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 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 Demand ( wwStrict, wwPrim, mkStrictnessInfo, noStrictnessInfo,
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, idName
75 import IdInfo ( IdInfo, noCafNoTyGenIdInfo,
76 exactArity, setUnfoldingInfo, setCprInfo,
77 setArityInfo, setSpecInfo, setCgInfo,
79 mkNewStrictnessInfo, setNewStrictnessInfo,
80 GlobalIdDetails(..), CafInfo(..), CprInfo(..),
81 CgInfo(..), setCgArity
83 import FieldLabel ( mkFieldLabel, fieldLabelName,
84 firstFieldLabelTag, allFieldLabelTags, fieldLabelType
87 import Unique ( mkBuiltinUnique )
90 import Maybe ( isJust )
92 import ListSetOps ( assoc, assocMaybe )
93 import UnicodeUtil ( stringToUtf8 )
97 %************************************************************************
99 \subsection{Wired in Ids}
101 %************************************************************************
105 = [ -- These error-y things are wired in because we don't yet have
106 -- a way to express in an interface file that the result type variable
107 -- is 'open'; that is can be unified with an unboxed type
109 -- [The interface file format now carry such information, but there's
110 -- no way yet of expressing at the definition site for these
112 -- functions that they have an 'open' result type. -- sof 1/99]
116 , iRREFUT_PAT_ERROR_ID
117 , nON_EXHAUSTIVE_GUARDS_ERROR_ID
118 , nO_METHOD_BINDING_ERROR_ID
124 -- These three can't be defined in Haskell
131 %************************************************************************
133 \subsection{Data constructors}
135 %************************************************************************
138 mkDataConId :: Name -> DataCon -> Id
139 -- Makes the *worker* for the data constructor; that is, the function
140 -- that takes the reprsentation arguments and builds the constructor.
141 mkDataConId work_name data_con
144 id = mkGlobalId (DataConId data_con) work_name (dataConRepType data_con) info
145 info = noCafNoTyGenIdInfo
147 `setArityInfo` exactArity arity
148 `setCprInfo` cpr_info
149 `setStrictnessInfo` strict_info
150 `setNewStrictnessInfo` mkNewStrictnessInfo id arity strict_info cpr_info
152 arity = dataConRepArity data_con
153 strict_info = mkStrictnessInfo (dataConRepStrictness data_con, False)
155 tycon = dataConTyCon data_con
156 cpr_info | isProductTyCon tycon &&
159 arity <= mAX_CPR_SIZE = ReturnsCPR
160 | otherwise = NoCPRInfo
161 -- ReturnsCPR is only true for products that are real data types;
162 -- that is, not unboxed tuples or [non-recursive] newtypes
164 mAX_CPR_SIZE :: Arity
166 -- We do not treat very big tuples as CPR-ish:
167 -- a) for a start we get into trouble because there aren't
168 -- "enough" unboxed tuple types (a tiresome restriction,
170 -- b) more importantly, big unboxed tuples get returned mainly
171 -- on the stack, and are often then allocated in the heap
172 -- by the caller. So doing CPR for them may in fact make
176 The wrapper for a constructor is an ordinary top-level binding that evaluates
177 any strict args, unboxes any args that are going to be flattened, and calls
180 We're going to build a constructor that looks like:
182 data (Data a, C b) => T a b = T1 !a !Int b
185 \d1::Data a, d2::C b ->
186 \p q r -> case p of { p ->
188 Con T1 [a,b] [p,q,r]}}
192 * d2 is thrown away --- a context in a data decl is used to make sure
193 one *could* construct dictionaries at the site the constructor
194 is used, but the dictionary isn't actually used.
196 * We have to check that we can construct Data dictionaries for
197 the types a and Int. Once we've done that we can throw d1 away too.
199 * We use (case p of q -> ...) to evaluate p, rather than "seq" because
200 all that matters is that the arguments are evaluated. "seq" is
201 very careful to preserve evaluation order, which we don't need
204 You might think that we could simply give constructors some strictness
205 info, like PrimOps, and let CoreToStg do the let-to-case transformation.
