Re: clang bug affecting greenfly

On Mon, Mar 30, 2026, at 2:39 AM, John Naylor wrote:
> [new subject]
>
> On Sat, Mar 28, 2026 at 3:22 AM Greg Burd <greg(at)burd(dot)me> wrote:
>
>> 0001 - This is a bug fix for DES/RISC-V/Clang DES initialization.
>>
>> ------> Join me in "the rabbit hole" on this issue if you care to...
>>
>> The existing software DES (as shown by the build-farm animal "greenfly" [1]) fails because Clang 20 has an auto-vectorization bug that we trigger in the DES initialization code (des_init() function), not the DES encryption algorithm itself.
>
>> [disable vectorization entirely]
>> While that might also fix the other intermittent bug we'd been seeing on greenfly (not tested) disablnig all RVV optimizations seems to heavy handed to me.
>
> The first thing I notice is that not very long ago the buildfarm had 3
> gcc RISC-V members, but not anymore. If you care about having coverage
> for this hardware, I'd suggest picking up gcc again if that's still
> working, and wait and see about clang. Clang has shipped broken code
> generation for obscure platforms in the past, and it seems here we're
> not even sure of the extent of the breakage.

Hey John,

All fair points. I've changed greenfly to use GCC 13.3.0, thanks for the suggestion.

> --
> John Naylor
> Amazon Web Services

best.

-greg