsize);
- LAruleno = XCALLOC (short, 1);
- lookback = XCALLOC (shorts *, 1);
- }
- else
- {
- LA = XCALLOC (unsigned, count * tokensetsize);
- LAruleno = XCALLOC (short, count);
- lookback = XCALLOC (shorts *, count);
- }
-
- np = LAruleno;
- for (i = 0; i < nstates; i++)
- {
- if (!state_table[i].consistent)
- {
- if ((rp = state_table[i].reduction_table))
- for (j = 0; j < rp->nreds; j++)
- *np++ = rp->rules[j];
- }
- }
-}
static void
set_goto_map (void)
{
- shifts *sp;
- int i;
- int symbol;
- int k;
- short *temp_map;
- int state2;
- int state1;
+ state_number s;
+ goto_number *temp_map;
- goto_map = XCALLOC (short, nvars + 1) - ntokens;
- temp_map = XCALLOC (short, nvars + 1) - ntokens;
+ goto_map = xcalloc (nvars + 1, sizeof *goto_map);
+ temp_map = xnmalloc (nvars + 1, sizeof *temp_map);
ngotos = 0;
- for (sp = first_shift; sp; sp = sp->next)
+ for (s = 0; s < nstates; ++s)
{
- for (i = sp->nshifts - 1; i >= 0; i--)
+ transitions *sp = states[s]->transitions;
+ int i;
+ for (i = sp->num - 1; i >= 0 && TRANSITION_IS_GOTO (sp, i); --i)
{
- symbol = state_table[sp->shifts[i]].accessing_symbol;
-
- if (ISTOKEN (symbol))
- break;
+ ngotos++;
- if (ngotos == MAXSHORT)
- fatal (_("too many gotos (max %d)"), MAXSHORT);
+ /* Abort if (ngotos + 1) would overflow. */
+ if (ngotos == GOTO_NUMBER_MAXIMUM)
+ abort ();
- ngotos++;
- goto_map[symbol]++;
+ goto_map[TRANSITION_SYMBOL (sp, i) - ntokens]++;
}
}
- k = 0;
- for (i = ntokens; i < nsyms; i++)
- {
- temp_map[i] = k;
- k += goto_map[i];
- }
+ {
+ goto_number k = 0;
+ int i;
+ for (i = ntokens; i < nsyms; i++)
+ {
+ temp_map[i - ntokens] = k;
+ k += goto_map[i - ntokens];
+ }
- for (i = ntokens; i < nsyms; i++)
- goto_map[i] = temp_map[i];
+ for (i = ntokens; i < nsyms; i++)
+ goto_map[i - ntokens] = temp_map[i - ntokens];
- goto_map[nsyms] = ngotos;
- temp_map[nsyms] = ngotos;
+ goto_map[nsyms - ntokens] = ngotos;
+ temp_map[nsyms - ntokens] = ngotos;
+ }
- from_state = XCALLOC (short, ngotos);
- to_state = XCALLOC (short, ngotos);
+ from_state = xcalloc (ngotos, sizeof *from_state);
+ to_state = xcalloc (ngotos, sizeof *to_state);
- for (sp = first_shift; sp; sp = sp->next)
+ for (s = 0; s < nstates; ++s)
{
- state1 = sp->number;
- for (i = sp->nshifts - 1; i >= 0; i--)
+ transitions *sp = states[s]->transitions;
+ int i;
+ for (i = sp->num - 1; i >= 0 && TRANSITION_IS_GOTO (sp, i); --i)
{
- state2 = sp->shifts[i];
- symbol = state_table[state2].accessing_symbol;
-
- if (ISTOKEN (symbol))
- break;
-
- k = temp_map[symbol]++;
- from_state[k] = state1;
- to_state[k] = state2;
+ goto_number k = temp_map[TRANSITION_SYMBOL (sp, i) - ntokens]++;
+ from_state[k] = s;
+ to_state[k] = sp->states[i]->number;
}
}
- XFREE (temp_map + ntokens);
+ free (temp_map);
}
| Map a state/symbol pair into its numeric representation. |
`----------------------------------------------------------*/
-static int
-map_goto (int state, int symbol)
+static goto_number
+map_goto (state_number s0, symbol_number sym)
{
- int high;
- int low;
- int middle;
- int s;
+ goto_number high;
+ goto_number low;
+ goto_number middle;
+ state_number s;
- low = goto_map[symbol];
- high = goto_map[symbol + 1] - 1;
+ low = goto_map[sym - ntokens];
+ high = goto_map[sym - ntokens + 1] - 1;
- while (low <= high)
+ for (;;)
{
+ if (high < low)
+ abort ();
middle = (low + high) / 2;
s = from_state[middle];
- if (s == state)
+ if (s == s0)
return middle;
- else if (s < state)
+ else if (s < s0)
low = middle + 1;
else
high = middle - 1;
}
-
- assert (0);
- /* NOTREACHED */
- return 0;
