gecko-dev/js/public/TracingAPI.h
Steve Fink 9adc1ff74c Bug 1164294 - Implement a linear-time ephemeron marking algorithm, r=terrence, r=jonco
--HG--
extra : rebase_source : 6478019f3ef8bb4379f41d4a6258930739e3fc87
extra : source : 28c31978b8d5b9ae08bf7d54fce16062efde9f4e
2015-08-12 16:55:40 -07:00

394 lines
15 KiB
C++

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* vim: set ts=8 sts=4 et sw=4 tw=99:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef js_TracingAPI_h
#define js_TracingAPI_h
#include "jsalloc.h"
#include "js/HashTable.h"
#include "js/HeapAPI.h"
#include "js/TraceKind.h"
class JS_PUBLIC_API(JSTracer);
namespace JS {
class JS_PUBLIC_API(CallbackTracer);
template <typename T> class Heap;
template <typename T> class TenuredHeap;
// Returns a static string equivalent of |kind|.
JS_FRIEND_API(const char*)
GCTraceKindToAscii(JS::TraceKind kind);
} // namespace JS
enum WeakMapTraceKind {
// Do true ephemeron marking with an iterative weak marking phase.
DoNotTraceWeakMaps,
// Do true ephemeron marking with a weak key lookup marking phase. This is
// expected to be constant for the lifetime of a JSTracer; it does not
// change when switching from "plain" marking to weak marking.
ExpandWeakMaps,
// Trace through to all values, irrespective of whether the keys are live
// or not. Used for non-marking tracers.
TraceWeakMapValues,
// Trace through to all keys and values, irrespective of whether the keys
// are live or not. Used for non-marking tracers.
TraceWeakMapKeysValues
};
class JS_PUBLIC_API(JSTracer)
{
public:
// Return the runtime set on the tracer.
JSRuntime* runtime() const { return runtime_; }
// Return the weak map tracing behavior currently set on this tracer.
WeakMapTraceKind weakMapAction() const { return weakMapAction_; }
// An intermediate state on the road from C to C++ style dispatch.
enum class TracerKindTag {
Marking,
WeakMarking, // In weak marking phase: looking up every marked obj/script.
Tenuring,
Callback
};
bool isMarkingTracer() const { return tag_ == TracerKindTag::Marking || tag_ == TracerKindTag::WeakMarking; }
bool isWeakMarkingTracer() const { return tag_ == TracerKindTag::WeakMarking; }
bool isTenuringTracer() const { return tag_ == TracerKindTag::Tenuring; }
bool isCallbackTracer() const { return tag_ == TracerKindTag::Callback; }
inline JS::CallbackTracer* asCallbackTracer();
protected:
JSTracer(JSRuntime* rt, TracerKindTag tag,
WeakMapTraceKind weakTraceKind = TraceWeakMapValues)
: runtime_(rt), weakMapAction_(weakTraceKind), tag_(tag)
{}
private:
JSRuntime* runtime_;
WeakMapTraceKind weakMapAction_;
protected:
TracerKindTag tag_;
};
namespace JS {
class AutoTracingName;
class AutoTracingIndex;
class AutoTracingCallback;
class JS_PUBLIC_API(CallbackTracer) : public JSTracer
{
public:
CallbackTracer(JSRuntime* rt, WeakMapTraceKind weakTraceKind = TraceWeakMapValues)
: JSTracer(rt, JSTracer::TracerKindTag::Callback, weakTraceKind),
contextName_(nullptr), contextIndex_(InvalidIndex), contextFunctor_(nullptr)
{}
// Override these methods to receive notification when an edge is visited
// with the type contained in the callback. The default implementation
// dispatches to the fully-generic onChild implementation, so for cases that
// do not care about boxing overhead and do not need the actual edges,
// just override the generic onChild.
