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 ( 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, splitSigmaTy,
45 isUnLiftedType, mkForAllTys, mkTyVarTy, tyVarsOfType,
46 splitFunTys, splitForAllTys, mkPredTy
48 import Module ( Module )
49 import CoreUtils ( exprType, mkInlineMe )
50 import CoreUnfold ( mkTopUnfolding, mkCompulsoryUnfolding, mkOtherCon )
51 import Literal ( Literal(..) )
52 import TyCon ( TyCon, isNewTyCon, tyConTyVars, tyConDataCons,
53 tyConTheta, isProductTyCon, isDataTyCon )
54 import Class ( Class, classTyCon, classTyVars, classSelIds )
55 import Var ( Id, TyVar )
56 import VarSet ( isEmptyVarSet )
57 import Name ( mkWiredInName, mkLocalName,
58 mkWorkerOcc, mkCCallName,
59 Name, NamedThing(..), getSrcLoc
61 import OccName ( mkVarOcc )
62 import PrimOp ( PrimOp(DataToTagOp, CCallOp),
63 primOpSig, mkPrimOpIdName,
66 import Demand ( wwStrict, wwPrim, mkStrictnessInfo )
67 import DataCon ( DataCon, StrictnessMark(..),
68 dataConFieldLabels, dataConRepArity, dataConTyCon,
69 dataConArgTys, dataConRepType, dataConRepStrictness,
70 dataConInstOrigArgTys,
71 dataConName, dataConTheta,
72 dataConSig, dataConStrictMarks, dataConId,
73 maybeMarkedUnboxed, splitProductType_maybe
75 import Id ( idType, mkId,
76 mkVanillaId, mkTemplateLocals, mkTemplateLocalsNum,
77 mkTemplateLocal, idCprInfo
79 import IdInfo ( IdInfo, constantIdInfo, mkIdInfo,
80 exactArity, setUnfoldingInfo, setCafInfo, setCprInfo,
81 setArityInfo, setSpecInfo, setTyGenInfo,
82 mkStrictnessInfo, setStrictnessInfo,
83 IdFlavour(..), CafInfo(..), CprInfo(..), TyGenInfo(..)
85 import FieldLabel ( mkFieldLabel, fieldLabelName,
86 firstFieldLabelTag, allFieldLabelTags, fieldLabelType
91 import Maybe ( isJust )
93 import ListSetOps ( assoc, assocMaybe )
94 import UnicodeUtil ( stringToUtf8 )
99 %************************************************************************
101 \subsection{Wired in Ids}
103 %************************************************************************
107 = [ -- These error-y things are wired in because we don't yet have
108 -- a way to express in an interface file that the result type variable
109 -- is 'open'; that is can be unified with an unboxed type
111 -- [The interface file format now carry such information, but there's
112 -- no way yet of expressing at the definition site for these
114 -- functions that they have an 'open' result type. -- sof 1/99]
118 , iRREFUT_PAT_ERROR_ID
119 , nON_EXHAUSTIVE_GUARDS_ERROR_ID
120 , nO_METHOD_BINDING_ERROR_ID
126 -- These two can't be defined in Haskell
133 %************************************************************************
135 \subsection{Easy ones}
137 %************************************************************************
140 mkSpecPragmaId occ uniq ty loc
141 = mkId (mkLocalName uniq occ loc) ty (mkIdInfo SpecPragmaId NoCafRefs)
142 -- Maybe a SysLocal? But then we'd lose the location
144 mkDefaultMethodId dm_name rec_c ty
145 = mkId dm_name ty info
147 info = constantIdInfo `setTyGenInfo` TyGenNever
148 -- type is wired-in (see comment at TcClassDcl.tcClassSig), so
149 -- do not generalise it
151 mkWorkerId :: Unique -> Id -> Type -> Id
152 -- A worker gets a local name. CoreTidy will globalise it if necessary.
