LLVM loop miscompilation

I'm filing this issue on behalf of @pitust, who discovered this issue.

This is caused by https://github.com/llvm/llvm-project/issues/183906

The following code constructs a NonZero<i8> that has a value of 0 at run time when compiled in release mode, which is unsound.

use std::num::NonZero;

#[inline(never)]
pub fn func() -> NonZero<i8> {
    let mut i = -5;
    let mut j = -4;
    loop {
        let x = loop {
            if let Some(v) = NonZero::new(j) {
                break v;
            }
            j *= 3;
        };
        i += 1;
        j += 1;
        if i == 0 {
            return x;
        }
    }
}

fn main() {
    println!("{}", func());
}

Meta

Reproducible on the playground with version 1.95.0-nightly (2026-02-24 859951e3c7c9d0322c39)

Reproduce the issue using the provided Rust example on the playground with version 1.95.0-nightly (2026-02-24 859951e3c7c9d0322c39). Start by reading the linked LLVM issue 183906 and comparing its findings with this example; the work is complete when the release build no longer produces an invalid NonZero value.