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Merge pull request #90 from microsoft/refactor-finalisation
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Modified finaliser to collect subregions
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@mjp41
mjp41 committed Jun 8, 2020
2 parents b0e53f7 + f13b01e commit fe80d41
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Showing 37 changed files with 339 additions and 272 deletions.
32 changes: 27 additions & 5 deletions src/interpreter/object.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -30,10 +30,12 @@ namespace verona::interpreter
// skip it. In that case, there are also obviously no iso fields.
rt::Descriptor::destructor =
field_count > 0 ? VMObject::destructor_fn : nullptr;
rt::Descriptor::trace_possibly_iso =
field_count > 0 ? VMObject::trace_fn : nullptr;
// In the VM object we always need a finaliser in case it has an iso field.
// The finaliser will collect the iso references that will be deallocated
// at the end of this phase.
// TODO: Can be optimised if we look at the types of all the fields
rt::Descriptor::finaliser =
finaliser_ip > 0 ? VMObject::finaliser_fn : nullptr;
finaliser_ip > 0 ? VMObject::finaliser_fn : VMObject::collect_iso_fields;
}

VMObject::VMObject(VMObject* region, const VMDescriptor* desc)
Expand All @@ -58,7 +60,7 @@ namespace verona::interpreter
}
}

void VMObject::trace_fn(const rt::Object* base_object, rt::ObjectStack* stack)
void VMObject::trace_fn(const rt::Object* base_object, rt::ObjectStack& stack)
{
const VMObject* object = static_cast<const VMObject*>(base_object);
const VMDescriptor* descriptor = object->descriptor();
Expand All @@ -69,10 +71,30 @@ namespace verona::interpreter
}
}

void VMObject::finaliser_fn(rt::Object* base_object)
void VMObject::finaliser_fn(
rt::Object* base_object, rt::Object* region, rt::ObjectStack& sub_regions)
{
VMObject* object = static_cast<VMObject*>(base_object);

VM::execute_finaliser(object);

collect_iso_fields(base_object, region, sub_regions);
}

void VMObject::collect_iso_fields(
rt::Object* base_object, rt::Object* region, rt::ObjectStack& sub_regions)
{
// The interpreter doesn't need the region, as the FieldValue type contains
// the ISO information in its fat pointers.
UNUSED(region);

VMObject* object = static_cast<VMObject*>(base_object);
const VMDescriptor* descriptor = object->descriptor();

for (size_t i = 0; i < descriptor->field_count; i++)
{
object->fields[i].add_isos(sub_regions);
}
}

void VMObject::destructor_fn(rt::Object* base_object)
Expand Down
21 changes: 11 additions & 10 deletions src/interpreter/object.h
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Original file line number Diff line number Diff line change
Expand Up @@ -43,8 +43,15 @@ namespace verona::interpreter

VMObject* region();

static void trace_fn(const rt::Object* base_object, rt::ObjectStack* stack);
static void finaliser_fn(rt::Object* base_object);
static void trace_fn(const rt::Object* base_object, rt::ObjectStack& stack);
static void finaliser_fn(
rt::Object* base_object,
rt::Object* region,
rt::ObjectStack& sub_regions);
static void collect_iso_fields(
rt::Object* base_object,
rt::Object* region,
rt::ObjectStack& sub_regions);
static void destructor_fn(rt::Object* base_object);

private:
Expand Down Expand Up @@ -81,16 +88,10 @@ namespace verona::interpreter
rt::VCown<VMCown>::schedule();
}

void trace(rt::ObjectStack* stack)
void trace(rt::ObjectStack& stack)
{
if (contents != nullptr)
stack->push(contents);
}

void trace_possibly_iso(rt::ObjectStack* stack)
{
if (contents != nullptr)
stack->push(contents);
stack.push(contents);
}
};
}
31 changes: 28 additions & 3 deletions src/interpreter/value.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -297,18 +297,18 @@ namespace verona::interpreter
return result;
}

void FieldValue::trace(rt::ObjectStack* stack) const
void FieldValue::trace(rt::ObjectStack& stack) const
{
switch (tag)
{
case Value::ISO:
case Value::MUT:
case Value::IMM:
stack->push(inner.object);
stack.push(inner.object);
break;

case Value::COWN:
stack->push(inner.cown);
stack.push(inner.cown);
break;

case Value::UNINIT:
Expand All @@ -325,6 +325,31 @@ namespace verona::interpreter
}
}

void FieldValue::add_isos(rt::ObjectStack& stack) const
{
switch (tag)
{
case Value::ISO:
stack.push(inner.object);
break;

case Value::COWN:
case Value::MUT:
case Value::IMM:
case Value::UNINIT:
case Value::U64:
case Value::STRING:
case Value::DESCRIPTOR:
break;

case Value::COWN_UNOWNED:
// Cannot be part of the heap.
abort();

