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 TysPrim ( openAlphaTyVars, alphaTyVar, alphaTy,
35 intPrimTy, realWorldStatePrimTy
37 import TysWiredIn ( charTy, mkListTy )
38 import PrelNames ( pREL_ERR, pREL_GHC )
39 import PrelRules ( primOpRule )
40 import Rules ( addRule )
41 import Type ( Type, ThetaType, mkDictTy, mkPredTys, mkTyConApp, mkTyVarTys,
42 mkFunTys, mkFunTy, mkSigmaTy, splitSigmaTy,
43 isUnLiftedType, mkForAllTys, mkTyVarTy, tyVarsOfType,
44 splitFunTys, splitForAllTys, mkPredTy
46 import Module ( Module )
47 import CoreUtils ( exprType, mkInlineMe )
48 import CoreUnfold ( mkTopUnfolding, mkCompulsoryUnfolding, mkOtherCon )
49 import Literal ( Literal(..) )
50 import TyCon ( TyCon, isNewTyCon, tyConTyVars, tyConDataCons,
51 tyConTheta, isProductTyCon, isDataTyCon )
52 import Class ( Class, classTyCon, classTyVars, classSelIds )
53 import Var ( Id, TyVar )
54 import VarSet ( isEmptyVarSet )
55 import Name ( mkWiredInName, mkCCallName, Name )
56 import OccName ( mkVarOcc )
57 import PrimOp ( PrimOp(DataToTagOp, CCallOp),
58 primOpSig, mkPrimOpIdName,
61 import Demand ( wwStrict, wwPrim, mkStrictnessInfo )
62 import DataCon ( DataCon, StrictnessMark(..),
63 dataConFieldLabels, dataConRepArity, dataConTyCon,
64 dataConArgTys, dataConRepType, dataConRepStrictness,
65 dataConInstOrigArgTys,
66 dataConName, dataConTheta,
67 dataConSig, dataConStrictMarks, dataConId,
68 maybeMarkedUnboxed, splitProductType_maybe
70 import Id ( idType, mkGlobalId, mkVanillaGlobal,
71 mkTemplateLocals, mkTemplateLocalsNum,
72 mkTemplateLocal, idCprInfo
74 import IdInfo ( IdInfo, noCafNoTyGenIdInfo,
75 exactArity, setUnfoldingInfo, setCprInfo,
76 setArityInfo, setSpecInfo, setCgInfo,
77 mkStrictnessInfo, setStrictnessInfo,
78 GlobalIdDetails(..), CafInfo(..), CprInfo(..),
79 CgInfo(..), setCgArity
81 import FieldLabel ( mkFieldLabel, fieldLabelName,
82 firstFieldLabelTag, allFieldLabelTags, fieldLabelType
87 import Maybe ( isJust )
89 import ListSetOps ( assoc, assocMaybe )
90 import UnicodeUtil ( stringToUtf8 )
94 %************************************************************************
96 \subsection{Wired in Ids}
98 %************************************************************************
102 = [ -- These error-y things are wired in because we don't yet have
103 -- a way to express in an interface file that the result type variable
104 -- is 'open'; that is can be unified with an unboxed type
106 -- [The interface file format now carry such information, but there's
107 -- no way yet of expressing at the definition site for these
109 -- functions that they have an 'open' result type. -- sof 1/99]
113 , iRREFUT_PAT_ERROR_ID
114 , nON_EXHAUSTIVE_GUARDS_ERROR_ID
115 , nO_METHOD_BINDING_ERROR_ID
121 -- These two can't be defined in Haskell
128 %************************************************************************
130 \subsection{Data constructors}
132 %************************************************************************
135 mkDataConId :: Name -> DataCon -> Id
136 -- Makes the *worker* for the data constructor; that is, the function
137 -- that takes the reprsentation arguments and builds the constructor.
