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 mkSpecPragmaId, mkWorkerId,
18 mkDictFunId, mkDefaultMethodId,
21 mkDataConId, mkDataConWrapId,
23 mkPrimOpId, mkCCallOpId,
25 -- And some particular Ids; see below for why they are wired in
27 unsafeCoerceId, realWorldPrimId,
28 eRROR_ID, rEC_SEL_ERROR_ID, pAT_ERROR_ID, rEC_CON_ERROR_ID,
29 rEC_UPD_ERROR_ID, iRREFUT_PAT_ERROR_ID, nON_EXHAUSTIVE_GUARDS_ERROR_ID,
30 nO_METHOD_BINDING_ERROR_ID, aBSENT_ERROR_ID, pAR_ERROR_ID
33 #include "HsVersions.h"
36 import TysPrim ( openAlphaTyVars, alphaTyVar, alphaTy,
37 intPrimTy, realWorldStatePrimTy
39 import TysWiredIn ( boolTy, charTy, mkListTy )
40 import PrelNames ( pREL_ERR, pREL_GHC )
41 import PrelRules ( primOpRule )
42 import Rules ( addRule )
43 import Type ( Type, ThetaType, mkDictTy, mkDictTys, mkTyConApp, mkTyVarTys,
44 mkFunTys, mkFunTy, mkSigmaTy, classesToPreds,
45 isUnLiftedType, mkForAllTys, mkTyVarTy, tyVarsOfType, tyVarsOfTypes,
46 splitSigmaTy, splitFunTy_maybe,
47 splitFunTys, splitForAllTys, unUsgTy,
50 import Module ( Module )
51 import CoreUtils ( exprType, mkInlineMe )
52 import CoreUnfold ( mkTopUnfolding, mkCompulsoryUnfolding, mkOtherCon )
53 import Literal ( Literal(..) )
54 import TyCon ( TyCon, isNewTyCon, tyConTyVars, tyConDataCons, isDataTyCon,
55 tyConTheta, isProductTyCon, isUnboxedTupleTyCon )
56 import Class ( Class, classBigSig, classTyCon, classTyVars, classSelIds )
57 import Var ( Id, TyVar )
58 import VarSet ( isEmptyVarSet )
59 import Name ( mkDerivedName, mkWiredInIdName, mkLocalName,
60 mkWorkerOcc, mkSuperDictSelOcc, mkCCallName,
63 import OccName ( mkSrcVarOcc )
64 import PrimOp ( PrimOp(DataToTagOp, CCallOp),
65 primOpSig, mkPrimOpIdName,
68 import Demand ( wwStrict, wwPrim, mkStrictnessInfo )
