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#include <inttypes.h>
#include <atomic>
#include <utility>
#include <vector>
#include "RuntimePrivate.h"
#include "WAVM/Inline/BasicTypes.h"
#include "WAVM/Inline/Errors.h"
#include "WAVM/Inline/Hash.h"
#include "WAVM/Inline/HashSet.h"
#include "WAVM/Inline/Timing.h"
#include "WAVM/Logging/Logging.h"
#include "WAVM/Platform/RWMutex.h"
#include "WAVM/Runtime/Runtime.h"
using namespace WAVM;
using namespace WAVM::Runtime;
Runtime::GCObject::GCObject(ObjectKind inKind,
Compartment* inCompartment,
std::string&& inDebugName)
: Object{inKind}
, compartment(inCompartment)
, userData(nullptr)
, finalizeUserData(nullptr)
, debugName(inDebugName)
{
}
#define IMPLEMENT_GCOBJECT_REFCOUNTING(Type) \
void Runtime::addGCRoot(const Type* object) { ++object->numRootReferences; } \
void Runtime::removeGCRoot(const Type* object) noexcept { --object->numRootReferences; }
IMPLEMENT_GCOBJECT_REFCOUNTING(Table)
IMPLEMENT_GCOBJECT_REFCOUNTING(Memory)
IMPLEMENT_GCOBJECT_REFCOUNTING(Global)
IMPLEMENT_GCOBJECT_REFCOUNTING(ExceptionType)
IMPLEMENT_GCOBJECT_REFCOUNTING(Instance)
IMPLEMENT_GCOBJECT_REFCOUNTING(Context)
IMPLEMENT_GCOBJECT_REFCOUNTING(Compartment)
IMPLEMENT_GCOBJECT_REFCOUNTING(Foreign)
void Runtime::addGCRoot(const Function* function)
{
WAVM_ASSERT(function->mutableData);
++function->mutableData->numRootReferences;
}
void Runtime::removeGCRoot(const Function* function) noexcept
{
WAVM_ASSERT(function->mutableData);
--function->mutableData->numRootReferences;
}
void Runtime::addGCRoot(const Object* object)
{
if(object->kind == ObjectKind::function) { addGCRoot((const Function*)object); }
else
{
const GCObject* gcObject = static_cast<const GCObject*>(object);
++gcObject->numRootReferences;
}
}
void Runtime::removeGCRoot(const Object* object) noexcept
{
if(object->kind == ObjectKind::function) { removeGCRoot((const Function*)object); }
else
{
GCObject* gcObject = (GCObject*)object;
--gcObject->numRootReferences;
}
}
struct GCState
{
Compartment* compartment;
HashSet<GCObject*> unreferencedObjects;
std::vector<GCObject*> pendingScanObjects;
GCState(Compartment* inCompartment) : compartment(inCompartment) {}
void visitReference(Object* object)
{
if(object)
{
if(object->kind == ObjectKind::function)
{
Function* function = asFunction(object);
if(function->instanceId != UINTPTR_MAX)
{
WAVM_ASSERT(compartment->instances.contains(function->instanceId));
Instance* instance = compartment->instances[function->instanceId];
visitReference(instance);
}
}
else if(unreferencedObjects.remove((GCObject*)object))
{
pendingScanObjects.push_back((GCObject*)object);
}
}
}
template<typename Array> void visitReferenceArray(const Array& array)
{
for(auto reference : array) { visitReference(asObject(reference)); }
}
void initGCObject(GCObject* object, bool forceRoot = false)
{
if(forceRoot || object->numRootReferences > 0) { pendingScanObjects.push_back(object); }
else
{
unreferencedObjects.add(object);
}
}
void scanObject(GCObject* object)
{
WAVM_ASSERT(!object->compartment || object->compartment == compartment);
visitReference(object->compartment);
// Gather the child references for this object based on its kind.
