2 % (c) The AQUA Project, Glasgow University, 1998
4 \section[StdIdInfo]{Standard unfoldings}
6 This module contains definitions for the IdInfo for things that
7 have a standard form, namely:
11 * method and superclass selectors
12 * primitive operations
16 mkDictFunId, mkDefaultMethodId,
19 mkDataConId, mkDataConWrapId,
21 mkPrimOpId, mkCCallOpId,
23 -- And some particular Ids; see below for why they are wired in
25 unsafeCoerceId, realWorldPrimId,
26 eRROR_ID, rEC_SEL_ERROR_ID, pAT_ERROR_ID, rEC_CON_ERROR_ID,
27 rEC_UPD_ERROR_ID, iRREFUT_PAT_ERROR_ID, nON_EXHAUSTIVE_GUARDS_ERROR_ID,
28 nO_METHOD_BINDING_ERROR_ID, aBSENT_ERROR_ID, pAR_ERROR_ID
31 #include "HsVersions.h"
34 import BasicTypes ( Arity )
35 import TysPrim ( openAlphaTyVars, alphaTyVar, alphaTy,
36 intPrimTy, realWorldStatePrimTy
38 import TysWiredIn ( charTy, mkListTy )
39 import PrelNames ( pREL_ERR, pREL_GHC )
40 import PrelRules ( primOpRule )
41 import Rules ( addRule )
42 import Type ( Type, ThetaType, mkDictTy, mkPredTys, mkTyConApp, mkTyVarTys,
43 mkFunTys, mkFunTy, mkSigmaTy, splitSigmaTy,
44 isUnLiftedType, mkForAllTys, mkTyVarTy, tyVarsOfType,
45 splitFunTys, splitForAllTys, mkPredTy
47 import Module ( Module )
48 import CoreUtils ( exprType, mkInlineMe )
49 import CoreUnfold ( mkTopUnfolding, mkCompulsoryUnfolding, mkOtherCon )
50 import Literal ( Literal(..) )
51 import TyCon ( TyCon, isNewTyCon, tyConTyVars, tyConDataCons,
52 tyConTheta, isProductTyCon, isDataTyCon )
53 import Class ( Class, classTyCon, classTyVars, classSelIds )
54 import Var ( Id, TyVar )
55 import VarSet ( isEmptyVarSet )
56 import Name ( mkWiredInName, mkCCallName, Name )
57 import OccName ( mkVarOcc )
58 import PrimOp ( PrimOp(DataToTagOp, CCallOp),
59 primOpSig, mkPrimOpIdName,
62 import Demand ( wwStrict, wwPrim, mkStrictnessInfo )
63 import DataCon ( DataCon, StrictnessMark(..),
64 dataConFieldLabels, dataConRepArity, dataConTyCon,
65 dataConArgTys, dataConRepType, dataConRepStrictness,
66 dataConInstOrigArgTys,
67 dataConName, dataConTheta,
68 dataConSig, dataConStrictMarks, dataConId,
69 maybeMarkedUnboxed, splitProductType_maybe
71 import Id ( idType, mkGlobalId, mkVanillaGlobal,
72 mkTemplateLocals, mkTemplateLocalsNum,
73 mkTemplateLocal, idCprInfo
75 import IdInfo ( IdInfo, noCafNoTyGenIdInfo,
76 exactArity, setUnfoldingInfo, setCprInfo,
77 setArityInfo, setSpecInfo, setCgInfo,
78 mkStrictnessInfo, setStrictnessInfo,
79 GlobalIdDetails(..), CafInfo(..), CprInfo(..),
80 CgInfo(..), setCgArity
82 import FieldLabel ( mkFieldLabel, fieldLabelName,
83 firstFieldLabelTag, allFieldLabelTags, fieldLabelType
88 import Maybe ( isJust )
90 import ListSetOps ( assoc, assocMaybe )
91 import UnicodeUtil ( stringToUtf8 )
95 %************************************************************************
97 \subsection{Wired in Ids}
99 %************************************************************************
103 = [ -- These error-y things are wired in because we don't yet have
104 -- a way to express in an interface file that the result type variable
105 -- is 'open'; that is can be unified with an unboxed type
107 -- [The interface file format now carry such information, but there's
108 -- no way yet of expressing at the definition site for these
110 -- functions that they have an 'open' result type. -- sof 1/99]
114 , iRREFUT_PAT_ERROR_ID
115 , nON_EXHAUSTIVE_GUARDS_ERROR_ID
116 , nO_METHOD_BINDING_ERROR_ID
122 -- These three can't be defined in Haskell
129 %************************************************************************
131 \subsection{Data constructors}
133 %************************************************************************
136 mkDataConId :: Name -> DataCon -> Id
137 -- Makes the *worker* for the data constructor; that is, the function
138 -- that takes the reprsentation arguments and builds the constructor.
