Implement bigint shift intrinsics on x64.

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 609 matching lines @@
   void sarl(Register operand, Register shifter);
   void shldl(Register dst, Register src, const Immediate& imm);
 
   void shlq(Register reg, const Immediate& imm);
   void shlq(Register operand, Register shifter);
   void shrq(Register reg, const Immediate& imm);
   void shrq(Register operand, Register shifter);
   void sarq(Register reg, const Immediate& imm);
   void sarq(Register operand, Register shifter);
   void shldq(Register dst, Register src, const Immediate& imm);
+  void shldq(Register dst, Register src, Register shifter);
+  void shrdq(Register dst, Register src, Register shifter);
 
   void incl(const Address& address);
   void decl(const Address& address);
 
   void incq(Register reg);
   void incq(const Address& address);
   void decq(Register reg);
   void decq(const Address& address);
 
   void negl(Register reg);
@@ skipping 549 matching lines @@
 }
 
 
 inline void Assembler::EmitOperandSizeOverride() {
   EmitUint8(0x66);
 }
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_X64_H_