rust/README.md

This crate is regularly synced with its mirror in the rustc repo at compiler/rustc_smir.

We use git subtree for this to preserve commits and allow the rustc repo to edit these crates without having to touch this repo. This keeps the crates compiling while allowing us to independently work on them here. The effort of keeping them in sync is pushed entirely onto us, without affecting rustc workflows negatively. This may change in the future, but changes to policy should only be done via a compiler team MCP.

Instructions for syncing

Updating this repository

In the rustc repo, execute

git subtree push --prefix=compiler/rustc_smir url_to_your_fork_of_project_stable_mir some_feature_branch

and then open a PR of your some_feature_branch against https://github.com/rust-lang/project-stable-mir

Updating the rustc library

First we need to bump our stack limit, as the rustc repo otherwise quickly hits that:

ulimit -s 60000

Maximum function recursion depth (1000) reached

Then we need to disable dash as the default shell for sh scripts, as otherwise we run into a hard limit of a recursion depth of 1000:

sudo dpkg-reconfigure dash

and then select No to disable dash.

Patching your git worktree

The regular git worktree does not scale to repos of the size of the rustc repo. So download the git-subtree.sh from https://github.com/gitgitgadget/git/pull/493/files and run

sudo cp --backup /path/to/patched/git-subtree.sh /usr/lib/git-core/git-subtree
sudo chmod --reference=/usr/lib/git-core/git-subtree~ /usr/lib/git-core/git-subtree
sudo chown --reference=/usr/lib/git-core/git-subtree~ /usr/lib/git-core/git-subtree

Actually doing a sync

In the rustc repo, execute

git subtree pull --prefix=compiler/rustc_smir https://github.com/rust-lang/project-stable-mir smir

Note: only ever sync to rustc from the project-stable-mir's smir branch. Do not sync with your own forks.

Then open a PR against rustc just like a regular PR.