зеркало из https://github.com/mozilla/gecko-dev.git
253 строки
9.0 KiB
C++
253 строки
9.0 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
|
|
* vim: set ts=8 sts=2 et sw=2 tw=80:
|
|
* 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_TraceKind_h
|
|
#define js_TraceKind_h
|
|
|
|
#include "mozilla/UniquePtr.h"
|
|
|
|
#include "js/TypeDecls.h"
|
|
|
|
// Forward declarations of all the types a TraceKind can denote.
|
|
namespace js {
|
|
class BaseScript;
|
|
class BaseShape;
|
|
class ObjectGroup;
|
|
class RegExpShared;
|
|
class Shape;
|
|
class Scope;
|
|
namespace jit {
|
|
class JitCode;
|
|
} // namespace jit
|
|
} // namespace js
|
|
|
|
namespace JS {
|
|
|
|
// When tracing a thing, the GC needs to know about the layout of the object it
|
|
// is looking at. There are a fixed number of different layouts that the GC
|
|
// knows about. The "trace kind" is a static map which tells which layout a GC
|
|
// thing has.
|
|
//
|
|
// Although this map is public, the details are completely hidden. Not all of
|
|
// the matching C++ types are exposed, and those that are, are opaque.
|
|
//
|
|
// See Value::gcKind() and JSTraceCallback in Tracer.h for more details.
|
|
enum class TraceKind {
|
|
// These trace kinds have a publicly exposed, although opaque, C++ type.
|
|
// Note: The order here is determined by our Value packing. Other users
|
|
// should sort alphabetically, for consistency.
|
|
Object = 0x00,
|
|
BigInt = 0x01,
|
|
String = 0x02,
|
|
Symbol = 0x03,
|
|
|
|
// Shape details are exposed through JS_TraceShapeCycleCollectorChildren.
|
|
Shape = 0x04,
|
|
|
|
// ObjectGroup details are exposed through
|
|
// JS_TraceObjectGroupCycleCollectorChildren.
|
|
ObjectGroup = 0x05,
|
|
|
|
// The kind associated with a nullptr.
|
|
Null = 0x06,
|
|
|
|
// The following kinds do not have an exposed C++ idiom.
|
|
BaseShape = 0x0F,
|
|
JitCode = 0x1F,
|
|
Script = 0x2F,
|
|
Scope = 0x3F,
|
|
RegExpShared = 0x4F
|
|
};
|
|
const static uintptr_t OutOfLineTraceKindMask = 0x07;
|
|
|
|
#define ASSERT_TRACE_KIND(tk) \
|
|
static_assert( \
|
|
(uintptr_t(tk) & OutOfLineTraceKindMask) == OutOfLineTraceKindMask, \
|
|
"mask bits are set")
|
|
ASSERT_TRACE_KIND(JS::TraceKind::BaseShape);
|
|
ASSERT_TRACE_KIND(JS::TraceKind::JitCode);
|
|
ASSERT_TRACE_KIND(JS::TraceKind::Script);
|
|
ASSERT_TRACE_KIND(JS::TraceKind::Scope);
|
|
ASSERT_TRACE_KIND(JS::TraceKind::RegExpShared);
|
|
#undef ASSERT_TRACE_KIND
|
|
|
|
// When this header is imported inside SpiderMonkey, the class definitions are
|
|
// available and we can query those definitions to find the correct kind
|
|
// directly from the class hierarchy.
|
|
template <typename T>
|
|
struct MapTypeToTraceKind {
|
|
static const JS::TraceKind kind = T::TraceKind;
|
|
};
|
|
|
|
// When this header is used outside SpiderMonkey, the class definitions are not
|
|
// available, so the following table containing all public GC types is used.
|
|
//
|
|
// canBeGray: GC can mark things of this kind gray. The cycle collector
|
|
// traverses gray GC things when looking for cycles.
|
|
// inCCGraph: Things of this kind are represented as nodes in the CC graph. This
|
|
// also means they can be used as a keys in WeakMap.
