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,
20 mkRecordSelId, rebuildConArgs,
21 mkPrimOpId, mkFCallId,
23 -- And some particular Ids; see below for why they are wired in
25 unsafeCoerceId, realWorldPrimId,
26 eRROR_ID, rEC_SEL_ERROR_ID, pAT_ERROR_ID, rEC_CON_ERROR_ID,
27 rEC_UPD_ERROR_ID, iRREFUT_PAT_ERROR_ID, nON_EXHAUSTIVE_GUARDS_ERROR_ID,
28 nO_METHOD_BINDING_ERROR_ID, aBSENT_ERROR_ID, pAR_ERROR_ID
31 #include "HsVersions.h"
34 import BasicTypes ( Arity )
35 import TysPrim ( openAlphaTyVars, alphaTyVar, alphaTy,
36 intPrimTy, realWorldStatePrimTy
38 import TysWiredIn ( charTy, mkListTy )
39 import PrelNames ( pREL_ERR, pREL_GHC )
40 import PrelRules ( primOpRule )
41 import Rules ( addRule )
42 import Type ( Type, ThetaType, mkDictTy, mkPredTys, mkTyConApp,
43 mkTyVarTys, repType, isNewType,
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, mkFCallName, Name )
58 import OccName ( mkVarOcc )
59 import PrimOp ( PrimOp(DataToTagOp), primOpSig, mkPrimOpIdName )
60 import ForeignCall ( ForeignCall )
61 import Demand ( wwStrict, wwPrim, mkStrictnessInfo,
62 StrictnessMark(..), isMarkedUnboxed, isMarkedStrict )
63 import DataCon ( DataCon,
64 dataConFieldLabels, dataConRepArity, dataConTyCon,
65 dataConArgTys, dataConRepType, dataConRepStrictness,
66 dataConInstOrigArgTys,
67 dataConName, dataConTheta,
68 dataConSig, dataConStrictMarks, dataConId,
71 import Id ( idType, mkGlobalId, mkVanillaGlobal, mkSysLocal,
72 mkTemplateLocals, mkTemplateLocalsNum,
73 mkTemplateLocal, idCprInfo
75 import IdInfo ( IdInfo, noCafNoTyGenIdInfo,
76 exactArity, setUnfoldingInfo, setCprInfo,
77 setArityInfo, setSpecInfo, setCgInfo,
78 mkStrictnessInfo, setStrictnessInfo,
79 GlobalIdDetails(..), CafInfo(..), CprInfo(..),
80 CgInfo(..), setCgArity
82 import FieldLabel ( mkFieldLabel, fieldLabelName,
83 firstFieldLabelTag, allFieldLabelTags, fieldLabelType
86 import Unique ( mkBuiltinUnique )
89 import Maybe ( isJust )
91 import ListSetOps ( assoc, assocMaybe )
92 import UnicodeUtil ( stringToUtf8 )
96 %************************************************************************
98 \subsection{Wired in Ids}
100 %************************************************************************
104 = [ -- These error-y things are wired in because we don't yet have
105 -- a way to express in an interface file that the result type variable
106 -- is 'open'; that is can be unified with an unboxed type
108 -- [The interface file format now carry such information, but there's
109 -- no way yet of expressing at the definition site for these
111 -- functions that they have an 'open' result type. -- sof 1/99]
115 , iRREFUT_PAT_ERROR_ID
116 , nON_EXHAUSTIVE_GUARDS_ERROR_ID
117 , nO_METHOD_BINDING_ERROR_ID
123 -- These three can't be defined in Haskell
130 %************************************************************************
132 \subsection{Data constructors}
134 %************************************************************************
137 mkDataConId :: Name -> DataCon -> Id
138 -- Makes the *worker* for the data constructor; that is, the function
139 -- that takes the reprsentation arguments and builds the constructor.
