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

src/code-stubs.h

 // 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
@@ skipping 55 matching lines @@
   V(ArgumentsAccess)                     \
   V(RegExpConstructResult)               \
   V(NumberToString)                      \
   V(CEntry)                              \
   V(JSEntry)                             \
   V(KeyedLoadElement)                    \
   V(KeyedStoreElement)                   \
   V(DebuggerStatement)                   \
   V(StringDictionaryLookup)              \
   V(ElementsTransitionAndStore)          \
-  V(StoreArrayLiteralElement)
+  V(StoreArrayLiteralElement)            \
+  V(ProfileEntryHook)
 
 // List of code stubs only used on ARM platforms.
 #ifdef V8_TARGET_ARCH_ARM
 #define CODE_STUB_LIST_ARM(V)  \
   V(GetProperty)               \
   V(SetProperty)               \
   V(InvokeBuiltin)             \
   V(RegExpCEntry)              \
   V(DirectCEntry)
 #else
@@ skipping 1048 matching lines @@
 
  private:
   Major MajorKey() { return StoreArrayLiteralElement; }
   int MinorKey() { return 0; }
 
   void Generate(MacroAssembler* masm);
 
   DISALLOW_COPY_AND_ASSIGN(StoreArrayLiteralElementStub);
 };
 
+
+class ProfileEntryHookStub : public CodeStub {
+ public:
+  explicit ProfileEntryHookStub() {}
+
+  // The profile entry hook function is not allowed to cause a GC.
+  virtual bool SometimesSetsUpAFrame() { return false; }
+
+  // Generates a call to the entry hook if it's enabled.
+  static void MaybeCallEntryHook(MacroAssembler* masm);
+
+  // Sets or unsets the entry hook function. Returns true on success,
+  // false on an attempt to replace a non-NULL entry hook with another
+  // non-NULL hook.
+  static bool SetFunctionEntryHook(FunctionEntryHook entry_hook);
+
+ private:
+  static void EntryHookTrampoline(intptr_t function,
+                                  intptr_t stack_pointer);
+
+  Major MajorKey() { return ProfileEntryHook; }
+  int MinorKey() { return 0; }
+
+  void Generate(MacroAssembler* masm);
+
+  // The current function entry hook.
+  static FunctionEntryHook entry_hook_;
+
+  DISALLOW_COPY_AND_ASSIGN(ProfileEntryHookStub);
+};
+
 } }  // namespace v8::internal
 
 #endif  // V8_CODE_STUBS_H_