[interpreter] Clear pending message object on handler entry.

This clears the currently pending message object whenever a try-block or
a finally-block is being entered in interpreted code. The intention is
to avoid memory leaks introduced by the message object. Also the message
object is being restored when a finally-block exits.

R=rmcilroy@chromium.org
TEST=cctest/test-heap/MessageObjectLeak
BUG=v8:4674
LOG=n

Review URL: https://codereview.chromium.org/1651993002

Cr-Commit-Position: refs/heads/master@{#33704}

src/interpreter/bytecode-generator.cc

@@ -1108,6 +1108,7 @@ void BytecodeGenerator::VisitForOfStatement(ForOfStatement* stmt) {
 
 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.
@@ -1123,11 +1124,15 @@ void BytecodeGenerator::VisitTryCatchStatement(TryCatchStatement* stmt) {
   }
   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());
@@ -1137,6 +1142,7 @@ void BytecodeGenerator::VisitTryCatchStatement(TryCatchStatement* stmt) {
 
 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
@@ -1177,15 +1183,22 @@ void BytecodeGenerator::VisitTryFinallyStatement(TryFinallyStatement* stmt) {
   try_control_builder.BeginHandler();
   commands.RecordHandlerReThrowPath();
 
+  // Pending message object is saved on entry.
   try_control_builder.BeginFinally();
+  Register message = context;  // Reuse register.
 
   // Clear message object as we enter the finally block.
-  // TODO(mstarzinger): Implement this!
+  builder()
+      ->CallRuntime(Runtime::kInterpreterClearPendingMessage, no_reg, 0)
+      .StoreAccumulatorInRegister(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();
 }

src/runtime/runtime-interpreter.cc

@@ -253,5 +253,21 @@ RUNTIME_FUNCTION(Runtime_InterpreterTraceBytecodeExit) {
   return isolate->heap()->undefined_value();
 }
 
+RUNTIME_FUNCTION(Runtime_InterpreterClearPendingMessage) {
+  SealHandleScope shs(isolate);
+  DCHECK_EQ(0, args.length());
+  Object* message = isolate->thread_local_top()->pending_message_obj_;
+  isolate->clear_pending_message();
+  return message;
+}
+
+RUNTIME_FUNCTION(Runtime_InterpreterSetPendingMessage) {
+  SealHandleScope shs(isolate);
+  DCHECK_EQ(1, args.length());
+  CONVERT_ARG_HANDLE_CHECKED(Object, message, 0);
+  isolate->thread_local_top()->pending_message_obj_ = *message;
+  return isolate->heap()->undefined_value();
+}
+
 }  // namespace internal
 }  // namespace v8

src/runtime/runtime.h

@@ -221,7 +221,9 @@ namespace internal {
   F(InterpreterTypeOf, 1, 1)              \
   F(InterpreterNewClosure, 2, 1)          \
   F(InterpreterTraceBytecodeEntry, 3, 1)  \
-  F(InterpreterTraceBytecodeExit, 3, 1)
+  F(InterpreterTraceBytecodeExit, 3, 1)   \
+  F(InterpreterClearPendingMessage, 0, 1) \
+  F(InterpreterSetPendingMessage, 1, 1)
 
 #define FOR_EACH_INTRINSIC_FUNCTION(F)     \
   F(FunctionGetName, 1, 1)                 \

test/cctest/cctest.status

@@ -513,11 +513,8 @@
   'test-profile-generator/BailoutReason': [FAIL],
   'test-api/Regress385349': [FAIL],
 
-  # TODO(mstarzinger,4674): Message object is not properly cleared.
-  'test-heap/MessageObjectLeak': [FAIL],
-
   # TODO(mstarzinger,4674): Support exception handlers in BytecodeGraphBuilder.
-  'test-run-deopt/DeoptExceptionHandlerCatch': [FAIL],
+  'test-run-deopt/DeoptExceptionHandlerCatch': [PASS, FAIL],
 
   # TODO(rmcilroy,4680): Check failed: toplevel_test_code_event_found.
   'test-serialize/SerializeToplevelIsolates': [FAIL],