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, StrictnessMark(..), isMarkedUnboxed, isMarkedStrict )
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 TcType ( Type, ThetaType, mkDictTy, mkPredTys, mkTyConApp,
43 mkTyVarTys, mkClassPred, tcEqPred,
44 mkFunTys, mkFunTy, mkSigmaTy, tcSplitSigmaTy,
45 isUnLiftedType, mkForAllTys, mkTyVarTy, tyVarsOfType,
46 tcSplitFunTys, tcSplitForAllTys, 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, isRecursiveTyCon )
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 DataCon ( DataCon,
62 dataConFieldLabels, dataConRepArity, dataConTyCon,
63 dataConArgTys, dataConRepType, dataConRepStrictness,
64 dataConInstOrigArgTys,
65 dataConName, dataConTheta,
66 dataConSig, dataConStrictMarks, dataConId,
69 import Id ( idType, mkGlobalId, mkVanillaGlobal, mkSysLocal,
70 mkTemplateLocals, mkTemplateLocalsNum,
71 mkTemplateLocal, idNewStrictness, idName
73 import IdInfo ( IdInfo, noCafNoTyGenIdInfo,
74 exactArity, setUnfoldingInfo, setCprInfo,
75 setArityInfo, setSpecInfo, setCgInfo,
76 mkNewStrictnessInfo, setNewStrictnessInfo,
77 GlobalIdDetails(..), CafInfo(..), CprInfo(..),
78 CgInfo(..), setCgArity
80 import NewDemand ( mkStrictSig, strictSigResInfo, DmdResult(..),
81 mkTopDmdType, topDmd, evalDmd )
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
143 id = mkGlobalId (DataConId data_con) work_name (dataConRepType data_con) info
144 info = noCafNoTyGenIdInfo
147 `setNewStrictnessInfo` Just strict_sig
149 arity = dataConRepArity data_con
150 strict_sig = mkStrictSig id arity (mkTopDmdType (dataConRepStrictness data_con) cpr_info)
152 tycon = dataConTyCon data_con
153 cpr_info | isProductTyCon tycon &&
156 arity <= mAX_CPR_SIZE = RetCPR
158 -- RetCPR is only true for products that are real data types;
159 -- that is, not unboxed tuples or [non-recursive] newtypes
161 mAX_CPR_SIZE :: Arity
163 -- We do not treat very big tuples as CPR-ish:
164 -- a) for a start we get into trouble because there aren't
165 -- "enough" unboxed tuple types (a tiresome restriction,
167 -- b) more importantly, big unboxed tuples get returned mainly
168 -- on the stack, and are often then allocated in the heap
169 -- by the caller. So doing CPR for them may in fact make
173 The wrapper for a constructor is an ordinary top-level binding that evaluates
174 any strict args, unboxes any args that are going to be flattened, and calls
177 We're going to build a constructor that looks like:
179 data (Data a, C b) => T a b = T1 !a !Int b
182 \d1::Data a, d2::C b ->
183 \p q r -> case p of { p ->
185 Con T1 [a,b] [p,q,r]}}
189 * d2 is thrown away --- a context in a data decl is used to make sure
190 one *could* construct dictionaries at the site the constructor
191 is used, but the dictionary isn't actually used.
193 * We have to check that we can construct Data dictionaries for
194 the types a and Int. Once we've done that we can throw d1 away too.
196 * We use (case p of q -> ...) to evaluate p, rather than "seq" because
197 all that matters is that the arguments are evaluated. "seq" is
198 very careful to preserve evaluation order, which we don't need
201 You might think that we could simply give constructors some strictness
202 info, like PrimOps, and let CoreToStg do the let-to-case transformation.
203 But we don't do that because in the case of primops and functions strictness
204 is a *property* not a *requirement*. In the case of constructors we need to
205 do something active to evaluate the argument.
207 Making an explicit case expression allows the simplifier to eliminate
208 it in the (common) case where the constructor arg is already evaluated.
211 mkDataConWrapId data_con
214 wrap_id = mkGlobalId (DataConWrapId data_con) (dataConName data_con) wrap_ty info
215 work_id = dataConId data_con
217 info = noCafNoTyGenIdInfo
218 `setUnfoldingInfo` mkTopUnfolding (mkInlineMe wrap_rhs)
220 -- The NoCaf-ness is set by noCafNoTyGenIdInfo
222 -- It's important to specify the arity, so that partial
223 -- applications are treated as values
224 `setNewStrictnessInfo` Just wrap_sig
226 wrap_ty = mkForAllTys all_tyvars $
230 res_info = strictSigResInfo (idNewStrictness work_id)
231 wrap_sig = mkStrictSig wrap_id arity (mkTopDmdType (replicate arity topDmd) res_info)
232 -- The Cpr info can be important inside INLINE rhss, where the
233 -- wrapper constructor isn't inlined
234 -- But we are sloppy about the argument demands, because we expect
235 -- to inline the constructor very vigorously.
