[Interpreter] Ensure context is popped when we break or continue

src/interpreter/bytecode-generator.cc

Index: src/interpreter/bytecode-generator.cc
diff --git a/src/interpreter/bytecode-generator.cc b/src/interpreter/bytecode-generator.cc
index 6e94b5f0791182803076d8dbb550f1dfec075652..5bbc3819ad613b5b38e4081eefc05449b5780d78 100644
--- a/src/interpreter/bytecode-generator.cc
+++ b/src/interpreter/bytecode-generator.cc
@@ -81,7 +81,8 @@ class BytecodeGenerator::ContextScope BASE_EMBEDDED {
 class BytecodeGenerator::ControlScope BASE_EMBEDDED {
  public:
   explicit ControlScope(BytecodeGenerator* generator)
-      : generator_(generator), outer_(generator->execution_control()) {
+      : generator_(generator), outer_(generator->execution_control()),
+        context_(generator->execution_context()) {
     generator_->set_execution_control(this);
   }
   virtual ~ControlScope() { generator_->set_execution_control(outer()); }
@@ -92,14 +93,17 @@ class BytecodeGenerator::ControlScope BASE_EMBEDDED {
  protected:
   enum Command { CMD_BREAK, CMD_CONTINUE };
   void PerformCommand(Command command, Statement* statement);
-  virtual bool Execute(Command command, Statement* statement) = 0;
+  virtual bool ShouldExecute(Command command, Statement* statement) = 0;
+  virtual void Execute(Command command) = 0;
 
   BytecodeGenerator* generator() const { return generator_; }
   ControlScope* outer() const { return outer_; }
+  ContextScope* context() const { return context_; }
 
  private:
   BytecodeGenerator* generator_;
   ControlScope* outer_;
+  ContextScope* context_;
 
   DISALLOW_COPY_AND_ASSIGN(ControlScope);
 };
@@ -117,16 +121,20 @@ class BytecodeGenerator::ControlScopeForBreakable final
         control_builder_(control_builder) {}
 
  protected:
-  virtual bool Execute(Command command, Statement* statement) {
+  bool ShouldExecute(Command command, Statement* statement) override {
     if (statement != statement_) return false;
+    return command == CMD_BREAK;
+  }
+
+  void Execute(Command command) override {
     switch (command) {
       case CMD_BREAK:
         control_builder_->Break();
-        return true;
+        break;
       case CMD_CONTINUE:
+        UNREACHABLE();
         break;
     }
-    return false;
   }
 
  private:
@@ -148,17 +156,20 @@ class BytecodeGenerator::ControlScopeForIteration final
         loop_builder_(loop_builder) {}
 
  protected:
-  virtual bool Execute(Command command, Statement* statement) {
+  bool ShouldExecute(Command command, Statement* statement) override {
     if (statement != statement_) return false;
+    return command == CMD_BREAK || command == CMD_CONTINUE;
+  }
+
+  void Execute(Command command) override {
     switch (command) {
       case CMD_BREAK:
         loop_builder_->Break();
-        return true;
+        break;
       case CMD_CONTINUE:
         loop_builder_->Continue();
-        return true;
+        break;
     }
-    return false;
   }
 
  private:
@@ -171,7 +182,14 @@ void BytecodeGenerator::ControlScope::PerformCommand(Command command,
                                                      Statement* statement) {
   ControlScope* current = this;
   do {
-    if (current->Execute(command, statement)) return;
+    if (current->ShouldExecute(command, statement)) {

[Michael Starzinger, 2016/01/21 13:25:20]

As discussed offline: How would you feel about going for the sub-optimal
solution of potential popping a context for every control scope first? That way
the implementation of the various control scopes stays simple while we hack on
them. We can certainly leave a TODO in that regard. Once we got them all done we
can revisit how to optimize away the redundant pops. WDYT?

[rmcilroy, 2016/01/22 11:46:08]

Done.

+      if (current->context() != this->context()) {
+        // Pop context to the expected depth.
+        generator()->builder()->PopContext(current->context()->reg());
+      }
+      current->Execute(command);
+      return;
+    }
     current = current->outer();
   } while (current != nullptr);
   UNREACHABLE();