[interpreter] Clear pending message object on handler entry.

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 1089 matching lines @@
 
   VisitForEffect(stmt->assign_each());
   Visit(stmt->body());
   loop_builder.JumpToHeader();
   loop_builder.EndLoop();
 }
 
 
 void BytecodeGenerator::VisitTryCatchStatement(TryCatchStatement* stmt) {
   TryCatchBuilder try_control_builder(builder());
+  Register no_reg;
 
   // Preserve the context in a dedicated register, so that it can be restored
   // when the handler is entered by the stack-unwinding machinery.
   // TODO(mstarzinger): Be smarter about register allocation.
   Register context = register_allocator()->NewRegister();
 
   // Evaluate the try-block inside a control scope. This simulates a handler
   // that is intercepting 'throw' control commands.
   try_control_builder.BeginTry(context);
   {
     ControlScopeForTryCatch scope(this, &try_control_builder);
     Visit(stmt->try_block());
   }
   try_control_builder.EndTry();
 
-  // Clear message object as we enter the catch block.
-  // TODO(mstarzinger): Implement this!
-
   // Create a catch scope that binds the exception.
   VisitNewLocalCatchContext(stmt->variable());
+  builder()->StoreAccumulatorInRegister(context);
+
+  // Clear message object as we enter the catch block.
+  builder()->CallRuntime(Runtime::kInterpreterClearPendingMessage, no_reg, 0);
+
+  // Load the catch context into the accumulator.
+  builder()->LoadAccumulatorWithRegister(context);
 
   // Evaluate the catch-block.
   VisitInScope(stmt->catch_block(), stmt->scope());
   try_control_builder.EndCatch();
 }
 
 
 void BytecodeGenerator::VisitTryFinallyStatement(TryFinallyStatement* stmt) {
   TryFinallyBuilder try_control_builder(builder());
+  Register no_reg;
 
   // We keep a record of all paths that enter the finally-block to be able to
   // dispatch to the correct continuation point after the statements in the
   // finally-block have been evaluated.
   //
   // The try-finally construct can enter the finally-block in three ways:
   // 1. By exiting the try-block normally, falling through at the end.
   // 2. By exiting the try-block with a function-local control flow transfer
   //    (i.e. through break/continue/return statements).
   // 3. By exiting the try-block with a thrown exception.
@@ skipping 20 matching lines @@
     Visit(stmt->try_block());
   }
   try_control_builder.EndTry();
 
   // Record fall-through and exception cases.
   commands.RecordFallThroughPath();
   try_control_builder.LeaveTry();
   try_control_builder.BeginHandler();
   commands.RecordHandlerReThrowPath();
 
+  // Pending message object is saved on entry.
   try_control_builder.BeginFinally();
+  Register message = context;  // Reuse register.
+  builder()
+      ->CallRuntime(Runtime::kInterpreterGetPendingMessage, no_reg, 0)
+      .StoreAccumulatorInRegister(message);
 
   // Clear message object as we enter the finally block.
-  // TODO(mstarzinger): Implement this!
+  builder()->CallRuntime(Runtime::kInterpreterClearPendingMessage, no_reg, 0);

[rmcilroy, 2016/02/01 20:57:14]

Could we make InterpreterGetPendingMessage also clear the pending message to
avoid having to make two runtime calls in quick succession?

[Michael Starzinger, 2016/02/02 09:41:43]

Done. I made kInterpreterClearPendingMessage return the original message.

 
   // Evaluate the finally-block.
   Visit(stmt->finally_block());
   try_control_builder.EndFinally();
 
+  // Pending message object is restored on exit.
+  builder()->CallRuntime(Runtime::kInterpreterSetPendingMessage, message, 1);
+
   // Dynamic dispatch after the finally-block.
   commands.ApplyDeferredCommands();
 }
 
 
 void BytecodeGenerator::VisitDebuggerStatement(DebuggerStatement* stmt) {
   UNIMPLEMENTED();
 }
 
 
@@ skipping 1308 matching lines @@
 }
 
 
 int BytecodeGenerator::feedback_index(FeedbackVectorSlot slot) const {
   return info()->feedback_vector()->GetIndex(slot);
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8