rust-lang / rust-lang/rustc_codegen_cranelift

Warn on opt-level > 1

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C-enhancement
Dominant language
Rust
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Forks
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Avg merge
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Merged PRs (30d)
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Description

And once the 128bit int ABI compatibility is fixed suggest using the LLVM backend for the crates that use opt-level > 1.

On multiple occasions people have found significant runtime slowdown from switching to cg_clif. Upon closer inspection it turns out that these projects are using opt-level = 3 for some dependencies or for the entire compilation.

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First steps

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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

The issue names no files, tests, or entry points. First locate how opt-level is handled and how warnings or backend recommendations are emitted; also confirm the 128-bit integer ABI compatibility prerequisite. Done means opt-level values above 1 trigger an appropriate warning and suggest LLVM for affected crates once that prerequisite is fixed.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers, performance
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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