[Interpreter] Allocate registers used as call arguments on-demand.

src/interpreter/bytecode-register.h

 // Copyright 2015 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.
 
 #ifndef V8_INTERPRETER_BYTECODE_REGISTER_H_
 #define V8_INTERPRETER_BYTECODE_REGISTER_H_
 
 #include "src/interpreter/bytecodes.h"
 
 #include "src/frames.h"
@@ skipping 87 matching lines @@
 
   int index_;
 };
 
 class RegisterList {
  public:
   RegisterList() : first_reg_index_(Register().index()), register_count_(0) {}
   RegisterList(int first_reg_index, int register_count)
       : first_reg_index_(first_reg_index), register_count_(register_count) {}
 
+  // Increases the size of the register list by one.
+  void IncrementRegisterCount() { register_count_++; }
+
   // Returns a new RegisterList which is a truncated version of this list, with
   // |count| registers.
   const RegisterList Truncate(int new_count) {
     DCHECK_GE(new_count, 0);
     DCHECK_LT(new_count, register_count_);
     return RegisterList(first_reg_index_, new_count);
   }
 
   const Register operator[](size_t i) const {
     DCHECK_LT(static_cast<int>(i), register_count_);
@@ skipping 13 matching lines @@
  private:
   int first_reg_index_;
   int register_count_;
 };
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_INTERPRETER_BYTECODE_REGISTER_H_