Make guard_cid and nullable_cid half words.

runtime/vm/assembler_x64.h

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_ASSEMBLER_X64_H_
 #define VM_ASSEMBLER_X64_H_
 
 #ifndef VM_ASSEMBLER_H_
 #error Do not include assembler_x64.h directly; use assembler.h instead.
 #endif
@@ skipping 379 matching lines @@
   void movb(Register dst, const Address& src);
   void movb(const Address& dst, Register src);
   void movb(const Address& dst, const Immediate& imm);
 
   void movzxw(Register dst, Register src);
   void movzxw(Register dst, const Address& src);
   void movsxw(Register dst, Register src);
   void movsxw(Register dst, const Address& src);
   void movw(Register dst, const Address& src);
   void movw(const Address& dst, Register src);
+  void movw(const Address& dst, const Immediate& imm);
 
   void movq(Register dst, const Immediate& imm);
   void movq(Register dst, Register src);
   void movq(Register dst, const Address& src);
   void movq(const Address& dst, Register src);
   void movq(const Address& dst, const Immediate& imm);
 
   void movsxd(Register dst, Register src);
   void movsxd(Register dst, const Address& src);
 
@@ skipping 95 matching lines @@
     kRoundUp        = 0x2,
     kRoundToZero    = 0x3
   };
   void roundsd(XmmRegister dst, XmmRegister src, RoundingMode mode);
 
   void xchgl(Register dst, Register src);
   void xchgq(Register dst, Register src);
 
   void cmpb(const Address& address, const Immediate& imm);
 
+  void cmpw(Register reg, const Address& address);
+  void cmpw(const Address& address, const Immediate& imm);
+
   void cmpl(Register reg, const Immediate& imm);
   void cmpl(Register reg0, Register reg1);
   void cmpl(Register reg, const Address& address);
   void cmpl(const Address& address, const Immediate& imm);
 
   void cmpq(Register reg, const Immediate& imm);
   void cmpq(const Address& address, Register reg);
   void cmpq(const Address& address, const Immediate& imm);
   void cmpq(Register reg0, Register reg1);
   void cmpq(Register reg, const Address& address);
@@ skipping 670 matching lines @@
 }
 
 
 inline void Assembler::EmitOperandSizeOverride() {
   EmitUint8(0x66);
 }
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_X64_H_