[Interpreter] Add support for VisitThisFunction.

BUG=v8:4280
LOG=N

Review URL: https://codereview.chromium.org/1406253008

Cr-Commit-Position: refs/heads/master@{#31859}

src/interpreter/bytecode-generator.cc

@@ -1869,7 +1869,7 @@ void BytecodeGenerator::VisitEmptyParentheses(EmptyParentheses* expr) {
 
 
 void BytecodeGenerator::VisitThisFunction(ThisFunction* expr) {
-  UNIMPLEMENTED();
+  execution_result()->SetResultInRegister(Register::function_closure());
 }
 
 

test/cctest/interpreter/test-bytecode-generator.cc

@@ -5147,6 +5147,47 @@ TEST(DeadCodeRemoval) {
   }
 }
 
+
+TEST(ThisFunction) {
+  InitializedHandleScope handle_scope;
+  BytecodeGeneratorHelper helper;
+
+  int closure = Register::function_closure().index();
+
+  ExpectedSnippet<int> snippets[] = {
+      {"var f;\n f = function f() { }",
+       1 * kPointerSize,
+       1,
+       9,
+       {
+           B(LdaTheHole),        //
+           B(Star), R(0),        //
+           B(Ldar), R(closure),  //
+           B(Star), R(0),        //
+           B(LdaUndefined),      //
+           B(Return),            //
+       }},
+      {"var f;\n f = function f() { return f; }",
+       1 * kPointerSize,
+       1,
+       10,
+       {
+           B(LdaTheHole),        //
+           B(Star), R(0),        //
+           B(Ldar), R(closure),  //
+           B(Star), R(0),        //
+           B(Ldar), R(0),        //
+           B(Return),            //
+       }},
+  };
+
+  for (size_t i = 0; i < arraysize(snippets); i++) {
+    Handle<BytecodeArray> bytecode_array =
+        helper.MakeBytecodeForFunction(snippets[i].code_snippet);
+    CheckBytecodeArrayEqual(snippets[i], bytecode_array);
+  }
+}
+
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8

test/cctest/interpreter/test-interpreter.cc

@@ -2919,6 +2919,20 @@ TEST(InterpreterSloppyThis) {
   }
 }
 
+
+TEST(InterpreterThisFunction) {
+  HandleAndZoneScope handles;
+  i::Isolate* isolate = handles.main_isolate();
+  i::Factory* factory = isolate->factory();
+
+  InterpreterTester tester(handles.main_isolate(),
+                           "var f;\n f = function f() { return f.name; }");
+  auto callable = tester.GetCallable<>();
+
+  Handle<i::Object> return_value = callable().ToHandleChecked();
+  CHECK(return_value->SameValue(*factory->NewStringFromStaticChars("f")));
+}
+
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8