DevMeeting - 2021-08-16/17

[jackkoenig]

2021-08-16/17

Outreach

Updates

• DataView is merged 🎉
  • AXI Example from docs: https://scastie.scala-lang.org/1UczoG5hRk6KQbI5EgQvfg

Pinned Items

• Priority PRs:
  *

Discussion 1

• [jack] Chisel 3.5.0-RC1 or 3.5.0-M1
  • Would like to get DataView and InstanceAPI out for people (including SiFive) to try in production
  • Good to get our new features (including Scala 2.13) out that people can rely on
  • Not ready for .0 because of some bugs and other features in development (chiseltest stuff?)
    • In particular, stuff around compiler plugin fixes
  • What non-Chisel stuff is wanted in this release?
  • Needed PRs:
    • Instance/Definition: Instance/Definition (formerly Template) #2045
    • RenameMap backport deprecation: Turn RenameMap into a trait and add MutableRenameMap firrtl#2318
      • Needed because the removal was merged to master
• instance API discussion
  • [jiuyang] can we use instance API for diplomacy?
    • [jack] already trying that internally at SiFive
    • [jack] What we have isn’t super well integrated, we just break at the LazyModuleImp (which is a Chisel module)
  • [kevin] queue interning?
    • Should this be part of the PR?
    • It would be true dogfooding
  • [jack] Biggest risk is really custom transformations/annotations not handling multiple instantiation correctly
• [schuyler] Switch and When codegen
  • Scala FIRRTL could be improved
  • MLIR FIRRTL should generate optimal code by the end of the day…
  • Discussion:
    • [RFC] Deprecate switch-is #2069
    • Remove switch #2070
  • [jiuyang] Related to potential FSM API
    • FSM API #2071
    • [jack] We mainly need to know what the Verilog should look like
  • [kevin] Already has a pass to recognize state machines
• [jiuyang] Can we hand off to CIRCT?
  • [schuyler] We cannot go CIRCT -> Scala FIRRTL but can go Scala FIRRTL -> CIRCT
  • We could do Low FIRRTL -> CIRCT -> Verilog (basically use CIRCT as a Verilog Emitter)
    • This may be beneficial for specific cases like the switch issue
    • Biggest issue is custom transforms and file emission, if you don’t use CustomFileEmission and emit custom datafiles, it would likely break
    • Schuyler already has a start to this: https://github.com/sifive/chisel-circt
    • Probably only thing we need in addition to chisel-circt and emit a bunch of DontTouches for CustomFileEmission (and make chisel-circt support annotation files)
  • Longer term we have the standard native binary distribution problem
• [kevin] chiseltest with custom (e.g. SiFive) frontend flow
  • currently we recreate the ChiselStage infrastructure:
    Elaborate and toLowFirrtl
  • Adam said that SiFive has custom frontend flow, and thus cannot use chiseltest
  • Ideally we would add some infrastructure to chisel3 that allows users to define custom frontend flows that generate the circuit object (the scala instance inheriting from RawModule) and the LoFirrtl.
  • [jiuyang] I did(but not merged) in that giant PR. DependencyAPI Phase 4 ucb-bar/chiseltest#200
    • I’m proposing adding a ChiselTestStage and ScalaTest/Utest depending on it.
  • conclusion: don’t worry about this for now, SiFive only might want to use chiseltest for unittesting, so we do not need to run the custom stage for now

Discussion 2

• [jiuyang] Chisel PRs:
  • prefer to using using system protoc and antlr4 in mill firrtl#2276
  • Z3 CI debug #2057 ready for merging.
  • Speed up CI #2043
    • [jack] Let’s not deprecate TesterDriver in this PR, we need replacement for people who might actually use it so do that separately
  • remove DefRegInit, change DefReg API with option definition. #1944 ready for merging.
• [jiuyang] Trace API:
  • Signal Trace API #2077
  • I think it seems to be a slim Grand Central API.
    • https://github.com/llvm/circt/blob/6fe0463eac523f15f7a2b954c2a46663fc9c4c40/docs/FIRRTLAnnotations.md#grand-central
  • Basically it provides an API to map from hasId.toTarget -> Target(after entire transform renames)
  • In the future refactor of chiseltest:
    • It might be more reasonable to peek/poke to Data.toTarget, which is String,
    • Using map generated by trace API to find the final signal name,
    • In the Simulator backend, those need to implement the API to
      • Convert Target to internal symbol table.
      • Implement Peek/Poke and etc scala APIs.
    • This would be better to provide a serializable AnnotationSeq
  • [jack] This is great, let’s just refine the user API a little bit
    • I’d like to see it used to create a Verilator config file (just in src/test/scala is fine for now)
  • [schuyler] This is probably missing the ability to track not just renames but also ConstProp and DCE sort of things
    • What if we don’t want to “DontTouch” the targets?
• [jiuyang] chipsalliance issues:
  • approve/merging strategy?
    • Add CI to publish project to maven. cde#17
  • sonatype account?
  • PLCT is applying gold member of chipsalliance but and waiting for review for 1 weeks :(
    • Ping who?
  • Standalone diplomacy:
    • Add Diplomacy to Sandbox projects tac#76
    • Package name changed.
    • Originally diplomacy from rocket-chip cannot use strict compile options(don’t check unconnected IO).
    • I kept all only LM and Node API for diplomacy, and can replace RC source directly via Split diplomacy into the standalone repository rocket-chip#2741
  • [jack] We should get write access to CDE, will ping Brian about sonatype and PLCT application
    • Need to talk to Henry when back from vacation
  • Espresso
    • Working on a C++ version
      • a little bit(O(1)) slower, but much easier to maintain.
      • Will release version 3.0
        • Deprecate a lot of APIs(lost codes which was stored in tapes) since 2.5
        • 3.0 will be a slim C++ rewrite.
    • Ask Jack for the license issue.
      • Two options:
        • Ask the author/UCB to re-license.
          • https://ptolemy.berkeley.edu/projects/embedded/
          • https://www.berkeley.edu/news/media/releases/2005/01/05_donpederson.shtml
        • rewrite and relicense in 3.0…
    • [jack] I don’t know what to do here