}
static void
initialize_F (void)
{
- int i;
- int j;
- int k;
- shifts *sp;
- short *edge;
- unsigned *rowp;
- short *rp;
- short **reads;
- int nedges;
- int stateno;
- int symbol;
- int nwords;
-
- nwords = ngotos * tokensetsize;
- F = XCALLOC (unsigned, nwords);
-
- reads = XCALLOC (short *, ngotos);
- edge = XCALLOC (short, ngotos + 1);
- nedges = 0;
-
- rowp = F;
- for (i = 0; i < ngotos; i++)
- {
- stateno = to_state[i];
- sp = state_table[stateno].shift_table;
-
- if (sp)
- {
- k = sp->nshifts;
+ goto_number **reads = xnmalloc (ngotos, sizeof *reads);
+ goto_number *edge = xnmalloc (ngotos + 1, sizeof *edge);
+ goto_number nedges = 0;
- for (j = 0; j < k; j++)
- {
- symbol = state_table[sp->shifts[j]].accessing_symbol;
- if (ISVAR (symbol))
- break;
- SETBIT (rowp, symbol);
- }
+ goto_number i;
- for (; j < k; j++)
- {
- symbol = state_table[sp->shifts[j]].accessing_symbol;
- if (nullable[symbol])
- edge[nedges++] = map_goto (stateno, symbol);
- }
+ F = bitsetv_create (ngotos, ntokens, BITSET_FIXED);
- if (nedges)
- {
- reads[i] = rp = XCALLOC (short, nedges + 1);
+ for (i = 0; i < ngotos; i++)
+ {
+ state_number stateno = to_state[i];
+ transitions *sp = states[stateno]->transitions;
- for (j = 0; j < nedges; j++)
- rp[j] = edge[j];
+ int j;
+ FOR_EACH_SHIFT (sp, j)
+ bitset_set (F[i], TRANSITION_SYMBOL (sp, j));
- rp[nedges] = -1;
- nedges = 0;
- }
+ for (; j < sp->num; j++)
+ {
+ symbol_number sym = TRANSITION_SYMBOL (sp, j);
+ if (nullable[sym - ntokens])
+ edge[nedges++] = map_goto (stateno, sym);
}
- rowp += tokensetsize;
+ if (nedges == 0)
+ reads[i] = NULL;
+ else
+ {
+ reads[i] = xnmalloc (nedges + 1, sizeof reads[i][0]);
+ memcpy (reads[i], edge, nedges * sizeof edge[0]);
+ reads[i][nedges] = END_NODE;
+ nedges = 0;
+ }
}
- digraph (reads);
+ relation_digraph (reads, ngotos, &F);
for (i = 0; i < ngotos; i++)
- {
- if (reads[i])
- XFREE (reads[i]);
- }
+ free (reads[i]);
- XFREE (reads);
- XFREE (edge);
+ free (reads);
+ free (edge);
}
static void
-add_lookback_edge (int stateno, int ruleno, int gotono)
+add_lookback_edge (state *s, rule *r, goto_number gotono)
{
- int i;
- int k;
- int found;
- shorts *sp;
-
- i = state_table[stateno].lookaheads;
- k = state_table[stateno + 1].lookaheads;
- found = 0;
- while (!found && i < k)
- {
- if (LAruleno[i] == ruleno)
- found = 1;
- else
- i++;
- }
-
- assert (found);
-
- sp = XCALLOC (shorts, 1);
- sp->next = lookback[i];
+ int ri = state_reduction_find (s, r);
+ goto_list *sp = xmalloc (sizeof *sp);
+ sp->next = lookback[(s->reductions->look_ahead_tokens - LA) + ri];
sp->value = gotono;
- lookback[i] = sp;
+ lookback[(s->reductions->look_ahead_tokens - LA) + ri] = sp;
}
-static short **
-transpose (short **R_arg, int n)
-{
- short **new_R;
- short **temp_R;
- short *nedges;
- short *sp;
- int i;
- int k;
-
- nedges = XCALLOC (short, n);
-
- for (i = 0; i < n; i++)
- {
- sp = R_arg[i];
- if (sp)
- {
- while (*sp >= 0)
- nedges[*sp++]++;
- }
- }
-
- new_R = XCALLOC (short *, n);
- temp_R = XCALLOC (short *, n);
-
- for (i = 0; i < n; i++)
- {
- k = nedges[i];
- if (k > 0)
- {
- sp = XCALLOC (short, k + 1);
- new_R[i] = sp;
- temp_R[i] = sp;
- sp[k] = -1;
- }
- }
-
- XFREE (nedges);
-
- for (i = 0; i < n; i++)
- {
- sp = R_arg[i];
- if (sp)
- {
- while (*sp >= 0)
- *temp_R[*sp++]++ = i;
- }
- }
-
- XFREE (temp_R);
-
- return new_R;
-}
-
static void
build_relations (void)
{
- int i;
- int j;
- int k;
- short *rulep;
- short *rp;
- shifts *sp;
- int length;
- int nedges;
- int done;
- int state1;
- int stateno;
