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,
45 isUnLiftedType, mkForAllTys, mkTyVarTy, tyVarsOfType,
46 splitFunTys, splitForAllTys
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,
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)
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)
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)
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 `setCafInfo` NoCafRefs
243 -- The wrapper Id ends up in STG code as an argument,
244 -- sometimes before its definition, so we want to
245 -- signal that it has no CAFs
246 `setTyGenInfo` TyGenNever
247 -- No point generalising its type, since it gets eagerly inlined
250 wrap_ty = mkForAllTys all_tyvars $
254 cpr_info = idCprInfo work_id
256 wrap_rhs | isNewTyCon tycon
257 = ASSERT( null ex_tyvars && null ex_dict_args && length orig_arg_tys == 1 )
258 -- No existentials on a newtype, but it can have a context
259 -- e.g. newtype Eq a => T a = MkT (...)
261 mkLams tyvars $ mkLams dict_args $ Lam id_arg1 $
262 Note (Coerce result_ty (head orig_arg_tys)) (Var id_arg1)
264 | null dict_args && all not_marked_strict strict_marks
265 = Var work_id -- The common case. Not only is this efficient,
266 -- but it also ensures that the wrapper is replaced
267 -- by the worker even when there are no args.
271 -- This is really important in rule matching,
272 -- (We could match on the wrappers,
273 -- but that makes it less likely that rules will match
274 -- when we bring bits of unfoldings together.)
276 -- NB: because of this special case, (map (:) ys) turns into
277 -- (map $w: ys), and thence into (map (\x xs. $w: x xs) ys)
278 -- in core-to-stg. The top-level defn for (:) is never used.
279 -- This is somewhat of a bore, but I'm currently leaving it
280 -- as is, so that there still is a top level curried (:) for
281 -- the interpreter to call.
284 = mkLams all_tyvars $ mkLams dict_args $
285 mkLams ex_dict_args $ mkLams id_args $
286 foldr mk_case con_app
287 (zip (ex_dict_args++id_args) strict_marks) i3 []
289 con_app i rep_ids = mkApps (Var work_id)
290 (map varToCoreExpr (all_tyvars ++ reverse rep_ids))
292 (tyvars, theta, ex_tyvars, ex_theta, orig_arg_tys, tycon) = dataConSig data_con
293 all_tyvars = tyvars ++ ex_tyvars
295 dict_tys = mkDictTys theta
296 ex_dict_tys = mkDictTys ex_theta
297 all_arg_tys = dict_tys ++ ex_dict_tys ++ orig_arg_tys
298 result_ty = mkTyConApp tycon (mkTyVarTys tyvars)
300 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
304 (dict_args, i1) = mkLocals 1 dict_tys
305 (ex_dict_args,i2) = mkLocals i1 ex_dict_tys
306 (id_args,i3) = mkLocals i2 orig_arg_tys
308 (id_arg1:_) = id_args -- Used for newtype only
310 strict_marks = dataConStrictMarks data_con
311 not_marked_strict NotMarkedStrict = True
312 not_marked_strict other = False
316 :: (Id, StrictnessMark) -- arg, strictness
317 -> (Int -> [Id] -> CoreExpr) -- body
318 -> Int -- next rep arg id
319 -> [Id] -- rep args so far
321 mk_case (arg,strict) body i rep_args
323 NotMarkedStrict -> body i (arg:rep_args)
325 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
327 Case (Var arg) arg [(DEFAULT,[], body i (arg:rep_args))]
329 MarkedUnboxed con tys ->
330 Case (Var arg) arg [(DataAlt con, con_args,
331 body i' (reverse con_args++rep_args))]
333 (con_args,i') = mkLocals i tys
337 %************************************************************************
339 \subsection{Record selectors}
341 %************************************************************************
343 We're going to build a record selector unfolding that looks like this:
345 data T a b c = T1 { ..., op :: a, ...}
346 | T2 { ..., op :: a, ...}
349 sel = /\ a b c -> \ d -> case d of
354 Similarly for newtypes
356 newtype N a = MkN { unN :: a->a }
359 unN n = coerce (a->a) n
361 We need to take a little care if the field has a polymorphic type:
363 data R = R { f :: forall a. a->a }
367 f :: forall a. R -> a -> a
368 f = /\ a \ r = case r of
371 (not f :: R -> forall a. a->a, which gives the type inference mechanism
372 problems at call sites)
374 Similarly for newtypes
376 newtype N = MkN { unN :: forall a. a->a }
378 unN :: forall a. N -> a -> a
379 unN = /\a -> \n:N -> coerce (a->a) n
382 mkRecordSelId tycon field_label unpack_id unpackUtf8_id
383 -- Assumes that all fields with the same field label have the same type
385 -- Annoyingly, we have to pass in the unpackCString# Id, because
386 -- we can't conjure it up out of thin air
389 sel_id = mkId (fieldLabelName field_label) selector_ty info
391 field_ty = fieldLabelType field_label
392 data_cons = tyConDataCons tycon
393 tyvars = tyConTyVars tycon -- These scope over the types in
394 -- the FieldLabels of constructors of this type
395 tycon_theta = tyConTheta tycon -- The context on the data decl
396 -- eg data (Eq a, Ord b) => T a b = ...
