Improve Array.shift() performance for small arrays.

src/x64/lithium-codegen-x64.cc

 // Copyright 2013 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 "x64/lithium-codegen-x64.h"
 #include "code-stubs.h"
@@ skipping 4382 matching lines @@
     __ Move(rbx, to_map);
     bool is_js_array = from_map->instance_type() == JS_ARRAY_TYPE;
     TransitionElementsKindStub stub(isolate(), from_kind, to_kind, is_js_array);
     __ CallStub(&stub);
     RecordSafepointWithLazyDeopt(instr, RECORD_SAFEPOINT_WITH_REGISTERS, 0);
   }
   __ bind(&not_applicable);
 }
 
 
+void LCodeGen::DoArrayShift(LArrayShift* instr) {
+  ASSERT(ToRegister(instr->context()).is(rsi));
+  ASSERT(ToRegister(instr->object()).is(rax));
+  ASSERT(ToRegister(instr->result()).is(rax));
+  ArrayShiftStub stub(isolate(), instr->hydrogen()->kind());
+  CallCode(stub.GetCode(), RelocInfo::CODE_TARGET, instr);
+}
+
+
 void LCodeGen::DoTrapAllocationMemento(LTrapAllocationMemento* instr) {
   Register object = ToRegister(instr->object());
   Register temp = ToRegister(instr->temp());
   Label no_memento_found;
   __ TestJSArrayForAllocationMemento(object, temp, &no_memento_found);
   DeoptimizeIf(equal, instr->environment());
   __ bind(&no_memento_found);
 }
 
 
@@ skipping 1299 matching lines @@
   __ bind(deferred->exit());
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64