Optimize JS date implementation for smi-only arrays

src/runtime.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 7857 matching lines @@
   ASSERT(args.length() == 2);
 
   CONVERT_DOUBLE_ARG_CHECKED(t, 0);
   CONVERT_CHECKED(JSArray, res_array, args[1]);
 
   int year, month, day;
   DateYMDFromTime(static_cast<int>(floor(t / 86400000)), year, month, day);
 
   FixedArrayBase* elms_base = FixedArrayBase::cast(res_array->elements());
   RUNTIME_ASSERT(elms_base->length() == 3);
-  RUNTIME_ASSERT(res_array->GetElementsKind() <= FAST_DOUBLE_ELEMENTS);
+  RUNTIME_ASSERT(res_array->HasFastTypeElements());
 
-  if (res_array->HasFastDoubleElements()) {
-    FixedDoubleArray* elms = FixedDoubleArray::cast(res_array->elements());
-    elms->set(0, year);
-    elms->set(1, month);
-    elms->set(2, day);
-  } else {
-    FixedArray* elms = FixedArray::cast(res_array->elements());
-    elms->set(0, Smi::FromInt(year));
-    elms->set(1, Smi::FromInt(month));
-    elms->set(2, Smi::FromInt(day));
-  }
+  MaybeObject* maybe = res_array->EnsureWritableFastElements();
+  if (maybe->IsFailure()) return maybe;
+  FixedArray* elms = FixedArray::cast(res_array->elements());
+  elms->set(0, Smi::FromInt(year));
+  elms->set(1, Smi::FromInt(month));
+  elms->set(2, Smi::FromInt(day));
 
   return isolate->heap()->undefined_value();
 }
 
 
 RUNTIME_FUNCTION(MaybeObject*, Runtime_NewArgumentsFast) {
   HandleScope scope(isolate);
   ASSERT(args.length() == 3);
 
   Handle<JSFunction> callee = args.at<JSFunction>(0);
@@ skipping 5584 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags);
   }
 }
 
 
 } }  // namespace v8::internal