CollectFreeVars.hs

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{-# LANGUAGE GADTs #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE OverlappingInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}

module Feldspar.Compiler.Imperative.Plugin.CollectFreeVars where

import Data.Map (Map)
import qualified Data.Map as Map
import qualified Feldspar.Compiler.Imperative.Frontend as Front
import Feldspar.Transformation

data Collect = Collect

type Collection = Map String Front.Var

instance Default Collection where
    def = Map.empty

instance Combine Collection where
    combine = Map.union

instance Transformation Collect
  where
    type From Collect     = ()
    type To Collect       = ()
    type Down Collect     = ()
    type Up Collect       = Collection
    type State Collect    = ()

instance Plugin Collect
  where
    type ExternalInfo Collect = ()
    executePlugin _ externalInfo = result . transform Collect () externalInfo

instance Transformable Collect Variable where
    transform _ _ _ v = Result v () $ Map.singleton (varName v) (Front.toInterface v)

instance Transformable Collect Block where
    transform t _ _ bl = Result bl' () diff
      where
        Result bl' _ m = defaultTransform t () () bl
        localNames = map (varName . declVar) $ locals bl'
        localMap = Map.fromList $ map (\name -> (name,())) localNames
        diff = m `Map.difference` localMap

instance Transformable Collect Program where
    transform t _ _ pr@(ParLoop idxVar _ _ _ _ _) = Result pr' () diff
      where
        Result pr' _ m = defaultTransform t () () pr
        diff = Map.delete (varName idxVar) m
    transform t _ _ prog = defaultTransform t () () prog