Staging
v0.8.1
v0.8.1
https://github.com/python/cpython
Tip revision: f03c5148cfc6873df855bd0edca2940f9a5d8fd5 authored by Ned Deily on 14 March 2018, 01:21:36 UTC
3.6.5rc1
3.6.5rc1
Tip revision: f03c514
acceler.c
/* 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 "node.h"
#include "token.h"
#include "parser.h"
/* Forward references */
static void fixdfa(grammar *, dfa *);
static void fixstate(grammar *, state *);
void
PyGrammar_AddAccelerators(grammar *g)
{
dfa *d;
int i;
d = g->g_dfa;
for (i = g->g_ndfas; --i >= 0; d++)
fixdfa(g, d);
g->g_accel = 1;
}
void
PyGrammar_RemoveAccelerators(grammar *g)
{
dfa *d;
int i;
g->g_accel = 0;
d = g->g_dfa;
for (i = g->g_ndfas; --i >= 0; d++) {
state *s;
int j;
s = d->d_state;
for (j = 0; j < d->d_nstates; j++, s++) {
if (s->s_accel)
PyObject_FREE(s->s_accel);
s->s_accel = NULL;
}
}
}
static void
fixdfa(grammar *g, dfa *d)
{
state *s;
int j;
s = d->d_state;
for (j = 0; j < d->d_nstates; j++, s++)
fixstate(g, s);
}
static void
fixstate(grammar *g, state *s)
{
arc *a;
int k;
int *accel;
int nl = g->g_ll.ll_nlabels;
s->s_accept = 0;
accel = (int *) PyObject_MALLOC(nl * sizeof(int));
if (accel == NULL) {
fprintf(stderr, "no mem to build parser accelerators\n");
exit(1);
}
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 = PyGrammar_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 = (int *) PyObject_MALLOC((nl-k) * sizeof(int));
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];
}
PyObject_FREE(accel);
}