%
+% (c) The University of Glasgow 2006
% (c) The AQUA Project, Glasgow University, 1998
%
-\section[StdIdInfo]{Standard unfoldings}
This module contains definitions for the IdInfo for things that
have a standard form, namely:
- * data constructors
- * record selectors
- * method and superclass selectors
- * primitive operations
+- data constructors
+- record selectors
+- method and superclass selectors
+- primitive operations
\begin{code}
module MkId (
- mkDictFunId, mkDefaultMethodId,
- mkDictSelId,
+ mkDictFunId, mkDefaultMethodId,
+ mkDictSelId,
- mkDataConIds,
- mkRecordSelId,
- mkPrimOpId, mkFCallId,
+ mkDataConIds,
+ mkPrimOpId, mkFCallId, mkTickBoxOpId, mkBreakPointOpId,
- mkReboxingAlt, wrapNewTypeBody, unwrapNewTypeBody,
+ mkReboxingAlt, wrapNewTypeBody, unwrapNewTypeBody,
+ wrapFamInstBody, unwrapFamInstScrut,
mkUnpackCase, mkProductBox,
- -- And some particular Ids; see below for why they are wired in
- wiredInIds, ghcPrimIds,
- unsafeCoerceId, realWorldPrimId, voidArgId, nullAddrId, seqId,
- lazyId, lazyIdUnfolding, lazyIdKey,
-
- mkRuntimeErrorApp,
- rEC_CON_ERROR_ID, iRREFUT_PAT_ERROR_ID, rUNTIME_ERROR_ID,
- nON_EXHAUSTIVE_GUARDS_ERROR_ID, nO_METHOD_BINDING_ERROR_ID,
- pAT_ERROR_ID, eRROR_ID,
-
- unsafeCoerceName
+ -- And some particular Ids; see below for why they are wired in
+ wiredInIds, ghcPrimIds,
+ unsafeCoerceName, unsafeCoerceId, realWorldPrimId,
+ voidArgId, nullAddrId, seqId, lazyId, lazyIdKey
) where
#include "HsVersions.h"
-
-import BasicTypes ( Arity, StrictnessMark(..), isMarkedUnboxed, isMarkedStrict )
-import Rules ( mkSpecInfo )
-import TysPrim ( openAlphaTyVars, alphaTyVar, alphaTy,
- realWorldStatePrimTy, addrPrimTy
- )
-import TysWiredIn ( charTy, mkListTy )
-import PrelRules ( primOpRules )
-import Type ( TyThing(..), mkForAllTy, tyVarsOfTypes,
- newTyConInstRhs, mkTopTvSubst, substTyVar,
- substTys, zipTopTvSubst )
-import TcGadt ( gadtRefine, refineType, emptyRefinement )
-import HsBinds ( HsWrapper(..), isIdHsWrapper )
-import Coercion ( mkSymCoercion, mkUnsafeCoercion, isEqPred )
-import TcType ( Type, ThetaType, mkDictTy, mkPredTys, mkPredTy,
- mkTyConApp, mkTyVarTys, mkClassPred, isPredTy,
- mkFunTys, mkFunTy, mkSigmaTy, tcSplitSigmaTy, tcEqType,
- isUnLiftedType, mkForAllTys, mkTyVarTy, tyVarsOfType,
- tcSplitFunTys, tcSplitForAllTys, dataConsStupidTheta
- )
-import CoreUtils ( exprType, dataConOrigInstPat, mkCoerce )
-import CoreUnfold ( mkTopUnfolding, mkCompulsoryUnfolding )
-import Literal ( nullAddrLit, mkStringLit )
-import TyCon ( TyCon, isNewTyCon, tyConTyVars, tyConDataCons,
- FieldLabel,
- tyConStupidTheta, isProductTyCon, isDataTyCon,
- isRecursiveTyCon, isFamInstTyCon,
- tyConFamInst_maybe, tyConFamilyCoercion_maybe,
- newTyConCo_maybe )
-import Class ( Class, classTyCon, classSelIds )
-import Var ( Id, TyVar, Var, setIdType )
-import VarSet ( isEmptyVarSet, subVarSet, varSetElems )
-import Name ( mkFCallName, mkWiredInName, Name, BuiltInSyntax(..))
-import OccName ( mkOccNameFS, varName )
-import PrimOp ( PrimOp, primOpSig, primOpOcc, primOpTag )
-import ForeignCall ( ForeignCall )
-import DataCon ( DataCon, DataConIds(..), dataConTyCon,
- dataConUnivTyVars,
- dataConFieldLabels, dataConRepArity, dataConResTys,
- dataConRepArgTys, dataConRepType, dataConFullSig,
- dataConStrictMarks, dataConExStricts,
- splitProductType, isVanillaDataCon, dataConFieldType,
- deepSplitProductType,
- )
-import Id ( idType, mkGlobalId, mkVanillaGlobal, mkSysLocal,
- mkTemplateLocals, mkTemplateLocalsNum, mkExportedLocalId,
- mkTemplateLocal, idName
- )
-import IdInfo ( IdInfo, noCafIdInfo, setUnfoldingInfo,
- setArityInfo, setSpecInfo, setCafInfo,
- setAllStrictnessInfo, vanillaIdInfo,
- GlobalIdDetails(..), CafInfo(..)
- )
-import NewDemand ( mkStrictSig, DmdResult(..),
- mkTopDmdType, topDmd, evalDmd, lazyDmd, retCPR,
- Demand(..), Demands(..) )
-import DmdAnal ( dmdAnalTopRhs )
+import Rules
+import TysPrim
+import PrelRules
+import Type
+import Coercion
+import TcType
+import MkCore
+import CoreUtils ( exprType, mkCoerce )
+import CoreUnfold
+import Literal
+import TyCon
+import Class
+import VarSet
+import Name
+import PrimOp
+import ForeignCall
+import DataCon
+import Id
+import Var ( Var, TyVar, mkCoVar, mkExportedLocalVar )
+import IdInfo
+import Demand
import CoreSyn
-import Unique ( mkBuiltinUnique, mkPrimOpIdUnique )
-import Maybes
+import Unique
import PrelNames
-import Util ( dropList, isSingleton )
+import BasicTypes hiding ( SuccessFlag(..) )
+import Util
import Outputable
import FastString
-import ListSetOps ( assoc, minusList )
-\end{code}
+import ListSetOps
+import Module
+\end{code}
%************************************************************************
-%* *
+%* *
\subsection{Wired in Ids}
-%* *
+%* *
%************************************************************************
+Note [Wired-in Ids]
+~~~~~~~~~~~~~~~~~~~
+There are several reasons why an Id might appear in the wiredInIds:
+
+(1) The ghcPrimIds are wired in because they can't be defined in
+ Haskell at all, although the can be defined in Core. They have
+ compulsory unfoldings, so they are always inlined and they have
+ no definition site. Their home module is GHC.Prim, so they
+ also have a description in primops.txt.pp, where they are called
+ 'pseudoops'.
+
+(2) The 'error' function, eRROR_ID, is wired in because we don't yet have
+ a way to express in an interface file that the result type variable
+ is 'open'; that is can be unified with an unboxed type
+
+ [The interface file format now carry such information, but there's
+ no way yet of expressing at the definition site for these
+ error-reporting functions that they have an 'open'
+ result type. -- sof 1/99]
+
+(3) Other error functions (rUNTIME_ERROR_ID) are wired in (a) because
+ the desugarer generates code that mentiones them directly, and
+ (b) for the same reason as eRROR_ID
+
+(4) lazyId is wired in because the wired-in version overrides the
+ strictness of the version defined in GHC.Base
+
+In cases (2-4), the function has a definition in a library module, and
+can be called; but the wired-in version means that the details are
+never read from that module's interface file; instead, the full definition
+is right here.
+
\begin{code}
+wiredInIds :: [Id]
wiredInIds
- = [ -- These error-y things are wired in because we don't yet have
- -- a way to express in an interface file that the result type variable
- -- is 'open'; that is can be unified with an unboxed type
- --
- -- [The interface file format now carry such information, but there's
- -- no way yet of expressing at the definition site for these
- -- error-reporting functions that they have an 'open'
- -- result type. -- sof 1/99]
-
- eRROR_ID, -- This one isn't used anywhere else in the compiler
- -- But we still need it in wiredInIds so that when GHC
- -- compiles a program that mentions 'error' we don't
- -- import its type from the interface file; we just get
- -- the Id defined here. Which has an 'open-tyvar' type.
