X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FbasicTypes%2FMkId.lhs;h=16c45b758395b1e708144b5a6dcc0cdbfe1858b4;hp=1dd990e4cf9ed497686346075b4da1edf606a862;hb=77166b1729061531eeb77c33f4d3b2581f7d4c41;hpb=d95ce839533391e7118257537044f01cbb1d6694 diff --git a/compiler/basicTypes/MkId.lhs b/compiler/basicTypes/MkId.lhs index 1dd990e..16c45b7 100644 --- a/compiler/basicTypes/MkId.lhs +++ b/compiler/basicTypes/MkId.lhs @@ -24,7 +24,6 @@ module MkId ( mkDictSelId, mkDataConIds, - mkRecordSelId, mkPrimOpId, mkFCallId, mkTickBoxOpId, mkBreakPointOpId, mkReboxingAlt, wrapNewTypeBody, unwrapNewTypeBody, @@ -34,12 +33,12 @@ module MkId ( -- And some particular Ids; see below for why they are wired in wiredInIds, ghcPrimIds, unsafeCoerceId, realWorldPrimId, voidArgId, nullAddrId, seqId, - lazyId, lazyIdUnfolding, lazyIdKey, + lazyId, lazyIdKey, - mkRuntimeErrorApp, + mkRuntimeErrorApp, mkImpossibleExpr, 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, + pAT_ERROR_ID, eRROR_ID, rEC_SEL_ERROR_ID, unsafeCoerceName ) where @@ -50,30 +49,25 @@ import Rules import TysPrim import TysWiredIn import PrelRules -import Unify import Type -import TypeRep import Coercion import TcType -import CoreUtils +import CoreUtils ( exprType, mkCoerce ) import CoreUnfold import Literal import TyCon import Class import VarSet import Name -import OccName import PrimOp import ForeignCall import DataCon import Id -import Var ( Var, TyVar, mkCoVar) +import Var ( Var, TyVar, mkCoVar, mkExportedLocalVar ) import IdInfo -import NewDemand -import DmdAnal +import Demand import CoreSyn import Unique -import Maybes import PrelNames import BasicTypes hiding ( SuccessFlag(..) ) import Util @@ -89,17 +83,42 @@ import Module %* * %************************************************************************ +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 @@ -113,6 +132,7 @@ wiredInIds nO_METHOD_BINDING_ERROR_ID, pAT_ERROR_ID, rEC_CON_ERROR_ID, + rEC_SEL_ERROR_ID, lazyId ] ++ ghcPrimIds @@ -245,7 +265,7 @@ mkDataConIds wrap_name wkr_name data_con wkr_arity = dataConRepArity data_con wkr_info = noCafIdInfo `setArityInfo` wkr_arity - `setAllStrictnessInfo` Just wkr_sig + `setStrictnessInfo` Just wkr_sig `setUnfoldingInfo` evaldUnfolding -- Record that it's evaluated, -- even if arity = 0 @@ -280,24 +300,14 @@ mkDataConIds wrap_name wkr_name data_con nt_work_info = noCafIdInfo -- The NoCaf-ness is set by noCafIdInfo `setArityInfo` 1 -- Arity 1 `setUnfoldingInfo` newtype_unf - newtype_unf = -- The assertion below is no longer correct: - -- there may be a dict theta rather than a singleton orig_arg_ty - -- 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 (...) + 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) + wrapNewTypeBody tycon res_ty_args (Var id_arg1) - id_arg1 = mkTemplateLocal 1 - (if null orig_arg_tys - then ASSERT(not (null $ dataConDictTheta data_con)) - mkPredTy $ head (dataConDictTheta data_con) - else head orig_arg_tys - ) ----------- Wrapper -------------- -- We used to include the stupid theta in the wrapper's args @@ -319,7 +329,7 @@ mkDataConIds wrap_name wkr_name data_con -- It's important to specify the arity, so that partial -- applications are treated as values `setUnfoldingInfo` wrap_unf - `setAllStrictnessInfo` Just wrap_sig + `setStrictnessInfo` Just wrap_sig all_strict_marks = dataConExStricts data_con ++ dataConStrictMarks data_con wrap_sig = mkStrictSig (mkTopDmdType arg_dmds cpr_info) @@ -335,7 +345,7 @@ mkDataConIds wrap_name wkr_name data_con -- ...