Remove unnecessary overflow check in BuildCreateAllocationMemento.

src/hydrogen.cc

 // Copyright 2013 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 2574 matching lines @@
   Add<HStoreNamedField>(
       allocation_memento,
       HObjectAccess::ForAllocationMementoSite(),
       allocation_site);
   if (FLAG_allocation_site_pretenuring) {
     HValue* memento_create_count = Add<HLoadNamedField>(
         allocation_site, HObjectAccess::ForAllocationSiteOffset(
             AllocationSite::kMementoCreateCountOffset));
     memento_create_count = AddUncasted<HAdd>(
         memento_create_count, graph()->GetConstant1());
+    // This smi value is reset to zero after every gc, overflow isn't a problem.

[Hannes Payer (out of office), 2013/12/04 10:32:33]

"isn't a problem since the counter is bounded by the new space size."

+    memento_create_count->ClearFlag(HValue::kCanOverflow);
     HStoreNamedField* store = Add<HStoreNamedField>(
         allocation_site, HObjectAccess::ForAllocationSiteOffset(
             AllocationSite::kMementoCreateCountOffset), memento_create_count);
     // No write barrier needed to store a smi.
     store->SkipWriteBarrier();
   }
 }
 
 
 HInstruction* HGraphBuilder::BuildGetNativeContext() {
@@ skipping 8203 matching lines @@
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 } }  // namespace v8::internal