Implement IsConstructor() abstract operation

src/runtime/runtime-function.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/v8.h"
 
 #include "src/accessors.h"
 #include "src/arguments.h"
 #include "src/compiler.h"
 #include "src/deoptimizer.h"
@@ skipping 308 matching lines @@
   CONVERT_ARG_CHECKED(Object, object, 0);
 
   if (object->IsJSFunction()) {
     JSFunction* func = JSFunction::cast(object);
     func->shared()->set_native(true);
   }
   return isolate->heap()->undefined_value();
 }
 
 
+RUNTIME_FUNCTION(Runtime_IsConstructor) {
+  HandleScope handles(isolate);
+  RUNTIME_ASSERT(args.length() == 1);
+
+  CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
+
+  // TODO(caitp): implement this in a better/simpler way, allow inlining via TF
+  if (object->IsJSFunction()) {
+    Handle<JSFunction> func = Handle<JSFunction>::cast(object);
+    bool should_have_prototype = func->should_have_prototype();
+    if (func->shared()->bound()) {
+      Handle<FixedArray> bound_args =
+          Handle<FixedArray>(FixedArray::cast(func->function_bindings()));
+      Handle<Object> bound_function(
+          JSReceiver::cast(bound_args->get(JSFunction::kBoundFunctionIndex)),
+          isolate);
+      if (bound_function->IsJSFunction()) {
+        Handle<JSFunction> bound = Handle<JSFunction>::cast(bound_function);
+        DCHECK(!bound->shared()->bound());
+        should_have_prototype = bound->should_have_prototype();
+      }
+    }
+    return isolate->heap()->ToBoolean(should_have_prototype);
+  }
+  return isolate->heap()->false_value();
+}
+
+
 RUNTIME_FUNCTION(Runtime_SetInlineBuiltinFlag) {
   SealHandleScope shs(isolate);
   RUNTIME_ASSERT(args.length() == 1);
   CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
 
   if (object->IsJSFunction()) {
     JSFunction* func = JSFunction::cast(*object);
     func->shared()->set_inline_builtin(true);
   }
   return isolate->heap()->undefined_value();
@@ skipping 276 matching lines @@
 
 
 RUNTIME_FUNCTION(RuntimeReference_IsFunction) {
   SealHandleScope shs(isolate);
   DCHECK(args.length() == 1);
   CONVERT_ARG_CHECKED(Object, obj, 0);
   return isolate->heap()->ToBoolean(obj->IsJSFunction());
 }
 }
 }  // namespace v8::internal