Fix features

[nazar-pc]

First commit removes features of blst that shouldn't be necessary (and shouldn't exist in blst in the first place) as described in #233 (comment).

Second commit fixes regression from #232 that caused hex dependency to pull standard library in (annoyingly wasm32-unknown-unknown does have a standard library, although an incomplete one, so it didn't cause CI failure).

[belijzajac]

This breaks the release action that runs on the main branch:

https://github.com/sifraitech/rust-kzg/blob/a96d615365ec6e91c02256e195e4ac5c9f10bdca/.github/workflows/release.yml#L38

[nazar-pc]

Yeah, will fix, do you otherwise agree it is better to remove those features though or should provide more details?

[sauliusgrigaitis]

AFAIK runtime detection costs a bit of performance, can't recall if is it noticeable. If that's true, then we may leave option for user to force settings instead of runtime detection.

[belijzajac]

c-kzg-4844 removed features for portable and force-adx ethereum/c-kzg-4844#338, so maybe we should too?

[nazar-pc]

AFAIK runtime detection costs a bit of performance, can't recall if is it noticeable. If that's true, then we may leave option for user to force settings instead of runtime detection.

There is no runtime cost, it is all decided at compile time. blst will enable support for necessary features based on the target platform, so RUSTFLAGS="-C target-cpu=x86-64-v2" will not use ADX and RUSTFLAGS="-C target-cpu=skylake" will.

blst is essentially infecting all downstream projects with its features, but at least they support target-cpu for Rust since supranational/blst@9bf52f8

[sauliusgrigaitis]

Interesting, I thought they added runtime detection recently supranational/blst#10.

[nazar-pc]

Looks like they are only used in portable builds, so compiling without selecting portable flag should give you the same result as before.

[nazar-pc]

Is there anything else I should do here? With this we should finally be able to use upstream version of this library at Subspace Network, had to patch it all along prior to this.

[sauliusgrigaitis]

Seems it broke the build. I'm reverting.

[nazar-pc]

Looks like -C target-cpu=x86-64 needs to be applied at a different position in the command.