Re: target/ppc: bug in optimised vsl/vsr implementation?

["Alex Bennée" <alex.bennee@linaro.org>]

Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk> writes:

> On 28/09/2019 18:45, Aleksandar Markovic wrote:
>
> Hi Aleksandar,
>
> Thanks for taking a look at this!
>
>> Mark and Paul (and Stefan),
>>
>> Thanks for spotting this and pinpointing the culprit commit. I guess Stefan is going
>> to respond soon, but, in the meantime, I took a look at the commit in question:
>>
>> https://github.com/qemu/qemu/commit/4e6d0920e7547e6af4bbac5ffe9adfe6ea621822
>>
>> I don't have at the moment any dev/test environment handy, but I did manual
>> inspection of the code, and here is what I found (in order of importance, perceived
>> by me):
>>
<snip>
>
>> Given all these circumstances, perhaps the most reasonable solution would be to
>> revert the commit in question, and allow Stefan enough dev and test time to hopefully
>> submit a new, better, version later on.
>
> Given that it has been broken for 3 months now, I don't think we're in any major rush
> to revert ASAP. I'd prefer to give Stefan a bit more time first since he does report
> some substantial speed improvements from these new implementations.

Is the denbcdq instruction exposed in any standard float operations?
Once this is fixed it would be worth adding a testcase (either ppc64
specific or multiarch) so protect it from regression in the future.

>
>
> ATB,
>
> Mark.


--
Alex Bennée