module Main
( main
) where
import Control.Monad (forM_)
import Control.Monad.State (State, runState)
import Data.Map (Map)
import qualified Control.Monad.State.Class as State
import qualified Data.Map as Map
newtype InstructionID = InstructionID Int deriving (Eq, Ord, Show)
data Instruction
= ConstInstruction Int
| IncrementInstruction InstructionID
deriving (Show)
operands :: Instruction -> [InstructionID]
operands (ConstInstruction _) = []
operands (IncrementInstruction operand) = [operand]
type SSA = State (Int, [(InstructionID, Instruction)], Map InstructionID [InstructionID])
freshInstructionID :: SSA InstructionID
freshInstructionID = do
id <- State.gets $ \(next, _, _) -> next
State.modify $ \(next, is, us) -> (next + 1, is, us)
pure $ InstructionID id
appendInstruction :: Instruction -> SSA InstructionID
appendInstruction instruction = do
id <- freshInstructionID
State.modify $ \(next, is, us) -> (next, is ++ [(id, instruction)], us)
forM_ (operands instruction) $ \operand -> do
let alter Nothing = Just [id]
alter (Just os) = Just $ id : os
State.modify $ \(next, is, us) -> (next, is, Map.alter alter operand us)
pure id
main :: IO ()
main = print . flip runState (0, [], Map.empty) $ do
a <- appendInstruction $ ConstInstruction 42
b <- appendInstruction $ IncrementInstruction a
pure b