(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 (length dict_args + length id_args) + 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 $ @@ -396,301 +406,139 @@ mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n) 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 } - - unN :: forall b. N -> b -> b - unN = /\b -> \n:N -> (coerce (forall a. a->a) n) - +Selecting a field for a dictionary. If there is just one field, then +there's nothing to do. -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. +Dictionary selectors may get nested forall-types. Thus: -In general, a field is naughty if its type mentions a type variable that -isn't in the result type of the constructor. + class Foo a where + op :: 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 :: Maybe a } :: T [a] - T2 { f :: Maybe a, y :: b } :: T [a] +Then the top-level type for op is -and now the selector takes that result type as its argument: - f :: forall a. T [a] -> Maybe a + op :: forall a. Foo a => + forall b. Ord b => + a -> b -> b -Details: the "real" types of T1,T2 are: - T1 :: forall r a. (r~[a]) => a -> T r - T2 :: forall r a b. (r~[a]) => a -> b -> T r +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. -So the selector loooks like this: - f :: forall a. T [a] -> Maybe a - f (a:*) (t:T [a]) - = case t of - T1 c (g:[a]~[c]) (v:Maybe c) -> v `cast` Maybe (right (sym g)) - T2 c d (g:[a]~[c]) (v:Maybe c) (w:d) -> v `cast` Maybe (right (sym g)) +\begin{code} +mkDictSelId :: Bool -- True <=> don't include the unfolding + -- Little point on imports without -O, because the + -- dictionary itself won't be visible + -> Name -> Class -> Id +mkDictSelId no_unf 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 get (say) C a -> (a -> a) -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). + 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 index n_ty_args } -Note the need for casts in the result! + -- 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 ]) -Note [Selector running example] -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -It's OK to combine GADTs and type families. Here's a running example: + tycon = classTyCon clas + new_tycon = isNewTyCon tycon + [data_con] = tyConDataCons tycon + tyvars = dataConUnivTyVars data_con + arg_tys = {- ASSERT( isVanillaDataCon data_con ) -} dataConRepArgTys data_con + eq_theta = dataConEqTheta data_con + index = assoc "MkId.mkDictSelId" (map idName (classSelIds clas) `zip` [0..]) name + the_arg_id = arg_ids !! index - data instance T [a] where - T1 { fld :: b } :: T [Maybe b] + pred = mkClassPred clas (mkTyVarTys tyvars) + dict_id = mkTemplateLocal 1 $ mkPredTy pred + (eq_ids,n) = mkCoVarLocals 2 $ mkPredTys eq_theta + arg_ids = mkTemplateLocalsNum n arg_tys -The representation type looks like this - data :R7T a where - T1 { fld :: b } :: :R7T (Maybe b) + 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) -and there's coercion from the family type to the representation type - :CoR7T a :: T [a] ~ :R7T a + 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 -> IdUnfoldingFun -> [CoreExpr] -> Maybe CoreExpr +-- Oh, very clever +-- op_i t1..tk (df s1..sn d1..dm) = op_i_helper s1..sn d1..dm +-- op_i t1..tk (D t1..tk op1 ... opm) = opi +-- +-- NB: the data constructor has the same number of type args as the class op -The selector we want for fld looks like this: +dictSelRule index n_ty_args id_unf args + | (dict_arg : _) <- drop n_ty_args args + , Just (_, _, val_args) <- exprIsConApp_maybe id_unf dict_arg + = Just (val_args !! index) + | otherwise + = Nothing +\end{code} - fld :: forall b. T [Maybe b] -> b - fld = /\b. \(d::T [Maybe b]). - case d `cast` :CoR7T (Maybe b) of - T1 (x::b) -> x -The scrutinee of the case has type :R7T (Maybe b), which can be -gotten by appying the eq_spec to the univ_tvs of the data con. +%************************************************************************ +%* * + Boxing and unboxing +%* * +%************************************************************************ \begin{code} -mkRecordSelId :: TyCon -> FieldLabel -> Id -mkRecordSelId tycon field_label - -- Assumes that all fields with the same field label have the same type - = sel_id - where - -- Because this function gets called by implicitTyThings, we need to - -- produce the OccName of the Id without doing any suspend type checks. - -- (see the note [Tricky iface loop]). - -- A suspended type-check is sometimes necessary to compute field_ty, - -- so we need to make sure that we suspend anything that depends on field_ty. - - -- the overall result - sel_id = mkGlobalId sel_id_details field_label theType theInfo - - -- check whether the type is naughty: this thunk does not get forced - -- until the type is actually needed - field_ty = dataConFieldType con1 field_label - is_naughty = not (tyVarsOfType field_ty `subVarSet` data_tv_set) - - -- it's important that this doesn't force the if - (theType, theInfo) = if is_naughty - -- Escapist case here for naughty constructors - -- We give it no IdInfo, and a type of - -- forall a.a (never looked at) - then (forall_a_a, noCafIdInfo) - -- otherwise do the real case - else (selector_ty, info) - - sel_id_details = RecordSelId { sel_tycon = tycon, - sel_label = field_label, - sel_naughty = is_naughty } - -- For a data type family, the tycon is the *instance* TyCon - - -- for naughty case - forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar) - - -- real case starts here: - 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 = ASSERT( not (null data_cons_w_field) ) head data_cons_w_field - (univ_tvs, _, eq_spec, _, _, _, data_ty) = dataConFullSig con1 - -- For a data type family, the data_ty (and hence selector_ty) mentions - -- only the family TyCon, not the instance TyCon - data_tv_set = tyVarsOfType data_ty - data_tvs = varSetElems data_tv_set - - -- _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 data_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! - - info = noCafIdInfo - `setCafInfo` caf_info - `setArityInfo` arity - `setUnfoldingInfo` unfolding - `setAllStrictnessInfo` Just strict_sig - - unfolding = mkImplicitUnfolding rhs_w_str - - -- 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 - scrut_id = mkTemplateLocal (dict_id_base+1) scrut_ty - arg_base = dict_id_base + 2 - - 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 data_tvs $ mkLams field_tyvars $ - mkLams stupid_dict_ids $ mkLams field_dict_ids $ - Lam data_id $ mk_result sel_body - - scrut_ty_args = substTyVars (mkTopTvSubst eq_spec) univ_tvs - scrut_ty = mkTyConApp tycon scrut_ty_args - scrut = unwrapFamInstScrut tycon scrut_ty_args (Var data_id) - -- First coerce from the type family to the representation type - - -- NB: A newtype always has a vanilla DataCon; no existentials etc - -- data_tys will simply be the dataConUnivTyVars - sel_body | isNewTyCon tycon = unwrapNewTypeBody tycon scrut_ty_args scrut - | otherwise = Case scrut scrut_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 - = 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 - scrut_ty_args - - 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)) - - -- Generate the cast for the result - -- See Note [GADT record selectors] for why a cast is needed - in_scope_tvs = ex_tvs ++ co_tvs ++ data_tvs - reft = matchRefine in_scope_tvs (map (mkSymCoercion . mkTyVarTy) co_tvs) - rhs = case refineType reft (idType the_arg_id) of - Nothing -> Var the_arg_id - Just (co, data_ty) -> ASSERT2( data_ty `tcEqType` field_ty, - ppr data_con $$ ppr data_ty $$ ppr field_ty ) - Cast (Var the_arg_id) co - - 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]) - -- 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. @@ -824,87 +672,6 @@ mkReboxingAlt us con args rhs %************************************************************************ %* * -\subsection{Dictionary selectors} -%* * -%************************************************************************ - -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 :: Bool -- True <=> don't include the unfolding - -- Little point on imports without -O, because the - -- dictionary itself won't be visible - -> Name -> Class -> Id -mkDictSelId no_unf 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 get (say) C a -> (a -> a) - - info = noCafIdInfo - `setArityInfo` 1 - `setAllStrictnessInfo` Just strict_sig - `setUnfoldingInfo` (if no_unf then noUnfolding - else mkImplicitUnfolding rhs) - - -- 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 - eq_theta = dataConEqTheta data_con - the_arg_id = assoc "MkId.mkDictSelId" (map idName (classSelIds clas) `zip` arg_ids) name - - pred = mkClassPred clas (mkTyVarTys tyvars) - dict_id = mkTemplateLocal 1 $ mkPredTy pred - (eq_ids,n) = mkCoVarLocals 2 $ mkPredTys eq_theta - arg_ids = mkTemplateLocalsNum n arg_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) - - 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, eq_ids ++ arg_ids, Var the_arg_id)] -\end{code} - - -%************************************************************************ -%* * Wrapping and unwrapping newtypes and type families %* * %************************************************************************ @@ -992,7 +759,7 @@ mkPrimOpId prim_op info = noCafIdInfo `setSpecInfo` mkSpecInfo (primOpRules prim_op name) `setArityInfo` arity - `setAllStrictnessInfo` Just strict_sig + `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, @@ -1018,7 +785,7 @@ mkFCallId uniq fcall ty info = noCafIdInfo `setArityInfo` arity - `setAllStrictnessInfo` Just strict_sig + `setStrictnessInfo` Just strict_sig (_, tau) = tcSplitForAllTys ty (arg_tys, _) = tcSplitFunTys tau @@ -1091,37 +858,10 @@ mkDictFunId :: Name -- Name to use for the dict fun; -> 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} @@ -1195,14 +935,11 @@ nullAddrId = pcMiscPrelId nullAddrName addrPrimTy info mkCompulsoryUnfolding (Lit nullAddrLit) ------------------------------------------------ -seqId :: Id --- 'seq' is very special. See notes with --- See DsUtils.lhs Note [Desugaring seq (1)] and --- Note [Desugaring seq (2)] and --- Fixity is set in LoadIface.ghcPrimIface +seqId :: Id -- See Note [seqId magic] seqId = pcMiscPrelId seqName ty info where info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs + `setSpecInfo` mkSpecInfo [seq_cast_rule] ty = mkForAllTys [alphaTyVar,openBetaTyVar] @@ -1210,30 +947,101 @@ seqId = pcMiscPrelId seqName ty info [x,y] = mkTemplateLocals [alphaTy, openBetaTy] rhs = mkLams [alphaTyVar,openBetaTyVar,x,y] (Case (Var x) x openBetaTy [(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 --- 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/wrapperpass --- (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 :: 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} +Note [seqId magic] +~~~~~~~~~~~~~~~~~~ +'GHC.Prim.seq' is special in several ways. + +a) Its second arg can have an unboxed type + x `seq` (v +# w) + +b) Its fixity is set in LoadIface.ghcPrimIface + +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] + +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 + +Rather than attempt some general analysis to support this, I've added +enough support that you can do this using a rewrite rule: + + RULE "f/seq" forall n. seq (f n) e = seq n e + +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. + +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. + +Note [Built-in RULES for seq] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +We also have the following built-in rule for seq + + 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@). @@ -1293,6 +1101,10 @@ mkRuntimeErrorApp err_id res_ty err_msg where err_string = Lit (mkMachString err_msg) +mkImpossibleExpr :: Type -> CoreExpr +mkImpossibleExpr res_ty + = mkRuntimeErrorApp rUNTIME_ERROR_ID res_ty "Impossible case alternative" + rEC_SEL_ERROR_ID = mkRuntimeErrorId recSelErrorName rUNTIME_ERROR_ID = mkRuntimeErrorId runtimeErrorName iRREFUT_PAT_ERROR_ID = mkRuntimeErrorId irrefutPatErrorName @@ -1307,7 +1119,7 @@ mkRuntimeErrorId :: Name -> Id mkRuntimeErrorId name = pc_bottoming_Id name runtimeErrorTy runtimeErrorTy :: Type -runtimeErrorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTy addrPrimTy openAlphaTy) +runtimeErrorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTy addrPrimTy openAlphaTy) \end{code} \begin{code} @@ -1342,7 +1154,7 @@ pc_bottoming_Id :: Name -> Type -> Id pc_bottoming_Id name ty = pcMiscPrelId name ty bottoming_info where - bottoming_info = vanillaIdInfo `setAllStrictnessInfo` Just strict_sig + bottoming_info = vanillaIdInfo `setStrictnessInfo` Just strict_sig `setArityInfo` 1 -- Make arity and strictness agree