| commit | 36b4b36dee6a67648eeb4d7fc4365db5276f4e0a | [log] [tgz] |
|---|---|---|
| author | bors <bors@rust-lang.org> | Wed Aug 13 04:18:43 2025 +0000 |
| committer | bors <bors@rust-lang.org> | Wed Aug 13 04:18:43 2025 +0000 |
| tree | 672f89f052fc31cf6ae17ceeb5c03372db48be55 | |
| parent | 49bf3e601ea77aff6545801239ef3f6c728cf184 [diff] | |
| parent | f81b8b765829df5d828600758ce91e6a81cfb0d8 [diff] |
Auto merge of #145093 - nikic:dead-on-return, r=nnethercote Set dead_on_return attribute for indirect arguments Set the dead_on_return attribute (added in LLVM 21) for arguments that are passed indirectly, but not byval. This indicates that the value of the argument on return does not matter, enabling additional dead store elimination. From LangRef: > This attribute indicates that the memory pointed to by the argument is dead upon function return, both upon normal return and if the calls unwinds, meaning that the caller will not depend on its contents. Stores that would be observable either on the return path or on the unwind path may be elided. > > Specifically, the behavior is as-if any memory written through the pointer during the execution of the function is overwritten with a poison value upon function return. The caller may access the memory, but any load not preceded by a store will return poison. > > This attribute does not imply aliasing properties. For pointer arguments that do not alias other memory locations, noalias attribute may be used in conjunction. Conversely, this attribute always implies dead_on_unwind. > > This attribute cannot be applied to return values. This fixes parts of https://github.com/rust-lang/rust/issues/96497.
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.
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.
To build a local static HTML site, install mdbook with:
cargo install mdbook mdbook-linkcheck2 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
Each page has a TOC that is automatically generated by pagetoc.js. There is an associated pagetoc.css, for styling.
This repository is linked to rust-lang/rust as a josh subtree. You can use the rustc-josh-sync tool to perform synchronization.
You can find a guide on how to perform the synchronization here.