140 mkDataConId work_name data_con
141 = mkGlobalId (DataConId data_con) work_name (dataConRepType data_con) info
143 info = noCafNoTyGenIdInfo
145 `setArityInfo` exactArity arity
146 `setStrictnessInfo` strict_info
147 `setCprInfo` cpr_info
149 arity = dataConRepArity data_con
151 strict_info = mkStrictnessInfo (dataConRepStrictness data_con, False)
153 tycon = dataConTyCon data_con
154 cpr_info | isProductTyCon tycon &&
157 arity <= mAX_CPR_SIZE = ReturnsCPR
158 | otherwise = NoCPRInfo
159 -- ReturnsCPR is only true for products that are real data types;
160 -- that is, not unboxed tuples or newtypes
162 mAX_CPR_SIZE :: Arity
164 -- We do not treat very big tuples as CPR-ish:
165 -- a) for a start we get into trouble because there aren't
166 -- "enough" unboxed tuple types (a tiresome restriction,
168 -- b) more importantly, big unboxed tuples get returned mainly
169 -- on the stack, and are often then allocated in the heap
170 -- by the caller. So doing CPR for them may in fact make
174 The wrapper for a constructor is an ordinary top-level binding that evaluates
175 any strict args, unboxes any args that are going to be flattened, and calls
178 We're going to build a constructor that looks like:
180 data (Data a, C b) => T a b = T1 !a !Int b
183 \d1::Data a, d2::C b ->
184 \p q r -> case p of { p ->
186 Con T1 [a,b] [p,q,r]}}
190 * d2 is thrown away --- a context in a data decl is used to make sure
191 one *could* construct dictionaries at the site the constructor
192 is used, but the dictionary isn't actually used.
194 * We have to check that we can construct Data dictionaries for
195 the types a and Int. Once we've done that we can throw d1 away too.
197 * We use (case p of q -> ...) to evaluate p, rather than "seq" because
198 all that matters is that the arguments are evaluated. "seq" is
199 very careful to preserve evaluation order, which we don't need
202 You might think that we could simply give constructors some strictness
203 info, like PrimOps, and let CoreToStg do the let-to-case transformation.
204 But we don't do that because in the case of primops and functions strictness
205 is a *property* not a *requirement*. In the case of constructors we need to
206 do something active to evaluate the argument.
208 Making an explicit case expression allows the simplifier to eliminate
209 it in the (common) case where the constructor arg is already evaluated.
212 mkDataConWrapId data_con
215 wrap_id = mkGlobalId (DataConWrapId data_con) (dataConName data_con) wrap_ty info
216 work_id = dataConId data_con
218 info = noCafNoTyGenIdInfo
219 `setUnfoldingInfo` mkTopUnfolding (mkInlineMe wrap_rhs)
220 `setCprInfo` cpr_info
221 -- The Cpr info can be important inside INLINE rhss, where the
222 -- wrapper constructor isn't inlined
224 -- The NoCaf-ness is set by noCafNoTyGenIdInfo
225 `setArityInfo` exactArity arity
226 -- It's important to specify the arity, so that partial
227 -- applications are treated as values
229 wrap_ty = mkForAllTys all_tyvars $
233 cpr_info = idCprInfo work_id
235 wrap_rhs | isNewTyCon tycon
236 = ASSERT( null ex_tyvars && null ex_dict_args && length orig_arg_tys == 1 )
237 -- No existentials on a newtype, but it can have a context
238 -- e.g. newtype Eq a => T a = MkT (...)
240 mkLams tyvars $ mkLams dict_args $ Lam id_arg1 $
241 Note (Coerce result_ty (head orig_arg_tys)) (Var id_arg1)
243 | null dict_args && not (any isMarkedStrict strict_marks)
244 = Var work_id -- The common case. Not only is this efficient,
245 -- but it also ensures that the wrapper is replaced
246 -- by the worker even when there are no args.
250 -- This is really important in rule matching,
251 -- (We could match on the wrappers,
252 -- but that makes it less likely that rules will match
253 -- when we bring bits of unfoldings together.)
255 -- NB: because of this special case, (map (:) ys) turns into
256 -- (map $w: ys), and thence into (map (\x xs. $w: x xs) ys)
257 -- in core-to-stg. The top-level defn for (:) is never used.
258 -- This is somewhat of a bore, but I'm currently leaving it
259 -- as is, so that there still is a top level curried (:) for
260 -- the interpreter to call.
