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* src/reduce.h: New file.
Propagate its inclusion. * src/reduce.c: Topological sort and other formatting changes. (bool, TRUE, FALSE): Move their definition to... * src/system.h: here.
This commit is contained in:
Akim Demaille
@@ -1,3 +1,12 @@
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2000-10-02 Akim Demaille <akim@epita.fr>
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* src/reduce.h: New file.
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Propagate its inclusion.
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* src/reduce.c: Topological sort and other formatting changes.
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(bool, TRUE, FALSE): Move their definition to...
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* src/system.h: here.
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2000-10-02 Akim Demaille <akim@epita.fr>
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* src/files.c: Formatting changes.
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@@ -22,7 +22,7 @@ noinst_HEADERS = alloc.h closure.h complain.h \
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derives.h \
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files.h getargs.h gram.h lalr.h lex.h \
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output.h state.h \
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reader.h symtab.h system.h types.h
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reader.h reduce.h symtab.h system.h types.h
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data_DATA = bison.simple bison.hairy
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@@ -28,6 +28,7 @@
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#include "output.h"
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#include "reader.h"
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#include "lalr.h"
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#include "reduce.h"
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#if 0 /* XXX currently unused. */
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/* Nonzero means failure has been detected; don't write a parser file. */
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@@ -41,7 +42,6 @@ extern void berror PARAMS((const char *));
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extern char *printable_version PARAMS ((int));
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extern void reduce_grammar PARAMS ((void));
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extern void set_nullable PARAMS ((void));
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extern void free_nullable PARAMS ((void));
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extern void generate_states PARAMS ((void));
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314
src/reduce.c
314
src/reduce.c
@@ -1,5 +1,5 @@
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/* Grammar reduction for Bison.
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Copyright (C) 1988, 1989 Free Software Foundation, Inc.
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Copyright (C) 1988, 1989, 2000 Free Software Foundation, Inc.
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This file is part of Bison, the GNU Compiler Compiler.
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@@ -19,15 +19,11 @@ the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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/*
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* Reduce the grammar: Find and eliminate unreachable terminals,
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* nonterminals, and productions. David S. Bakin.
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*/
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/* Reduce the grammar: Find and eliminate unreachable terminals,
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nonterminals, and productions. David S. Bakin. */
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/*
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* Don't eliminate unreachable terminals: They may be used by the user's
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* parser.
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*/
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/* Don't eliminate unreachable terminals: They may be used by the
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user's parser. */
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#include "system.h"
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#include "getargs.h"
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@@ -35,49 +31,27 @@ Boston, MA 02111-1307, USA. */
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#include "gram.h"
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#include "alloc.h"
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#include "complain.h"
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#include "reduce.h"
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extern char **tags; /* reader.c */
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static int statisticsflag; /* XXXXXXX */
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extern int fixed_outfiles;
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#ifndef TRUE
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#define TRUE (1)
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#define FALSE (0)
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#endif
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typedef int bool;
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typedef unsigned *BSet;
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typedef short *rule;
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/*
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* N is set of all nonterminals which are not useless. P is set of all rules
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* which have no useless nonterminals in their RHS. V is the set of all
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* accessible symbols.
