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authorMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
committerMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
commit5f8de423f190bbb79a62f804151bc24824fa32d8 (patch)
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Add m-esr52 at 52.6.0
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+/* -*- 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_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 BaseShape;
+class LazyScript;
+class ObjectGroup;
+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,
+ String = 0x01,
+ Symbol = 0x02,
+ Script = 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,
+ LazyScript = 0x2F,
+ Scope = 0x3F
+};
+const static uintptr_t OutOfLineTraceKindMask = 0x07;
+static_assert(uintptr_t(JS::TraceKind::BaseShape) & OutOfLineTraceKindMask, "mask bits are set");
+static_assert(uintptr_t(JS::TraceKind::JitCode) & OutOfLineTraceKindMask, "mask bits are set");
+static_assert(uintptr_t(JS::TraceKind::LazyScript) & OutOfLineTraceKindMask, "mask bits are set");
+static_assert(uintptr_t(JS::TraceKind::Scope) & OutOfLineTraceKindMask, "mask bits are set");
+
+// 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.
+#define JS_FOR_EACH_TRACEKIND(D) \
+ /* PrettyName TypeName AddToCCKind */ \
+ D(BaseShape, js::BaseShape, true) \
+ D(JitCode, js::jit::JitCode, true) \
+ D(LazyScript, js::LazyScript, true) \
+ D(Scope, js::Scope, true) \
+ D(Object, JSObject, true) \
+ D(ObjectGroup, js::ObjectGroup, true) \
+ D(Script, JSScript, true) \
+ D(Shape, js::Shape, true) \
+ D(String, JSString, false) \
+ D(Symbol, JS::Symbol, false)
+
+// Map from all public types to their trace kind.
+#define JS_EXPAND_DEF(name, type, _) \
+ 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) \
+ 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) \
+ 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;
+// 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 <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*> {};
+
+// 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|.
+
+// GCC and Clang require an explicit template declaration in front of the
+// specialization of operator() because it is a dependent template. MSVC, on
+// the other hand, gets very confused if we have a |template| token there.
+// The clang-cl front end defines _MSC_VER, but still requires the explicit
+// template declaration, so we must test for __clang__ here as well.
+#if defined(_MSC_VER) && !defined(__clang__)
+# define JS_DEPENDENT_TEMPLATE_HINT
+#else
+# define JS_DEPENDENT_TEMPLATE_HINT template
+#endif
+template <typename F, typename... Args>
+auto
+DispatchTraceKindTyped(F f, JS::TraceKind traceKind, Args&&... args)
+ -> decltype(f. JS_DEPENDENT_TEMPLATE_HINT operator()<JSObject>(mozilla::Forward<Args>(args)...))
+{
+ switch (traceKind) {
+#define JS_EXPAND_DEF(name, type, _) \
+ case JS::TraceKind::name: \
+ return f. JS_DEPENDENT_TEMPLATE_HINT operator()<type>(mozilla::Forward<Args>(args)...);
+ JS_FOR_EACH_TRACEKIND(JS_EXPAND_DEF);
+#undef JS_EXPAND_DEF
+ default:
+ MOZ_CRASH("Invalid trace kind in DispatchTraceKindTyped.");
+ }
+}
+#undef JS_DEPENDENT_TEMPLATE_HINT
+
+template <typename F, typename... Args>
+auto
+DispatchTraceKindTyped(F f, void* thing, JS::TraceKind traceKind, Args&&... args)
+ -> decltype(f(static_cast<JSObject*>(nullptr), mozilla::Forward<Args>(args)...))
+{
+ switch (traceKind) {
+#define JS_EXPAND_DEF(name, type, _) \
+ case JS::TraceKind::name: \
+ return f(static_cast<type*>(thing), mozilla::Forward<Args>(args)...);
+ JS_FOR_EACH_TRACEKIND(JS_EXPAND_DEF);
+#undef JS_EXPAND_DEF
+ default:
+ MOZ_CRASH("Invalid trace kind in DispatchTraceKindTyped.");
+ }
+}
+
+} // namespace JS
+
+#endif // js_TraceKind_h