virtual void onObjectEdge(JSObject** objp) { onChild(JS::GCCellPtr(*objp)); }
virtual void onStringEdge(JSString** strp) { onChild(JS::GCCellPtr(*strp)); }
virtual void onSymbolEdge(JS::Symbol** symp) { onChild(JS::GCCellPtr(*symp)); }
virtual void onScriptEdge(JSScript** scriptp) { onChild(JS::GCCellPtr(*scriptp)); }
virtual void onShapeEdge(js::Shape** shapep) {
onChild(JS::GCCellPtr(*shapep, JS::TraceKind::Shape));
}
virtual void onObjectGroupEdge(js::ObjectGroup** groupp) {
onChild(JS::GCCellPtr(*groupp, JS::TraceKind::ObjectGroup));
}
virtual void onBaseShapeEdge(js::BaseShape** basep) {
onChild(JS::GCCellPtr(*basep, JS::TraceKind::BaseShape));
}
virtual void onJitCodeEdge(js::jit::JitCode** codep) {
onChild(JS::GCCellPtr(*codep, JS::TraceKind::JitCode));
}
virtual void onLazyScriptEdge(js::LazyScript** lazyp) {
onChild(JS::GCCellPtr(*lazyp, JS::TraceKind::LazyScript));
}
// Override this method to receive notification when a node in the GC
// heap graph is visited.
virtual void onChild(const JS::GCCellPtr& thing) = 0;
// Access to the tracing context:
// When tracing with a JS::CallbackTracer, we invoke the callback with the
// edge location and the type of target. This is useful for operating on
// the edge in the abstract or on the target thing, satisfying most common
// use cases. However, some tracers need additional detail about the
// specific edge that is being traced in order to be useful. Unfortunately,
// the raw pointer to the edge that we provide is not enough information to
// infer much of anything useful about that edge.
//
// In order to better support use cases that care in particular about edges
// -- as opposed to the target thing -- tracing implementations are
// responsible for providing extra context information about each edge they
// trace, as it is traced. This contains, at a minimum, an edge name and,
// when tracing an array, the index. Further specialization can be achived
// (with some complexity), by associating a functor with the tracer so
// that, when requested, the user can generate totally custom edge
// descriptions.
// Returns the current edge's name. It is only valid to call this when
// inside the trace callback, however, the edge name will always be set.
const char* contextName() const { MOZ_ASSERT(contextName_); return contextName_; }
// Returns the current edge's index, if marked as part of an array of edges.
// This must be called only inside the trace callback. When not tracing an
// array, the value will be InvalidIndex.
const static size_t InvalidIndex = size_t(-1);
size_t contextIndex() const { return contextIndex_; }
// Build a description of this edge in the heap graph. This call may invoke
// the context functor, if set, which may inspect arbitrary areas of the
// heap. On the other hand, the description provided by this method may be
// substantially more accurate and useful than those provided by only the
// contextName and contextIndex.
void getTracingEdgeName(char* buffer, size_t bufferSize);
// The trace implementation may associate a callback with one or more edges
// using AutoTracingDetails. This functor is called by getTracingEdgeName
// and is responsible for providing a textual representation of the
// currently being traced edge. The callback has access to the full heap,
// including the currently set tracing context.
class ContextFunctor {
public:
virtual void operator()(CallbackTracer* trc, char* buf, size_t bufsize) = 0;
};
#ifdef DEBUG
enum class TracerKind { DoNotCare, Moving, GrayBuffering, VerifyTraceProtoAndIface };
virtual TracerKind getTracerKind() const { return TracerKind::DoNotCare; }
#endif
// In C++, overriding a method hides all methods in the base class with
// that name, not just methods with that signature. Thus, the typed edge
// methods have to have distinct names to allow us to override them
// individually, which is freqently useful if, for example, we only want to
// process only one type of edge.
