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xo-gc: copy/move step for collection phase

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This commit is contained in:
Roland Conybeare 2026-01-04 00:34:19 -05:00
commit f27dd9f0a1
3 changed files with 344 additions and 106 deletions
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104
src/gc/ICollector_DX1Collector.cpp
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@ -79,95 +79,7 @@ namespace xo {
AGCObject * lhs_iface,
void ** lhs_data)
{
(void)lhs_iface;
assert(d.runstate_.is_running());
/*
* lhs obj<AGCObject>
* | +---------+ +---+-+----+
* \--->| .iface | | T |G|size| header
* +---------+ object_data +---+-+----+
* | .data x----------------->| alloc |
* +---------+ | data |
* | for |
* | instance |
* | ... |
* +----------+
*/
void * object_data = (byte *)lhs_data;
if (!d.contains(role::from_space(), object_data)) {
/* *lhs isn't in GC-allocated space.
*
* This happens for a modest number of global
* constant, for example DBoolean {true, false}.
*
* It's important we recognize these up front.
* Since not allocated from GC, they don't have
* an alloc-header.
*/
return;
}
/** NOTE: for form's sake:
* better to lookup actual arena that
* allocated object data.
*
**/
DArena * some_arena = d.to_space(generation(0));
DArena::header_type * p_header
= some_arena->obj2hdr(object_data);
DArena::header_type alloc_hdr = *p_header;
/* recover allocation size */
std::size_t alloc_z = some_arena->config_.header_.size(alloc_hdr);
/* need to be able to fit forwarding pointer
* in place of forwarded object.
*
* This is guaranteed anyway, by alignment rules
*/
assert(alloc_z > sizeof(uintptr_t));
if (d.is_forwarding_header(alloc_hdr)) {
/* *lhs already refers to a forwarding pointer */
/*
* lhs obj<AGCObject>
* | +---------+ +---+-+----+
* \--->| .iface | |FWD|G|size| alloc_hdr
* +---------+ object_data +---+-+----+
* | .data x----------------->| x-------->
* +---------+ | | dest
* | |
* +----------+
*/
void * dest = *(void**)object_data;
/* update *lhs in-place */
*lhs_data = dest;
} else if (check_move_policy(d, alloc_hdr, object_data)) {
/* copy object *lhs + replace with forwarding pointer */
/* which arena are we writing to? need allocator interface */
assert(false);
#ifdef NOT_YET
// to do this need IAllocator_DX1Collector fully implemented
void * copy = (*lhs).shallow_copy(xxx);
xxx mm xxx;
#endif
} else {
/* object doesn't need to move.
* e.g. incremental collection + object is tenured
*/
}
d.forward_inplace(lhs_iface, lhs_data);
}
bool
@ -175,19 +87,7 @@ namespace xo {
header_type alloc_hdr,
void * object_data)
{
(void)object_data;
// when gc is moving objects, to- and from- spaces have been
// reversed: forwarding pointers are located in from-space and
// refer to to-space.
object_age age = d.header2age(alloc_hdr);
generation g = d.config_.age2gen(age);
assert(d.runstate_.is_running());
return (g < d.runstate_.gc_upto());
return d.check_move_policy(alloc_hdr, object_data);
}
} /*namespace mm*/