    {-# LANGUAGE CPP #-}
    {-# LANGUAGE FlexibleContexts #-}

    module GHC.Types.RepType
      (
        -- * Code generator views onto Types
        UnaryType, NvUnaryType, isNvUnaryType,
        unwrapType,

        -- * Predicates on types
        isVoidTy,

        -- * Type representation for the code generator
        typePrimRep, typePrimRep1,
        runtimeRepPrimRep, typePrimRepArgs,
        PrimRep(..), primRepToType,
        countFunRepArgs, countConRepArgs, tyConPrimRep, tyConPrimRep1,

        -- * Unboxed sum representation type
        ubxSumRepType, layoutUbxSum, typeSlotTy, SlotTy (..),
        slotPrimRep, primRepSlot
      ) where

    #include "HsVersions.h"

    import GHC.Prelude

    import GHC.Types.Basic (Arity, RepArity)
    import GHC.Core.DataCon
    import GHC.Builtin.Names
    import GHC.Core.Coercion
    import GHC.Core.TyCon
    import GHC.Core.TyCon.RecWalk
    import GHC.Core.TyCo.Rep
    import GHC.Core.Type
    import GHC.Builtin.Types.Prim
    import {-# SOURCE #-} GHC.Builtin.Types ( anyTypeOfKind )

    import GHC.Utils.Misc
    import GHC.Utils.Outputable
    import GHC.Utils.Panic

    import Data.List (sort)
    import qualified Data.IntSet as IS

    {- **********************************************************************
    *                                                                       *
                    Representation types
    *                                                                       *
    ********************************************************************** -}

    type NvUnaryType = Type
    type UnaryType   = Type
         -- Both are always a value type; i.e. its kind is TYPE rr
         -- for some rr; moreover the rr is never a variable.
         --
         --   NvUnaryType : never an unboxed tuple or sum, or void
         --
         --   UnaryType   : never an unboxed tuple or sum;
         --                 can be Void# or (# #)

    isNvUnaryType :: Type -> Bool
    isNvUnaryType :: Type -> Bool
    isNvUnaryType Type
    ty
      | [PrimRep
    _] <- HasDebugCallStack => Type -> [PrimRep]
    Type -> [PrimRep]
    typePrimRep Type
    ty
      = Bool
    True
      | Bool
    otherwise
      = Bool
    False

    -- INVARIANT: the result list is never empty.
    typePrimRepArgs :: HasDebugCallStack => Type -> [PrimRep]
    typePrimRepArgs :: HasDebugCallStack => Type -> [PrimRep]
    typePrimRepArgs Type
    ty
      | [] <- [PrimRep]
    reps
      = [PrimRep
    VoidRep]
      | Bool
    otherwise
      = [PrimRep]
    reps
      where
        reps :: [PrimRep]
    reps = HasDebugCallStack => Type -> [PrimRep]
    Type -> [PrimRep]
    typePrimRep Type
    ty

    -- | Gets rid of the stuff that prevents us from understanding the
    -- runtime representation of a type. Including:
    --   1. Casts
    --   2. Newtypes
    --   3. Foralls
    --   4. Synonyms
    -- But not type/data families, because we don't have the envs to hand.
    unwrapType :: Type -> Type
    unwrapType :: Type -> Type
    unwrapType Type
    ty
      | Just (()
    _, Type
    unwrapped)
          <- NormaliseStepper () -> (() -> () -> ()) -> Type -> Maybe ((), Type)
    forall ev.
    NormaliseStepper ev -> (ev -> ev -> ev) -> Type -> Maybe (ev, Type)
    topNormaliseTypeX NormaliseStepper ()
    stepper () -> () -> ()
    forall a. Monoid a => a -> a -> a
    mappend Type
    inner_ty
      = Type
    unwrapped
      | Bool
    otherwise
      = Type
    inner_ty
      where
        inner_ty :: Type
    inner_ty = Type -> Type
    go Type
    ty

        go :: Type -> Type
    go Type
    t | Just Type
    t' <- Type -> Maybe Type
    coreView Type
    t = Type -> Type
    go Type
    t'
        go (ForAllTy TyCoVarBinder
    _ Type
    t)            = Type -> Type
    go Type
    t
        go (CastTy Type
    t KindCoercion
    _)              = Type -> Type
    go Type
    t
        go Type
    t                         = Type
    t

         -- cf. Coercion.unwrapNewTypeStepper
        stepper :: NormaliseStepper ()
    stepper RecTcChecker
    rec_nts TyCon
    tc [Type]
    tys
          | Just (Type
    ty', KindCoercion
    _) <- TyCon -> [Type] -> Maybe (Type, KindCoercion)
    instNewTyCon_maybe TyCon
    tc [Type]
    tys
          = case RecTcChecker -> TyCon -> Maybe RecTcChecker
    checkRecTc RecTcChecker
    rec_nts TyCon
    tc of
              Just RecTcChecker
    rec_nts' -> RecTcChecker -> Type -> () -> NormaliseStepResult ()
    forall ev. RecTcChecker -> Type -> ev -> NormaliseStepResult ev
    NS_Step RecTcChecker
    rec_nts' (Type -> Type
    go Type
    ty') ()
              Maybe RecTcChecker
    Nothing       -> NormaliseStepResult ()
    forall ev. NormaliseStepResult ev
    NS_Abort   -- infinite newtypes
          | Bool
    otherwise
          = NormaliseStepResult ()
    forall ev. NormaliseStepResult ev
    NS_Done