138 mkDataConId work_name data_con
139 = mkGlobalId (DataConId data_con) work_name (dataConRepType data_con) info
141 info = noCafNoTyGenIdInfo
143 `setArityInfo` exactArity arity
144 `setStrictnessInfo` strict_info
145 `setCprInfo` cpr_info
147 arity = dataConRepArity data_con
149 strict_info = mkStrictnessInfo (dataConRepStrictness data_con, False)
151 tycon = dataConTyCon data_con
152 cpr_info | isProductTyCon tycon &&
154 arity > 0 = ReturnsCPR
155 | otherwise = NoCPRInfo
156 -- ReturnsCPR is only true for products that are real data types;
157 -- that is, not unboxed tuples or newtypes
160 The wrapper for a constructor is an ordinary top-level binding that evaluates
161 any strict args, unboxes any args that are going to be flattened, and calls
164 We're going to build a constructor that looks like:
166 data (Data a, C b) => T a b = T1 !a !Int b
169 \d1::Data a, d2::C b ->
170 \p q r -> case p of { p ->
172 Con T1 [a,b] [p,q,r]}}
176 * d2 is thrown away --- a context in a data decl is used to make sure
177 one *could* construct dictionaries at the site the constructor
178 is used, but the dictionary isn't actually used.
180 * We have to check that we can construct Data dictionaries for
181 the types a and Int. Once we've done that we can throw d1 away too.
183 * We use (case p of q -> ...) to evaluate p, rather than "seq" because
184 all that matters is that the arguments are evaluated. "seq" is
185 very careful to preserve evaluation order, which we don't need
188 You might think that we could simply give constructors some strictness
189 info, like PrimOps, and let CoreToStg do the let-to-case transformation.
190 But we don't do that because in the case of primops and functions strictness
191 is a *property* not a *requirement*. In the case of constructors we need to
192 do something active to evaluate the argument.
194 Making an explicit case expression allows the simplifier to eliminate
195 it in the (common) case where the constructor arg is already evaluated.
198 mkDataConWrapId data_con
201 wrap_id = mkGlobalId (DataConWrapId data_con) (dataConName data_con) wrap_ty info
202 work_id = dataConId data_con
204 info = noCafNoTyGenIdInfo
205 `setUnfoldingInfo` mkTopUnfolding (mkInlineMe wrap_rhs)
206 `setCprInfo` cpr_info
207 -- The Cpr info can be important inside INLINE rhss, where the
208 -- wrapper constructor isn't inlined
210 `setArityInfo` exactArity arity
211 -- It's important to specify the arity, so that partial
212 -- applications are treated as values
214 wrap_ty = mkForAllTys all_tyvars $
218 cpr_info = idCprInfo work_id
220 wrap_rhs | isNewTyCon tycon
221 = ASSERT( null ex_tyvars && null ex_dict_args && length orig_arg_tys == 1 )
222 -- No existentials on a newtype, but it can have a context
223 -- e.g. newtype Eq a => T a = MkT (...)
225 mkLams tyvars $ mkLams dict_args $ Lam id_arg1 $
226 Note (Coerce result_ty (head orig_arg_tys)) (Var id_arg1)
228 | null dict_args && all not_marked_strict strict_marks
229 = Var work_id -- The common case. Not only is this efficient,
230 -- but it also ensures that the wrapper is replaced
231 -- by the worker even when there are no args.
235 -- This is really important in rule matching,
236 -- (We could match on the wrappers,
237 -- but that makes it less likely that rules will match
238 -- when we bring bits of unfoldings together.)
240 -- NB: because of this special case, (map (:) ys) turns into
241 -- (map $w: ys), and thence into (map (\x xs. $w: x xs) ys)
242 -- in core-to-stg. The top-level defn for (:) is never used.
243 -- This is somewhat of a bore, but I'm currently leaving it
244 -- as is, so that there still is a top level curried (:) for
245 -- the interpreter to call.
