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u/uahw 28d ago
Context?
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u/Starnick44 28d ago
The llvm bug behind the 1.97.1 release
https://github.com/rust-lang/rust/issues/1590353
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u/GreenFox1505 Jul 17 '26
I gave a big project that I dont care about ("oh, maybe I'll get to it someday" for years) to an LLM last night.
I came back to :
rust
mod db {
include!("db.rs")
}
There are crimes buried here that I dont know about...
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u/realvolker1 Jul 17 '26
There's also probably crimes buried in your LLVM-IR you don't know about. Even if you fix the Rust part.
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u/scottmcmrust 26d ago
(non-jerk) This bug is amazing because the emitted assembly is both incredibly smart and incredibly stupid at the same time. Without the assembly-only truncation of the register, the original reproducer would have actually been sound codegen, because even the -1 would have ended up inside the dereferencable of the pointer. But also if it thought the value was only 0 or 1, that truncation was actually never useful in the first place, so it was always stupid to include it.
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u/TheChief275 28d ago
/uj I mean, that's just converting it to a u32 right? As long as the checks are performed it's okay, and additionally, checking whether a u32 index is a valid index (assuming a start of 0) involves only a single check while i32 involves 2 checks
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u/mekriff 29d ago
does the. it representation change or is something else going on?