RFR: 8166840: Synthetic bridge constructor in ArrayList$Itr blocks inlining

[Claes Redestad]

I dealt with this in isolation deliberately to ease backporting, but I 
don't have the 8u committer rights to do it myself.

/Claes

On 2016-09-28 16:27, Vitaly Davidovich wrote:
> Thanks Claes - this is an annoying one!
>
> Will it be backported to 8?
>
> On Wednesday, September 28, 2016, Claes Redestad 
> <claes.redestad at oracle.com <mailto:claes.redestad at oracle.com>> wrote:
>
>     Thanks for the quick reviews!
>
>     /Claes
>
>     On 2016-09-28 14:14, Remi Forax wrote:
>
>         yes,
>         thumb up.
>
>         Rémi
>
>
>         On September 28, 2016 1:51:18 PM GMT+02:00, Michael Haupt
>         <michael.haupt at oracle.com> wrote:
>
>             Hi Claes,
>
>             yes please. Thumbs up. :-)
>
>             Best,
>
>             Michael
>
>                 Am 28.09.2016 um 13:48 schrieb Claes Redestad
>
>             <claes.redestad at oracle.com>:
>
>                 Hi,
>
>                 as discussed recently on hotspot-compiler-dev[1],
>                 having a private
>
>             class with no default constructor can lead to C2 failing
>             to inline, due
>             to the synthetic bridge constructor using a dummy argument
>             of an
>             uninitialized class. This is really a problem in C2, as
>             well as
>             something which could ultimately be resolved by nestmates...
>
>                 However, there is an easy workaround in adding an empty
>
>             package-private constructor. In the most recently found
>             case - a
>             microbenchmark stressing MethodHandles.iteratedLoop -
>             adding this to
>             ArrayList$Itr lead to a 2.5-3x speedup.
>
>                 This is me asking nicely to do a quick-fix for this in
>
>             java.util.ArrayList$Itr now:
>
>                 Bug: https://bugs.openjdk.java.net/browse/JDK-8166840
>                 <https://bugs.openjdk.java.net/browse/JDK-8166840>
>                 Webrev:
>                 http://cr.openjdk.java.net/~redestad/8166840/webrev.01/
>                 <http://cr.openjdk.java.net/%7Eredestad/8166840/webrev.01/>
>
>                 Thanks!
>
>                 /Claes
>
>                 [1]
>
>             http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2016-September/024407.html
>             <http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2016-September/024407.html>
>
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