-
- rUNTIME_ERROR_ID,
- iRREFUT_PAT_ERROR_ID,
- nON_EXHAUSTIVE_GUARDS_ERROR_ID,
- nO_METHOD_BINDING_ERROR_ID,
- pAT_ERROR_ID,
- rEC_CON_ERROR_ID,
-
- lazyId
- ] ++ ghcPrimIds
+ = [lazyId]
+ ++ errorIds -- Defined in MkCore
+ ++ ghcPrimIds
-- These Ids are exported from GHC.Prim
+ghcPrimIds :: [Id]
ghcPrimIds
- = [ -- These can't be defined in Haskell, but they have
- -- perfectly reasonable unfoldings in Core
+ = [ -- These can't be defined in Haskell, but they have
+ -- perfectly reasonable unfoldings in Core
realWorldPrimId,
unsafeCoerceId,
nullAddrId,
\end{code}
%************************************************************************
-%* *
+%* *
\subsection{Data constructors}
-%* *
+%* *
%************************************************************************
The wrapper for a constructor is an ordinary top-level binding that evaluates
We're going to build a constructor that looks like:
- data (Data a, C b) => T a b = T1 !a !Int b
+ data (Data a, C b) => T a b = T1 !a !Int b
- T1 = /\ a b ->
- \d1::Data a, d2::C b ->
- \p q r -> case p of { p ->
- case q of { q ->
- Con T1 [a,b] [p,q,r]}}
+ T1 = /\ a b ->
+ \d1::Data a, d2::C b ->
+ \p q r -> case p of { p ->
+ case q of { q ->
+ Con T1 [a,b] [p,q,r]}}
Notice that
Making an explicit case expression allows the simplifier to eliminate
it in the (common) case where the constructor arg is already evaluated.
-[Wrappers for data instance tycons]
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Note [Wrappers for data instance tycons]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In the case of data instances, the wrapper also applies the coercion turning
the representation type into the family instance type to cast the result of
the wrapper. For example, consider the declarations
data family Map k :: * -> *
data instance Map (a, b) v = MapPair (Map a (Pair b v))
-The tycon to which the datacon MapPair belongs gets a unique internal name of
-the form :R123Map, and we call it the representation tycon. In contrast, Map
-is the family tycon (accessible via tyConFamInst_maybe). The wrapper and work
-of MapPair get the types
+The tycon to which the datacon MapPair belongs gets a unique internal
+name of the form :R123Map, and we call it the representation tycon.
+In contrast, Map is the family tycon (accessible via
+tyConFamInst_maybe). A coercion allows you to move between
+representation and family type. It is accessible from :R123Map via
+tyConFamilyCoercion_maybe and has kind
- $WMapPair :: forall a b v. Map a (Map a b v) -> Map (a, b) v
- $wMapPair :: forall a b v. Map a (Map a b v) -> :R123Map a b v
+ Co123Map a b v :: {Map (a, b) v ~ :R123Map a b v}
-which implies that the wrapper code will have to apply the coercion moving
-between representation and family type. It is accessible via
-tyConFamilyCoercion_maybe and has kind
+The wrapper and worker of MapPair get the types
+
+ -- Wrapper
+ $WMapPair :: forall a b v. Map a (Map a b v) -> Map (a, b) v
+ $WMapPair a b v = MapPair a b v `cast` sym (Co123Map a b v)
- Co123Map a b v :: {Map (a, b) v :=: :R123Map a b v}
+ -- Worker
+ MapPair :: forall a b v. Map a (Map a b v) -> :R123Map a b v
This coercion is conditionally applied by wrapFamInstBody.
+It's a bit more complicated if the data instance is a GADT as well!
+
+ data instance T [a] where
+ T1 :: forall b. b -> T [Maybe b]
+
+Hence we translate to
+
+ -- Wrapper
+ $WT1 :: forall b. b -> T [Maybe b]
+ $WT1 b v = T1 (Maybe b) b (Maybe b) v
+ `cast` sym (Co7T (Maybe b))
+
+ -- Worker
+ T1 :: forall c b. (c ~ Maybe b) => b -> :R7T c
+
+ -- Coercion from family type to representation type
+ Co7T a :: T [a] ~ :R7T a
+
\begin{code}
mkDataConIds :: Name -> Name -> DataCon -> DataConIds
mkDataConIds wrap_name wkr_name data_con
- | isNewTyCon tycon
- = DCIds Nothing nt_work_id -- Newtype, only has a worker
+ | isNewTyCon tycon -- Newtype, only has a worker
+ = DCIds Nothing nt_work_id
- | any isMarkedStrict all_strict_marks -- Algebraic, needs wrapper
- || not (null eq_spec) -- NB: LoadIface.ifaceDeclSubBndrs
- || isFamInstTyCon tycon -- depends on this test
+ | any isBanged all_strict_marks -- Algebraic, needs wrapper
+ || not (null eq_spec) -- NB: LoadIface.ifaceDeclSubBndrs
+ || isFamInstTyCon tycon -- depends on this test
= DCIds (Just alg_wrap_id) wrk_id
- | otherwise -- Algebraic, no wrapper
+ | otherwise -- Algebraic, no wrapper
= DCIds Nothing wrk_id
where
(univ_tvs, ex_tvs, eq_spec,
- theta, orig_arg_tys) = dataConFullSig data_con
- tycon = dataConTyCon data_con
-
- ----------- Wrapper --------------
- -- We used to include the stupid theta in the wrapper's args
- -- but now we don't. Instead the type checker just injects these
- -- extra constraints where necessary.
- wrap_tvs = (univ_tvs `minusList` map fst eq_spec) ++ ex_tvs
- subst = mkTopTvSubst eq_spec
- famSubst = ASSERT( length (tyConTyVars tycon ) ==
- length (mkTyVarTys univ_tvs) )
- zipTopTvSubst (tyConTyVars tycon) (mkTyVarTys univ_tvs)
- -- substitution mapping the type constructor's type
- -- arguments to the universals of the data constructor
- -- (crucial when type checking interfaces)
- dict_tys = mkPredTys theta
- result_ty_args = map (substTyVar subst) univ_tvs
- result_ty = case tyConFamInst_maybe tycon of
- -- ordinary constructor
- Nothing -> mkTyConApp tycon result_ty_args
- -- family instance constructor
- Just (familyTyCon,
- instTys) ->
- mkTyConApp familyTyCon ( substTys subst
- . substTys famSubst
- $ instTys)
- wrap_ty = mkForAllTys wrap_tvs $ mkFunTys dict_tys $
- mkFunTys orig_arg_tys $ result_ty
- -- NB: watch out here if you allow user-written equality
- -- constraints in data constructor signatures
-
- ----------- Worker (algebraic data types only) --------------
- -- The *worker* for the data constructor is the function that
- -- takes the representation arguments and builds the constructor.
+ eq_theta, dict_theta, orig_arg_tys, res_ty) = dataConFullSig data_con
+ tycon = dataConTyCon data_con -- The representation TyCon (not family)
+
+ ----------- Worker (algebraic data types only) --------------
+ -- The *worker* for the data constructor is the function that
+ -- takes the representation arguments and builds the constructor.
wrk_id = mkGlobalId (DataConWorkId data_con) wkr_name
- (dataConRepType data_con) wkr_info
+ (dataConRepType data_con) wkr_info
wkr_arity = dataConRepArity data_con
wkr_info = noCafIdInfo
- `setArityInfo` wkr_arity
- `setAllStrictnessInfo` Just wkr_sig
- `setUnfoldingInfo` evaldUnfolding -- Record that it's evaluated,
- -- even if arity = 0
+ `setArityInfo` wkr_arity
+ `setStrictnessInfo` Just wkr_sig
+ `setUnfoldingInfo` evaldUnfolding -- Record that it's evaluated,
+ -- even if arity = 0
wkr_sig = mkStrictSig (mkTopDmdType (replicate wkr_arity topDmd) cpr_info)
- -- Notice that we do *not* say the worker is strict
- -- even if the data constructor is declared strict
- -- e.g. data T = MkT !(Int,Int)
- -- Why? Because the *wrapper* is strict (and its unfolding has case
- -- expresssions that do the evals) but the *worker* itself is not.
- -- If we pretend it is strict then when we see
- -- case x of y -> $wMkT y
- -- the simplifier thinks that y is "sure to be evaluated" (because
- -- $wMkT is strict) and drops the case. No, $wMkT is not strict.
- --
- -- When the simplifer sees a pattern
- -- case e of MkT x -> ...
- -- it uses the dataConRepStrictness of MkT to mark x as evaluated;
- -- but that's fine... dataConRepStrictness comes from the data con
- -- not from the worker Id.
+ -- Note [Data-con worker strictness]
+ -- Notice that we do *not* say the worker is strict
+ -- even if the data constructor is declared strict
+ -- e.g. data T = MkT !(Int,Int)
+ -- Why? Because the *wrapper* is strict (and its unfolding has case
+ -- expresssions that do the evals) but the *worker* itself is not.
+ -- If we pretend it is strict then when we see
+ -- case x of y -> $wMkT y
+ -- the simplifier thinks that y is "sure to be evaluated" (because
+ -- $wMkT is strict) and drops the case. No, $wMkT is not strict.
+ --
+ -- When the simplifer sees a pattern
+ -- case e of MkT x -> ...
+ -- it uses the dataConRepStrictness of MkT to mark x as evaluated;
+ -- but that's fine... dataConRepStrictness comes from the data con
+ -- not from the worker Id.
cpr_info | isProductTyCon tycon &&
- isDataTyCon tycon &&
- wkr_arity > 0 &&
- wkr_arity <= mAX_CPR_SIZE = retCPR
- | otherwise = TopRes
- -- RetCPR is only true for products that are real data types;
- -- that is, not unboxed tuples or [non-recursive] newtypes
-
- ----------- Workers for newtypes --------------
+ isDataTyCon tycon &&
+ wkr_arity > 0 &&
+ wkr_arity <= mAX_CPR_SIZE = retCPR
+ | otherwise = TopRes
+ -- RetCPR is only true for products that are real data types;
+ -- that is, not unboxed tuples or [non-recursive] newtypes
+
+ ----------- Workers for newtypes --------------
nt_work_id = mkGlobalId (DataConWrapId data_con) wkr_name wrap_ty nt_work_info
- nt_work_info = noCafIdInfo -- The NoCaf-ness is set by noCafIdInfo
- `setArityInfo` 1 -- Arity 1
- `setUnfoldingInfo` newtype_unf
- newtype_unf = ASSERT( isVanillaDataCon data_con &&
- isSingleton orig_arg_tys )
- -- No existentials on a newtype, but it can have a context
- -- e.g. newtype Eq a => T a = MkT (...)