263 = mkLams all_tyvars $ mkLams dict_args $
264 mkLams ex_dict_args $ mkLams id_args $
265 foldr mk_case con_app
266 (zip (ex_dict_args++id_args) strict_marks) i3 []
268 con_app i rep_ids = mkApps (Var work_id)
269 (map varToCoreExpr (all_tyvars ++ reverse rep_ids))
271 (tyvars, theta, ex_tyvars, ex_theta, orig_arg_tys, tycon) = dataConSig data_con
272 all_tyvars = tyvars ++ ex_tyvars
274 dict_tys = mkPredTys theta
275 ex_dict_tys = mkPredTys ex_theta
276 all_arg_tys = dict_tys ++ ex_dict_tys ++ orig_arg_tys
277 result_ty = mkTyConApp tycon (mkTyVarTys tyvars)
279 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
283 (dict_args, i1) = mkLocals 1 dict_tys
284 (ex_dict_args,i2) = mkLocals i1 ex_dict_tys
285 (id_args,i3) = mkLocals i2 orig_arg_tys
287 (id_arg1:_) = id_args -- Used for newtype only
289 strict_marks = dataConStrictMarks data_con
292 :: (Id, StrictnessMark) -- Arg, strictness
293 -> (Int -> [Id] -> CoreExpr) -- Body
294 -> Int -- Next rep arg id
295 -> [Id] -- Rep args so far, reversed
297 mk_case (arg,strict) body i rep_args
299 NotMarkedStrict -> body i (arg:rep_args)
301 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
303 Case (Var arg) arg [(DEFAULT,[], body i (arg:rep_args))]
306 | isNewType arg_ty ->
307 Let (NonRec coerced_arg
308 (Note (Coerce rep_ty arg_ty) (Var arg)))
309 (do_unbox coerced_arg rep_ty i')
311 do_unbox arg arg_ty i
313 ([coerced_arg],i') = mkLocals i [rep_ty]
315 rep_ty = repType arg_ty
318 case splitProductType "do_unbox" ty of
319 (tycon, tycon_args, con, tys) ->
320 Case (Var arg) arg [(DataAlt con, con_args,
321 body i' (reverse con_args ++ rep_args))]
323 (con_args, i') = mkLocals i tys
327 %************************************************************************
329 \subsection{Record selectors}
331 %************************************************************************
333 We're going to build a record selector unfolding that looks like this:
335 data T a b c = T1 { ..., op :: a, ...}
336 | T2 { ..., op :: a, ...}
339 sel = /\ a b c -> \ d -> case d of
344 Similarly for newtypes
346 newtype N a = MkN { unN :: a->a }
349 unN n = coerce (a->a) n
351 We need to take a little care if the field has a polymorphic type:
353 data R = R { f :: forall a. a->a }
357 f :: forall a. R -> a -> a
358 f = /\ a \ r = case r of
361 (not f :: R -> forall a. a->a, which gives the type inference mechanism
362 problems at call sites)
364 Similarly for newtypes
366 newtype N = MkN { unN :: forall a. a->a }
368 unN :: forall a. N -> a -> a
369 unN = /\a -> \n:N -> coerce (a->a) n
372 mkRecordSelId tycon field_label unpack_id unpackUtf8_id
373 -- Assumes that all fields with the same field label have the same type
375 -- Annoyingly, we have to pass in the unpackCString# Id, because
376 -- we can't conjure it up out of thin air
379 sel_id = mkGlobalId (RecordSelId field_label) (fieldLabelName field_label) selector_ty info
380 field_ty = fieldLabelType field_label
381 data_cons = tyConDataCons tycon
382 tyvars = tyConTyVars tycon -- These scope over the types in
383 -- the FieldLabels of constructors of this type
384 data_ty = mkTyConApp tycon tyvar_tys
385 tyvar_tys = mkTyVarTys tyvars
387 tycon_theta = tyConTheta tycon -- The context on the data decl
388 -- eg data (Eq a, Ord b) => T a b = ...