248 = mkLams all_tyvars $ mkLams dict_args $
249 mkLams ex_dict_args $ mkLams id_args $
250 foldr mk_case con_app
251 (zip (ex_dict_args++id_args) strict_marks) i3 []
253 con_app i rep_ids = mkApps (Var work_id)
254 (map varToCoreExpr (all_tyvars ++ reverse rep_ids))
256 (tyvars, theta, ex_tyvars, ex_theta, orig_arg_tys, tycon) = dataConSig data_con
257 all_tyvars = tyvars ++ ex_tyvars
259 dict_tys = mkPredTys theta
260 ex_dict_tys = mkPredTys ex_theta
261 all_arg_tys = dict_tys ++ ex_dict_tys ++ orig_arg_tys
262 result_ty = mkTyConApp tycon (mkTyVarTys tyvars)
264 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
268 (dict_args, i1) = mkLocals 1 dict_tys
269 (ex_dict_args,i2) = mkLocals i1 ex_dict_tys
270 (id_args,i3) = mkLocals i2 orig_arg_tys
272 (id_arg1:_) = id_args -- Used for newtype only
274 strict_marks = dataConStrictMarks data_con
275 not_marked_strict NotMarkedStrict = True
276 not_marked_strict other = False
280 :: (Id, StrictnessMark) -- arg, strictness
281 -> (Int -> [Id] -> CoreExpr) -- body
282 -> Int -- next rep arg id
283 -> [Id] -- rep args so far
285 mk_case (arg,strict) body i rep_args
287 NotMarkedStrict -> body i (arg:rep_args)
289 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
291 Case (Var arg) arg [(DEFAULT,[], body i (arg:rep_args))]
293 MarkedUnboxed con tys ->
294 Case (Var arg) arg [(DataAlt con, con_args,
295 body i' (reverse con_args++rep_args))]
297 (con_args,i') = mkLocals i tys
301 %************************************************************************
303 \subsection{Record selectors}
305 %************************************************************************
307 We're going to build a record selector unfolding that looks like this:
309 data T a b c = T1 { ..., op :: a, ...}
310 | T2 { ..., op :: a, ...}
313 sel = /\ a b c -> \ d -> case d of
318 Similarly for newtypes
320 newtype N a = MkN { unN :: a->a }
323 unN n = coerce (a->a) n
325 We need to take a little care if the field has a polymorphic type:
327 data R = R { f :: forall a. a->a }
331 f :: forall a. R -> a -> a
332 f = /\ a \ r = case r of
335 (not f :: R -> forall a. a->a, which gives the type inference mechanism
336 problems at call sites)
338 Similarly for newtypes
340 newtype N = MkN { unN :: forall a. a->a }
342 unN :: forall a. N -> a -> a
343 unN = /\a -> \n:N -> coerce (a->a) n
346 mkRecordSelId tycon field_label unpack_id unpackUtf8_id
347 -- Assumes that all fields with the same field label have the same type
349 -- Annoyingly, we have to pass in the unpackCString# Id, because
350 -- we can't conjure it up out of thin air
353 sel_id = mkGlobalId (RecordSelId field_label) (fieldLabelName field_label) selector_ty info
354 field_ty = fieldLabelType field_label
355 data_cons = tyConDataCons tycon
356 tyvars = tyConTyVars tycon -- These scope over the types in
357 -- the FieldLabels of constructors of this type
358 data_ty = mkTyConApp tycon tyvar_tys
359 tyvar_tys = mkTyVarTys tyvars
361 tycon_theta = tyConTheta tycon -- The context on the data decl
362 -- eg data (Eq a, Ord b) => T a b = ...
