Merge V8 at 3.9.24.13
Bug: 5688872
Change-Id: Id0aa8d23375030494d3189c31774059c0f5398fc
diff --git a/src/lazy-instance.h b/src/lazy-instance.h
new file mode 100644
index 0000000..d0893e5
--- /dev/null
+++ b/src/lazy-instance.h
@@ -0,0 +1,259 @@
+// Copyright 2012 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+// * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following
+// disclaimer in the documentation and/or other materials provided
+// with the distribution.
+// * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived
+// from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// The LazyInstance<Type, Traits> class manages a single instance of Type,
+// which will be lazily created on the first time it's accessed. This class is
+// useful for places you would normally use a function-level static, but you
+// need to have guaranteed thread-safety. The Type constructor will only ever
+// be called once, even if two threads are racing to create the object. Get()
+// and Pointer() will always return the same, completely initialized instance.
+//
+// LazyInstance is completely thread safe, assuming that you create it safely.
+// The class was designed to be POD initialized, so it shouldn't require a
+// static constructor. It really only makes sense to declare a LazyInstance as
+// a global variable using the LAZY_INSTANCE_INITIALIZER initializer.
+//
+// LazyInstance is similar to Singleton, except it does not have the singleton
+// property. You can have multiple LazyInstance's of the same type, and each
+// will manage a unique instance. It also preallocates the space for Type, as
+// to avoid allocating the Type instance on the heap. This may help with the
+// performance of creating the instance, and reducing heap fragmentation. This
+// requires that Type be a complete type so we can determine the size. See
+// notes for advanced users below for more explanations.
+//
+// Example usage:
+// static LazyInstance<MyClass>::type my_instance = LAZY_INSTANCE_INITIALIZER;
+// void SomeMethod() {
+// my_instance.Get().SomeMethod(); // MyClass::SomeMethod()
+//
+// MyClass* ptr = my_instance.Pointer();
+// ptr->DoDoDo(); // MyClass::DoDoDo
+// }
+//
+// Additionally you can override the way your instance is constructed by
+// providing your own trait:
+// Example usage:
+// struct MyCreateTrait {
+// static void Construct(MyClass* allocated_ptr) {
+// new (allocated_ptr) MyClass(/* extra parameters... */);
+// }
+// };
+// static LazyInstance<MyClass, MyCreateTrait>::type my_instance =
+// LAZY_INSTANCE_INITIALIZER;
+//
+// WARNING: This implementation of LazyInstance is NOT thread-safe by default.
+// See ThreadSafeInitOnceTrait declared below for that.
+//
+// Notes for advanced users:
+// LazyInstance can actually be used in two different ways:
+//
+// - "Static mode" which is the default mode since it is the most efficient
+// (no extra heap allocation). In this mode, the instance is statically
+// allocated (stored in the global data section at compile time).
+// The macro LAZY_STATIC_INSTANCE_INITIALIZER (= LAZY_INSTANCE_INITIALIZER)
+// must be used to initialize static lazy instances.
+//
+// - "Dynamic mode". In this mode, the instance is dynamically allocated and
+// constructed (using new) by default. This mode is useful if you have to
+// deal with some code already allocating the instance for you (e.g.
+// OS::Mutex() which returns a new private OS-dependent subclass of Mutex).
+// The macro LAZY_DYNAMIC_INSTANCE_INITIALIZER must be used to initialize
+// dynamic lazy instances.
+
+#ifndef V8_LAZY_INSTANCE_H_
+#define V8_LAZY_INSTANCE_H_
+
+#include "once.h"
+
+namespace v8 {
+namespace internal {
+
+#define LAZY_STATIC_INSTANCE_INITIALIZER { V8_ONCE_INIT, {} }
+#define LAZY_DYNAMIC_INSTANCE_INITIALIZER { V8_ONCE_INIT, 0 }
+
+// Default to static mode.
+#define LAZY_INSTANCE_INITIALIZER LAZY_STATIC_INSTANCE_INITIALIZER
+
+
+template <typename T>
+struct LeakyInstanceTrait {
+ static void Destroy(T* /* instance */) {}
+};
+
+
+// Traits that define how an instance is allocated and accessed.
+
+// TODO(kalmard): __alignof__ is only defined for GCC > 4.2. Fix alignment issue
+// on MIPS with other compilers.
