Implements a new API to set a function entry hook for profiling.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index 77ffb385ab97f34381177e4a39e2f01aec62fa94..92cad9c38e2daf415564de317c35ea0e1669dd5e 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -3179,6 +3179,16 @@ class V8EXPORT V8 {
       ReturnAddressLocationResolver return_address_resolver);
 
   /**
+   * Allows the host application to provide the address of a function that's
+   * invoked on entry to every V8-generated function.
+   * Note that the entry_hook function is invoked at the very start of
+   * each generated function, before a stack frame is constructed, volatile
+   * registers saved etc. This function therefore must preserve all registers,
+   * and will likely need to be written in assembly.
+   */
+  static void SetFunctionEntryHook(uintptr_t entry_hook);

[danno, 2012/06/27 23:01:54]

I am not sure exactly what the right thing to do is, but it seems a bit fragile
that the call silently fails on x64 and ARM.

[Sigurður Ásgeirsson, 2012/06/28 09:41:41]

Good point. Another thing that occurred to me is that there's no way to "stack"
this API, e.g. it doesn't make sense to have multiple profilers active at the
same time.
How about having this function return bool, return true on success, and fail it
on unsupported platforms as well as on setting any transition except to and from
a NULL hook?

+
+  /**
    * 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