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authormarha <marha@users.sourceforge.net>2010-11-19 15:19:19 +0000
committermarha <marha@users.sourceforge.net>2010-11-19 15:19:19 +0000
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tree8d5546283940c928290a23c50748b3f5c431ef06 /tools/bison++/closure.cc
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parent12f606ce06ef926f366a03079c5e3107c23f18af (diff)
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+/* Subroutines for bison
+ Copyright (C) 1984, 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. */
+
+
+/* subroutines of file LR0.c.
+
+Entry points:
+
+ closure (items, n)
+
+Given a vector of item numbers items, of length n,
+set up ruleset and itemset to indicate what rules could be run
+and which items could be accepted when those items are the active ones.
+
+ruleset contains a bit for each rule. closure sets the bits
+for all rules which could potentially describe the next input to be read.
+
+itemset is a vector of item numbers; itemsetend points to just beyond the end
+ of the part of it that is significant.
+closure places there the indices of all items which represent units of
+input that could arrive next.
+
+ initialize_closure (n)
+
+Allocates the itemset and ruleset vectors,
+and precomputes useful data so that closure can be called.
+n is the number of elements to allocate for itemset.
+
+ finalize_closure ()
+
+Frees itemset, ruleset and internal data.
+
+*/
+
+#include <stdio.h>
+#include "system.h"
+#include "machine.h"
+#include "new.h"
+#include "gram.h"
+
+#ifdef DEBUG
+static void print_fderives(void);
+static void print_firsts(void);
+static void print_closure(int n);
+#endif
+
+extern short **derives;
+extern char **tags;
+
+void set_fderives();
+void set_firsts();
+
+extern void RTC(unsigned* R, int n);
+
+short *itemset;
+short *itemsetend;
+static unsigned *ruleset;
+
+/* internal data. See comments before set_fderives and set_firsts. */
+static unsigned *fderives;
+static unsigned *firsts;
+
+/* number of words required to hold a bit for each rule */
+static int rulesetsize;
+
+/* number of words required to hold a bit for each variable */
+static int varsetsize;
+
+
+void
+initialize_closure(int n)
+{
+ itemset = NEW2(n, short);
+
+ rulesetsize = WORDSIZE(nrules + 1);
+ ruleset = NEW2(rulesetsize, unsigned);
+
+ set_fderives();
+}
+
+
+
+/* set fderives to an nvars 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. */
+void
+set_fderives()
+{
+ register unsigned *rrow;
+ register unsigned *vrow;
+ register int j;
+ register unsigned cword;
+ register short *rp;
+ register int b;
+
+ int ruleno;
+ int i;
+
+ fderives = NEW2(nvars * rulesetsize, unsigned) - ntokens * rulesetsize;
+
+ set_firsts();
+
+ rrow = fderives + ntokens * rulesetsize;
+
+ for (i = ntokens; i < nsyms; i++)
+ {
+ vrow = firsts + ((i - ntokens) * varsetsize);
+ cword = *vrow++;
+ b = 0;
+ for (j = ntokens; j < nsyms; j++)
+ {
+ if (cword & (1 << b))
+ {
+ rp = derives[j];
+ while ((ruleno = *rp++) > 0)
+ {
+ SETBIT(rrow, ruleno);
+ }
+ }
+
+ b++;