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*/
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/* N is set of all nonterminals which are not useless. P is set of
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all rules which have no useless nonterminals in their RHS. V is
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the set of all accessible symbols. */
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static BSet N, P, V, V1;
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static int nuseful_productions, nuseless_productions,
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nuseful_nonterminals, nuseless_nonterminals;
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extern void reduce_grammar PARAMS((void));
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static bool bits_equal PARAMS((BSet, BSet, int));
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static int nbits PARAMS((unsigned));
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static int bits_size PARAMS((BSet, int));
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static void useless_nonterminals PARAMS((void));
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static void inaccessable_symbols PARAMS((void));
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static void reduce_grammar_tables PARAMS((void));
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static void print_results PARAMS((void));
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static void print_notices PARAMS((void));
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#if 0 /* XXX currently unused. */
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static void dump_grammar PARAMS((void));
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#endif
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static int nuseful_productions;
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static int nuseless_productions;
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static int nuseful_nonterminals;
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static int nuseless_nonterminals;
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static bool
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bits_equal (BSet L, BSet R, int n)
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{
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@@ -95,7 +69,8 @@ nbits (unsigned i)
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{
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int count = 0;
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while (i != 0) {
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while (i != 0)
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{
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i ^= (i & ((unsigned) (-(int) i)));
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++count;
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}
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@@ -113,67 +88,11 @@ bits_size (BSet S, int n)
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return count;
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}
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void
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reduce_grammar (void)
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{
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bool reduced;
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/* Allocate the global sets used to compute the reduced grammar */
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N = NEW2(WORDSIZE(nvars), unsigned);
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P = NEW2(WORDSIZE(nrules + 1), unsigned);
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V = NEW2(WORDSIZE(nsyms), unsigned);
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V1 = NEW2(WORDSIZE(nsyms), unsigned);
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useless_nonterminals();
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inaccessable_symbols();
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reduced = (bool) (nuseless_nonterminals + nuseless_productions > 0);
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if (verboseflag)
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print_results();
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if (reduced == FALSE)
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goto done_reducing;
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print_notices();
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if (!BITISSET(N, start_symbol - ntokens))
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fatal (_("Start symbol %s does not derive any sentence"),
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tags[start_symbol]);
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reduce_grammar_tables();
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#if 0
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if (verboseflag)
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{
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fprintf(foutput, "REDUCED GRAMMAR\n\n");
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dump_grammar();
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}
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#endif
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/**/ statisticsflag = FALSE; /* someday getopts should handle this */
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if (statisticsflag == TRUE)
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fprintf(stderr,
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_("reduced %s defines %d terminal%s, %d nonterminal%s\
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, and %d production%s.\n"), infile,
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ntokens, (ntokens == 1 ? "" : "s"),
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nvars, (nvars == 1 ? "" : "s"),
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nrules, (nrules == 1 ? "" : "s"));
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done_reducing:
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/* Free the global sets used to compute the reduced grammar */
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FREE(N);
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FREE(V);
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FREE(P);
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}
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/*
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* Another way to do this would be with a set for each production and then do
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* subset tests against N0, but even for the C grammar the whole reducing
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* process takes only 2 seconds on my 8Mhz AT.
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*/
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/*-------------------------------------------------------------------.
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| Another way to do this would be with a set for each production and |
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| then do subset tests against N0, but even for the C grammar the |
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| whole reducing process takes only 2 seconds on my 8Mhz AT. |
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`-------------------------------------------------------------------*/
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static bool
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useful_production (int i, BSet N0)
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@@ -181,10 +100,8 @@ useful_production (int i, BSet N0)
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rule r;
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short n;
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/*
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* A production is useful if all of the nonterminals in its RHS
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* appear in the set of useful nonterminals.
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*/
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/* A production is useful if all of the nonterminals in its appear
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in the set of useful nonterminals. */
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for (r = &ritem[rrhs[i]]; *r > 0; r++)
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if (ISVAR (n = *r))
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@@ -194,7 +111,9 @@ useful_production (int i, BSet N0)
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}
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/* Remember that rules are 1-origin, symbols are 0-origin. */
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/*---------------------------------------------------------.
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| Remember that rules are 1-origin, symbols are 0-origin. |
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`---------------------------------------------------------*/
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static void
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useless_nonterminals (void)
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@@ -202,30 +121,26 @@ useless_nonterminals (void)
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BSet Np, Ns;
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int i, n;
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/*
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* N is set as built. Np is set being built this iteration. P is set
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* of all productions which have a RHS all in N.