363 dict_tys = [mkPredTy pred | pred <- tycon_theta,
365 needed_dict pred = or [ pred `elem` (dataConTheta dc)
366 | (DataAlt dc, _, _) <- the_alts]
367 n_dict_tys = length dict_tys
369 (field_tyvars,field_theta,field_tau) = splitSigmaTy field_ty
370 field_dict_tys = map mkPredTy field_theta
371 n_field_dict_tys = length field_dict_tys
372 -- If the field has a universally quantified type we have to
373 -- be a bit careful. Suppose we have
374 -- data R = R { op :: forall a. Foo a => a -> a }
375 -- Then we can't give op the type
376 -- op :: R -> forall a. Foo a => a -> a
377 -- because the typechecker doesn't understand foralls to the
378 -- right of an arrow. The "right" type to give it is
379 -- op :: forall a. Foo a => R -> a -> a
380 -- But then we must generate the right unfolding too:
381 -- op = /\a -> \dfoo -> \ r ->
384 -- Note that this is exactly the type we'd infer from a user defn
387 -- Very tiresomely, the selectors are (unnecessarily!) overloaded over
388 -- just the dictionaries in the types of the constructors that contain
389 -- the relevant field. Urgh.
390 -- NB: this code relies on the fact that DataCons are quantified over
391 -- the identical type variables as their parent TyCon
394 selector_ty = mkForAllTys tyvars $ mkForAllTys field_tyvars $
395 mkFunTys dict_tys $ mkFunTys field_dict_tys $
396 mkFunTy data_ty field_tau
398 arity = 1 + n_dict_tys + n_field_dict_tys
399 info = noCafNoTyGenIdInfo
400 `setCgInfo` (CgInfo arity caf_info)
401 `setArityInfo` exactArity arity
402 `setUnfoldingInfo` unfolding
403 -- ToDo: consider adding further IdInfo
405 unfolding = mkTopUnfolding sel_rhs
407 -- Allocate Ids. We do it a funny way round because field_dict_tys is
408 -- almost always empty. Also note that we use length_tycon_theta
409 -- rather than n_dict_tys, because the latter gives an infinite loop:
410 -- n_dict tys depends on the_alts, which depens on arg_ids, which depends
411 -- on arity, which depends on n_dict tys. Sigh! Mega sigh!
412 field_dict_base = length tycon_theta + 1
413 dict_id_base = field_dict_base + n_field_dict_tys
414 field_base = dict_id_base + 1
415 dict_ids = mkTemplateLocalsNum 1 dict_tys
416 field_dict_ids = mkTemplateLocalsNum field_dict_base field_dict_tys
417 data_id = mkTemplateLocal dict_id_base data_ty
419 alts = map mk_maybe_alt data_cons
420 the_alts = catMaybes alts
422 no_default = all isJust alts -- No default needed
423 default_alt | no_default = []
424 | otherwise = [(DEFAULT, [], error_expr)]
426 -- the default branch may have CAF refs, because it calls recSelError etc.
427 caf_info | no_default = NoCafRefs
428 | otherwise = MayHaveCafRefs
430 sel_rhs = mkLams tyvars $ mkLams field_tyvars $
431 mkLams dict_ids $ mkLams field_dict_ids $
432 Lam data_id $ sel_body
434 sel_body | isNewTyCon tycon = Note (Coerce field_tau data_ty) (Var data_id)
435 | otherwise = Case (Var data_id) data_id (the_alts ++ default_alt)
437 mk_maybe_alt data_con
438 = case maybe_the_arg_id of
440 Just the_arg_id -> Just (DataAlt data_con, real_args, expr)
442 body = mkVarApps (mkVarApps (Var the_arg_id) field_tyvars) field_dict_ids
443 strict_marks = dataConStrictMarks data_con
444 (expr, real_args) = rebuildConArgs data_con arg_ids strict_marks body
447 arg_ids = mkTemplateLocalsNum field_base (dataConInstOrigArgTys data_con tyvar_tys)
448 -- arity+1 avoids all shadowing
449 maybe_the_arg_id = assocMaybe (field_lbls `zip` arg_ids) field_label
450 field_lbls = dataConFieldLabels data_con
452 error_expr = mkApps (Var rEC_SEL_ERROR_ID) [Type field_tau, err_string]
454 | all safeChar full_msg
455 = App (Var unpack_id) (Lit (MachStr (_PK_ full_msg)))
457 = App (Var unpackUtf8_id) (Lit (MachStr (_PK_ (stringToUtf8 (map ord full_msg)))))
459 safeChar c = c >= '\1' && c <= '\xFF'
460 -- TODO: Putting this Unicode stuff here is ugly. Find a better
461 -- generic place to make string literals. This logic is repeated
463 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
466 -- this rather ugly function converts the unpacked data con arguments back into
467 -- their packed form. It is almost the same as the version in DsUtils, except that
468 -- we use template locals here rather than newDsId (ToDo: merge these).