206 But we don't do that because in the case of primops and functions strictness
207 is a *property* not a *requirement*. In the case of constructors we need to
208 do something active to evaluate the argument.
210 Making an explicit case expression allows the simplifier to eliminate
211 it in the (common) case where the constructor arg is already evaluated.
214 mkDataConWrapId data_con
217 wrap_id = mkGlobalId (DataConWrapId data_con) (dataConName data_con) wrap_ty info
218 work_id = dataConId data_con
220 info = noCafNoTyGenIdInfo
221 `setUnfoldingInfo` mkTopUnfolding (mkInlineMe wrap_rhs)
222 `setCprInfo` cpr_info
223 -- The Cpr info can be important inside INLINE rhss, where the
224 -- wrapper constructor isn't inlined
226 -- The NoCaf-ness is set by noCafNoTyGenIdInfo
227 `setArityInfo` exactArity arity
228 -- It's important to specify the arity, so that partial
229 -- applications are treated as values
230 `setNewStrictnessInfo` mkNewStrictnessInfo wrap_id arity noStrictnessInfo cpr_info
232 wrap_ty = mkForAllTys all_tyvars $
236 cpr_info = idCprInfo work_id
238 wrap_rhs | isNewTyCon tycon
239 = ASSERT( null ex_tyvars && null ex_dict_args && length orig_arg_tys == 1 )
240 -- No existentials on a newtype, but it can have a context
241 -- e.g. newtype Eq a => T a = MkT (...)
242 mkLams tyvars $ mkLams dict_args $ Lam id_arg1 $
243 mkNewTypeBody tycon result_ty id_arg1
245 | null dict_args && not (any isMarkedStrict strict_marks)
246 = Var work_id -- The common case. Not only is this efficient,
247 -- but it also ensures that the wrapper is replaced
248 -- by the worker even when there are no args.
252 -- This is really important in rule matching,
253 -- (We could match on the wrappers,
254 -- but that makes it less likely that rules will match
255 -- when we bring bits of unfoldings together.)
257 -- NB: because of this special case, (map (:) ys) turns into
258 -- (map $w: ys), and thence into (map (\x xs. $w: x xs) ys)
259 -- in core-to-stg. The top-level defn for (:) is never used.
260 -- This is somewhat of a bore, but I'm currently leaving it
261 -- as is, so that there still is a top level curried (:) for
262 -- the interpreter to call.
265 = mkLams all_tyvars $ mkLams dict_args $
266 mkLams ex_dict_args $ mkLams id_args $
267 foldr mk_case con_app
268 (zip (ex_dict_args++id_args) strict_marks) i3 []
270 con_app i rep_ids = mkApps (Var work_id)
271 (map varToCoreExpr (all_tyvars ++ reverse rep_ids))
273 (tyvars, theta, ex_tyvars, ex_theta, orig_arg_tys, tycon) = dataConSig data_con
274 all_tyvars = tyvars ++ ex_tyvars
276 dict_tys = mkPredTys theta
277 ex_dict_tys = mkPredTys ex_theta
278 all_arg_tys = dict_tys ++ ex_dict_tys ++ orig_arg_tys
279 result_ty = mkTyConApp tycon (mkTyVarTys tyvars)
281 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
285 (dict_args, i1) = mkLocals 1 dict_tys
286 (ex_dict_args,i2) = mkLocals i1 ex_dict_tys
287 (id_args,i3) = mkLocals i2 orig_arg_tys
289 (id_arg1:_) = id_args -- Used for newtype only
291 strict_marks = dataConStrictMarks data_con
294 :: (Id, StrictnessMark) -- Arg, strictness
295 -> (Int -> [Id] -> CoreExpr) -- Body
296 -> Int -- Next rep arg id