- int symbol1;
- int symbol2;
- short *shortp;
- short *edge;
- short *states;
- short **new_includes;
-
- includes = XCALLOC (short *, ngotos);
- edge = XCALLOC (short, ngotos + 1);
- states = XCALLOC (short, maxrhs + 1);
+ goto_number *edge = xnmalloc (ngotos + 1, sizeof *edge);
+ state_number *states1 = xnmalloc (ritem_longest_rhs () + 1, sizeof *states1);
+ goto_number i;
+
+ includes = xnmalloc (ngotos, sizeof *includes);
for (i = 0; i < ngotos; i++)
{
- nedges = 0;
- state1 = from_state[i];
- symbol1 = state_table[to_state[i]].accessing_symbol;
+ int nedges = 0;
+ symbol_number symbol1 = states[to_state[i]]->accessing_symbol;
+ rule **rulep;
- for (rulep = derives[symbol1]; *rulep > 0; rulep++)
+ for (rulep = derives[symbol1 - ntokens]; *rulep; rulep++)
{
- length = 1;
- states[0] = state1;
- stateno = state1;
+ bool done;
+ int length = 1;
+ item_number *rp;
+ state *s = states[from_state[i]];
+ states1[0] = s->number;
- for (rp = ritem + rrhs[*rulep]; *rp > 0; rp++)
+ for (rp = (*rulep)->rhs; *rp >= 0; rp++)
{
- symbol2 = *rp;
- sp = state_table[stateno].shift_table;
- k = sp->nshifts;
-
- for (j = 0; j < k; j++)
- {
- stateno = sp->shifts[j];
- if (state_table[stateno].accessing_symbol == symbol2)
- break;
- }
-
- states[length++] = stateno;
+ s = transitions_to (s->transitions,
+ item_number_as_symbol_number (*rp));
+ states1[length++] = s->number;
}
- if (!state_table[stateno].consistent)
- add_lookback_edge (stateno, *rulep, i);
+ if (!s->consistent)
+ add_lookback_edge (s, *rulep, i);
length--;
- done = 0;
+ done = false;
while (!done)
{
- done = 1;
+ done = true;
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;
+ /* Downcasting from item_number to symbol_number. */
+ edge[nedges++] = map_goto (states1[--length],
+ item_number_as_symbol_number (*rp));
+ if (nullable[*rp - ntokens])
+ done = false;
}
}
}
- if (nedges)
+ if (nedges == 0)
+ includes[i] = NULL;
+ else
{
- includes[i] = shortp = XCALLOC (short, nedges + 1);
+ int j;
+ includes[i] = xnmalloc (nedges + 1, sizeof includes[i][0]);
for (j = 0; j < nedges; j++)
- shortp[j] = edge[j];
- shortp[nedges] = -1;
+ includes[i][j] = edge[j];
+ includes[i][nedges] = END_NODE;
}
}
- new_includes = transpose (includes, ngotos);
-
- for (i = 0; i < ngotos; i++)
- if (includes[i])
- XFREE (includes[i]);
-
- XFREE (includes);
+ free (edge);
+ free (states1);
- includes = new_includes;
-
- XFREE (edge);
- XFREE (states);
+ relation_transpose (&includes, ngotos);
}
static void
compute_FOLLOWS (void)
{
- int i;
+ goto_number i;
- digraph (includes);
+ relation_digraph (includes, ngotos, &F);
for (i = 0; i < ngotos; i++)
- {
- if (includes[i])
- XFREE (includes[i]);
- }
+ free (includes[i]);
- XFREE (includes);
+ free (includes);
}
static void
-compute_lookaheads (void)
+compute_look_ahead_tokens (void)
{
- int i;
- int n;
- unsigned *fp1;
- unsigned *fp2;
- unsigned *fp3;
- shorts *sp;
- unsigned *rowp;
- shorts *sptmp; /* JF */
-
- rowp = LA;
- for (i = 0; i < state_table[nstates].lookaheads; i++)
- {
- fp3 = rowp + tokensetsize;
- for (sp = lookback[i]; sp; sp = sp->next)
- {
- fp1 = rowp;
- fp2 = F + tokensetsize * sp->value;
- while (fp1 < fp3)
- *fp1++ |= *fp2++;
- }
+ size_t i;
+ goto_list *sp;
- rowp = fp3;
- }
+ for (i = 0; i < nLA; i++)
+ for (sp = lookback[i]; sp; sp = sp->next)
+ bitset_or (LA[i], LA[i], F[sp->value]);
+
+ /* Free LOOKBACK. */
+ for (i = 0; i < nLA; i++)
+ LIST_FREE (goto_list, lookback[i]);
+
+ free (lookback);
+ bitsetv_free (F);
+}
+
+
+/*-----------------------------------------------------.
