crypto/sha512: arm optimizations not implemented

[gopherbot]

by jeromyj:

sha family hash functions on ARM architectures are quite slow, there is an
implementation of sha512 (and sha1) in libgcrypt that has assembly optimized code for
ARM Neon. It would be really nice to have something similar implemented into the Go
standard library.

[davecheney]

Comment 1:

It would be great to have an assembly implementation of those crypto functions for arm.
There are two issues.
1. not all supported platforms support neon, so that means a non neon version would have
to be included and detected at runtime.
2. i am not a lawyer, and don't pretend to play one on tv, but the licence for libgcrypt
does not appear to be compatible with the Go licence.

Labels changed: added release-none, repo-main, arch-arm.

Status changed to Accepted.

[gopherbot]

Comment 2 by jeromyj:

Couldnt the difference between neon code and code without be checked at compile time?
using a "*_neon.s" type file exension? Ive not looked too far into how the platform
specifiers work, so maybe thats not possible.

[minux]

Comment 3:

subarch build tag has been proposed before, but rejected (?).
even if we can select code based on subarch, you might still want to two copies of the
code
to run systems without NEON.

[heisen-li]

cryto/sha512: Will the assembly submitted to arm64 now be accepted?