Refactor bigint shifting code in preparation of shifting intrinsics.

runtime/vm/intrinsifier_x64.cc

 // 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.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/intrinsifier.h"
 
 #include "vm/assembler.h"
@@ skipping 707 matching lines @@
   __ xorq(RAX, RCX);
   // BSR does not write the destination register if source is zero.  Put a 1 in
   // the Smi tag bit to ensure BSR writes to destination register.
   __ orq(RAX, Immediate(kSmiTagMask));
   __ bsrq(RAX, RAX);
   __ SmiTag(RAX);
   __ ret();
 }
 
 
+void Intrinsifier::Bigint_lsh(Assembler* assembler) {
+  // TODO(regis): Implement.
+}
+
+
+void Intrinsifier::Bigint_rsh(Assembler* assembler) {
+  // TODO(regis): Implement.
+}
+
+
 void Intrinsifier::Bigint_absAdd(Assembler* assembler) {
   // static void _absAdd(Uint32List digits, int used,
   //                     Uint32List a_digits, int a_used,
   //                     Uint32List r_digits)
 
   __ movq(RDI, Address(RSP, 5 * kWordSize));  // digits
   __ movq(R8, Address(RSP, 4 * kWordSize));  // used is Smi
   __ addq(R8, Immediate(2));  // used > 0, Smi. R8 = used + 1, round up.
   __ sarq(R8, Immediate(2));  // R8 = number of digit pairs to process.
   __ movq(RSI, Address(RSP, 3 * kWordSize));  // a_digits
@@ skipping 1175 matching lines @@
   // Set return value to Isolate::current_tag_.
   __ movq(RAX, Address(RBX, Isolate::current_tag_offset()));
   __ ret();
 }
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64