[Atomics] code stubs for atomic operations

src/x64/interface-descriptors-x64.cc

 // Copyright 2012 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.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/interface-descriptors.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 427 matching lines @@
 void InterpreterCEntryDescriptor::InitializePlatformSpecific(
     CallInterfaceDescriptorData* data) {
   Register registers[] = {
       rax,  // argument count (argc)
       r15,  // address of first argument (argv)
       rbx   // the runtime function to call
   };
   data->InitializePlatformSpecific(arraysize(registers), registers);
 }
 
+
+void AtomicsLoadDescriptor::InitializePlatformSpecific(
+    CallInterfaceDescriptorData* data) {
+  Register registers[] = {rdx, rax};
+  data->InitializePlatformSpecific(arraysize(registers), registers);
+}
+
+
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64