    countFunRepArgs :: Arity -> Type -> RepArity
    countFunRepArgs :: Int -> Type -> Int
    countFunRepArgs Int
    0 Type
    _
      = Int
    0
    countFunRepArgs Int
    n Type
    ty
      | FunTy AnonArgFlag
    _ Type
    _ Type
    arg Type
    res <- Type -> Type
    unwrapType Type
    ty
      = [PrimRep] -> Int
    forall (t :: * -> *) a. Foldable t => t a -> Int
    length (HasDebugCallStack => Type -> [PrimRep]
    Type -> [PrimRep]
    typePrimRepArgs Type
    arg) Int -> Int -> Int
    forall a. Num a => a -> a -> a
    + Int -> Type -> Int
    countFunRepArgs (Int
    n Int -> Int -> Int
    forall a. Num a => a -> a -> a
    - Int
    1) Type
    res
      | Bool
    otherwise
      = String -> SDoc -> Int
    forall a. HasCallStack => String -> SDoc -> a
    pprPanic String
    "countFunRepArgs: arity greater than type can handle" ((Int, Type, [PrimRep]) -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr (Int
    n, Type
    ty, HasDebugCallStack => Type -> [PrimRep]
    Type -> [PrimRep]
    typePrimRep Type
    ty))

    countConRepArgs :: DataCon -> RepArity
    countConRepArgs :: DataCon -> Int
    countConRepArgs DataCon
    dc = Int -> Type -> Int
    go (DataCon -> Int
    dataConRepArity DataCon
    dc) (DataCon -> Type
    dataConRepType DataCon
    dc)
      where
        go :: Arity -> Type -> RepArity
        go :: Int -> Type -> Int
    go Int
    0 Type
    _
          = Int
    0
        go Int
    n Type
    ty
          | FunTy AnonArgFlag
    _ Type
    _ Type
    arg Type
    res <- Type -> Type
    unwrapType Type
    ty
          = [PrimRep] -> Int
    forall (t :: * -> *) a. Foldable t => t a -> Int
    length (HasDebugCallStack => Type -> [PrimRep]
    Type -> [PrimRep]
    typePrimRep Type
    arg) Int -> Int -> Int
    forall a. Num a => a -> a -> a
    + Int -> Type -> Int
    go (Int
    n Int -> Int -> Int
    forall a. Num a => a -> a -> a
    - Int
    1) Type
    res
          | Bool
    otherwise
          = String -> SDoc -> Int
    forall a. HasCallStack => String -> SDoc -> a
    pprPanic String
    "countConRepArgs: arity greater than type can handle" ((Int, Type, [PrimRep]) -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr (Int
    n, Type
    ty, HasDebugCallStack => Type -> [PrimRep]
    Type -> [PrimRep]
    typePrimRep Type
    ty))

    -- | True if the type has zero width.
    isVoidTy :: Type -> Bool
    isVoidTy :: Type -> Bool
    isVoidTy = [PrimRep] -> Bool
    forall (t :: * -> *) a. Foldable t => t a -> Bool
    null ([PrimRep] -> Bool) -> (Type -> [PrimRep]) -> Type -> Bool
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . HasDebugCallStack => Type -> [PrimRep]
    Type -> [PrimRep]
    typePrimRep

    {- **********************************************************************
    *                                                                       *
                    Unboxed sums
     See Note [Translating unboxed sums to unboxed tuples] in GHC.Stg.Unarise
    *                                                                       *
    ********************************************************************** -}

    type SortedSlotTys = [SlotTy]

    -- | Given the arguments of a sum type constructor application,
    --   return the unboxed sum rep type.
    --
    -- E.g.
    --
    --   (# Int# | Maybe Int | (# Int#, Float# #) #)
    --
    -- We call `ubxSumRepType [ [IntRep], [LiftedRep], [IntRep, FloatRep] ]`,
    -- which returns [WordSlot, PtrSlot, WordSlot, FloatSlot]
    --
    -- INVARIANT: Result slots are sorted (via Ord SlotTy), except that at the head
    -- of the list we have the slot for the tag.
    ubxSumRepType :: [[PrimRep]] -> [SlotTy]
    ubxSumRepType :: [[PrimRep]] -> SortedSlotTys
    ubxSumRepType [[PrimRep]]
    constrs0
      -- These first two cases never classify an actual unboxed sum, which always
      -- has at least two disjuncts. But it could happen if a user writes, e.g.,
      -- forall (a :: TYPE (SumRep [IntRep])). ...
      -- which could never be instantiated. We still don't want to panic.
      | [[PrimRep]]
    constrs0 [[PrimRep]] -> Int -> Bool
    forall a. [a] -> Int -> Bool
    `lengthLessThan` Int
    2
      = [SlotTy
    WordSlot]

      | Bool
    otherwise
      = let
          combine_alts :: [SortedSlotTys]  -- slots of constructors
                       -> SortedSlotTys    -- final slots
          combine_alts :: [SortedSlotTys] -> SortedSlotTys
    combine_alts [SortedSlotTys]
    constrs = (SortedSlotTys -> SortedSlotTys -> SortedSlotTys)
    -> SortedSlotTys -> [SortedSlotTys] -> SortedSlotTys
    forall (t :: * -> *) b a.
    Foldable t =>
    (b -> a -> b) -> b -> t a -> b
    foldl' SortedSlotTys -> SortedSlotTys -> SortedSlotTys
    merge [] [SortedSlotTys]
    constrs

