The biggest change here is that assembly implementations are enabled by
default.
Added features:
- "pure" (Pure Rust, with no C or assembly implementations.)
Removed features:
- "c" (Now basically the default.)
Renamed features;
- "c_prefer_intrinsics" -> "prefer_intrinsics"
- "c_neon" -> "neon"
Unchanged:
- "rayon"
- "std" (Still the only feature on by default.)
This gives the assembly files the same prefix as the intrinsics files which
simplifies building when the build system should pick between the assembly and
the intrinsics files.
If AVX-512 is enabled, and the local C compiler doesn't support it, the
build is going to fail. However, if we check for this explicitly, we can
give a better error message.
Fixes https://github.com/BLAKE3-team/BLAKE3/issues/6.
The portable implementation was getting slowed down by converting back
and forth between words and bytes.
I made the corresponding change on the C side first
(12a37be8b5),
and as part of this commit I'm re-vendoring the C code. I'm also
exposing a small FFI interface to C so that blake3_neon.c can link
against portable.rs rather than blake3_portable.c, see c_neon.rs.