JDK 9 rampdown and a plea for mercy (original) (raw)

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.

Thanks,

Andrew.

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