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..60403c6cfb5474e4f97dc91bbc1fba7c6ca5f85e 100644
--- a/src/x64/ic-x64.cc
+++ b/src/x64/ic-x64.cc
@@ -1052,6 +1052,13 @@ 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; }
+
+
 void KeyedLoadIC::GenerateRuntimeGetProperty(MacroAssembler* masm) {
   // ----------- S t a t e -------------
   //  -- rax    : key