// hash LR item sets (DFA states) - hash the elements and sum
HHashValue h_hash_lr_itemset(const void *p)
{
HHashValue hash = 0;
H_FOREACH_KEY((const HHashSet *)p, HLRItem *item)
hash += hash_lr_item(item);
H_END_FOREACH
return hash;
}
int h_lalr_compile(HAllocator* mm__, HParser* parser, const void* params)
{
// generate (augmented) CFG from parser
// construct LR(0) DFA
// build LR(0) table
// if necessary, resolve conflicts "by conversion to SLR"
if (!parser->vtable->isValidCF(parser->env)) {
return -1;
}
HCFGrammar *g = h_cfgrammar_(mm__, h_desugar_augmented(mm__, parser));
if(g == NULL) // backend not suitable (language not context-free)
return -1;
HLRDFA *dfa = h_lr0_dfa(g);
if (dfa == NULL) { // this should normally not happen
h_cfgrammar_free(g);
return -1;
}
HLRTable *table = h_lr0_table(g, dfa);
if (table == NULL) { // this should normally not happen
h_cfgrammar_free(g);
return -1;
}
if(has_conflicts(table)) {
HArena *arena = table->arena;
HLREnhGrammar *eg = enhance_grammar(g, dfa, table);
if(eg == NULL) { // this should normally not happen
h_cfgrammar_free(g);
h_lrtable_free(table);
return -1;
}
// go through the inadequate states; replace inadeq with a new list
HSlist *inadeq = table->inadeq;
table->inadeq = h_slist_new(arena);
for(HSlistNode *x=inadeq->head; x; x=x->next) {
size_t state = (uintptr_t)x->elem;
bool inadeq = false;
// clear old forall entry, it's being replaced by more fine-grained ones
table->forall[state] = NULL;
// go through each reducible item of state
H_FOREACH_KEY(dfa->states[state], HLRItem *item)
if(item->mark < item->len)
continue;
// action to place in the table cells indicated by lookahead
HLRAction *action = h_reduce_action(arena, item);
// find all LR(0)-enhanced productions matching item
HHashSet *lhss = h_hashtable_get(eg->corr, item->lhs);
assert(lhss != NULL);
H_FOREACH_KEY(lhss, HCFChoice *lhs)
assert(lhs->type == HCF_CHOICE); // XXX could be CHARSET?
for(HCFSequence **p=lhs->seq; *p; p++) {
HCFChoice **rhs = (*p)->items;
if(!match_production(eg, rhs, item->rhs, state)) {
continue;
}
// the left-hand symbol's follow set is this production's
// contribution to the lookahead
const HStringMap *fs = h_follow(1, eg->grammar, lhs);
assert(fs != NULL);
assert(fs->epsilon_branch == NULL);
assert(!h_stringmap_empty(fs));
// for each lookahead symbol, put action into table cell
if(terminals_put(table->tmap[state], fs, action) < 0)
inadeq = true;
} H_END_FOREACH // enhanced production
H_END_FOREACH // reducible item
if(inadeq) {
h_slist_push(table->inadeq, (void *)(uintptr_t)state);
}
}
}
h_cfgrammar_free(g);
parser->backend_data = table;
return has_conflicts(table)? -1 : 0;
}