153 mkWorkerId uniq unwrkr ty
154 = mkVanillaId wkr_name ty
156 wkr_name = mkLocalName uniq (mkWorkerOcc (getOccName unwrkr)) (getSrcLoc unwrkr)
159 %************************************************************************
161 \subsection{Data constructors}
163 %************************************************************************
166 mkDataConId :: Name -> DataCon -> Id
167 -- Makes the *worker* for the data constructor; that is, the function
168 -- that takes the reprsentation arguments and builds the constructor.
169 mkDataConId work_name data_con
170 = mkId work_name (dataConRepType data_con) info
172 info = mkIdInfo (DataConId data_con) NoCafRefs
173 `setArityInfo` exactArity arity
174 `setStrictnessInfo` strict_info
175 `setCprInfo` cpr_info
177 arity = dataConRepArity data_con
179 strict_info = mkStrictnessInfo (dataConRepStrictness data_con, False)
181 tycon = dataConTyCon data_con
182 cpr_info | isProductTyCon tycon &&
184 arity > 0 = ReturnsCPR
185 | otherwise = NoCPRInfo
186 -- ReturnsCPR is only true for products that are real data types;
187 -- that is, not unboxed tuples or newtypes
190 The wrapper for a constructor is an ordinary top-level binding that evaluates
191 any strict args, unboxes any args that are going to be flattened, and calls
194 We're going to build a constructor that looks like:
196 data (Data a, C b) => T a b = T1 !a !Int b
199 \d1::Data a, d2::C b ->
200 \p q r -> case p of { p ->
202 Con T1 [a,b] [p,q,r]}}
206 * d2 is thrown away --- a context in a data decl is used to make sure
207 one *could* construct dictionaries at the site the constructor
208 is used, but the dictionary isn't actually used.
210 * We have to check that we can construct Data dictionaries for
211 the types a and Int. Once we've done that we can throw d1 away too.
213 * We use (case p of q -> ...) to evaluate p, rather than "seq" because
214 all that matters is that the arguments are evaluated. "seq" is
215 very careful to preserve evaluation order, which we don't need
218 You might think that we could simply give constructors some strictness
219 info, like PrimOps, and let CoreToStg do the let-to-case transformation.
220 But we don't do that because in the case of primops and functions strictness
221 is a *property* not a *requirement*. In the case of constructors we need to
222 do something active to evaluate the argument.
224 Making an explicit case expression allows the simplifier to eliminate
225 it in the (common) case where the constructor arg is already evaluated.
228 mkDataConWrapId data_con
231 wrap_id = mkId (dataConName data_con) wrap_ty info
232 work_id = dataConId data_con
234 info = mkIdInfo (DataConWrapId data_con) NoCafRefs
235 `setUnfoldingInfo` mkTopUnfolding (mkInlineMe wrap_rhs)
236 `setCprInfo` cpr_info
237 -- The Cpr info can be important inside INLINE rhss, where the
238 -- wrapper constructor isn't inlined
239 `setArityInfo` exactArity arity
240 -- It's important to specify the arity, so that partial
241 -- applications are treated as values
242 `setTyGenInfo` TyGenNever
243 -- No point generalising its type, since it gets eagerly inlined
246 wrap_ty = mkForAllTys all_tyvars $
250 cpr_info = idCprInfo work_id
252 wrap_rhs | isNewTyCon tycon
253 = ASSERT( null ex_tyvars && null ex_dict_args && length orig_arg_tys == 1 )
254 -- No existentials on a newtype, but it can have a context
255 -- e.g. newtype Eq a => T a = MkT (...)
257 mkLams tyvars $ mkLams dict_args $ Lam id_arg1 $
258 Note (Coerce result_ty (head orig_arg_tys)) (Var id_arg1)
260 | null dict_args && all not_marked_strict strict_marks
261 = Var work_id -- The common case. Not only is this efficient,
262 -- but it also ensures that the wrapper is replaced
263 -- by the worker even when there are no args.
267 -- This is really important in rule matching,
268 -- (We could match on the wrappers,
269 -- but that makes it less likely that rules will match
270 -- when we bring bits of unfoldings together.)
272 -- NB: because of this special case, (map (:) ys) turns into
273 -- (map $w: ys), and thence into (map (\x xs. $w: x xs) ys)
274 -- in core-to-stg. The top-level defn for (:) is never used.