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*/
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/* N is set as built. Np is set being built this iteration. P is
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set of all productions which have a RHS all in N. */
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Np = NEW2 (WORDSIZE (nvars), unsigned);
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/*
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* The set being computed is a set of nonterminals which can derive
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* the empty string or strings consisting of all terminals. At each
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* iteration a nonterminal is added to the set if there is a
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* production with that nonterminal as its LHS for which all the
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* nonterminals in its RHS are already in the set. Iterate until the
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* set being computed remains unchanged. Any nonterminals not in the
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* set at that point are useless in that they will never be used in
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* deriving a sentence of the language.
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*
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* This iteration doesn't use any special traversal over the
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* productions. A set is kept of all productions for which all the
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* nonterminals in the RHS are in useful. Only productions not in
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* this set are scanned on each iteration. At the end, this set is
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* saved to be used when finding useful productions: only productions
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* in this set will appear in the final grammar.
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*/
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/* The set being computed is a set of nonterminals which can derive
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the empty string or strings consisting of all terminals. At each
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iteration a nonterminal is added to the set if there is a
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production with that nonterminal as its LHS for which all the
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nonterminals in its RHS are already in the set. Iterate until
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the set being computed remains unchanged. Any nonterminals not
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in the set at that point are useless in that they will never be
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used in deriving a sentence of the language.
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This iteration doesn't use any special traversal over the
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productions. A set is kept of all productions for which all the
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nonterminals in the RHS are in useful. Only productions not in
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this set are scanned on each iteration. At the end, this set is
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saved to be used when finding useful productions: only
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productions in this set will appear in the final grammar. */
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n = 0;
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while (1)
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@@ -252,7 +167,8 @@ useless_nonterminals (void)
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FREE (N);
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N = Np;
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}
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static void
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inaccessable_symbols (void)
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{
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@@ -261,30 +177,28 @@ inaccessable_symbols (void)
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short t;
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rule r;
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/*
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* Find out which productions are reachable and which symbols are
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* used. Starting with an empty set of productions and a set of
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* symbols which only has the start symbol in it, iterate over all
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* productions until the set of productions remains unchanged for an
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* iteration. For each production which has a LHS in the set of
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* reachable symbols, add the production to the set of reachable
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* productions, and add all of the nonterminals in the RHS of the
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* production to the set of reachable symbols.
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*
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* Consider only the (partially) reduced grammar which has only
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* nonterminals in N and productions in P.
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*
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* The result is the set P of productions in the reduced grammar, and
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* the set V of symbols in the reduced grammar.
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*
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* Although this algorithm also computes the set of terminals which are
|
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* reachable, no terminal will be deleted from the grammar. Some
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* terminals might not be in the grammar but might be generated by
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* semantic routines, and so the user might want them available with
|
||||
* specified numbers. (Is this true?) However, the nonreachable
|
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* terminals are printed (if running in verbose mode) so that the user
|
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* can know.
|
||||
*/
|
||||
/* Find out which productions are reachable and which symbols are
|
||||
used. Starting with an empty set of productions and a set of
|
||||
symbols which only has the start symbol in it, iterate over all
|
||||
productions until the set of productions remains unchanged for an
|
||||
iteration. For each production which has a LHS in the set of
|
||||
reachable symbols, add the production to the set of reachable
|
||||
productions, and add all of the nonterminals in the RHS of the
|
||||
production to the set of reachable symbols.
|
||||
|
||||
Consider only the (partially) reduced grammar which has only
|
||||
nonterminals in N and productions in P.
|
||||
|
||||
The result is the set P of productions in the reduced grammar,
|
||||
and the set V of symbols in the reduced grammar.