          merge :: SortedSlotTys -> SortedSlotTys -> SortedSlotTys
          merge :: SortedSlotTys -> SortedSlotTys -> SortedSlotTys
    merge SortedSlotTys
    existing_slots []
            = SortedSlotTys
    existing_slots
          merge [] SortedSlotTys
    needed_slots
            = SortedSlotTys
    needed_slots
          merge (SlotTy
    es : SortedSlotTys
    ess) (SlotTy
    s : SortedSlotTys
    ss)
            | Just SlotTy
    s' <- SlotTy
    s SlotTy -> SlotTy -> Maybe SlotTy
    `fitsIn` SlotTy
    es
            = -- found a slot, use it
              SlotTy
    s' SlotTy -> SortedSlotTys -> SortedSlotTys
    forall a. a -> [a] -> [a]
    : SortedSlotTys -> SortedSlotTys -> SortedSlotTys
    merge SortedSlotTys
    ess SortedSlotTys
    ss
            | SlotTy
    s SlotTy -> SlotTy -> Bool
    forall a. Ord a => a -> a -> Bool
    < SlotTy
    es
            = -- we need a new slot and this is the right place for it
              SlotTy
    s SlotTy -> SortedSlotTys -> SortedSlotTys
    forall a. a -> [a] -> [a]
    : SortedSlotTys -> SortedSlotTys -> SortedSlotTys
    merge (SlotTy
    es SlotTy -> SortedSlotTys -> SortedSlotTys
    forall a. a -> [a] -> [a]
    : SortedSlotTys
    ess) SortedSlotTys
    ss
            | Bool
    otherwise
            = -- keep searching for a slot
              SlotTy
    es SlotTy -> SortedSlotTys -> SortedSlotTys
    forall a. a -> [a] -> [a]
    : SortedSlotTys -> SortedSlotTys -> SortedSlotTys
    merge SortedSlotTys
    ess (SlotTy
    s SlotTy -> SortedSlotTys -> SortedSlotTys
    forall a. a -> [a] -> [a]
    : SortedSlotTys
    ss)

          -- Nesting unboxed tuples and sums is OK, so we need to flatten first.
          rep :: [PrimRep] -> SortedSlotTys
          rep :: [PrimRep] -> SortedSlotTys
    rep [PrimRep]
    ty = SortedSlotTys -> SortedSlotTys
    forall a. Ord a => [a] -> [a]
    sort ((PrimRep -> SlotTy) -> [PrimRep] -> SortedSlotTys
    forall a b. (a -> b) -> [a] -> [b]
    map PrimRep -> SlotTy
    primRepSlot [PrimRep]
    ty)

          sumRep :: SortedSlotTys
    sumRep = SlotTy
    WordSlot SlotTy -> SortedSlotTys -> SortedSlotTys
    forall a. a -> [a] -> [a]
    : [SortedSlotTys] -> SortedSlotTys
    combine_alts (([PrimRep] -> SortedSlotTys) -> [[PrimRep]] -> [SortedSlotTys]
    forall a b. (a -> b) -> [a] -> [b]
    map [PrimRep] -> SortedSlotTys
    rep [[PrimRep]]
    constrs0)
                   -- WordSlot: for the tag of the sum
        in
          SortedSlotTys
    sumRep

    layoutUbxSum :: SortedSlotTys -- Layout of sum. Does not include tag.
                                  -- We assume that they are in increasing order
                 -> [SlotTy]      -- Slot types of things we want to map to locations in the
                                  -- sum layout
                 -> [Int]         -- Where to map 'things' in the sum layout
    layoutUbxSum :: SortedSlotTys -> SortedSlotTys -> [Int]
    layoutUbxSum SortedSlotTys
    sum_slots0 SortedSlotTys
    arg_slots0 =
        SortedSlotTys -> IntSet -> [Int]
    go SortedSlotTys
    arg_slots0 IntSet
    IS.empty
      where
        go :: [SlotTy] -> IS.IntSet -> [Int]
        go :: SortedSlotTys -> IntSet -> [Int]
    go [] IntSet
    _
          = []
        go (SlotTy
    arg : SortedSlotTys
    args) IntSet
    used
          = let slot_idx :: Int
    slot_idx = SlotTy -> Int -> SortedSlotTys -> IntSet -> Int
    findSlot SlotTy
    arg Int
    0 SortedSlotTys
    sum_slots0 IntSet
    used
             in Int
    slot_idx Int -> [Int] -> [Int]
    forall a. a -> [a] -> [a]
    : SortedSlotTys -> IntSet -> [Int]
    go SortedSlotTys
    args (Int -> IntSet -> IntSet
    IS.insert Int
    slot_idx IntSet
    used)

