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/* Parser accelerator module */
/* The parser as originally conceived had disappointing performance.
This module does some precomputation that speeds up the selection
of a DFA based upon a token, turning a search through an array
into a simple indexing operation. The parser now cannot work
without the accelerators installed. Note that the accelerators
are installed dynamically when the parser is initialized, they
are not part of the static data structure written on graminit.[ch]
by the parser generator. */
#include "pgenheaders.h"
#include "grammar.h"
#include "token.h"
#include "parser.h"
/* Forward references */
static void fixdfa PROTO((grammar *, dfa *));
static void fixstate PROTO((grammar *, dfa *, state *));
void
addaccelerators(g)
grammar *g;
{
dfa *d;
int i;
#ifdef DEBUG
printf("Adding parser accellerators ...\n");
#endif
d = g->g_dfa;
for (i = g->g_ndfas; --i >= 0; d++)
fixdfa(g, d);
g->g_accel = 1;
#ifdef DEBUG
printf("Done.\n");
#endif
}
static void
fixdfa(g, d)
grammar *g;
dfa *d;
{
state *s;
int j;
s = d->d_state;
for (j = 0; j < d->d_nstates; j++, s++)
fixstate(g, d, s);
}
static void
fixstate(g, d, s)
grammar *g;
dfa *d;
state *s;
{
arc *a;
int k;
int *accel;
int nl = g->g_ll.ll_nlabels;
s->s_accept = 0;
accel = NEW(int, nl);
for (k = 0; k < nl; k++)
accel[k] = -1;
a = s->s_arc;
for (k = s->s_narcs; --k >= 0; a++) {
int lbl = a->a_lbl;
label *l = &g->g_ll.ll_label[lbl];
int type = l->lb_type;
if (a->a_arrow >= (1 << 7)) {
printf("XXX too many states!\n");
continue;
}
if (ISNONTERMINAL(type)) {
dfa *d1 = finddfa(g, type);
int ibit;
if (type - NT_OFFSET >= (1 << 7)) {
printf("XXX too high nonterminal number!\n");
continue;
}
for (ibit = 0; ibit < g->g_ll.ll_nlabels; ibit++) {
if (testbit(d1->d_first, ibit)) {
if (accel[ibit] != -1)
printf("XXX ambiguity!\n");
accel[ibit] = a->a_arrow | (1 << 7) |
((type - NT_OFFSET) << 8);
}
}
}
else if (lbl == EMPTY)
s->s_accept = 1;
else if (lbl >= 0 && lbl < nl)
accel[lbl] = a->a_arrow;
}
while (nl > 0 && accel[nl-1] == -1)
nl--;
for (k = 0; k < nl && accel[k] == -1;)
k++;
if (k < nl) {
int i;
s->s_accel = NEW(int, nl-k);
if (s->s_accel == NULL) {
fprintf(stderr, "no mem to add parser accelerators\n");
exit(1);
}
s->s_lower = k;
s->s_upper = nl;
for (i = 0; k < nl; i++, k++)
s->s_accel[i] = accel[k];
}
DEL(accel);
}
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