xo-alloc2: progress on forwarding objects [WIP]

This commit is contained in:
Roland Conybeare 2025-12-15 00:56:49 -05:00
commit 31a8a8ae48
16 changed files with 499 additions and 37 deletions

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@ -10,6 +10,7 @@ set(SELF_SRCS
ICollector_Any.cpp
IGCObject_Any.cpp
IAllocator_DX1Collector.cpp
ICollector_DX1Collector.cpp
DX1Collector.cpp

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@ -238,6 +238,16 @@ namespace xo {
error_count_ = 0;
last_error_ = AllocatorError();
}
DArena::header_type *
DArena::obj2hdr(void * obj)
{
assert(config_.store_header_flag_);
return (header_type *)((byte *)obj - sizeof(header_type));
}
}
} /*namespace xo*/

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@ -4,15 +4,84 @@
**/
#include "gc/DX1Collector.hpp"
#include "gc/generation.hpp"
#include <_types/_uint32_t.h>
#include <cassert>
#include <cstdint>
namespace xo {
namespace mm {
#ifdef NOT_USING
constexpr std::uint64_t
CollectorConfig::gen_mult() const {
return 1ul << arena_config_.header_size_bits_;
}
#endif
constexpr std::uint64_t
CollectorConfig::gen_shift() const {
return arena_config_.header_size_bits_;
}
constexpr std::uint64_t
CollectorConfig::gen_mask_unshifted() const {
return (1ul << gen_bits_) - 1;
}
constexpr std::uint64_t
CollectorConfig::gen_mask_shifted() const {
return gen_mask_unshifted() << arena_config_.header_size_bits_;
}
#ifdef NOT_USING
constexpr std::uint64_t
CollectorConfig::tseq_mult() const {
return 1ul << (gen_bits_ + arena_config_.header_size_bits_);
}
#endif
constexpr std::uint64_t
CollectorConfig::tseq_shift() const {
return gen_bits_ + arena_config_.header_size_bits_;
}
constexpr std::uint64_t
CollectorConfig::tseq_mask_unshifted() const {
return (1ul << tseq_bits_) - 1;
}
constexpr std::uint64_t
CollectorConfig::tseq_mask_shifted() const {
return tseq_mask_unshifted() << (gen_bits_ + arena_config_.header_size_bits_);
}
// ----- GCRunState -----
GCRunState::GCRunState(generation gc_upto)
: gc_upto_{gc_upto}
{}
GCRunState
GCRunState::gc_not_running()
{
return GCRunState(generation(0));
}
GCRunState
GCRunState::gc_upto(generation g)
{
return GCRunState(generation(g + 1));
}
// ----- DX1Collector -----
DX1Collector::DX1Collector(const CollectorConfig & cfg) : config_{cfg}
{
assert(config_.arena_config_.header_size_bits_ + config_.gen_bits_ + config_.tseq_bits_ <= 64);
for (uint32_t igen = 0, ngen = cfg.n_generation_; igen < ngen; ++igen) {
space_storage_[0][igen] = std::move(DArena::map(cfg.arena_config_));
space_storage_[1][igen] = std::move(DArena::map(cfg.arena_config_));
space_storage_[0][igen] = DArena::map(cfg.arena_config_);
space_storage_[1][igen] = DArena::map(cfg.arena_config_);
space_[role::to_space()][igen] = &space_storage_[0][igen];
space_[role::from_space()][igen] = &space_storage_[1][igen];
@ -24,6 +93,50 @@ namespace xo {
}
}
bool
DX1Collector::contains(role r, void * addr) const
{
for (generation gi{0}; gi < config_.n_generation_; ++gi) {
if (get_space(r, gi)->contains(addr))
return true;
}
return false;
}
std::size_t
DX1Collector::header2size(header_type hdr) const
{
uint32_t z = (hdr & config_.arena_config_.header_size_mask_);
return z;
}
generation
DX1Collector::header2gen(header_type hdr) const
{
uint32_t g = (hdr & config_.gen_mask_shifted()) >> config_.gen_shift();
assert(g < c_max_generation);
return generation(g);
}
uint32_t
DX1Collector::header2tseq(header_type hdr) const
{
uint32_t tseq = (hdr & config_.tseq_mask_shifted()) >> config_.tseq_shift();
return tseq;
}
bool
DX1Collector::is_forwarding_header(header_type hdr) const
{
/** all 1 bits to flag forwarding pointer **/
return header2tseq(hdr) == config_.tseq_mask_shifted();
}
void
DX1Collector::reverse_roles(generation g) {
assert(g < config_.n_generation_);

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@ -24,7 +24,7 @@ namespace xo {
size_t
IAllocator_DArena::reserved(const DArena & s) noexcept {
return s.hi_ - s.lo_;
return s.reserved();
}
size_t
@ -34,12 +34,12 @@ namespace xo {
size_t
IAllocator_DArena::committed(const DArena & s) noexcept {
return s.committed_z_;
return s.committed();
}
size_t
IAllocator_DArena::available(const DArena & s) noexcept {
return s.limit_ - s.free_;
return s.available();
}
size_t

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@ -0,0 +1,11 @@
/** @file IAllocator_DX1Collector.cpp
*
* @author Roland Conybeare, Dec 2025
**/
namespace xo {
namespace mm {
} /*namespace mm*/
} /*namespace xo*/
/* end IAllocator_DX1Collector.cpp */

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@ -4,9 +4,182 @@
**/
#include "gc/ICollector_DX1Collector.hpp"
#include "GCObject.hpp"
namespace xo {
namespace mm {
using size_type = ICollector_DX1Collector::size_type;
using std::byte;
namespace {
size_type
stat_helper(const DX1Collector & d,
size_type (DArena::* getter)() const,
generation g,
role r)
{
const DArena * arena = d.get_space(r, g);
if (arena) [[likely]]
return (arena->*getter)();
return 0;
}
}
size_type
ICollector_DX1Collector::reserved(const DX1Collector & d, generation g, role r)
{
return stat_helper(d, &DArena::reserved, g, r);
}
size_type
ICollector_DX1Collector::allocated(const DX1Collector & d, generation g, role r)
{
return stat_helper(d, &DArena::allocated, g, r);
}
size_type
ICollector_DX1Collector::committed(const DX1Collector & d, generation g, role r)
{
return stat_helper(d, &DArena::committed, g, r);
}
void
ICollector_DX1Collector::install_type(DX1Collector & d,
std::int32_t tseq,
IGCObject_Any & iface)
{
(void)d;
(void)tseq;
(void)iface;
assert(false);
}
void
ICollector_DX1Collector::add_gc_root(DX1Collector & d,
int32_t tseq,
Opaque * root)
{
(void)d;
(void)tseq;
(void)root;
assert(false);
}
void
ICollector_DX1Collector::forward_inplace(DX1Collector & d,
obj<AGCObject> * lhs)
{
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).opaque_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_mask_ & 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).reset_opaque(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
*/
}
}
bool
ICollector_DX1Collector::check_move_policy(const DX1Collector & d,
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.
generation g = d.header2gen(alloc_hdr);
assert(d.runstate_.is_running());
return (g < d.runstate_.gc_upto());
}
} /*namespace mm*/
} /*namespace xo*/