237 wrap_rhs | isNewTyCon tycon
238 = ASSERT( null ex_tyvars && null ex_dict_args && length orig_arg_tys == 1 )
239 -- No existentials on a newtype, but it can have a context
240 -- e.g. newtype Eq a => T a = MkT (...)
241 mkLams tyvars $ mkLams dict_args $ Lam id_arg1 $
242 mkNewTypeBody tycon result_ty id_arg1
244 | null dict_args && not (any isMarkedStrict strict_marks)
245 = Var work_id -- The common case. Not only is this efficient,
246 -- but it also ensures that the wrapper is replaced
247 -- by the worker even when there are no args.
251 -- This is really important in rule matching,
252 -- (We could match on the wrappers,
253 -- but that makes it less likely that rules will match
254 -- when we bring bits of unfoldings together.)
256 -- NB: because of this special case, (map (:) ys) turns into
257 -- (map $w: ys), and thence into (map (\x xs. $w: x xs) ys)
258 -- in core-to-stg. The top-level defn for (:) is never used.
259 -- This is somewhat of a bore, but I'm currently leaving it
260 -- as is, so that there still is a top level curried (:) for
261 -- the interpreter to call.
264 = mkLams all_tyvars $ mkLams dict_args $
265 mkLams ex_dict_args $ mkLams id_args $
266 foldr mk_case con_app
267 (zip (ex_dict_args++id_args) strict_marks) i3 []
269 con_app i rep_ids = mkApps (Var work_id)
270 (map varToCoreExpr (all_tyvars ++ reverse rep_ids))
272 (tyvars, theta, ex_tyvars, ex_theta, orig_arg_tys, tycon) = dataConSig data_con
273 all_tyvars = tyvars ++ ex_tyvars
275 dict_tys = mkPredTys theta
276 ex_dict_tys = mkPredTys ex_theta
277 all_arg_tys = dict_tys ++ ex_dict_tys ++ orig_arg_tys
278 result_ty = mkTyConApp tycon (mkTyVarTys tyvars)
280 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
284 (dict_args, i1) = mkLocals 1 dict_tys
285 (ex_dict_args,i2) = mkLocals i1 ex_dict_tys
286 (id_args,i3) = mkLocals i2 orig_arg_tys
288 (id_arg1:_) = id_args -- Used for newtype only
290 strict_marks = dataConStrictMarks data_con
293 :: (Id, StrictnessMark) -- Arg, strictness
294 -> (Int -> [Id] -> CoreExpr) -- Body
295 -> Int -- Next rep arg id
296 -> [Id] -- Rep args so far, reversed
298 mk_case (arg,strict) body i rep_args
300 NotMarkedStrict -> body i (arg:rep_args)
302 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
304 Case (Var arg) arg [(DEFAULT,[], body i (arg:rep_args))]
307 -> case splitProductType "do_unbox" (idType arg) of
308 (tycon, tycon_args, con, tys) ->
309 Case (Var arg) arg [(DataAlt con, con_args,
310 body i' (reverse con_args ++ rep_args))]
312 (con_args, i') = mkLocals i tys
316 %************************************************************************
318 \subsection{Record selectors}
320 %************************************************************************
322 We're going to build a record selector unfolding that looks like this:
324 data T a b c = T1 { ..., op :: a, ...}
325 | T2 { ..., op :: a, ...}
328 sel = /\ a b c -> \ d -> case d of
333 Similarly for newtypes
335 newtype N a = MkN { unN :: a->a }
338 unN n = coerce (a->a) n
340 We need to take a little care if the field has a polymorphic type:
342 data R = R { f :: forall a. a->a }
346 f :: forall a. R -> a -> a
347 f = /\ a \ r = case r of
350 (not f :: R -> forall a. a->a, which gives the type inference mechanism
351 problems at call sites)
353 Similarly for newtypes
355 newtype N = MkN { unN :: forall a. a->a }
357 unN :: forall a. N -> a -> a
358 unN = /\a -> \n:N -> coerce (a->a) n
361 mkRecordSelId tycon field_label unpack_id unpackUtf8_id
362 -- Assumes that all fields with the same field label have the same type
364 -- Annoyingly, we have to pass in the unpackCString# Id, because
365 -- we can't conjure it up out of thin air
368 sel_id = mkGlobalId (RecordSelId field_label) (fieldLabelName field_label) selector_ty info
369 field_ty = fieldLabelType field_label
370 data_cons = tyConDataCons tycon
371 tyvars = tyConTyVars tycon -- These scope over the types in
372 -- the FieldLabels of constructors of this type
373 data_ty = mkTyConApp tycon tyvar_tys
374 tyvar_tys = mkTyVarTys tyvars
376 tycon_theta = tyConTheta tycon -- The context on the data decl
377 -- eg data (Eq a, Ord b) => T a b = ...