297 -> [Id] -- Rep args so far, reversed
299 mk_case (arg,strict) body i rep_args
301 NotMarkedStrict -> body i (arg:rep_args)
303 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
305 Case (Var arg) arg [(DEFAULT,[], body i (arg:rep_args))]
308 -> case splitProductType "do_unbox" (idType arg) of
309 (tycon, tycon_args, con, tys) ->
310 Case (Var arg) arg [(DataAlt con, con_args,
311 body i' (reverse con_args ++ rep_args))]
313 (con_args, i') = mkLocals i tys
317 %************************************************************************
319 \subsection{Record selectors}
321 %************************************************************************
323 We're going to build a record selector unfolding that looks like this:
325 data T a b c = T1 { ..., op :: a, ...}
326 | T2 { ..., op :: a, ...}
329 sel = /\ a b c -> \ d -> case d of
334 Similarly for newtypes
336 newtype N a = MkN { unN :: a->a }
339 unN n = coerce (a->a) n
341 We need to take a little care if the field has a polymorphic type:
343 data R = R { f :: forall a. a->a }
347 f :: forall a. R -> a -> a
348 f = /\ a \ r = case r of
351 (not f :: R -> forall a. a->a, which gives the type inference mechanism
352 problems at call sites)
354 Similarly for newtypes
356 newtype N = MkN { unN :: forall a. a->a }
358 unN :: forall a. N -> a -> a
359 unN = /\a -> \n:N -> coerce (a->a) n
362 mkRecordSelId tycon field_label unpack_id unpackUtf8_id
363 -- Assumes that all fields with the same field label have the same type
365 -- Annoyingly, we have to pass in the unpackCString# Id, because
366 -- we can't conjure it up out of thin air
369 sel_id = mkGlobalId (RecordSelId field_label) (fieldLabelName field_label) selector_ty info
370 field_ty = fieldLabelType field_label
371 data_cons = tyConDataCons tycon
372 tyvars = tyConTyVars tycon -- These scope over the types in
373 -- the FieldLabels of constructors of this type
374 data_ty = mkTyConApp tycon tyvar_tys
375 tyvar_tys = mkTyVarTys tyvars
377 tycon_theta = tyConTheta tycon -- The context on the data decl
378 -- eg data (Eq a, Ord b) => T a b = ...
379 dict_tys = [mkPredTy pred | pred <- tycon_theta,
381 needed_dict pred = or [ tcEqPred pred p
382 | (DataAlt dc, _, _) <- the_alts, p <- dataConTheta dc]
383 n_dict_tys = length dict_tys
385 (field_tyvars,field_theta,field_tau) = tcSplitSigmaTy field_ty
386 field_dict_tys = map mkPredTy field_theta
387 n_field_dict_tys = length field_dict_tys
388 -- If the field has a universally quantified type we have to
389 -- be a bit careful. Suppose we have
390 -- data R = R { op :: forall a. Foo a => a -> a }
391 -- Then we can't give op the type
392 -- op :: R -> forall a. Foo a => a -> a
393 -- because the typechecker doesn't understand foralls to the
394 -- right of an arrow. The "right" type to give it is
395 -- op :: forall a. Foo a => R -> a -> a
396 -- But then we must generate the right unfolding too:
397 -- op = /\a -> \dfoo -> \ r ->
400 -- Note that this is exactly the type we'd infer from a user defn
403 -- Very tiresomely, the selectors are (unnecessarily!) overloaded over
404 -- just the dictionaries in the types of the constructors that contain
405 -- the relevant field. Urgh.
