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 -     * Redistributions in binary form must reproduce the above copyright
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 -       software without specific prior written permission.
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 -}

{-# LANGUAGE FlexibleInstances, TypeFamilies #-}

module Feldspar.Compiler.Plugins.Unroll where

import Feldspar.Compiler.Imperative.Representation
import Feldspar.Compiler.Options
import Prelude
import Feldspar.Compiler.Imperative.Semantics
import Feldspar.Compiler.PluginArchitecture


instance Plugin UnrollPlugin where
    type ExternalInfo UnrollPlugin = UnrollStrategy
    executePlugin UnrollPlugin ei p = case ei of
        NoUnroll -> p
        Unroll unrollCount -> fst $ executeTransformationPhase Unroll_2 Nothing $ fst $ executeTransformationPhase Unroll_1 unrollCount p
    
data UnrollPlugin = UnrollPlugin
instance TransformationPhase UnrollPlugin where
    type From UnrollPlugin = ()
    type To UnrollPlugin = ()
    type Downwards UnrollPlugin = ()
    type Upwards UnrollPlugin = ()

data Unroll_1 = Unroll_1
instance TransformationPhase Unroll_1 where
    type From Unroll_1 = ()
    type To Unroll_1 = UnrollSemInf
    type Downwards Unroll_1 = Int
    type Upwards Unroll_1 = Bool
    upwardsParallelLoop _ _ _ _ _ = True
    transformParallelLoop Unroll_1 d pl u = trParLoop1 d pl u

data Unroll_2 = Unroll_2    
instance TransformationPhase Unroll_2     where
    type From Unroll_2 = UnrollSemInf
    type To Unroll_2 = ()
    type Downwards Unroll_2 = Maybe SemInfPrg
    type Upwards Unroll_2 = ()
    downwardsProgram Unroll_2 d p
        | programSemInf p == Nothing = d
        | otherwise = programSemInf p
    transformVariable Unroll_2 d v = trVariable d v
    transformLeftValueExpression Unroll_2 d lvie u = trLVIE d lvie u

data UnrollSemInf = UnrollSemInf
instance SemanticInfo UnrollSemInf where
    type ProcedureInfo UnrollSemInf = ()
    type BlockInfo UnrollSemInf = ()
    type ProgramInfo UnrollSemInf = Maybe SemInfPrg
    type EmptyInfo UnrollSemInf = Maybe SemInfPrg
    type PrimitiveInfo UnrollSemInf = Maybe SemInfPrg
    type SequenceInfo UnrollSemInf = Maybe SemInfPrg
    type BranchInfo UnrollSemInf = ()
    type SequentialLoopInfo UnrollSemInf = ()
    type ParallelLoopInfo UnrollSemInf = ()
    type FormalParameterInfo UnrollSemInf = ()
    type LocalDeclarationInfo UnrollSemInf = ()
    type LeftValueExpressionInfo UnrollSemInf = ()
    type VariableInLeftValueInfo UnrollSemInf = ()
    type ArrayElemReferenceInfo UnrollSemInf = ()
    type InputActualParameterInfo UnrollSemInf = ()
    type OutputActualParameterInfo UnrollSemInf = ()
    type AssignmentInfo UnrollSemInf = ()
    type ProcedureCallInfo UnrollSemInf = ()
    type FunctionCallInfo UnrollSemInf = ()
    type IntConstantInfo UnrollSemInf = ()
    type FloatConstantInfo UnrollSemInf = ()
    type BoolConstantInfo UnrollSemInf = ()
    type ArrayConstantInfo UnrollSemInf = ()
    type VariableInfo UnrollSemInf = ()

instance Combine Bool where
    combine = (||)    

data SemInfPrg = SemInfPrg
    {    position    :: Int
    ,    varNames    :: [String]
    ,    loopVar        :: String
    } deriving (Eq, Show)
instance Default (Maybe SemInfPrg) where defaultValue = Nothing    

