[llvm] [DirectX][DXIL] Design document for TableGen Spec of DXIL Operations (PR #85170)

[S. Bharadwaj Yadavalli via llvm-commits]

bharadwajy wrote:

> Can you include in the examples for each of the options how we would represent the requirements for specific overloads? For example the `Sin` DXIL Op is valid for `float` in SM 6.0+, and valid for `half` in SM 6.2+.

Added a section with the details. Thanks!

https://github.com/llvm/llvm-project/pull/85170