275 -- This is somewhat of a bore, but I'm currently leaving it
276 -- as is, so that there still is a top level curried (:) for
277 -- the interpreter to call.
280 = mkLams all_tyvars $ mkLams dict_args $
281 mkLams ex_dict_args $ mkLams id_args $
282 foldr mk_case con_app
283 (zip (ex_dict_args++id_args) strict_marks) i3 []
285 con_app i rep_ids = mkApps (Var work_id)
286 (map varToCoreExpr (all_tyvars ++ reverse rep_ids))
288 (tyvars, theta, ex_tyvars, ex_theta, orig_arg_tys, tycon) = dataConSig data_con
289 all_tyvars = tyvars ++ ex_tyvars
291 dict_tys = mkDictTys theta
292 ex_dict_tys = mkDictTys ex_theta
293 all_arg_tys = dict_tys ++ ex_dict_tys ++ orig_arg_tys
294 result_ty = mkTyConApp tycon (mkTyVarTys tyvars)
296 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
300 (dict_args, i1) = mkLocals 1 dict_tys
301 (ex_dict_args,i2) = mkLocals i1 ex_dict_tys
302 (id_args,i3) = mkLocals i2 orig_arg_tys
304 (id_arg1:_) = id_args -- Used for newtype only
306 strict_marks = dataConStrictMarks data_con
307 not_marked_strict NotMarkedStrict = True
308 not_marked_strict other = False
312 :: (Id, StrictnessMark) -- arg, strictness
313 -> (Int -> [Id] -> CoreExpr) -- body
314 -> Int -- next rep arg id
315 -> [Id] -- rep args so far
317 mk_case (arg,strict) body i rep_args
319 NotMarkedStrict -> body i (arg:rep_args)
321 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
323 Case (Var arg) arg [(DEFAULT,[], body i (arg:rep_args))]
325 MarkedUnboxed con tys ->
326 Case (Var arg) arg [(DataAlt con, con_args,
327 body i' (reverse con_args++rep_args))]
329 (con_args,i') = mkLocals i tys
333 %************************************************************************
335 \subsection{Record selectors}
337 %************************************************************************
339 We're going to build a record selector unfolding that looks like this:
341 data T a b c = T1 { ..., op :: a, ...}
342 | T2 { ..., op :: a, ...}
345 sel = /\ a b c -> \ d -> case d of
350 Similarly for newtypes
352 newtype N a = MkN { unN :: a->a }
355 unN n = coerce (a->a) n
357 We need to take a little care if the field has a polymorphic type:
359 data R = R { f :: forall a. a->a }
363 f :: forall a. R -> a -> a
364 f = /\ a \ r = case r of
367 (not f :: R -> forall a. a->a, which gives the type inference mechanism
368 problems at call sites)
370 Similarly for newtypes
372 newtype N = MkN { unN :: forall a. a->a }
374 unN :: forall a. N -> a -> a
375 unN = /\a -> \n:N -> coerce (a->a) n
378 mkRecordSelId tycon field_label unpack_id unpackUtf8_id
379 -- Assumes that all fields with the same field label have the same type
381 -- Annoyingly, we have to pass in the unpackCString# Id, because
382 -- we can't conjure it up out of thin air
385 sel_id = mkId (fieldLabelName field_label) selector_ty info
387 field_ty = fieldLabelType field_label
388 data_cons = tyConDataCons tycon
389 tyvars = tyConTyVars tycon -- These scope over the types in
390 -- the FieldLabels of constructors of this type
391 data_ty = mkTyConApp tycon tyvar_tys
392 tyvar_tys = mkTyVarTys tyvars
394 tycon_theta = tyConTheta tycon -- The context on the data decl
395 -- eg data (Eq a, Ord b) => T a b = ...
