Improve Array.shift() performance for small arrays.

src/x64/lithium-x64.cc

 // Copyright 2012 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.
 
 #include "v8.h"
 
 #if V8_TARGET_ARCH_X64
 
 #include "lithium-allocator-inl.h"
 #include "x64/lithium-x64.h"
@@ skipping 2235 matching lines @@
   } else {
     LOperand* object = UseFixed(instr->object(), rax);
     LOperand* context = UseFixed(instr->context(), rsi);
     LTransitionElementsKind* result =
         new(zone()) LTransitionElementsKind(object, context, NULL, NULL);
     return MarkAsCall(result, instr);
   }
 }
 
 
+LInstruction* LChunkBuilder::DoArrayShift(HArrayShift* instr) {
+  LOperand* object = UseFixed(instr->object(), rax);
+  LOperand* context = UseFixed(instr->context(), rsi);
+  LArrayShift* result = new(zone()) LArrayShift(context, object);
+  return MarkAsCall(DefineFixed(result, rax), instr, CANNOT_DEOPTIMIZE_EAGERLY);
+}
+
+
 LInstruction* LChunkBuilder::DoTrapAllocationMemento(
     HTrapAllocationMemento* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* temp = TempRegister();
   LTrapAllocationMemento* result =
       new(zone()) LTrapAllocationMemento(object, temp);
   return AssignEnvironment(result);
 }
 
 
@@ skipping 319 matching lines @@
   LOperand* index = UseTempRegister(instr->index());
   LLoadFieldByIndex* load = new(zone()) LLoadFieldByIndex(object, index);
   LInstruction* result = DefineSameAsFirst(load);
   return AssignPointerMap(result);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64