Contributing to Rust

notes.md

Contribution Workflows

• Doc-only changes:

  ./x.py doc --stage=0 src/libstd

• libstd-only changes:

  ./x.py check --stage=0 src/libstd

• Run tests on individual crate

  cargo test -p

• Always use --stage=1

  ./x.py test --stage=1

• Tidy checks only

  ./x.py test --stage=0 src/tools/tidy

Where to start?

Check the issue tracker:

• E-easy / E-needs-test
• C-cleanup

Ask:

• On Zulip or Discord
• Specific working groups

Compiler Performance

• There's a working group for that!
• Pathological cases: Open an issue
• Tooling:
  • perf record
  • cargo flamegraph
  • rustc -Zself-profile – has working group WG-self-profile

MIR optimizations

Parse Code -> AST -> HIR -> MIR -> LLVM IR -> Machine Code

• WG-mir-opt
• Passes:
  • SimplifyCfg, instcombine, simplifyX (most on by default)
  • Constant Propagation (on by default)
  • Inliner (working on turning it on by default)
  • Copy Propagation / NRVO (WIP)
• Other work:
  • Polymorphization to avoid instantiating generic MIR bodies more often than needed
  • Other ideas around making generics more efficient