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, eRROR_CSTRING_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, addrPrimTy
38 import TysWiredIn ( charTy, mkListTy )
39 import PrelRules ( primOpRule )
40 import Rules ( addRule )
41 import TcType ( Type, ThetaType, mkDictTy, mkPredTys, mkTyConApp,
42 mkTyVarTys, mkClassPred, tcEqPred,
43 mkFunTys, mkFunTy, mkSigmaTy, tcSplitSigmaTy,
44 isUnLiftedType, mkForAllTys, mkTyVarTy, tyVarsOfType,
45 tcSplitFunTys, tcSplitForAllTys, mkPredTy
47 import Module ( Module )
48 import CoreUtils ( exprType, mkInlineMe )
49 import CoreUnfold ( mkTopUnfolding, mkCompulsoryUnfolding, mkOtherCon )
50 import Literal ( Literal(..) )
51 import TyCon ( TyCon, isNewTyCon, tyConTyVars, tyConDataCons,
52 tyConTheta, isProductTyCon, isDataTyCon, isRecursiveTyCon )
53 import Class ( Class, classTyCon, classTyVars, classSelIds )
54 import Var ( Id, TyVar )
55 import VarSet ( isEmptyVarSet )
56 import Name ( mkWiredInName, mkFCallName, Name )
57 import OccName ( mkVarOcc )
58 import PrimOp ( PrimOp(DataToTagOp), primOpSig, mkPrimOpIdName )
59 import ForeignCall ( ForeignCall )
60 import DataCon ( DataCon,
61 dataConFieldLabels, dataConRepArity, dataConTyCon,
62 dataConArgTys, dataConRepType, dataConRepStrictness,
63 dataConInstOrigArgTys,
64 dataConName, dataConTheta,
65 dataConSig, dataConStrictMarks, dataConId,
68 import Id ( idType, mkGlobalId, mkVanillaGlobal, mkSysLocal,
69 mkLocalIdWithInfo, setIdNoDiscard,
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]
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
148 `setNewStrictnessInfo` Just strict_sig
150 arity = dataConRepArity data_con
151 strict_sig = mkStrictSig id arity (mkTopDmdType (replicate arity topDmd) cpr_info)
153 tycon = dataConTyCon data_con
154 cpr_info | isProductTyCon tycon &&
157 arity <= mAX_CPR_SIZE = RetCPR
159 -- RetCPR is only true for products that are real data types;
160 -- that is, not unboxed tuples or [non-recursive] 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)
221 -- The NoCaf-ness is set by noCafNoTyGenIdInfo
223 -- It's important to specify the arity, so that partial
224 -- applications are treated as values
225 `setNewStrictnessInfo` Just wrap_sig
227 wrap_ty = mkForAllTys all_tyvars $
231 res_info = strictSigResInfo (idNewStrictness work_id)
232 wrap_sig = mkStrictSig wrap_id arity (mkTopDmdType (replicate arity topDmd) res_info)
233 -- The Cpr info can be important inside INLINE rhss, where the
234 -- wrapper constructor isn't inlined
235 -- But we are sloppy about the argument demands, because we expect
236 -- to inline the constructor very vigorously.
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)
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
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
609 `setNewStrictnessInfo` Just (mkNewStrictnessInfo id arity strict_info NoCPRInfo)
610 -- Until we modify the primop generation code
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
642 `setNewStrictnessInfo` Just strict_sig
644 (_, tau) = tcSplitForAllTys ty
645 (arg_tys, _) = tcSplitFunTys tau
646 arity = length arg_tys
647 strict_sig = mkStrictSig id arity (mkTopDmdType (replicate arity evalDmd) TopRes)
651 %************************************************************************
653 \subsection{DictFuns and default methods}
655 %************************************************************************
658 mkDefaultMethodId dm_name ty
659 = mkVanillaGlobal dm_name ty noCafNoTyGenIdInfo
661 mkDictFunId :: Name -- Name to use for the dict fun;
668 mkDictFunId dfun_name clas inst_tyvars inst_tys dfun_theta
669 = setIdNoDiscard (mkLocalIdWithInfo dfun_name dfun_ty noCafNoTyGenIdInfo)
670 -- NB: It's important that dict funs are *local* Ids
671 -- This ensures that they are taken to account by free-variable finding
672 -- and dependency analysis (e.g. CoreFVs.exprFreeVars).
673 -- In particular, if they are globals, the
674 -- specialiser floats dict uses above their defns, which prevents
675 -- good simplifications happening.
677 -- It's OK for them to be locals, because we form the instance-env to
678 -- pass on to the next module (md_insts) in CoreTidy, afer tdying
679 -- and globalising the top-level Ids.
681 -- BUT Make sure it's an exported Id (setIdNoDiscard) so that it's not dropped!
683 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
685 {- 1 dec 99: disable the Mark Jones optimisation for the sake
686 of compatibility with Hugs.
687 See `types/InstEnv' for a discussion related to this.
689 (class_tyvars, sc_theta, _, _) = classBigSig clas
690 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
691 sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys) sc_theta
692 dfun_theta = case inst_decl_theta of
693 [] -> [] -- If inst_decl_theta is empty, then we don't
694 -- want to have any dict arguments, so that we can
695 -- expose the constant methods.
697 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
698 -- Otherwise we pass the superclass dictionaries to
699 -- the dictionary function; the Mark Jones optimisation.
701 -- NOTE the "nub". I got caught by this one:
702 -- class Monad m => MonadT t m where ...
703 -- instance Monad m => MonadT (EnvT env) m where ...