397 (field_tyvars,field_tau) = splitForAllTys field_ty
399 data_ty = mkTyConApp tycon tyvar_tys
400 tyvar_tys = mkTyVarTys tyvars
402 -- Very tiresomely, the selectors are (unnecessarily!) overloaded over
403 -- just the dictionaries in the types of the constructors that contain
404 -- the relevant field. Urgh.
405 -- NB: this code relies on the fact that DataCons are quantified over
406 -- the identical type variables as their parent TyCon
407 dict_tys = [mkDictTy cls tys | (cls, tys) <- tycon_theta, needed_dict (cls, tys)]
408 needed_dict pred = or [ pred `elem` (dataConTheta dc)
409 | (DataAlt dc, _, _) <- the_alts]
412 selector_ty = mkForAllTys tyvars $ mkForAllTys field_tyvars $
413 mkFunTys dict_tys $ mkFunTy data_ty field_tau
415 info = mkIdInfo (RecordSelId field_label)
416 `setArityInfo` exactArity (1 + length dict_tys)
417 `setUnfoldingInfo` unfolding
418 `setCafInfo` NoCafRefs
419 `setTyGenInfo` TyGenNever
420 -- ToDo: consider adding further IdInfo
422 unfolding = mkTopUnfolding sel_rhs
425 (data_id:dict_ids) = mkTemplateLocals (data_ty:dict_tys)
426 alts = map mk_maybe_alt data_cons
427 the_alts = catMaybes alts
428 default_alt | all isJust alts = [] -- No default needed
429 | otherwise = [(DEFAULT, [], error_expr)]
431 sel_rhs = mkLams tyvars $ mkLams field_tyvars $
432 mkLams dict_ids $ Lam data_id $
435 sel_body | isNewTyCon tycon = Note (Coerce field_tau data_ty) (Var data_id)
436 | otherwise = Case (Var data_id) data_id (the_alts ++ default_alt)
438 mk_maybe_alt data_con
439 = case maybe_the_arg_id of
441 Just the_arg_id -> Just (DataAlt data_con, real_args, expr)
443 body = mkVarApps (Var the_arg_id) field_tyvars
444 strict_marks = dataConStrictMarks data_con
445 (expr, real_args) = rebuildConArgs data_con arg_ids strict_marks body
448 arg_ids = mkTemplateLocals (dataConInstOrigArgTys data_con tyvar_tys)
449 -- The first one will shadow data_id, but who cares
450 maybe_the_arg_id = assocMaybe (field_lbls `zip` arg_ids) field_label
451 field_lbls = dataConFieldLabels data_con
453 error_expr = mkApps (Var rEC_SEL_ERROR_ID) [Type field_tau, err_string]
455 | all safeChar full_msg
456 = App (Var unpack_id) (Lit (MachStr (_PK_ full_msg)))
458 = App (Var unpackUtf8_id) (Lit (MachStr (_PK_ (stringToUtf8 (map ord full_msg)))))
460 safeChar c = c >= '\1' && c <= '\xFF'
461 -- TODO: Putting this Unicode stuff here is ugly. Find a better
462 -- generic place to make string literals. This logic is repeated
464 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
467 -- this rather ugly function converts the unpacked data con arguments back into
468 -- their packed form. It is almost the same as the version in DsUtils, except that
469 -- we use template locals here rather than newDsId (ToDo: merge these).
