The IC exposes a register definition.

src/mips/ic-mips.cc

Index: src/mips/ic-mips.cc
diff --git a/src/mips/ic-mips.cc b/src/mips/ic-mips.cc
index cbf721adb8c8ec9ae7dc70039a4af2f885310f5d..3a428a9f13c68108ac475f0467e9df8163581ef9 100644
--- a/src/mips/ic-mips.cc
+++ b/src/mips/ic-mips.cc
@@ -560,6 +560,21 @@ void KeyedLoadIC::GenerateMiss(MacroAssembler* masm) {
 }
 
 
+// IC register specifications
+const Register LoadIC::ReceiverRegister() { return a0; }
+const Register LoadIC::NameRegister() { return a2; }
+const Register KeyedLoadIC::ReceiverRegister() { return a1; }
+const Register KeyedLoadIC::NameRegister() { return a0; }
+
+
+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 --------------
   //  -- ra     : return address