ref: 17ebe55031ae6945ad1f671b69267a672328e4b1
dir: /sys/src/cmd/python/Parser/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); }