lighthouse/consensus/tree_hash
Michael Sproul 2c691af95b Use hardware acceleration for SHA256 (#2426)
## Proposed Changes

Modify the SHA256 implementation in `eth2_hashing` so that it switches between `ring` and `sha2` to take advantage of [x86_64 SHA extensions](https://en.wikipedia.org/wiki/Intel_SHA_extensions). The extensions are available on modern Intel and AMD CPUs, and seem to provide a considerable speed-up: on my Ryzen 5950X it dropped state tree hashing times by about 30% from 35ms to 25ms (on Prater).

## Additional Info

The extensions became available in the `sha2` crate [last year](https://www.reddit.com/r/rust/comments/hf2vcx/ann_rustcryptos_sha1_and_sha2_now_support/), and are not available in Ring, which uses a [pure Rust implementation of sha2](https://github.com/briansmith/ring/blob/main/src/digest/sha2.rs). Ring is faster on CPUs that lack the extensions so I've implemented a runtime switch to use `sha2` only when the extensions are available. The runtime switching seems to impose a miniscule penalty (see the benchmarks linked below).
2021-07-12 08:47:01 +00:00
..
examples Altair consensus changes and refactors (#2279) 2021-07-09 06:15:32 +00:00
src Use hardware acceleration for SHA256 (#2426) 2021-07-12 08:47:01 +00:00
Cargo.toml Altair consensus changes and refactors (#2279) 2021-07-09 06:15:32 +00:00