        findSlot :: SlotTy -> Int -> SortedSlotTys -> IS.IntSet -> Int
        findSlot :: SlotTy -> Int -> SortedSlotTys -> IntSet -> Int
    findSlot SlotTy
    arg Int
    slot_idx (SlotTy
    slot : SortedSlotTys
    slots) IntSet
    useds
          | Bool -> Bool
    not (Int -> IntSet -> Bool
    IS.member Int
    slot_idx IntSet
    useds)
          , SlotTy -> Maybe SlotTy
    forall a. a -> Maybe a
    Just SlotTy
    slot Maybe SlotTy -> Maybe SlotTy -> Bool
    forall a. Eq a => a -> a -> Bool
    == SlotTy
    arg SlotTy -> SlotTy -> Maybe SlotTy
    `fitsIn` SlotTy
    slot
          = Int
    slot_idx
          | Bool
    otherwise
          = SlotTy -> Int -> SortedSlotTys -> IntSet -> Int
    findSlot SlotTy
    arg (Int
    slot_idx Int -> Int -> Int
    forall a. Num a => a -> a -> a
    + Int
    1) SortedSlotTys
    slots IntSet
    useds
        findSlot SlotTy
    _ Int
    _ [] IntSet
    _
          = String -> SDoc -> Int
    forall a. HasCallStack => String -> SDoc -> a
    pprPanic String
    "findSlot" (String -> SDoc
    text String
    "Can't find slot" SDoc -> SDoc -> SDoc
    $$ SortedSlotTys -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr SortedSlotTys
    sum_slots0 SDoc -> SDoc -> SDoc
    $$ SortedSlotTys -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr SortedSlotTys
    arg_slots0)

    --------------------------------------------------------------------------------

    -- We have 3 kinds of slots:
    --
    --   - Pointer slot: Only shared between actual pointers to Haskell heap (i.e.
    --     boxed objects). These come in two variants: Lifted and unlifted (see
    --     #19645).
    --
    --   - Word slots: Shared between IntRep, WordRep, Int64Rep, Word64Rep, AddrRep.
    --
    --   - Float slots: Shared between floating point types.
    --
    --   - Void slots: Shared between void types. Not used in sums.
    --
    -- TODO(michalt): We should probably introduce `SlotTy`s for 8-/16-/32-bit
    -- values, so that we can pack things more tightly.
    data SlotTy = PtrLiftedSlot | PtrUnliftedSlot | WordSlot | Word64Slot | FloatSlot | DoubleSlot
      deriving (SlotTy -> SlotTy -> Bool
    (SlotTy -> SlotTy -> Bool)
    -> (SlotTy -> SlotTy -> Bool) -> Eq SlotTy
    forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
    /= :: SlotTy -> SlotTy -> Bool
    $c/= :: SlotTy -> SlotTy -> Bool
    == :: SlotTy -> SlotTy -> Bool
    $c== :: SlotTy -> SlotTy -> Bool
    Eq, Eq SlotTy
    Eq SlotTy
    -> (SlotTy -> SlotTy -> Ordering)
    -> (SlotTy -> SlotTy -> Bool)
    -> (SlotTy -> SlotTy -> Bool)
    -> (SlotTy -> SlotTy -> Bool)
    -> (SlotTy -> SlotTy -> Bool)
    -> (SlotTy -> SlotTy -> SlotTy)
    -> (SlotTy -> SlotTy -> SlotTy)
    -> Ord SlotTy
    SlotTy -> SlotTy -> Bool
    SlotTy -> SlotTy -> Ordering
    SlotTy -> SlotTy -> SlotTy
    forall a.
    Eq a
    -> (a -> a -> Ordering)
    -> (a -> a -> Bool)
    -> (a -> a -> Bool)
    -> (a -> a -> Bool)
    -> (a -> a -> Bool)
    -> (a -> a -> a)
    -> (a -> a -> a)
    -> Ord a
    min :: SlotTy -> SlotTy -> SlotTy
    $cmin :: SlotTy -> SlotTy -> SlotTy
    max :: SlotTy -> SlotTy -> SlotTy
    $cmax :: SlotTy -> SlotTy -> SlotTy
    >= :: SlotTy -> SlotTy -> Bool
    $c>= :: SlotTy -> SlotTy -> Bool
    > :: SlotTy -> SlotTy -> Bool
    $c> :: SlotTy -> SlotTy -> Bool
    <= :: SlotTy -> SlotTy -> Bool
    $c<= :: SlotTy -> SlotTy -> Bool
    < :: SlotTy -> SlotTy -> Bool
    $c< :: SlotTy -> SlotTy -> Bool
    compare :: SlotTy -> SlotTy -> Ordering
    $ccompare :: SlotTy -> SlotTy -> Ordering
    Ord)
        -- Constructor order is important! If slot A could fit into slot B
        -- then slot A must occur first.  E.g.  FloatSlot before DoubleSlot
        --
        -- We are assuming that WordSlot is smaller than or equal to Word64Slot
        -- (would not be true on a 128-bit machine)

    instance Outputable SlotTy where
      ppr :: SlotTy -> SDoc
    ppr SlotTy
    PtrLiftedSlot   = String -> SDoc
    text String
    "PtrLiftedSlot"
      ppr SlotTy
    PtrUnliftedSlot = String -> SDoc
    text String
    "PtrUnliftedSlot"
      ppr SlotTy
    Word64Slot      = String -> SDoc
    text String
    "Word64Slot"
      ppr SlotTy
    WordSlot        = String -> SDoc
    text String
    "WordSlot"
      ppr SlotTy
    DoubleSlot      = String -> SDoc
    text String
    "DoubleSlot"
      ppr SlotTy
    FloatSlot       = String -> SDoc
    text String
    "FloatSlot"

