README.md

Haskell JIT Example

Tiny example of building a intermediate language that JIT compiles Haskell DSL into x86-64 machine code.

Usage

The factorial function can be written in assembly, taking the input value in %rcx and computing the resulting value in %rax.

.global main

main:
        mov rcx, 5
        mov rax, 1
.factor:
        mul rcx
        loop .factor
        ret

In our Haskell logic we compose these operations inside of the X86 monad.

factorial :: Int64 -> X86 ()
factorial n = do
  mov rcx (I n)
  mov rax (I 1)
  l1 <- label
  mul rcx
  loop l1
  ret

The resulting logic can be JIT compiled inside of Haskell and invoked from inside the Haskell runtime by calling out to the JIT'd memory.

main :: IO ()
main = do
  let jitsize = 256*1024
  mem <- allocateMemory jitsize
  let jitm = assemble mem (factorial 5)

  case jitm of
    Left err -> putStrLn err
    Right jitst -> do
      let machCode = _mach jitst
      fn <- jit mem machCode
      res <- fn
      putStrLn $ "Result: " <> show res

The machine code is generated.

48 c7 c1 05 00 00 00 48 c7 c0 01 00 00 00 48 f7 e1 e2 fc c3

And executed to yield the result:

Result: 120

License

Released under the MIT License. Copyright (c) 2016-2020, Stephen Diehl