Surprising behavior of portable SIMD integer vector max/min

[RalfJung]

The following code does not print what I would expect:

#![feature(portable_simd)]
use std::simd::*;

fn main() {
    let a = i32x4::splat(10);
    let b = i32x4::from_array([1, 2, 12, -4]);
    println!("{:?} {:?}", a.max(b), a.min(b));
}

I expected element-wise max/min, but I got:

[10, 10, 10, 10] [1, 2, 12, -4]

The funny thing is that portable-simd does not even define max/min on its integer SIMD types (only on the float ones). What happens is that it falls back to Ord::max, and it looks like vectors implement Ord by comparing them as arrays, which probably uses lexicographic comparison.

However this means integer and float vectors max/min methods behave very differently, so this is probably not intended?

Cc @workingjubilee

[jfrimmel]

I think this is the same as rust-lang/portable-simd#247 and rust-lang/portable-simd#253.

[RalfJung]

Ah, it is.

Not sure which issue tracker is the preferred one for such issues.

[workingjubilee]

Hello!
Yes, it is a bit peculiar and we should fix that.
We usually track library-level issues over there and integration-level issues on the Rust issue tracker.

[RalfJung]

Fixed by rust-lang/portable-simd#260
(though clamp remains unfixed)