+#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ > 2))
+#define LAZY_ALIGN(x) __attribute__((aligned(__alignof__(x))))
+#else
+#define LAZY_ALIGN(x)
+#endif
+
+template <typename T>
+struct StaticallyAllocatedInstanceTrait {
+ typedef char StorageType[sizeof(T)] LAZY_ALIGN(T);
+
+ static T* MutableInstance(StorageType* storage) {
+ return reinterpret_cast<T*>(storage);
+ }
+
+ template <typename ConstructTrait>
+ static void InitStorageUsingTrait(StorageType* storage) {
+ ConstructTrait::Construct(MutableInstance(storage));
+ }
+};
+
+#undef LAZY_ALIGN
+
+
+template <typename T>
+struct DynamicallyAllocatedInstanceTrait {
+ typedef T* StorageType;
+
+ static T* MutableInstance(StorageType* storage) {
+ return *storage;
+ }
+
+ template <typename CreateTrait>
+ static void InitStorageUsingTrait(StorageType* storage) {
+ *storage = CreateTrait::Create();
+ }
+};
+
+
+template <typename T>
+struct DefaultConstructTrait {
+ // Constructs the provided object which was already allocated.
+ static void Construct(T* allocated_ptr) {
+ new(allocated_ptr) T();
+ }
+};
+
+
+template <typename T>
+struct DefaultCreateTrait {
+ static T* Create() {
+ return new T();
+ }
+};
+
+
+struct ThreadSafeInitOnceTrait {
+ template <typename Function, typename Storage>
+ static void Init(OnceType* once, Function function, Storage storage) {
+ CallOnce(once, function, storage);
+ }
+};
+
+
+// Initialization trait for users who don't care about thread-safety.
+struct SingleThreadInitOnceTrait {
+ template <typename Function, typename Storage>
+ static void Init(OnceType* once, Function function, Storage storage) {
+ if (*once == ONCE_STATE_UNINITIALIZED) {
+ function(storage);
+ *once = ONCE_STATE_DONE;
+ }
+ }
+};
+
+
+// TODO(pliard): Handle instances destruction (using global destructors).
+template <typename T, typename AllocationTrait, typename CreateTrait,
+ typename InitOnceTrait, typename DestroyTrait /* not used yet. */>
+struct LazyInstanceImpl {
+ public:
+ typedef typename AllocationTrait::StorageType StorageType;
+
+ private:
+ static void InitInstance(StorageType* storage) {
+ AllocationTrait::template InitStorageUsingTrait<CreateTrait>(storage);
+ }
+
+ void Init() const {
+ InitOnceTrait::Init(
+ &once_,
+ // Casts to void* are needed here to avoid breaking strict aliasing
+ // rules.
+ reinterpret_cast<void(*)(void*)>(&InitInstance), // NOLINT
+ reinterpret_cast<void*>(&storage_));
+ }
+
+ public:
+ T* Pointer() {
+ Init();
+ return AllocationTrait::MutableInstance(&storage_);
+ }
+
+ const T& Get() const {
+ Init();
+ return *AllocationTrait::MutableInstance(&storage_);
+ }
+
+ mutable OnceType once_;
+ // Note that the previous field, OnceType, is an AtomicWord which guarantees
+ // 4-byte alignment of the storage field below. If compiling with GCC (>4.2),
+ // the LAZY_ALIGN macro above will guarantee correctness for any alignment.
+ mutable StorageType storage_;
+};
+
+
+template <typename T,
+ typename CreateTrait = DefaultConstructTrait<T>,
+ typename InitOnceTrait = SingleThreadInitOnceTrait,
+ typename DestroyTrait = LeakyInstanceTrait<T> >
+struct LazyStaticInstance {
+ typedef LazyInstanceImpl<T, StaticallyAllocatedInstanceTrait<T>,
+ CreateTrait, InitOnceTrait, DestroyTrait> type;
+};
+
+
+template <typename T,
+ typename CreateTrait = DefaultConstructTrait<T>,
+ typename InitOnceTrait = SingleThreadInitOnceTrait,
+ typename DestroyTrait = LeakyInstanceTrait<T> >
+struct LazyInstance {
+ // A LazyInstance is a LazyStaticInstance.
+ typedef typename LazyStaticInstance<T, CreateTrait, InitOnceTrait,
+ DestroyTrait>::type type;
+};
+
+
+template <typename T,
+ typename CreateTrait = DefaultConstructTrait<T>,
+ typename InitOnceTrait = SingleThreadInitOnceTrait,
+ typename DestroyTrait = LeakyInstanceTrait<T> >
+struct LazyDynamicInstance {
+ typedef LazyInstanceImpl<T, DynamicallyAllocatedInstanceTrait<T>,
+ CreateTrait, InitOnceTrait, DestroyTrait> type;
+};
+
+} } // namespace v8::internal
+
+#endif // V8_LAZY_INSTANCE_H_