472 :: DataCon -- the con we're matching on
473 -> [Id] -- the source-level args
474 -> [StrictnessMark] -- the strictness annotations (per-arg)
475 -> CoreExpr -- the body
476 -> Int -- template local
479 rebuildConArgs con [] stricts body i = (body, [])
480 rebuildConArgs con (arg:args) stricts body i | isTyVar arg
481 = let (body', args') = rebuildConArgs con args stricts body i
483 rebuildConArgs con (arg:args) (str:stricts) body i
484 = case maybeMarkedUnboxed str of
485 Just (pack_con1, _) ->
486 case splitProductType_maybe (idType arg) of
487 Just (_, tycon_args, pack_con, con_arg_tys) ->
488 ASSERT( pack_con == pack_con1 )
489 let unpacked_args = zipWith mkTemplateLocal [i..] con_arg_tys
490 (body', real_args) = rebuildConArgs con args stricts body
491 (i + length con_arg_tys)
494 Let (NonRec arg (mkConApp pack_con
495 (map Type tycon_args ++
496 map Var unpacked_args))) body',
497 unpacked_args ++ real_args
500 _ -> let (body', args') = rebuildConArgs con args stricts body i
501 in (body', arg:args')
505 %************************************************************************
507 \subsection{Dictionary selectors}
509 %************************************************************************
511 Selecting a field for a dictionary. If there is just one field, then
512 there's nothing to do.
514 ToDo: unify with mkRecordSelId.
517 mkDictSelId :: Name -> Class -> Id
518 mkDictSelId name clas
522 sel_id = mkId name ty info
523 field_lbl = mkFieldLabel name tycon ty tag
524 tag = assoc "MkId.mkDictSelId" (classSelIds clas `zip` allFieldLabelTags) sel_id
526 info = mkIdInfo (RecordSelId field_lbl)
527 `setArityInfo` exactArity 1
528 `setUnfoldingInfo` unfolding
529 `setCafInfo` NoCafRefs
530 `setTyGenInfo` TyGenNever
532 -- We no longer use 'must-inline' on record selectors. They'll
533 -- inline like crazy if they scrutinise a constructor
535 unfolding = mkTopUnfolding rhs
537 tyvars = classTyVars clas
539 tycon = classTyCon clas
540 [data_con] = tyConDataCons tycon
541 tyvar_tys = mkTyVarTys tyvars
542 arg_tys = dataConArgTys data_con tyvar_tys
543 the_arg_id = arg_ids !! (tag - firstFieldLabelTag)
545 dict_ty = mkDictTy clas tyvar_tys
546 (dict_id:arg_ids) = mkTemplateLocals (dict_ty : arg_tys)
548 rhs | isNewTyCon tycon = mkLams tyvars $ Lam dict_id $
549 Note (Coerce (head arg_tys) dict_ty) (Var dict_id)
550 | otherwise = mkLams tyvars $ Lam dict_id $
551 Case (Var dict_id) dict_id
552 [(DataAlt data_con, arg_ids, Var the_arg_id)]
556 %************************************************************************
558 \subsection{Primitive operations
560 %************************************************************************
563 mkPrimOpId :: PrimOp -> Id
567 (tyvars,arg_tys,res_ty, arity, strict_info) = primOpSig prim_op
568 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
569 name = mkPrimOpIdName prim_op
570 id = mkId name ty info
572 info = mkIdInfo (PrimOpId prim_op)
574 `setArityInfo` exactArity arity
575 `setStrictnessInfo` strict_info
577 rules = addRule emptyCoreRules id (primOpRule prim_op)
580 -- For each ccall we manufacture a separate CCallOpId, giving it
581 -- a fresh unique, a type that is correct for this particular ccall,
582 -- and a CCall structure that gives the correct details about calling
585 -- The *name* of this Id is a local name whose OccName gives the full
586 -- details of the ccall, type and all. This means that the interface
587 -- file reader can reconstruct a suitable Id
589 mkCCallOpId :: Unique -> CCall -> Type -> Id
590 mkCCallOpId uniq ccall ty
591 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
592 -- A CCallOpId should have no free type variables;
593 -- when doing substitutions won't substitute over it
596 occ_str = showSDocIface (braces (pprCCallOp ccall <+> ppr ty))
597 -- The "occurrence name" of a ccall is the full info about the
598 -- ccall; it is encoded, but may have embedded spaces etc!
