[interpreter, debugger] support debug breaks via bytecode array copy

src/interpreter/bytecode-generator.cc

 // Copyright 2015 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.
 
 #include "src/interpreter/bytecode-generator.h"
 
 #include "src/ast/scopes.h"
 #include "src/compiler.h"
 #include "src/interpreter/bytecode-register-allocator.h"
 #include "src/interpreter/control-flow-builders.h"
@@ skipping 880 matching lines @@
 }
 
 
 void BytecodeGenerator::VisitBreakStatement(BreakStatement* stmt) {
   execution_control()->Break(stmt->target());
 }
 
 
 void BytecodeGenerator::VisitReturnStatement(ReturnStatement* stmt) {
   VisitForAccumulatorValue(stmt->expression());
-  builder()->SetReturnPosition(info_->literal());
+  builder()->SetStatementPosition(stmt);

[Yang, 2016/02/16 09:22:20]

Turns out I've been wrong about setting the return position here before. This
here matches what FCG does.

[rmcilroy, 2016/02/16 10:46:38]

Ack. Note: we will only get a SetReturnPosition now where there is an implicit
return - just making sure this is what we want.

Should we make SetReturnPosition private to ensure we only set it on implicit
returns?

[Yang, 2016/02/19 13:09:17]

Done.

   execution_control()->ReturnAccumulator();
 }
 
 
 void BytecodeGenerator::VisitWithStatement(WithStatement* stmt) {
   VisitForAccumulatorValue(stmt->expression());
   builder()->CastAccumulatorToJSObject();
   VisitNewLocalWithContext();
   VisitInScope(stmt->statement(), stmt->scope());
 }
@@ skipping 2214 matching lines @@
 }
 
 
 int BytecodeGenerator::feedback_index(FeedbackVectorSlot slot) const {
   return info()->feedback_vector()->GetIndex(slot);
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8