RFC: How to handle >64 CPU features

askervin commented 4 years ago

Hi @klauspost,

I'd like to add AMX CPU features AMXBF16, AMXTILE, AMXINT8. However, we've hit the limit of 64 features in Flags (of type uint64).

So I'm wondering if you'd have a preference over following options, or a better idea:

Change CPUInfo.Features from uint64 to an alternative of arbitrary size (like map[int]bool, math.big.Int, bitarray) - and totally break the API.
Add "next leaf" like CPUInfo.Features2.
Add a "feature leaf" like CPUInfo.AMX that would hold subflags for this particular feature.
Add new feature structure (new API) of arbitrary size with current and new AMX features in it, and keep current CPUInfo.Features as is for backwards compatibility.
Something better?

klauspost commented 4 years ago

Yeah, a v2 has been needed for a while. #28

I think without a full rewrite I would prefer the "feature leaf" option. At least for now what makes it feasible for now. How does that sound?

askervin commented 4 years ago

That's perfectly fine. Thanks for quick answer! Closing.

klauspost / cpuid