600 name = mkCCallName uniq occ_str
601 prim_op = CCallOp ccall
603 info = mkIdInfo (PrimOpId prim_op)
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}
618 %************************************************************************
621 mkDictFunId :: Name -- Name to use for the dict fun;
628 mkDictFunId dfun_name clas inst_tyvars inst_tys dfun_theta
629 = mkId dfun_name dfun_ty info
631 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
632 info = mkIdInfo DictFunId `setTyGenInfo` TyGenNever
633 -- type is wired-in (see comment at TcClassDcl.tcClassSig), so
634 -- do not generalise it
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 = constantIdInfo `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 = constantIdInfo
705 `setUnfoldingInfo` mkCompulsoryUnfolding rhs
706 -- We don't provide a defn for this; you must inline it
708 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy intPrimTy)
709 [x,y] = mkTemplateLocals [alphaTy,alphaTy]
710 rhs = mkLams [alphaTyVar,x] $
711 Case (Var x) y [ (DEFAULT, [], mkApps (Var dataToTagId) [Type alphaTy, Var y]) ]
713 dataToTagId = mkPrimOpId DataToTagOp
716 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
717 nasty as-is, change it back to a literal (@Literal@).
720 realWorldPrimId -- :: State# RealWorld
721 = pcMiscPrelId realWorldPrimIdKey pREL_GHC SLIT("realWorld#")
723 (noCafIdInfo `setUnfoldingInfo` mkOtherCon [])
724 -- The mkOtherCon makes it look that realWorld# is evaluated
725 -- which in turn makes Simplify.interestingArg return True,
726 -- which in turn makes INLINE things applied to realWorld# likely
731 %************************************************************************
733 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
735 %************************************************************************
737 GHC randomly injects these into the code.
739 @patError@ is just a version of @error@ for pattern-matching
740 failures. It knows various ``codes'' which expand to longer
741 strings---this saves space!
743 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
744 well shouldn't be yanked on, but if one is, then you will get a
745 friendly message from @absentErr@ (rather than a totally random
748 @parError@ is a special version of @error@ which the compiler does
749 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
750 templates, but we don't ever expect to generate code for it.
754 = pc_bottoming_Id errorIdKey pREL_ERR SLIT("error") errorTy
756 = generic_ERROR_ID patErrorIdKey SLIT("patError")
758 = generic_ERROR_ID recSelErrIdKey SLIT("recSelError")
760 = generic_ERROR_ID recConErrorIdKey SLIT("recConError")
762 = generic_ERROR_ID recUpdErrorIdKey SLIT("recUpdError")
764 = generic_ERROR_ID irrefutPatErrorIdKey SLIT("irrefutPatError")
765 nON_EXHAUSTIVE_GUARDS_ERROR_ID
766 = generic_ERROR_ID nonExhaustiveGuardsErrorIdKey SLIT("nonExhaustiveGuardsError")
767 nO_METHOD_BINDING_ERROR_ID
768 = generic_ERROR_ID noMethodBindingErrorIdKey SLIT("noMethodBindingError")
771 = pc_bottoming_Id absentErrorIdKey pREL_ERR SLIT("absentErr")
772 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy)
775 = pcMiscPrelId parErrorIdKey pREL_ERR SLIT("parError")
776 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy) noCafIdInfo
781 %************************************************************************
783 \subsection{Utilities}
785 %************************************************************************
788 pcMiscPrelId :: Unique{-IdKey-} -> Module -> FAST_STRING -> Type -> IdInfo -> Id
789 pcMiscPrelId key mod str ty info
791 name = mkWiredInName mod (mkVarOcc str) key
792 imp = mkId name ty info -- the usual case...
795 -- We lie and say the thing is imported; otherwise, we get into
796 -- a mess with dependency analysis; e.g., core2stg may heave in
797 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
798 -- being compiled, then it's just a matter of luck if the definition
799 -- will be in "the right place" to be in scope.
801 pc_bottoming_Id key mod name ty
802 = pcMiscPrelId key mod name ty bottoming_info
804 bottoming_info = noCafIdInfo
805 `setStrictnessInfo` mkStrictnessInfo ([wwStrict], True)
807 -- these "bottom" out, no matter what their arguments
809 generic_ERROR_ID u n = pc_bottoming_Id u pREL_ERR n errorTy
812 noCafIdInfo = constantIdInfo `setCafInfo` NoCafRefs
814 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
815 openAlphaTy = mkTyVarTy openAlphaTyVar
816 openBetaTy = mkTyVarTy openBetaTyVar
819 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy]
821 -- Notice the openAlphaTyVar. It says that "error" can be applied
822 -- to unboxed as well as boxed types. This is OK because it never
823 -- returns, so the return type is irrelevant.