- mkCompulsoryUnfolding $
- mkLams wrap_tvs $ Lam id_arg1 $
- wrapNewTypeBody tycon result_ty_args
- (Var id_arg1)
-
- id_arg1 = mkTemplateLocal 1 (head orig_arg_tys)
-
- ----------- Wrappers for algebraic data types --------------
+ nt_work_info = noCafIdInfo -- The NoCaf-ness is set by noCafIdInfo
+ `setArityInfo` 1 -- Arity 1
+ `setUnfoldingInfo` newtype_unf
+ id_arg1 = mkTemplateLocal 1 (head orig_arg_tys)
+ newtype_unf = ASSERT2( isVanillaDataCon data_con &&
+ isSingleton orig_arg_tys, ppr data_con )
+ -- Note [Newtype datacons]
+ mkCompulsoryUnfolding $
+ mkLams wrap_tvs $ Lam id_arg1 $
+ wrapNewTypeBody tycon res_ty_args (Var id_arg1)
+
+
+ ----------- Wrapper --------------
+ -- We used to include the stupid theta in the wrapper's args
+ -- but now we don't. Instead the type checker just injects these
+ -- extra constraints where necessary.
+ wrap_tvs = (univ_tvs `minusList` map fst eq_spec) ++ ex_tvs
+ res_ty_args = substTyVars (mkTopTvSubst eq_spec) univ_tvs
+ eq_tys = mkPredTys eq_theta
+ dict_tys = mkPredTys dict_theta
+ wrap_ty = mkForAllTys wrap_tvs $ mkFunTys eq_tys $ mkFunTys dict_tys $
+ mkFunTys orig_arg_tys $ res_ty
+ -- NB: watch out here if you allow user-written equality
+ -- constraints in data constructor signatures
+
+ ----------- Wrappers for algebraic data types --------------
alg_wrap_id = mkGlobalId (DataConWrapId data_con) wrap_name wrap_ty alg_wrap_info
- alg_wrap_info = noCafIdInfo -- The NoCaf-ness is set by noCafIdInfo
- `setArityInfo` alg_arity
- -- It's important to specify the arity, so that partial
- -- applications are treated as values
- `setUnfoldingInfo` alg_unf
- `setAllStrictnessInfo` Just wrap_sig
+ alg_wrap_info = noCafIdInfo -- The NoCaf-ness is set by noCafIdInfo
+ `setArityInfo` wrap_arity
+ -- It's important to specify the arity, so that partial
+ -- applications are treated as values
+ `setUnfoldingInfo` wrap_unf
+ `setStrictnessInfo` Just wrap_sig
all_strict_marks = dataConExStricts data_con ++ dataConStrictMarks data_con
wrap_sig = mkStrictSig (mkTopDmdType arg_dmds cpr_info)
arg_dmds = map mk_dmd all_strict_marks
- mk_dmd str | isMarkedStrict str = evalDmd
- | otherwise = lazyDmd
- -- The Cpr info can be important inside INLINE rhss, where the
- -- wrapper constructor isn't inlined.
- -- And the argument strictness can be important too; we
- -- may not inline a contructor when it is partially applied.
- -- For example:
- -- data W = C !Int !Int !Int
- -- ...(let w = C x in ...(w p q)...)...
- -- we want to see that w is strict in its two arguments
-
- alg_unf = mkTopUnfolding $ Note InlineMe $
- mkLams wrap_tvs $
- mkLams dict_args $ mkLams id_args $
- foldr mk_case con_app
- (zip (dict_args ++ id_args) all_strict_marks)
- i3 []
-
- con_app _ rep_ids = wrapFamInstBody tycon result_ty_args $
- Var wrk_id `mkTyApps` result_ty_args
- `mkVarApps` ex_tvs
- `mkTyApps` map snd eq_spec
- `mkVarApps` reverse rep_ids
+ mk_dmd str | isBanged str = evalDmd
+ | otherwise = lazyDmd
+ -- The Cpr info can be important inside INLINE rhss, where the
+ -- wrapper constructor isn't inlined.
+ -- And the argument strictness can be important too; we
+ -- may not inline a contructor when it is partially applied.
+ -- For example:
+ -- data W = C !Int !Int !Int
+ -- ...(let w = C x in ...(w p q)...)...
+ -- we want to see that w is strict in its two arguments
+
+ wrap_unf = mkInlineRule wrap_rhs (Just (length dict_args + length id_args))
+ wrap_rhs = mkLams wrap_tvs $
+ mkLams eq_args $
+ mkLams dict_args $ mkLams id_args $
+ foldr mk_case con_app
+ (zip (dict_args ++ id_args) all_strict_marks)
+ i3 []
+
+ con_app _ rep_ids = wrapFamInstBody tycon res_ty_args $
+ Var wrk_id `mkTyApps` res_ty_args
+ `mkVarApps` ex_tvs
+ -- Equality evidence:
+ `mkTyApps` map snd eq_spec
+ `mkVarApps` eq_args
+ `mkVarApps` reverse rep_ids
(dict_args,i2) = mkLocals 1 dict_tys
(id_args,i3) = mkLocals i2 orig_arg_tys
- alg_arity = i3-1
+ wrap_arity = i3-1
+ (eq_args,_) = mkCoVarLocals i3 eq_tys
+
+ mkCoVarLocals i [] = ([],i)
+ mkCoVarLocals i (x:xs) = let (ys,j) = mkCoVarLocals (i+1) xs
+ y = mkCoVar (mkSysTvName (mkBuiltinUnique i)
+ (fsLit "dc_co")) x
+ in (y:ys,j)
mk_case
- :: (Id, StrictnessMark) -- Arg, strictness
- -> (Int -> [Id] -> CoreExpr) -- Body
- -> Int -- Next rep arg id
- -> [Id] -- Rep args so far, reversed
- -> CoreExpr
+ :: (Id, HsBang) -- Arg, strictness
+ -> (Int -> [Id] -> CoreExpr) -- Body
+ -> Int -- Next rep arg id
+ -> [Id] -- Rep args so far, reversed
+ -> CoreExpr
mk_case (arg,strict) body i rep_args
- = case strict of
- NotMarkedStrict -> body i (arg:rep_args)
- MarkedStrict
- | isUnLiftedType (idType arg) -> body i (arg:rep_args)
- | otherwise ->
- Case (Var arg) arg result_ty [(DEFAULT,[], body i (arg:rep_args))]
-
- MarkedUnboxed
- -> unboxProduct i (Var arg) (idType arg) the_body
+ = case strict of
+ HsNoBang -> body i (arg:rep_args)
+ HsUnpack -> unboxProduct i (Var arg) (idType arg) the_body
where
the_body i con_args = body i (reverse con_args ++ rep_args)
+ _other -- HsUnpackFailed and HsStrict
+ | isUnLiftedType (idType arg) -> body i (arg:rep_args)
+ | otherwise -> Case (Var arg) arg res_ty
+ [(DEFAULT,[], body i (arg:rep_args))]
mAX_CPR_SIZE :: Arity
mAX_CPR_SIZE = 10
-- We do not treat very big tuples as CPR-ish:
--- a) for a start we get into trouble because there aren't
--- "enough" unboxed tuple types (a tiresome restriction,
--- but hard to fix),
--- b) more importantly, big unboxed tuples get returned mainly
--- on the stack, and are often then allocated in the heap
--- by the caller. So doing CPR for them may in fact make
--- things worse.
-
+-- a) for a start we get into trouble because there aren't
+-- "enough" unboxed tuple types (a tiresome restriction,
+-- but hard to fix),
+-- b) more importantly, big unboxed tuples get returned mainly
+-- on the stack, and are often then allocated in the heap
+-- by the caller. So doing CPR for them may in fact make
+-- things worse.
+
+mkLocals :: Int -> [Type] -> ([Id], Int)
mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
- where
- n = length tys
-
--- If the type constructor is a representation type of a data instance, wrap
--- the expression into a cast adjusting the expression type, which is an
--- instance of the representation type, to the corresponding instance of the
--- family instance type.
---
-wrapFamInstBody :: TyCon -> [Type] -> CoreExpr -> CoreExpr
-wrapFamInstBody tycon args result_expr
- | Just co_con <- tyConFamilyCoercion_maybe tycon
- = mkCoerce (mkSymCoercion (mkTyConApp co_con args)) result_expr
- | otherwise
- = result_expr
+ where
+ n = length tys
\end{code}
+Note [Newtype datacons]
+~~~~~~~~~~~~~~~~~~~~~~~
+The "data constructor" for a newtype should always be vanilla. At one
+point this wasn't true, because the newtype arising from
+ class C a => D a
+looked like
+ newtype T:D a = D:D (C a)
+so the data constructor for T:C had a single argument, namely the
+predicate (C a). But now we treat that as an ordinary argument, not
+part of the theta-type, so all is well.
