RFR: 8240370: Provide Intel JCC Erratum opt-out

[Erik Österlund]

Hi Claes,

On 2020-03-03 13:48, Claes Redestad wrote:
> Hi Erik,
>
> thanks for adding this!
>
> I think you can move the flag definition from globals.hpp to 
> globals_x86.hpp and leave the other platforms alone for this. There
> are a number of x86-specific flags there already.

That makes sense. I took this chance to refine the name of the flag to 
IntelJccErratumMitigation as well.

New webrev: http://cr.openjdk.java.net/~eosterlund/8240370/webrev.01/

Thanks,
/Erik

> /Claes
>
> On 2020-03-03 13:23, Erik Österlund wrote:
>> Hi,
>>
>> Today, the Intel JCC Erratum mitigation is automatically enabled when 
>> running on an affected machine.
>> While it is strongly recommended that customers run code in 
>> environments with the micro code updates
>> provided by Intel to mitigate the erratum, and hence are probably 
>> almost always better off with the
>> mitigation, there could be value in being able to opt out to analyze 
>> the performance characteristics
>> of an application, as a diagnostic option.
>>
>> This patch adds a diagnostic option that allows you to opt out with: 
>> -XX:-IntelJccErratum
>>
>> Webrev:
>> http://cr.openjdk.java.net/~eosterlund/8240370/webrev.00/
>>
>> Bug:
>> https://bugs.openjdk.java.net/browse/JDK-8240370
>>
>> Thanks,
>> /Erik