[Interpreter] Implement do expressions.

test/cctest/interpreter/test-interpreter.cc

Index: test/cctest/interpreter/test-interpreter.cc
diff --git a/test/cctest/interpreter/test-interpreter.cc b/test/cctest/interpreter/test-interpreter.cc
index e4e546ae83c735a16d41c5f4af5cce945cc8b830..ded815b9557d3eee63b850148db26e75a14bff49 100644
--- a/test/cctest/interpreter/test-interpreter.cc
+++ b/test/cctest/interpreter/test-interpreter.cc
@@ -3825,6 +3825,37 @@ TEST(InterpreterWideParametersSummation) {
 
 // TODO(oth): Test for..in with wide registers.
 
+TEST(InterpreterDoExpression) {
+  bool old_flag = FLAG_harmony_do_expressions;
+  FLAG_harmony_do_expressions = true;
+
+  HandleAndZoneScope handles;
+  i::Isolate* isolate = handles.main_isolate();
+  Factory* factory = isolate->factory();
+
+  std::pair<const char*, Handle<Object>> do_expr[] = {
+      {"var a = do {}; return a;", factory->undefined_value()},
+      {"var a = do { var x = 100; }; return a;", factory->undefined_value()},
+      {"var a = do { var x = 100; }; return a;", factory->undefined_value()},
+      {"var a = do { var x = 100; x++; }; return a;",
+       handle(Smi::FromInt(100), isolate)},
+      {"var i = 0; for (; i < 5;) { i = do { if (i == 3) { break; }; i + 1; }};"
+       "return i;",
+       handle(Smi::FromInt(3), isolate)},
+  };
+
+  for (size_t i = 0; i < arraysize(do_expr); i++) {
+    std::string source(InterpreterTester::SourceForBody(do_expr[i].first));
+    InterpreterTester tester(handles.main_isolate(), source.c_str());
+    auto callable = tester.GetCallable<>();
+
+    Handle<i::Object> return_value = callable().ToHandleChecked();
+    CHECK(return_value->SameValue(*do_expr[i].second));
+  }
+
+  FLAG_harmony_do_expressions = old_flag;
+}
+
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8