RFR (S) 8220656 : ARM32: -XX:MaxVectorSize=16 makes SIGILL

[Boris Ulasevich]

Hi David,

Thanks for review! I added a warning and fixed the drop back value:
http://cr.openjdk.java.net/~bulasevich/8220656/webrev.02

regards,
Boris

On 15.05.2019 4:16, David Holmes wrote:
> On 15/05/2019 6:48 am, dean.long at oracle.com wrote:
>> Looks fine, but you might want to print a warning if you override the 
>> user's choice.
> 
> I would normally agree, but in this case the following code will already 
> silently overwrite the user's choice in some cases:
> 
>   281   if (MaxVectorSize > 16) {
>   282     FLAG_SET_DEFAULT(MaxVectorSize, 8);
>   283   }
> 
> and I find it odd that it drops it back to 8 rather than taking the 
> upper-limit of 16.
> 
> To me the first problem here is that MaxVectorSize should be a pd_global 
> so each platform can just set the right default to begin with, and set a 
> correct allowed range for that platform. In fact with a constraint 
> function it could even incorporate the has_simd() check. But that's 
> getting a bit beyond the current fix.
> 
> I can't see any non-convoluted way to print a warning under all the 
> right circumstances, so I'll leave it to Boris to decide what to do 
> here. I don't think a warning is essential.
> 
> Cheers,
> David
> 
>> dl
>>
>> On 5/14/19 8:39 AM, Boris Ulasevich wrote:
>>> Hi all,
>>>
>>> Please review a simple change to prevent VLD1/VST1 instructions 
>>> generation on ARM32 processor without SIMD support. The change 
>>> overrides MaxVectorSize option set up by user to a value acceptable 
>>> by the hardware.
>>>
>>> https://bugs.openjdk.java.net/browse/JDK-8220656
>>> http://cr.openjdk.java.net/~bulasevich/8220656/webrev.01/
>>>
>>> thanks,
>>> Boris
>>