139 mkDataConId work_name data_con
140 = mkGlobalId (DataConId data_con) work_name (dataConRepType data_con) info
142 info = noCafNoTyGenIdInfo
144 `setArityInfo` exactArity arity
145 `setStrictnessInfo` strict_info
146 `setCprInfo` cpr_info
148 arity = dataConRepArity data_con
150 strict_info = mkStrictnessInfo (dataConRepStrictness data_con, False)
152 tycon = dataConTyCon data_con
153 cpr_info | isProductTyCon tycon &&
156 arity <= mAX_CPR_SIZE = ReturnsCPR
157 | otherwise = NoCPRInfo
158 -- ReturnsCPR is only true for products that are real data types;
159 -- that is, not unboxed tuples or newtypes
161 mAX_CPR_SIZE :: Arity
163 -- We do not treat very big tuples as CPR-ish:
164 -- a) for a start we get into trouble because there aren't
165 -- "enough" unboxed tuple types (a tiresome restriction,
167 -- b) more importantly, big unboxed tuples get returned mainly
168 -- on the stack, and are often then allocated in the heap
169 -- by the caller. So doing CPR for them may in fact make
173 The wrapper for a constructor is an ordinary top-level binding that evaluates
174 any strict args, unboxes any args that are going to be flattened, and calls
177 We're going to build a constructor that looks like:
179 data (Data a, C b) => T a b = T1 !a !Int b
182 \d1::Data a, d2::C b ->
183 \p q r -> case p of { p ->
185 Con T1 [a,b] [p,q,r]}}
189 * d2 is thrown away --- a context in a data decl is used to make sure
190 one *could* construct dictionaries at the site the constructor
191 is used, but the dictionary isn't actually used.
193 * We have to check that we can construct Data dictionaries for
194 the types a and Int. Once we've done that we can throw d1 away too.
196 * We use (case p of q -> ...) to evaluate p, rather than "seq" because
197 all that matters is that the arguments are evaluated. "seq" is
198 very careful to preserve evaluation order, which we don't need
201 You might think that we could simply give constructors some strictness
202 info, like PrimOps, and let CoreToStg do the let-to-case transformation.
203 But we don't do that because in the case of primops and functions strictness
204 is a *property* not a *requirement*. In the case of constructors we need to
205 do something active to evaluate the argument.
207 Making an explicit case expression allows the simplifier to eliminate
208 it in the (common) case where the constructor arg is already evaluated.
211 mkDataConWrapId data_con
214 wrap_id = mkGlobalId (DataConWrapId data_con) (dataConName data_con) wrap_ty info
215 work_id = dataConId data_con
217 info = noCafNoTyGenIdInfo
218 `setUnfoldingInfo` mkTopUnfolding (mkInlineMe wrap_rhs)
219 `setCprInfo` cpr_info
220 -- The Cpr info can be important inside INLINE rhss, where the
221 -- wrapper constructor isn't inlined
223 `setArityInfo` exactArity arity
224 -- It's important to specify the arity, so that partial
225 -- applications are treated as values
227 wrap_ty = mkForAllTys all_tyvars $
231 cpr_info = idCprInfo work_id
233 wrap_rhs | isNewTyCon tycon
234 = ASSERT( null ex_tyvars && null ex_dict_args && length orig_arg_tys == 1 )
235 -- No existentials on a newtype, but it can have a context
236 -- e.g. newtype Eq a => T a = MkT (...)
