[Interpreter] Adds support to fetch return value on break at return.

src/debug/debug.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_DEBUG_DEBUG_H_
 #define V8_DEBUG_DEBUG_H_
 
 #include "src/allocation.h"
 #include "src/arguments.h"
 #include "src/assembler.h"
@@ skipping 506 matching lines @@
   inline bool is_loaded() const { return !debug_context_.is_null(); }
   inline bool in_debug_scope() const {
     return !!base::NoBarrier_Load(&thread_local_.current_debug_scope_);
   }
   void set_break_points_active(bool v) { break_points_active_ = v; }
   bool break_points_active() const { return break_points_active_; }
 
   StackFrame::Id break_frame_id() { return thread_local_.break_frame_id_; }
   int break_id() { return thread_local_.break_id_; }
 
+  Handle<Object> get_return_value() { return thread_local_.return_value_; }
+
   // Support for embedding into generated code.
   Address is_active_address() {
     return reinterpret_cast<Address>(&is_active_);
   }
 
   Address after_break_target_address() {
     return reinterpret_cast<Address>(&after_break_target_);
   }
 
   Address step_in_enabled_address() {
@@ skipping 134 matching lines @@
     Address target_fp_;
 
     // Whether functions are flooded on entry for step-in and step-frame.
     // If we stepped out to the embedder, disable flooding to spill stepping
     // to the next call that the embedder makes.
     bool step_in_enabled_;
 
     // Stores the way how LiveEdit has patched the stack. It is used when
     // debugger returns control back to user script.
     LiveEdit::FrameDropMode frame_drop_mode_;
+
+    // Value of accumulator in interpreter frames. In non-interpreter frames
+    // this value will be a hole.

[rmcilroy, 2016/03/22 11:32:34]

/s/a hole/the hole/

[mythria, 2016/03/22 12:08:09]

Done.

+    Handle<Object> return_value_;
   };
 
   // Storage location for registers when handling debug break calls
   ThreadLocal thread_local_;
 
   Isolate* isolate_;
 
   friend class Isolate;
   friend class DebugScope;
   friend class DisableBreak;
@@ skipping 21 matching lines @@
   // Get the active context from before entering the debugger.
   inline Handle<Context> GetContext() { return save_.context(); }
 
  private:
   Isolate* isolate() { return debug_->isolate_; }
 
   Debug* debug_;
   DebugScope* prev_;               // Previous scope if entered recursively.
   StackFrame::Id break_frame_id_;  // Previous break frame id.
   int break_id_;                   // Previous break id.
+  Handle<Object> return_value_;    // Previous result.
   bool failed_;                    // Did the debug context fail to load?
   SaveContext save_;               // Saves previous context.
   PostponeInterruptsScope no_termination_exceptons_;
 };
 
 
 // Stack allocated class for disabling break.
 class DisableBreak BASE_EMBEDDED {
  public:
   explicit DisableBreak(Debug* debug, bool disable_break)
@@ skipping 55 matching lines @@
                                   Handle<Code> code);
   static bool DebugBreakSlotIsPatched(Address pc);
   static void ClearDebugBreakSlot(Isolate* isolate, Address pc);
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_DEBUG_DEBUG_H_