406 -- NB: this code relies on the fact that DataCons are quantified over
407 -- the identical type variables as their parent TyCon
410 selector_ty = mkForAllTys tyvars $ mkForAllTys field_tyvars $
411 mkFunTys dict_tys $ mkFunTys field_dict_tys $
412 mkFunTy data_ty field_tau
414 arity = 1 + n_dict_tys + n_field_dict_tys
415 info = noCafNoTyGenIdInfo
416 `setCgInfo` (CgInfo arity caf_info)
417 `setArityInfo` exactArity arity
418 `setUnfoldingInfo` unfolding
419 -- ToDo: consider adding further IdInfo
421 unfolding = mkTopUnfolding sel_rhs
423 -- Allocate Ids. We do it a funny way round because field_dict_tys is
424 -- almost always empty. Also note that we use length_tycon_theta
425 -- rather than n_dict_tys, because the latter gives an infinite loop:
426 -- n_dict tys depends on the_alts, which depens on arg_ids, which depends
427 -- on arity, which depends on n_dict tys. Sigh! Mega sigh!
428 field_dict_base = length tycon_theta + 1
429 dict_id_base = field_dict_base + n_field_dict_tys
430 field_base = dict_id_base + 1
431 dict_ids = mkTemplateLocalsNum 1 dict_tys
432 field_dict_ids = mkTemplateLocalsNum field_dict_base field_dict_tys
433 data_id = mkTemplateLocal dict_id_base data_ty
435 alts = map mk_maybe_alt data_cons
436 the_alts = catMaybes alts
438 no_default = all isJust alts -- No default needed
439 default_alt | no_default = []
440 | otherwise = [(DEFAULT, [], error_expr)]
442 -- the default branch may have CAF refs, because it calls recSelError etc.
443 caf_info | no_default = NoCafRefs
444 | otherwise = MayHaveCafRefs
446 sel_rhs = mkLams tyvars $ mkLams field_tyvars $
447 mkLams dict_ids $ mkLams field_dict_ids $
448 Lam data_id $ sel_body
450 sel_body | isNewTyCon tycon = mkNewTypeBody tycon field_tau data_id
451 | otherwise = Case (Var data_id) data_id (default_alt ++ the_alts)
453 mk_maybe_alt data_con
454 = case maybe_the_arg_id of
456 Just the_arg_id -> Just (DataAlt data_con, real_args, mkLets binds body)
458 body = mkVarApps (mkVarApps (Var the_arg_id) field_tyvars) field_dict_ids
459 strict_marks = dataConStrictMarks data_con
460 (binds, real_args) = rebuildConArgs arg_ids strict_marks
461 (map mkBuiltinUnique [unpack_base..])
463 arg_ids = mkTemplateLocalsNum field_base (dataConInstOrigArgTys data_con tyvar_tys)
465 unpack_base = field_base + length arg_ids
467 -- arity+1 avoids all shadowing
468 maybe_the_arg_id = assocMaybe (field_lbls `zip` arg_ids) field_label
469 field_lbls = dataConFieldLabels data_con
471 error_expr = mkApps (Var rEC_SEL_ERROR_ID) [Type field_tau, err_string]
473 | all safeChar full_msg
474 = App (Var unpack_id) (Lit (MachStr (_PK_ full_msg)))
476 = App (Var unpackUtf8_id) (Lit (MachStr (_PK_ (stringToUtf8 (map ord full_msg)))))
478 safeChar c = c >= '\1' && c <= '\xFF'
479 -- TODO: Putting this Unicode stuff here is ugly. Find a better
480 -- generic place to make string literals. This logic is repeated
482 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
485 -- This rather ugly function converts the unpacked data con
486 -- arguments back into their packed form.
