Portable vector type methods are broken within `#[target_feature = "..."]`

[sfackler]

This is due to a known issue (rust-lang/rust#44367), but it's pretty confusing.

#![feature(target_feature)]

extern crate stdsimd;

use stdsimd::simd::u32x8;

fn main() {
    foo();
}

#[target_feature = "+avx2"]
fn foo() {
    let p = u32x8::new(0, 1, 2, 3, 4, 5, 6, 7);
    println!("{:?}", p);
}

$ cargo +nightly run
   Compiling foo v0.1.0 (file:///Users/sfackler/foo)
    Finished dev [unoptimized + debuginfo] target(s) in 0.32 secs
     Running `target/debug/foo`
u32x8(0, 1, 2, 3, 0, 0, 0, 0)

$ cargo +nightly run --release
   Compiling stdsimd v0.0.2 (https://github.com/rust-lang-nursery/stdsimd#6fdfce52)
   Compiling foo v0.1.0 (file:///Users/sfackler/foo)
    Finished release [optimized] target(s) in 4.43 secs
     Running `target/release/foo`
u32x8(0, 1, 2, 3, 4, 5, 6, 7)

Switching p to a static with #137 makes everything work.

[sfackler]

Ah, this is rust-lang/rust#45201, and I have an outdated nightly!