69 import DataCon ( DataCon, StrictnessMark(..),
70 dataConFieldLabels, dataConRepArity, dataConTyCon,
71 dataConArgTys, dataConRepType, dataConRepStrictness,
72 dataConInstOrigArgTys,
73 dataConName, dataConTheta,
74 dataConSig, dataConStrictMarks, dataConId,
75 maybeMarkedUnboxed, splitProductType_maybe
77 import Id ( idType, mkId,
78 mkVanillaId, mkTemplateLocals,
79 mkTemplateLocal, setInlinePragma, idCprInfo
81 import IdInfo ( IdInfo, vanillaIdInfo, mkIdInfo,
82 exactArity, setUnfoldingInfo, setCafInfo, setCprInfo,
83 setArityInfo, setInlinePragInfo, setSpecInfo,
84 mkStrictnessInfo, setStrictnessInfo,
85 IdFlavour(..), InlinePragInfo(..), CafInfo(..), StrictnessInfo(..), CprInfo(..)
87 import FieldLabel ( FieldLabel, FieldLabelTag, mkFieldLabel, fieldLabelName,
88 firstFieldLabelTag, allFieldLabelTags, fieldLabelType
93 import Maybe ( isJust )
95 import ListSetOps ( assoc, assocMaybe )
96 import UnicodeUtil ( stringToUtf8 )
101 %************************************************************************
103 \subsection{Wired in Ids}
105 %************************************************************************
109 = [ -- These error-y things are wired in because we don't yet have
110 -- a way to express in an interface file that the result type variable
111 -- is 'open'; that is can be unified with an unboxed type
113 -- [The interface file format now carry such information, but there's
114 -- no way yet of expressing at the definition site for these
116 -- functions that they have an 'open' result type. -- sof 1/99]
120 , iRREFUT_PAT_ERROR_ID
121 , nON_EXHAUSTIVE_GUARDS_ERROR_ID
122 , nO_METHOD_BINDING_ERROR_ID
128 -- These two can't be defined in Haskell
135 %************************************************************************
137 \subsection{Easy ones}
139 %************************************************************************
142 mkSpecPragmaId occ uniq ty loc
143 = mkId (mkLocalName uniq occ loc) ty (mkIdInfo SpecPragmaId)
144 -- Maybe a SysLocal? But then we'd lose the location
146 mkDefaultMethodId dm_name rec_c ty
147 = mkVanillaId dm_name ty
149 mkWorkerId uniq unwrkr ty
150 = mkVanillaId (mkDerivedName mkWorkerOcc (getName unwrkr) uniq) ty
153 %************************************************************************
155 \subsection{Data constructors}
157 %************************************************************************
160 mkDataConId :: Name -> DataCon -> Id
161 -- Makes the *worker* for the data constructor; that is, the function
162 -- that takes the reprsentation arguments and builds the constructor.
163 mkDataConId work_name data_con
164 = mkId work_name (dataConRepType data_con) info
166 info = mkIdInfo (DataConId data_con)
167 `setArityInfo` exactArity arity
168 `setStrictnessInfo` strict_info
169 `setCprInfo` cpr_info
171 arity = dataConRepArity data_con
173 strict_info = mkStrictnessInfo (dataConRepStrictness data_con, False)
175 cpr_info | isProductTyCon tycon &&
176 not (isUnboxedTupleTyCon tycon) &&
177 arity > 0 = ReturnsCPR
178 | otherwise = NoCPRInfo
180 tycon = dataConTyCon data_con
181 -- Newtypes don't have a worker at all
183 -- If we are a product with 0 args we must be void(like)
184 -- We can't create an unboxed tuple with 0 args for this
185 -- and since Void has only one, constant value it should
186 -- just mean returning a pointer to a pre-existing cell.
187 -- So we won't really gain from doing anything fancy
188 -- and we treat this case as Top.
191 The wrapper for a constructor is an ordinary top-level binding that evaluates
192 any strict args, unboxes any args that are going to be flattened, and calls
195 We're going to build a constructor that looks like:
197 data (Data a, C b) => T a b = T1 !a !Int b
200 \d1::Data a, d2::C b ->
201 \p q r -> case p of { p ->
203 Con T1 [a,b] [p,q,r]}}
207 * d2 is thrown away --- a context in a data decl is used to make sure
208 one *could* construct dictionaries at the site the constructor
209 is used, but the dictionary isn't actually used.
211 * We have to check that we can construct Data dictionaries for
212 the types a and Int. Once we've done that we can throw d1 away too.
214 * We use (case p of q -> ...) to evaluate p, rather than "seq" because
215 all that matters is that the arguments are evaluated. "seq" is
216 very careful to preserve evaluation order, which we don't need
219 You might think that we could simply give constructors some strictness
220 info, like PrimOps, and let CoreToStg do the let-to-case transformation.
221 But we don't do that because in the case of primops and functions strictness
222 is a *property* not a *requirement*. In the case of constructors we need to
223 do something active to evaluate the argument.
225 Making an explicit case expression allows the simplifier to eliminate
226 it in the (common) case where the constructor arg is already evaluated.
