The discussion centers on Relax, an AI-generated JIT compiler for Rust that reduces build times by deferring the borrow checker, with users debating whether this trade-off is viable compared to traditional caching tools. Critics argue that long build times stem from dependency bloat and trait solving rather than the borrow checker itself, while proponents highlight the tool's utility for rapid iteration and AI-assisted development.
38 readable replies · Supporting reply 1 · Supporting reply 2 · Supporting reply 3 · Supporting reply 4rust-lang
rustc_codegen_cranelift
Rust2024–2026
rust-lang / rustc_codegen_cranelift
rustc_codegen_cranelift
Cranelift based backend for rustc
12Distinct people
12Mentions
0Explicit recommenders
2.2KGitHub stars
What to know before exploring
What it is
Cranelift based backend for rustc
GitHub
Where it is used
No documented product use was verified in the last source check.
What people are saying
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Also in these discussions
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This week on Hacker News
Nov 7–Nov 14 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/14/2026, 12:24:10 PM UTC.
Mentions over time
HN mentions by month12 dated mentions
Observed mentions: 2024-03-16 12:08:08 UTC to 2026-10-01 15:30:02 UTC.
Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.
View mention counts and date ranges
| Period | Start (UTC) | End (exclusive, UTC) | Mentions | Submissions | Comments |
|---|---|---|---|---|---|
| Mar 2024 | 2024-03-01 00:00:00 UTC | 2024-04-01 00:00:00 UTC | 3 | 0 | 3 |
| Apr 2024 | 2024-04-01 00:00:00 UTC | 2024-05-01 00:00:00 UTC | 0 | 0 | 0 |
| May 2024 | 2024-05-01 00:00:00 UTC | 2024-06-01 00:00:00 UTC | 0 | 0 | 0 |
| Jun 2024 | 2024-06-01 00:00:00 UTC | 2024-07-01 00:00:00 UTC | 0 | 0 | 0 |
| Jul 2024 | 2024-07-01 00:00:00 UTC | 2024-08-01 00:00:00 UTC | 1 | 0 | 1 |
| Aug 2024 | 2024-08-01 00:00:00 UTC | 2024-09-01 00:00:00 UTC | 0 | 0 | 0 |
| Sep 2024 | 2024-09-01 00:00:00 UTC | 2024-10-01 00:00:00 UTC | 0 | 0 | 0 |
| Oct 2024 | 2024-10-01 00:00:00 UTC | 2024-11-01 00:00:00 UTC | 0 | 0 | 0 |
| Nov 2024 | 2024-11-01 00:00:00 UTC | 2024-12-01 00:00:00 UTC | 0 | 0 | 0 |
| Dec 2024 | 2024-12-01 00:00:00 UTC | 2025-01-01 00:00:00 UTC | 0 | 0 | 0 |
| Jan 2025 | 2025-01-01 00:00:00 UTC | 2025-02-01 00:00:00 UTC | 0 | 0 | 0 |
| Feb 2025 | 2025-02-01 00:00:00 UTC | 2025-03-01 00:00:00 UTC | 0 | 0 | 0 |
| Mar 2025 | 2025-03-01 00:00:00 UTC | 2025-04-01 00:00:00 UTC | 0 | 0 | 0 |
| Apr 2025 | 2025-04-01 00:00:00 UTC | 2025-05-01 00:00:00 UTC | 0 | 0 | 0 |
| May 2025 | 2025-05-01 00:00:00 UTC | 2025-06-01 00:00:00 UTC | 0 | 0 | 0 |
| Jun 2025 | 2025-06-01 00:00:00 UTC | 2025-07-01 00:00:00 UTC | 3 | 0 | 3 |
| Jul 2025 | 2025-07-01 00:00:00 UTC | 2025-08-01 00:00:00 UTC | 1 | 0 | 1 |
| Aug 2025 | 2025-08-01 00:00:00 UTC | 2025-09-01 00:00:00 UTC | 1 | 0 | 1 |
| Sep 2025 | 2025-09-01 00:00:00 UTC | 2025-10-01 00:00:00 UTC | 0 | 0 | 0 |
| Oct 2025 | 2025-10-01 00:00:00 UTC | 2025-11-01 00:00:00 UTC | 0 | 0 | 0 |
| Nov 2025 | 2025-11-01 00:00:00 UTC | 2025-12-01 00:00:00 UTC | 0 | 0 | 0 |
| Dec 2025 | 2025-12-01 00:00:00 UTC | 2026-01-01 00:00:00 UTC | 1 | 0 | 1 |
| Jan 2026 | 2026-01-01 00:00:00 UTC | 2026-02-01 00:00:00 UTC | 0 | 0 | 0 |
| Feb 2026 | 2026-02-01 00:00:00 UTC | 2026-03-01 00:00:00 UTC | 1 | 0 | 1 |
| Mar 2026 | 2026-03-01 00:00:00 UTC | 2026-04-01 00:00:00 UTC | 0 | 0 | 0 |
| Apr 2026 | 2026-04-01 00:00:00 UTC | 2026-05-01 00:00:00 UTC | 0 | 0 | 0 |
| May 2026 | 2026-05-01 00:00:00 UTC | 2026-06-01 00:00:00 UTC | 0 | 0 | 0 |
| Jun 2026 | 2026-06-01 00:00:00 UTC | 2026-07-01 00:00:00 UTC | 0 | 0 | 0 |