    typeSlotTy :: UnaryType -> Maybe SlotTy
    typeSlotTy :: Type -> Maybe SlotTy
    typeSlotTy Type
    ty
      | Type -> Bool
    isVoidTy Type
    ty
      = Maybe SlotTy
    forall a. Maybe a
    Nothing
      | Bool
    otherwise
      = SlotTy -> Maybe SlotTy
    forall a. a -> Maybe a
    Just (PrimRep -> SlotTy
    primRepSlot (HasDebugCallStack => Type -> PrimRep
    Type -> PrimRep
    typePrimRep1 Type
    ty))

    primRepSlot :: PrimRep -> SlotTy
    primRepSlot :: PrimRep -> SlotTy
    primRepSlot PrimRep
    VoidRep     = String -> SDoc -> SlotTy
    forall a. HasCallStack => String -> SDoc -> a
    pprPanic String
    "primRepSlot" (String -> SDoc
    text String
    "No slot for VoidRep")
    primRepSlot PrimRep
    LiftedRep   = SlotTy
    PtrLiftedSlot
    primRepSlot PrimRep
    UnliftedRep = SlotTy
    PtrUnliftedSlot
    primRepSlot PrimRep
    IntRep      = SlotTy
    WordSlot
    primRepSlot PrimRep
    Int8Rep     = SlotTy
    WordSlot
    primRepSlot PrimRep
    Int16Rep    = SlotTy
    WordSlot
    primRepSlot PrimRep
    Int32Rep    = SlotTy
    WordSlot
    primRepSlot PrimRep
    Int64Rep    = SlotTy
    Word64Slot
    primRepSlot PrimRep
    WordRep     = SlotTy
    WordSlot
    primRepSlot PrimRep
    Word8Rep    = SlotTy
    WordSlot
    primRepSlot PrimRep
    Word16Rep   = SlotTy
    WordSlot
    primRepSlot PrimRep
    Word32Rep   = SlotTy
    WordSlot
    primRepSlot PrimRep
    Word64Rep   = SlotTy
    Word64Slot
    primRepSlot PrimRep
    AddrRep     = SlotTy
    WordSlot
    primRepSlot PrimRep
    FloatRep    = SlotTy
    FloatSlot
    primRepSlot PrimRep
    DoubleRep   = SlotTy
    DoubleSlot
    primRepSlot VecRep{}    = String -> SDoc -> SlotTy
    forall a. HasCallStack => String -> SDoc -> a
    pprPanic String
    "primRepSlot" (String -> SDoc
    text String
    "No slot for VecRep")

    slotPrimRep :: SlotTy -> PrimRep
    slotPrimRep :: SlotTy -> PrimRep
    slotPrimRep SlotTy
    PtrLiftedSlot   = PrimRep
    LiftedRep
    slotPrimRep SlotTy
    PtrUnliftedSlot = PrimRep
    UnliftedRep
    slotPrimRep SlotTy
    Word64Slot      = PrimRep
    Word64Rep
    slotPrimRep SlotTy
    WordSlot        = PrimRep
    WordRep
    slotPrimRep SlotTy
    DoubleSlot      = PrimRep
    DoubleRep
    slotPrimRep SlotTy
    FloatSlot       = PrimRep
    FloatRep

    -- | Returns the bigger type if one fits into the other. (commutative)
    fitsIn :: SlotTy -> SlotTy -> Maybe SlotTy
    fitsIn :: SlotTy -> SlotTy -> Maybe SlotTy
    fitsIn SlotTy
    ty1 SlotTy
    ty2
      | SlotTy
    ty1 SlotTy -> SlotTy -> Bool
    forall a. Eq a => a -> a -> Bool
    == SlotTy
    ty2
      = SlotTy -> Maybe SlotTy
    forall a. a -> Maybe a
    Just SlotTy
    ty1
      | SlotTy -> Bool
    isWordSlot SlotTy
    ty1 Bool -> Bool -> Bool
    && SlotTy -> Bool
    isWordSlot SlotTy
    ty2
      = SlotTy -> Maybe SlotTy
    forall a. a -> Maybe a
    Just (SlotTy -> SlotTy -> SlotTy
    forall a. Ord a => a -> a -> a
    max SlotTy
    ty1 SlotTy
    ty2)
      | SlotTy -> Bool
    isFloatSlot SlotTy
    ty1 Bool -> Bool -> Bool
    && SlotTy -> Bool
    isFloatSlot SlotTy
    ty2
      = SlotTy -> Maybe SlotTy
    forall a. a -> Maybe a
    Just (SlotTy -> SlotTy -> SlotTy
    forall a. Ord a => a -> a -> a
    max SlotTy
    ty1 SlotTy
    ty2)
      | Bool
    otherwise
      = Maybe SlotTy
    forall a. Maybe a
    Nothing
      where
        isWordSlot :: SlotTy -> Bool
    isWordSlot SlotTy
    Word64Slot = Bool
    True
        isWordSlot SlotTy
    WordSlot   = Bool
    True
        isWordSlot SlotTy
    _          = Bool
    False

        isFloatSlot :: SlotTy -> Bool
    isFloatSlot SlotTy
    DoubleSlot = Bool
    True
        isFloatSlot SlotTy
    FloatSlot  = Bool
    True
        isFloatSlot SlotTy
    _          = Bool
    False

    {- **********************************************************************
    *                                                                       *
                       PrimRep
    *                                                                       *
    *************************************************************************

    Note [RuntimeRep and PrimRep]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    This Note describes the relationship between GHC.Types.RuntimeRep
    (of levity-polymorphism fame) and GHC.Core.TyCon.PrimRep, as these types
    are closely related.