|
|
|
|
// clang-format off
|
|
#define JS_FOR_EACH_TRACEKIND(D) \
|
|
/* name type canBeGray inCCGraph */ \
|
|
D(BaseShape, js::BaseShape, true, false) \
|
|
D(JitCode, js::jit::JitCode, true, false) \
|
|
D(Scope, js::Scope, true, true) \
|
|
D(Object, JSObject, true, true) \
|
|
D(ObjectGroup, js::ObjectGroup, true, false) \
|
|
D(Script, js::BaseScript, true, true) \
|
|
D(Shape, js::Shape, true, false) \
|
|
D(String, JSString, false, false) \
|
|
D(Symbol, JS::Symbol, false, false) \
|
|
D(BigInt, JS::BigInt, false, false) \
|
|
D(RegExpShared, js::RegExpShared, true, true)
|
|
// clang-format on
|
|
|
|
// Returns true if the JS::TraceKind is represented as a node in cycle collector
|
|
// graph.
|
|
inline constexpr bool IsCCTraceKind(JS::TraceKind aKind) {
|
|
switch (aKind) {
|
|
#define JS_EXPAND_DEF(name, _1, _2, inCCGraph) \
|
|
case JS::TraceKind::name: \
|
|
return inCCGraph;
|
|
JS_FOR_EACH_TRACEKIND(JS_EXPAND_DEF);
|
|
#undef JS_EXPAND_DEF
|
|
default:
|
|
return false;
|
|
}
|
|
}
|
|
|
|
// Map from all public types to their trace kind.
|
|
#define JS_EXPAND_DEF(name, type, _, _1) \
|
|
template <> \
|
|
struct MapTypeToTraceKind<type> { \
|
|
static const JS::TraceKind kind = JS::TraceKind::name; \
|
|
};
|
|
JS_FOR_EACH_TRACEKIND(JS_EXPAND_DEF);
|
|
#undef JS_EXPAND_DEF
|
|
|
|
// RootKind is closely related to TraceKind. Whereas TraceKind's indices are
|
|
// laid out for convenient embedding as a pointer tag, the indicies of RootKind
|
|
// are designed for use as array keys via EnumeratedArray.
|
|
enum class RootKind : int8_t {
|
|
// These map 1:1 with trace kinds.
|
|
#define EXPAND_ROOT_KIND(name, _0, _1, _2) name,
|
|
JS_FOR_EACH_TRACEKIND(EXPAND_ROOT_KIND)
|
|
#undef EXPAND_ROOT_KIND
|
|
|
|
// These tagged pointers are special-cased for performance.
|
|
Id,
|
|
Value,
|
|
|
|
// Everything else.
|
|
Traceable,
|
|
|
|
Limit
|
|
};
|
|
|
|
// Most RootKind correspond directly to a trace kind.
|
|
template <TraceKind traceKind>
|
|
struct MapTraceKindToRootKind {};
|
|
#define JS_EXPAND_DEF(name, _0, _1, _2) \
|
|
template <> \
|
|
struct MapTraceKindToRootKind<JS::TraceKind::name> { \
|
|
static const JS::RootKind kind = JS::RootKind::name; \
|
|
};
|
|
JS_FOR_EACH_TRACEKIND(JS_EXPAND_DEF)
|
|
#undef JS_EXPAND_DEF
|
|
|
|
// Specify the RootKind for all types. Value and jsid map to special cases;
|
|
// Cell pointer types we can derive directly from the TraceKind; everything else
|
|
// should go in the Traceable list and use GCPolicy<T>::trace for tracing.
|
|
template <typename T>
|
|
struct MapTypeToRootKind {
|
|
static const JS::RootKind kind = JS::RootKind::Traceable;
|
|
};
|
|
template <typename T>
|
|
struct MapTypeToRootKind<T*> {
|
|
static const JS::RootKind kind =
|
|
JS::MapTraceKindToRootKind<JS::MapTypeToTraceKind<T>::kind>::kind;
|
|
};
|
|
template <>
|
|
struct MapTypeToRootKind<JS::Realm*> {
|
|
// Not a pointer to a GC cell. Use GCPolicy.
