Support aligned globals

[ahomescu]

Submitted by @Lokathor via email:

Your need for aligned globals has come up before and the best way to get some aligned static data without making a new struct every single time is to generalize what you did with the SSEMask type:

#[repr(align(16))]

pub struct Align16<T>(pub T);

 

static ssemask: &[u8; 16] = &Align16([7_u8; 16]).0;

 

#[test]

fn aligned() {

    assert_eq!(ssemask as *const _ as usize % 16, 0);

}

I like this approach, we could implement it for a few common aligment values: 16 (common for SSE values), 32, 64 (common for cache-aligned data) and maybe 128.

[Lokathor]

Align4 is also popular to make include_bytes! be "word aligned" so you can safely cast it to &[u32] without fail.

The drawback of is this that it doesn't work on static mut, but you really shouldn't be using static mut in the first place if it's in any way possible to avoid it, and usually you can avoid it.