Index: tool/lemon.c ================================================================== --- tool/lemon.c +++ tool/lemon.c @@ -339,10 +339,11 @@ enum e_action type; union { struct state *stp; /* The new state, if a shift */ struct rule *rp; /* The rule, if a reduce */ } x; + struct symbol *spOpt; /* SHIFTREDUCE optimization to this symbol */ struct action *next; /* Next action for this state */ struct action *collide; /* Next action with the same hash */ }; /* Each state of the generated parser's finite state machine @@ -530,10 +531,11 @@ newaction = Action_new(); newaction->next = *app; *app = newaction; newaction->type = type; newaction->sp = sp; + newaction->spOpt = 0; if( type==SHIFT ){ newaction->x.stp = (struct state *)arg; }else{ newaction->x.rp = (struct rule *)arg; } @@ -3165,10 +3167,13 @@ break; case NOT_USED: result = 0; break; } + if( result && ap->spOpt ){ + fprintf(fp," /* because %s==%s */", ap->sp->name, ap->spOpt->name); + } return result; } /* Generate the "*.out" log file */ void ReportOutput(struct lemon *lemp) @@ -4507,11 +4512,11 @@ ** is a possible look-ahead. */ void CompressTables(struct lemon *lemp) { struct state *stp; - struct action *ap, *ap2; + struct action *ap, *ap2, *nextap; struct rule *rp, *rp2, *rbest; int nbest, n; int i; int usesWildcard; @@ -4584,10 +4589,40 @@ ap->type = SHIFTREDUCE; ap->x.rp = pNextState->pDfltReduce; } } } + + /* If a SHIFTREDUCE action specifies a rule that has a single RHS term + ** (meaning that the SHIFTREDUCE will land back in the state where it + ** started) and if there is no C-code associated with the reduce action, + ** then we can go ahead and convert the action to be the same as the + ** action for the RHS of the rule. + */ + for(i=0; instate; i++){ + stp = lemp->sorted[i]; + for(ap=stp->ap; ap; ap=nextap){ + nextap = ap->next; + if( ap->type!=SHIFTREDUCE ) continue; + rp = ap->x.rp; + if( rp->noCode==0 ) continue; + if( rp->nrhs!=1 ) continue; +#if 1 + /* Only apply this optimization to non-terminals. It would be OK to + ** apply it to terminal symbols too, but that makes the parser tables + ** larger. */ + if( ap->sp->indexnterminal ) continue; +#endif + /* If we reach this point, it means the optimization can be applied */ + nextap = ap; + for(ap2=stp->ap; ap2 && (ap2==ap || ap2->sp!=rp->lhs); ap2=ap2->next){} + assert( ap2!=0 ); + ap->spOpt = ap2->sp; + ap->type = ap2->type; + ap->x = ap2->x; + } + } } /* ** Compare two states for sorting purposes. The smaller state is the