[runtime] Introduce dedicated JSBoundFunction to represent bound functions.

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 34494122096da30dfc5919d15e74e71547e42136..1dee9794dfc2bd509088fcb9a8b9d57ec32ed540 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -269,8 +269,7 @@ class Genesis BASE_EMBEDDED {
     FUNCTION_WITH_WRITEABLE_PROTOTYPE,
     FUNCTION_WITH_READONLY_PROTOTYPE,
     // Without prototype.
-    FUNCTION_WITHOUT_PROTOTYPE,
-    BOUND_FUNCTION
+    FUNCTION_WITHOUT_PROTOTYPE
   };
 
   static bool IsFunctionModeWithPrototype(FunctionMode function_mode) {
@@ -486,7 +485,7 @@ void Genesis::SetFunctionInstanceDescriptor(Handle<Map> map,
 Handle<Map> Genesis::CreateSloppyFunctionMap(FunctionMode function_mode) {
   Handle<Map> map = factory()->NewMap(JS_FUNCTION_TYPE, JSFunction::kSize);
   SetFunctionInstanceDescriptor(map, function_mode);
-  map->set_is_constructor(IsFunctionModeWithPrototype(function_mode));
+  if (IsFunctionModeWithPrototype(function_mode)) map->set_is_constructor();
   map->set_is_callable();
   return map;
 }
@@ -609,35 +608,22 @@ void Genesis::SetStrictFunctionInstanceDescriptor(Handle<Map> map,
   PropertyAttributes roc_attribs =
       static_cast<PropertyAttributes>(DONT_ENUM | READ_ONLY);
 
-  if (function_mode == BOUND_FUNCTION) {
-    {  // Add length.
-      Handle<String> length_string = isolate()->factory()->length_string();
-      DataDescriptor d(length_string, 0, roc_attribs, Representation::Tagged());
-      map->AppendDescriptor(&d);
-    }
-    {  // Add name.
-      Handle<String> name_string = isolate()->factory()->name_string();
-      DataDescriptor d(name_string, 1, roc_attribs, Representation::Tagged());
-      map->AppendDescriptor(&d);
-    }
-  } else {
-    DCHECK(function_mode == FUNCTION_WITH_WRITEABLE_PROTOTYPE ||
-           function_mode == FUNCTION_WITH_READONLY_PROTOTYPE ||
-           function_mode == FUNCTION_WITHOUT_PROTOTYPE);
-    {  // Add length.
-      Handle<AccessorInfo> length =
-          Accessors::FunctionLengthInfo(isolate(), roc_attribs);
-      AccessorConstantDescriptor d(Handle<Name>(Name::cast(length->name())),
-                                   length, roc_attribs);
-      map->AppendDescriptor(&d);
-    }
-    {  // Add name.
-      Handle<AccessorInfo> name =
-          Accessors::FunctionNameInfo(isolate(), roc_attribs);
-      AccessorConstantDescriptor d(Handle<Name>(Name::cast(name->name())), name,
-                                   roc_attribs);
-      map->AppendDescriptor(&d);
-    }
+  DCHECK(function_mode == FUNCTION_WITH_WRITEABLE_PROTOTYPE ||
+         function_mode == FUNCTION_WITH_READONLY_PROTOTYPE ||
+         function_mode == FUNCTION_WITHOUT_PROTOTYPE);
+  {  // Add length.
+    Handle<AccessorInfo> length =
+        Accessors::FunctionLengthInfo(isolate(), roc_attribs);
+    AccessorConstantDescriptor d(Handle<Name>(Name::cast(length->name())),
+                                 length, roc_attribs);
+    map->AppendDescriptor(&d);
+  }
+  {  // Add name.
+    Handle<AccessorInfo> name =
+        Accessors::FunctionNameInfo(isolate(), roc_attribs);
+    AccessorConstantDescriptor d(Handle<Name>(Name::cast(name->name())), name,
+                                 roc_attribs);
+    map->AppendDescriptor(&d);
   }
   if (IsFunctionModeWithPrototype(function_mode)) {
     // Add prototype.
@@ -732,7 +718,7 @@ Handle<Map> Genesis::CreateStrictFunctionMap(
     FunctionMode function_mode, Handle<JSFunction> empty_function) {
   Handle<Map> map = factory()->NewMap(JS_FUNCTION_TYPE, JSFunction::kSize);
   SetStrictFunctionInstanceDescriptor(map, function_mode);
-  map->set_is_constructor(IsFunctionModeWithPrototype(function_mode));
+  if (IsFunctionModeWithPrototype(function_mode)) map->set_is_constructor();
   map->set_is_callable();
   Map::SetPrototype(map, empty_function);
   return map;
@@ -743,7 +729,7 @@ Handle<Map> Genesis::CreateStrongFunctionMap(
     Handle<JSFunction> empty_function, bool is_constructor) {
   Handle<Map> map = factory()->NewMap(JS_FUNCTION_TYPE, JSFunction::kSize);
   SetStrongFunctionInstanceDescriptor(map);
-  map->set_is_constructor(is_constructor);
+  if (is_constructor) map->set_is_constructor();
   Map::SetPrototype(map, empty_function);
   map->set_is_callable();
   map->set_is_extensible(is_constructor);
@@ -770,21 +756,6 @@ void Genesis::CreateStrictModeFunctionMaps(Handle<JSFunction> empty) {
   // This map is installed in MakeFunctionInstancePrototypeWritable.
   strict_function_map_writable_prototype_ =
       CreateStrictFunctionMap(FUNCTION_WITH_WRITEABLE_PROTOTYPE, empty);
-
-  // Special map for non-constructor bound functions.
-  // TODO(bmeurer): Bound functions should not be represented as JSFunctions.
-  Handle<Map> bound_function_without_constructor_map =
-      CreateStrictFunctionMap(BOUND_FUNCTION, empty);
-  native_context()->set_bound_function_without_constructor_map(
-      *bound_function_without_constructor_map);
-
-  // Special map for constructor bound functions.
-  // TODO(bmeurer): Bound functions should not be represented as JSFunctions.
-  Handle<Map> bound_function_with_constructor_map =
-      Map::Copy(bound_function_without_constructor_map, "IsConstructor");
-  bound_function_with_constructor_map->set_is_constructor(true);
-  native_context()->set_bound_function_with_constructor_map(
-      *bound_function_with_constructor_map);
 }
 