489 :: [Id] -- Source-level args
490 -> [StrictnessMark] -- Strictness annotations (per-arg)
491 -> [Unique] -- Uniques for the new Ids
492 -> ([CoreBind], [Id]) -- A binding for each source-level arg, plus
493 -- a list of the representation-level arguments
494 -- e.g. data T = MkT Int !Int
496 -- rebuild [x::Int, y::Int] [Not, Unbox]
497 -- = ([ y = I# t ], [x,t])
499 rebuildConArgs [] stricts us = ([], [])
501 -- Type variable case
502 rebuildConArgs (arg:args) stricts us
504 = let (binds, args') = rebuildConArgs args stricts us
505 in (binds, arg:args')
507 -- Term variable case
508 rebuildConArgs (arg:args) (str:stricts) us
509 | isMarkedUnboxed str
513 (_, tycon_args, pack_con, con_arg_tys)
514 = splitProductType "rebuildConArgs" arg_ty
516 unpacked_args = zipWith (mkSysLocal SLIT("rb")) us con_arg_tys
517 (binds, args') = rebuildConArgs args stricts (drop (length con_arg_tys) us)
518 con_app = mkConApp pack_con (map Type tycon_args ++ map Var unpacked_args)
520 (NonRec arg con_app : binds, unpacked_args ++ args')
523 = let (binds, args') = rebuildConArgs args stricts us
524 in (binds, arg:args')
528 %************************************************************************
530 \subsection{Dictionary selectors}
532 %************************************************************************
534 Selecting a field for a dictionary. If there is just one field, then
535 there's nothing to do.
537 ToDo: unify with mkRecordSelId.
540 mkDictSelId :: Name -> Class -> Id
541 mkDictSelId name clas
542 = mkGlobalId (RecordSelId field_lbl) name sel_ty info
544 sel_ty = mkForAllTys tyvars (mkFunTy (idType dict_id) (idType the_arg_id))
545 -- We can't just say (exprType rhs), because that would give a type
547 -- for a single-op class (after all, the selector is the identity)
548 -- But it's type must expose the representation of the dictionary
549 -- to gat (say) C a -> (a -> a)
551 field_lbl = mkFieldLabel name tycon sel_ty tag
552 tag = assoc "MkId.mkDictSelId" (map idName (classSelIds clas) `zip` allFieldLabelTags) name
554 info = noCafNoTyGenIdInfo
556 `setArityInfo` exactArity 1
557 `setUnfoldingInfo` unfolding
559 -- We no longer use 'must-inline' on record selectors. They'll
560 -- inline like crazy if they scrutinise a constructor
562 unfolding = mkTopUnfolding rhs
564 tyvars = classTyVars clas
566 tycon = classTyCon clas
567 [data_con] = tyConDataCons tycon
568 tyvar_tys = mkTyVarTys tyvars
569 arg_tys = dataConArgTys data_con tyvar_tys
570 the_arg_id = arg_ids !! (tag - firstFieldLabelTag)
572 pred = mkClassPred clas tyvar_tys
573 (dict_id:arg_ids) = mkTemplateLocals (mkPredTy pred : arg_tys)
575 rhs | isNewTyCon tycon = mkLams tyvars $ Lam dict_id $
576 mkNewTypeBody tycon (head arg_tys) dict_id
577 | otherwise = mkLams tyvars $ Lam dict_id $
578 Case (Var dict_id) dict_id
579 [(DataAlt data_con, arg_ids, Var the_arg_id)]
581 mkNewTypeBody tycon result_ty result_id
582 | isRecursiveTyCon tycon -- Recursive case; use a coerce
583 = Note (Coerce result_ty (idType result_id)) (Var result_id)
584 | otherwise -- Normal case
589 %************************************************************************
591 \subsection{Primitive operations
593 %************************************************************************
596 mkPrimOpId :: PrimOp -> Id
600 (tyvars,arg_tys,res_ty, arity, strict_info) = primOpSig prim_op
601 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
602 name = mkPrimOpIdName prim_op
603 id = mkGlobalId (PrimOpId prim_op) name ty info
605 info = noCafNoTyGenIdInfo
608 `setArityInfo` exactArity arity
609 `setStrictnessInfo` strict_info
610 `setNewStrictnessInfo` mkNewStrictnessInfo id arity strict_info NoCPRInfo
612 rules = maybe emptyCoreRules (addRule emptyCoreRules id)
616 -- For each ccall we manufacture a separate CCallOpId, giving it
617 -- a fresh unique, a type that is correct for this particular ccall,
618 -- and a CCall structure that gives the correct details about calling
621 -- The *name* of this Id is a local name whose OccName gives the full
622 -- details of the ccall, type and all. This means that the interface
623 -- file reader can reconstruct a suitable Id
625 mkFCallId :: Unique -> ForeignCall -> Type -> Id
626 mkFCallId uniq fcall ty
627 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
628 -- A CCallOpId should have no free type variables;
629 -- when doing substitutions won't substitute over it
632 id = mkGlobalId (FCallId fcall) name ty info
633 occ_str = showSDocIface (braces (ppr fcall <+> ppr ty))
634 -- The "occurrence name" of a ccall is the full info about the
635 -- ccall; it is encoded, but may have embedded spaces etc!
