[llvm] [DirectX] Set whole-module flags prior to evaluating per-function flags (PR #139967)

[Deric C. via llvm-commits]

Icohedron wrote:

> I think the bugs you are fixing were mostly found because of the validator? Should we be doing some testing that invokes the validator something similaor to what `llvm/test/tools/dxil-dis/` tests do?

Yes, the bugs were found in the validator. 
Unlike dxil-dis, dxv (the validator) isn't included as a tool with LLVM. Perhaps dxv should be made available as llvm-dxv perhaps?

Or, the DirectX tests could have RUN lines conditioned on having dxv in the path, and runs the validator if it is in the path; similar to spirv-val I saw in SPIRV tests.

Either way, I think this topic should be relegated to a separate issue and PR.

https://github.com/llvm/llvm-project/pull/139967