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Instead of mapping the LHS of unused rules to -1, keep the LHS

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valid, but flag the rules as invalid.
* src/gram.h (rule_t): `useful' is a new member.
* src/print.c (print_grammar): Adjust.
* src/derives.c (set_derives): Likewise.
* src/reader.c (packgram, reduce_output): Likewise.
* src/reduce.c (reduce_grammar_tables): Likewise.
* tests/reduce.at (Underivable Rules, Useless Rules): New.
This commit is contained in:
Akim Demaille
2001-11-30 10:46:08 +00:00
parent d287d66a69
commit d39a6b7ca9
7 changed files with 131 additions and 30 deletions
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26
src/reduce.c
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@@ -310,20 +310,12 @@ reduce_grammar_tables (void)
}
#endif /* 0 */
/* Disable useless productions,
since they may contain useless nonterms
that would get mapped below to -1 and confuse everyone. */
/* Disable useless productions. */
if (nuseless_productions > 0)
{
int pn;
for (pn = 1; pn <= nrules; pn++)
{
if (!BITISSET (P, pn))
{
rule_table[pn].lhs = -1;
}
}
rule_table[pn].useful = BITISSET (P, pn);
}
}
@@ -338,8 +330,8 @@ nonterminals_reduce (void)
int i, n;
rule r;
/* Create a map of nonterminal number to new nonterminal number. -1
in the map means it was useless and is being eliminated. */
/* Map the nonterminals to their new index: useful first, useless
afterwards. Kept for later report. */
short *nontermmap = XCALLOC (short, nvars) - ntokens;
n = ntokens;
@@ -379,9 +371,7 @@ nonterminals_reduce (void)
for (i = 1; i <= nrules; i++)
{
/* Ignore the rules disabled above. */
if (rule_table[i].lhs >= 0)
rule_table[i].lhs = nontermmap[rule_table[i].lhs];
rule_table[i].lhs = nontermmap[rule_table[i].lhs];
if (ISVAR (rule_table[i].precsym))
/* Can this happen? */
rule_table[i].precsym = nontermmap[rule_table[i].precsym];
@@ -396,7 +386,7 @@ nonterminals_reduce (void)
nsyms -= nuseless_nonterminals;
nvars -= nuseless_nonterminals;
free (&nontermmap[ntokens]);
free (nontermmap + ntokens);
}
@@ -436,11 +426,11 @@ reduce_output (FILE *out)
int i;
fprintf (out, "%s\n\n", _("Useless rules:"));
for (i = 1; i <= nrules; i++)
if (!BITISSET (P, i))
if (!rule_table[i].useful)
{
rule r;
fprintf (out, "#%-4d ", i);
fprintf (out, "%s :\t", tags[rule_table[i].lhs]);
fprintf (out, "%s:", tags[rule_table[i].lhs]);
for (r = &ritem[rule_table[i].rhs]; *r >= 0; r++)
fprintf (out, " %s", tags[*r]);
fputs (";\n", out);