    A "primitive entity" is one that can be
     * stored in one register
     * manipulated with one machine instruction

    Examples include:
     * a 32-bit integer
     * a 32-bit float
     * a 64-bit float
     * a machine address (heap pointer), etc.
     * a quad-float (on a machine with SIMD register and instructions)
     * ...etc...

    The "representation or a primitive entity" specifies what kind of register is
    needed and how many bits are required. The data type GHC.Core.TyCon.PrimRep
    enumerates all the possibilities.

    data PrimRep
      = VoidRep
      | LiftedRep     -- ^ Lifted pointer
      | UnliftedRep   -- ^ Unlifted pointer
      | Int8Rep       -- ^ Signed, 8-bit value
      | Int16Rep      -- ^ Signed, 16-bit value
      ...etc...
      | VecRep Int PrimElemRep  -- ^ SIMD fixed-width vector

    The Haskell source language is a bit more flexible: a single value may need multiple PrimReps.
    For example

      utup :: (# Int, Int #) -> Bool
      utup x = ...

    Here x :: (# Int, Int #), and that takes two registers, and two instructions to move around.
    Unboxed sums are similar.

    Every Haskell expression e has a type ty, whose kind is of form TYPE rep
       e :: ty :: TYPE rep
    where rep :: RuntimeRep. Here rep describes the runtime representation for e's value,
    but RuntimeRep has some extra cases:

    data RuntimeRep = VecRep VecCount VecElem   -- ^ a SIMD vector type
                    | TupleRep [RuntimeRep]     -- ^ An unboxed tuple of the given reps
                    | SumRep [RuntimeRep]       -- ^ An unboxed sum of the given reps
                    | BoxedRep Levity -- ^ boxed; represented by a pointer
                    | IntRep          -- ^ signed, word-sized value
                    ...etc...
    data Levity     = Lifted
                    | Unlifted

    It's all in 1-1 correspondence with PrimRep except for TupleRep and SumRep,
    which describe unboxed products and sums respectively. RuntimeRep is defined
    in the library ghc-prim:GHC.Types. It is also "wired-in" to GHC: see
    GHC.Builtin.Types.runtimeRepTyCon. The unarisation pass, in GHC.Stg.Unarise, transforms the
    program, so that every variable has a type that has a PrimRep. For
    example, unarisation transforms our utup function above, to take two Int
    arguments instead of one (# Int, Int #) argument.

    Also, note that boxed types are represented slightly differently in RuntimeRep
    and PrimRep. PrimRep just has the nullary LiftedRep and UnliftedRep data
    constructors. RuntimeRep has a BoxedRep data constructor, which accepts a
    Levity. The subtle distinction is that since BoxedRep can accept a variable
    argument, RuntimeRep can talk about levity polymorphic types. PrimRep, by
    contrast, cannot.

    See also Note [Getting from RuntimeRep to PrimRep] and Note [VoidRep].

    Note [VoidRep]
    ~~~~~~~~~~~~~~
    PrimRep contains a constructor VoidRep, while RuntimeRep does
    not. Yet representations are often characterised by a list of PrimReps,
    where a void would be denoted as []. (See also Note [RuntimeRep and PrimRep].)

    However, after the unariser, all identifiers have exactly one PrimRep, but
    void arguments still exist. Thus, PrimRep includes VoidRep to describe these
    binders. Perhaps post-unariser representations (which need VoidRep) should be
    a different type than pre-unariser representations (which use a list and do
    not need VoidRep), but we have what we have.

    RuntimeRep instead uses TupleRep '[] to denote a void argument. When
    converting a TupleRep '[] into a list of PrimReps, we get an empty list.

    Note [Getting from RuntimeRep to PrimRep]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    General info on RuntimeRep and PrimRep is in Note [RuntimeRep and PrimRep].

    How do we get from an Id to the list or PrimReps used to store it? We get
    the Id's type ty (using idType), then ty's kind ki (using typeKind), then
    pattern-match on ki to extract rep (in kindPrimRep), then extract the PrimRep
    from the RuntimeRep (in runtimeRepPrimRep).