396 dict_tys = [mkDictTy cls tys | (cls, tys) <- tycon_theta,
397 needed_dict (cls, tys)]
398 needed_dict pred = or [ pred `elem` (dataConTheta dc)
399 | (DataAlt dc, _, _) <- the_alts]
400 n_dict_tys = length dict_tys
402 (field_tyvars,field_theta,field_tau) = splitSigmaTy field_ty
403 field_dict_tys = map mkPredTy field_theta
404 n_field_dict_tys = length field_dict_tys
405 -- If the field has a universally quantified type we have to
406 -- be a bit careful. Suppose we have
407 -- data R = R { op :: forall a. Foo a => a -> a }
408 -- Then we can't give op the type
409 -- op :: R -> forall a. Foo a => a -> a
410 -- because the typechecker doesn't understand foralls to the
411 -- right of an arrow. The "right" type to give it is
412 -- op :: forall a. Foo a => R -> a -> a
413 -- But then we must generate the right unfolding too:
414 -- op = /\a -> \dfoo -> \ r ->
417 -- Note that this is exactly the type we'd infer from a user defn
420 -- Very tiresomely, the selectors are (unnecessarily!) overloaded over
421 -- just the dictionaries in the types of the constructors that contain
422 -- the relevant field. Urgh.
423 -- NB: this code relies on the fact that DataCons are quantified over
424 -- the identical type variables as their parent TyCon
427 selector_ty = mkForAllTys tyvars $ mkForAllTys field_tyvars $
428 mkFunTys dict_tys $ mkFunTys field_dict_tys $
429 mkFunTy data_ty field_tau
431 arity = 1 + n_dict_tys + n_field_dict_tys
432 info = mkIdInfo (RecordSelId field_label) caf_info
433 `setArityInfo` exactArity arity
434 `setUnfoldingInfo` unfolding
435 `setTyGenInfo` TyGenNever
436 -- ToDo: consider adding further IdInfo
438 unfolding = mkTopUnfolding sel_rhs
440 -- Allocate Ids. We do it a funny way round because field_dict_tys is
441 -- almost always empty. Also note that we use length_tycon_theta
442 -- rather than n_dict_tys, because the latter gives an infinite loop:
443 -- n_dict tys depends on the_alts, which depens on arg_ids, which depends
444 -- on arity, which depends on n_dict tys. Sigh! Mega sigh!
445 field_dict_base = length tycon_theta + 1
446 dict_id_base = field_dict_base + n_field_dict_tys
447 field_base = dict_id_base + 1
448 dict_ids = mkTemplateLocalsNum 1 dict_tys
449 field_dict_ids = mkTemplateLocalsNum field_dict_base field_dict_tys
450 data_id = mkTemplateLocal dict_id_base data_ty
452 alts = map mk_maybe_alt data_cons
453 the_alts = catMaybes alts
455 no_default = all isJust alts -- No default needed
456 default_alt | no_default = []
457 | otherwise = [(DEFAULT, [], error_expr)]
459 -- the default branch may have CAF refs, because it calls recSelError etc.
460 caf_info | no_default = NoCafRefs
461 | otherwise = MayHaveCafRefs
463 sel_rhs = mkLams tyvars $ mkLams field_tyvars $
464 mkLams dict_ids $ mkLams field_dict_ids $
465 Lam data_id $ sel_body
467 sel_body | isNewTyCon tycon = Note (Coerce field_tau data_ty) (Var data_id)
468 | otherwise = Case (Var data_id) data_id (the_alts ++ default_alt)
470 mk_maybe_alt data_con
471 = case maybe_the_arg_id of
473 Just the_arg_id -> Just (DataAlt data_con, real_args, expr)
475 body = mkVarApps (mkVarApps (Var the_arg_id) field_tyvars) field_dict_ids
476 strict_marks = dataConStrictMarks data_con
477 (expr, real_args) = rebuildConArgs data_con arg_ids strict_marks body
480 arg_ids = mkTemplateLocalsNum field_base (dataConInstOrigArgTys data_con tyvar_tys)
481 -- arity+1 avoids all shadowing
482 maybe_the_arg_id = assocMaybe (field_lbls `zip` arg_ids) field_label
483 field_lbls = dataConFieldLabels data_con
485 error_expr = mkApps (Var rEC_SEL_ERROR_ID) [Type field_tau, err_string]
487 | all safeChar full_msg
488 = App (Var unpack_id) (Lit (MachStr (_PK_ full_msg)))
490 = App (Var unpackUtf8_id) (Lit (MachStr (_PK_ (stringToUtf8 (map ord full_msg)))))
492 safeChar c = c >= '\1' && c <= '\xFF'
493 -- TODO: Putting this Unicode stuff here is ugly. Find a better
494 -- generic place to make string literals. This logic is repeated
496 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
499 -- this rather ugly function converts the unpacked data con arguments back into
500 -- their packed form. It is almost the same as the version in DsUtils, except that
501 -- we use template locals here rather than newDsId (ToDo: merge these).
