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diff --git a/compiler/rustc_smir/README.md b/compiler/rustc_smir/README.md new file mode 100644 index 000000000..ae49098dd --- /dev/null +++ b/compiler/rustc_smir/README.md @@ -0,0 +1,75 @@ +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 working on this crate locally + +Since the crate is the same in the rustc repo and here, the dependencies on rustc_* crates +will only either work here or there, but never in both places at the same time. Thus we use +optional dependencies on the rustc_* crates, requiring local development to use + +``` +cargo build --no-default-features -Zavoid-dev-deps +``` + +in order to compile successfully. + +## 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. |