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u3: refactors u3a_take() to use road stack api

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This commit is contained in:
Joe Bryan 2020-09-14 15:44:11 -07:00
parent a0621f2bbf
commit 8b08a8b5c8
1 changed files with 31 additions and 66 deletions
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95
pkg/urbit/noun/allocate.c
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@ -1114,75 +1114,28 @@ typedef struct takeframe
u3_noun hed; u3_noun hed;
} takeframe; } takeframe;
static inline void
_ca_take_push(c3_ys mov,
c3_ys off,
c3_y tag_y,
u3_cell old,
u3_cell hed)
{
u3R->cap_p += mov;
// ensure we haven't overflowed the stack
// (off==0 means we're on a north road)
//
if ( 0 == off ) {
if( !(u3R->cap_p > u3R->hat_p) ) {
u3m_bail(c3__meme);
}
}
else {
if( !(u3R->cap_p < u3R->hat_p) ) {
u3m_bail(c3__meme);
}
}
takeframe* fam_u = u3to(takeframe, u3R->cap_p + off);
fam_u->tag_y = tag_y;
fam_u->old = old;
fam_u->hed = hed;
}
static inline takeframe
_ca_take_pop(c3_ys mov, c3_ys off)
{
takeframe* fam_u = u3to(takeframe, u3R->cap_p + off);
u3R->cap_p -= mov;
return *fam_u;
}
/* u3a_take(): gain, copying juniors. /* u3a_take(): gain, copying juniors.
*/ */
u3_noun u3_noun
u3a_take(u3_noun veb) u3a_take(u3_noun veb)
{ {
c3_assert(u3_none != veb); u3a_pile pil_u;
u3_noun pro;
c3_o nor_o = u3a_is_north(u3R);
u3t_on(coy_o); u3t_on(coy_o);
// initialize signed stack offsets (relative to north/south road) c3_assert(u3_none != veb);
u3a_pile_prep(&pil_u, sizeof(takeframe));
// push the ROOT stack frame (our termination condition)
// //
c3_o nor_o = u3a_is_north(u3R);
c3_ys mov, off;
{ {
c3_y wis_y = c3_wiseof(takeframe); takeframe* fam_u = u3a_push(&pil_u);
mov = ( c3y == nor_o ? -wis_y : wis_y ); fam_u->tag_y = TAKE_ROOT;
off = ( c3y == nor_o ? 0 : -wis_y );
} }
// stash the current stack post
//
u3p(takeframe) cap_p = u3R->cap_p;
// push the (only) ROOT stack frame (our termination condition)
//
_ca_take_push(mov, off, TAKE_ROOT, 0, 0);
// the finished copy of our current noun .veb
//
u3_noun pro;
// read from the current noun .veb // read from the current noun .veb
// //
advance: { advance: {
@ -1247,7 +1200,15 @@ u3a_take(u3_noun veb)
} }
else { else {
u3a_cell* old_u = (u3a_cell*)veb_u; u3a_cell* old_u = (u3a_cell*)veb_u;
_ca_take_push(mov, off, TAKE_HEAD, veb, 0);
{
takeframe* fam_u = u3a_push(&pil_u);
u3a_pile_sane(&pil_u);
fam_u->tag_y = TAKE_HEAD;
fam_u->old = veb;
}
veb = old_u->hed; veb = old_u->hed;
goto advance; goto advance;
} }
@ -1257,9 +1218,9 @@ u3a_take(u3_noun veb)
// consume: popped stack frame, and .pro from above // consume: popped stack frame, and .pro from above
// //
retreat: { retreat: {
takeframe fam_u = _ca_take_pop(mov, off); takeframe* fam_u = u3a_peek(&pil_u);
switch ( fam_u.tag_y ) { switch ( fam_u->tag_y ) {
default: { default: {
c3_assert(0); c3_assert(0);
} }
@ -1267,6 +1228,7 @@ u3a_take(u3_noun veb)
// .fam_u is our stack root, we're done. // .fam_u is our stack root, we're done.
// //
case TAKE_ROOT: { case TAKE_ROOT: {
u3a_pop(&pil_u);
break; break;
} }
@ -1274,9 +1236,11 @@ u3a_take(u3_noun veb)
// and advance to copy the tail // and advance to copy the tail
// //
case TAKE_HEAD: { case TAKE_HEAD: {
u3a_cell* old_u = u3a_to_ptr(fam_u.old); u3a_cell* old_u = u3a_to_ptr(fam_u->old);
fam_u->tag_y = TAKE_TAIL;
fam_u->hed = pro;
_ca_take_push(mov, off, TAKE_TAIL, fam_u.old, pro);
veb = old_u->tel; veb = old_u->tel;
goto advance; goto advance;
} }
@ -1285,9 +1249,10 @@ u3a_take(u3_noun veb)
// and produce the whole copied cell (as if it were a read from above). // and produce the whole copied cell (as if it were a read from above).
// //
case TAKE_TAIL: { case TAKE_TAIL: {
u3a_cell* old_u = u3a_to_ptr(fam_u.old); u3a_cell* old_u = u3a_to_ptr(fam_u->old);
pro = _ca_take_cell(old_u, fam_u.hed, pro); pro = _ca_take_cell(old_u, fam_u->hed, pro);
u3a_pop(&pil_u);
goto retreat; goto retreat;
} }
} }
@ -1295,7 +1260,7 @@ u3a_take(u3_noun veb)
// sanity check // sanity check
// //
c3_assert( u3R->cap_p == cap_p ); c3_assert( c3y == u3a_pile_done(&pil_u) );
u3t_off(coy_o); u3t_off(coy_o);