urbit/shrub
1
1
Fork 0
mirror of https://github.com/urbit/shrub.git synced 2024-12-13 16:03:36 +03:00
Code Issues Packages Projects Releases Wiki Activity

u3: refactors unifying equality unification

Browse Source
This commit is contained in:
Joe Bryan 2019-09-13 10:32:56 -07:00
parent a5599eaab1
commit aa25024e83
1 changed files with 70 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

100
pkg/urbit/noun/retrieve.c
View File

@ -316,16 +316,25 @@ _sing_one(u3_noun* a, u3_noun* b)
static void
_sung_one(u3_noun* a, u3_noun* b)
{
// already unified, we're done
//
if ( *a == *b ) {
return;
} else {
}
else {
// stash our road pointer
//
// XX do we need signal exclusion to safely mutate u3R?
//
u3_road* rod_u = u3R;
while ( 1 ) {
//
// we can't perform this kind of butchery on the home road,
// where asynchronous things can allocate.
//
// XX anything other than u3t_samp?
//
if ( u3R == &u3H->rod_u ) {
break;
}
@ -333,7 +342,14 @@ _sung_one(u3_noun* a, u3_noun* b)
c3_o asr_o = u3a_is_senior(u3R, *a);
c3_o bsr_o = u3a_is_senior(u3R, *b);
if ( _(asr_o) && _(bsr_o) ) {
// both [a] and [b] are in a senior road
//
// we can't switch to a senior road if GC is enabled,
// as we may be forced to (temporarily) leak a reference.
//
if ( (c3y == asr_o) &&
(c3y == bsr_o) )
{
//
// when unifying on a higher road, we can't free nouns,
// because we can't track junior nouns that point into
@ -349,46 +365,70 @@ _sung_one(u3_noun* a, u3_noun* b)
// itself, constantly running into duplicates.
//
#ifdef U3_MEMORY_DEBUG
return;
break;
#else
u3R = u3to(u3_road, u3R->par_p);
continue;
#endif
}
if ( _(asr_o) && !_(bsr_o) ){
if ( u3R == rod_u ) { u3z(*b); }
*b = *a;
}
if ( _(bsr_o) && !_(asr_o) ) {
if ( u3R == rod_u ) { u3z(*a); }
*a = *b;
}
if ( u3a_is_north(u3R) ) {
if ( *a <= *b ) {
u3k(*a);
if ( u3R == rod_u ) { u3z(*b); }
*b = *a;
} else {
u3k(*b);
if ( u3R == rod_u ) { u3z(*a); }
*a = *b;
}
}
else {
if ( *a >= *b ) {
u3k(*a);
if ( u3R == rod_u ) { u3z(*b); }
// if we're on our road, we can free
//
// it's safe to leak on inner roads;
// memory will be reclaimed when we return home.
//
// XX we should stash [b] on its road and lose it
// when return to that road.
//
c3_t loc_t = ( u3R == rod_u );
// keep [a]; it's senior
//
if ( (c3y == asr_o) &&
(c3n == bsr_o) )
{
if ( loc_t ) { u3z(*b); }
*b = *a;
} else {
u3k(*b);
if ( u3R == rod_u ) { u3z(*a); }
}
// keep [b]; it's senior
//
else if ( (c3n == asr_o) &&
(c3y == bsr_o) )
{
if ( loc_t ) { u3z(*a); }
*a = *b;
}
// both are on the current road; gain a reference
// to whichever we keep
//
else {
// keep [a]; it's deeper in the heap
//
// (N && >) || (S && <)
//
if ( (*a > *b) ==
(c3y == u3a_is_north(u3R)) )
{
u3k(*a);
if ( loc_t ) { u3z(*b); }
*b = *a;
}
// keep [b]; it's deeper in the heap
//
else {
u3k(*b);
if ( loc_t ) { u3z(*a); }
*a = *b;
}
}
}
break;
}
}
// restore our road pointer
//
u3R = rod_u;
}
}