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/* Closures for Bison
Copyright (C) 1984, 1989, 2000-2002, 2004-2005, 2007, 2009-2015,
2018-2021 Free Software Foundation, Inc.
This file is part of Bison, the GNU Compiler Compiler.
This program 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 3 of the License, or
(at your option) any later version.
This program 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 this program. If not, see <https://www.gnu.org/licenses/>. */
#include <config.h>
#include "system.h"
#include <bitset.h>
#include <bitsetv.h>
#include "closure.h"
#include "derives.h"
#include "getargs.h"
#include "gram.h"
#include "reader.h"
#include "symtab.h"
/* NITEMSET is the size of the array ITEMSET. */
item_index *itemset;
size_t nitemset;
/* RULESET contains a bit for each rule. CLOSURE sets the bits for
all rules which could potentially describe the next input to be
read. */
static bitset ruleset;
/* internal data. See comments before set_fderives and set_firsts. */
static bitsetv fderives = NULL;
static bitsetv firsts = NULL;
/* Retrieve the FDERIVES/FIRSTS sets of the nonterminals numbered Var. */
#define FDERIVES(Var) fderives[(Var) - ntokens]
#define FIRSTS(Var) firsts[(Var) - ntokens]
/*-----------------.
| Debugging code. |
`-----------------*/
static void
closure_print (char const *title, item_index const *array, size_t size)
{
fprintf (stderr, "Closure: %s\n", title);
for (size_t i = 0; i < size; ++i)
{
fprintf (stderr, " %2d: .", array[i]);
item_number *rp;
for (rp = &ritem[array[i]]; 0 <= *rp; ++rp)
fprintf (stderr, " %s", symbols[*rp]->tag);
fprintf (stderr, " (rule %d)\n", item_number_as_rule_number (*rp));
}
fputs ("\n\n", stderr);
}
static void
print_firsts (void)
{
fprintf (stderr, "FIRSTS\n");
for (symbol_number i = ntokens; i < nsyms; ++i)
{
fprintf (stderr, " %s firsts\n", symbols[i]->tag);
bitset_iterator iter;
symbol_number j;
BITSET_FOR_EACH (iter, FIRSTS (i), j, 0)
fprintf (stderr, " %s\n", symbols[j + ntokens]->tag);
}
fprintf (stderr, "\n\n");
}
static void
print_fderives (void)
{
fprintf (stderr, "FDERIVES\n");
for (symbol_number i = ntokens; i < nsyms; ++i)
{
fprintf (stderr, " %s derives\n", symbols[i]->tag);
bitset_iterator iter;
rule_number r;
BITSET_FOR_EACH (iter, FDERIVES (i), r, 0)
{
fprintf (stderr, " %3d ", r);
rule_rhs_print (&rules[r], stderr);
fprintf (stderr, "\n");
}
}
fprintf (stderr, "\n\n");
}
/*-------------------------------------------------------------------.
| Set FIRSTS to be an NNTERMS array of NNTERMS bitsets indicating |
| which items can represent the beginning of the input corresponding |
| to which other items. |
| |
| For example, if some rule expands symbol 5 into the sequence of |
| symbols 8 3 20, the symbol 8 can be the beginning of the data for |
| symbol 5, so the bit [8 - ntokens] in first[5 - ntokens] (= FIRST |
| (5)) is set. |
`-------------------------------------------------------------------*/
static void
set_firsts (void)
{
firsts = bitsetv_create (nnterms, nnterms, BITSET_FIXED);
for (symbol_number i = ntokens; i < nsyms; ++i)
for (symbol_number j = 0; derives[i - ntokens][j]; ++j)
{
item_number sym = derives[i - ntokens][j]->rhs[0];
if (ISVAR (sym))
bitset_set (FIRSTS (i), sym - ntokens);
}
if (trace_flag & trace_sets)
bitsetv_matrix_dump (stderr, "RTC: Firsts Input", firsts);
bitsetv_reflexive_transitive_closure (firsts);
if (trace_flag & trace_sets)
bitsetv_matrix_dump (stderr, "RTC: Firsts Output", firsts);
if (trace_flag & trace_sets)
print_firsts ();
}
/*-------------------------------------------------------------------.
| Set FDERIVES to an NNTERMS by NRULES matrix of bits indicating |
| which rules can help derive the beginning of the data for each |
| nonterminal. |
| |
| For example, if symbol 5 can be derived as the sequence of symbols |
| 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
| the [5 - NTOKENS, 4] bit in FDERIVES is set. |
`-------------------------------------------------------------------*/
static void
set_fderives (void)
{
fderives = bitsetv_create (nnterms, nrules, BITSET_FIXED);
set_firsts ();
for (symbol_number i = ntokens; i < nsyms; ++i)
for (symbol_number j = ntokens; j < nsyms; ++j)
if (bitset_test (FIRSTS (i), j - ntokens))
for (rule_number k = 0; derives[j - ntokens][k]; ++k)
bitset_set (FDERIVES (i), derives[j - ntokens][k]->number);
if (trace_flag & trace_sets)
print_fderives ();
bitsetv_free (firsts);
}
void
closure_new (int n)
{
itemset = xnmalloc (n, sizeof *itemset);
ruleset = bitset_create (nrules, BITSET_FIXED);
set_fderives ();
}
void
closure (item_index const *core, size_t n)
{
if (trace_flag & trace_closure)
closure_print ("input", core, n);
bitset_zero (ruleset);
for (size_t c = 0; c < n; ++c)
if (ISVAR (ritem[core[c]]))
bitset_or (ruleset, ruleset, FDERIVES (ritem[core[c]]));
/* core is sorted on item index in ritem, which is sorted on rule number.
Compute itemset with the same sort. */
nitemset = 0;
size_t c = 0;
/* A bit index over RULESET. */
rule_number ruleno;
bitset_iterator iter;
BITSET_FOR_EACH (iter, ruleset, ruleno, 0)
{
item_index itemno = rules[ruleno].rhs - ritem;
while (c < n && core[c] < itemno)
{
itemset[nitemset] = core[c];
nitemset++;
c++;
}
itemset[nitemset] = itemno;
nitemset++;
};
while (c < n)
{
itemset[nitemset] = core[c];
nitemset++;
c++;
}
if (trace_flag & trace_closure)
closure_print ("output", itemset, nitemset);
}
void
closure_free (void)
{
free (itemset);
bitset_free (ruleset);
bitsetv_free (fderives);
}
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