I think that SIMD code should not be written by hand but rather in a high-level language and so dealing with tail becomes a compiler's and not a programmer's problem. Or people still prefer to write assembly be hand? It seems to be so judging by the code you link.

What I wanted is to write code in a more high-level language like this. For example, to compute a scalar product of a and b you write:

    1..n | a[$1] * b[$1] | sum

    x = sum for i in 1 .. n: a[i] * b[i]

Zig exposes a Vector type to use for SIMD instructions, which has been my first introduction to SIMD directly. Reading through this thread I was immediately mapping what people were saying to Vector operations in Zig. It seems to me like SIMD can reasonably be exposed in high level languages for programmers to reach to in contexts where it matters.

Of course, the compiler vectorizing code when it can as a general optimization is still useful, but when it's critical that some operations must be vectorized, explicit SIMD structures seem nice to have.