> Am 20.12.2024 um 17:49 schrieb Palmer Dabbelt <pal...@rivosinc.com>:
>
> On Thu, 19 Dec 2024 15:01:26 PST (-0800), jeffreya...@gmail.com wrote:
>>
>>
>>> On 12/19/24 3:08 PM, Palmer Dabbelt wrote:
>>>
>>> I agree lacking B and V makes us very clearly uncompetitive in the space
>>> where these sort of things matter (ie, binary compatible distros and
>>> long term stability type things) -- the gap is just too big to close by
>>> doing clever things in the hardware. Maybe just B and V isn't enough,
>>> it's hard to tell, but lacking them seems pretty clearly uncompetitive.
>>>
>>> I'm not sure B is so scary on the SW side of things, it's been mostly
>>> performance issues we've been fixing. V is huge, though, and we've
>>> generally found a bunch of V-related functional codegen bugs. Without
>>> reliable hardware to test against (and do distro builds and such) it
>>> just seems premature to declare that being as stable as the other ports
>>> on the list.
>> It wouldn't take much to push me into agreeing to B -- it's not scary in
>> any way. There's just notable systems out there that don't implement B,
>> but I wouldn't mind leaving them behind for this change.
>>
>> V has real performance concerns. I haven't tested it performance-wise
>> on the BPI recently, but when I last did the general rule of thumb was
>> the more vector you did, the worse it performed *especially* for FP.
>
> Yep. TBH that's actually my biggest worry here: it might be that just V
> isn't enough, which means we have another few generations of HW before all
> the V add-on extensions coalesce into something that's widely implemented.
> I'm not really sure there, though -- the HW guys can be pretty clever so
> maybe V gets us close enough to be interesting.
Note we usually do Not restrict ports to a subset of the ISA, iff extensions
are not ready for prime time Id suggest to instead never enable those by
default.
Note we might want to start documenting primary/secondary _hosts_ vs targets as
well. For a native compiler that might imply a select default ISA.
Richard
>>
>> jeff
