[9] RFR(S): 8072398: assert fails in L1RGenerator::increment_event_counter_impl

[Zoltán Majó]

Hi Igor,


thank you for the feedback.


On 02/05/2015 09:59 PM, Igor Veresov wrote:
> The code looks good. But I think the comment about CompileThresholdScaling == 0 being equivalent to -Xint is bit misleading. The VM does not become interpreter-only, does it?

It does.

The reason is that CompileThreshold==0 has been historically equivalent 
to -Xint (see lines 3488-3493 in arguments.cpp). 
CompileThresholdScaling==0.0 scales down CompileThreshold to 0, so we 
decided to keep functionality consistent and make 
CompileThresholdScaling equivalent to -Xint as well when we introduced 
the CompileThresholdScaling flag in 8059604.

I hope this makes sense.

Thank you!

Best regards,


Zoltan



>
> igor
>
>> On Feb 5, 2015, at 8:18 AM, Zoltán Majó <zoltan.majo at oracle.com> wrote:
>>
>> Hi,
>>
>>
>> please review the following small patch.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8072398
>>
>> Problem: The reported assert is triggered because the method LIRGenerator::increment_event_counter_impl is called with parameter 'frequency' set to -1.
>>
>> The value originates from Arguments::scaled_freq_log(): If both variables 'freq_log' and 'scale' are small, 'scaled_freq' can become 0 and the function log2_intptr returns -1 for the value 0. A similar problem appears if freq_log == 0.
>>
>>
>> Solution:
>>
>> To treat the above mentioned cases graciously, this patch:
>>
>> - Changes Arguments::scaled_freq_log() and Arguments::scaled_compile_threshold() to allow scaling the frequency/threshold by 0.0 and return 0.0 in these cases without calling log2_intptr().
>>
>> - Adds a new condition to Arguments::set_tiered_flags(): Threshold values are *not scaled* if 'CompileThresholdScaling' is 0.0 (behavior equivalent to -Xint). Previously, this functionality was encoded in scaled_freq_log() and scaled_compile_threshold(). Handling this case in set_tiered_flags() results in clearer code.
>>
>> - Improves comments.
>>
>>
>> Webrev: http://cr.openjdk.java.net/~zmajo/8072398/webrev.00/
>>
>> Testing:
>> - manual testing with failing test cases
>> - compiler/arguments/CheckCompileThresholdScaling.java
>> - JPRT
>>
>> Thank you and best regards,
>>
>>
>> Zoltan
>>