Invalid code generated by C2 compiler in OpenJDK 21

[David Holmes]

On 16/12/2023 3:44 am, Volker Simonis wrote:
> On Fri, Dec 15, 2023 at 1:11 PM Antoine DESSAIGNE
> <antoine.dessaigne at gmail.com> wrote:
>>
>> Thank you Volker and Andrew for your replies,
>>
>> Unfortunately, there's no hs_error generated, the code throws a
>> NullPointerException when it shouldn't.
> 
> Sorry, overlooked the "without" before "crashing due to assertions" :)
> 
>>
>> I can even reproduce it with JDK 23, I took the master of the jdk
>> repository this morning (commit b31454e3623 to be precise) and it
>> still fails.
>>
>> I cannot exclude this method from the JIT as it's used a lot in our application.
>>
>> I checked many many times the commit to be sure that I have the right
>> one and I do. It fails almost every time with 10737e168c9 [1] but it
>> never fails with its parent commit, even after 20 tests.
>>
> 
> The change looks innocent, but CCing hotstpo-runtime-dev and Coleen
> (who's the author of that change [1]). Maybe she has an idea?

Coleen is away for a while. I reviewed the change in [1] and I also 
cannot see how it could affect anything to do with the JIT.

 From the original mail on compiler-dev:

 >  A valued local variable (effectively final) has its value removed

What does this mean???

David
-----

> Is your code doing a lot of dynamic class loading and/or bytecode
> instrumentation/rewriting?
> 
>> [1] https://github.com/openjdk/jdk/commit/10737e168c967a08e257927251861bf2c14795ab
>>
>> Le ven. 15 déc. 2023 à 12:37, Andrew Haley
>> <aph-open at littlepinkcloud.com> a écrit :
>>>
>>> On 12/15/23 10:20, Antoine DESSAIGNE wrote:
>>>> Do you have an idea of why this is happening? Do you know what test I
>>>> can run?
>>>
>>> First, try to reproduce it with JDK 22 preview.
>>>
>>> If you can't provide a reproducer, it's likely that no one will be
>>> able to fix it now, and you'll have to wait until it gets fixed.
>>>
>>> Try: '-XX:CompileCommand=exclude,foo.bar.baz.Classname::badMethodName'
>>>
>>> --
>>> Andrew Haley  (he/him)
>>> Java Platform Lead Engineer
>>> Red Hat UK Ltd. <https://www.redhat.com>
>>> https://keybase.io/andrewhaley
>>> EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671
>>>