Miscompilation with -Zsanitizer=address

[fintelia]

I tried this code:

#[inline(never)]
fn unfilter(current: &mut [u8]) {
    current.iter_mut().reduce(|&mut prev, curr| {
        *curr = curr.wrapping_add(prev);
        curr
    });
}

fn main() {
    let mut data = [255, 0, 18, 243, 13, 240, 255, 0, 4];
    unfilter(&mut data);
    assert_eq!(data, [255, 255, 17, 4, 17, 1, 0, 0, 4]);
}

And compiled with these arguments:

RUSTFLAGS="-Zsanitizer=address -Clink-dead-code -C codegen-units=1" cargo +nightly run -Z build-std --target=x86_64-unknown-linux-gnu --release

I expected to see this happen: assertion passes like it does on the playground or with cargo run.

Instead, this happened:

thread 'main' panicked at src/main.rs:12:5:
assertion `left == right` failed
  left: [255, 255, 18, 5, 0, 253, 239, 255, 4]
 right: [255, 255, 17, 4, 17, 1, 0, 0, 4]

Meta

rustc +nightly --version --verbose:

rustc 1.77.0-nightly (d5fd09972 2024-01-22)
binary: rustc
commit-hash: d5fd0997291ca0135401a39dff25c8a9c13b8961
commit-date: 2024-01-22
host: x86_64-unknown-linux-gnu
release: 1.77.0-nightly
LLVM version: 17.0.6

[nikic]

Also reproduces without -Z build-std. I also tested this with +b10e3758cdf73aa9155f6b955843731a66488b9c, so it doesn't look like this issue has been fixed in LLVM 18.

[nikic]

opt-bisect points to:

BISECT: NOT running pass (2036) LoopVectorizePass on _ZN3foo8unfilter17hcdf00299b79e44ccE

IR for this function without and with LoopVectorize: https://gist.github.com/nikic/619764c58f3cd184326ffdd6831abc2e

[nikic]

Upstream issue: llvm/llvm-project#79137

[apiraino]

WG-prioritization assigning priority (Zulip discussion).

@rustbot label -I-prioritize +P-high

[nikic]

Fixed upstream by llvm/llvm-project@cd7ea4e.

[nikic]

Fixed in beta & nightly.