389 dict_tys = [mkPredTy pred | pred <- tycon_theta,
391 needed_dict pred = or [ pred `elem` (dataConTheta dc)
392 | (DataAlt dc, _, _) <- the_alts]
393 n_dict_tys = length dict_tys
395 (field_tyvars,field_theta,field_tau) = splitSigmaTy field_ty
396 field_dict_tys = map mkPredTy field_theta
397 n_field_dict_tys = length field_dict_tys
398 -- If the field has a universally quantified type we have to
399 -- be a bit careful. Suppose we have
400 -- data R = R { op :: forall a. Foo a => a -> a }
401 -- Then we can't give op the type
402 -- op :: R -> forall a. Foo a => a -> a
403 -- because the typechecker doesn't understand foralls to the
404 -- right of an arrow. The "right" type to give it is
405 -- op :: forall a. Foo a => R -> a -> a
406 -- But then we must generate the right unfolding too:
407 -- op = /\a -> \dfoo -> \ r ->
410 -- Note that this is exactly the type we'd infer from a user defn
413 -- Very tiresomely, the selectors are (unnecessarily!) overloaded over
414 -- just the dictionaries in the types of the constructors that contain
415 -- the relevant field. Urgh.
416 -- NB: this code relies on the fact that DataCons are quantified over
417 -- the identical type variables as their parent TyCon
420 selector_ty = mkForAllTys tyvars $ mkForAllTys field_tyvars $
421 mkFunTys dict_tys $ mkFunTys field_dict_tys $
422 mkFunTy data_ty field_tau
424 arity = 1 + n_dict_tys + n_field_dict_tys
425 info = noCafNoTyGenIdInfo
426 `setCgInfo` (CgInfo arity caf_info)
427 `setArityInfo` exactArity arity
428 `setUnfoldingInfo` unfolding
429 -- ToDo: consider adding further IdInfo
431 unfolding = mkTopUnfolding sel_rhs
433 -- Allocate Ids. We do it a funny way round because field_dict_tys is
434 -- almost always empty. Also note that we use length_tycon_theta
435 -- rather than n_dict_tys, because the latter gives an infinite loop:
436 -- n_dict tys depends on the_alts, which depens on arg_ids, which depends
437 -- on arity, which depends on n_dict tys. Sigh! Mega sigh!
438 field_dict_base = length tycon_theta + 1
439 dict_id_base = field_dict_base + n_field_dict_tys
440 field_base = dict_id_base + 1
441 dict_ids = mkTemplateLocalsNum 1 dict_tys
442 field_dict_ids = mkTemplateLocalsNum field_dict_base field_dict_tys
443 data_id = mkTemplateLocal dict_id_base data_ty
445 alts = map mk_maybe_alt data_cons
446 the_alts = catMaybes alts
448 no_default = all isJust alts -- No default needed
449 default_alt | no_default = []
450 | otherwise = [(DEFAULT, [], error_expr)]
452 -- the default branch may have CAF refs, because it calls recSelError etc.
453 caf_info | no_default = NoCafRefs
454 | otherwise = MayHaveCafRefs
456 sel_rhs = mkLams tyvars $ mkLams field_tyvars $
457 mkLams dict_ids $ mkLams field_dict_ids $
458 Lam data_id $ sel_body
460 sel_body | isNewTyCon tycon = Note (Coerce field_tau data_ty) (Var data_id)
461 | otherwise = Case (Var data_id) data_id (the_alts ++ default_alt)
463 mk_maybe_alt data_con
464 = case maybe_the_arg_id of
466 Just the_arg_id -> Just (DataAlt data_con, real_args, mkLets binds body)
468 body = mkVarApps (mkVarApps (Var the_arg_id) field_tyvars) field_dict_ids
469 strict_marks = dataConStrictMarks data_con
470 (binds, real_args) = rebuildConArgs arg_ids strict_marks
471 (map mkBuiltinUnique [unpack_base..])