|
||||
|
||||
Although this algorithm also computes the set of terminals which
|
||||
are reachable, no terminal will be deleted from the grammar. Some
|
||||
terminals might not be in the grammar but might be generated by
|
||||
semantic routines, and so the user might want them available with
|
||||
specified numbers. (Is this true?) However, the nonreachable
|
||||
terminals are printed (if running in verbose mode) so that the
|
||||
user can know. */
|
||||
|
||||
Vp = NEW2 (WORDSIZE (nsyms), unsigned);
|
||||
Pp = NEW2 (WORDSIZE (nrules + 1), unsigned);
|
||||
@@ -302,13 +216,11 @@ inaccessable_symbols (void)
|
||||
Vp[i] = V[i];
|
||||
for (i = 1; i <= nrules; i++)
|
||||
{
|
||||
if (!BITISSET(Pp, i) && BITISSET(P, i) &&
|
||||
BITISSET(V, rlhs[i]))
|
||||
if (!BITISSET (Pp, i) && BITISSET (P, i) && BITISSET (V, rlhs[i]))
|
||||
{
|
||||
for (r = &ritem[rrhs[i]]; *r >= 0; r++)
|
||||
{
|
||||
if (ISTOKEN(t = *r)
|
||||
|| BITISSET(N, t - ntokens))
|
||||
if (ISTOKEN (t = *r) || BITISSET (N, t - ntokens))
|
||||
{
|
||||
SETBIT (Vp, t);
|
||||
}
|
||||
@@ -351,7 +263,7 @@ inaccessable_symbols (void)
|
||||
if (rprecsym[i] != 0)
|
||||
SETBIT (V1, rprecsym[i]);
|
||||
}
|
||||
|
||||
|
||||
static void
|
||||
reduce_grammar_tables (void)
|
||||
{
|
||||
@@ -385,7 +297,9 @@ reduce_grammar_tables (void)
|
||||
ritem[ni++] = ritem[pi++];
|
||||
ritem[ni++] = -np;
|
||||
}
|
||||
} else {
|
||||
}
|
||||
else
|
||||
{
|
||||
while (ritem[ni++] >= 0);
|
||||
}
|
||||
}
|
||||
@@ -394,10 +308,8 @@ reduce_grammar_tables (void)
|
||||
nrules -= nuseless_productions;
|
||||
nitems = ni;
|
||||
|
||||
/*
|
||||
* Is it worth it to reduce the amount of memory for the
|
||||
* grammar? Probably not.
|
||||
*/
|
||||
/* Is it worth it to reduce the amount of memory for the
|
||||
grammar? Probably not. */
|
||||
|
||||
}
|
||||
#endif /* 0 */
|
||||
@@ -426,11 +338,9 @@ reduce_grammar_tables (void)
|
||||
short *nontermmap;
|
||||
rule r;
|
||||
|
||||
/*
|
||||
* create a map of nonterminal number to new nonterminal
|
||||
* number. -1 in the map means it was useless and is being
|
||||
* eliminated.
|
||||
*/
|
||||
/* Create a map of nonterminal number to new nonterminal
|
||||
number. -1 in the map means it was useless and is being
|
||||
eliminated. */
|
||||
|
||||
nontermmap = NEW2 (nvars, short) - ntokens;
|
||||
for (i = ntokens; i < nsyms; i++)
|
||||
@@ -451,7 +361,9 @@ reduce_grammar_tables (void)
|
||||
sassoc[n] = sassoc[i];
|
||||
sprec[n] = sprec[i];
|
||||
tags[n] = tags[i];
|
||||
} else {
|
||||
}
|
||||
else
|
||||
{
|
||||
free (tags[i]);
|
||||
}
|
||||
}
|
||||
@@ -480,7 +392,7 @@ reduce_grammar_tables (void)
|
||||
free (&nontermmap[ntokens]);
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
static void
|
||||
print_results (void)
|
||||
{
|
||||
@@ -544,8 +456,7 @@ dump_grammar (void)
|
||||
fprintf (foutput, _("Variables\n---------\n\n"));
|
||||
fprintf (foutput, _("Value Sprec Sassoc Tag\n"));