229 mkDataConWrapId data_con
232 wrap_id = mkId (dataConName data_con) wrap_ty info
233 work_id = dataConId data_con
235 info = mkIdInfo (DataConWrapId data_con)
236 `setUnfoldingInfo` mkTopUnfolding (mkInlineMe wrap_rhs)
237 `setCprInfo` cpr_info
238 -- The Cpr info can be important inside INLINE rhss, where the
239 -- wrapper constructor isn't inlined
240 `setArityInfo` exactArity arity
241 -- It's important to specify the arity, so that partial
242 -- applications are treated as values
243 `setCafInfo` NoCafRefs
244 -- The wrapper Id ends up in STG code as an argument,
245 -- sometimes before its definition, so we want to
246 -- signal that it has no CAFs
248 wrap_ty = mkForAllTys all_tyvars $
252 cpr_info = idCprInfo work_id
254 wrap_rhs | isNewTyCon tycon
255 = ASSERT( null ex_tyvars && null ex_dict_args && length orig_arg_tys == 1 )
256 -- No existentials on a newtype, but it can have a context
257 -- e.g. newtype Eq a => T a = MkT (...)
259 mkLams tyvars $ mkLams dict_args $ Lam id_arg1 $
260 Note (Coerce result_ty (head orig_arg_tys)) (Var id_arg1)
262 | null dict_args && all not_marked_strict strict_marks
263 = Var work_id -- The common case. Not only is this efficient,
264 -- but it also ensures that the wrapper is replaced
265 -- by the worker even when there are no args.
269 -- This is really important in rule matching,
270 -- (We could match on the wrappers,
271 -- but that makes it less likely that rules will match
272 -- when we bring bits of unfoldings together.)
274 -- NB: because of this special case, (map (:) ys) turns into
275 -- (map $w: ys), and thence into (map (\x xs. $w: x xs) ys)
276 -- in core-to-stg. The top-level defn for (:) is never used.
277 -- This is somewhat of a bore, but I'm currently leaving it
278 -- as is, so that there still is a top level curried (:) for
279 -- the interpreter to call.
282 = mkLams all_tyvars $ mkLams dict_args $
283 mkLams ex_dict_args $ mkLams id_args $
284 foldr mk_case con_app
285 (zip (ex_dict_args++id_args) strict_marks) i3 []
287 con_app i rep_ids = mkApps (Var work_id)
288 (map varToCoreExpr (all_tyvars ++ reverse rep_ids))
290 (tyvars, theta, ex_tyvars, ex_theta, orig_arg_tys, tycon) = dataConSig data_con
291 all_tyvars = tyvars ++ ex_tyvars
293 dict_tys = mkDictTys theta
294 ex_dict_tys = mkDictTys ex_theta
295 all_arg_tys = dict_tys ++ ex_dict_tys ++ orig_arg_tys
296 result_ty = mkTyConApp tycon (mkTyVarTys tyvars)
298 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
302 (dict_args, i1) = mkLocals 1 dict_tys
303 (ex_dict_args,i2) = mkLocals i1 ex_dict_tys
304 (id_args,i3) = mkLocals i2 orig_arg_tys
306 (id_arg1:_) = id_args -- Used for newtype only
308 strict_marks = dataConStrictMarks data_con
309 not_marked_strict NotMarkedStrict = True
310 not_marked_strict other = False
314 :: (Id, StrictnessMark) -- arg, strictness
315 -> (Int -> [Id] -> CoreExpr) -- body
316 -> Int -- next rep arg id
317 -> [Id] -- rep args so far
319 mk_case (arg,strict) body i rep_args
321 NotMarkedStrict -> body i (arg:rep_args)
323 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
325 Case (Var arg) arg [(DEFAULT,[], body i (arg:rep_args))]
327 MarkedUnboxed con tys ->
328 Case (Var arg) arg [(DataAlt con, con_args,
329 body i' (reverse con_args++rep_args))]
331 (con_args,i') = mkLocals i tys
335 %************************************************************************
