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Bug fix in lemon: 3-way conflicts (SHIFT/REDUCE/REDUCE) were not detected or

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resolved.  This is now fixed.  Also, table compression works a little better. (CVS 388)

FossilOrigin-Name: 8da0ac9a8bb859377613dd18f4f423eb49c7338b
This commit is contained in:
drh
2002-02-23 18:45:13 +00:00
parent a76b5dfca6
commit b59499c73b
3 changed files with 51 additions and 32 deletions
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69
tool/lemon.c
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@ -770,7 +770,7 @@ struct lemon *lemp;
stp = lemp->sorted[i];
assert( stp->ap );
stp->ap = Action_sort(stp->ap);
for(ap=stp->ap; ap && ap->next; ap=nap){
for(ap=stp->ap; ap && ap->next; ap=ap->next){
for(nap=ap->next; nap && nap->sp==ap->sp; nap=nap->next){
/* The two actions "ap" and "nap" have the same lookahead.
** Figure out which one should be used */
@ -848,9 +848,17 @@ struct symbol *errsym; /* The error symbol (if defined. NULL otherwise) */
apx->type = RD_RESOLVED;
}
}else{
/* Can't happen. Shifts have to come before Reduces on the
** list because the reduces were added last. Hence, if apx->type==REDUCE
** then it is impossible for apy->type==SHIFT */
assert(
apx->type==SH_RESOLVED ||
apx->type==RD_RESOLVED ||
apx->type==CONFLICT ||
apy->type==SH_RESOLVED ||
apy->type==RD_RESOLVED ||
apy->type==CONFLICT
);
/* The REDUCE/SHIFT case cannot happen because SHIFTs come before
** REDUCEs on the list. If we reach this point it must be because
** the parser conflict had already been resolved. */
}
return errcnt;
}
@ -3256,48 +3264,59 @@ struct lemon *lemp;
/* Reduce the size of the action tables, if possible, by making use
** of defaults.
**
** In this version, if all REDUCE actions use the same rule, make
** them the default. Only default them if there are more than one.
** In this version, we take the most frequent REDUCE action and make
** it the default. Only default a reduce if there are more than one.
*/
void CompressTables(lemp)
struct lemon *lemp;
{
struct state *stp;
struct action *ap;
struct rule *rp;
struct action *ap, *ap2;
struct rule *rp, *rp2, *rbest;
int nbest, n;
int i;
int cnt;
for(i=0; i<lemp->nstate; i++){
stp = lemp->sorted[i];
nbest = 0;
rbest = 0;
/* Find the first REDUCE action */
for(ap=stp->ap; ap && ap->type!=REDUCE; ap=ap->next);
if( ap==0 ) continue;
/* Remember the rule used */
rp = ap->x.rp;
/* See if all other REDUCE acitons use the same rule */
cnt = 1;
for(ap=ap->next; ap; ap=ap->next){
if( ap->type==REDUCE ){
if( ap->x.rp!=rp ) break;
cnt++;
for(ap=stp->ap; ap; ap=ap->next){
if( ap->type!=REDUCE ) continue;
rp = ap->x.rp;
if( rp==rbest ) continue;
n = 1;
for(ap2=ap->next; ap2; ap2=ap2->next){
if( ap2->type!=REDUCE ) continue;
rp2 = ap2->x.rp;
if( rp2==rbest ) continue;
if( rp2==rp ) n++;
}
if( n>nbest ){
nbest = n;
rbest = rp;
}
}
if( ap || cnt==1 ) continue;
/* Do not make a default if the number of rules to default
** is not at least 2 */
if( nbest<2 ) continue;
/* Combine all REDUCE actions into a single default */
for(ap=stp->ap; ap && ap->type!=REDUCE; ap=ap->next);
/* Combine matching REDUCE actions into a single default */
for(ap=stp->ap; ap; ap=ap->next){
if( ap->type==REDUCE && ap->x.rp==rbest ) break;
}
assert( ap );
ap->sp = Symbol_new("{default}");
for(ap=ap->next; ap; ap=ap->next){
if( ap->type==REDUCE ) ap->type = NOT_USED;
if( ap->type==REDUCE && ap->x.rp==rbest ) ap->type = NOT_USED;
}
stp->ap = Action_sort(stp->ap);
}
}
/***************** From the file "set.c" ************************************/
/*
** Set manipulation routines for the LEMON parser generator.