504 :: DataCon -- the con we're matching on
505 -> [Id] -- the source-level args
506 -> [StrictnessMark] -- the strictness annotations (per-arg)
507 -> CoreExpr -- the body
508 -> Int -- template local
511 rebuildConArgs con [] stricts body i = (body, [])
512 rebuildConArgs con (arg:args) stricts body i | isTyVar arg
513 = let (body', args') = rebuildConArgs con args stricts body i
515 rebuildConArgs con (arg:args) (str:stricts) body i
516 = case maybeMarkedUnboxed str of
517 Just (pack_con1, _) ->
518 case splitProductType_maybe (idType arg) of
519 Just (_, tycon_args, pack_con, con_arg_tys) ->
520 ASSERT( pack_con == pack_con1 )
521 let unpacked_args = zipWith mkTemplateLocal [i..] con_arg_tys
522 (body', real_args) = rebuildConArgs con args stricts body
523 (i + length con_arg_tys)
526 Let (NonRec arg (mkConApp pack_con
527 (map Type tycon_args ++
528 map Var unpacked_args))) body',
529 unpacked_args ++ real_args
532 _ -> let (body', args') = rebuildConArgs con args stricts body i
533 in (body', arg:args')
537 %************************************************************************
539 \subsection{Dictionary selectors}
541 %************************************************************************
543 Selecting a field for a dictionary. If there is just one field, then
544 there's nothing to do.
546 ToDo: unify with mkRecordSelId.
549 mkDictSelId :: Name -> Class -> Id
550 mkDictSelId name clas
554 sel_id = mkId name ty info
555 field_lbl = mkFieldLabel name tycon ty tag
556 tag = assoc "MkId.mkDictSelId" (classSelIds clas `zip` allFieldLabelTags) sel_id
558 info = mkIdInfo (RecordSelId field_lbl) NoCafRefs
559 `setArityInfo` exactArity 1
560 `setUnfoldingInfo` unfolding
561 `setTyGenInfo` TyGenNever
563 -- We no longer use 'must-inline' on record selectors. They'll
564 -- inline like crazy if they scrutinise a constructor
566 unfolding = mkTopUnfolding rhs
568 tyvars = classTyVars clas
570 tycon = classTyCon clas
571 [data_con] = tyConDataCons tycon
572 tyvar_tys = mkTyVarTys tyvars
573 arg_tys = dataConArgTys data_con tyvar_tys
574 the_arg_id = arg_ids !! (tag - firstFieldLabelTag)
576 dict_ty = mkDictTy clas tyvar_tys
577 (dict_id:arg_ids) = mkTemplateLocals (dict_ty : arg_tys)
579 rhs | isNewTyCon tycon = mkLams tyvars $ Lam dict_id $
580 Note (Coerce (head arg_tys) dict_ty) (Var dict_id)
581 | otherwise = mkLams tyvars $ Lam dict_id $
582 Case (Var dict_id) dict_id
583 [(DataAlt data_con, arg_ids, Var the_arg_id)]
587 %************************************************************************
589 \subsection{Primitive operations
591 %************************************************************************
594 mkPrimOpId :: PrimOp -> Id
598 (tyvars,arg_tys,res_ty, arity, strict_info) = primOpSig prim_op
599 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
600 name = mkPrimOpIdName prim_op
601 id = mkId name ty info
603 info = mkIdInfo (PrimOpId prim_op) NoCafRefs
605 `setArityInfo` exactArity arity
606 `setStrictnessInfo` strict_info
608 rules = addRule emptyCoreRules id (primOpRule prim_op)
611 -- For each ccall we manufacture a separate CCallOpId, giving it
612 -- a fresh unique, a type that is correct for this particular ccall,
613 -- and a CCall structure that gives the correct details about calling
616 -- The *name* of this Id is a local name whose OccName gives the full
617 -- details of the ccall, type and all. This means that the interface
618 -- file reader can reconstruct a suitable Id
620 mkCCallOpId :: Unique -> CCall -> Type -> Id
621 mkCCallOpId uniq ccall ty
622 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
623 -- A CCallOpId should have no free type variables;
624 -- when doing substitutions won't substitute over it
627 occ_str = showSDocIface (braces (pprCCallOp ccall <+> ppr ty))
628 -- The "occurrence name" of a ccall is the full info about the
629 -- ccall; it is encoded, but may have embedded spaces etc!
