[Isolates] Add a preprocessor flag to guard using TLS for the global isolate....

src/isolate.h

 // Copyright 2010 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
@@ skipping 10 matching lines @@
 // 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.
 
 #ifndef V8_ISOLATE_H_
 #define V8_ISOLATE_H_
 
+// #define V8_USE_TLS_FOR_GLOBAL_ISOLATE
+
 #include "apiutils.h"
 #include "heap.h"
 #include "execution.h"
 #include "zone.h"
 
 namespace v8 {
 namespace internal {
 
 class Bootstrapper;
 class ContextSlotCache;
@@ skipping 104 matching lines @@
   /* A previously allocated buffer of kMinimalBufferSize bytes, or NULL. */    \
   V(byte*, assembler_spare_buffer, NULL)                                       \
   ISOLATE_PLATFORM_INIT_LIST(V)
 
 class Isolate {
  public:
   ~Isolate();
 
   // Returns the single global isolate.
   static Isolate* Current() {
-    ASSERT(global_isolate != NULL);
-    return global_isolate;
+#ifdef V8_USE_TLS_FOR_GLOBAL_ISOLATE
+    Isolate* isolate = reinterpret_cast<Isolate*>(
+        Thread::GetThreadLocal(global_isolate_key_));
+    if (isolate == NULL) {
+      isolate = InitThreadForGlobalIsolate();
+      ASSERT(isolate != NULL);
+    }
+    return isolate;
+#else
+    ASSERT(global_isolate_ != NULL);
+    return global_isolate_;
+#endif
   }
 
+#ifdef V8_USE_TLS_FOR_GLOBAL_ISOLATE
+  static Isolate* InitThreadForGlobalIsolate();
+#endif
+
   // Creates a new isolate (perhaps using a deserializer). Returns null
   // on failure.
   static Isolate* Create(Deserializer* des);
 
 #define GLOBAL_ACCESSOR(type, name, initialvalue)                              \
   type name() const { return name##_; }                                        \
   void set_##name(type value) { name##_ = value; }
   ISOLATE_INIT_LIST(GLOBAL_ACCESSOR)
 #undef GLOBAL_ACCESSOR
 
@@ skipping 40 matching lines @@
   Zone* zone() { return &zone_; }
 
   // SerializerDeserializer state.
   static const int kPartialSnapshotCacheCapacity = 1300;
 
   static int number_of_isolates() { return number_of_isolates_; }
 
  private:
   Isolate();
 
-  static Isolate* global_isolate;
+#ifdef V8_USE_TLS_FOR_GLOBAL_ISOLATE
+  static Thread::LocalStorageKey global_isolate_key_;
+#endif
+  static Isolate* global_isolate_;
+
   // TODO(isolates): Access to this global counter should be serialized.
   static int number_of_isolates_;
 
   // Initialize process-wide state.
   static void InitOnce();
 
   bool PreInit();
 
   bool Init(Deserializer* des);
 
@@ skipping 88 matching lines @@
 
 
 // Temporary macro to be used to flag classes that are completely converted
 // to be isolate-friendly. Their mix of static/nonstatic methods/fields is
 // correct.
 #define ISOLATED_CLASS class
 
 } }  // namespace v8::internal
 
 #endif  // V8_ISOLATE_H_