+
%************************************************************************
-%* *
-\subsection{Record selectors}
-%* *
+%* *
+\subsection{Dictionary selectors}
+%* *
%************************************************************************
-We're going to build a record selector unfolding that looks like this:
-
- data T a b c = T1 { ..., op :: a, ...}
- | T2 { ..., op :: a, ...}
- | T3
-
- sel = /\ a b c -> \ d -> case d of
- T1 ... x ... -> x
- T2 ... x ... -> x
- other -> error "..."
-
-Similarly for newtypes
-
- newtype N a = MkN { unN :: a->a }
-
- unN :: N a -> a -> a
- unN n = coerce (a->a) n
-
-We need to take a little care if the field has a polymorphic type:
-
- data R = R { f :: forall a. a->a }
-
-Then we want
-
- f :: forall a. R -> a -> a
- f = /\ a \ r = case r of
- R f -> f a
-
-(not f :: R -> forall a. a->a, which gives the type inference mechanism
-problems at call sites)
-
-Similarly for (recursive) newtypes
-
- newtype N = MkN { unN :: forall a. a->a }
+Selecting a field for a dictionary. If there is just one field, then
+there's nothing to do.
- unN :: forall b. N -> b -> b
- unN = /\b -> \n:N -> (coerce (forall a. a->a) n)
+Dictionary selectors may get nested forall-types. Thus:
+ class Foo a where
+ op :: forall b. Ord b => a -> b -> b
-Note [Naughty record selectors]
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-A "naughty" field is one for which we can't define a record
-selector, because an existential type variable would escape. For example:
- data T = forall a. MkT { x,y::a }
-We obviously can't define
- x (MkT v _) = v
-Nevertheless we *do* put a RecordSelId into the type environment
-so that if the user tries to use 'x' as a selector we can bleat
-helpfully, rather than saying unhelpfully that 'x' is not in scope.
-Hence the sel_naughty flag, to identify record selectors that don't really exist.
+Then the top-level type for op is
-In general, a field is naughty if its type mentions a type variable that
-isn't in the result type of the constructor.
+ op :: forall a. Foo a =>
+ forall b. Ord b =>
+ a -> b -> b
-Note [GADT record selectors]
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-For GADTs, we require that all constructors with a common field 'f' have the same
-result type (modulo alpha conversion). [Checked in TcTyClsDecls.checkValidTyCon]
-E.g.
- data T where
- T1 { f :: a } :: T [a]
- T2 { f :: a, y :: b } :: T [a]
-and now the selector takes that type as its argument:
- f :: forall a. T [a] -> a
- f t = case t of
- T1 { f = v } -> v
- T2 { f = v } -> v
-Note the forall'd tyvars of the selector are just the free tyvars
-of the result type; there may be other tyvars in the constructor's
-type (e.g. 'b' in T2).
+This is unlike ordinary record selectors, which have all the for-alls
+at the outside. When dealing with classes it's very convenient to
+recover the original type signature from the class op selector.
\begin{code}
-
--- Steps for handling "naughty" vs "non-naughty" selectors:
--- 1. Determine naughtiness by comparing field type vs result type
--- 2. Install naughty ones with selector_ty of type _|_ and fill in mzero for info
--- 3. If it's not naughty, do the normal plan.
-
-mkRecordSelId :: TyCon -> FieldLabel -> Id
-mkRecordSelId tycon field_label
- -- Assumes that all fields with the same field label have the same type
- | is_naughty = naughty_id
- | otherwise = sel_id
+mkDictSelId :: Bool -- True <=> don't include the unfolding
+ -- Little point on imports without -O, because the
+ -- dictionary itself won't be visible
+ -> Name -- Name of one of the *value* selectors
+ -- (dictionary superclass or method)
+ -> Class -> Id
+mkDictSelId no_unf name clas
+ = mkGlobalId (ClassOpId clas) name sel_ty info
where
- is_naughty = not (tyVarsOfType field_ty `subVarSet` res_tv_set)
- sel_id_details = RecordSelId tycon field_label is_naughty
-
- -- Escapist case here for naughty construcotrs
- -- We give it no IdInfo, and a type of forall a.a (never looked at)
- naughty_id = mkGlobalId sel_id_details field_label forall_a_a noCafIdInfo
- forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar)
-
- -- Normal case starts here
- sel_id = mkGlobalId sel_id_details field_label selector_ty info
- data_cons = tyConDataCons tycon
- data_cons_w_field = filter has_field data_cons -- Can't be empty!
- has_field con = field_label `elem` dataConFieldLabels con
-
- con1 = head data_cons_w_field
- res_tys = dataConResTys con1
- res_tv_set = tyVarsOfTypes res_tys
- res_tvs = varSetElems res_tv_set
- data_ty = mkTyConApp tycon res_tys
- field_ty = dataConFieldType con1 field_label
-
- -- *Very* tiresomely, the selectors are (unnecessarily!) overloaded over
- -- just the dictionaries in the types of the constructors that contain
- -- the relevant field. [The Report says that pattern matching on a
- -- constructor gives the same constraints as applying it.] Urgh.
- --
- -- However, not all data cons have all constraints (because of
- -- BuildTyCl.mkDataConStupidTheta). So we need to find all the data cons
- -- involved in the pattern match and take the union of their constraints.
- stupid_dict_tys = mkPredTys (dataConsStupidTheta data_cons_w_field)
- n_stupid_dicts = length stupid_dict_tys
-
- (field_tyvars,pre_field_theta,field_tau) = tcSplitSigmaTy field_ty
-
- field_theta = filter (not . isEqPred) pre_field_theta
- field_dict_tys = mkPredTys field_theta
- n_field_dict_tys = length field_dict_tys
- -- If the field has a universally quantified type we have to
- -- be a bit careful. Suppose we have
- -- data R = R { op :: forall a. Foo a => a -> a }
- -- Then we can't give op the type
- -- op :: R -> forall a. Foo a => a -> a
- -- because the typechecker doesn't understand foralls to the
- -- right of an arrow. The "right" type to give it is
- -- op :: forall a. Foo a => R -> a -> a
- -- But then we must generate the right unfolding too:
- -- op = /\a -> \dfoo -> \ r ->
- -- case r of
- -- R op -> op a dfoo
- -- Note that this is exactly the type we'd infer from a user defn
- -- op (R op) = op
-
- selector_ty :: Type
- selector_ty = mkForAllTys res_tvs $ mkForAllTys field_tyvars $
- mkFunTys stupid_dict_tys $ mkFunTys field_dict_tys $
- mkFunTy data_ty field_tau
-
- arity = 1 + n_stupid_dicts + n_field_dict_tys
-
- (strict_sig, rhs_w_str) = dmdAnalTopRhs sel_rhs
- -- Use the demand analyser to work out strictness.
- -- With all this unpackery it's not easy!
+ sel_ty = mkForAllTys tyvars (mkFunTy (idType dict_id) (idType the_arg_id))
+ -- We can't just say (exprType rhs), because that would give a type
+ -- C a -> C a
+ -- for a single-op class (after all, the selector is the identity)
+ -- But it's type must expose the representation of the dictionary
+ -- to get (say) C a -> (a -> a)
+
+ base_info = noCafIdInfo
+ `setArityInfo` 1
+ `setStrictnessInfo` Just strict_sig
+ `setUnfoldingInfo` (if no_unf then noUnfolding
+ else mkImplicitUnfolding rhs)
+ -- In module where class op is defined, we must add
+ -- the unfolding, even though it'll never be inlined
+ -- becuase we use that to generate a top-level binding
+ -- for the ClassOp
+
+ info = base_info `setSpecInfo` mkSpecInfo [rule]
+ `setInlinePragInfo` neverInlinePragma
+ -- Add a magic BuiltinRule, and never inline it
+ -- so that the rule is always available to fire.
+ -- See Note [ClassOp/DFun selection] in TcInstDcls
+
+ n_ty_args = length tyvars
+
+ -- This is the built-in rule that goes
+ -- op (dfT d1 d2) ---> opT d1 d2
+ rule = BuiltinRule { ru_name = fsLit "Class op " `appendFS`
+ occNameFS (getOccName name)
+ , ru_fn = name
+ , ru_nargs = n_ty_args + 1
+ , ru_try = dictSelRule val_index n_ty_args n_eq_args }
+
+ -- The strictness signature is of the form U(AAAVAAAA) -> T
+ -- where the V depends on which item we are selecting
+ -- It's worth giving one, so that absence info etc is generated
+ -- even if the selector isn't inlined
+ strict_sig = mkStrictSig (mkTopDmdType [arg_dmd] TopRes)
+ arg_dmd | new_tycon = evalDmd
+ | otherwise = Eval (Prod [ if the_arg_id == id then evalDmd else Abs
+ | id <- arg_ids ])
+
+ tycon = classTyCon clas
+ new_tycon = isNewTyCon tycon
+ [data_con] = tyConDataCons tycon
+ tyvars = dataConUnivTyVars data_con
+ arg_tys = dataConRepArgTys data_con -- Includes the dictionary superclasses
+ eq_theta = dataConEqTheta data_con
+ n_eq_args = length eq_theta
+
+ -- 'index' is a 0-index into the *value* arguments of the dictionary
+ val_index = assoc "MkId.mkDictSelId" sel_index_prs name
+ sel_index_prs = map idName (classAllSelIds clas) `zip` [0..]