631 name = mkCCallName uniq occ_str
632 prim_op = CCallOp ccall
634 info = mkIdInfo (PrimOpId prim_op) NoCafRefs
635 `setArityInfo` exactArity arity
636 `setStrictnessInfo` strict_info
638 (_, tau) = splitForAllTys ty
639 (arg_tys, _) = splitFunTys tau
640 arity = length arg_tys
641 strict_info = mkStrictnessInfo (take arity (repeat wwPrim), False)
645 %************************************************************************
647 \subsection{DictFuns}
649 %************************************************************************
652 mkDictFunId :: Name -- Name to use for the dict fun;
659 mkDictFunId dfun_name clas inst_tyvars inst_tys dfun_theta
660 = mkId dfun_name dfun_ty info
662 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
663 info = mkIdInfo DictFunId MayHaveCafRefs
664 `setTyGenInfo` TyGenNever
665 -- type is wired-in (see comment at TcClassDcl.tcClassSig), so
666 -- do not generalise it
667 -- An imported dfun may refer to CAFs, so we assume the worst
669 {- 1 dec 99: disable the Mark Jones optimisation for the sake
670 of compatibility with Hugs.
671 See `types/InstEnv' for a discussion related to this.
673 (class_tyvars, sc_theta, _, _) = classBigSig clas
674 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
675 sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys) sc_theta
676 dfun_theta = case inst_decl_theta of
677 [] -> [] -- If inst_decl_theta is empty, then we don't
678 -- want to have any dict arguments, so that we can
679 -- expose the constant methods.
681 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
682 -- Otherwise we pass the superclass dictionaries to
683 -- the dictionary function; the Mark Jones optimisation.
685 -- NOTE the "nub". I got caught by this one:
686 -- class Monad m => MonadT t m where ...
687 -- instance Monad m => MonadT (EnvT env) m where ...
688 -- Here, the inst_decl_theta has (Monad m); but so
689 -- does the sc_theta'!
691 -- NOTE the "not_const". I got caught by this one too:
692 -- class Foo a => Baz a b where ...
693 -- instance Wob b => Baz T b where..
694 -- Now sc_theta' has Foo T
699 %************************************************************************
701 \subsection{Un-definable}
703 %************************************************************************
705 These two can't be defined in Haskell.
707 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
708 just gets expanded into a type coercion wherever it occurs. Hence we
709 add it as a built-in Id with an unfolding here.
711 The type variables we use here are "open" type variables: this means
712 they can unify with both unlifted and lifted types. Hence we provide
713 another gun with which to shoot yourself in the foot.
717 = pcMiscPrelId unsafeCoerceIdKey pREL_GHC SLIT("unsafeCoerce#") ty info
719 info = constantIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
722 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
723 (mkFunTy openAlphaTy openBetaTy)
724 [x] = mkTemplateLocals [openAlphaTy]
725 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
726 Note (Coerce openBetaTy openAlphaTy) (Var x)
730 @getTag#@ is another function which can't be defined in Haskell. It needs to
731 evaluate its argument and call the dataToTag# primitive.