EXHAUSTIVE_SWITCH
}
}

FieldValue::~FieldValue()
{
switch (tag)
Expand Down
10 changes: 8 additions & 2 deletions src/interpreter/value.h
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Original file line number Diff line number Diff line change
Expand Up @@ -145,7 +145,7 @@ namespace verona::interpreter
return &inner;
}

void trace(rt::ObjectStack* stack) const;
void trace(rt::ObjectStack& stack) const;

static constexpr Tag UNINIT = Tag::UNINIT;
static constexpr Tag ISO = Tag::ISO;
Expand Down Expand Up @@ -190,7 +190,13 @@ namespace verona::interpreter
*/
Value exchange(rt::Alloc* alloc, rt::Object* region, Value&& value);

void trace(rt::ObjectStack* stack) const;
void trace(rt::ObjectStack& stack) const;

/**
* If this Value contains an ISO, then add it to the stack
* Otherwise, do nothing.
**/
void add_isos(rt::ObjectStack& stack) const;

friend fmt::formatter<Value>;

Expand Down
4 changes: 2 additions & 2 deletions src/rt/cpp/vaction.h
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,7 @@ namespace verona::rt
friend class Cown;

private:
static void gc_trace(const Action* msg, ObjectStack* st)
static void gc_trace(const Action* msg, ObjectStack& st)
{
(static_cast<const T*>(msg))->trace(st);
}
Expand All @@ -51,7 +51,7 @@ namespace verona::rt
return &desc;
}

void trace(ObjectStack*) const {}
void trace(ObjectStack&) const {}

public:
VAction() : Action(desc())
Expand Down
28 changes: 6 additions & 22 deletions src/rt/cpp/vobject.h
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Original file line number Diff line number Diff line change
Expand Up @@ -20,15 +20,6 @@ namespace verona::rt
//
// This is better than ignoring methods with the right name but the wrong
// signature.
template<class T, class = void>
struct has_trace_possibly_iso : std::false_type
{};
template<class T>
struct has_trace_possibly_iso<
T,
std::void_t<decltype(&T::trace_possibly_iso)>> : std::true_type
{};

template<class T, class = void>
struct has_notified : std::false_type
{};
Expand Down Expand Up @@ -66,27 +57,21 @@ namespace verona::rt

using RegionClass = typename RegionType_to_class<region_type>::T;

static void gc_trace(const Object* o, ObjectStack* st)
static void gc_trace(const Object* o, ObjectStack& st)
{
((T*)o)->trace(st);
}

static void gc_trace_possibly_iso(const Object* o, ObjectStack* st)
{
if constexpr (has_trace_possibly_iso<T>::value)
((T*)o)->trace_possibly_iso(st);
}

static void gc_notified(Object* o)
{
if constexpr (has_notified<T>::value)
((T*)o)->notified(o);
}

static void gc_final(Object* o)
static void gc_final(Object* o, Object* region, ObjectStack& sub_regions)
{
if constexpr (has_finaliser<T>::value)
((T*)o)->finaliser();
((T*)o)->finaliser(region, sub_regions);
}

static void gc_destructor(Object* o)
Expand All @@ -99,15 +84,14 @@ namespace verona::rt
static constexpr Descriptor desc = {
sizeof(T),
gc_trace,
has_trace_possibly_iso<T>::value ? gc_trace_possibly_iso : nullptr,
has_finaliser<T>::value ? gc_final : nullptr,
has_notified<T>::value ? gc_notified : nullptr,
has_destructor<T>::value ? gc_destructor : nullptr};

return &desc;
}

void trace(ObjectStack*) {}
void trace(ObjectStack&) {}

static EpochMark get_alloc_epoch()
{
Expand All @@ -131,7 +115,7 @@ namespace verona::rt
if constexpr (std::is_same_v<Base, Object>)
return RegionClass::template create<sizeof(T)>(alloc, desc());
else
return ThreadAlloc::get()->alloc<sizeof(T)>();
return alloc->alloc<sizeof(T)>();
}

