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

src/arm/lithium-codegen-arm.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 "src/v8.h"
 
 #include "src/arm/lithium-codegen-arm.h"
 #include "src/arm/lithium-gap-resolver-arm.h"
 #include "src/base/bits.h"
 #include "src/code-factory.h"
@@ skipping 1912 matching lines @@
   Register map = ToRegister(instr->value());
   __ EnumLength(result, map);
 }
 
 
 void LCodeGen::DoDateField(LDateField* instr) {
   Register object = ToRegister(instr->date());
   Register result = ToRegister(instr->result());
   Register scratch = ToRegister(instr->temp());
   Smi* index = instr->index();
-  Label runtime, done;
   DCHECK(object.is(result));
   DCHECK(object.is(r0));
   DCHECK(!scratch.is(scratch0()));
   DCHECK(!scratch.is(object));
 
-  __ SmiTst(object);
-  DeoptimizeIf(eq, instr, Deoptimizer::kSmi);
-  __ CompareObjectType(object, scratch, scratch, JS_DATE_TYPE);
-  DeoptimizeIf(ne, instr, Deoptimizer::kNotADateObject);
-
   if (index->value() == 0) {
     __ ldr(result, FieldMemOperand(object, JSDate::kValueOffset));
   } else {
+    Label runtime, done;
     if (index->value() < JSDate::kFirstUncachedField) {
       ExternalReference stamp = ExternalReference::date_cache_stamp(isolate());
       __ mov(scratch, Operand(stamp));
       __ ldr(scratch, MemOperand(scratch));
       __ ldr(scratch0(), FieldMemOperand(object, JSDate::kCacheStampOffset));
       __ cmp(scratch, scratch0());
       __ b(ne, &runtime);
       __ ldr(result, FieldMemOperand(object, JSDate::kValueOffset +
                                              kPointerSize * index->value()));
       __ jmp(&done);
@@ skipping 4056 matching lines @@
   __ push(ToRegister(instr->function()));
   CallRuntime(Runtime::kPushBlockContext, 2, instr);
   RecordSafepoint(Safepoint::kNoLazyDeopt);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8