473 arg_ids = mkTemplateLocalsNum field_base (dataConInstOrigArgTys data_con tyvar_tys)
475 unpack_base = field_base + length arg_ids
477 -- arity+1 avoids all shadowing
478 maybe_the_arg_id = assocMaybe (field_lbls `zip` arg_ids) field_label
479 field_lbls = dataConFieldLabels data_con
481 error_expr = mkApps (Var rEC_SEL_ERROR_ID) [Type field_tau, err_string]
483 | all safeChar full_msg
484 = App (Var unpack_id) (Lit (MachStr (_PK_ full_msg)))
486 = App (Var unpackUtf8_id) (Lit (MachStr (_PK_ (stringToUtf8 (map ord full_msg)))))
488 safeChar c = c >= '\1' && c <= '\xFF'
489 -- TODO: Putting this Unicode stuff here is ugly. Find a better
490 -- generic place to make string literals. This logic is repeated
492 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
495 -- This rather ugly function converts the unpacked data con
496 -- arguments back into their packed form.
499 :: [Id] -- Source-level args
500 -> [StrictnessMark] -- Strictness annotations (per-arg)
501 -> [Unique] -- Uniques for the new Ids
502 -> ([CoreBind], [Id]) -- A binding for each source-level arg, plus
503 -- a list of the representation-level arguments
504 -- e.g. data T = MkT Int !Int
506 -- rebuild [x::Int, y::Int] [Not, Unbox]
507 -- = ([ y = I# t ], [x,t])
509 rebuildConArgs [] stricts us = ([], [])
511 -- Type variable case
512 rebuildConArgs (arg:args) stricts us
514 = let (binds, args') = rebuildConArgs args stricts us
515 in (binds, arg:args')
517 -- Term variable case
518 rebuildConArgs (arg:args) (str:stricts) us
519 | isMarkedUnboxed str
522 prod_ty | isNewType arg_ty = repType arg_ty
525 (_, tycon_args, pack_con, con_arg_tys)
526 = splitProductType "rebuildConArgs" prod_ty
528 unpacked_args = zipWith (mkSysLocal SLIT("rb")) us con_arg_tys
530 (binds, args') = rebuildConArgs args stricts
531 (drop (length con_arg_tys) us)
533 coerce | isNewType arg_ty = Note (Coerce arg_ty prod_ty) con_app
534 | otherwise = con_app
536 con_app = mkConApp pack_con (map Type tycon_args ++
537 map Var unpacked_args)
539 (NonRec arg coerce : binds, unpacked_args ++ args')
542 = let (binds, args') = rebuildConArgs args stricts us
543 in (binds, arg:args')
547 %************************************************************************
549 \subsection{Dictionary selectors}
551 %************************************************************************
553 Selecting a field for a dictionary. If there is just one field, then
554 there's nothing to do.
556 ToDo: unify with mkRecordSelId.
559 mkDictSelId :: Name -> Class -> Id
560 mkDictSelId name clas
564 sel_id = mkGlobalId (RecordSelId field_lbl) name ty info
565 field_lbl = mkFieldLabel name tycon ty tag
566 tag = assoc "MkId.mkDictSelId" (classSelIds clas `zip` allFieldLabelTags) sel_id
568 info = noCafNoTyGenIdInfo
570 `setArityInfo` exactArity 1
571 `setUnfoldingInfo` unfolding
573 -- We no longer use 'must-inline' on record selectors. They'll
574 -- inline like crazy if they scrutinise a constructor
576 unfolding = mkTopUnfolding rhs
578 tyvars = classTyVars clas
580 tycon = classTyCon clas
581 [data_con] = tyConDataCons tycon
582 tyvar_tys = mkTyVarTys tyvars
583 arg_tys = dataConArgTys data_con tyvar_tys
584 the_arg_id = arg_ids !! (tag - firstFieldLabelTag)
586 dict_ty = mkDictTy clas tyvar_tys
587 (dict_id:arg_ids) = mkTemplateLocals (dict_ty : arg_tys)
589 rhs | isNewTyCon tycon = mkLams tyvars $ Lam dict_id $
590 Note (Coerce (head arg_tys) dict_ty) (Var dict_id)
591 | otherwise = mkLams tyvars $ Lam dict_id $
592 Case (Var dict_id) dict_id
593 [(DataAlt data_con, arg_ids, Var the_arg_id)]
597 %************************************************************************
599 \subsection{Primitive operations
601 %************************************************************************
604 mkPrimOpId :: PrimOp -> Id
608 (tyvars,arg_tys,res_ty, arity, strict_info) = primOpSig prim_op
609 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
610 name = mkPrimOpIdName prim_op
611 id = mkGlobalId (PrimOpId prim_op) name ty info
613 info = noCafNoTyGenIdInfo
616 `setArityInfo` exactArity arity
617 `setStrictnessInfo` strict_info
619 rules = maybe emptyCoreRules (addRule emptyCoreRules id)
623 -- For each ccall we manufacture a separate CCallOpId, giving it
624 -- a fresh unique, a type that is correct for this particular ccall,
625 -- and a CCall structure that gives the correct details about calling
628 -- The *name* of this Id is a local name whose OccName gives the full
629 -- details of the ccall, type and all. This means that the interface
630 -- file reader can reconstruct a suitable Id
632 mkFCallId :: Unique -> ForeignCall -> Type -> Id
633 mkFCallId uniq fcall ty
634 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
635 -- A CCallOpId should have no free type variables;
636 -- when doing substitutions won't substitute over it
637 mkGlobalId (FCallId fcall) name ty info
639 occ_str = showSDocIface (braces (ppr fcall <+> ppr ty))
640 -- The "occurrence name" of a ccall is the full info about the
641 -- ccall; it is encoded, but may have embedded spaces etc!
