rust/library/stdarch/README.md

stdarch - Rust's standard library SIMD components

Crates

This repository contains two main crates:

• core_arch implements core::arch - Rust's core library architecture-specific intrinsics, and

• std_detect implements std::detect - Rust's standard library run-time CPU feature detection.

The std::simd component now lives in the packed_simd_2 crate.

Synchronizing josh subtree with rustc

This repository is linked to rust-lang/rust as a josh subtree. You can use the following commands to synchronize the subtree in both directions.

You'll need to install josh-proxy locally via

cargo install josh-proxy --git https://github.com/josh-project/josh --tag r24.10.04

Older versions of josh-proxy may not round trip commits losslessly so it is important to install this exact version.

Pull changes from rust-lang/rust into this repository

1. Checkout a new branch that will be used to create a PR into rust-lang/stdarch
2. Run the pull command

   cargo run --manifest-path josh-sync/Cargo.toml rustc-pull
   

3. Push the branch to your fork and create a PR into stdarch

Push changes from this repository into rust-lang/rust

NOTE: If you use Git protocol to push to your fork of rust-lang/rust, ensure that you have this entry in your Git config, else the 2 steps that follow would prompt for a username and password:

[url "git@github.com:"]
insteadOf = "https://github.com/"

1. Run the push command to create a branch named <branch-name> in a rustc fork under the <gh-username> account

   cargo run --manifest-path josh-sync/Cargo.toml rustc-push <branch-name> <gh-username>
   

2. Create a PR from <branch-name> into rust-lang/rust

Minimal git config

For simplicity (ease of implementation purposes), the josh-sync script simply calls out to system git. This means that the git invocation may be influenced by global (or local) git configuration.

You may observe "Nothing to pull" even if you know rustc-pull has something to pull if your global git config sets fetch.prunetags = true (and possibly other configurations may cause unexpected outcomes).

To minimize the likelihood of this happening, you may wish to keep a separate minimal git config that only has [user] entries from global git config, then repoint system git to use the minimal git config instead. E.g.

GIT_CONFIG_GLOBAL=/path/to/minimal/gitconfig GIT_CONFIG_SYSTEM='' cargo run --manifest-path josh-sync/Cargo.toml -- rustc-pull