471 :: DataCon -- the con we're matching on
472 -> [Id] -- the source-level args
473 -> [StrictnessMark] -- the strictness annotations (per-arg)
474 -> CoreExpr -- the body
475 -> Int -- template local
478 rebuildConArgs con [] stricts body i = (body, [])
479 rebuildConArgs con (arg:args) stricts body i | isTyVar arg
480 = let (body', args') = rebuildConArgs con args stricts body i
482 rebuildConArgs con (arg:args) (str:stricts) body i
483 = case maybeMarkedUnboxed str of
484 Just (pack_con1, _) ->
485 case splitProductType_maybe (idType arg) of
486 Just (_, tycon_args, pack_con, con_arg_tys) ->
487 ASSERT( pack_con == pack_con1 )
488 let unpacked_args = zipWith mkTemplateLocal [i..] con_arg_tys
489 (body', real_args) = rebuildConArgs con args stricts body
490 (i + length con_arg_tys)
493 Let (NonRec arg (mkConApp pack_con
494 (map Type tycon_args ++
495 map Var unpacked_args))) body',
496 unpacked_args ++ real_args
499 _ -> let (body', args') = rebuildConArgs con args stricts body i
500 in (body', arg:args')
504 %************************************************************************
506 \subsection{Dictionary selectors}
508 %************************************************************************
510 Selecting a field for a dictionary. If there is just one field, then
511 there's nothing to do.
513 ToDo: unify with mkRecordSelId.
516 mkDictSelId :: Name -> Class -> Id
517 mkDictSelId name clas
521 sel_id = mkGlobalId (RecordSelId field_lbl) name ty info
522 field_lbl = mkFieldLabel name tycon ty tag
523 tag = assoc "MkId.mkDictSelId" (classSelIds clas `zip` allFieldLabelTags) sel_id
525 info = noCafNoTyGenIdInfo
527 `setArityInfo` exactArity 1
528 `setUnfoldingInfo` unfolding
530 -- We no longer use 'must-inline' on record selectors. They'll
531 -- inline like crazy if they scrutinise a constructor
533 unfolding = mkTopUnfolding rhs
535 tyvars = classTyVars clas
537 tycon = classTyCon clas
538 [data_con] = tyConDataCons tycon
539 tyvar_tys = mkTyVarTys tyvars
540 arg_tys = dataConArgTys data_con tyvar_tys
541 the_arg_id = arg_ids !! (tag - firstFieldLabelTag)
543 dict_ty = mkDictTy clas tyvar_tys
544 (dict_id:arg_ids) = mkTemplateLocals (dict_ty : arg_tys)
546 rhs | isNewTyCon tycon = mkLams tyvars $ Lam dict_id $
547 Note (Coerce (head arg_tys) dict_ty) (Var dict_id)
548 | otherwise = mkLams tyvars $ Lam dict_id $
549 Case (Var dict_id) dict_id
550 [(DataAlt data_con, arg_ids, Var the_arg_id)]
554 %************************************************************************
556 \subsection{Primitive operations
558 %************************************************************************
561 mkPrimOpId :: PrimOp -> Id
565 (tyvars,arg_tys,res_ty, arity, strict_info) = primOpSig prim_op
566 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
567 name = mkPrimOpIdName prim_op
568 id = mkGlobalId (PrimOpId prim_op) name ty info
570 info = noCafNoTyGenIdInfo
573 `setArityInfo` exactArity arity
574 `setStrictnessInfo` strict_info
576 rules = addRule emptyCoreRules id (primOpRule prim_op)
579 -- For each ccall we manufacture a separate CCallOpId, giving it
580 -- a fresh unique, a type that is correct for this particular ccall,
581 -- and a CCall structure that gives the correct details about calling
584 -- The *name* of this Id is a local name whose OccName gives the full
585 -- details of the ccall, type and all. This means that the interface
586 -- file reader can reconstruct a suitable Id
588 mkCCallOpId :: Unique -> CCall -> Type -> Id
589 mkCCallOpId uniq ccall ty
590 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
591 -- A CCallOpId should have no free type variables;
592 -- when doing substitutions won't substitute over it
593 mkGlobalId (PrimOpId prim_op) name ty info
595 occ_str = showSDocIface (braces (pprCCallOp ccall <+> ppr ty))
596 -- The "occurrence name" of a ccall is the full info about the
597 -- ccall; it is encoded, but may have embedded spaces etc!
