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