704 -- Here, the inst_decl_theta has (Monad m); but so
705 -- does the sc_theta'!
707 -- NOTE the "not_const". I got caught by this one too:
708 -- class Foo a => Baz a b where ...
709 -- instance Wob b => Baz T b where..
710 -- Now sc_theta' has Foo T
715 %************************************************************************
717 \subsection{Un-definable}
719 %************************************************************************
721 These two can't be defined in Haskell.
723 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
724 just gets expanded into a type coercion wherever it occurs. Hence we
725 add it as a built-in Id with an unfolding here.
727 The type variables we use here are "open" type variables: this means
728 they can unify with both unlifted and lifted types. Hence we provide
729 another gun with which to shoot yourself in the foot.
733 = pcMiscPrelId unsafeCoerceIdKey pREL_GHC SLIT("unsafeCoerce#") ty info
735 info = noCafNoTyGenIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
738 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
739 (mkFunTy openAlphaTy openBetaTy)
740 [x] = mkTemplateLocals [openAlphaTy]
741 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
742 Note (Coerce openBetaTy openAlphaTy) (Var x)
746 @getTag#@ is another function which can't be defined in Haskell. It needs to
747 evaluate its argument and call the dataToTag# primitive.
751 = pcMiscPrelId getTagIdKey pREL_GHC SLIT("getTag#") ty info
753 info = noCafNoTyGenIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
754 -- We don't provide a defn for this; you must inline it
756 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy intPrimTy)
757 [x,y] = mkTemplateLocals [alphaTy,alphaTy]
758 rhs = mkLams [alphaTyVar,x] $
759 Case (Var x) y [ (DEFAULT, [], mkApps (Var dataToTagId) [Type alphaTy, Var y]) ]
761 dataToTagId = mkPrimOpId DataToTagOp
764 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
765 nasty as-is, change it back to a literal (@Literal@).
768 realWorldPrimId -- :: State# RealWorld
769 = pcMiscPrelId realWorldPrimIdKey pREL_GHC SLIT("realWorld#")
771 (noCafNoTyGenIdInfo `setUnfoldingInfo` mkOtherCon [])
772 -- The mkOtherCon makes it look that realWorld# is evaluated
773 -- which in turn makes Simplify.interestingArg return True,
774 -- which in turn makes INLINE things applied to realWorld# likely
779 %************************************************************************
781 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
783 %************************************************************************
785 GHC randomly injects these into the code.
787 @patError@ is just a version of @error@ for pattern-matching
788 failures. It knows various ``codes'' which expand to longer
789 strings---this saves space!
791 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
792 well shouldn't be yanked on, but if one is, then you will get a
793 friendly message from @absentErr@ (rather than a totally random
796 @parError@ is a special version of @error@ which the compiler does
797 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
798 templates, but we don't ever expect to generate code for it.
802 = pc_bottoming_Id errorIdKey pREL_ERR SLIT("error") errorTy
804 = pc_bottoming_Id errorCStringIdKey pREL_ERR SLIT("errorCString")
805 (mkSigmaTy [openAlphaTyVar] [] (mkFunTy addrPrimTy openAlphaTy))
807 = generic_ERROR_ID patErrorIdKey SLIT("patError")
809 = generic_ERROR_ID recSelErrIdKey SLIT("recSelError")
811 = generic_ERROR_ID recConErrorIdKey SLIT("recConError")
813 = generic_ERROR_ID recUpdErrorIdKey SLIT("recUpdError")
815 = generic_ERROR_ID irrefutPatErrorIdKey SLIT("irrefutPatError")
816 nON_EXHAUSTIVE_GUARDS_ERROR_ID
817 = generic_ERROR_ID nonExhaustiveGuardsErrorIdKey SLIT("nonExhaustiveGuardsError")
818 nO_METHOD_BINDING_ERROR_ID
819 = generic_ERROR_ID noMethodBindingErrorIdKey SLIT("noMethodBindingError")
822 = pc_bottoming_Id absentErrorIdKey pREL_ERR SLIT("absentErr")
823 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy)
826 = pcMiscPrelId parErrorIdKey pREL_ERR SLIT("parError")
827 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy) noCafNoTyGenIdInfo
831 %************************************************************************
833 \subsection{Utilities}
835 %************************************************************************
838 pcMiscPrelId :: Unique{-IdKey-} -> Module -> FAST_STRING -> Type -> IdInfo -> Id
839 pcMiscPrelId key mod str ty info
841 name = mkWiredInName mod (mkVarOcc str) key
842 imp = mkVanillaGlobal name ty info -- the usual case...
845 -- We lie and say the thing is imported; otherwise, we get into
846 -- a mess with dependency analysis; e.g., core2stg may heave in
847 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
848 -- being compiled, then it's just a matter of luck if the definition
849 -- will be in "the right place" to be in scope.
851 pc_bottoming_Id key mod name ty
854 id = pcMiscPrelId key mod name ty bottoming_info
856 strict_sig = mkStrictSig id arity (mkTopDmdType [evalDmd] BotRes)
857 bottoming_info = noCafNoTyGenIdInfo `setNewStrictnessInfo` Just strict_sig
858 -- these "bottom" out, no matter what their arguments
860 generic_ERROR_ID u n = pc_bottoming_Id u pREL_ERR n errorTy
862 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
863 openAlphaTy = mkTyVarTy openAlphaTyVar
864 openBetaTy = mkTyVarTy openBetaTyVar
867 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy]
869 -- Notice the openAlphaTyVar. It says that "error" can be applied
870 -- to unboxed as well as boxed types. This is OK because it never
871 -- returns, so the return type is irrelevant.