trLVIE d lvie u = case d of
    Just x -> result x
    otherwise -> orig
    where
        leftValue = leftValueExpressionContents $ lvie
        name = case leftValue of
            VariableLeftValue (VariableInLeftValue d _) -> Just $ getVarName d
            otherwise    ->    Nothing
        result x = case name of
            Just n
                | n == loopVar x -> FunctionCallExpression $ FunctionCall (FunctionCallData (InfixOp) (Numeric ImpSigned S32) ("+") ([loopVarPar, plusPar])) ()
                | otherwise -> orig
            otherwise -> orig
            where
                loopVarPar = orig
                num = position x
                plusPar = ConstantExpression $ IntConstant $ IntConstantType num ()
        orig = LeftValueExpression $ LeftValueInExpression (recursivelyTransformedLeftValueExpressionContents u ) ()        
    
trVariable d v
    | d /= Nothing && elementOf (varNames (valueFromJust d)) (getVarName v) = v { variableData = (variableData v){ variableName = (variableName $ variableData v) ++ "_u" ++ (show $ position $ valueFromJust d) },variableSemInf = ()}
    | otherwise = v {variableSemInf = ()}
    
trParLoop1 d pl u
    | ( upwardsInfoFromParallelLoopCore u ) == False && (unrollPossible || varInExpr ) = ParallelLoopProgram newParLoop
    | otherwise = ParallelLoopProgram (ParallelLoop trPL ())
    where
        newParLoop = pl { parallelLoopData = ( trPL ) 
            {    parallelLoopStep = unrollNum
            ,    parallelLoopCore = newLoopCore}
        ,    parallelLoopSemInf = ()}
        newLoopCore = origLoopCore 
                        {    blockData = (blockData origLoopCore)
                            {    blockDeclarations = unrollDecls
                            ,    blockInstructions = unrollPrg
                            }
                        ,    blockSemInf = ()}
        unrollPrg = Program (SequenceProgram $ Sequence prgs (Nothing)) (Nothing)
        prgs = map (\(i,p) -> writeSemInfToPrg p (Just $ SemInfPrg i varNames loopCounter)) $ zip [0,1..] replPrg
        writeSemInfToPrg prg semInf = prg { programSemInf = semInf }        
        replPrg = replicate unrollNum origPrg
        origPrg = blockInstructions $ blockData origLoopCore
        unrollDecls = concat $ map (\(i,ds) -> renameDecls ds i) $ zip [0,1..] replDecls
        renameDecls ds i = map (\d -> renameDeclaration d ((getVarNameDecl d) ++ "_u" ++ (show i))) ds
        replDecls = replicate unrollNum origDecls
        origDecls = blockDeclarations $ blockData origLoopCore
        origLoopCore = parallelLoopCore $ trPL
        iterExpr = numberOfIterations $ trPL
        trPL = recursivelyTransformedParallelLoopData u
        unrollNum = d
        loopCounter = getVarName $ parallelLoopConditionVariable trPL
        varNames = map (\d -> getVarNameDecl d) origDecls
        iterTemp = iterNumFromExpr iterExpr
        origIterNum = valueFromJust iterTemp
        iterNumIsConstant = isJust iterTemp
        unrollPossible = iterNumIsConstant && ( mod origIterNum d == 0 )
        varInExpr = not $ isJust iterTemp

-- helper functions : 
iterNumFromExpr (ConstantExpression (IntConstant (IntConstantType i _))) = Just i
iterNumFromExpr _ = Nothing
isJust (Just x) = True
isJust _ = False
getVarNameDecl d = getVarName $ localVariable $ localDeclarationData $ d
getVarName v = variableName $ variableData v
valueFromJust (Just v) = v
valueFromJust Nothing = error "This was Nothing"
renameDeclaration d n = d { localDeclarationData = (localDeclarationData d) { localVariable = renameVariable (localVariable $ localDeclarationData d) n } }
renameVariable v n = v { variableData = (variableData v) { variableName = n    } }
elementOf ss s = (length $ filter (\s' -> s' == s) ss) > 0