The IC exposes a register definition.

src/x64/ic-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/codegen.h"
 #include "src/ic-inl.h"
@@ skipping 1034 matching lines @@
   __ Push(rax);  // name
   __ PushReturnAddressFrom(rbx);
 
   // Perform tail call to the entry.
   ExternalReference ref =
       ExternalReference(IC_Utility(kKeyedLoadIC_Miss), masm->isolate());
   __ TailCallExternalReference(ref, 2, 1);
 }
 
 
+// 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
   //  -- rdx    : receiver
   //  -- rsp[0] : return address
   // -----------------------------------
 
   __ PopReturnAddressTo(rbx);
   __ Push(rdx);  // receiver
   __ Push(rax);  // name
@@ skipping 237 matching lines @@
   Condition cc = (check == ENABLE_INLINED_SMI_CHECK)
       ? (*jmp_address == Assembler::kJncShortOpcode ? not_zero : zero)
       : (*jmp_address == Assembler::kJnzShortOpcode ? not_carry : carry);
   *jmp_address = static_cast<byte>(Assembler::kJccShortPrefix | cc);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64