337 \subsection{Record selectors}
339 %************************************************************************
341 We're going to build a record selector unfolding that looks like this:
343 data T a b c = T1 { ..., op :: a, ...}
344 | T2 { ..., op :: a, ...}
347 sel = /\ a b c -> \ d -> case d of
352 Similarly for newtypes
354 newtype N a = MkN { unN :: a->a }
357 unN n = coerce (a->a) n
359 We need to take a little care if the field has a polymorphic type:
361 data R = R { f :: forall a. a->a }
365 f :: forall a. R -> a -> a
366 f = /\ a \ r = case r of
369 (not f :: R -> forall a. a->a, which gives the type inference mechanism
370 problems at call sites)
372 Similarly for newtypes
374 newtype N = MkN { unN :: forall a. a->a }
376 unN :: forall a. N -> a -> a
377 unN = /\a -> \n:N -> coerce (a->a) n
380 mkRecordSelId tycon field_label unpack_id unpackUtf8_id
381 -- Assumes that all fields with the same field label have the same type
383 -- Annoyingly, we have to pass in the unpackCString# Id, because
384 -- we can't conjure it up out of thin air
387 sel_id = mkId (fieldLabelName field_label) selector_ty info
389 field_ty = fieldLabelType field_label
390 data_cons = tyConDataCons tycon
391 tyvars = tyConTyVars tycon -- These scope over the types in
392 -- the FieldLabels of constructors of this type
393 tycon_theta = tyConTheta tycon -- The context on the data decl
394 -- eg data (Eq a, Ord b) => T a b = ...
395 (field_tyvars,field_tau) = splitForAllTys field_ty
397 data_ty = mkTyConApp tycon tyvar_tys
398 tyvar_tys = mkTyVarTys tyvars
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
405 dict_tys = [mkDictTy cls tys | (cls, tys) <- tycon_theta, needed_dict (cls, tys)]
406 needed_dict pred = or [ pred `elem` (dataConTheta dc)
407 | (DataAlt dc, _, _) <- the_alts]
410 selector_ty = mkForAllTys tyvars $ mkForAllTys field_tyvars $
411 mkFunTys dict_tys $ mkFunTy data_ty field_tau
413 info = mkIdInfo (RecordSelId field_label)
414 `setArityInfo` exactArity (1 + length dict_tys)
415 `setUnfoldingInfo` unfolding
416 `setCafInfo` NoCafRefs
417 -- ToDo: consider adding further IdInfo
419 unfolding = mkTopUnfolding sel_rhs
422 (data_id:dict_ids) = mkTemplateLocals (data_ty:dict_tys)
423 alts = map mk_maybe_alt data_cons
424 the_alts = catMaybes alts
425 default_alt | all isJust alts = [] -- No default needed
426 | otherwise = [(DEFAULT, [], error_expr)]
428 sel_rhs = mkLams tyvars $ mkLams field_tyvars $
429 mkLams dict_ids $ Lam data_id $
432 sel_body | isNewTyCon tycon = Note (Coerce (unUsgTy field_tau) (unUsgTy data_ty)) (Var data_id)
433 | otherwise = Case (Var data_id) data_id (the_alts ++ default_alt)
435 mk_maybe_alt data_con
436 = case maybe_the_arg_id of
438 Just the_arg_id -> Just (DataAlt data_con, real_args, expr)
440 body = mkVarApps (Var the_arg_id) field_tyvars
441 strict_marks = dataConStrictMarks data_con
442 (expr, real_args) = rebuildConArgs data_con arg_ids strict_marks body
445 arg_ids = mkTemplateLocals (dataConInstOrigArgTys data_con tyvar_tys)
446 -- The first one will shadow data_id, but who cares
447 maybe_the_arg_id = assocMaybe (field_lbls `zip` arg_ids) field_label
448 field_lbls = dataConFieldLabels data_con
450 error_expr = mkApps (Var rEC_SEL_ERROR_ID) [Type (unUsgTy field_tau), err_string]
451 -- preserves invariant that type args are *not* usage-annotated on top. KSW 1999-04.
