Some debugging support fixes on ARM simulator port....

src/top.h

 // Copyright 2006-2008 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 294 matching lines @@
 // versions of GCC. See V8 issue 122 for details.
 class SaveContext BASE_EMBEDDED {
  public:
   SaveContext() :
       context_(Top::context()),
 #if __GNUC_VERSION__ >= 40100 && __GNUC_VERSION__ < 40300
       dummy_(Top::context()),
 #endif
       prev_(Top::save_context()) {
     Top::set_save_context(this);
+
+    // If there is no JS frame under the current C frame, use the value 0.
+    JavaScriptFrameIterator it;
+    js_sp_ = it.done() ? 0 : it.frame()->sp();
   }
 
   ~SaveContext() {
     Top::set_context(*context_);
     Top::set_save_context(prev_);
   }
 
   Handle<Context> context() { return context_; }
   SaveContext* prev() { return prev_; }
 
+  // Returns true if this save context is below a given JavaScript frame.
+  bool below(JavaScriptFrame* frame) {
+    return (js_sp_ == 0) || (frame->sp() < js_sp_);
+  }
+
  private:
   Handle<Context> context_;
 #if __GNUC_VERSION__ >= 40100 && __GNUC_VERSION__ < 40300
   Handle<Context> dummy_;
 #endif
   SaveContext* prev_;
+  Address js_sp_;  // The top JS frame's sp when saving context.
 };
 
 
 class AssertNoContextChange BASE_EMBEDDED {
 #ifdef DEBUG
  public:
   AssertNoContextChange() :
       context_(Top::context()) {
   }
 
@@ skipping 13 matching lines @@
 
 class ExecutionAccess BASE_EMBEDDED {
  public:
   ExecutionAccess();
   ~ExecutionAccess();
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_TOP_H_