Use a register spec for StoreIC and KeyedStoreIC.

src/x64/stub-cache-x64.cc

Index: src/x64/stub-cache-x64.cc
diff --git a/src/x64/stub-cache-x64.cc b/src/x64/stub-cache-x64.cc
index b305392ea29472921a5ae8b90cf7f732d4a625cb..886d9ad9d71ec8a0b36190ab299e835559627b69 100644
--- a/src/x64/stub-cache-x64.cc
+++ b/src/x64/stub-cache-x64.cc
@@ -1239,20 +1239,24 @@ Register* KeyedLoadStubCompiler::registers() {
 
 
 Register StoreStubCompiler::value() {
-  return rax;
+  return StoreIC::ValueRegister();
 }
 
 
 Register* StoreStubCompiler::registers() {
   // receiver, name, scratch1, scratch2, scratch3.
-  static Register registers[] = { rdx, rcx, rbx, rdi, r8 };
+  Register receiver = KeyedStoreIC::ReceiverRegister();
+  Register name = KeyedStoreIC::NameRegister();
+  static Register registers[] = { receiver, name, rbx, rdi, r8 };
   return registers;
 }
 
 
 Register* KeyedStoreStubCompiler::registers() {
   // receiver, name, scratch1, scratch2, scratch3.
-  static Register registers[] = { rdx, rcx, rbx, rdi, r8 };
+  Register receiver = KeyedStoreIC::ReceiverRegister();
+  Register name = KeyedStoreIC::NameRegister();
+  static Register registers[] = { receiver, name, rbx, rdi, r8 };
   return registers;
 }