[Atomics] code stubs for atomic operations

src/x64/interface-descriptors-x64.cc

Index: src/x64/interface-descriptors-x64.cc
diff --git a/src/x64/interface-descriptors-x64.cc b/src/x64/interface-descriptors-x64.cc
index 1eb0055cf7542d1357d85209b210307012622004..0b887a29af3fe9088b89dc0d2bf9b663b3d7ef63 100644
--- a/src/x64/interface-descriptors-x64.cc
+++ b/src/x64/interface-descriptors-x64.cc
@@ -420,6 +420,15 @@ void ResumeGeneratorDescriptor::InitializePlatformSpecific(
   data->InitializePlatformSpecific(arraysize(registers), registers);
 }
 
+void AtomicsLoadDescriptor::InitializePlatformSpecific(
+    CallInterfaceDescriptorData* data) {
+  Register registers[] = {
+      rdx,  // the typedarray object
+      rax   // the index to load (untagged)
+  };
+  data->InitializePlatformSpecific(arraysize(registers), registers);
+}
+
 }  // namespace internal
 }  // namespace v8