+
+ the_arg_id = arg_ids !! val_index
+ pred = mkClassPred clas (mkTyVarTys tyvars)
+ dict_id = mkTemplateLocal 1 $ mkPredTy pred
+ arg_ids = mkTemplateLocalsNum 2 arg_tys
+ eq_ids = map mkWildEvBinder eq_theta
+
+ rhs = mkLams tyvars (Lam dict_id rhs_body)
+ rhs_body | new_tycon = unwrapNewTypeBody tycon (map mkTyVarTy tyvars) (Var dict_id)
+ | otherwise = Case (Var dict_id) dict_id (idType the_arg_id)
+ [(DataAlt data_con, eq_ids ++ arg_ids, Var the_arg_id)]
+
+dictSelRule :: Int -> Arity -> Arity
+ -> IdUnfoldingFun -> [CoreExpr] -> Maybe CoreExpr
+-- Oh, very clever
+-- sel_i t1..tk (df s1..sn d1..dm) = op_i_helper s1..sn d1..dm
+-- sel_i t1..tk (D t1..tk op1 ... opm) = opi
+--
+-- NB: the data constructor has the same number of type and
+-- coercion args as the selector
+--
+-- This only works for *value* superclasses
+-- There are no selector functions for equality superclasses
+dictSelRule val_index n_ty_args n_eq_args id_unf args
+ | (dict_arg : _) <- drop n_ty_args args
+ , Just (_, _, con_args) <- exprIsConApp_maybe id_unf dict_arg
+ , let val_args = drop n_eq_args con_args
+ = Just (val_args !! val_index)
+ | otherwise
+ = Nothing
+\end{code}
- info = noCafIdInfo
- `setCafInfo` caf_info
- `setArityInfo` arity
- `setUnfoldingInfo` mkTopUnfolding rhs_w_str
- `setAllStrictnessInfo` Just strict_sig
-
- -- Allocate Ids. We do it a funny way round because field_dict_tys is
- -- almost always empty. Also note that we use max_dict_tys
- -- rather than n_dict_tys, because the latter gives an infinite loop:
- -- n_dict tys depends on the_alts, which depens on arg_ids, which depends
- -- on arity, which depends on n_dict tys. Sigh! Mega sigh!
- stupid_dict_ids = mkTemplateLocalsNum 1 stupid_dict_tys
- max_stupid_dicts = length (tyConStupidTheta tycon)
- field_dict_base = max_stupid_dicts + 1
- field_dict_ids = mkTemplateLocalsNum field_dict_base field_dict_tys
- dict_id_base = field_dict_base + n_field_dict_tys
- data_id = mkTemplateLocal dict_id_base data_ty
- arg_base = dict_id_base + 1
-
- the_alts :: [CoreAlt]
- the_alts = map mk_alt data_cons_w_field -- Already sorted by data-con
- no_default = length data_cons == length data_cons_w_field -- No default needed
-
- default_alt | no_default = []
- | otherwise = [(DEFAULT, [], error_expr)]
-
- -- The default branch may have CAF refs, because it calls recSelError etc.
- caf_info | no_default = NoCafRefs
- | otherwise = MayHaveCafRefs
-
- sel_rhs = mkLams res_tvs $ mkLams field_tyvars $
- mkLams stupid_dict_ids $ mkLams field_dict_ids $
- Lam data_id $ mk_result sel_body
-
- -- NB: A newtype always has a vanilla DataCon; no existentials etc
- -- res_tys will simply be the dataConUnivTyVars
- sel_body | isNewTyCon tycon = unwrapNewTypeBody tycon res_tys (Var data_id)
- | otherwise = Case (Var data_id) data_id field_ty (default_alt ++ the_alts)
-
- mk_result poly_result = mkVarApps (mkVarApps poly_result field_tyvars) field_dict_ids
- -- We pull the field lambdas to the top, so we need to
- -- apply them in the body. For example:
- -- data T = MkT { foo :: forall a. a->a }
- --
- -- foo :: forall a. T -> a -> a
- -- foo = /\a. \t:T. case t of { MkT f -> f a }
-
- mk_alt data_con
- = ASSERT2( res_ty `tcEqType` field_ty, ppr data_con $$ ppr res_ty $$ ppr field_ty )
- mkReboxingAlt rebox_uniqs data_con (ex_tvs ++ co_tvs ++ arg_vs) rhs
- where
- -- get pattern binders with types appropriately instantiated
- arg_uniqs = map mkBuiltinUnique [arg_base..]
- (ex_tvs, co_tvs, arg_vs) = dataConOrigInstPat arg_uniqs data_con res_tys
-
- rebox_base = arg_base + length ex_tvs + length co_tvs + length arg_vs
- rebox_uniqs = map mkBuiltinUnique [rebox_base..]
-
- -- data T :: *->* where T1 { fld :: Maybe b } -> T [b]
- -- Hence T1 :: forall a b. (a=[b]) => b -> T a
- -- fld :: forall b. T [b] -> Maybe b
- -- fld = /\b.\(t:T[b]). case t of
- -- T1 b' (c : [b]=[b']) (x:Maybe b')
- -- -> x `cast` Maybe (sym (right c))
-
- Succeeded refinement = gadtRefine emptyRefinement ex_tvs co_tvs
- (co_fn, res_ty) = refineType refinement (idType the_arg_id)
- -- Generate the refinement for b'=b,
- -- and apply to (Maybe b'), to get (Maybe b)
-
- rhs = case co_fn of
- WpCo co -> Cast (Var the_arg_id) co
- id_co -> ASSERT(isIdHsWrapper id_co) Var the_arg_id
-
- field_vs = filter (not . isPredTy . idType) arg_vs
- the_arg_id = assoc "mkRecordSelId:mk_alt" (field_lbls `zip` field_vs) field_label
- field_lbls = dataConFieldLabels data_con
-
- error_expr = mkRuntimeErrorApp rEC_SEL_ERROR_ID field_ty full_msg
- full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
+%************************************************************************
+%* *
+ Boxing and unboxing
+%* *
+%************************************************************************
+
+\begin{code}
-- unbox a product type...
-- we will recurse into newtypes, casting along the way, and unbox at the
-- first product data constructor we find. e.g.
mkUnpackCase :: Id -> CoreExpr -> [Id] -> DataCon -> CoreExpr -> CoreExpr
-- (mkUnpackCase x e args Con body)
--- returns
+-- returns
-- case (e `cast` ...) of bndr { Con args -> body }
--
-- the type of the bndr passed in is irrelevent
[Id]) -- Ids being boxed into product
reboxProduct us ty
= let
- (_tycon, _tycon_args, _pack_con, con_arg_tys) = deepSplitProductType "reboxProduct" ty
+ (_tycon, _tycon_args, _pack_con, con_arg_tys) = deepSplitProductType "reboxProduct" ty
us' = dropList con_arg_tys us
- arg_ids = zipWith (mkSysLocal FSLIT("rb")) us con_arg_tys
+ arg_ids = zipWith (mkSysLocal (fsLit "rb")) us con_arg_tys
bind_rhs = mkProductBox arg_ids ty
-- (mkReboxingAlt us con xs rhs) basically constructs the case
--- alternative (con, xs, rhs)
+-- alternative (con, xs, rhs)
-- but it does the reboxing necessary to construct the *source*
-- arguments, xs, from the representation arguments ys.
-- For example:
--- data T = MkT !(Int,Int) Bool
+-- data T = MkT !(Int,Int) Bool
--
-- mkReboxingAlt MkT [x,b] r
--- = (DataAlt MkT, [y::Int,z::Int,b], let x = (y,z) in r)
+-- = (DataAlt MkT, [y::Int,z::Int,b], let x = (y,z) in r)
--
-- mkDataAlt should really be in DataCon, but it can't because
-- it manipulates CoreSyn.
mkReboxingAlt
- :: [Unique] -- Uniques for the new Ids
+ :: [Unique] -- Uniques for the new Ids
-> DataCon
- -> [Var] -- Source-level args, including existential dicts
- -> CoreExpr -- RHS
+ -> [Var] -- Source-level args, including existential dicts
+ -> CoreExpr -- RHS
-> CoreAlt
mkReboxingAlt us con args rhs
| otherwise
= let
- (binds, args') = go args stricts us
+ (binds, args') = go args stricts us
in
(DataAlt con, args', mkLets binds rhs)
go [] _stricts _us = ([], [])
- -- Type variable case
+ -- Type variable case
go (arg:args) stricts us
- | isTyVar arg
+ | isTyCoVar arg
= let (binds, args') = go args stricts us
- in (binds, arg:args')
+ in (binds, arg:args')
- -- Term variable case
+ -- Term variable case
go (arg:args) (str:stricts) us
| isMarkedUnboxed str
=
| otherwise
= let (binds, args') = go args stricts us
in (binds, arg:args')
+ go (_ : _) [] _ = panic "mkReboxingAlt"
\end{code}
%************************************************************************
-%* *
-\subsection{Dictionary selectors}
-%* *
+%* *
+ Wrapping and unwrapping newtypes and type families
+%* *
%************************************************************************
-Selecting a field for a dictionary. If there is just one field, then
-there's nothing to do.
