Bounds checking

Reading and writing packed vectors to/from slices is checked by default. Independently of the configuration options used, the safe functions:

• Simd<[T; N]>::from_slice_aligned(& s[..])
• Simd<[T; N]>::write_to_slice_aligned(&mut s[..])

always check that:

• the slice is big enough to hold the vector
• the slice is suitably aligned to perform an aligned load/store for a Simd<[T; N]> (this alignment is often much larger than that of T).

There are _unaligned versions that use unaligned load and stores, as well as unsafe _unchecked that do not perform any checks iff debug-assertions = false / debug = false. That is, the _unchecked methods do still assert size and alignment in debug builds and could also do so in release builds depending on the configuration options.

These assertions do often significantly impact performance and you should be aware of them.