[ESnext] Implement Promise.prototype.finally

src/bootstrapper.cc

 // Copyright 2014 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/bootstrapper.h"
 
 #include "src/accessors.h"
 #include "src/api-natives.h"
 #include "src/base/ieee754.h"
 #include "src/code-stubs.h"
@@ skipping 3606 matching lines @@
                         NONE);
 }
 
 void Genesis::InitializeGlobal_harmony_async_iteration() {
   if (!FLAG_harmony_async_iteration) return;
   Handle<JSFunction> symbol_fun(native_context()->symbol_function());
   InstallConstant(isolate(), symbol_fun, "asyncIterator",
                   factory()->async_iterator_symbol());
 }
 
+void Genesis::InitializeGlobal_harmony_promise_finally() {
+  if (!FLAG_harmony_promise_finally) return;
+
+  Handle<JSFunction> constructor(native_context()->promise_function());
+  Handle<JSObject> prototype(JSObject::cast(constructor->instance_prototype()));
+  SimpleInstallFunction(prototype, "finally", Builtins::kPromiseFinally, 1,
+                        true, DONT_ENUM);
+
+  // The promise prototype map has changed because we added a property
+  // to prototype, so we update the saved map.
+  Handle<Map> prototype_map(prototype->map());
+  Map::SetShouldBeFastPrototypeMap(prototype_map, true, isolate());
+  native_context()->set_promise_prototype_map(*prototype_map);
+
+  Handle<Code> code = handle(
+      isolate()->builtins()->builtin(Builtins::kPromiseThenFinally), isolate());
+  Handle<SharedFunctionInfo> info =
+      factory()->NewSharedFunctionInfo(factory()->empty_string(), code, false);
+  info->set_internal_formal_parameter_count(1);
+  info->set_length(1);
+  native_context()->set_promise_then_finally_shared_fun(*info);

[neis, 2017/02/15 12:40:39]

Nit: put this block in { }.  Same below.

Should we mark (some of) these SFIs as native?

[gsathya, 2017/02/16 15:05:29]

Why?
PromiseThenFinally and PromiseCatchFinally call userland js, so marking them as
native.

[neis, 2017/02/17 10:22:54]

I find it easier to read if it's immediately clear that code and info are local
to each block.

[gsathya, 2017/02/17 11:26:15]

Ok. I made each SFI creation its own block

+
+  code = handle(isolate()->builtins()->builtin(Builtins::kPromiseCatchFinally),
+                isolate());
+  info =
+      factory()->NewSharedFunctionInfo(factory()->empty_string(), code, false);
+  info->set_internal_formal_parameter_count(1);
+  info->set_length(1);
+  native_context()->set_promise_catch_finally_shared_fun(*info);
+
+  code = handle(
+      isolate()->builtins()->builtin(Builtins::kPromiseValueThunkFinally),
+      isolate());
+  info =
+      factory()->NewSharedFunctionInfo(factory()->empty_string(), code, false);
+  info->set_internal_formal_parameter_count(0);
+  info->set_length(0);
+  native_context()->set_promise_value_thunk_finally_shared_fun(*info);
+
+  code =
+      handle(isolate()->builtins()->builtin(Builtins::kPromiseThrowerFinally),
+             isolate());
+  info =
+      factory()->NewSharedFunctionInfo(factory()->empty_string(), code, false);
+  info->set_internal_formal_parameter_count(0);
+  info->set_length(0);
+  native_context()->set_promise_thrower_finally_shared_fun(*info);
+}
+
 Handle<JSFunction> Genesis::InstallArrayBuffer(Handle<JSObject> target,
                                                const char* name,
                                                Builtins::Name call,
                                                BuiltinFunctionId id) {
   // Create the %ArrayBufferPrototype%
   // Setup the {prototype} with the given {name} for @@toStringTag.
   Handle<JSObject> prototype =
       factory()->NewJSObject(isolate()->object_function(), TENURED);
   JSObject::AddProperty(prototype, factory()->to_string_tag_symbol(),
                         factory()->NewStringFromAsciiChecked(name),
@@ skipping 446 matching lines @@
                                                    nullptr};
   static const char* datetime_format_to_parts_natives[] = {
       "native datetime-format-to-parts.js", nullptr};
 #endif
   static const char* harmony_restrictive_generators_natives[] = {nullptr};
   static const char* harmony_trailing_commas_natives[] = {nullptr};
   static const char* harmony_class_fields_natives[] = {nullptr};
   static const char* harmony_object_rest_spread_natives[] = {nullptr};
   static const char* harmony_async_iteration_natives[] = {nullptr};
   static const char* harmony_dynamic_import_natives[] = {nullptr};
+  static const char* harmony_promise_finally_natives[] = {nullptr};
 
   for (int i = ExperimentalNatives::GetDebuggerCount();
        i < ExperimentalNatives::GetBuiltinsCount(); i++) {
 #define INSTALL_EXPERIMENTAL_NATIVES(id, desc)                                \
   if (FLAG_##id) {                                                            \
     for (size_t j = 0; id##_natives[j] != NULL; j++) {                        \
       Vector<const char> script_name = ExperimentalNatives::GetScriptName(i); \
       if (strncmp(script_name.start(), id##_natives[j],                       \
                   script_name.length()) == 0) {                               \
         if (!Bootstrapper::CompileExperimentalBuiltin(isolate(), i)) {        \
@@ skipping 736 matching lines @@
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   DCHECK(!IsActive());
 }
 
 }  // namespace internal
 }  // namespace v8