238 mkLams tyvars $ mkLams dict_args $ Lam id_arg1 $
239 Note (Coerce result_ty (head orig_arg_tys)) (Var id_arg1)
241 | null dict_args && all not_marked_strict strict_marks
242 = Var work_id -- The common case. Not only is this efficient,
243 -- but it also ensures that the wrapper is replaced
244 -- by the worker even when there are no args.
248 -- This is really important in rule matching,
249 -- (We could match on the wrappers,
250 -- but that makes it less likely that rules will match
251 -- when we bring bits of unfoldings together.)
253 -- NB: because of this special case, (map (:) ys) turns into
254 -- (map $w: ys), and thence into (map (\x xs. $w: x xs) ys)
255 -- in core-to-stg. The top-level defn for (:) is never used.
256 -- This is somewhat of a bore, but I'm currently leaving it
257 -- as is, so that there still is a top level curried (:) for
258 -- the interpreter to call.
261 = mkLams all_tyvars $ mkLams dict_args $
262 mkLams ex_dict_args $ mkLams id_args $
263 foldr mk_case con_app
264 (zip (ex_dict_args++id_args) strict_marks) i3 []
266 con_app i rep_ids = mkApps (Var work_id)
267 (map varToCoreExpr (all_tyvars ++ reverse rep_ids))
269 (tyvars, theta, ex_tyvars, ex_theta, orig_arg_tys, tycon) = dataConSig data_con
270 all_tyvars = tyvars ++ ex_tyvars
272 dict_tys = mkPredTys theta
273 ex_dict_tys = mkPredTys ex_theta
274 all_arg_tys = dict_tys ++ ex_dict_tys ++ orig_arg_tys
275 result_ty = mkTyConApp tycon (mkTyVarTys tyvars)
277 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
281 (dict_args, i1) = mkLocals 1 dict_tys
282 (ex_dict_args,i2) = mkLocals i1 ex_dict_tys
283 (id_args,i3) = mkLocals i2 orig_arg_tys
285 (id_arg1:_) = id_args -- Used for newtype only
287 strict_marks = dataConStrictMarks data_con
288 not_marked_strict NotMarkedStrict = True
289 not_marked_strict other = False
293 :: (Id, StrictnessMark) -- arg, strictness
294 -> (Int -> [Id] -> CoreExpr) -- body
295 -> Int -- next rep arg id
296 -> [Id] -- rep args so far
298 mk_case (arg,strict) body i rep_args
300 NotMarkedStrict -> body i (arg:rep_args)
302 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
304 Case (Var arg) arg [(DEFAULT,[], body i (arg:rep_args))]
306 MarkedUnboxed con tys ->
307 Case (Var arg) arg [(DataAlt con, con_args,
308 body i' (reverse con_args++rep_args))]
310 (con_args,i') = mkLocals i tys
314 %************************************************************************
316 \subsection{Record selectors}
318 %************************************************************************
320 We're going to build a record selector unfolding that looks like this:
322 data T a b c = T1 { ..., op :: a, ...}
323 | T2 { ..., op :: a, ...}
326 sel = /\ a b c -> \ d -> case d of
331 Similarly for newtypes
333 newtype N a = MkN { unN :: a->a }
336 unN n = coerce (a->a) n
338 We need to take a little care if the field has a polymorphic type:
340 data R = R { f :: forall a. a->a }
344 f :: forall a. R -> a -> a
345 f = /\ a \ r = case r of
348 (not f :: R -> forall a. a->a, which gives the type inference mechanism
349 problems at call sites)
351 Similarly for newtypes
353 newtype N = MkN { unN :: forall a. a->a }
355 unN :: forall a. N -> a -> a
356 unN = /\a -> \n:N -> coerce (a->a) n
359 mkRecordSelId tycon field_label unpack_id unpackUtf8_id
360 -- Assumes that all fields with the same field label have the same type
362 -- Annoyingly, we have to pass in the unpackCString# Id, because
363 -- we can't conjure it up out of thin air
366 sel_id = mkGlobalId (RecordSelId field_label) (fieldLabelName field_label) selector_ty info
367 field_ty = fieldLabelType field_label
368 data_cons = tyConDataCons tycon
369 tyvars = tyConTyVars tycon -- These scope over the types in
370 -- the FieldLabels of constructors of this type
371 data_ty = mkTyConApp tycon tyvar_tys
372 tyvar_tys = mkTyVarTys tyvars
374 tycon_theta = tyConTheta tycon -- The context on the data decl
375 -- eg data (Eq a, Ord b) => T a b = ...
