ref: b9745c60a1bf2a3876e411d38c67a0980d70e3a3
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); }