Restrict immediate operands to smi where only smis are supported.

runtime/vm/assembler_x64.h

 // Copyright (c) 2012, 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 422 matching lines @@
   void cqo();
 
   void idivl(Register reg);
   void idivq(Register reg);
 
   void imull(Register dst, Register src);
   void imull(Register reg, const Immediate& imm);
 
   void imulq(Register dst, Register src);
   void imulq(Register dst, const Address& address);
+  void imulq(Register dst, const Immediate& imm);
 
   void subq(Register dst, Register src);
   void subq(Register reg, const Immediate& imm);
   void subq(Register reg, const Address& address);
 
   void shll(Register reg, const Immediate& imm);
   void shll(Register operand, Register shifter);
   void shrl(Register reg, const Immediate& imm);
   void shrl(Register operand, Register shifter);
   void sarl(Register reg, const Immediate& imm);
@@ skipping 277 matching lines @@
 }
 
 
 inline void Assembler::EmitOperandSizeOverride() {
   EmitUint8(0x66);
 }
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_X64_H_