ARM - Aarch64

[DaanA32]

Hi Ragnaroek,

I've implemented the sse.rs and most of the m128d and m128i for aarch64, unfortunately the Raspberry Pi 4B doesn't have the crypto extension.
Therefore I was unable to verify if the AESE instruction works, although it does compile when using RUSTFLAGS='-C target_feature=+aes'.
I was wondering what your preferred way of seperating the different architectures would be.

https://github.com/DaanA32/mithril/tree/aarch64

[Ragnaroek]

Hi DaanA32,

nice things in your commit!

To be honest, I haven't put much thought into a support for a different architecture. I'm still working on the x86 implementation and this will take some time.
But this is definitely something I want to do in the future. Maybe I would go with the cfg feature of Rust.
Also a pure software based implementation as a fallback would be nice, to support CPUs without the AES extension (like the Raspberry you mentioned).
But this would purely for freedom of mining reasons (everybody with a CPU should be able to mine Monero). I'm currently focusing on performance and I guess this is something not in the near future.

[DaanA32]

I would suggest either using cnf_if for the aes part of m128i
eg:

pub fn aesenc(&self, key: m128i) -> m128i {
    cnf_if {
        if #[cfg(target_feature='crypto')] {
            // HARDWARE IMPL
        } else {
            // SOFTWARE IMPL
        }
    }
}

Or a trait based approach

#[cfg(target_feature='crypto')]
trait Aes for m128i {
    // HARDWARE IMPL
}

#[cfg(not(target_feature='crypto'))]
trait Aes for m128i {
    // SOFTWARE IMPL
}