On constant folding of final field loads

Paul Sandoz paul.sandoz at oracle.com
Mon Jun 29 12:13:39 UTC 2015

On Jun 29, 2015, at 2:00 PM, Vladimir Ivanov <vladimir.x.ivanov at oracle.com> wrote:

> Paul,
>> For MHs it's not possible to lookup a MH (via MH.L.findSetter/unreflectSetter) to a final field.
>> http://hg.openjdk.java.net/jdk9/dev/jdk/file/93ced310c728/src/java.base/share/classes/java/lang/invoke/MethodHandles.java#l1516
>> Although i cannot find any such explicit mention in JavaDoc, so i guess it can be considered under the umbrella of "access checks".
> Though you can't lookup a setter for al final field directly, you can use Lookup.unreflectSetter:
>  Field f = T.class.getDeclaredField("t");
>  f.setAccessible(true);
>  MethodHandle setter = MethodHandles.lookup().unreflectSetter(f);

Oh, yes, i see now, i missed the switch to use IMPL_LOOKUP if the field is set to accessible.

> But it doesn't matter much, since MH field getters/setters are baseon on Unsafe. So, if final field value tracking works for Unsafe, it works for j.l.i as well.


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