637 name = mkFCallName uniq occ_str
639 info = noCafNoTyGenIdInfo
641 `setArityInfo` exactArity arity
642 `setStrictnessInfo` strict_info
643 `setNewStrictnessInfo` mkNewStrictnessInfo id arity strict_info NoCPRInfo
645 (_, tau) = tcSplitForAllTys ty
646 (arg_tys, _) = tcSplitFunTys tau
647 arity = length arg_tys
648 strict_info = mkStrictnessInfo (take arity (repeat wwPrim), False)
652 %************************************************************************
654 \subsection{DictFuns and default methods}
656 %************************************************************************
659 mkDefaultMethodId dm_name ty
660 = mkVanillaGlobal dm_name ty noCafNoTyGenIdInfo
662 mkDictFunId :: Name -- Name to use for the dict fun;
669 mkDictFunId dfun_name clas inst_tyvars inst_tys dfun_theta
670 = mkVanillaGlobal dfun_name dfun_ty noCafNoTyGenIdInfo
672 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
674 {- 1 dec 99: disable the Mark Jones optimisation for the sake
675 of compatibility with Hugs.
676 See `types/InstEnv' for a discussion related to this.
678 (class_tyvars, sc_theta, _, _) = classBigSig clas
679 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
680 sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys) sc_theta
681 dfun_theta = case inst_decl_theta of
682 [] -> [] -- If inst_decl_theta is empty, then we don't
683 -- want to have any dict arguments, so that we can
684 -- expose the constant methods.
686 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
687 -- Otherwise we pass the superclass dictionaries to
688 -- the dictionary function; the Mark Jones optimisation.
690 -- NOTE the "nub". I got caught by this one:
691 -- class Monad m => MonadT t m where ...
692 -- instance Monad m => MonadT (EnvT env) m where ...
693 -- Here, the inst_decl_theta has (Monad m); but so
694 -- does the sc_theta'!
696 -- NOTE the "not_const". I got caught by this one too:
697 -- class Foo a => Baz a b where ...
698 -- instance Wob b => Baz T b where..
699 -- Now sc_theta' has Foo T
704 %************************************************************************
706 \subsection{Un-definable}
708 %************************************************************************
710 These two can't be defined in Haskell.
712 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
713 just gets expanded into a type coercion wherever it occurs. Hence we
714 add it as a built-in Id with an unfolding here.
716 The type variables we use here are "open" type variables: this means
717 they can unify with both unlifted and lifted types. Hence we provide
718 another gun with which to shoot yourself in the foot.
722 = pcMiscPrelId unsafeCoerceIdKey pREL_GHC SLIT("unsafeCoerce#") ty info
724 info = noCafNoTyGenIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
727 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
728 (mkFunTy openAlphaTy openBetaTy)
729 [x] = mkTemplateLocals [openAlphaTy]
730 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
731 Note (Coerce openBetaTy openAlphaTy) (Var x)
735 @getTag#@ is another function which can't be defined in Haskell. It needs to
736 evaluate its argument and call the dataToTag# primitive.
740 = pcMiscPrelId getTagIdKey pREL_GHC SLIT("getTag#") ty info
742 info = noCafNoTyGenIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
743 -- We don't provide a defn for this; you must inline it
745 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy intPrimTy)
746 [x,y] = mkTemplateLocals [alphaTy,alphaTy]
747 rhs = mkLams [alphaTyVar,x] $
748 Case (Var x) y [ (DEFAULT, [], mkApps (Var dataToTagId) [Type alphaTy, Var y]) ]
750 dataToTagId = mkPrimOpId DataToTagOp
753 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
754 nasty as-is, change it back to a literal (@Literal@).
