compiler/rustc_smir/README.md

   1 This crate is regularly synced with its mirror in the rustc repo at `compiler/rustc_smir`.
   2
   3 We use `git subtree` for this to preserve commits and allow the rustc repo to
   4 edit these crates without having to touch this repo. This keeps the crates compiling
   5 while allowing us to independently work on them here. The effort of keeping them in
   6 sync is pushed entirely onto us, without affecting rustc workflows negatively.
   7 This may change in the future, but changes to policy should only be done via a
   8 compiler team MCP.
   9
  10 ## Instructions for working on this crate locally
  11
  12 Since the crate is the same in the rustc repo and here, the dependencies on rustc_* crates
  13 will only either work here or there, but never in both places at the same time. Thus we use
  14 optional dependencies on the rustc_* crates, requiring local development to use
  15
  16 ```
  17 cargo build --no-default-features -Zavoid-dev-deps
  18 ```
  19
  20 in order to compile successfully.
  21
  22 ## Instructions for syncing
  23
  24 ### Updating this repository
  25
  26 In the rustc repo, execute
  27
  28 ```
  29 git subtree push --prefix=compiler/rustc_smir url_to_your_fork_of_project_stable_mir some_feature_branch
  30 ```
  31
  32 and then open a PR of your `some_feature_branch` against https://github.com/rust-lang/project-stable-mir
  33
  34 ### Updating the rustc library
  35
  36 First we need to bump our stack limit, as the rustc repo otherwise quickly hits that:
  37
  38 ```
  39 ulimit -s 60000
  40 ```
  41
  42 #### Maximum function recursion depth (1000) reached
  43
  44 Then we need to disable `dash` as the default shell for sh scripts, as otherwise we run into a
  45 hard limit of a recursion depth of 1000:
  46
  47 ```
  48 sudo dpkg-reconfigure dash
  49 ```
  50
  51 and then select `No` to disable dash.
  52
  53
  54 #### Patching your `git worktree`
  55
  56 The regular git worktree does not scale to repos of the size of the rustc repo.
  57 So download the `git-subtree.sh` from https://github.com/gitgitgadget/git/pull/493/files and run
  58
  59 ```
  60 sudo cp --backup /path/to/patched/git-subtree.sh /usr/lib/git-core/git-subtree
  61 sudo chmod --reference=/usr/lib/git-core/git-subtree~ /usr/lib/git-core/git-subtree
  62 sudo chown --reference=/usr/lib/git-core/git-subtree~ /usr/lib/git-core/git-subtree
  63 ```
  64
  65 #### Actually doing a sync
  66
  67 In the rustc repo, execute
  68
  69 ```
  70 git subtree pull --prefix=compiler/rustc_smir https://github.com/rust-lang/project-stable-mir smir
  71 ```
  72
  73 Note: only ever sync to rustc from the project-stable-mir's `smir` branch. Do not sync with your own forks.
  74
  75 Then open a PR against rustc just like a regular PR.