A guide to how rustc works and how to contribute to it.
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Matthias Krüger ace7a22f2f
Rollup merge of #135581 - EnzymeAD:refactor-codgencx, r=oli-obk
Separate Builder methods from tcx

As part of the autodiff upstreaming we noticed, that it would be nice to have various builder methods available without the TypeContext, which prevents the normal CodegenCx to be passed around between threads.
We introduce a SimpleCx which just owns the llvm module and llvm context, to encapsulate them.
The previous CodegenCx now implements deref and forwards access to the llvm module or context to it's SimpleCx sub-struct. This gives us a bit more flexibility, because now we can pass (or construct) the SimpleCx in locations where we don't have enough information to construct a CodegenCx, or are not able to pass it around due to the tcx lifetimes (and it not implementing send/sync).

This also introduces an SBuilder, similar to the SimpleCx. The SBuilder uses a SimpleCx, whereas the existing Builder uses the larger CodegenCx. I will push updates to make  implementations generic (where possible) to be implemented once and work for either of the two. I'll also clean up the leftover code.

`call` is a bit tricky, because it requires a tcx, I probably need to duplicate it after all.

Tracking:

- https://github.com/rust-lang/rust/issues/124509
2025-01-24 23:25:42 +01:00
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README.md

CI

This is a collaborative effort to build a guide that explains how rustc works. The aim of the guide is to help new contributors get oriented to rustc, as well as to help more experienced folks in figuring out some new part of the compiler that they haven't worked on before.

You can read the latest version of the guide here.

You may also find the rustdocs for the compiler itself useful. Note that these are not intended as a guide; it's recommended that you search for the docs you're looking for instead of reading them top to bottom.

For documentation on developing the standard library, see std-dev-guide.

Contributing to the guide

The guide is useful today, but it has a lot of work still to go.

If you'd like to help improve the guide, we'd love to have you! You can find plenty of issues on the issue tracker. Just post a comment on the issue you would like to work on to make sure that we don't accidentally duplicate work. If you think something is missing, please open an issue about it!

In general, if you don't know how the compiler works, that is not a problem! In that case, what we will do is to schedule a bit of time for you to talk with someone who does know the code, or who wants to pair with you and figure it out. Then you can work on writing up what you learned.

In general, when writing about a particular part of the compiler's code, we recommend that you link to the relevant parts of the rustc rustdocs.

Build Instructions

To build a local static HTML site, install mdbook with:

> cargo install mdbook mdbook-linkcheck2 mdbook-toc mdbook-mermaid

and execute the following command in the root of the repository:

> mdbook build --open

The build files are found in the book/html directory.

We use mdbook-linkcheck2 to validate URLs included in our documentation. Link checking is not run by default locally, though it is in CI. To enable it locally, set the environment variable ENABLE_LINKCHECK=1 like in the following example.

$ ENABLE_LINKCHECK=1 mdbook serve

Table of Contents

We use mdbook-toc to auto-generate TOCs for long sections. You can invoke the preprocessor by including the <!-- toc --> marker at the place where you want the TOC.

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.

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/rustc-dev-guide
  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 rustc-dev-guide

Push changes from this repository into rust-lang/rust

  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