378 dict_tys = [mkPredTy pred | pred <- tycon_theta,
380 needed_dict pred = or [ tcEqPred pred p
381 | (DataAlt dc, _, _) <- the_alts, p <- dataConTheta dc]
382 n_dict_tys = length dict_tys
384 (field_tyvars,field_theta,field_tau) = tcSplitSigmaTy field_ty
385 field_dict_tys = map mkPredTy field_theta
386 n_field_dict_tys = length field_dict_tys
387 -- If the field has a universally quantified type we have to
388 -- be a bit careful. Suppose we have
389 -- data R = R { op :: forall a. Foo a => a -> a }
390 -- Then we can't give op the type
391 -- op :: R -> forall a. Foo a => a -> a
392 -- because the typechecker doesn't understand foralls to the
393 -- right of an arrow. The "right" type to give it is
394 -- op :: forall a. Foo a => R -> a -> a
395 -- But then we must generate the right unfolding too:
396 -- op = /\a -> \dfoo -> \ r ->
399 -- Note that this is exactly the type we'd infer from a user defn
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
409 selector_ty = mkForAllTys tyvars $ mkForAllTys field_tyvars $
410 mkFunTys dict_tys $ mkFunTys field_dict_tys $
411 mkFunTy data_ty field_tau
413 arity = 1 + n_dict_tys + n_field_dict_tys
414 info = noCafNoTyGenIdInfo
415 `setCgInfo` (CgInfo arity caf_info)
417 `setUnfoldingInfo` unfolding
418 -- ToDo: consider adding further IdInfo
420 unfolding = mkTopUnfolding sel_rhs
422 -- Allocate Ids. We do it a funny way round because field_dict_tys is
423 -- almost always empty. Also note that we use length_tycon_theta
424 -- rather than n_dict_tys, because the latter gives an infinite loop:
425 -- n_dict tys depends on the_alts, which depens on arg_ids, which depends
426 -- on arity, which depends on n_dict tys. Sigh! Mega sigh!
427 field_dict_base = length tycon_theta + 1
428 dict_id_base = field_dict_base + n_field_dict_tys
429 field_base = dict_id_base + 1
430 dict_ids = mkTemplateLocalsNum 1 dict_tys
431 field_dict_ids = mkTemplateLocalsNum field_dict_base field_dict_tys
432 data_id = mkTemplateLocal dict_id_base data_ty
434 alts = map mk_maybe_alt data_cons
435 the_alts = catMaybes alts
437 no_default = all isJust alts -- No default needed
438 default_alt | no_default = []
439 | otherwise = [(DEFAULT, [], error_expr)]
441 -- the default branch may have CAF refs, because it calls recSelError etc.
442 caf_info | no_default = NoCafRefs
443 | otherwise = MayHaveCafRefs
445 sel_rhs = mkLams tyvars $ mkLams field_tyvars $
446 mkLams dict_ids $ mkLams field_dict_ids $
447 Lam data_id $ sel_body
449 sel_body | isNewTyCon tycon = mkNewTypeBody tycon field_tau data_id
450 | otherwise = Case (Var data_id) data_id (default_alt ++ the_alts)
452 mk_maybe_alt data_con
453 = case maybe_the_arg_id of
455 Just the_arg_id -> Just (DataAlt data_con, real_args, mkLets binds body)
457 body = mkVarApps (mkVarApps (Var the_arg_id) field_tyvars) field_dict_ids
458 strict_marks = dataConStrictMarks data_con
459 (binds, real_args) = rebuildConArgs arg_ids strict_marks
460 (map mkBuiltinUnique [unpack_base..])
