A64: Use a scope utility to allocate scratch registers.

src/a64/assembler-a64.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 443 matching lines @@
   CPURegister::RegisterType type() const {
     ASSERT(IsValid());
     return type_;
   }
 
   RegList list() const {
     ASSERT(IsValid());
     return list_;
   }
 
+  inline void set_list(RegList new_list) {
+    ASSERT(IsValid());
+    list_ = new_list;
+  }
+
   // Combine another CPURegList into this one. Registers that already exist in
   // this list are left unchanged. The type and size of the registers in the
   // 'other' list must match those in this list.
   void Combine(const CPURegList& other);
 
   // Remove every register in the other CPURegList from this one. Registers that
   // do not exist in this list are ignored. The type and size of the registers
   // in the 'other' list must match those in this list.
   void Remove(const CPURegList& other);
 
-  // Variants of Combine and Remove which take a single register.
+  // Variants of Combine and Remove which take CPURegisters.
   void Combine(const CPURegister& other);
-  void Remove(const CPURegister& other);
+  void Remove(const CPURegister& other1,
+              const CPURegister& other2 = NoCPUReg,
+              const CPURegister& other3 = NoCPUReg,
+              const CPURegister& other4 = NoCPUReg);
 
   // Variants of Combine and Remove which take a single register by its code;
   // the type and size of the register is inferred from this list.
   void Combine(int code);
   void Remove(int code);
 
   // Remove all callee-saved registers from the list. This can be useful when
   // preparing registers for an AAPCS64 function call, for example.
   void RemoveCalleeSaved();
 
@@ skipping 1589 matching lines @@
 class EnsureSpace BASE_EMBEDDED {
  public:
   explicit EnsureSpace(Assembler* assembler) {
     assembler->CheckBuffer();
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_A64_ASSEMBLER_A64_H_