453 | all safeChar full_msg
454 = App (Var unpack_id) (Lit (MachStr (_PK_ full_msg)))
456 = App (Var unpackUtf8_id) (Lit (MachStr (_PK_ (stringToUtf8 (map ord full_msg)))))
458 safeChar c = c >= '\1' && c <= '\xFF'
459 -- TODO: Putting this Unicode stuff here is ugly. Find a better
460 -- generic place to make string literals. This logic is repeated
462 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
465 -- this rather ugly function converts the unpacked data con arguments back into
466 -- their packed form. It is almost the same as the version in DsUtils, except that
467 -- we use template locals here rather than newDsId (ToDo: merge these).
470 :: DataCon -- the con we're matching on
471 -> [Id] -- the source-level args
472 -> [StrictnessMark] -- the strictness annotations (per-arg)
473 -> CoreExpr -- the body
474 -> Int -- template local
477 rebuildConArgs con [] stricts body i = (body, [])
478 rebuildConArgs con (arg:args) stricts body i | isTyVar arg
479 = let (body', args') = rebuildConArgs con args stricts body i
481 rebuildConArgs con (arg:args) (str:stricts) body i
482 = case maybeMarkedUnboxed str of
483 Just (pack_con1, _) ->
484 case splitProductType_maybe (idType arg) of
485 Just (_, tycon_args, pack_con, con_arg_tys) ->
486 ASSERT( pack_con == pack_con1 )
487 let unpacked_args = zipWith mkTemplateLocal [i..] con_arg_tys
488 (body', real_args) = rebuildConArgs con args stricts body
489 (i + length con_arg_tys)
492 Let (NonRec arg (mkConApp pack_con
493 (map Type tycon_args ++
494 map Var unpacked_args))) body',
495 unpacked_args ++ real_args
498 _ -> let (body', args') = rebuildConArgs con args stricts body i
499 in (body', arg:args')
503 %************************************************************************
505 \subsection{Dictionary selectors}
507 %************************************************************************
509 Selecting a field for a dictionary. If there is just one field, then
510 there's nothing to do.
512 ToDo: unify with mkRecordSelId.
515 mkDictSelId :: Name -> Class -> Id
516 mkDictSelId name clas
520 sel_id = mkId name ty info
521 field_lbl = mkFieldLabel name tycon ty tag
522 tag = assoc "MkId.mkDictSelId" (classSelIds clas `zip` allFieldLabelTags) sel_id
524 info = mkIdInfo (RecordSelId field_lbl)
525 `setArityInfo` exactArity 1
526 `setUnfoldingInfo` unfolding
527 `setCafInfo` NoCafRefs
529 -- We no longer use 'must-inline' on record selectors. They'll
530 -- inline like crazy if they scrutinise a constructor
532 unfolding = mkTopUnfolding rhs
534 tyvars = classTyVars clas
536 tycon = classTyCon clas
537 [data_con] = tyConDataCons tycon
538 tyvar_tys = mkTyVarTys tyvars
539 arg_tys = dataConArgTys data_con tyvar_tys
540 the_arg_id = arg_ids !! (tag - firstFieldLabelTag)
542 dict_ty = mkDictTy clas tyvar_tys
543 (dict_id:arg_ids) = mkTemplateLocals (dict_ty : arg_tys)
545 rhs | isNewTyCon tycon = mkLams tyvars $ Lam dict_id $
546 Note (Coerce (head arg_tys) dict_ty) (Var dict_id)
547 | otherwise = mkLams tyvars $ Lam dict_id $
548 Case (Var dict_id) dict_id
549 [(DataAlt data_con, arg_ids, Var the_arg_id)]
553 %************************************************************************
555 \subsection{Primitive operations
557 %************************************************************************
560 mkPrimOpId :: PrimOp -> Id
564 (tyvars,arg_tys,res_ty, arity, strict_info) = primOpSig prim_op
565 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
566 name = mkPrimOpIdName prim_op id
567 id = mkId name ty info
569 info = mkIdInfo (PrimOpId prim_op)
571 `setArityInfo` exactArity arity
572 `setStrictnessInfo` strict_info
574 rules = addRule id emptyCoreRules (primOpRule prim_op)
577 -- For each ccall we manufacture a separate CCallOpId, giving it
578 -- a fresh unique, a type that is correct for this particular ccall,
579 -- and a CCall structure that gives the correct details about calling
582 -- The *name* of this Id is a local name whose OccName gives the full
583 -- details of the ccall, type and all. This means that the interface
584 -- file reader can reconstruct a suitable Id
586 mkCCallOpId :: Unique -> CCall -> Type -> Id
587 mkCCallOpId uniq ccall ty
588 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
589 -- A CCallOpId should have no free type variables;
590 -- when doing substitutions won't substitute over it
593 occ_str = showSDocIface (braces (pprCCallOp ccall <+> ppr ty))
594 -- The "occurrence name" of a ccall is the full info about the
595 -- ccall; it is encoded, but may have embedded spaces etc!
