JDK 9 rampdown and a plea for mercy

Andrew Haley aph at redhat.com
Fri Mar 10 14:55:30 UTC 2017

As you may remember, I did some work on ByteBuffers a couple of years
ago.  At the time the generated code was sparklingly good, and I was
happy the job was done well.  Yesterday I looked at the code we are
generating in JDK9, and was horrified to see that it now is a steaming
pile of ordure.  It might be, of course, that I am mistaken about it
being better before, but I really don't think so: I wouldn't have let
it go out like that.  I suppose it was just good luck (or a C2 bug)
that great code was generated.

The full gory details are in
https://bugs.openjdk.java.net/browse/JDK-8176513, but the bottom line
is that unless this regression is fixed all my ByteBuffer work will
have been for naught.

Roland has had a look at what is happening, and he thinks that this
can be fixed fairly quickly: he already has a working patch.  Is there
any way that we can get it in?

One thing for the future: we need to keep an eye on code quality
regressions.  I'm not sure how, exactly.  And perhaps I need to
remember that just because C2 generates good code today, it might not
generate good code tomorrow.



More information about the hotspot-dev mailing list