376 dict_tys = [mkPredTy pred | pred <- tycon_theta,
378 needed_dict pred = or [ pred `elem` (dataConTheta dc)
379 | (DataAlt dc, _, _) <- the_alts]
380 n_dict_tys = length dict_tys
382 (field_tyvars,field_theta,field_tau) = splitSigmaTy field_ty
383 field_dict_tys = map mkPredTy field_theta
384 n_field_dict_tys = length field_dict_tys
385 -- If the field has a universally quantified type we have to
386 -- be a bit careful. Suppose we have
387 -- data R = R { op :: forall a. Foo a => a -> a }
388 -- Then we can't give op the type
389 -- op :: R -> forall a. Foo a => a -> a
390 -- because the typechecker doesn't understand foralls to the
391 -- right of an arrow. The "right" type to give it is
392 -- op :: forall a. Foo a => R -> a -> a
393 -- But then we must generate the right unfolding too:
394 -- op = /\a -> \dfoo -> \ r ->
397 -- Note that this is exactly the type we'd infer from a user defn
400 -- Very tiresomely, the selectors are (unnecessarily!) overloaded over
401 -- just the dictionaries in the types of the constructors that contain
402 -- the relevant field. Urgh.
403 -- NB: this code relies on the fact that DataCons are quantified over
404 -- the identical type variables as their parent TyCon
407 selector_ty = mkForAllTys tyvars $ mkForAllTys field_tyvars $
408 mkFunTys dict_tys $ mkFunTys field_dict_tys $
409 mkFunTy data_ty field_tau
411 arity = 1 + n_dict_tys + n_field_dict_tys
412 info = noCafNoTyGenIdInfo
413 `setCgInfo` (CgInfo arity caf_info)
414 `setArityInfo` exactArity arity
415 `setUnfoldingInfo` unfolding
416 -- ToDo: consider adding further IdInfo
418 unfolding = mkTopUnfolding sel_rhs
420 -- Allocate Ids. We do it a funny way round because field_dict_tys is
421 -- almost always empty. Also note that we use length_tycon_theta
422 -- rather than n_dict_tys, because the latter gives an infinite loop:
423 -- n_dict tys depends on the_alts, which depens on arg_ids, which depends
424 -- on arity, which depends on n_dict tys. Sigh! Mega sigh!
425 field_dict_base = length tycon_theta + 1
426 dict_id_base = field_dict_base + n_field_dict_tys
427 field_base = dict_id_base + 1
428 dict_ids = mkTemplateLocalsNum 1 dict_tys
429 field_dict_ids = mkTemplateLocalsNum field_dict_base field_dict_tys
430 data_id = mkTemplateLocal dict_id_base data_ty
432 alts = map mk_maybe_alt data_cons
433 the_alts = catMaybes alts
435 no_default = all isJust alts -- No default needed
436 default_alt | no_default = []
437 | otherwise = [(DEFAULT, [], error_expr)]
439 -- the default branch may have CAF refs, because it calls recSelError etc.
