boxing + unboxing a VT is not a no-op ? (original) (raw)

Remi Forax forax at univ-mlv.fr
Thu Jul 12 18:43:26 UTC 2018

Hi guys, it seems that operations likes VT -> Object -> VT are not optimized has being a no-op.

with IntBox being a value type that wrap an int, this code is slow (not very slow, i.e not interpreter slow)

public int valuelist_intbox_innervalue_inlined_reduce() { __ByValue class Adder implements BiFunction<IntBox, IntBox, IntBox> { private final boolean nonEmpty;

  Adder() {
    nonEmpty = false;
    throw new AssertionError();
  }
  
  public IntBox apply(IntBox acc, IntBox element) {
    return acc.add(element);
  }
}
BiFunction<IntBox, IntBox, IntBox> mapper = __MakeDefault Adder();
var sum = IntBox.zero();
int size = valueList.size();
for(int i = 0; i < size; i++) {
  sum = mapper.apply(sum, valueList.get(i));
}
return sum.intValue();

}

while this code is fast (more than 10 times faster) public int valuelist_intbox_inlined_reduce() { var sum = IntBox.zero(); int size = valueList.size(); for(int i = 0; i < size; i++) { sum = sum.add(valueList.get(i)); } return sum.intValue(); }

the difference is that instead of calling add on an IntBox to do the addition, i used an anonymous value class which implement a functional interface which used Objects. (valueList is just an array of IntBox wrapped in a value type).

regards, Rémi

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