On 4/29/20 2:30 PM, fo...@univ-mlv.fr wrote:
I think the problem with perf might be caused by the fact that while the
array is now a constant, the elements are not (the array is mutable
after all). For fields you can fix this by using @Stable, but not for CP
entries :)
I think you're right,
Ah, I missed that!
I think what could work is; rather than ldc'ing the array, and then
looking up the values with 'normal' Java code, we could have another
dynamic constant that does the the array lookup as well. Then the
resolved value is stored in a separate CP slot as a true constant. We
probably want to have a bootstrap method in ConstantBootstraps that can
do an arbitrary array lookup given an array and an index for that.
FYI. I'm exploring is `classDataAt` to get a specific element/entry
from a class data of immutable List or Map.
[1]
http://cr.openjdk.java.net/~mchung/jdk15/webrevs/8239578/webrev.00/src/java.base/share/classes/java/lang/invoke/MethodHandles.java.frames.html
Not going down this road, sorry :-)
I've added the changes (see attached patch), and all benchmarks are
several order of magnitude slower. I think this is mostly caused by
the fact that the addOffset/multiplyOffset handle are no longer
cached in static constants.
While I understand that there might be better ways to generate the
code, I'd strongly prefer to leave the code as per last iteration. I
can't honestly see in which way having 3-4 static fields in a
synthetic VarHandle class is going to hurt (but I can see how much it
hurts by not having said fields).
I agree to keep the code per last iteration. We can always improve this
in the future with performance measurement.
Mandy