440 caf_info | no_default = NoCafRefs
441 | otherwise = MayHaveCafRefs
443 sel_rhs = mkLams tyvars $ mkLams field_tyvars $
444 mkLams dict_ids $ mkLams field_dict_ids $
445 Lam data_id $ sel_body
447 sel_body | isNewTyCon tycon = Note (Coerce field_tau data_ty) (Var data_id)
448 | otherwise = Case (Var data_id) data_id (the_alts ++ default_alt)
450 mk_maybe_alt data_con
451 = case maybe_the_arg_id of
453 Just the_arg_id -> Just (DataAlt data_con, real_args, expr)
455 body = mkVarApps (mkVarApps (Var the_arg_id) field_tyvars) field_dict_ids
456 strict_marks = dataConStrictMarks data_con
457 (expr, real_args) = rebuildConArgs data_con arg_ids strict_marks body
460 arg_ids = mkTemplateLocalsNum field_base (dataConInstOrigArgTys data_con tyvar_tys)
461 -- arity+1 avoids all shadowing
462 maybe_the_arg_id = assocMaybe (field_lbls `zip` arg_ids) field_label
463 field_lbls = dataConFieldLabels data_con
465 error_expr = mkApps (Var rEC_SEL_ERROR_ID) [Type field_tau, err_string]
467 | all safeChar full_msg
468 = App (Var unpack_id) (Lit (MachStr (_PK_ full_msg)))
470 = App (Var unpackUtf8_id) (Lit (MachStr (_PK_ (stringToUtf8 (map ord full_msg)))))
472 safeChar c = c >= '\1' && c <= '\xFF'
473 -- TODO: Putting this Unicode stuff here is ugly. Find a better
474 -- generic place to make string literals. This logic is repeated
476 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
479 -- this rather ugly function converts the unpacked data con arguments back into
480 -- their packed form. It is almost the same as the version in DsUtils, except that
481 -- we use template locals here rather than newDsId (ToDo: merge these).
484 :: DataCon -- the con we're matching on
485 -> [Id] -- the source-level args
486 -> [StrictnessMark] -- the strictness annotations (per-arg)
487 -> CoreExpr -- the body
488 -> Int -- template local
491 rebuildConArgs con [] stricts body i = (body, [])
492 rebuildConArgs con (arg:args) stricts body i | isTyVar arg
493 = let (body', args') = rebuildConArgs con args stricts body i
495 rebuildConArgs con (arg:args) (str:stricts) body i
496 = case maybeMarkedUnboxed str of
497 Just (pack_con1, _) ->
498 case splitProductType_maybe (idType arg) of
499 Just (_, tycon_args, pack_con, con_arg_tys) ->
500 ASSERT( pack_con == pack_con1 )
501 let unpacked_args = zipWith mkTemplateLocal [i..] con_arg_tys
502 (body', real_args) = rebuildConArgs con args stricts body
503 (i + length con_arg_tys)
506 Let (NonRec arg (mkConApp pack_con
507 (map Type tycon_args ++
508 map Var unpacked_args))) body',
509 unpacked_args ++ real_args
512 _ -> let (body', args') = rebuildConArgs con args stricts body i
513 in (body', arg:args')
517 %************************************************************************
519 \subsection{Dictionary selectors}
521 %************************************************************************
523 Selecting a field for a dictionary. If there is just one field, then
524 there's nothing to do.
526 ToDo: unify with mkRecordSelId.
529 mkDictSelId :: Name -> Class -> Id
530 mkDictSelId name clas
534 sel_id = mkGlobalId (RecordSelId field_lbl) name ty info
535 field_lbl = mkFieldLabel name tycon ty tag
536 tag = assoc "MkId.mkDictSelId" (classSelIds clas `zip` allFieldLabelTags) sel_id
538 info = noCafNoTyGenIdInfo
540 `setArityInfo` exactArity 1
541 `setUnfoldingInfo` unfolding
543 -- We no longer use 'must-inline' on record selectors. They'll
544 -- inline like crazy if they scrutinise a constructor
546 unfolding = mkTopUnfolding rhs
548 tyvars = classTyVars clas
550 tycon = classTyCon clas
551 [data_con] = tyConDataCons tycon
552 tyvar_tys = mkTyVarTys tyvars
553 arg_tys = dataConArgTys data_con tyvar_tys
554 the_arg_id = arg_ids !! (tag - firstFieldLabelTag)
556 dict_ty = mkDictTy clas tyvar_tys
557 (dict_id:arg_ids) = mkTemplateLocals (dict_ty : arg_tys)
559 rhs | isNewTyCon tycon = mkLams tyvars $ Lam dict_id $
560 Note (Coerce (head arg_tys) dict_ty) (Var dict_id)
561 | otherwise = mkLams tyvars $ Lam dict_id $
562 Case (Var dict_id) dict_id
563 [(DataAlt data_con, arg_ids, Var the_arg_id)]
567 %************************************************************************
569 \subsection{Primitive operations
571 %************************************************************************
574 mkPrimOpId :: PrimOp -> Id
578 (tyvars,arg_tys,res_ty, arity, strict_info) = primOpSig prim_op
