[water] NormalForm Module

[tgymnich]

• introduce NormalForm Dialect with a NormalForm module and a NormalFormAttrInterface

[ftynse]

Not for this PR, but we will likely want this op in a separate dialect, working towards generalization of normal forms.

cc @fabianmcg

[fabianmcg]

Nice! Thanks @ftynse for the pointer!

We realized we couldn't continue without some version of them, so we also took a stab at implementing them. Putting here our relevant files. We should likely sync at some point.

• Attribute interface: https://github.com/iree-org/aster/blob/main/include/aster/Interfaces/VerifierAttr.td
• Header: https://github.com/iree-org/aster/blob/main/include/aster/Interfaces/VerifierAttr.h
• Source: https://github.com/iree-org/aster/blob/main/lib/Interfaces/VerifierAttr.cpp
• Impls: https://github.com/iree-org/aster/blob/main/lib/Dialect/AMDGCN/IR/AMDGCNVerifiers.cpp

I used VerifierAttr instead of normal form because if I remember correctly, Alex's definition at LLVM dev is more general.

[tgymnich]

pass nullstream if we don't want errors. Remarks should already not be emitted by default??? Or call abandon on inflight diagnostic

[ftynse]

IDK if we can create an InFlightDiagnostic that will not actually emit anything if so, we can try that. Otherwise, we can (rather heavily) have a wrapper class that holds an optional InFlightDiagnostic and has the same API so it's transparent to the caller. Another heavy-ish solution is to register a diagnostic handler that discards all errors before the interface method call and unregister it immediately after, though we may potentially discard some errors that are not specific to the interface method.

[tgymnich]

It seems like we can just abandon the diagnostic before returning it to the verifier.

[ftynse]

I used VerifierAttr instead of normal form because if I remember correctly, Alex's definition at LLVM dev is more general.

The talk was more of an overall vision, we don't have to implement all of that. The dependencies between verifiers are a nice idea. What I also want here is a way to control error emission, so we can "discover" which forms are present without reporting errors, for example.