[date] Refactor the %_DateField intrinsic to be optimizable.

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 "src/v8.h"
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/base/bits.h"
 #include "src/code-factory.h"
@@ skipping 1758 matching lines @@
   Register result = ToRegister(instr->result());
   Register map = ToRegister(instr->value());
   __ EnumLength(result, map);
 }
 
 
 void LCodeGen::DoDateField(LDateField* instr) {
   Register object = ToRegister(instr->date());
   Register result = ToRegister(instr->result());
   Smi* index = instr->index();
-  Label runtime, done, not_date_object;
   DCHECK(object.is(result));
   DCHECK(object.is(rax));
 
-  Condition cc = masm()->CheckSmi(object);
-  DeoptimizeIf(cc, instr, Deoptimizer::kSmi);
-  __ CmpObjectType(object, JS_DATE_TYPE, kScratchRegister);
-  DeoptimizeIf(not_equal, instr, Deoptimizer::kNotADateObject);
+  if (FLAG_debug_code) {
+    __ AssertNotSmi(object);
+    __ CmpObjectType(object, JS_DATE_TYPE, kScratchRegister);
+    __ Check(equal, kOperandIsNotADate);
+  }
 
   if (index->value() == 0) {
     __ movp(result, FieldOperand(object, JSDate::kValueOffset));
   } else {
+    Label runtime, done;
     if (index->value() < JSDate::kFirstUncachedField) {
       ExternalReference stamp = ExternalReference::date_cache_stamp(isolate());
       Operand stamp_operand = __ ExternalOperand(stamp);
       __ movp(kScratchRegister, stamp_operand);
       __ cmpp(kScratchRegister, FieldOperand(object,
                                              JSDate::kCacheStampOffset));
       __ j(not_equal, &runtime, Label::kNear);
       __ movp(result, FieldOperand(object, JSDate::kValueOffset +
                                            kPointerSize * index->value()));
       __ jmp(&done, Label::kNear);
@@ skipping 4225 matching lines @@
   RecordSafepoint(Safepoint::kNoLazyDeopt);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64