597 name = mkCCallName uniq occ_str
598 prim_op = CCallOp ccall
600 info = mkIdInfo (PrimOpId prim_op)
601 `setArityInfo` exactArity arity
602 `setStrictnessInfo` strict_info
604 (_, tau) = splitForAllTys ty
605 (arg_tys, _) = splitFunTys tau
606 arity = length arg_tys
607 strict_info = mkStrictnessInfo (take arity (repeat wwPrim), False)
611 %************************************************************************
613 \subsection{DictFuns}
615 %************************************************************************
618 mkDictFunId :: Name -- Name to use for the dict fun;
625 mkDictFunId dfun_name clas inst_tyvars inst_tys dfun_theta
626 = mkVanillaId dfun_name dfun_ty
628 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
630 {- 1 dec 99: disable the Mark Jones optimisation for the sake
631 of compatibility with Hugs.
632 See `types/InstEnv' for a discussion related to this.
634 (class_tyvars, sc_theta, _, _) = classBigSig clas
635 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
636 sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys) sc_theta
637 dfun_theta = case inst_decl_theta of
638 [] -> [] -- If inst_decl_theta is empty, then we don't
639 -- want to have any dict arguments, so that we can
640 -- expose the constant methods.
642 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
643 -- Otherwise we pass the superclass dictionaries to
644 -- the dictionary function; the Mark Jones optimisation.
646 -- NOTE the "nub". I got caught by this one:
647 -- class Monad m => MonadT t m where ...
648 -- instance Monad m => MonadT (EnvT env) m where ...
649 -- Here, the inst_decl_theta has (Monad m); but so
650 -- does the sc_theta'!
652 -- NOTE the "not_const". I got caught by this one too:
653 -- class Foo a => Baz a b where ...
654 -- instance Wob b => Baz T b where..
655 -- Now sc_theta' has Foo T
660 %************************************************************************
662 \subsection{Un-definable}
664 %************************************************************************
666 These two can't be defined in Haskell.
668 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
669 just gets expanded into a type coercion wherever it occurs. Hence we
670 add it as a built-in Id with an unfolding here.
672 The type variables we use here are "open" type variables: this means
673 they can unify with both unlifted and lifted types. Hence we provide
674 another gun with which to shoot yourself in the foot.
678 = pcMiscPrelId unsafeCoerceIdKey pREL_GHC SLIT("unsafeCoerce#") ty info
681 `setUnfoldingInfo` mkCompulsoryUnfolding rhs
684 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
685 (mkFunTy openAlphaTy openBetaTy)
686 [x] = mkTemplateLocals [openAlphaTy]
687 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
688 Note (Coerce openBetaTy openAlphaTy) (Var x)
692 @getTag#@ is another function which can't be defined in Haskell. It needs to
693 evaluate its argument and call the dataToTag# primitive.
697 = pcMiscPrelId getTagIdKey pREL_GHC SLIT("getTag#") ty info
700 `setUnfoldingInfo` mkCompulsoryUnfolding rhs
701 -- We don't provide a defn for this; you must inline it
703 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy intPrimTy)
704 [x,y] = mkTemplateLocals [alphaTy,alphaTy]
705 rhs = mkLams [alphaTyVar,x] $
706 Case (Var x) y [ (DEFAULT, [], mkApps (Var dataToTagId) [Type alphaTy, Var y]) ]
708 dataToTagId = mkPrimOpId DataToTagOp
711 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
712 nasty as-is, change it back to a literal (@Literal@).