-
-Dictionary selectors may get nested forall-types. Thus:
-
- class Foo a where
- op :: forall b. Ord b => a -> b -> b
-
-Then the top-level type for op is
-
- op :: forall a. Foo a =>
- forall b. Ord b =>
- a -> b -> b
-
-This is unlike ordinary record selectors, which have all the for-alls
-at the outside. When dealing with classes it's very convenient to
-recover the original type signature from the class op selector.
-
\begin{code}
-mkDictSelId :: Name -> Class -> Id
-mkDictSelId name clas
- = mkGlobalId (ClassOpId clas) name sel_ty info
- where
- sel_ty = mkForAllTys tyvars (mkFunTy (idType dict_id) (idType the_arg_id))
- -- We can't just say (exprType rhs), because that would give a type
- -- C a -> C a
- -- for a single-op class (after all, the selector is the identity)
- -- But it's type must expose the representation of the dictionary
- -- to gat (say) C a -> (a -> a)
-
- info = noCafIdInfo
- `setArityInfo` 1
- `setUnfoldingInfo` mkTopUnfolding rhs
- `setAllStrictnessInfo` Just strict_sig
-
- -- We no longer use 'must-inline' on record selectors. They'll
- -- inline like crazy if they scrutinise a constructor
-
- -- The strictness signature is of the form U(AAAVAAAA) -> T
- -- where the V depends on which item we are selecting
- -- It's worth giving one, so that absence info etc is generated
- -- even if the selector isn't inlined
- strict_sig = mkStrictSig (mkTopDmdType [arg_dmd] TopRes)
- arg_dmd | isNewTyCon tycon = evalDmd
- | otherwise = Eval (Prod [ if the_arg_id == id then evalDmd else Abs
- | id <- arg_ids ])
-
- tycon = classTyCon clas
- [data_con] = tyConDataCons tycon
- tyvars = dataConUnivTyVars data_con
- arg_tys = ASSERT( isVanillaDataCon data_con ) dataConRepArgTys data_con
- the_arg_id = assoc "MkId.mkDictSelId" (map idName (classSelIds clas) `zip` arg_ids) name
-
- pred = mkClassPred clas (mkTyVarTys tyvars)
- (dict_id:arg_ids) = mkTemplateLocals (mkPredTy pred : arg_tys)
-
- rhs = mkLams tyvars (Lam dict_id rhs_body)
- rhs_body | isNewTyCon tycon = unwrapNewTypeBody tycon (map mkTyVarTy tyvars) (Var dict_id)
- | otherwise = Case (Var dict_id) dict_id (idType the_arg_id)
- [(DataAlt data_con, arg_ids, Var the_arg_id)]
-
wrapNewTypeBody :: TyCon -> [Type] -> CoreExpr -> CoreExpr
-- The wrapper for the data constructor for a newtype looks like this:
--- newtype T a = MkT (a,Int)
--- MkT :: forall a. (a,Int) -> T a
--- MkT = /\a. \(x:(a,Int)). x `cast` sym (CoT a)
+-- newtype T a = MkT (a,Int)
+-- MkT :: forall a. (a,Int) -> T a
+-- MkT = /\a. \(x:(a,Int)). x `cast` sym (CoT a)
-- where CoT is the coercion TyCon assoicated with the newtype
--
-- The call (wrapNewTypeBody T [a] e) returns the
-- body of the wrapper, namely
--- e `cast` (CoT [a])
+-- e `cast` (CoT [a])
--
--- If a coercion constructor is prodivided in the newtype, then we use
+-- If a coercion constructor is provided in the newtype, then we use
-- it, otherwise the wrap/unwrap are both no-ops
--
--- If the we are dealing with a newtype instance, we have a second coercion
+-- If the we are dealing with a newtype *instance*, we have a second coercion
-- identifying the family instance with the constructor of the newtype
-- instance. This coercion is applied in any case (ie, composed with the
-- coercion constructor of the newtype or applied by itself).
---
+
wrapNewTypeBody tycon args result_expr
= wrapFamInstBody tycon args inner
where
-- be done via a CoPat by the type checker. We have to do it this way as
-- computing the right type arguments for the coercion requires more than just
-- a spliting operation (cf, TcPat.tcConPat).
---
+
unwrapNewTypeBody :: TyCon -> [Type] -> CoreExpr -> CoreExpr
unwrapNewTypeBody tycon args result_expr
| Just co_con <- newTyConCo_maybe tycon
| otherwise
= result_expr
+-- If the type constructor is a representation type of a data instance, wrap
+-- the expression into a cast adjusting the expression type, which is an
+-- instance of the representation type, to the corresponding instance of the
+-- family instance type.
+-- See Note [Wrappers for data instance tycons]
+wrapFamInstBody :: TyCon -> [Type] -> CoreExpr -> CoreExpr
+wrapFamInstBody tycon args body
+ | Just co_con <- tyConFamilyCoercion_maybe tycon
+ = mkCoerce (mkSymCoercion (mkTyConApp co_con args)) body
+ | otherwise
+ = body
+unwrapFamInstScrut :: TyCon -> [Type] -> CoreExpr -> CoreExpr
+unwrapFamInstScrut tycon args scrut
+ | Just co_con <- tyConFamilyCoercion_maybe tycon
+ = mkCoerce (mkTyConApp co_con args) scrut
+ | otherwise
+ = scrut
\end{code}
%************************************************************************
-%* *
-\subsection{Primitive operations
-%* *
+%* *
+\subsection{Primitive operations}
+%* *
%************************************************************************
\begin{code}
(tyvars,arg_tys,res_ty, arity, strict_sig) = primOpSig prim_op
ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
name = mkWiredInName gHC_PRIM (primOpOcc prim_op)
- (mkPrimOpIdUnique (primOpTag prim_op))
- Nothing (AnId id) UserSyntax
+ (mkPrimOpIdUnique (primOpTag prim_op))
+ (AnId id) UserSyntax
id = mkGlobalId (PrimOpId prim_op) name ty info
-
+
info = noCafIdInfo
- `setSpecInfo` mkSpecInfo (primOpRules prim_op name)
- `setArityInfo` arity
- `setAllStrictnessInfo` Just strict_sig
+ `setSpecInfo` mkSpecInfo (primOpRules prim_op name)
+ `setArityInfo` arity
+ `setStrictnessInfo` Just strict_sig
-- For each ccall we manufacture a separate CCallOpId, giving it
-- a fresh unique, a type that is correct for this particular ccall,
mkFCallId :: Unique -> ForeignCall -> Type -> Id
mkFCallId uniq fcall ty
= ASSERT( isEmptyVarSet (tyVarsOfType ty) )
- -- A CCallOpId should have no free type variables;
- -- when doing substitutions won't substitute over it
+ -- A CCallOpId should have no free type variables;
+ -- when doing substitutions won't substitute over it
mkGlobalId (FCallId fcall) name ty info
where
occ_str = showSDoc (braces (ppr fcall <+> ppr ty))
- -- The "occurrence name" of a ccall is the full info about the
- -- ccall; it is encoded, but may have embedded spaces etc!
+ -- The "occurrence name" of a ccall is the full info about the
+ -- ccall; it is encoded, but may have embedded spaces etc!
name = mkFCallName uniq occ_str
info = noCafIdInfo
- `setArityInfo` arity
- `setAllStrictnessInfo` Just strict_sig
+ `setArityInfo` arity
+ `setStrictnessInfo` Just strict_sig
- (_, tau) = tcSplitForAllTys ty
+ (_, tau) = tcSplitForAllTys ty
(arg_tys, _) = tcSplitFunTys tau
- arity = length arg_tys
+ arity = length arg_tys
strict_sig = mkStrictSig (mkTopDmdType (replicate arity evalDmd) TopRes)
+
+-- Tick boxes and breakpoints are both represented as TickBoxOpIds,
+-- except for the type:
+--
+-- a plain HPC tick box has type (State# RealWorld)
+-- a breakpoint Id has type forall a.a
+--
+-- The breakpoint Id will be applied to a list of arbitrary free variables,
+-- which is why it needs a polymorphic type.