+ if (b >= BITS_PER_WORD && j + 1 < nsyms)
+ {
+ cword = *vrow++;
+ b = 0;
+ }
+ }
+
+ rrow += rulesetsize;
+ }
+
+#ifdef DEBUG
+ print_fderives();
+#endif
+
+ FREE(firsts);
+}
+
+
+
+/* set firsts to be an nvars by nvars bit matrix 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, 5 - ntokens] in firsts is set. */
+void
+set_firsts()
+{
+ register unsigned *row;
+/* register int done; JF unused */
+ register int symbol;
+ register short *sp;
+ register int rowsize;
+
+ int i;
+
+ varsetsize = rowsize = WORDSIZE(nvars);
+
+ firsts = NEW2(nvars * rowsize, unsigned);
+
+ row = firsts;
+ for (i = ntokens; i < nsyms; i++)
+ {
+ sp = derives[i];
+ while (*sp >= 0)
+ {
+ symbol = ritem[rrhs[*sp++]];
+ if (ISVAR(symbol))
+ {
+ symbol -= ntokens;
+ SETBIT(row, symbol);
+ }
+ }
+
+ row += rowsize;
+ }
+
+ RTC(firsts, nvars);
+
+#ifdef DEBUG
+ print_firsts();
+#endif
+}
+
+
+void
+closure(short* core, int n)
+{
+ register int ruleno;
+ register unsigned word;
+ register short *csp;
+ register unsigned *dsp;
+ register unsigned *rsp;
+
+ short *csend;
+ unsigned *rsend;
+ int symbol;
+ int itemno;
+
+ rsp = ruleset;
+ rsend = ruleset + rulesetsize;
+ csend = core + n;
+
+ if (n == 0)
+ {
+ dsp = fderives + start_symbol * rulesetsize;
+ while (rsp < rsend)
+ *rsp++ = *dsp++;
+ }
+ else
+ {
+ while (rsp < rsend)
+ *rsp++ = 0;
+
+ csp = core;
+ while (csp < csend)
+ {
+ symbol = ritem[*csp++];
+ if (ISVAR(symbol))
+ {
+ dsp = fderives + symbol * rulesetsize;
+ rsp = ruleset;
+ while (rsp < rsend)
+ *rsp++ |= *dsp++;
+ }
+ }
+ }
+
+ ruleno = 0;
+ itemsetend = itemset;
+ csp = core;
+ rsp = ruleset;
+ while (rsp < rsend)
+ {
+ word = *rsp++;
+ if (word == 0)
+ {
+ ruleno += BITS_PER_WORD;
+ }
+ else
+ {
+ register int b;
+
+ for (b = 0; b < BITS_PER_WORD; b++)
+ {
+ if (word & (1 << b))
+ {
+ itemno = rrhs[ruleno];
+ while (csp < csend && *csp < itemno)
+ *itemsetend++ = *csp++;
+ *itemsetend++ = itemno;
+ }
+
+ ruleno++;
+ }
+ }
+ }
+
+ while (csp < csend)
+ *itemsetend++ = *csp++;
+
+#ifdef DEBUG
+ print_closure(n);
+#endif
+}
+
+
+void
+finalize_closure()
+{
+ FREE(itemset);
+ FREE(ruleset);
+ FREE(fderives + ntokens * rulesetsize);
+}
+
+
+
+#ifdef DEBUG
+
+void print_closure(int n)
+{
+ register short *isp;
+
+ printf("\n\nn = %d\n\n", n);
+ for (isp = itemset; isp < itemsetend; isp++)
+ printf(" %d\n", *isp);
+}
+
+
+
+void print_firsts(void)
+{
+ register int i;
+ register int j;
+ register unsigned *rowp;
+
+ printf("\n\n\nFIRSTS\n\n");
+
+ for (i = ntokens; i < nsyms; i++)
+ {
+ printf("\n\n%s firsts\n\n", tags[i]);
+
+ rowp = firsts + ((i - ntokens) * varsetsize);
+
+ for (j = 0; j < nvars; j++)
+ if (BITISSET (rowp, j))
+ printf(" %s\n", tags[j + ntokens]);
+ }
+}
+
+
+
+void print_fderives(void)
+{
+ register int i;
+ register int j;
+ register unsigned *rp;
+
+ printf("\n\n\nFDERIVES\n");
+
+ for (i = ntokens; i < nsyms; i++)
+ {
+ printf("\n\n%s derives\n\n", tags[i]);
+ rp = fderives + i * rulesetsize;
+
+ for (j = 0; j <= nrules; j++)
+ if (BITISSET (rp, j))
+ printf(" %d\n", j);
+ }
+
+ fflush(stdout);
+}
+
+#endif