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

src/mips/full-codegen-mips.cc

Index: src/mips/full-codegen-mips.cc
diff --git a/src/mips/full-codegen-mips.cc b/src/mips/full-codegen-mips.cc
index ef8f981008fd5d9575009f4997f7eab1f5d2c5e8..47975c1d8b1b5c413fa9fe6f9c0f20c1badf3cf4 100644
--- a/src/mips/full-codegen-mips.cc
+++ b/src/mips/full-codegen-mips.cc
@@ -3894,6 +3894,28 @@ void FullCodeGenerator::EmitValueOf(CallRuntime* expr) {
 }
 
 
+void FullCodeGenerator::EmitThrowIfNotADate(CallRuntime* expr) {
+  ZoneList<Expression*>* args = expr->arguments();
+  DCHECK_EQ(1, args->length());
+
+  VisitForAccumulatorValue(args->at(0));  // Load the object.
+
+  Label done, not_date_object;
+  Register object = v0;
+  Register result = v0;
+  Register scratch1 = a1;
+
+  __ JumpIfSmi(object, &not_date_object);
+  __ GetObjectType(object, scratch1, scratch1);
+  __ Branch(&done, eq, scratch1, Operand(JS_DATE_TYPE));
+  __ bind(&not_date_object);
+  __ CallRuntime(Runtime::kThrowNotDateError, 0);
+
+  __ bind(&done);
+  context()->Plug(result);
+}
+
+
 void FullCodeGenerator::EmitDateField(CallRuntime* expr) {
   ZoneList<Expression*>* args = expr->arguments();
   DCHECK(args->length() == 2);
@@ -3902,20 +3924,15 @@ void FullCodeGenerator::EmitDateField(CallRuntime* expr) {
 
   VisitForAccumulatorValue(args->at(0));  // Load the object.
 
-  Label runtime, done, not_date_object;
   Register object = v0;
   Register result = v0;
   Register scratch0 = t5;
   Register scratch1 = a1;
 
-  __ JumpIfSmi(object, &not_date_object);
-  __ GetObjectType(object, scratch1, scratch1);
-  __ Branch(&not_date_object, ne, scratch1, Operand(JS_DATE_TYPE));
-
   if (index->value() == 0) {
     __ lw(result, FieldMemOperand(object, JSDate::kValueOffset));
-    __ jmp(&done);
   } else {
+    Label runtime, done;
     if (index->value() < JSDate::kFirstUncachedField) {
       ExternalReference stamp = ExternalReference::date_cache_stamp(isolate());
       __ li(scratch1, Operand(stamp));
@@ -3931,13 +3948,10 @@ void FullCodeGenerator::EmitDateField(CallRuntime* expr) {
     __ li(a1, Operand(index));
     __ Move(a0, object);
     __ CallCFunction(ExternalReference::get_date_field_function(isolate()), 2);
-    __ jmp(&done);
+    __ bind(&done);
   }
 
-  __ bind(&not_date_object);
-  __ CallRuntime(Runtime::kThrowNotDateError, 0);
-  __ bind(&done);
-  context()->Plug(v0);
+  context()->Plug(result);
 }