579 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
580 name = mkPrimOpIdName prim_op
581 id = mkGlobalId (PrimOpId prim_op) name ty info
583 info = noCafNoTyGenIdInfo
586 `setArityInfo` exactArity arity
587 `setStrictnessInfo` strict_info
589 rules = maybe emptyCoreRules (addRule emptyCoreRules id)
593 -- For each ccall we manufacture a separate CCallOpId, giving it
594 -- a fresh unique, a type that is correct for this particular ccall,
595 -- and a CCall structure that gives the correct details about calling
598 -- The *name* of this Id is a local name whose OccName gives the full
599 -- details of the ccall, type and all. This means that the interface
600 -- file reader can reconstruct a suitable Id
602 mkCCallOpId :: Unique -> CCall -> Type -> Id
603 mkCCallOpId uniq ccall ty
604 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
605 -- A CCallOpId should have no free type variables;
606 -- when doing substitutions won't substitute over it
607 mkGlobalId (PrimOpId prim_op) name ty info
609 occ_str = showSDocIface (braces (pprCCallOp ccall <+> ppr ty))
610 -- The "occurrence name" of a ccall is the full info about the
611 -- ccall; it is encoded, but may have embedded spaces etc!
613 name = mkCCallName uniq occ_str
614 prim_op = CCallOp ccall
616 info = noCafNoTyGenIdInfo
618 `setArityInfo` exactArity arity
619 `setStrictnessInfo` strict_info
621 (_, tau) = splitForAllTys ty
622 (arg_tys, _) = splitFunTys tau
623 arity = length arg_tys
624 strict_info = mkStrictnessInfo (take arity (repeat wwPrim), False)
628 %************************************************************************
630 \subsection{DictFuns and default methods}
632 %************************************************************************
635 mkDefaultMethodId dm_name ty
636 = mkVanillaGlobal dm_name ty noCafNoTyGenIdInfo
638 mkDictFunId :: Name -- Name to use for the dict fun;
645 mkDictFunId dfun_name clas inst_tyvars inst_tys dfun_theta
646 = mkVanillaGlobal dfun_name dfun_ty noCafNoTyGenIdInfo
648 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
650 {- 1 dec 99: disable the Mark Jones optimisation for the sake
651 of compatibility with Hugs.
652 See `types/InstEnv' for a discussion related to this.
654 (class_tyvars, sc_theta, _, _) = classBigSig clas
655 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
656 sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys) sc_theta
657 dfun_theta = case inst_decl_theta of
658 [] -> [] -- If inst_decl_theta is empty, then we don't
659 -- want to have any dict arguments, so that we can
660 -- expose the constant methods.
662 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
663 -- Otherwise we pass the superclass dictionaries to
664 -- the dictionary function; the Mark Jones optimisation.
666 -- NOTE the "nub". I got caught by this one:
667 -- class Monad m => MonadT t m where ...
668 -- instance Monad m => MonadT (EnvT env) m where ...
669 -- Here, the inst_decl_theta has (Monad m); but so
670 -- does the sc_theta'!
672 -- NOTE the "not_const". I got caught by this one too:
673 -- class Foo a => Baz a b where ...
674 -- instance Wob b => Baz T b where..
675 -- Now sc_theta' has Foo T
680 %************************************************************************
682 \subsection{Un-definable}
684 %************************************************************************
686 These two can't be defined in Haskell.
688 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
689 just gets expanded into a type coercion wherever it occurs. Hence we
690 add it as a built-in Id with an unfolding here.
692 The type variables we use here are "open" type variables: this means
693 they can unify with both unlifted and lifted types. Hence we provide
694 another gun with which to shoot yourself in the foot.
698 = pcMiscPrelId unsafeCoerceIdKey pREL_GHC SLIT("unsafeCoerce#") ty info
700 info = noCafNoTyGenIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
703 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
704 (mkFunTy openAlphaTy openBetaTy)
705 [x] = mkTemplateLocals [openAlphaTy]
706 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
707 Note (Coerce openBetaTy openAlphaTy) (Var x)
711 @getTag#@ is another function which can't be defined in Haskell. It needs to
712 evaluate its argument and call the dataToTag# primitive.