462 arg_ids = mkTemplateLocalsNum field_base (dataConInstOrigArgTys data_con tyvar_tys)
464 unpack_base = field_base + length arg_ids
466 -- arity+1 avoids all shadowing
467 maybe_the_arg_id = assocMaybe (field_lbls `zip` arg_ids) field_label
468 field_lbls = dataConFieldLabels data_con
470 error_expr = mkApps (Var rEC_SEL_ERROR_ID) [Type field_tau, err_string]
472 | all safeChar full_msg
473 = App (Var unpack_id) (Lit (MachStr (_PK_ full_msg)))
475 = App (Var unpackUtf8_id) (Lit (MachStr (_PK_ (stringToUtf8 (map ord full_msg)))))
477 safeChar c = c >= '\1' && c <= '\xFF'
478 -- TODO: Putting this Unicode stuff here is ugly. Find a better
479 -- generic place to make string literals. This logic is repeated
481 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
484 -- This rather ugly function converts the unpacked data con
485 -- arguments back into their packed form.
488 :: [Id] -- Source-level args
489 -> [StrictnessMark] -- Strictness annotations (per-arg)
490 -> [Unique] -- Uniques for the new Ids
491 -> ([CoreBind], [Id]) -- A binding for each source-level arg, plus
492 -- a list of the representation-level arguments
493 -- e.g. data T = MkT Int !Int
495 -- rebuild [x::Int, y::Int] [Not, Unbox]
496 -- = ([ y = I# t ], [x,t])
498 rebuildConArgs [] stricts us = ([], [])
500 -- Type variable case
501 rebuildConArgs (arg:args) stricts us
503 = let (binds, args') = rebuildConArgs args stricts us
504 in (binds, arg:args')
506 -- Term variable case
507 rebuildConArgs (arg:args) (str:stricts) us
508 | isMarkedUnboxed str
512 (_, tycon_args, pack_con, con_arg_tys)
513 = splitProductType "rebuildConArgs" arg_ty
515 unpacked_args = zipWith (mkSysLocal SLIT("rb")) us con_arg_tys
516 (binds, args') = rebuildConArgs args stricts (drop (length con_arg_tys) us)
517 con_app = mkConApp pack_con (map Type tycon_args ++ map Var unpacked_args)
519 (NonRec arg con_app : binds, unpacked_args ++ args')
522 = let (binds, args') = rebuildConArgs args stricts us
523 in (binds, arg:args')
527 %************************************************************************
529 \subsection{Dictionary selectors}
531 %************************************************************************
533 Selecting a field for a dictionary. If there is just one field, then
534 there's nothing to do.
536 ToDo: unify with mkRecordSelId.
539 mkDictSelId :: Name -> Class -> Id
540 mkDictSelId name clas
541 = mkGlobalId (RecordSelId field_lbl) name sel_ty info
543 sel_ty = mkForAllTys tyvars (mkFunTy (idType dict_id) (idType the_arg_id))
544 -- We can't just say (exprType rhs), because that would give a type
546 -- for a single-op class (after all, the selector is the identity)
547 -- But it's type must expose the representation of the dictionary
548 -- to gat (say) C a -> (a -> a)
550 field_lbl = mkFieldLabel name tycon sel_ty tag
551 tag = assoc "MkId.mkDictSelId" (map idName (classSelIds clas) `zip` allFieldLabelTags) name
553 info = noCafNoTyGenIdInfo
556 `setUnfoldingInfo` unfolding
558 -- We no longer use 'must-inline' on record selectors. They'll
559 -- inline like crazy if they scrutinise a constructor
561 unfolding = mkTopUnfolding rhs
563 tyvars = classTyVars clas
565 tycon = classTyCon clas
566 [data_con] = tyConDataCons tycon
567 tyvar_tys = mkTyVarTys tyvars
568 arg_tys = dataConArgTys data_con tyvar_tys
569 the_arg_id = arg_ids !! (tag - firstFieldLabelTag)
571 pred = mkClassPred clas tyvar_tys
572 (dict_id:arg_ids) = mkTemplateLocals (mkPredTy pred : arg_tys)
574 rhs | isNewTyCon tycon = mkLams tyvars $ Lam dict_id $
575 mkNewTypeBody tycon (head arg_tys) dict_id
576 | otherwise = mkLams tyvars $ Lam dict_id $
577 Case (Var dict_id) dict_id
578 [(DataAlt data_con, arg_ids, Var the_arg_id)]
580 mkNewTypeBody tycon result_ty result_id
581 | isRecursiveTyCon tycon -- Recursive case; use a coerce
582 = Note (Coerce result_ty (idType result_id)) (Var result_id)
583 | otherwise -- Normal case
588 %************************************************************************
590 \subsection{Primitive operations
592 %************************************************************************
595 mkPrimOpId :: PrimOp -> Id
599 (tyvars,arg_tys,res_ty, arity, strict_info) = primOpSig prim_op
600 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