+
+mkTickBoxOpId :: Unique -> Module -> TickBoxId -> Id
+mkTickBoxOpId uniq mod ix = mkTickBox' uniq mod ix realWorldStatePrimTy
+
+mkBreakPointOpId :: Unique -> Module -> TickBoxId -> Id
+mkBreakPointOpId uniq mod ix = mkTickBox' uniq mod ix ty
+ where ty = mkSigmaTy [openAlphaTyVar] [] openAlphaTy
+
+mkTickBox' :: Unique -> Module -> TickBoxId -> Type -> Id
+mkTickBox' uniq mod ix ty = mkGlobalId (TickBoxOpId tickbox) name ty info
+ where
+ tickbox = TickBox mod ix
+ occ_str = showSDoc (braces (ppr tickbox))
+ name = mkTickBoxOpName uniq occ_str
+ info = noCafIdInfo
\end{code}
%************************************************************************
-%* *
+%* *
\subsection{DictFuns and default methods}
-%* *
+%* *
%************************************************************************
Important notes about dict funs and default methods
that they aren't discarded by the occurrence analyser.
\begin{code}
-mkDefaultMethodId dm_name ty = mkExportedLocalId dm_name ty
-
-mkDictFunId :: Name -- Name to use for the dict fun;
- -> [TyVar]
- -> ThetaType
- -> Class
- -> [Type]
- -> Id
+mkDefaultMethodId :: Id -- Selector Id
+ -> Name -- Default method name
+ -> Id -- Default method Id
+mkDefaultMethodId sel_id dm_name = mkExportedLocalId dm_name (idType sel_id)
+
+mkDictFunId :: Name -- Name to use for the dict fun;
+ -> [TyVar]
+ -> ThetaType
+ -> Class
+ -> [Type]
+ -> Id
mkDictFunId dfun_name inst_tyvars dfun_theta clas inst_tys
- = mkExportedLocalId dfun_name dfun_ty
+ = mkExportedLocalVar (DFunId is_nt) dfun_name dfun_ty vanillaIdInfo
where
+ is_nt = isNewTyCon (classTyCon clas)
dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
-
-{- 1 dec 99: disable the Mark Jones optimisation for the sake
- of compatibility with Hugs.
- See `types/InstEnv' for a discussion related to this.
-
- (class_tyvars, sc_theta, _, _) = classBigSig clas
- not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
- sc_theta' = substClasses (zipTopTvSubst class_tyvars inst_tys) sc_theta
- dfun_theta = case inst_decl_theta of
- [] -> [] -- If inst_decl_theta is empty, then we don't
- -- want to have any dict arguments, so that we can
- -- expose the constant methods.
-
- other -> nub (inst_decl_theta ++ filter not_const sc_theta')
- -- Otherwise we pass the superclass dictionaries to
- -- the dictionary function; the Mark Jones optimisation.
- --
- -- NOTE the "nub". I got caught by this one:
- -- class Monad m => MonadT t m where ...
- -- instance Monad m => MonadT (EnvT env) m where ...
- -- Here, the inst_decl_theta has (Monad m); but so
- -- does the sc_theta'!
- --
- -- NOTE the "not_const". I got caught by this one too:
- -- class Foo a => Baz a b where ...
- -- instance Wob b => Baz T b where..
- -- Now sc_theta' has Foo T
--}
\end{code}
%************************************************************************
-%* *
+%* *
\subsection{Un-definable}
-%* *
+%* *
%************************************************************************
These Ids can't be defined in Haskell. They could be defined in
another gun with which to shoot yourself in the foot.
\begin{code}
-mkWiredInIdName mod fs uniq id
- = mkWiredInName mod (mkOccNameFS varName fs) uniq Nothing (AnId id) UserSyntax
-
-unsafeCoerceName = mkWiredInIdName gHC_PRIM FSLIT("unsafeCoerce#") unsafeCoerceIdKey unsafeCoerceId
-nullAddrName = mkWiredInIdName gHC_PRIM FSLIT("nullAddr#") nullAddrIdKey nullAddrId
-seqName = mkWiredInIdName gHC_PRIM FSLIT("seq") seqIdKey seqId
-realWorldName = mkWiredInIdName gHC_PRIM FSLIT("realWorld#") realWorldPrimIdKey realWorldPrimId
-lazyIdName = mkWiredInIdName gHC_BASE FSLIT("lazy") lazyIdKey lazyId
-
-errorName = mkWiredInIdName gHC_ERR FSLIT("error") errorIdKey eRROR_ID
-recSelErrorName = mkWiredInIdName gHC_ERR FSLIT("recSelError") recSelErrorIdKey rEC_SEL_ERROR_ID
-runtimeErrorName = mkWiredInIdName gHC_ERR FSLIT("runtimeError") runtimeErrorIdKey rUNTIME_ERROR_ID
-irrefutPatErrorName = mkWiredInIdName gHC_ERR FSLIT("irrefutPatError") irrefutPatErrorIdKey iRREFUT_PAT_ERROR_ID
-recConErrorName = mkWiredInIdName gHC_ERR FSLIT("recConError") recConErrorIdKey rEC_CON_ERROR_ID
-patErrorName = mkWiredInIdName gHC_ERR FSLIT("patError") patErrorIdKey pAT_ERROR_ID
-noMethodBindingErrorName = mkWiredInIdName gHC_ERR FSLIT("noMethodBindingError")
- noMethodBindingErrorIdKey nO_METHOD_BINDING_ERROR_ID
-nonExhaustiveGuardsErrorName
- = mkWiredInIdName gHC_ERR FSLIT("nonExhaustiveGuardsError")
- nonExhaustiveGuardsErrorIdKey nON_EXHAUSTIVE_GUARDS_ERROR_ID
+lazyIdName, unsafeCoerceName, nullAddrName, seqName, realWorldName :: Name
+unsafeCoerceName = mkWiredInIdName gHC_PRIM (fsLit "unsafeCoerce#") unsafeCoerceIdKey unsafeCoerceId
+nullAddrName = mkWiredInIdName gHC_PRIM (fsLit "nullAddr#") nullAddrIdKey nullAddrId
+seqName = mkWiredInIdName gHC_PRIM (fsLit "seq") seqIdKey seqId
+realWorldName = mkWiredInIdName gHC_PRIM (fsLit "realWorld#") realWorldPrimIdKey realWorldPrimId
+lazyIdName = mkWiredInIdName gHC_BASE (fsLit "lazy") lazyIdKey lazyId
\end{code}
\begin{code}
+------------------------------------------------
-- unsafeCoerce# :: forall a b. a -> b
+unsafeCoerceId :: Id
unsafeCoerceId
= pcMiscPrelId unsafeCoerceName ty info
where
info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
-
+
- ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
- (mkFunTy openAlphaTy openBetaTy)
- [x] = mkTemplateLocals [openAlphaTy]
- rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
--- Note (Coerce openBetaTy openAlphaTy) (Var x)
- Cast (Var x) (mkUnsafeCoercion openAlphaTy openBetaTy)
+ ty = mkForAllTys [argAlphaTyVar,openBetaTyVar]
+ (mkFunTy argAlphaTy openBetaTy)
+ [x] = mkTemplateLocals [argAlphaTy]
+ rhs = mkLams [argAlphaTyVar,openBetaTyVar,x] $
+ Cast (Var x) (mkUnsafeCoercion argAlphaTy openBetaTy)
+------------------------------------------------
+nullAddrId :: Id
-- nullAddr# :: Addr#
-- The reason is is here is because we don't provide
-- a way to write this literal in Haskell.
-nullAddrId
- = pcMiscPrelId nullAddrName addrPrimTy info
+nullAddrId = pcMiscPrelId nullAddrName addrPrimTy info
where
info = noCafIdInfo `setUnfoldingInfo`
- mkCompulsoryUnfolding (Lit nullAddrLit)
+ mkCompulsoryUnfolding (Lit nullAddrLit)
-seqId
- = pcMiscPrelId seqName ty info
+------------------------------------------------
+seqId :: Id -- See Note [seqId magic]
+seqId = pcMiscPrelId seqName ty info
where
info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
-
-
- ty = mkForAllTys [alphaTyVar,openBetaTyVar]
- (mkFunTy alphaTy (mkFunTy openBetaTy openBetaTy))
- [x,y] = mkTemplateLocals [alphaTy, openBetaTy]
- rhs = mkLams [alphaTyVar,openBetaTyVar,x,y] (Case (Var x) x openBetaTy [(DEFAULT, [], Var y)])
-
--- lazy :: forall a?. a? -> a? (i.e. works for unboxed types too)
--- Used to lazify pseq: pseq a b = a `seq` lazy b
---
--- Also, no strictness: by being a built-in Id, all the info about lazyId comes from here,
--- not from GHC.Base.hi. This is important, because the strictness
--- analyser will spot it as strict!
---
--- Also no unfolding in lazyId: it gets "inlined" by a HACK in the worker/wrapper pass
--- (see WorkWrap.wwExpr)
--- We could use inline phases to do this, but that would be vulnerable to changes in
--- phase numbering....we must inline precisely after strictness analysis.
-lazyId
- = pcMiscPrelId lazyIdName ty info
+ `setSpecInfo` mkSpecInfo [seq_cast_rule]
+
+
+ ty = mkForAllTys [alphaTyVar,argBetaTyVar]
+ (mkFunTy alphaTy (mkFunTy argBetaTy argBetaTy))
+ [x,y] = mkTemplateLocals [alphaTy, argBetaTy]
+ rhs = mkLams [alphaTyVar,argBetaTyVar,x,y] (Case (Var x) x argBetaTy [(DEFAULT, [], Var y)])
+
+ -- See Note [Built-in RULES for seq]
+ seq_cast_rule = BuiltinRule { ru_name = fsLit "seq of cast"
+ , ru_fn = seqName
+ , ru_nargs = 4
+ , ru_try = match_seq_of_cast
+ }
+
+match_seq_of_cast :: IdUnfoldingFun -> [CoreExpr] -> Maybe CoreExpr
+ -- See Note [Built-in RULES for seq]
+match_seq_of_cast _ [Type _, Type res_ty, Cast scrut co, expr]
+ = Just (Var seqId `mkApps` [Type (fst (coercionKind co)), Type res_ty,
+ scrut, expr])
+match_seq_of_cast _ _ = Nothing
+
+------------------------------------------------
+lazyId :: Id -- See Note [lazyId magic]
+lazyId = pcMiscPrelId lazyIdName ty info
where
info = noCafIdInfo
ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy alphaTy)
-
-lazyIdUnfolding :: CoreExpr -- Used to expand 'lazyId' after strictness anal
-lazyIdUnfolding = mkLams [openAlphaTyVar,x] (Var x)
- where
- [x] = mkTemplateLocals [openAlphaTy]
\end{code}
-@realWorld#@ used to be a magic literal, \tr{void#}. If things get
-nasty as-is, change it back to a literal (@Literal@).
