[HandshakeToHW] Tracking issue

[mortbopet]

This is a tracking issue for the reimplementation of HandshakeToFIRRTL to a HW/ESI-based implementation:

• Operators
  • [x] Mux
  • [ ] Conditional branch
  • [ ] Buffer
    • [x] Seq
    • [ ] Fifo: A fifo is most easily implemented when some memory abstraction can be targeted (ready/write pointers, transparency, ...). We don't yet have such abstraction to target - ideally, seq should support some notion of high-level memory which lowers down into something that synthesizes reasonably toan FPGA.
  • [ ] Constant
  • [x] Fork
  • [x] Join
  • [ ] LazyFork
  • [ ] Load
  • [ ] Store
  • [ ] Memory
  • [ ] External memory
  • [x] Select
  • [x] Sync
  • [x] Pack
  • [x] Unpack
• [ ] Support pruning i0 logic
  • HandshakeToHW attempts to to keep special-case logic for handling none (soon to be i0)-typed values. This implies that any handshake SSA value which is i0 still carries ready/valid/data semantics, however the data part of the bundle is of zero width. Given this style of lowering, we need a pass that is able to prune the i0 logic post-conversion (or keep it around until emission and let the emitter decide what to do with it).
• [ ] Figure out how to support memories
  • This will be ESI based, and should use an ESI service.
• [ ] Move integration tests from FIRRTL to HW implementation
• [ ] Remove HandshakeToFIRRTL