void dispatchToOnEdge(JSObject** objp) { onObjectEdge(objp); }
void dispatchToOnEdge(JSString** strp) { onStringEdge(strp); }
void dispatchToOnEdge(JS::Symbol** symp) { onSymbolEdge(symp); }
void dispatchToOnEdge(JSScript** scriptp) { onScriptEdge(scriptp); }
void dispatchToOnEdge(js::Shape** shapep) { onShapeEdge(shapep); }
void dispatchToOnEdge(js::ObjectGroup** groupp) { onObjectGroupEdge(groupp); }
void dispatchToOnEdge(js::BaseShape** basep) { onBaseShapeEdge(basep); }
void dispatchToOnEdge(js::jit::JitCode** codep) { onJitCodeEdge(codep); }
void dispatchToOnEdge(js::LazyScript** lazyp) { onLazyScriptEdge(lazyp); }
private:
friend class AutoTracingName;
const char* contextName_;
friend class AutoTracingIndex;
size_t contextIndex_;
friend class AutoTracingDetails;
ContextFunctor* contextFunctor_;
};
// Set the name portion of the tracer's context for the current edge.
class AutoTracingName
{
CallbackTracer* trc_;
const char* prior_;
public:
AutoTracingName(CallbackTracer* trc, const char* name) : trc_(trc), prior_(trc->contextName_) {
MOZ_ASSERT(name);
trc->contextName_ = name;
}
~AutoTracingName() {
MOZ_ASSERT(trc_->contextName_);
trc_->contextName_ = prior_;
}
};
// Set the index portion of the tracer's context for the current range.
class AutoTracingIndex
{
CallbackTracer* trc_;
public:
explicit AutoTracingIndex(JSTracer* trc, size_t initial = 0) : trc_(nullptr) {
if (trc->isCallbackTracer()) {
trc_ = trc->asCallbackTracer();
MOZ_ASSERT(trc_->contextIndex_ == CallbackTracer::InvalidIndex);
trc_->contextIndex_ = initial;
}
}
~AutoTracingIndex() {
if (trc_) {
MOZ_ASSERT(trc_->contextIndex_ != CallbackTracer::InvalidIndex);
trc_->contextIndex_ = CallbackTracer::InvalidIndex;
}
}
void operator++() {
if (trc_) {
MOZ_ASSERT(trc_->contextIndex_ != CallbackTracer::InvalidIndex);
++trc_->contextIndex_;
}
}
};
// Set a context callback for the trace callback to use, if it needs a detailed
// edge description.
class AutoTracingDetails
{
CallbackTracer* trc_;
public:
AutoTracingDetails(JSTracer* trc, CallbackTracer::ContextFunctor& func) : trc_(nullptr) {
if (trc->isCallbackTracer()) {
trc_ = trc->asCallbackTracer();
MOZ_ASSERT(trc_->contextFunctor_ == nullptr);
trc_->contextFunctor_ = &func;
}
}
~AutoTracingDetails() {
if (trc_) {
MOZ_ASSERT(trc_->contextFunctor_);
trc_->contextFunctor_ = nullptr;
}
}
};
} // namespace JS
JS::CallbackTracer*
JSTracer::asCallbackTracer()
{
MOZ_ASSERT(isCallbackTracer());
return static_cast<JS::CallbackTracer*>(this);
}
// The JS_Call*Tracer family of functions traces the given GC thing reference.
// This performs the tracing action configured on the given JSTracer:
// typically calling the JSTracer::callback or marking the thing as live.
//
// The argument to JS_Call*Tracer is an in-out param: when the function
// returns, the garbage collector might have moved the GC thing. In this case,
// the reference passed to JS_Call*Tracer will be updated to the object's new
// location. Callers of this method are responsible for updating any state
// that is dependent on the object's address. For example, if the object's
// address is used as a key in a hashtable, then the object must be removed
// and re-inserted with the correct hash.