599 name = mkCCallName uniq occ_str
600 prim_op = CCallOp ccall
602 info = noCafNoTyGenIdInfo
604 `setArityInfo` exactArity arity
605 `setStrictnessInfo` strict_info
607 (_, tau) = splitForAllTys ty
608 (arg_tys, _) = splitFunTys tau
609 arity = length arg_tys
610 strict_info = mkStrictnessInfo (take arity (repeat wwPrim), False)
614 %************************************************************************
616 \subsection{DictFuns and default methods}
618 %************************************************************************
621 mkDefaultMethodId dm_name ty
622 = mkVanillaGlobal dm_name ty noCafNoTyGenIdInfo
624 mkDictFunId :: Name -- Name to use for the dict fun;
631 mkDictFunId dfun_name clas inst_tyvars inst_tys dfun_theta
632 = mkVanillaGlobal dfun_name dfun_ty noCafNoTyGenIdInfo
634 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
636 {- 1 dec 99: disable the Mark Jones optimisation for the sake
637 of compatibility with Hugs.
638 See `types/InstEnv' for a discussion related to this.
640 (class_tyvars, sc_theta, _, _) = classBigSig clas
641 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
642 sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys) sc_theta
643 dfun_theta = case inst_decl_theta of
644 [] -> [] -- If inst_decl_theta is empty, then we don't
645 -- want to have any dict arguments, so that we can
646 -- expose the constant methods.
648 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
649 -- Otherwise we pass the superclass dictionaries to
650 -- the dictionary function; the Mark Jones optimisation.
652 -- NOTE the "nub". I got caught by this one:
653 -- class Monad m => MonadT t m where ...
654 -- instance Monad m => MonadT (EnvT env) m where ...
655 -- Here, the inst_decl_theta has (Monad m); but so
656 -- does the sc_theta'!
658 -- NOTE the "not_const". I got caught by this one too:
659 -- class Foo a => Baz a b where ...
660 -- instance Wob b => Baz T b where..
661 -- Now sc_theta' has Foo T
666 %************************************************************************
668 \subsection{Un-definable}
670 %************************************************************************
672 These two can't be defined in Haskell.
674 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
675 just gets expanded into a type coercion wherever it occurs. Hence we
676 add it as a built-in Id with an unfolding here.
678 The type variables we use here are "open" type variables: this means
679 they can unify with both unlifted and lifted types. Hence we provide
680 another gun with which to shoot yourself in the foot.
684 = pcMiscPrelId unsafeCoerceIdKey pREL_GHC SLIT("unsafeCoerce#") ty info
686 info = noCafNoTyGenIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
689 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
690 (mkFunTy openAlphaTy openBetaTy)
691 [x] = mkTemplateLocals [openAlphaTy]
692 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
693 Note (Coerce openBetaTy openAlphaTy) (Var x)
697 @getTag#@ is another function which can't be defined in Haskell. It needs to
698 evaluate its argument and call the dataToTag# primitive.
