The IC exposes a register definition.

src/arm64/stub-cache-arm64.cc

 // Copyright 2013 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_ARM64
 
 #include "src/codegen.h"
 #include "src/ic-inl.h"
@@ skipping 1227 matching lines @@
 
 
 // TODO(all): The so-called scratch registers are significant in some cases. For
 // example, KeyedStoreStubCompiler::registers()[3] (x3) is actually used for
 // KeyedStoreCompiler::transition_map(). We should verify which registers are
 // actually scratch registers, and which are important. For now, we use the same
 // assignments as ARM to remain on the safe side.
 
 Register* LoadStubCompiler::registers() {
   // receiver, name, scratch1, scratch2, scratch3, scratch4.
-  static Register registers[] = { x0, x2, x3, x1, x4, x5 };
+  Register receiver = LoadIC::ReceiverRegister();
+  Register name = LoadIC::NameRegister();
+  static Register registers[] = { receiver, name, x3, x1, x4, x5 };
   return registers;
 }
 
 
 Register* KeyedLoadStubCompiler::registers() {
-  // receiver, name/key, scratch1, scratch2, scratch3, scratch4.
-  static Register registers[] = { x1, x0, x2, x3, x4, x5 };
+  // receiver, name, scratch1, scratch2, scratch3, scratch4.
+  Register receiver = KeyedLoadIC::ReceiverRegister();
+  Register name = KeyedLoadIC::NameRegister();
+  static Register registers[] = { receiver, name, x2, x3, x4, x5 };
   return registers;
 }
 
 
 Register StoreStubCompiler::value() {
   return x0;
 }
 
 
 Register* StoreStubCompiler::registers() {
@@ skipping 202 matching lines @@
 
   // Miss case, call the runtime.
   __ Bind(&miss);
   TailCallBuiltin(masm, Builtins::kKeyedLoadIC_Miss);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM64