Missing optimization for interger `modulo` operation in `loop` edge case
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A-codegen
A-LLVM
C-optimization
I-slow
T-compiler
- Dominant language
- Rust
- Stars
- 119k
- Forks
- 16.1k
- PR merge metrics
- PR metrics pending
Description
rust and c can't optimize code like this when modulo is larger than 100 and is not power of 2 but cpp can:
fn modulo() {
let mut j = 0;
loop {
j = j + 1;
if j % modulo == 0 {
return;
}
}
}
rust: godbolt link
c: godbolt link
cpp: godbolt link
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First steps
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Research direction
Start by comparing the Rust, C, and C++ Compiler Explorer links for the loop with a non-power-of-two modulo above 100. Trace the Rust compiler optimization path responsible for this loop and compare the generated code; done means Rust emits an equivalent optimization for the reported edge case, with a regression test covering it.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- c, cpp, rust
- Domain
- compilers, performance
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100