    We now must convert the RuntimeRep to a list of PrimReps. Let's look at two
    examples:

      1. x :: Int#
      2. y :: (# Int, Word# #)

    With these types, we can extract these kinds:

      1. Int# :: TYPE IntRep
      2. (# Int, Word# #) :: TYPE (TupleRep [LiftedRep, WordRep])

    In the end, we will get these PrimReps:

      1. [IntRep]
      2. [LiftedRep, WordRep]

    It would thus seem that we should have a function somewhere of
    type `RuntimeRep -> [PrimRep]`. This doesn't work though: when we
    look at the argument of TYPE, we get something of type Type (of course).
    RuntimeRep exists in the user's program, but not in GHC as such.
    Instead, we must decompose the Type of kind RuntimeRep into tycons and
    extract the PrimReps from the TyCons. This is what runtimeRepPrimRep does:
    it takes a Type and returns a [PrimRep]

    runtimeRepPrimRep works by using tyConRuntimeRepInfo. That function
    should be passed the TyCon produced by promoting one of the constructors
    of RuntimeRep into type-level data. The RuntimeRep promoted datacons are
    associated with a RuntimeRepInfo (stored directly in the PromotedDataCon
    constructor of TyCon). This pairing happens in GHC.Builtin.Types. A RuntimeRepInfo
    usually(*) contains a function from [Type] to [PrimRep]: the [Type] are
    the arguments to the promoted datacon. These arguments are necessary
    for the TupleRep and SumRep constructors, so that this process can recur,
    producing a flattened list of PrimReps. Calling this extracted function
    happens in runtimeRepPrimRep; the functions themselves are defined in
    tupleRepDataCon and sumRepDataCon, both in GHC.Builtin.Types.

    The (*) above is to support vector representations. RuntimeRep refers
    to VecCount and VecElem, whose promoted datacons have nuggets of information
    related to vectors; these form the other alternatives for RuntimeRepInfo.

    Returning to our examples, the Types we get (after stripping off TYPE) are

      1. TyConApp (PromotedDataCon "IntRep") []
      2. TyConApp (PromotedDataCon "TupleRep")
                  [TyConApp (PromotedDataCon ":")
                            [ TyConApp (AlgTyCon "RuntimeRep") []
                            , TyConApp (PromotedDataCon "LiftedRep") []
                            , TyConApp (PromotedDataCon ":")
                                       [ TyConApp (AlgTyCon "RuntimeRep") []
                                       , TyConApp (PromotedDataCon "WordRep") []
                                       , TyConApp (PromotedDataCon "'[]")
                                                  [TyConApp (AlgTyCon "RuntimeRep") []]]]]

    runtimeRepPrimRep calls tyConRuntimeRepInfo on (PromotedDataCon "IntRep"), resp.
    (PromotedDataCon "TupleRep"), extracting a function that will produce the PrimReps.
    In example 1, this function is passed an empty list (the empty list of args to IntRep)
    and returns the PrimRep IntRep. (See the definition of runtimeRepSimpleDataCons in
    GHC.Builtin.Types and its helper function mk_runtime_rep_dc.) Example 2 passes the promoted
    list as the one argument to the extracted function. The extracted function is defined
    as prim_rep_fun within tupleRepDataCon in GHC.Builtin.Types. It takes one argument, decomposes
    the promoted list (with extractPromotedList), and then recurs back to runtimeRepPrimRep
    to process the LiftedRep and WordRep, concatentating the results.

    -}

    -- | Discovers the primitive representation of a 'Type'. Returns
    -- a list of 'PrimRep': it's a list because of the possibility of
    -- no runtime representation (void) or multiple (unboxed tuple/sum)
    -- See also Note [Getting from RuntimeRep to PrimRep]
    typePrimRep :: HasDebugCallStack => Type -> [PrimRep]
    typePrimRep :: HasDebugCallStack => Type -> [PrimRep]
    typePrimRep Type
    ty = HasDebugCallStack => SDoc -> Type -> [PrimRep]
    SDoc -> Type -> [PrimRep]
    kindPrimRep (String -> SDoc
    text String
    "typePrimRep" SDoc -> SDoc -> SDoc
    <+>
                                  SDoc -> SDoc
    parens (Type -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr Type
    ty SDoc -> SDoc -> SDoc
    <+> SDoc
    dcolon SDoc -> SDoc -> SDoc
    <+> Type -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr (HasDebugCallStack => Type -> Type
    Type -> Type
    typeKind Type
    ty)))
                                 (HasDebugCallStack => Type -> Type
    Type -> Type
    typeKind Type
    ty)

    -- | Like 'typePrimRep', but assumes that there is precisely one 'PrimRep' output;
    -- an empty list of PrimReps becomes a VoidRep.
    -- This assumption holds after unarise, see Note [Post-unarisation invariants].
    -- Before unarise it may or may not hold.
    -- See also Note [RuntimeRep and PrimRep] and Note [VoidRep]
    typePrimRep1 :: HasDebugCallStack => UnaryType -> PrimRep
    typePrimRep1 :: HasDebugCallStack => Type -> PrimRep
    typePrimRep1 Type
    ty = case HasDebugCallStack => Type -> [PrimRep]
    Type -> [PrimRep]
    typePrimRep Type
    ty of
      []    -> PrimRep
    VoidRep
      [PrimRep
    rep] -> PrimRep
    rep
      [PrimRep]
    _     -> String -> SDoc -> PrimRep
    forall a. HasCallStack => String -> SDoc -> a
    pprPanic String
    "typePrimRep1" (Type -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr Type
    ty SDoc -> SDoc -> SDoc
    $$ [PrimRep] -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr (HasDebugCallStack => Type -> [PrimRep]
    Type -> [PrimRep]
    typePrimRep Type
    ty))