|
|
static const JS::RootKind kind = JS::RootKind::Traceable;
|
|
};
|
|
template <typename T>
|
|
struct MapTypeToRootKind<mozilla::UniquePtr<T>> {
|
|
static const JS::RootKind kind = JS::MapTypeToRootKind<T>::kind;
|
|
};
|
|
template <>
|
|
struct MapTypeToRootKind<JS::Value> {
|
|
static const JS::RootKind kind = JS::RootKind::Value;
|
|
};
|
|
template <>
|
|
struct MapTypeToRootKind<jsid> {
|
|
static const JS::RootKind kind = JS::RootKind::Id;
|
|
};
|
|
template <>
|
|
struct MapTypeToRootKind<JSFunction*> : public MapTypeToRootKind<JSObject*> {};
|
|
template <>
|
|
struct MapTypeToRootKind<JSScript*>
|
|
: public MapTypeToRootKind<js::BaseScript*> {};
|
|
|
|
// Fortunately, few places in the system need to deal with fully abstract
|
|
// cells. In those places that do, we generally want to move to a layout
|
|
// templated function as soon as possible. This template wraps the upcast
|
|
// for that dispatch.
|
|
//
|
|
// Given a call:
|
|
//
|
|
// DispatchTraceKindTyped(f, thing, traceKind, ... args)
|
|
//
|
|
// Downcast the |void *thing| to the specific type designated by |traceKind|,
|
|
// and pass it to the functor |f| along with |... args|, forwarded. Pass the
|
|
// type designated by |traceKind| as the functor's template argument. The
|
|
// |thing| parameter is optional; without it, we simply pass through |... args|.
|
|
template <typename F, typename... Args>
|
|
auto DispatchTraceKindTyped(F f, JS::TraceKind traceKind, Args&&... args) {
|
|
switch (traceKind) {
|
|
#define JS_EXPAND_DEF(name, type, _, _1) \
|
|
case JS::TraceKind::name: \
|
|
return f.template operator()<type>(std::forward<Args>(args)...);
|
|
JS_FOR_EACH_TRACEKIND(JS_EXPAND_DEF);
|
|
#undef JS_EXPAND_DEF
|
|
default:
|
|
MOZ_CRASH("Invalid trace kind in DispatchTraceKindTyped.");
|
|
}
|
|
}
|
|
|
|
// Given a GC thing specified by pointer and trace kind, calls the functor |f|
|
|
// with a template argument of the actual type of the pointer and returns the
|
|
// result.
|
|
template <typename F>
|
|
auto MapGCThingTyped(void* thing, JS::TraceKind traceKind, F&& f) {
|
|
switch (traceKind) {
|
|
#define JS_EXPAND_DEF(name, type, _, _1) \
|
|
case JS::TraceKind::name: \
|
|
return f(static_cast<type*>(thing));
|
|
JS_FOR_EACH_TRACEKIND(JS_EXPAND_DEF);
|
|
#undef JS_EXPAND_DEF
|
|
default:
|
|
MOZ_CRASH("Invalid trace kind in MapGCThingTyped.");
|
|
}
|
|
}
|
|
|
|
// Given a GC thing specified by pointer and trace kind, calls the functor |f|
|
|
// with a template argument of the actual type of the pointer and ignores the
|
|
// result.
|
|
template <typename F>
|
|
void ApplyGCThingTyped(void* thing, JS::TraceKind traceKind, F&& f) {
|
|
// This function doesn't do anything but is supplied for symmetry with other
|
|
// MapGCThingTyped/ApplyGCThingTyped implementations that have to wrap the
|
|
// functor to return a dummy value that is ignored.
|
|
MapGCThingTyped(thing, traceKind, std::move(f));
|
|
}
|
|
|
|
} // namespace JS
|
|
|
|
#endif // js_TraceKind_h
|