601 name = mkPrimOpIdName prim_op
602 id = mkGlobalId (PrimOpId prim_op) name ty info
604 info = noCafNoTyGenIdInfo
608 `setNewStrictnessInfo` Just (mkNewStrictnessInfo id arity strict_info NoCPRInfo)
609 -- Until we modify the primop generation code
611 rules = maybe emptyCoreRules (addRule emptyCoreRules id)
615 -- For each ccall we manufacture a separate CCallOpId, giving it
616 -- a fresh unique, a type that is correct for this particular ccall,
617 -- and a CCall structure that gives the correct details about calling
620 -- The *name* of this Id is a local name whose OccName gives the full
621 -- details of the ccall, type and all. This means that the interface
622 -- file reader can reconstruct a suitable Id
624 mkFCallId :: Unique -> ForeignCall -> Type -> Id
625 mkFCallId uniq fcall ty
626 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
627 -- A CCallOpId should have no free type variables;
628 -- when doing substitutions won't substitute over it
631 id = mkGlobalId (FCallId fcall) name ty info
632 occ_str = showSDocIface (braces (ppr fcall <+> ppr ty))
633 -- The "occurrence name" of a ccall is the full info about the
634 -- ccall; it is encoded, but may have embedded spaces etc!
636 name = mkFCallName uniq occ_str
638 info = noCafNoTyGenIdInfo
641 `setNewStrictnessInfo` Just strict_sig
643 (_, tau) = tcSplitForAllTys ty
644 (arg_tys, _) = tcSplitFunTys tau
645 arity = length arg_tys
646 strict_sig = mkStrictSig id arity (mkTopDmdType (replicate arity evalDmd) TopRes)
650 %************************************************************************
652 \subsection{DictFuns and default methods}
654 %************************************************************************
657 mkDefaultMethodId dm_name ty
658 = mkVanillaGlobal dm_name ty noCafNoTyGenIdInfo
660 mkDictFunId :: Name -- Name to use for the dict fun;
667 mkDictFunId dfun_name clas inst_tyvars inst_tys dfun_theta
668 = mkVanillaGlobal dfun_name dfun_ty noCafNoTyGenIdInfo
670 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
672 {- 1 dec 99: disable the Mark Jones optimisation for the sake
673 of compatibility with Hugs.
674 See `types/InstEnv' for a discussion related to this.
676 (class_tyvars, sc_theta, _, _) = classBigSig clas
677 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
678 sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys) sc_theta
679 dfun_theta = case inst_decl_theta of
680 [] -> [] -- If inst_decl_theta is empty, then we don't
681 -- want to have any dict arguments, so that we can
682 -- expose the constant methods.
684 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
685 -- Otherwise we pass the superclass dictionaries to
686 -- the dictionary function; the Mark Jones optimisation.
688 -- NOTE the "nub". I got caught by this one:
689 -- class Monad m => MonadT t m where ...
690 -- instance Monad m => MonadT (EnvT env) m where ...
691 -- Here, the inst_decl_theta has (Monad m); but so
692 -- does the sc_theta'!
694 -- NOTE the "not_const". I got caught by this one too:
695 -- class Foo a => Baz a b where ...
696 -- instance Wob b => Baz T b where..
697 -- Now sc_theta' has Foo T
702 %************************************************************************
704 \subsection{Un-definable}
706 %************************************************************************
708 These two can't be defined in Haskell.
710 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
711 just gets expanded into a type coercion wherever it occurs. Hence we
712 add it as a built-in Id with an unfolding here.
714 The type variables we use here are "open" type variables: this means
715 they can unify with both unlifted and lifted types. Hence we provide
716 another gun with which to shoot yourself in the foot.
720 = pcMiscPrelId unsafeCoerceIdKey pREL_GHC SLIT("unsafeCoerce#") ty info
722 info = noCafNoTyGenIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
725 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
726 (mkFunTy openAlphaTy openBetaTy)
727 [x] = mkTemplateLocals [openAlphaTy]
728 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
729 Note (Coerce openBetaTy openAlphaTy) (Var x)
733 @getTag#@ is another function which can't be defined in Haskell. It needs to
734 evaluate its argument and call the dataToTag# primitive.
