No auto-vectorization in such case since 1.54.0

[solotzg]

I tried this code:

const MAX_STEP_DATA_SIZE: usize = 32;

#[inline]
fn check(byte: u8) -> bool {
    return (byte <= 0x20) || (byte == 0x22) || (byte == 0x3D) || (byte == 0x5B) || (byte == 0x5D);
    return (byte <= 0x20) | (byte == 0x22) | (byte == 0x3D) | (byte == 0x5B) | (byte == 0x5D);
}

#[inline]
fn is_any(s: &[bool]) -> bool {
    let mut res = false;
    for i in 0..s.len() {
        res |= s[i];
    }
    res
}

unsafe fn test_impl(s: *const u8, len: usize) -> bool {
    let mut step_data = [false; MAX_STEP_DATA_SIZE / std::mem::size_of::<u8>()];
    let mut s = s;
    let mut len = len;
    while len >= step_data.len() {
        for i in 0..step_data.len() {
            step_data[i] = check(*s.add(i));
        }

        if is_any(&step_data) {
            return true;
        }

        s = s.add(step_data.len());
        len -= step_data.len();
    }
    for i in 0..len {
        if check(*s.add(i)) {
            return true;
        }
    }
    return false;
}

pub fn test(s: &[u8]) -> bool {
    unsafe { test_impl(s.as_ptr(), s.len()) }
}

With rustc 1.53.0-nightly
run RUSTFLAGS="--emit=asm -C target-feature=+avx2" cargo build --release
rustc can generate vectorized asm.

But with 1.54.0 or higher, rustc can not make optimization.

It can be verified in godbolt.org as well.

Meta

rustc --version --verbose:

rustc 1.59.0-nightly (e100ec5bc 2021-12-21)
binary: rustc
commit-hash: e100ec5bc7cd768ec17d75448b29c9ab4a39272b
commit-date: 2021-12-21
host: x86_64-unknown-linux-gnu
release: 1.59.0-nightly
LLVM version: 13.0.0

Backtrace

<backtrace>

[AngelicosPhosphoros]

Duplicate of #83623 probably.

[solotzg]

Duplicate of #83623 probably.

Maybe.
It can works as expected if I replace || by | in fn check

[workingjubilee]

Still deeply deoptimized today.