757 realWorldPrimId -- :: State# RealWorld
758 = pcMiscPrelId realWorldPrimIdKey pREL_GHC SLIT("realWorld#")
760 (noCafNoTyGenIdInfo `setUnfoldingInfo` mkOtherCon [])
761 -- The mkOtherCon makes it look that realWorld# is evaluated
762 -- which in turn makes Simplify.interestingArg return True,
763 -- which in turn makes INLINE things applied to realWorld# likely
768 %************************************************************************
770 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
772 %************************************************************************
774 GHC randomly injects these into the code.
776 @patError@ is just a version of @error@ for pattern-matching
777 failures. It knows various ``codes'' which expand to longer
778 strings---this saves space!
780 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
781 well shouldn't be yanked on, but if one is, then you will get a
782 friendly message from @absentErr@ (rather than a totally random
785 @parError@ is a special version of @error@ which the compiler does
786 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
787 templates, but we don't ever expect to generate code for it.
791 = pc_bottoming_Id errorIdKey pREL_ERR SLIT("error") errorTy
793 = generic_ERROR_ID patErrorIdKey SLIT("patError")
795 = generic_ERROR_ID recSelErrIdKey SLIT("recSelError")
797 = generic_ERROR_ID recConErrorIdKey SLIT("recConError")
799 = generic_ERROR_ID recUpdErrorIdKey SLIT("recUpdError")
801 = generic_ERROR_ID irrefutPatErrorIdKey SLIT("irrefutPatError")
802 nON_EXHAUSTIVE_GUARDS_ERROR_ID
803 = generic_ERROR_ID nonExhaustiveGuardsErrorIdKey SLIT("nonExhaustiveGuardsError")
804 nO_METHOD_BINDING_ERROR_ID
805 = generic_ERROR_ID noMethodBindingErrorIdKey SLIT("noMethodBindingError")
808 = pc_bottoming_Id absentErrorIdKey pREL_ERR SLIT("absentErr")
809 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy)
812 = pcMiscPrelId parErrorIdKey pREL_ERR SLIT("parError")
813 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy) noCafNoTyGenIdInfo
817 %************************************************************************
819 \subsection{Utilities}
821 %************************************************************************
824 pcMiscPrelId :: Unique{-IdKey-} -> Module -> FAST_STRING -> Type -> IdInfo -> Id
825 pcMiscPrelId key mod str ty info
827 name = mkWiredInName mod (mkVarOcc str) key
828 imp = mkVanillaGlobal name ty info -- the usual case...
831 -- We lie and say the thing is imported; otherwise, we get into
832 -- a mess with dependency analysis; e.g., core2stg may heave in
833 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
834 -- being compiled, then it's just a matter of luck if the definition
835 -- will be in "the right place" to be in scope.
837 pc_bottoming_Id key mod name ty
840 id = pcMiscPrelId key mod name ty bottoming_info
841 strict_info = mkStrictnessInfo ([wwStrict], True)
842 bottoming_info = noCafNoTyGenIdInfo
843 `setStrictnessInfo` strict_info
844 `setNewStrictnessInfo` mkNewStrictnessInfo id 1 strict_info NoCPRInfo
847 -- these "bottom" out, no matter what their arguments
849 generic_ERROR_ID u n = pc_bottoming_Id u pREL_ERR n errorTy
851 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
852 openAlphaTy = mkTyVarTy openAlphaTyVar
853 openBetaTy = mkTyVarTy openBetaTyVar
856 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy]
858 -- Notice the openAlphaTyVar. It says that "error" can be applied
859 -- to unboxed as well as boxed types. This is OK because it never
860 -- returns, so the return type is irrelevant.