PartialEq is fundamentally broken for stdsimd types

[gamozolabs]

The following code triggers an assertion, which checks if !(==) is the same as !=.

In this case the issue only occurs when there are different values in the vector. The current tests only check that PartialEq is working in the splat against splat case, which it does work correctly. However when there is a different value in the vector (non-splatted), PartialEq is incorrect.

This issue also occurs when using u32x4 and mask values. It does not seem to be an issue with just the 512-bit emulation.

Tests should also be expanded to test non-splatted cases.

#![feature(stdsimd)]

use std::simd::u32x16;

fn main() {
    let foo = u32x16::new(
        0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 1,
    );
    let target = u32x16::splat(1);
    
    print!("Are they different? {}\n", foo != target);
    print!("Are they equal?     {}\n", foo == target);
    
    assert!((foo != target) == !(foo == target));
}

This will result in

Standard Error
   Compiling playground v0.0.1 (file:///playground)
    Finished dev [unoptimized + debuginfo] target(s) in 1.31s
     Running `target/debug/playground`
thread 'main' panicked at 'assertion failed: (foo != target) == !(foo == target)', src/main.rs:15:5
note: Run with `RUST_BACKTRACE=1` for a backtrace.

Standard Output
Are they different? false
Are they equal?     false

https://play.rust-lang.org/?gist=9e0799d170e488b7c691b6f98ccc72ca&version=nightly&mode=debug

-B

[gamozolabs]

Related #457

Testing was done on x86_64 in my case.

[gamozolabs]

Bug seems pretty simple. ne() is implemented as $id::ne(*self, *other).all() where it should be $id::ne(*self, *other).any()

This is in impl_partial_eq

I've never done a pull request but I will attempt one. Sorry if I do it wrong :P

-B

[gnzlbg]

This was closed in 4751cb9