735 = pcMiscPrelId getTagIdKey pREL_GHC SLIT("getTag#") ty info
737 info = constantIdInfo
738 `setUnfoldingInfo` mkCompulsoryUnfolding rhs
739 -- We don't provide a defn for this; you must inline it
741 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy intPrimTy)
742 [x,y] = mkTemplateLocals [alphaTy,alphaTy]
743 rhs = mkLams [alphaTyVar,x] $
744 Case (Var x) y [ (DEFAULT, [], mkApps (Var dataToTagId) [Type alphaTy, Var y]) ]
746 dataToTagId = mkPrimOpId DataToTagOp
749 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
750 nasty as-is, change it back to a literal (@Literal@).
753 realWorldPrimId -- :: State# RealWorld
754 = pcMiscPrelId realWorldPrimIdKey pREL_GHC SLIT("realWorld#")
756 (noCafIdInfo `setUnfoldingInfo` mkOtherCon [])
757 -- The mkOtherCon makes it look that realWorld# is evaluated
758 -- which in turn makes Simplify.interestingArg return True,
759 -- which in turn makes INLINE things applied to realWorld# likely
764 %************************************************************************
766 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
768 %************************************************************************
770 GHC randomly injects these into the code.
772 @patError@ is just a version of @error@ for pattern-matching
773 failures. It knows various ``codes'' which expand to longer
774 strings---this saves space!
776 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
777 well shouldn't be yanked on, but if one is, then you will get a
778 friendly message from @absentErr@ (rather than a totally random
781 @parError@ is a special version of @error@ which the compiler does
782 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
783 templates, but we don't ever expect to generate code for it.
787 = pc_bottoming_Id errorIdKey pREL_ERR SLIT("error") errorTy
789 = generic_ERROR_ID patErrorIdKey SLIT("patError")
791 = generic_ERROR_ID recSelErrIdKey SLIT("recSelError")
793 = generic_ERROR_ID recConErrorIdKey SLIT("recConError")
795 = generic_ERROR_ID recUpdErrorIdKey SLIT("recUpdError")
797 = generic_ERROR_ID irrefutPatErrorIdKey SLIT("irrefutPatError")
798 nON_EXHAUSTIVE_GUARDS_ERROR_ID
799 = generic_ERROR_ID nonExhaustiveGuardsErrorIdKey SLIT("nonExhaustiveGuardsError")
800 nO_METHOD_BINDING_ERROR_ID
801 = generic_ERROR_ID noMethodBindingErrorIdKey SLIT("noMethodBindingError")
804 = pc_bottoming_Id absentErrorIdKey pREL_ERR SLIT("absentErr")
805 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy)
808 = pcMiscPrelId parErrorIdKey pREL_ERR SLIT("parError")
809 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy) noCafIdInfo
814 %************************************************************************
816 \subsection{Utilities}
818 %************************************************************************
821 pcMiscPrelId :: Unique{-IdKey-} -> Module -> FAST_STRING -> Type -> IdInfo -> Id
822 pcMiscPrelId key mod str ty info
824 name = mkWiredInName mod (mkVarOcc str) key
825 imp = mkId name ty info -- the usual case...
828 -- We lie and say the thing is imported; otherwise, we get into
829 -- a mess with dependency analysis; e.g., core2stg may heave in
830 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
831 -- being compiled, then it's just a matter of luck if the definition
832 -- will be in "the right place" to be in scope.
834 pc_bottoming_Id key mod name ty
835 = pcMiscPrelId key mod name ty bottoming_info
837 bottoming_info = noCafIdInfo
838 `setStrictnessInfo` mkStrictnessInfo ([wwStrict], True)
840 -- these "bottom" out, no matter what their arguments
842 generic_ERROR_ID u n = pc_bottoming_Id u pREL_ERR n errorTy
845 noCafIdInfo = constantIdInfo `setCafInfo` NoCafRefs
847 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
848 openAlphaTy = mkTyVarTy openAlphaTyVar
849 openBetaTy = mkTyVarTy openBetaTyVar
852 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy]
854 -- Notice the openAlphaTyVar. It says that "error" can be applied
855 -- to unboxed as well as boxed types. This is OK because it never
856 -- returns, so the return type is irrelevant.