The IC exposes a register definition.

src/x64/ic-x64.cc

Index: src/x64/ic-x64.cc
diff --git a/src/x64/ic-x64.cc b/src/x64/ic-x64.cc
index 0cda1df16bd000674e60b600e7c0af54ab5edbdf..663860cd6e6ee851f74be6bad169645569e9c92e 100644
--- a/src/x64/ic-x64.cc
+++ b/src/x64/ic-x64.cc
@@ -1052,6 +1052,21 @@ void KeyedLoadIC::GenerateMiss(MacroAssembler* masm) {
 }
 
 
+// IC register specifications
+const Register LoadIC::ReceiverRegister() { return rax; }
+const Register LoadIC::NameRegister() { return rcx; }
+const Register KeyedLoadIC::ReceiverRegister() { return rdx; }
+const Register KeyedLoadIC::NameRegister() { return rax; }
+
+
+const Register* KeyedLoadIC::AllocateRegisterArray() {
+  Register* registers = new Register[kRegisterArgumentCount];
+  registers[0] = ReceiverRegister();
+  registers[1] = NameRegister();
+  return registers;
+}
+
+
 void KeyedLoadIC::GenerateRuntimeGetProperty(MacroAssembler* masm) {
   // ----------- S t a t e -------------
   //  -- rax    : key