| Jul 2026 | 2026-07-01 00:00:00 UTC | 2026-08-01 00:00:00 UTC | 0 | 0 | 0 |
| Aug 2026 | 2026-08-01 00:00:00 UTC | 2026-09-01 00:00:00 UTC | 0 | 0 | 0 |
| Sep 2026 | 2026-09-01 00:00:00 UTC | 2026-10-01 00:00:00 UTC | 0 | 0 | 0 |
| Oct 2026 | 2026-10-01 00:00:00 UTC | 2026-11-01 00:00:00 UTC | 1 | 0 | 1 |
What Hacker News says
12 sourcesDIdicytea·Oct 1, 2026
Cranelift's biggest blocker for me is that it completely breaks debuggers:
https://github.com/rust-lang/rustc_codegen_cranelift/issues/...
In How to speed up the Rust compiler in September 2026Is offering an alternative to LLVM not precisely one of the purposes of the rustc_codegen_cranelift backend [0]? It still doesn't have 100% feature parity, but I believe it's able to fully bootstrap the compiler at this point. Writing a rustc backend isn't trivial, but it isn't as impossible as you make it out to be.
[0] https://github.com/rust-lang/rustc_codegen_cranelift
In map::operator[] should be nodiscardLink times are the worst part but solveable with mold[1]/sold. Incremental compilations are usually an order of magnitude (or even two) faster than clean compiles but tbh that can still feel slow. Helped by using something like sccache[2] or even cranelift[3] when debugging. Still not as fast as having a hot-reloadable language but it gets you to a relatively pleasant speed still IME
[1] https://github.com/rui314/mold
[2] https://github.com/mozilla/sccache
[3] https://github.com/rust-lang/rustc_codegen_cranelift
In Unexpected productivity boost of RustThere's an experimental compiler backend [1] using cranelift [1] that's supposed to improve debug build times. I never see it mentioned often in threads about Rust's long compilation time so I'm not sure if I'm missing something.
[1] https://github.com/rust-lang/rustc_codegen_cranelift/
[2] https://cranelift.dev/
In Building the Rust Compiler with GCCThere is an experimental Cranelift backend[0] for rustc to improve compilation performance in debug builds.
https://github.com/rust-lang/rustc_codegen_cranelift
In Why is the Rust compiler so slow?> I wonder if how much value there is in skipping LLVM in favor of having a JIT optimized linked in instead. For release builds it would get you a reasonable proxy if it optimized decently while still retaining better debugability.
Rust is in the process of building out the cranelift backend. Cranelift was originally built to be a JIT compiler. The hope is that this can become the debug build compiler.
https://github.com/rust-lang/rustc_codegen_cranelift
In Rust compiler performance> This is awesome for Zig, I think this direction is gonna be a primary differentiator when comparing to Rust.
FWIW there is a similar effort for Rust using cranelift: <https://github.com/rust-lang/rustc_codegen_cranelift>
In Self-hosted x86 back end is now default in debug modeThere's no reason? Are you sure about this?
I think you mean there could theoretically be an interpreted Rust, but I don't think anyone has ever made a prototype of a Rust interpreter.
The closest is probably rust-analyzer (the official language server), that maintains internal state and reacts to changes you make, but it doesn't create an executable artifact.
The other is probably the Cranelift Backend (https://github.com/rust-lang/rustc_codegen_cranelift), which can produce debug builds quickly.
In I Hope Rust Does Not Oxidize EverythingWindows is supported. See https://github.com/rust-lang/rustc_codegen_cranelift/issues/....
In Cranelift code generation comes to RustI will chime in to day that rust is also building a alternative to the LLVM backend in the form of cranelift : https://github.com/rust-lang/rustc_codegen_cranelift
In What part of Rust compilation is the bottleneck?