JDK 9 rampdown and a plea for mercy
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.
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