Claire Xen  🏳️‍⚧️ 🏳️‍🌈 🧙🏻‍♀️ BLM  🏴 🚩

What are your thoughts on https://gist.github.com/erincandescent/8a10eeeea1918ee4f9d9982f7618ef68 … ?

Roughly half is moderately serious, half is pointless pedantry about things that don't matter or complaints about good choices.

Atomics being optional is absolutely wrong. Non-SMP core can implement lr/sc trivially and should be required to. Likewise for mul but not quite as serious since it *can* be emulated in sw.

The MUL thing is silly because even if the HW ends up doing the same thing as SW in some cases, it’s always at least as efficient, and usually much more. And it’s such a common operation that not having it in base badly fractures binaries—you *have* to use it when available.

If you aren’t going to put MUL and barebones atomics in the base ISA, you barely have an ISA; you need to have at least two versions of everything anyway.

No, you still have the ability for baseline ISA binaries for the weak implementations to run on a proper implementation with mul.

Yeah, it's possible, but it's catastrophically bad for performance and a big waste of energy.

Not with shared libs where the mul func could just be mul insn on the more capable machine. But yeah mul should just be in baseline ISA.