+| Count the number of look-ahead tokens required for S |
+| (N_LOOK_AHEAD_TOKENS member). |
+`-----------------------------------------------------*/
+
+static int
+state_look_ahead_tokens_count (state *s)
+{
+ int k;
+ int n_look_ahead_tokens = 0;
+ reductions *rp = s->reductions;
+ transitions *sp = s->transitions;
+
+ /* We need a look-ahead either to distinguish different
+ reductions (i.e., there are two or more), or to distinguish a
+ reduction from a shift. Otherwise, it is straightforward,
+ and the state is `consistent'. */
+ if (rp->num > 1
+ || (rp->num == 1 && sp->num &&
+ !TRANSITION_IS_DISABLED (sp, 0) && TRANSITION_IS_SHIFT (sp, 0)))
+ n_look_ahead_tokens += rp->num;
+ else
+ s->consistent = 1;
+
+ for (k = 0; k < sp->num; k++)
+ if (!TRANSITION_IS_DISABLED (sp, k) && TRANSITION_IS_ERROR (sp, k))
+ {
+ s->consistent = 0;
+ break;
+ }
- for (i = 0; i < state_table[nstates].lookaheads; i++)
+ return n_look_ahead_tokens;
+}
+
+
+/*-----------------------------------------------------.
+| Compute LA, NLA, and the look_ahead_tokens members. |
+`-----------------------------------------------------*/
+
+static void
+initialize_LA (void)
+{
+ state_number i;
+ bitsetv pLA;
+
+ /* Compute the total number of reductions requiring a look-ahead. */
+ nLA = 0;
+ for (i = 0; i < nstates; i++)
+ nLA += state_look_ahead_tokens_count (states[i]);
+ /* Avoid having to special case 0. */
+ if (!nLA)
+ nLA = 1;
+
+ pLA = LA = bitsetv_create (nLA, ntokens, BITSET_FIXED);
+ lookback = xcalloc (nLA, sizeof *lookback);
+
+ /* Initialize the members LOOK_AHEAD_TOKENS for each state whose reductions
+ require look-ahead tokens. */
+ for (i = 0; i < nstates; i++)
{
- /* JF removed ref to freed storage */
- for (sp = lookback[i]; sp; sp = sptmp)
+ int count = state_look_ahead_tokens_count (states[i]);
+ if (count)
{
- sptmp = sp->next;
- XFREE (sp);
+ states[i]->reductions->look_ahead_tokens = pLA;
+ pLA += count;
}
}
-
- XFREE (lookback);
- XFREE (F);
}
+/*----------------------------------------------.
+| Output the look-ahead tokens for each state. |
+`----------------------------------------------*/
+
+static void
+look_ahead_tokens_print (FILE *out)
+{
+ state_number i;
+ int j, k;
+ fprintf (out, "Look-ahead tokens: BEGIN\n");
+ for (i = 0; i < nstates; ++i)
+ {
+ reductions *reds = states[i]->reductions;
+ bitset_iterator iter;
+ int n_look_ahead_tokens = 0;
+
+ if (reds->look_ahead_tokens)
+ for (k = 0; k < reds->num; ++k)
+ if (reds->look_ahead_tokens[k])
+ ++n_look_ahead_tokens;
+
+ fprintf (out, "State %d: %d look-ahead tokens\n",
+ i, n_look_ahead_tokens);
+
+ if (reds->look_ahead_tokens)
+ for (j = 0; j < reds->num; ++j)
+ BITSET_FOR_EACH (iter, reds->look_ahead_tokens[j], k, 0)
+ {
+ fprintf (out, " on %d (%s) -> rule %d\n",
+ k, symbols[k]->tag,
+ reds->rules[j]->number);
+ };
+ }
+ fprintf (out, "Look-ahead tokens: END\n");
+}
+
void
lalr (void)
{
- tokensetsize = WORDSIZE (ntokens);
-
- set_state_table ();
- set_maxrhs ();
initialize_LA ();
set_goto_map ();
initialize_F ();
build_relations ();
compute_FOLLOWS ();
- compute_lookaheads ();
+ compute_look_ahead_tokens ();
+
+ if (trace_flag & trace_sets)
+ look_ahead_tokens_print (stderr);
+}
+
+
+void
+lalr_free (void)
+{
+ state_number s;
+ for (s = 0; s < nstates; ++s)
+ states[s]->reductions->look_ahead_tokens = NULL;
+ bitsetv_free (LA);
}
projects / bison.git / blobdiff