+Note [seqId magic]
+~~~~~~~~~~~~~~~~~~
+'GHC.Prim.seq' is special in several ways.
-voidArgId is a Local Id used simply as an argument in functions
-where we just want an arg to avoid having a thunk of unlifted type.
-E.g.
- x = \ void :: State# RealWorld -> (# p, q #)
+a) Its second arg can have an unboxed type
+ x `seq` (v +# w)
-This comes up in strictness analysis
+b) Its fixity is set in LoadIface.ghcPrimIface
-\begin{code}
-realWorldPrimId -- :: State# RealWorld
- = pcMiscPrelId realWorldName realWorldStatePrimTy
- (noCafIdInfo `setUnfoldingInfo` evaldUnfolding)
- -- The evaldUnfolding makes it look that realWorld# is evaluated
- -- which in turn makes Simplify.interestingArg return True,
- -- which in turn makes INLINE things applied to realWorld# likely
- -- to be inlined
-
-voidArgId -- :: State# RealWorld
- = mkSysLocal FSLIT("void") voidArgIdKey realWorldStatePrimTy
-\end{code}
+c) It has quite a bit of desugaring magic.
+ See DsUtils.lhs Note [Desugaring seq (1)] and (2) and (3)
+d) There is some special rule handing: Note [User-defined RULES for seq]
-%************************************************************************
-%* *
-\subsection[PrelVals-error-related]{@error@ and friends; @trace@}
-%* *
-%************************************************************************
+e) See Note [Typing rule for seq] in TcExpr.
-GHC randomly injects these into the code.
+Note [User-defined RULES for seq]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Roman found situations where he had
+ case (f n) of _ -> e
+where he knew that f (which was strict in n) would terminate if n did.
+Notice that the result of (f n) is discarded. So it makes sense to
+transform to
+ case n of _ -> e
-@patError@ is just a version of @error@ for pattern-matching
-failures. It knows various ``codes'' which expand to longer
-strings---this saves space!
+Rather than attempt some general analysis to support this, I've added
+enough support that you can do this using a rewrite rule:
-@absentErr@ is a thing we put in for ``absent'' arguments. They jolly
-well shouldn't be yanked on, but if one is, then you will get a
-friendly message from @absentErr@ (rather than a totally random
-crash).
+ RULE "f/seq" forall n. seq (f n) e = seq n e
-@parError@ is a special version of @error@ which the compiler does
-not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
-templates, but we don't ever expect to generate code for it.
+You write that rule. When GHC sees a case expression that discards
+its result, it mentally transforms it to a call to 'seq' and looks for
+a RULE. (This is done in Simplify.rebuildCase.) As usual, the
+correctness of the rule is up to you.
-\begin{code}
-mkRuntimeErrorApp
- :: Id -- Should be of type (forall a. Addr# -> a)
- -- where Addr# points to a UTF8 encoded string
- -> Type -- The type to instantiate 'a'
- -> String -- The string to print
- -> CoreExpr
-
-mkRuntimeErrorApp err_id res_ty err_msg
- = mkApps (Var err_id) [Type res_ty, err_string]
- where
- err_string = Lit (mkStringLit err_msg)
-
-rEC_SEL_ERROR_ID = mkRuntimeErrorId recSelErrorName
-rUNTIME_ERROR_ID = mkRuntimeErrorId runtimeErrorName
-iRREFUT_PAT_ERROR_ID = mkRuntimeErrorId irrefutPatErrorName
-rEC_CON_ERROR_ID = mkRuntimeErrorId recConErrorName
-pAT_ERROR_ID = mkRuntimeErrorId patErrorName
-nO_METHOD_BINDING_ERROR_ID = mkRuntimeErrorId noMethodBindingErrorName
-nON_EXHAUSTIVE_GUARDS_ERROR_ID = mkRuntimeErrorId nonExhaustiveGuardsErrorName
-
--- The runtime error Ids take a UTF8-encoded string as argument
-mkRuntimeErrorId name = pc_bottoming_Id name runtimeErrorTy
-runtimeErrorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTy addrPrimTy openAlphaTy)
-\end{code}
+To make this work, we need to be careful that the magical desugaring
+done in Note [seqId magic] item (c) is *not* done on the LHS of a rule.
+Or rather, we arrange to un-do it, in DsBinds.decomposeRuleLhs.
-\begin{code}
-eRROR_ID = pc_bottoming_Id errorName errorTy
+Note [Built-in RULES for seq]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+We also have the following built-in rule for seq
-errorTy :: Type
-errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy] openAlphaTy)
- -- Notice the openAlphaTyVar. It says that "error" can be applied
- -- to unboxed as well as boxed types. This is OK because it never
- -- returns, so the return type is irrelevant.
-\end{code}
+ seq (x `cast` co) y = seq x y
+This eliminates unnecessary casts and also allows other seq rules to
+match more often. Notably,
+
+ seq (f x `cast` co) y --> seq (f x) y
+
+and now a user-defined rule for seq (see Note [User-defined RULES for seq])
+may fire.
+
+
+Note [lazyId magic]
+~~~~~~~~~~~~~~~~~~~
+ lazy :: forall a?. a? -> a? (i.e. works for unboxed types too)
+
+Used to lazify pseq: pseq a b = a `seq` lazy b
+
+Also, no strictness: by being a built-in Id, all the info about lazyId comes from here,
+not from GHC.Base.hi. This is important, because the strictness
+analyser will spot it as strict!
+
+Also no unfolding in lazyId: it gets "inlined" by a HACK in CorePrep.
+It's very important to do this inlining *after* unfoldings are exposed
+in the interface file. Otherwise, the unfolding for (say) pseq in the
+interface file will not mention 'lazy', so if we inline 'pseq' we'll totally
+miss the very thing that 'lazy' was there for in the first place.
+See Trac #3259 for a real world example.
+
+lazyId is defined in GHC.Base, so we don't *have* to inline it. If it
+appears un-applied, we'll end up just calling it.
+
+-------------------------------------------------------------
+@realWorld#@ used to be a magic literal, \tr{void#}. If things get
+nasty as-is, change it back to a literal (@Literal@).
+
+voidArgId is a Local Id used simply as an argument in functions
+where we just want an arg to avoid having a thunk of unlifted type.
+E.g.
+ x = \ void :: State# RealWorld -> (# p, q #)
+
+This comes up in strictness analysis
+
+\begin{code}
+realWorldPrimId :: Id
+realWorldPrimId -- :: State# RealWorld
+ = pcMiscPrelId realWorldName realWorldStatePrimTy
+ (noCafIdInfo `setUnfoldingInfo` evaldUnfolding)
+ -- The evaldUnfolding makes it look that realWorld# is evaluated
+ -- which in turn makes Simplify.interestingArg return True,
+ -- which in turn makes INLINE things applied to realWorld# likely
+ -- to be inlined
+
+voidArgId :: Id
+voidArgId -- :: State# RealWorld
+ = mkSysLocal (fsLit "void") voidArgIdKey realWorldStatePrimTy
+\end{code}
-%************************************************************************
-%* *
-\subsection{Utilities}
-%* *
-%************************************************************************
\begin{code}
pcMiscPrelId :: Name -> Type -> IdInfo -> Id
pcMiscPrelId name ty info
- = mkVanillaGlobal name ty info
+ = mkVanillaGlobalWithInfo name ty info
-- We lie and say the thing is imported; otherwise, we get into
-- a mess with dependency analysis; e.g., core2stg may heave in
-- random calls to GHCbase.unpackPS__. If GHCbase is the module
-- being compiled, then it's just a matter of luck if the definition
-- will be in "the right place" to be in scope.
-
-pc_bottoming_Id name ty
- = pcMiscPrelId name ty bottoming_info
- where
- bottoming_info = vanillaIdInfo `setAllStrictnessInfo` Just strict_sig
- -- Do *not* mark them as NoCafRefs, because they can indeed have
- -- CAF refs. For example, pAT_ERROR_ID calls GHC.Err.untangle,
- -- which has some CAFs
- -- In due course we may arrange that these error-y things are
- -- regarded by the GC as permanently live, in which case we
- -- can give them NoCaf info. As it is, any function that calls
- -- any pc_bottoming_Id will itself have CafRefs, which bloats
- -- SRTs.
-
- strict_sig = mkStrictSig (mkTopDmdType [evalDmd] BotRes)
- -- These "bottom" out, no matter what their arguments
-
-(openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
-openAlphaTy = mkTyVarTy openAlphaTyVar
-openBetaTy = mkTyVarTy openBetaTyVar
\end{code}
-
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