[9] RFR (XS): 8072422: Change a number of flags controlling loop optimizations to 'develop'

[Vladimir Kozlov]

It is nice to have not product flags which is easy to remove :)

Clean up looks good.

Can you leave test but remove "-XX:+UnlockDiagnosticVMOptions -XX:-LoopLimitCheck" only? It has interesting code shape. 
Add comment that it was ran with "-XX:+UnlockDiagnosticVMOptions -XX:-LoopLimitCheck" to trigger problem.

Thanks,
Vladimir

On 3/31/16 1:15 AM, Zoltán Majó wrote:
> Hi Vladimir,
>
>
> thank you for your feedback!
>
> On 03/23/2016 11:58 PM, Vladimir Kozlov wrote:
>> These flags were added when I fixed long standing C2 problem with counted loops: 5091921.
>> They were added to have ability to revert back to original code if new code cause a problem.
>> Looks like the old code which executed with these flags switched off become rotten.
>>
>> Zoltan, did you find what cause the crash? Looks like product VM was used in the bug report. What result gives
>> fastdebug VM?
>
> I've tried starting different VM versions with the flag(s) off. The most frequent error I get is
>
> # Internal Error (/home/zmajo/Documents/repos/8072422/hotspot/src/share/vm/opto/loopnode.cpp:3615), pid=32727, tid=32746
> # assert(false) failed: Bad graph detected in build_loop_late
>
> So it seems that the code executed with the flags off has indeed become rotten.
>
>> Converting flags to develop will not prevent problems happening with fastdebug VM where these flags could be switched
>> off even when they are develop.
>>
>> If the problem with original code (flags are off) is something fundamental we may simple remove old code and remove
>> these flags and have only new code. 5 years already passed since 5091921 was fixed.
>
> Yes, I agree. I think it's reasonable to remove the old code.
>
> Here is the new webrev:
> http://cr.openjdk.java.net/~zmajo/8072422/webrev.01/
>
> The changes pass JPRT.
>
> I've changed the title of the bug to "Cleanup: Remove some unused flags/code in loop optimizations" to better reflect
> what the change is doing. I have kept the original title in the RFR.
>
> Thank you!
>
> Best regards,
>
>
> Zoltan
>
>>
>> Thanks,
>> Vladimir
>>
>> On 3/23/16 6:26 AM, Zoltán Majó wrote:
>>> Hi,
>>>
>>>
>>> please review the patch for 8072422.
>>>
>>> https://bugs.openjdk.java.net/browse/JDK-8072422
>>>
>>> Problem: Some flags controlling loop optimizations are currently 'diagnostic'. Even though these flags are useful
>>> mostly for compiler-related development, their value can be changed not only in
>>> fastdebug, but also also in release builds,
>>>
>>> Solution: Change the flags to 'develop'.
>>>
>>> Webrev:
>>> http://cr.openjdk.java.net/~zmajo/8072422/webrev.00/
>>>
>>> Testing:
>>> - locally built/started VM;
>>> - locally executed runtime/CommandLine/OptionsValidation/TestOptionsWithRanges.java.
>>>
>>> Thank you and best regards,
>>>
>>>
>>> Zoltan
>>>
>