Add various integer ops

[calebzulawski]

Pending rust-lang/rust#114266 and an i16xN::trailing_zeros bug that I hope is fixed by LLVM 15 17

Good to go.

[workingjubilee]

LLVM 15 is already our minimum.

[calebzulawski]

Whoops, I meant 17

[workingjubilee]

can you describe the bug?

[calebzulawski]

I haven't looked at the codegen yet, but it reports that 4905 has 3 trailing zeros

---- i16::trailing_zeros::lanes_1 stdout ----
thread 'i16::trailing_zeros::lanes_1' panicked at 'called `Result::unwrap()` on an `Err` value: Fail(Reason("assertion failed: `(left == right)` \n  left: `[3 (3)]`,\n right: `[0 (0)]` at crates/test_helpers/src/lib.rs:175"), [4905])', /Users/caleb/repos/portable-simd/crates/test_helpers/src/lib.rs:117:43

---- i16::trailing_zeros::lanes_2 stdout ----
thread 'i16::trailing_zeros::lanes_2' panicked at 'called `Result::unwrap()` on an `Err` value: Fail(Reason("assertion failed: `(left == right)` \n  left: `[3 (3), 16 (10)]`,\n right: `[0 (0), 16 (10)]` at crates/test_helpers/src/lib.rs:175"), [4905, 0])', /Users/caleb/repos/portable-simd/crates/test_helpers/src/lib.rs:117:43

[calebzulawski]

Aha, actually it's a bug in my test (I compare against leading_zeros). I'm disturbed that it only failed for i16, which led me to believe it couldn't be my test...

[sammysheep]

Why is it called swap_bytes and not rev_bytes or some such thing? Say for u32 elements, is it swapping the high and low 16 bits, or are you reversing the byte order over all 4 bytes?

Sorry if this was stated elsewhere.

[calebzulawski]

That is the name used by scalars for the same operation: https://doc.rust-lang.org/std/primitive.i32.html#method.swap_bytes