 
@@ -1459,6 +1430,35 @@ void Genesis::InitializeGlobal(Handle<JSGlobalObject> global_object,
                                      Context::JS_WEAK_SET_FUN_INDEX);
   }
 
+  {  // --- B o u n d F u n c t i o n
+    Handle<Map> map =
+        factory->NewMap(JS_BOUND_FUNCTION_TYPE, JSBoundFunction::kSize);
+    map->set_is_callable();
+    Map::SetPrototype(map, empty_function);
+
+    PropertyAttributes roc_attribs =
+        static_cast<PropertyAttributes>(DONT_ENUM | READ_ONLY);
+    Map::EnsureDescriptorSlack(map, 2);
+
+    {  // length
+      DataDescriptor d(factory->length_string(), JSBoundFunction::kLengthIndex,
+                       roc_attribs, Representation::Tagged());
+      map->AppendDescriptor(&d);
+    }
+    {  // name
+      DataDescriptor d(factory->name_string(), JSBoundFunction::kNameIndex,
+                       roc_attribs, Representation::Tagged());
+      map->AppendDescriptor(&d);
+    }
+
+    map->SetInObjectProperties(2);
+    native_context()->set_bound_function_without_constructor_map(*map);
+
+    map = Map::Copy(map, "IsConstructor");
+    map->set_is_constructor();
+    native_context()->set_bound_function_with_constructor_map(*map);
+  }
+
   {  // --- sloppy arguments map
     // Make sure we can recognize argument objects at runtime.
     // This is done by introducing an anonymous function with
@@ -2285,7 +2285,7 @@ void Genesis::InstallJSProxyMaps() {
 
   Handle<Map> proxy_function_map =
       Map::Copy(isolate()->sloppy_function_without_prototype_map(), "Proxy");
-  proxy_function_map->set_is_constructor(true);
+  proxy_function_map->set_is_constructor();
   native_context()->set_proxy_function_map(*proxy_function_map);
 
   Handle<Map> proxy_map =
@@ -2299,7 +2299,7 @@ void Genesis::InstallJSProxyMaps() {
 
   Handle<Map> proxy_constructor_map =
       Map::Copy(proxy_callable_map, "constructor Proxy");
-  proxy_constructor_map->set_is_constructor(true);
+  proxy_constructor_map->set_is_constructor();
   native_context()->set_proxy_constructor_map(*proxy_constructor_map);
 }
 
@@ -2525,7 +2525,8 @@ bool Genesis::InstallNatives(ContextType context_type) {
     // Set the lengths for the functions to satisfy ECMA-262.
     concat->shared()->set_length(1);
   }
-  // Install Function.prototype.apply, call, and toString.
+
+  // Install Function.prototype.apply, bind, call, and toString.
   {
     Handle<String> key = factory()->Function_string();
     Handle<JSFunction> function =
@@ -2534,9 +2535,11 @@ bool Genesis::InstallNatives(ContextType context_type) {
     Handle<JSObject> proto =
         Handle<JSObject>(JSObject::cast(function->instance_prototype()));
 
-    // Install the apply, call and toString functions.
+    // Install the apply, bind, call and toString functions.
     SimpleInstallFunction(proto, factory()->apply_string(),
                           Builtins::kFunctionPrototypeApply, 2, false);
+    SimpleInstallFunction(proto, factory()->bind_string(),
+                          Builtins::kFunctionPrototypeBind, 1, false);
     SimpleInstallFunction(proto, factory()->call_string(),
                           Builtins::kFunctionPrototypeCall, 1, false);
     SimpleInstallFunction(proto, factory()->toString_string(),