Loop.hs

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{-# LANGUAGE GADTs #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE UndecidableInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}

module Feldspar.Compiler.Imperative.FromCore.Loop where

import Data.Typeable (Typeable(..))

import Prelude hiding (init)

import Language.Syntactic
import Language.Syntactic.Constructs.Binding
import Language.Syntactic.Constructs.Binding.HigherOrder

import Feldspar.Core.Types
import Feldspar.Core.Interpretation
import Feldspar.Core.Constructs.Binding
import Feldspar.Core.Constructs.Loop hiding (For, While)
import Feldspar.Core.Constructs.Literal
import qualified Feldspar.Core.Constructs.Loop as Core

import Feldspar.Compiler.Imperative.Frontend
import Feldspar.Compiler.Imperative.Representation (Program(..), Block(..),
                                                    typeof)
import Feldspar.Compiler.Imperative.FromCore.Interpretation
import Feldspar.Compiler.Imperative.FromCore.Binding (compileBind)

instance ( Compile dom dom
         , Project (CLambda Type) dom
         , Project (Literal  :|| Type) dom
         , Project (Variable :|| Type) dom
         , Project Let dom
         , ConstrainedBy dom Typeable
         )
      => Compile (Loop :|| Type) dom
  where
    compileProgSym (C' ForLoop) _ (Just loc) (len :* init :* (lam1 :$ lt1) :* Nil)
        | Just (SubConstr2 (Lambda ix)) <- prjLambda lam1
        , (bs1, lam2 :$ ixf)            <- collectLetBinders lt1
        , Just (SubConstr2 (Lambda st)) <- prjLambda lam2
        = do
            blocks <- mapM (confiscateBlock . compileBind) bs1
            let info1 = getInfo lam1
                sz = fst $ infoSize info1
                (dss, lets) = unzip $ map (\(_, Block ds (Sequence body)) -> (ds, body)) blocks
            let ix' = mkVar (compileTypeRep (infoType info1) (infoSize info1)) ix
            len' <- mkLength len (infoType $ getInfo len) sz
            (lstate, stvar) <- mkDoubleBufferState loc st
            compileProg (Just lstate) init
            (_, Block ds body) <- withAlias st lstate $ confiscateBlock 
                                $ compileProg (Just stvar) ixf >> (shallowCopyWithRefSwap lstate stvar)
            tellProg [toProg $ Block (concat dss ++ ds) (for False (lName ix') len' (litI32 1) (toBlock $ Sequence $ concat lets ++ [body]))]
            shallowAssign (Just loc) lstate 

    compileProgSym (C' WhileLoop) _ (Just loc) (init :* (lam1 :$ cond) :* (lam2 :$ body) :* Nil)
        | Just (SubConstr2 (Lambda cv)) <- prjLambda lam1
        , Just (SubConstr2 (Lambda cb)) <- prjLambda lam2
        = do
            let info2 = getInfo lam2
                info1 = getInfo lam1
            let stvar = mkVar (compileTypeRep (infoType info2) (infoSize info2)) cb
                condv = mkVar (compileTypeRep (infoType info1) (infoSize info1)) cv
            (lstate,stvar) <- mkDoubleBufferState loc cb
            compileProg (Just lstate) init
            (_, cond') <- confiscateBlock $ withAlias cv lstate $ compileProg (Just condv) cond
            (_, body') <- withAlias cb lstate $ confiscateBlock $ compileProg (Just stvar) body >> shallowCopyWithRefSwap lstate stvar
            declare condv
            tellProg [while cond' condv body']
            shallowAssign (Just loc) lstate

instance ( Compile dom dom
         , Project (CLambda Type) dom
         , Project (Literal  :|| Type) dom
         , Project (Variable :|| Type) dom
         )
      => Compile (LoopM Mut) dom
  where
    compileProgSym Core.For _ loc (len :* (lam :$ ixf) :* Nil)
        | Just (SubConstr2 (Lambda v)) <- prjLambda lam
        = do
            let ta = argType $ infoType $ getInfo lam
            let sa = fst $ infoSize $ getInfo lam
            let ix = mkVar (compileTypeRep ta sa) v
            len' <- mkLength len (infoType $ getInfo len) sa
            (_, Block ds body) <- confiscateBlock $ compileProg loc ixf
            tellProg [toProg $ Block ds (for False (lName ix) len' (litI32 1) (toBlock body))]

-- TODO Missing While
    compileProgSym Core.While _ loc (cond :* step :* Nil)
        = do
            let info1 = getInfo cond
            condv <- freshVar "cond" (infoType info1) (infoSize info1)
            (_, cond') <- confiscateBlock $ compileProg (Just condv) cond
            (_, step') <- confiscateBlock $ compileProg loc step
            tellProg [while cond' condv step']