738 = pcMiscPrelId getTagIdKey pREL_GHC SLIT("getTag#") ty info
740 info = noCafNoTyGenIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
741 -- We don't provide a defn for this; you must inline it
743 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy intPrimTy)
744 [x,y] = mkTemplateLocals [alphaTy,alphaTy]
745 rhs = mkLams [alphaTyVar,x] $
746 Case (Var x) y [ (DEFAULT, [], mkApps (Var dataToTagId) [Type alphaTy, Var y]) ]
748 dataToTagId = mkPrimOpId DataToTagOp
751 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
752 nasty as-is, change it back to a literal (@Literal@).
755 realWorldPrimId -- :: State# RealWorld
756 = pcMiscPrelId realWorldPrimIdKey pREL_GHC SLIT("realWorld#")
758 (noCafNoTyGenIdInfo `setUnfoldingInfo` mkOtherCon [])
759 -- The mkOtherCon makes it look that realWorld# is evaluated
760 -- which in turn makes Simplify.interestingArg return True,
761 -- which in turn makes INLINE things applied to realWorld# likely
766 %************************************************************************
768 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
770 %************************************************************************
772 GHC randomly injects these into the code.
774 @patError@ is just a version of @error@ for pattern-matching
775 failures. It knows various ``codes'' which expand to longer
776 strings---this saves space!
778 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
779 well shouldn't be yanked on, but if one is, then you will get a
780 friendly message from @absentErr@ (rather than a totally random
783 @parError@ is a special version of @error@ which the compiler does
784 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
785 templates, but we don't ever expect to generate code for it.
789 = pc_bottoming_Id errorIdKey pREL_ERR SLIT("error") errorTy
791 = generic_ERROR_ID patErrorIdKey SLIT("patError")
793 = generic_ERROR_ID recSelErrIdKey SLIT("recSelError")
795 = generic_ERROR_ID recConErrorIdKey SLIT("recConError")
797 = generic_ERROR_ID recUpdErrorIdKey SLIT("recUpdError")
799 = generic_ERROR_ID irrefutPatErrorIdKey SLIT("irrefutPatError")
800 nON_EXHAUSTIVE_GUARDS_ERROR_ID
801 = generic_ERROR_ID nonExhaustiveGuardsErrorIdKey SLIT("nonExhaustiveGuardsError")
802 nO_METHOD_BINDING_ERROR_ID
803 = generic_ERROR_ID noMethodBindingErrorIdKey SLIT("noMethodBindingError")
806 = pc_bottoming_Id absentErrorIdKey pREL_ERR SLIT("absentErr")
807 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy)
810 = pcMiscPrelId parErrorIdKey pREL_ERR SLIT("parError")
811 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy) noCafNoTyGenIdInfo
815 %************************************************************************
817 \subsection{Utilities}
819 %************************************************************************
822 pcMiscPrelId :: Unique{-IdKey-} -> Module -> FAST_STRING -> Type -> IdInfo -> Id
823 pcMiscPrelId key mod str ty info
825 name = mkWiredInName mod (mkVarOcc str) key
826 imp = mkVanillaGlobal name ty info -- the usual case...
829 -- We lie and say the thing is imported; otherwise, we get into
830 -- a mess with dependency analysis; e.g., core2stg may heave in
831 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
832 -- being compiled, then it's just a matter of luck if the definition
833 -- will be in "the right place" to be in scope.
835 pc_bottoming_Id key mod name ty
838 id = pcMiscPrelId key mod name ty bottoming_info
840 strict_sig = mkStrictSig id arity (mkTopDmdType [evalDmd] BotRes)
841 bottoming_info = noCafNoTyGenIdInfo `setNewStrictnessInfo` Just strict_sig
842 -- these "bottom" out, no matter what their arguments
844 generic_ERROR_ID u n = pc_bottoming_Id u pREL_ERR n errorTy
846 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
847 openAlphaTy = mkTyVarTy openAlphaTyVar
848 openBetaTy = mkTyVarTy openBetaTyVar
851 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy]
853 -- Notice the openAlphaTyVar. It says that "error" can be applied
854 -- to unboxed as well as boxed types. This is OK because it never
855 -- returns, so the return type is irrelevant.