702 = pcMiscPrelId getTagIdKey pREL_GHC SLIT("getTag#") ty info
704 info = noCafNoTyGenIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
705 -- We don't provide a defn for this; you must inline it
707 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy intPrimTy)
708 [x,y] = mkTemplateLocals [alphaTy,alphaTy]
709 rhs = mkLams [alphaTyVar,x] $
710 Case (Var x) y [ (DEFAULT, [], mkApps (Var dataToTagId) [Type alphaTy, Var y]) ]
712 dataToTagId = mkPrimOpId DataToTagOp
715 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
716 nasty as-is, change it back to a literal (@Literal@).
719 realWorldPrimId -- :: State# RealWorld
720 = pcMiscPrelId realWorldPrimIdKey pREL_GHC SLIT("realWorld#")
722 (noCafNoTyGenIdInfo `setUnfoldingInfo` mkOtherCon [])
723 -- The mkOtherCon makes it look that realWorld# is evaluated
724 -- which in turn makes Simplify.interestingArg return True,
725 -- which in turn makes INLINE things applied to realWorld# likely
730 %************************************************************************
732 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
734 %************************************************************************
736 GHC randomly injects these into the code.
738 @patError@ is just a version of @error@ for pattern-matching
739 failures. It knows various ``codes'' which expand to longer
740 strings---this saves space!
742 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
743 well shouldn't be yanked on, but if one is, then you will get a
744 friendly message from @absentErr@ (rather than a totally random
747 @parError@ is a special version of @error@ which the compiler does
748 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
749 templates, but we don't ever expect to generate code for it.
753 = pc_bottoming_Id errorIdKey pREL_ERR SLIT("error") errorTy
755 = generic_ERROR_ID patErrorIdKey SLIT("patError")
757 = generic_ERROR_ID recSelErrIdKey SLIT("recSelError")
759 = generic_ERROR_ID recConErrorIdKey SLIT("recConError")
761 = generic_ERROR_ID recUpdErrorIdKey SLIT("recUpdError")
763 = generic_ERROR_ID irrefutPatErrorIdKey SLIT("irrefutPatError")
764 nON_EXHAUSTIVE_GUARDS_ERROR_ID
765 = generic_ERROR_ID nonExhaustiveGuardsErrorIdKey SLIT("nonExhaustiveGuardsError")
766 nO_METHOD_BINDING_ERROR_ID
767 = generic_ERROR_ID noMethodBindingErrorIdKey SLIT("noMethodBindingError")
770 = pc_bottoming_Id absentErrorIdKey pREL_ERR SLIT("absentErr")
771 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy)
774 = pcMiscPrelId parErrorIdKey pREL_ERR SLIT("parError")
775 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy) noCafNoTyGenIdInfo
779 %************************************************************************
781 \subsection{Utilities}
783 %************************************************************************
786 pcMiscPrelId :: Unique{-IdKey-} -> Module -> FAST_STRING -> Type -> IdInfo -> Id
787 pcMiscPrelId key mod str ty info
789 name = mkWiredInName mod (mkVarOcc str) key
790 imp = mkVanillaGlobal name ty info -- the usual case...
793 -- We lie and say the thing is imported; otherwise, we get into
794 -- a mess with dependency analysis; e.g., core2stg may heave in
795 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
796 -- being compiled, then it's just a matter of luck if the definition
797 -- will be in "the right place" to be in scope.
799 pc_bottoming_Id key mod name ty
800 = pcMiscPrelId key mod name ty bottoming_info
802 bottoming_info = noCafNoTyGenIdInfo
803 `setStrictnessInfo` mkStrictnessInfo ([wwStrict], True)
805 -- these "bottom" out, no matter what their arguments
807 generic_ERROR_ID u n = pc_bottoming_Id u pREL_ERR n errorTy
809 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
810 openAlphaTy = mkTyVarTy openAlphaTyVar
811 openBetaTy = mkTyVarTy openBetaTyVar
814 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy]
816 -- Notice the openAlphaTyVar. It says that "error" can be applied
817 -- to unboxed as well as boxed types. This is OK because it never
818 -- returns, so the return type is irrelevant.