643 name = mkFCallName uniq occ_str
645 info = noCafNoTyGenIdInfo
647 `setArityInfo` exactArity arity
648 `setStrictnessInfo` strict_info
650 (_, tau) = splitForAllTys ty
651 (arg_tys, _) = splitFunTys tau
652 arity = length arg_tys
653 strict_info = mkStrictnessInfo (take arity (repeat wwPrim), False)
657 %************************************************************************
659 \subsection{DictFuns and default methods}
661 %************************************************************************
664 mkDefaultMethodId dm_name ty
665 = mkVanillaGlobal dm_name ty noCafNoTyGenIdInfo
667 mkDictFunId :: Name -- Name to use for the dict fun;
674 mkDictFunId dfun_name clas inst_tyvars inst_tys dfun_theta
675 = mkVanillaGlobal dfun_name dfun_ty noCafNoTyGenIdInfo
677 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
679 {- 1 dec 99: disable the Mark Jones optimisation for the sake
680 of compatibility with Hugs.
681 See `types/InstEnv' for a discussion related to this.
683 (class_tyvars, sc_theta, _, _) = classBigSig clas
684 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
685 sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys) sc_theta
686 dfun_theta = case inst_decl_theta of
687 [] -> [] -- If inst_decl_theta is empty, then we don't
688 -- want to have any dict arguments, so that we can
689 -- expose the constant methods.
691 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
692 -- Otherwise we pass the superclass dictionaries to
693 -- the dictionary function; the Mark Jones optimisation.
695 -- NOTE the "nub". I got caught by this one:
696 -- class Monad m => MonadT t m where ...
697 -- instance Monad m => MonadT (EnvT env) m where ...
698 -- Here, the inst_decl_theta has (Monad m); but so
699 -- does the sc_theta'!
701 -- NOTE the "not_const". I got caught by this one too:
702 -- class Foo a => Baz a b where ...
703 -- instance Wob b => Baz T b where..
704 -- Now sc_theta' has Foo T
709 %************************************************************************
711 \subsection{Un-definable}
713 %************************************************************************
715 These two can't be defined in Haskell.
717 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
718 just gets expanded into a type coercion wherever it occurs. Hence we
719 add it as a built-in Id with an unfolding here.
721 The type variables we use here are "open" type variables: this means
722 they can unify with both unlifted and lifted types. Hence we provide
723 another gun with which to shoot yourself in the foot.
727 = pcMiscPrelId unsafeCoerceIdKey pREL_GHC SLIT("unsafeCoerce#") ty info
729 info = noCafNoTyGenIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
732 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
733 (mkFunTy openAlphaTy openBetaTy)
734 [x] = mkTemplateLocals [openAlphaTy]
735 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
736 Note (Coerce openBetaTy openAlphaTy) (Var x)
740 @getTag#@ is another function which can't be defined in Haskell. It needs to
741 evaluate its argument and call the dataToTag# primitive.
