Should long vectors be supported on shader models that don't support native vectors?

[pow2clk]

Which proposal does this relate to?
https://github.com/microsoft/hlsl-specs/blob/main/proposals/0026-hlsl-long-vector-type.md

Describe the issue or outstanding question.
Should long vectors be allowed for shader models that don't support native vectors? They could be supported through scalarization of the long vectors into individual scalar operations or 4 at a time loads and stores. It doesn't necessarily hinge on the question of whether this is a language feature or not, but if it is a language feature, it would ordinarily be expected to work on all shader models.

Additional context

A number of comments in PR #361 brushed up against this, but this is the comment that explicitly requested this issue: #361 (comment)