716 = pcMiscPrelId getTagIdKey pREL_GHC SLIT("getTag#") ty info
718 info = noCafNoTyGenIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
719 -- We don't provide a defn for this; you must inline it
721 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy intPrimTy)
722 [x,y] = mkTemplateLocals [alphaTy,alphaTy]
723 rhs = mkLams [alphaTyVar,x] $
724 Case (Var x) y [ (DEFAULT, [], mkApps (Var dataToTagId) [Type alphaTy, Var y]) ]
726 dataToTagId = mkPrimOpId DataToTagOp
729 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
730 nasty as-is, change it back to a literal (@Literal@).
733 realWorldPrimId -- :: State# RealWorld
734 = pcMiscPrelId realWorldPrimIdKey pREL_GHC SLIT("realWorld#")
736 (noCafNoTyGenIdInfo `setUnfoldingInfo` mkOtherCon [])
737 -- The mkOtherCon makes it look that realWorld# is evaluated
738 -- which in turn makes Simplify.interestingArg return True,
739 -- which in turn makes INLINE things applied to realWorld# likely
744 %************************************************************************
746 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
748 %************************************************************************
750 GHC randomly injects these into the code.
752 @patError@ is just a version of @error@ for pattern-matching
753 failures. It knows various ``codes'' which expand to longer
754 strings---this saves space!
756 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
757 well shouldn't be yanked on, but if one is, then you will get a
758 friendly message from @absentErr@ (rather than a totally random
761 @parError@ is a special version of @error@ which the compiler does
762 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
763 templates, but we don't ever expect to generate code for it.
767 = pc_bottoming_Id errorIdKey pREL_ERR SLIT("error") errorTy
769 = generic_ERROR_ID patErrorIdKey SLIT("patError")
771 = generic_ERROR_ID recSelErrIdKey SLIT("recSelError")
773 = generic_ERROR_ID recConErrorIdKey SLIT("recConError")
775 = generic_ERROR_ID recUpdErrorIdKey SLIT("recUpdError")
777 = generic_ERROR_ID irrefutPatErrorIdKey SLIT("irrefutPatError")
778 nON_EXHAUSTIVE_GUARDS_ERROR_ID
779 = generic_ERROR_ID nonExhaustiveGuardsErrorIdKey SLIT("nonExhaustiveGuardsError")
780 nO_METHOD_BINDING_ERROR_ID
781 = generic_ERROR_ID noMethodBindingErrorIdKey SLIT("noMethodBindingError")
784 = pc_bottoming_Id absentErrorIdKey pREL_ERR SLIT("absentErr")
785 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy)
788 = pcMiscPrelId parErrorIdKey pREL_ERR SLIT("parError")
789 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy) noCafNoTyGenIdInfo
793 %************************************************************************
795 \subsection{Utilities}
797 %************************************************************************
800 pcMiscPrelId :: Unique{-IdKey-} -> Module -> FAST_STRING -> Type -> IdInfo -> Id
801 pcMiscPrelId key mod str ty info
803 name = mkWiredInName mod (mkVarOcc str) key
804 imp = mkVanillaGlobal name ty info -- the usual case...
807 -- We lie and say the thing is imported; otherwise, we get into
808 -- a mess with dependency analysis; e.g., core2stg may heave in
809 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
810 -- being compiled, then it's just a matter of luck if the definition
811 -- will be in "the right place" to be in scope.
813 pc_bottoming_Id key mod name ty
814 = pcMiscPrelId key mod name ty bottoming_info
816 bottoming_info = noCafNoTyGenIdInfo
817 `setStrictnessInfo` mkStrictnessInfo ([wwStrict], True)
819 -- these "bottom" out, no matter what their arguments
821 generic_ERROR_ID u n = pc_bottoming_Id u pREL_ERR n errorTy
823 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
824 openAlphaTy = mkTyVarTy openAlphaTyVar
825 openBetaTy = mkTyVarTy openBetaTyVar
828 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy]
830 -- Notice the openAlphaTyVar. It says that "error" can be applied
831 -- to unboxed as well as boxed types. This is OK because it never
832 -- returns, so the return type is irrelevant.