Clashilator: Automated Clash - Verilator integration

This package provides Cabal Setup.hs functionality to automatically integrate Verilator into your Clash project.

• Detailed introduction: https://unsafePerform.IO/blog/2020-05-07-integrating_verilator_and_clash_via_cabal/
• Example project: https://github.com/gergoerdi/clashilator-example

Usage

Suppose you have a Clash circuit that you want to simulate using Verilator, and then write Haskell code to interact with that simulation. If your Clash code looks like this:

topEntity
    :: "CLK" ::: Clock System
    -> "FOO" ::: Signal System Bit
    -> "BAR" ::: Signal System (Unsigned 4)
    -> ( "BAZ"  ::: Signal System (Unsigned 10)
       , "QUUX" ::: Signal System Bit
       )
topEntity = ...
makeTopEntity 'topEntity

and you put this in your Cabal file (x-clashilator-clock can be omitted if you have only a single clock):

custom-setup
  setup-depends: clashilator
executable MySim
  main-is: simulator.hs
  x-clashilator-clock: CLK
  x-clashilator-top-is: MyCircuit

then in your simulator.hs, you can import the "virtual" module Clash.Clashilator.FFI which provides the following definitions:

data INPUT = INPUT
    { iFOO :: Bit
    , iBAR :: Word8
    }
    deriving (Show)
instance Storable INPUT
data OUTPUT = OUTPUT
    { oBAZ :: Word16
    , oQUUX :: Bit
    }
    deriving (Show)
instance Storable OUTPUT
data Sim
simInit     :: IO (Ptr Sim)
simShutdown :: Ptr Sim -> IO ()
simStep     :: Ptr Sim -> Ptr INPUT -> Ptr OUTPUT -> IO ()

Note that input and output buses are represented as the smallest possible Word type, to improve marshalling cost when crossing the Haskell-C++ barrier.