715 realWorldPrimId -- :: State# RealWorld
716 = pcMiscPrelId realWorldPrimIdKey pREL_GHC SLIT("realWorld#")
718 (noCafIdInfo `setUnfoldingInfo` mkOtherCon [])
719 -- The mkOtherCon makes it look that realWorld# is evaluated
720 -- which in turn makes Simplify.interestingArg return True,
721 -- which in turn makes INLINE things applied to realWorld# likely
726 %************************************************************************
728 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
730 %************************************************************************
732 GHC randomly injects these into the code.
734 @patError@ is just a version of @error@ for pattern-matching
735 failures. It knows various ``codes'' which expand to longer
736 strings---this saves space!
738 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
739 well shouldn't be yanked on, but if one is, then you will get a
740 friendly message from @absentErr@ (rather than a totally random
743 @parError@ is a special version of @error@ which the compiler does
744 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
745 templates, but we don't ever expect to generate code for it.
749 = pc_bottoming_Id errorIdKey pREL_ERR SLIT("error") errorTy
751 = generic_ERROR_ID patErrorIdKey SLIT("patError")
753 = generic_ERROR_ID recSelErrIdKey SLIT("recSelError")
755 = generic_ERROR_ID recConErrorIdKey SLIT("recConError")
757 = generic_ERROR_ID recUpdErrorIdKey SLIT("recUpdError")
759 = generic_ERROR_ID irrefutPatErrorIdKey SLIT("irrefutPatError")
760 nON_EXHAUSTIVE_GUARDS_ERROR_ID
761 = generic_ERROR_ID nonExhaustiveGuardsErrorIdKey SLIT("nonExhaustiveGuardsError")
762 nO_METHOD_BINDING_ERROR_ID
763 = generic_ERROR_ID noMethodBindingErrorIdKey SLIT("noMethodBindingError")
766 = pc_bottoming_Id absentErrorIdKey pREL_ERR SLIT("absentErr")
767 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy)
770 = pcMiscPrelId parErrorIdKey pREL_ERR SLIT("parError")
771 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy) noCafIdInfo
776 %************************************************************************
778 \subsection{Utilities}
780 %************************************************************************
783 pcMiscPrelId :: Unique{-IdKey-} -> Module -> FAST_STRING -> Type -> IdInfo -> Id
784 pcMiscPrelId key mod str ty info
786 name = mkWiredInIdName key mod (mkSrcVarOcc str) imp
787 imp = mkId name ty info -- the usual case...
790 -- We lie and say the thing is imported; otherwise, we get into
791 -- a mess with dependency analysis; e.g., core2stg may heave in
792 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
793 -- being compiled, then it's just a matter of luck if the definition
794 -- will be in "the right place" to be in scope.
796 pc_bottoming_Id key mod name ty
797 = pcMiscPrelId key mod name ty bottoming_info
799 bottoming_info = noCafIdInfo
800 `setStrictnessInfo` mkStrictnessInfo ([wwStrict], True)
802 -- these "bottom" out, no matter what their arguments
804 generic_ERROR_ID u n = pc_bottoming_Id u pREL_ERR n errorTy
807 noCafIdInfo = vanillaIdInfo `setCafInfo` NoCafRefs
809 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
810 openAlphaTy = mkTyVarTy openAlphaTyVar
811 openBetaTy = mkTyVarTy openBetaTyVar
814 errorTy = mkUsgTy UsMany $
815 mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkUsgTy UsOnce (mkListTy charTy)]
816 (mkUsgTy UsMany openAlphaTy))
817 -- Notice the openAlphaTyVar. It says that "error" can be applied
818 -- to unboxed as well as boxed types. This is OK because it never
819 -- returns, so the return type is irrelevant.