//
extern JS_PUBLIC_API(void)
JS_CallValueTracer(JSTracer* trc, JS::Heap<JS::Value>* valuep, const char* name);
extern JS_PUBLIC_API(void)
JS_CallIdTracer(JSTracer* trc, JS::Heap<jsid>* idp, const char* name);
extern JS_PUBLIC_API(void)
JS_CallObjectTracer(JSTracer* trc, JS::Heap<JSObject*>* objp, const char* name);
extern JS_PUBLIC_API(void)
JS_CallStringTracer(JSTracer* trc, JS::Heap<JSString*>* strp, const char* name);
extern JS_PUBLIC_API(void)
JS_CallScriptTracer(JSTracer* trc, JS::Heap<JSScript*>* scriptp, const char* name);
extern JS_PUBLIC_API(void)
JS_CallFunctionTracer(JSTracer* trc, JS::Heap<JSFunction*>* funp, const char* name);
// The following JS_CallUnbarriered*Tracer functions should only be called where
// you know for sure that a heap post barrier is not required. Use with extreme
// caution!
extern JS_PUBLIC_API(void)
JS_CallUnbarrieredValueTracer(JSTracer* trc, JS::Value* valuep, const char* name);
extern JS_PUBLIC_API(void)
JS_CallUnbarrieredIdTracer(JSTracer* trc, jsid* idp, const char* name);
extern JS_PUBLIC_API(void)
JS_CallUnbarrieredObjectTracer(JSTracer* trc, JSObject** objp, const char* name);
extern JS_PUBLIC_API(void)
JS_CallUnbarrieredStringTracer(JSTracer* trc, JSString** strp, const char* name);
extern JS_PUBLIC_API(void)
JS_CallUnbarrieredScriptTracer(JSTracer* trc, JSScript** scriptp, const char* name);
template <typename HashSetEnum>
inline void
JS_CallHashSetObjectTracer(JSTracer* trc, HashSetEnum& e, JSObject* const& key, const char* name)
{
JSObject* updated = key;
JS_CallUnbarrieredObjectTracer(trc, &updated, name);
if (updated != key)
e.rekeyFront(updated);
}
// Trace an object that is known to always be tenured. No post barriers are
// required in this case.
extern JS_PUBLIC_API(void)
JS_CallTenuredObjectTracer(JSTracer* trc, JS::TenuredHeap<JSObject*>* objp, const char* name);
extern JS_PUBLIC_API(void)
JS_TraceChildren(JSTracer* trc, void* thing, JS::TraceKind kind);
extern JS_PUBLIC_API(void)
JS_TraceRuntime(JSTracer* trc);
namespace JS {
typedef js::HashSet<Zone*, js::DefaultHasher<Zone*>, js::SystemAllocPolicy> ZoneSet;
} // namespace JS
// Trace every value within |zones| that is wrapped by a cross-compartment
// wrapper from a zone that is not an element of |zones|.
extern JS_PUBLIC_API(void)
JS_TraceIncomingCCWs(JSTracer* trc, const JS::ZoneSet& zones);
extern JS_PUBLIC_API(void)
JS_GetTraceThingInfo(char* buf, size_t bufsize, JSTracer* trc,
void* thing, JS::TraceKind kind, bool includeDetails);
namespace js {
// Automates static dispatch for tracing for TraceableContainers.
template <typename, typename=void> struct DefaultTracer;
// The default for POD, non-pointer types is to do nothing.
template <typename T>
struct DefaultTracer<T, typename mozilla::EnableIf<!mozilla::IsPointer<T>::value &&
mozilla::IsPod<T>::value>::Type> {
static void trace(JSTracer* trc, T* t, const char* name) {
MOZ_ASSERT(mozilla::IsPod<T>::value);
MOZ_ASSERT(!mozilla::IsPointer<T>::value);
}
};
// The default for non-pod (e.g. struct) types is to call the trace method.
template <typename T>
struct DefaultTracer<T, typename mozilla::EnableIf<!mozilla::IsPod<T>::value>::Type> {
static void trace(JSTracer* trc, T* t, const char* name) {
t->trace(trc);
}
};
template <>
struct DefaultTracer<jsid>
{
static void trace(JSTracer* trc, jsid* id, const char* name) {
JS_CallUnbarrieredIdTracer(trc, id, name);
}
};
} // namespace js
#endif /* js_TracingAPI_h */