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

[Zoltán Majó]

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
>>