{-# 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.Utils.Outputable import GHC.Builtin.Names import GHC.Core.Coercion import GHC.Core.TyCon import GHC.Core.TyCo.Rep import GHC.Core.Type import GHC.Utils.Misc import GHC.Builtin.Types.Prim import {-# SOURCE #-} GHC.Builtin.Types ( anyTypeOfKind ) 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 ty | [_] <- typePrimRep ty = True | otherwise = False -- INVARIANT: the result list is never empty. typePrimRepArgs :: HasDebugCallStack => Type -> [PrimRep] typePrimRepArgs ty | [] <- reps = [VoidRep] | otherwise = reps where reps = typePrimRep 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 ty | Just (_, unwrapped) <- topNormaliseTypeX stepper mappend inner_ty = unwrapped | otherwise = inner_ty where inner_ty = go ty go t | Just t' <- coreView t = go t' go (ForAllTy _ t) = go t go (CastTy t _) = go t go t = t -- cf. Coercion.unwrapNewTypeStepper stepper rec_nts tc tys | Just (ty', _) <- instNewTyCon_maybe tc tys = case checkRecTc rec_nts tc of Just rec_nts' -> NS_Step rec_nts' (go ty') () Nothing -> NS_Abort -- infinite newtypes | otherwise = NS_Done countFunRepArgs :: Arity -> Type -> RepArity countFunRepArgs 0 _ = 0 countFunRepArgs n ty | FunTy _ _ arg res <- unwrapType ty = length (typePrimRepArgs arg) + countFunRepArgs (n - 1) res | otherwise = pprPanic "countFunRepArgs: arity greater than type can handle" (ppr (n, ty, typePrimRep ty)) countConRepArgs :: DataCon -> RepArity countConRepArgs dc = go (dataConRepArity dc) (dataConRepType dc) where go :: Arity -> Type -> RepArity go 0 _ = 0 go n ty | FunTy _ _ arg res <- unwrapType ty = length (typePrimRep arg) + go (n - 1) res | otherwise = pprPanic "countConRepArgs: arity greater than type can handle" (ppr (n, ty, typePrimRep ty)) -- | True if the type has zero width. isVoidTy :: Type -> Bool isVoidTy = null . 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 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. | constrs0 `lengthLessThan` 2 = [WordSlot] | otherwise = let combine_alts :: [SortedSlotTys] -- slots of constructors -> SortedSlotTys -- final slots combine_alts constrs = foldl' merge [] constrs merge :: SortedSlotTys -> SortedSlotTys -> SortedSlotTys merge existing_slots [] = existing_slots merge [] needed_slots = needed_slots merge (es : ess) (s : ss) | Just s' <- s `fitsIn` es = -- found a slot, use it s' : merge ess ss | s < es = -- we need a new slot and this is the right place for it s : merge (es : ess) ss | otherwise = -- keep searching for a slot es : merge ess (s : ss) -- Nesting unboxed tuples and sums is OK, so we need to flatten first. rep :: [PrimRep] -> SortedSlotTys rep ty = sort (map primRepSlot ty) sumRep = WordSlot : combine_alts (map rep constrs0) -- WordSlot: for the tag of the sum in 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 sum_slots0 arg_slots0 = go arg_slots0 IS.empty where go :: [SlotTy] -> IS.IntSet -> [Int] go [] _ = [] go (arg : args) used = let slot_idx = findSlot arg 0 sum_slots0 used in slot_idx : go args (IS.insert slot_idx used) findSlot :: SlotTy -> Int -> SortedSlotTys -> IS.IntSet -> Int findSlot arg slot_idx (slot : slots) useds | not (IS.member slot_idx useds) , Just slot == arg `fitsIn` slot = slot_idx | otherwise = findSlot arg (slot_idx + 1) slots useds findSlot _ _ [] _ = pprPanic "findSlot" (text "Can't find slot" $$ ppr sum_slots0 $$ ppr arg_slots0) -------------------------------------------------------------------------------- -- We have 3 kinds of slots: -- -- - Pointer slot: Only shared between actual pointers to Haskell heap (i.e. -- boxed objects) -- -- - 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 = PtrSlot | WordSlot | Word64Slot | FloatSlot | DoubleSlot deriving (Eq, 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 PtrSlot = text "PtrSlot" ppr Word64Slot = text "Word64Slot" ppr WordSlot = text "WordSlot" ppr DoubleSlot = text "DoubleSlot" ppr FloatSlot = text "FloatSlot" typeSlotTy :: UnaryType -> Maybe SlotTy typeSlotTy ty | isVoidTy ty = Nothing | otherwise = Just (primRepSlot (typePrimRep1 ty)) primRepSlot :: PrimRep -> SlotTy primRepSlot VoidRep = pprPanic "primRepSlot" (text "No slot for VoidRep") primRepSlot LiftedRep = PtrSlot primRepSlot UnliftedRep = PtrSlot primRepSlot IntRep = WordSlot primRepSlot Int8Rep = WordSlot primRepSlot Int16Rep = WordSlot primRepSlot Int32Rep = WordSlot primRepSlot Int64Rep = Word64Slot primRepSlot WordRep = WordSlot primRepSlot Word8Rep = WordSlot primRepSlot Word16Rep = WordSlot primRepSlot Word32Rep = WordSlot primRepSlot Word64Rep = Word64Slot primRepSlot AddrRep = WordSlot primRepSlot FloatRep = FloatSlot primRepSlot DoubleRep = DoubleSlot primRepSlot VecRep{} = pprPanic "primRepSlot" (text "No slot for VecRep") slotPrimRep :: SlotTy -> PrimRep slotPrimRep PtrSlot = LiftedRep -- choice between lifted & unlifted seems arbitrary slotPrimRep Word64Slot = Word64Rep slotPrimRep WordSlot = WordRep slotPrimRep DoubleSlot = DoubleRep slotPrimRep FloatSlot = FloatRep -- | Returns the bigger type if one fits into the other. (commutative) fitsIn :: SlotTy -> SlotTy -> Maybe SlotTy fitsIn ty1 ty2 | isWordSlot ty1 && isWordSlot ty2 = Just (max ty1 ty2) | isFloatSlot ty1 && isFloatSlot ty2 = Just (max ty1 ty2) | isPtrSlot ty1 && isPtrSlot ty2 = Just PtrSlot | otherwise = Nothing where isPtrSlot PtrSlot = True isPtrSlot _ = False isWordSlot Word64Slot = True isWordSlot WordSlot = True isWordSlot _ = False isFloatSlot DoubleSlot = True isFloatSlot FloatSlot = True isFloatSlot _ = 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 | LiftedRep -- ^ lifted; represented by a pointer | UnliftedRep -- ^ unlifted; represented by a pointer | IntRep -- ^ signed, word-sized value ...etc... 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. 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 ty = kindPrimRep (text "typePrimRep" <+> parens (ppr ty <+> dcolon <+> ppr (typeKind ty))) (typeKind 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 ty = case typePrimRep ty of [] -> VoidRep [rep] -> rep _ -> pprPanic "typePrimRep1" (ppr ty $$ ppr (typePrimRep ty)) -- | Find the runtime representation of a 'TyCon'. Defined here to -- avoid module loops. Returns a list of the register shapes necessary. -- See also Note [Getting from RuntimeRep to PrimRep] tyConPrimRep :: HasDebugCallStack => TyCon -> [PrimRep] tyConPrimRep tc = kindPrimRep (text "kindRep tc" <+> ppr tc $$ ppr res_kind) res_kind where res_kind = tyConResKind 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 tc = case tyConPrimRep tc of [] -> VoidRep [rep] -> rep _ -> pprPanic "tyConPrimRep1" (ppr tc $$ ppr (tyConPrimRep tc)) -- | Take a kind (of shape @TYPE rr@) and produce the 'PrimRep's -- of values of types of this kind. -- See also Note [Getting from RuntimeRep to PrimRep] kindPrimRep :: HasDebugCallStack => SDoc -> Kind -> [PrimRep] kindPrimRep doc ki | Just ki' <- coreView ki = kindPrimRep doc ki' kindPrimRep doc (TyConApp typ [runtime_rep]) = ASSERT( typ `hasKey` tYPETyConKey ) runtimeRepPrimRep doc runtime_rep kindPrimRep doc ki = pprPanic "kindPrimRep" (ppr ki $$ 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 doc rr_ty | Just rr_ty' <- coreView rr_ty = runtimeRepPrimRep doc rr_ty' | TyConApp rr_dc args <- rr_ty , RuntimeRep fun <- tyConRuntimeRepInfo rr_dc = fun args | otherwise = pprPanic "runtimeRepPrimRep" (doc $$ ppr 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 = anyTypeOfKind . tYPE . primRepToRuntimeRep