    -- | Find the runtime representation of a 'TyCon'. Defined here to
    -- avoid module loops. Returns a list of the register shapes necessary.
    -- See also Note [Getting from RuntimeRep to PrimRep]
    tyConPrimRep :: HasDebugCallStack => TyCon -> [PrimRep]
    tyConPrimRep :: HasDebugCallStack => TyCon -> [PrimRep]
    tyConPrimRep TyCon
    tc
      = HasDebugCallStack => SDoc -> Type -> [PrimRep]
    SDoc -> Type -> [PrimRep]
    kindPrimRep (String -> SDoc
    text String
    "kindRep tc" SDoc -> SDoc -> SDoc
    <+> TyCon -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr TyCon
    tc SDoc -> SDoc -> SDoc
    $$ Type -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr Type
    res_kind)
                    Type
    res_kind
      where
        res_kind :: Type
    res_kind = TyCon -> Type
    tyConResKind TyCon
    tc

    -- | Like 'tyConPrimRep', but assumed that there is precisely zero or
    -- one 'PrimRep' output
    -- See also Note [Getting from RuntimeRep to PrimRep] and Note [VoidRep]
    tyConPrimRep1 :: HasDebugCallStack => TyCon -> PrimRep
    tyConPrimRep1 :: HasDebugCallStack => TyCon -> PrimRep
    tyConPrimRep1 TyCon
    tc = case HasDebugCallStack => TyCon -> [PrimRep]
    TyCon -> [PrimRep]
    tyConPrimRep TyCon
    tc of
      []    -> PrimRep
    VoidRep
      [PrimRep
    rep] -> PrimRep
    rep
      [PrimRep]
    _     -> String -> SDoc -> PrimRep
    forall a. HasCallStack => String -> SDoc -> a
    pprPanic String
    "tyConPrimRep1" (TyCon -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr TyCon
    tc SDoc -> SDoc -> SDoc
    $$ [PrimRep] -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr (HasDebugCallStack => TyCon -> [PrimRep]
    TyCon -> [PrimRep]
    tyConPrimRep TyCon
    tc))

    -- | Take a kind (of shape @TYPE rr@) and produce the 'PrimRep's
    -- of values of types of this kind.
    -- See also Note [Getting from RuntimeRep to PrimRep]
    kindPrimRep :: HasDebugCallStack => SDoc -> Kind -> [PrimRep]
    kindPrimRep :: HasDebugCallStack => SDoc -> Type -> [PrimRep]
    kindPrimRep SDoc
    doc Type
    ki
      | Just Type
    ki' <- Type -> Maybe Type
    coreView Type
    ki
      = HasDebugCallStack => SDoc -> Type -> [PrimRep]
    SDoc -> Type -> [PrimRep]
    kindPrimRep SDoc
    doc Type
    ki'
    kindPrimRep SDoc
    doc (TyConApp TyCon
    typ [Type
    runtime_rep])
      = ASSERT( typ `hasKey` tYPETyConKey )
        HasDebugCallStack => SDoc -> Type -> [PrimRep]
    SDoc -> Type -> [PrimRep]
    runtimeRepPrimRep SDoc
    doc Type
    runtime_rep
    kindPrimRep SDoc
    doc Type
    ki
      = String -> SDoc -> [PrimRep]
    forall a. HasCallStack => String -> SDoc -> a
    pprPanic String
    "kindPrimRep" (Type -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr Type
    ki SDoc -> SDoc -> SDoc
    $$ SDoc
    doc)

    -- | Take a type of kind RuntimeRep and extract the list of 'PrimRep' that
    -- it encodes. See also Note [Getting from RuntimeRep to PrimRep]
    runtimeRepPrimRep :: HasDebugCallStack => SDoc -> Type -> [PrimRep]
    runtimeRepPrimRep :: HasDebugCallStack => SDoc -> Type -> [PrimRep]
    runtimeRepPrimRep SDoc
    doc Type
    rr_ty
      | Just Type
    rr_ty' <- Type -> Maybe Type
    coreView Type
    rr_ty
      = HasDebugCallStack => SDoc -> Type -> [PrimRep]
    SDoc -> Type -> [PrimRep]
    runtimeRepPrimRep SDoc
    doc Type
    rr_ty'
      | TyConApp TyCon
    rr_dc [Type]
    args <- Type
    rr_ty
      , RuntimeRep [Type] -> [PrimRep]
    fun <- TyCon -> RuntimeRepInfo
    tyConRuntimeRepInfo TyCon
    rr_dc
      = [Type] -> [PrimRep]
    fun [Type]
    args
      | Bool
    otherwise
      = String -> SDoc -> [PrimRep]
    forall a. HasCallStack => String -> SDoc -> a
    pprPanic String
    "runtimeRepPrimRep" (SDoc
    doc SDoc -> SDoc -> SDoc
    $$ Type -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr Type
    rr_ty)

    -- | Convert a PrimRep back to a Type. Used only in the unariser to give types
    -- to fresh Ids. Really, only the type's representation matters.
    -- See also Note [RuntimeRep and PrimRep]
    primRepToType :: PrimRep -> Type
    primRepToType :: PrimRep -> Type
    primRepToType = Type -> Type
    anyTypeOfKind (Type -> Type) -> (PrimRep -> Type) -> PrimRep -> Type
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . Type -> Type
    tYPE (Type -> Type) -> (PrimRep -> Type) -> PrimRep -> Type
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . PrimRep -> Type
    primRepToRuntimeRep