[DebugInfo][HGLDD] Consuming Tywaves annotations containing extra source language information from Chisel and improve HGLDD format

[rameloni]

This PR adds new functionality to CIRCT for emitting source language type information in HGLDD https://github.com/llvm/circt/issues/6983.

This new functionality support the new backend of my project. Tywaves: a type-based waveform viewer. Tywaves adds support for Chisel to Surfer through HGLDD, however it misses of Chisel-type information and a proper documentation.

So, in addition to the changes I made to CIRCT, I also created a library for reading and documenting HGLDD in rust. I noticed that HGLDD misses a formal specification, so the rust documentation is a first attempt to provide more formal description of the fields contained in the file.

Specific contribution to CIRCT

• Extract source language type information (not FIRRTL) encoded as TywavesAnnotation by Chisel https://github.com/chipsalliance/chisel/pull/4224
• Associate it to respective MLIR operations
• Consume it during MaterializeDebugInfo and convert to debug dialect operations
• Add two new debug dialect operations to support internal representation of extra debug info for subfields of aggregates and modules (dbg.subfield and dbg.moduleinfo) https://github.com/llvm/circt/blob/a1f795e10fb5ae945fb00de8635ef0bce7ce2337/include/circt/Dialect/Debug/DebugOps.td#L87-L114 https://github.com/llvm/circt/blob/a1f795e10fb5ae945fb00de8635ef0bce7ce2337/include/circt/Dialect/Debug/DebugOps.td#L154-L168
• Emit that information into HGLDD for modules, variables and subfields https://github.com/llvm/circt/blob/a1f795e10fb5ae945fb00de8635ef0bce7ce2337/lib/Target/DebugInfo/EmitHGLDD.cpp#L558-L580 https://github.com/llvm/circt/blob/a1f795e10fb5ae945fb00de8635ef0bce7ce2337/lib/Target/DebugInfo/EmitHGLDD.cpp#L612-L615 https://github.com/llvm/circt/blob/a1f795e10fb5ae945fb00de8635ef0bce7ce2337/lib/Target/DebugInfo/EmitHGLDD.cpp#L702-L705
• Document HGLDD https://github.com/rameloni/tywaves-rs/blob/main/src/hgldd/spec.rs

[rameloni]

The related PR in chisel: https://github.com/chipsalliance/chisel/pull/4224

[darthscsi]

Some general comments: We are trying very hard to not add new annotations. I thought the current debug efforts were grabbing chisel types and only falling back to firrtl types if asked. It might be this isn't done yet, in which case the efforts should be coordinated. @fabianschuiki or @prithayan might be able to shed more light.

[rameloni]

Some general comments: We are trying very hard to not add new annotations. I thought the current debug efforts were grabbing chisel types and only falling back to firrtl types if asked. It might be this isn't done yet, in which case the efforts should be coordinated. @fabianschuiki or @prithayan might be able to shed more light.

@darthscsi thanks for the comment. Yeah, I found that Intrinsics might be a better option to do that. However, I'm not sure if I can make it before the deadline of my thesis. That's why I'm using at the moment the annotations, since I've found they were slightly easier to manage on average between Chisel and CIRCT sides

[rameloni]

I have also noticed another thing. HGLDD also missed reference to enum variants, so I'm trying to add that. I've seen that the hw dialect has a definition of EnumType however it seems not to be generated?!? I'm not sure, am I wrong? Chisel passes the enum variants through 3 annotations (EnumComponentAnnotation, EnumDefAnnotation, and EnumVecAnnotation) but they are dropped in the LowerAnnotations pass, is there a reason for that? Apart from the fact you are trying to replace the annotation mechanism.