void* operator new(size_t, Object* region)
Expand All @@ -148,7 +132,7 @@ namespace verona::rt
if constexpr (std::is_same_v<Base, Object>)
return RegionClass::template alloc<sizeof(T)>(alloc, region, desc());
else
return ThreadAlloc::get()->alloc<sizeof(T)>();
return alloc->alloc<sizeof(T)>();
}

void operator delete(void*)
Expand Down
59 changes: 25 additions & 34 deletions src/rt/object/object.h
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Original file line number Diff line number Diff line change
Expand Up @@ -85,8 +85,7 @@ namespace verona::rt
{
// for field in o do
// st.push(o.field)
using TraceFunction = void (*)(const Object* o, ObjectStack* st);
using TraceIsoFunction = void (*)(const Object* o, ObjectStack* st);
using TraceFunction = void (*)(const Object* o, ObjectStack& st);

using NotifiedFunction = void (*)(Object* o);

Expand All @@ -102,14 +101,15 @@ namespace verona::rt
// invalid state ie. close file descriptors or deallocate some auxiliary
// storage.
//
// The finaliser can extract sub-regions and eg. send them in a
// multi-message. The destructor on the other hand may not do this.
using FinalFunction = void (*)(Object* o);
// The finaliser can must add all the subregions reachable from this object
// to the ObjectStack it is passed, so that they can be deallocated once
// this region has been deallocated.
using FinalFunction = void (*)(Object* o, Object* region, ObjectStack& st);

using DestructorFunction = void (*)(Object* o);

size_t size;
TraceFunction trace;
TraceIsoFunction trace_possibly_iso;
FinalFunction finaliser;
NotifiedFunction notified = nullptr;
DestructorFunction destructor = nullptr;
Expand Down Expand Up @@ -702,15 +702,9 @@ namespace verona::rt
return get_descriptor()->destructor != nullptr;
}

inline bool has_possibly_iso_fields()
{
return get_descriptor()->trace_possibly_iso != nullptr;
}

static inline bool is_trivial(const Descriptor* desc)
{
return desc->destructor == nullptr && desc->finaliser == nullptr &&
desc->trace_possibly_iso == nullptr;
return desc->destructor == nullptr && desc->finaliser == nullptr;
}

inline bool is_trivial()
Expand All @@ -729,18 +723,13 @@ namespace verona::rt
private:
inline void trace(ObjectStack& f) const
{
get_descriptor()->trace(this, &f);
}

inline void trace_possibly_iso(ObjectStack& f) const
{
get_descriptor()->trace_possibly_iso(this, &f);
get_descriptor()->trace(this, f);
}

inline void finalise()
inline void finalise(Object* region, ObjectStack& isos)
{
if (has_finaliser())
get_descriptor()->finaliser(this);
get_descriptor()->finaliser(this, region, isos);
}

inline void notified()
Expand All @@ -760,21 +749,23 @@ namespace verona::rt
alloc->dealloc(this, size());
}

inline void
find_iso_fields(Object* region_entry, ObjectStack& f, ObjectStack& iso_st)
protected:
static void
add_sub_region(Object* obj, Object* region, ObjectStack& sub_regions)
{
// Find all isolated fields in p other than some predecessor o.
if (!has_possibly_iso_fields())
return;

trace_possibly_iso(f);

while (!f.empty())
// Should be the entry-point of the region.
assert(
(region == nullptr) || (region->get_class() == Object::RegionMD::ISO));
// Have to be careful about internal references to the entry point for the
// `region` i.e. when obj == region we are refering to the entry point
// from inside the region and should not treat this as a subregion
// pointer.
if ((obj != nullptr) && (obj != region))
{
Object* o = f.pop();

if ((o != region_entry) && (o->get_class() == Object::ISO))
iso_st.push(o);
if (obj->get_class() == Object::RegionMD::ISO)
{
sub_regions.push(obj);
}
}
}
};
Expand Down
2 changes: 1 addition & 1 deletion src/rt/region/externalreference.h
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Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,7 @@ namespace verona::rt
// The object externally referred to
Object* o;

static void gc_trace(const Object*, ObjectStack*) {}
static void gc_trace(const Object*, ObjectStack&) {}

static const Descriptor* desc()
{
Expand Down
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