Add a new API V8::SetJitCodeEventHandler to push code name and location to users such as profilers.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index 5c2c8b6671827f56ddddb6ef4a71182b6d54c164..f25347d4dc3a7255139cfe0854085cd9ff235fa9 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -2944,6 +2944,40 @@ typedef void (*FunctionEntryHook)(uintptr_t function,
 
 
 /**
+ * A JIT code event is issued each time code is added, moved or removed.
+ *
+ * \note removal events are not currently issued.
+ */
+struct JitCodeEvent {
+  enum EventType {
+    CODE_ADDED,
+    CODE_MOVED,
+    CODE_REMOVED
+  };
+
+  EventType type;
+  // Start of the instructions.
+  void* code_start;
+  // Size of the instructions.
+  size_t code_len;
+  union {
+    // Name of the object associated with the code. Only valid for CODE_ADDED.
+    const char* name;
+    // New location of instructions. Only valid for CODE_MOVED.
+    void* new_code_start;
+  };
+};
+
+
+/**
+ * Callback function passed to SetJitCodeEventHandler.
+ *
+ * \param event code add, move or removal event.
+ */
+typedef void (*JitCodeEventHandler)(const JitCodeEvent* event);
+
+
+/**
  * Interface for iterating though all external resources in the heap.
  */
 class V8EXPORT ExternalResourceVisitor {  // NOLINT
@@ -3218,6 +3252,16 @@ class V8EXPORT V8 {
   static bool SetFunctionEntryHook(FunctionEntryHook entry_hook);
 
   /**
+   * Allows the host application to provide the address of a function that is
+   * notified each time code is added, moved or removed.
+   *
+   * \param event_handler the JIT code event handler, which will be invoked
+   *     each time code is added, moved or removed.
+   * \note \p event_handler won't get notified of existent code.

[mnaganov (inactive), 2012/07/30 11:43:36]

One more thing worth mentioning here -- because of missing code deletion events,
it will be possible for code addition events to arrive having code addresses
that overlap with previously added code objects. The client needs to delete all
overlapping code objects first, as they were in fact removed during GC.

Sorry I forgot about this issue initially.

[Sigurður Ásgeirsson, 2012/07/30 13:54:43]

Thanks! Added docs regarding overlap and string/event lifetimes.

+   */
+  static void SetJitCodeEventHandler(JitCodeEventHandler event_handler);
+
+  /**
    * Adjusts the amount of registered external memory.  Used to give
    * V8 an indication of the amount of externally allocated memory
    * that is kept alive by JavaScript objects.  V8 uses this to decide