switch(object->kind)
{
case ObjectKind::table: {
Table* table = asTable(object);
Platform::RWMutex::ShareableLock resizingLock(table->resizingMutex);
const Uptr numElements = getTableNumElements(table);
for(Uptr elementIndex = 0; elementIndex < numElements; ++elementIndex)
{ visitReference(getTableElement(table, elementIndex)); }
break;
}
case ObjectKind::global: {
Global* global = asGlobal(object);
if(isReferenceType(global->type.valueType))
{
if(global->type.isMutable)
{
visitReference(
compartment->initialContextMutableGlobals[global->mutableGlobalIndex]
.object);
for(Context* context : compartment->contexts)
{
visitReference(
context->runtimeData->mutableGlobals[global->mutableGlobalIndex]
.object);
}
}
visitReference(global->initialValue.object);
}
break;
}
case ObjectKind::instance: {
Instance* instance = asInstance(object);
visitReferenceArray(instance->functions);
visitReferenceArray(instance->tables);
visitReferenceArray(instance->memories);
visitReferenceArray(instance->globals);
visitReferenceArray(instance->exceptionTypes);
break;
}
case ObjectKind::compartment: {
WAVM_ASSERT(object == compartment);
break;
}
case ObjectKind::memory:
case ObjectKind::exceptionType:
case ObjectKind::context: break;
case ObjectKind::function:
case ObjectKind::foreign:
case ObjectKind::invalid:
default: WAVM_UNREACHABLE();
};
}
};
static bool collectGarbageImpl(Compartment* compartment)
{
Platform::RWMutex::ExclusiveLock compartmentLock(compartment->mutex);
Timing::Timer timer;
GCState state(compartment);
// Initialize the GC state from the compartment's various sets of objects.
state.initGCObject(compartment);
for(Instance* instance : compartment->instances)
{
if(instance)
{
// Transfer root markings from functions to their instance.
bool hasRootFunction = false;
for(Function* function : instance->functions)
{
if(function && function->mutableData->numRootReferences
&& function->instanceId == instance->id)
{
hasRootFunction = true;
break;
}
}
state.initGCObject(instance, hasRootFunction);
}
}
for(Memory* memory : compartment->memories) { state.initGCObject(memory); }
for(Table* table : compartment->tables) { state.initGCObject(table); }
for(ExceptionType* exceptionType : compartment->exceptionTypes)
{ state.initGCObject(exceptionType); }
for(Global* global : compartment->globals) { state.initGCObject(global); }
for(Context* context : compartment->contexts) { state.initGCObject(context); }
// Scan the objects added to the referenced set so far: gather their child references and
// recurse.
const Uptr numInitialObjects
= state.pendingScanObjects.size() + state.unreferencedObjects.size();
const Uptr numRoots = state.pendingScanObjects.size();
while(state.pendingScanObjects.size())
{
GCObject* object = state.pendingScanObjects.back();
state.pendingScanObjects.pop_back();
state.scanObject(object);
};
// Delete each unreferenced object that isn't the compartment.
bool wasCompartmentUnreferenced = false;
for(GCObject* object : state.unreferencedObjects)
{
if(object == compartment) { wasCompartmentUnreferenced = true; }
else
{
delete object;
}
}
// Delete the compartment last, if it wasn't referenced.
compartmentLock.unlock();
if(wasCompartmentUnreferenced) { delete compartment; }
Log::printf(Log::metrics,
"Collected garbage in %.2fms: %" WAVM_PRIuPTR " roots, %" WAVM_PRIuPTR
" objects, %" WAVM_PRIuPTR " garbage\n",
timer.getMilliseconds(),
numRoots,
numInitialObjects,
Uptr(state.unreferencedObjects.size()));
return wasCompartmentUnreferenced;
}
void Runtime::collectCompartmentGarbage(Compartment* compartment)
{
collectGarbageImpl(compartment);
}
bool Runtime::tryCollectCompartment(GCPointer<Compartment>&& compartmentRootRef)
{
Compartment* compartment = &*compartmentRootRef;
compartmentRootRef = nullptr;
return collectGarbageImpl(compartment);
}
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