The IC exposes a register definition.

src/ic.h

Index: src/ic.h
diff --git a/src/ic.h b/src/ic.h
index 3f550438a487849c8931dc6d87f7b51d8b125405..7c999daf3006adbb4aa61ec18db9419c6c8cd63e 100644
--- a/src/ic.h
+++ b/src/ic.h
@@ -398,6 +398,14 @@ class LoadIC: public IC {
   class ContextualModeBits: public BitField<ContextualMode, 0, 1> {};
   STATIC_ASSERT(static_cast<int>(NOT_CONTEXTUAL) == 0);
 
+  enum RegisterInfo {
+    kReceiverIndex,
+    kNameIndex,
+    kRegisterArgumentCount
+  };
+  static const Register ReceiverRegister();
+  static const Register NameRegister();
+
   static ExtraICState ComputeExtraICState(ContextualMode contextual_mode) {
     return ContextualModeBits::encode(contextual_mode);
   }
@@ -498,6 +506,9 @@ class KeyedLoadIC: public LoadIC {
     ASSERT(target()->is_keyed_load_stub());
   }
 
+  static const Register ReceiverRegister();
+  static const Register NameRegister();
+
   MUST_USE_RESULT MaybeHandle<Object> Load(Handle<Object> object,
                                            Handle<Object> key);