745 = pcMiscPrelId getTagIdKey pREL_GHC SLIT("getTag#") ty info
747 info = noCafNoTyGenIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
748 -- We don't provide a defn for this; you must inline it
750 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy intPrimTy)
751 [x,y] = mkTemplateLocals [alphaTy,alphaTy]
752 rhs = mkLams [alphaTyVar,x] $
753 Case (Var x) y [ (DEFAULT, [], mkApps (Var dataToTagId) [Type alphaTy, Var y]) ]
755 dataToTagId = mkPrimOpId DataToTagOp
758 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
759 nasty as-is, change it back to a literal (@Literal@).
762 realWorldPrimId -- :: State# RealWorld
763 = pcMiscPrelId realWorldPrimIdKey pREL_GHC SLIT("realWorld#")
765 (noCafNoTyGenIdInfo `setUnfoldingInfo` mkOtherCon [])
766 -- The mkOtherCon makes it look that realWorld# is evaluated
767 -- which in turn makes Simplify.interestingArg return True,
768 -- which in turn makes INLINE things applied to realWorld# likely
773 %************************************************************************
775 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
777 %************************************************************************
779 GHC randomly injects these into the code.
781 @patError@ is just a version of @error@ for pattern-matching
782 failures. It knows various ``codes'' which expand to longer
783 strings---this saves space!
785 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
786 well shouldn't be yanked on, but if one is, then you will get a
787 friendly message from @absentErr@ (rather than a totally random
790 @parError@ is a special version of @error@ which the compiler does
791 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
792 templates, but we don't ever expect to generate code for it.
796 = pc_bottoming_Id errorIdKey pREL_ERR SLIT("error") errorTy
798 = generic_ERROR_ID patErrorIdKey SLIT("patError")
800 = generic_ERROR_ID recSelErrIdKey SLIT("recSelError")
802 = generic_ERROR_ID recConErrorIdKey SLIT("recConError")
804 = generic_ERROR_ID recUpdErrorIdKey SLIT("recUpdError")
806 = generic_ERROR_ID irrefutPatErrorIdKey SLIT("irrefutPatError")
807 nON_EXHAUSTIVE_GUARDS_ERROR_ID
808 = generic_ERROR_ID nonExhaustiveGuardsErrorIdKey SLIT("nonExhaustiveGuardsError")
809 nO_METHOD_BINDING_ERROR_ID
810 = generic_ERROR_ID noMethodBindingErrorIdKey SLIT("noMethodBindingError")
813 = pc_bottoming_Id absentErrorIdKey pREL_ERR SLIT("absentErr")
814 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy)
817 = pcMiscPrelId parErrorIdKey pREL_ERR SLIT("parError")
818 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy) noCafNoTyGenIdInfo
822 %************************************************************************
824 \subsection{Utilities}
826 %************************************************************************
829 pcMiscPrelId :: Unique{-IdKey-} -> Module -> FAST_STRING -> Type -> IdInfo -> Id
830 pcMiscPrelId key mod str ty info
832 name = mkWiredInName mod (mkVarOcc str) key
833 imp = mkVanillaGlobal name ty info -- the usual case...
836 -- We lie and say the thing is imported; otherwise, we get into
837 -- a mess with dependency analysis; e.g., core2stg may heave in
838 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
839 -- being compiled, then it's just a matter of luck if the definition
840 -- will be in "the right place" to be in scope.
842 pc_bottoming_Id key mod name ty
843 = pcMiscPrelId key mod name ty bottoming_info
845 bottoming_info = noCafNoTyGenIdInfo
846 `setStrictnessInfo` mkStrictnessInfo ([wwStrict], True)
848 -- these "bottom" out, no matter what their arguments
850 generic_ERROR_ID u n = pc_bottoming_Id u pREL_ERR n errorTy
852 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
853 openAlphaTy = mkTyVarTy openAlphaTyVar
854 openBetaTy = mkTyVarTy openBetaTyVar
857 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy]
859 -- Notice the openAlphaTyVar. It says that "error" can be applied
860 -- to unboxed as well as boxed types. This is OK because it never
861 -- returns, so the return type is irrelevant.