|
||||
for (i = ntokens; i < nsyms; i++)
|
||||
fprintf(foutput, "%5d %5d %5d %s\n",
|
||||
i, sprec[i], sassoc[i], tags[i]);
|
||||
fprintf (foutput, "%5d %5d %5d %s\n", i, sprec[i], sassoc[i], tags[i]);
|
||||
fprintf (foutput, "\n\n");
|
||||
fprintf (foutput, _("Rules\n-----\n\n"));
|
||||
for (i = 1; i <= nrules; i++)
|
||||
@@ -567,6 +478,7 @@ dump_grammar (void)
|
||||
}
|
||||
fprintf (foutput, "\n\n");
|
||||
}
|
||||
|
||||
#endif
|
||||
|
||||
|
||||
@@ -590,9 +502,65 @@ print_notices (void)
|
||||
if (nuseless_productions > 0)
|
||||
{
|
||||
fprintf (stderr, _("%d useless rule%s"),
|
||||
nuseless_productions,
|
||||
(nuseless_productions == 1 ? "" : "s"));
|
||||
nuseless_productions, (nuseless_productions == 1 ? "" : "s"));
|
||||
}
|
||||
fprintf (stderr, "\n");
|
||||
fflush (stderr);
|
||||
}
|
||||
|
||||
void
|
||||
reduce_grammar (void)
|
||||
{
|
||||
bool reduced;
|
||||
|
||||
/* Allocate the global sets used to compute the reduced grammar */
|
||||
|
||||
N = NEW2 (WORDSIZE (nvars), unsigned);
|
||||
P = NEW2 (WORDSIZE (nrules + 1), unsigned);
|
||||
V = NEW2 (WORDSIZE (nsyms), unsigned);
|
||||
V1 = NEW2 (WORDSIZE (nsyms), unsigned);
|
||||
|
||||
useless_nonterminals ();
|
||||
inaccessable_symbols ();
|
||||
|
||||
reduced = (bool) (nuseless_nonterminals + nuseless_productions > 0);
|
||||
|
||||
if (verboseflag)
|
||||
print_results ();
|
||||
|
||||
if (reduced == FALSE)
|
||||
goto done_reducing;
|
||||
|
||||
print_notices ();
|
||||
|
||||
if (!BITISSET (N, start_symbol - ntokens))
|
||||
fatal (_("Start symbol %s does not derive any sentence"),
|
||||
tags[start_symbol]);
|
||||
|
||||
reduce_grammar_tables ();
|
||||
#if 0
|
||||
if (verboseflag)
|
||||
{
|
||||
fprintf (foutput, "REDUCED GRAMMAR\n\n");
|
||||
dump_grammar ();
|
||||
}
|
||||
#endif
|
||||
statisticsflag = FALSE; /* someday getopts should handle this */
|
||||
if (statisticsflag == TRUE)
|
||||
fprintf (stderr, _("reduced %s defines %d terminal%s, %d nonterminal%s\
|
||||
, and %d production%s.\n"),
|
||||
infile,
|
||||
ntokens,
|
||||
(ntokens == 1 ? "" : "s"),
|
||||
nvars,
|
||||
(nvars == 1 ? "" : "s"),
|
||||
nrules,
|
||||
(nrules == 1 ? "" : "s"));
|
||||
|
||||
done_reducing:
|
||||
/* Free the global sets used to compute the reduced grammar */
|
||||
|
||||
FREE (N);
|
||||
FREE (V);
|
||||
FREE (P);
|
||||
}
|
||||
|
||||
11
src/system.h
11
src/system.h
@@ -148,3 +148,14 @@ extern int errno;
|
||||
#define SETBIT(x, i) ((x)[(i)/BITS_PER_WORD] |= (1<<((i) % BITS_PER_WORD)))
|
||||
#define RESETBIT(x, i) ((x)[(i)/BITS_PER_WORD] &= ~(1<<((i) % BITS_PER_WORD)))
|
||||
#define BITISSET(x, i) (((x)[(i)/BITS_PER_WORD] & (1<<((i) % BITS_PER_WORD))) != 0)
|
||||
|
||||
|
||||
/*-----------.
|
||||
| Booleans. |
|
||||
`-----------*/
|
||||
|
||||
#ifndef TRUE
|
||||
# define TRUE (1)
|
||||
# define FALSE (0)
|
||||
#endif
|
||||
typedef int bool;
|
||||
|
||||
Reference in New Issue
Block a user