[clang] [llvm] [HLSL] Reapply Move length support out of the DirectX Backend (#121611) (PR #122337)

[Chris B via llvm-commits]

llvm-beanz wrote:

> No failures. We would need to have tests for all intrinsics that if its not SM 6.2 or greater uses of half would error, but we never did that for any of the other intrinsics so we should probably discuss what the test coverage should be and apply it broadly.

In practice these are pretty tricky to test on just Clang because the 6.2 attribute only applies when -enable-16bit-types is set, which requires shader model 6.2 or greater. So you shouldn't actually be able to make the compiler fail this.

The point of the attribute is really just for header completeness so that we can drive documentation and LSP tooling from it.

https://github.com/llvm/llvm-project/pull/122337