Portable vector shuffles

[gnzlbg]

I've just submitted a PR with an API for portable vector shuffles (#387). From the docs:

// Shuffle allows reordering the elements of a vector:
let x = i32x4::new(1, 2, 3, 4);
let r = shuffle!(x, [2, 1, 3, 0]);
assert_eq!(r, i32x4::new(3, 2, 4, 1));

// The resulting vector can be smaller than the input:
let r = shuffle!(x, [1, 3]);
assert_eq!(r, i32x2::new(2, 4));

// Equal:
let r = shuffle!(x, [1, 3, 2, 0]);
assert_eq!(r, i32x4::new(2, 4, 3, 1));

// Or larger (at most twice as large):
et r = shuffle!(x, [1, 3, 2, 2, 1, 3, 2, 2]);
assert_eq!(r, i32x8::new(2, 4, 3, 3, 2, 4, 3, 3));

// It also allows reordering elements of two vectors:
let y = i32x4::new(5, 6, 7, 8);
let r = shuffle!(x, y, [4, 0, 5, 1]);
assert_eq!(r, i32x4::new(5, 1, 6, 2));
// And this can be used to construct larger or smaller
// vectors as well.

It would be nice to gather feed-back on this.

[TheIronBorn]

Does this API allow shuffling where the indices are unknown? i.e. using _mm_shuffle_epi8 where the indices vector is unknown? (useful for SIMD lookup "tables")

[gnzlbg]

The indices need to be known at compile time for the compiler to generate the right shuffle sequence.

…

On Fri 22. Jun 2018 at 23:47, TheIronBorn ***@***.***> wrote: Does this API allow shuffling where the indices are unknown? i.e. using _mm_shuffle_epi8 where the indices vector is unknown? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#388 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AA3NppCspl5Hj9scx5u7s7mZcI9rIjsnks5t_WXvgaJpZM4Sx823> .

[gnzlbg]

This has been fixed in https://github.com/gnzlbg/packed_simd