[Interpreter] Fixes a bug when popping context to correct level on break/continue.

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"
 #include "src/objects.h"
 #include "src/parsing/parser.h"
 #include "src/parsing/token.h"
 
 namespace v8 {
 namespace internal {
 namespace interpreter {
 
 
 // Scoped class tracking context objects created by the visitor. Represents
 // mutations of the context chain within the function body, allowing pushing and
 // popping of the current {context_register} during visitation.
 class BytecodeGenerator::ContextScope BASE_EMBEDDED {
  public:
   ContextScope(BytecodeGenerator* generator, Scope* scope,
                bool should_pop_context = true)

[rmcilroy, 2016/03/08 07:34:37]

Now that we are popping more explicitly on return, and we drop dead code after a
return, the should_pop_context argument seems less useful - could you remove
this while you are here please?

[mythria, 2016/03/08 11:04:23]

Done.

       : generator_(generator),
         scope_(scope),
         outer_(generator_->execution_context()),
         register_(Register::current_context()),
         depth_(0),
         should_pop_context_(should_pop_context) {
     if (outer_) {
       depth_ = outer_->depth_ + 1;
 
       // Push the outer context into a new context register.
@@ skipping 318 matching lines @@
 
  private:
   TryFinallyBuilder* try_finally_builder_;
   DeferredCommands* commands_;
 };
 
 
 void BytecodeGenerator::ControlScope::PerformCommand(Command command,
                                                      Statement* statement) {
   ControlScope* current = this;
-  ContextScope* context = this->context();
+  ContextScope* context = generator()->execution_context();
   do {
-    if (current->Execute(command, statement)) { return; }
-    current = current->outer();
     if (current->context() != context) {
       // Pop context to the expected depth.
       // TODO(rmcilroy): Only emit a single context pop.
       generator()->builder()->PopContext(current->context()->reg());
       context = current->context();
     }
+    if (current->Execute(command, statement)) {
+      return;
+    }
+    current = current->outer();
   } while (current != nullptr);
   UNREACHABLE();
 }
 
 
 class BytecodeGenerator::RegisterAllocationScope {
  public:
   explicit RegisterAllocationScope(BytecodeGenerator* generator)
       : generator_(generator),
         outer_(generator->register_allocator()),
@@ skipping 2757 matching lines @@
 }
 
 
 int BytecodeGenerator::feedback_index(FeedbackVectorSlot slot) const {
   return info()->feedback_vector()->GetIndex(slot);
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8