[INF-0004] Validator should fill hash with PREVIEW pattern for pre-release DXIL version

[tex3d]

Which proposal does this relate to?
proposals/infra/INF-0004-validator-hashing.md

Describe the issue or outstanding question.
The spec does not address pre-release DXIL version behavior. We need to keep track of the last released stable DXIL version and only hash the container if the current DXIL version is less than or equal to this version. We should set the hash to the PREVIEW pattern otherwise.

Additional context
Previously, we would avoid hashing pre-release DXIL by only releasing the external hashing validator once we had a final release for that DXIL version. Now that hashing is included in every intermediate version of the compiler built from the open source project, we need another mechanism to differentiate the release hash behavior from in-development preview features.

[llvm-beanz]

For pre-release shader models DXC should run the validator, but it should not
apply the hash. Instead it should apply the PREVIEW sentinel value from the
table above. This allows us to differentiate between shaders validated by a
"final" validator.

Source

Can you be more clear about how you think this should be modified? I believe this covers the intent although perhaps the wording could be more clear.

[damyanp]

@tex3d - can you mark this for triage again once you've had a chance to address Chris's comment above please?