S390: [Atomics] code stubs for atomic operations

src/s390/interface-descriptors-s390.cc

Index: src/s390/interface-descriptors-s390.cc
diff --git a/src/s390/interface-descriptors-s390.cc b/src/s390/interface-descriptors-s390.cc
index f77d54d4283dc05f1ac103959f8d9254640cf97a..9f24f5761be45c74c1535879592e8e9e5a11ec50 100644
--- a/src/s390/interface-descriptors-s390.cc
+++ b/src/s390/interface-descriptors-s390.cc
@@ -376,6 +376,15 @@ void ResumeGeneratorDescriptor::InitializePlatformSpecific(
   };
   data->InitializePlatformSpecific(arraysize(registers), registers);
 }
+
+void AtomicsLoadDescriptor::InitializePlatformSpecific(
+    CallInterfaceDescriptorData* data) {
+  Register registers[] = {
+      r3,  // the typedarray object
+      r2   // the index to load (untagged)
+  };
+  data->InitializePlatformSpecific(arraysize(registers), registers);
+}
 }  // namespace internal
 }  // namespace v8