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, nullAddrId,
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, betaTyVar, betaTy,
36 intPrimTy, realWorldStatePrimTy, addrPrimTy
38 import TysWiredIn ( charTy, mkListTy )
39 import PrelRules ( primOpRules )
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 ( mkInlineMe )
49 import CoreUnfold ( mkTopUnfolding, mkCompulsoryUnfolding, mkOtherCon )
50 import Literal ( Literal(..), nullAddrLit )
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,
63 dataConInstOrigArgTys,
64 dataConName, dataConTheta,
65 dataConSig, dataConStrictMarks, dataConId,
68 import Id ( idType, mkGlobalId, mkVanillaGlobal, mkSysLocal,
69 mkTemplateLocals, mkTemplateLocalsNum,
70 mkTemplateLocal, idNewStrictness, idName
72 import IdInfo ( IdInfo, noCafNoTyGenIdInfo,
74 setArityInfo, setSpecInfo, setCgInfo, setCafInfo,
75 mkNewStrictnessInfo, setNewStrictnessInfo,
76 GlobalIdDetails(..), CafInfo(..), CprInfo(..),
79 import NewDemand ( mkStrictSig, strictSigResInfo, DmdResult(..),
80 mkTopDmdType, topDmd, evalDmd, Demand(..), Keepity(..) )
81 import FieldLabel ( mkFieldLabel, fieldLabelName,
82 firstFieldLabelTag, allFieldLabelTags, fieldLabelType
84 import DmdAnal ( dmdAnalTopRhs )
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
110 -- error-reporting functions that they have an 'open'
111 -- result type. -- sof 1/99]
116 , iRREFUT_PAT_ERROR_ID
117 , nON_EXHAUSTIVE_GUARDS_ERROR_ID
118 , nO_METHOD_BINDING_ERROR_ID
124 -- These can't be defined in Haskell, but they have
125 -- perfectly reasonable unfoldings in Core
134 %************************************************************************
136 \subsection{Data constructors}
138 %************************************************************************
141 mkDataConId :: Name -> DataCon -> Id
142 -- Makes the *worker* for the data constructor; that is, the function
143 -- that takes the reprsentation arguments and builds the constructor.
144 mkDataConId work_name data_con
145 = mkGlobalId (DataConId data_con) work_name (dataConRepType data_con) info
147 info = noCafNoTyGenIdInfo
149 `setNewStrictnessInfo` Just strict_sig
151 arity = dataConRepArity data_con
153 strict_sig = mkStrictSig (mkTopDmdType (replicate arity topDmd) cpr_info)
154 -- Notice that we do *not* say the worker is strict
155 -- even if the data constructor is declared strict
156 -- e.g. data T = MkT !(Int,Int)
157 -- Why? Because the *wrapper* is strict (and its unfolding has case
158 -- expresssions that do the evals) but the *worker* itself is not.
159 -- If we pretend it is strict then when we see
160 -- case x of y -> $wMkT y
161 -- the simplifier thinks that y is "sure to be evaluated" (because
162 -- $wMkT is strict) and drops the case. No, $wMkT is not strict.
164 -- When the simplifer sees a pattern
165 -- case e of MkT x -> ...
166 -- it uses the dataConRepStrictness of MkT to mark x as evaluated;
167 -- but that's fine... dataConRepStrictness comes from the data con
168 -- not from the worker Id.
170 tycon = dataConTyCon data_con
171 cpr_info | isProductTyCon tycon &&
174 arity <= mAX_CPR_SIZE = RetCPR
176 -- RetCPR is only true for products that are real data types;
177 -- that is, not unboxed tuples or [non-recursive] newtypes
179 mAX_CPR_SIZE :: Arity
181 -- We do not treat very big tuples as CPR-ish:
182 -- a) for a start we get into trouble because there aren't
183 -- "enough" unboxed tuple types (a tiresome restriction,
185 -- b) more importantly, big unboxed tuples get returned mainly
186 -- on the stack, and are often then allocated in the heap
187 -- by the caller. So doing CPR for them may in fact make
191 The wrapper for a constructor is an ordinary top-level binding that evaluates
192 any strict args, unboxes any args that are going to be flattened, and calls
195 We're going to build a constructor that looks like:
197 data (Data a, C b) => T a b = T1 !a !Int b
200 \d1::Data a, d2::C b ->
201 \p q r -> case p of { p ->
203 Con T1 [a,b] [p,q,r]}}
207 * d2 is thrown away --- a context in a data decl is used to make sure
208 one *could* construct dictionaries at the site the constructor
209 is used, but the dictionary isn't actually used.
211 * We have to check that we can construct Data dictionaries for
212 the types a and Int. Once we've done that we can throw d1 away too.
214 * We use (case p of q -> ...) to evaluate p, rather than "seq" because
215 all that matters is that the arguments are evaluated. "seq" is
216 very careful to preserve evaluation order, which we don't need
219 You might think that we could simply give constructors some strictness
220 info, like PrimOps, and let CoreToStg do the let-to-case transformation.
221 But we don't do that because in the case of primops and functions strictness
222 is a *property* not a *requirement*. In the case of constructors we need to
223 do something active to evaluate the argument.
225 Making an explicit case expression allows the simplifier to eliminate
226 it in the (common) case where the constructor arg is already evaluated.
229 mkDataConWrapId data_con
230 = mkGlobalId (DataConWrapId data_con) (dataConName data_con) wrap_ty info
232 work_id = dataConId data_con
234 info = noCafNoTyGenIdInfo
235 `setUnfoldingInfo` mkTopUnfolding (mkInlineMe wrap_rhs)
236 -- The NoCaf-ness is set by noCafNoTyGenIdInfo
238 -- It's important to specify the arity, so that partial
239 -- applications are treated as values
240 `setNewStrictnessInfo` Just wrap_sig
242 wrap_ty = mkForAllTys all_tyvars (mkFunTys all_arg_tys result_ty)
244 wrap_sig = mkStrictSig (mkTopDmdType arg_dmds res_info)
245 res_info = strictSigResInfo (idNewStrictness work_id)
246 arg_dmds = [Abs | d <- dict_args] ++ map mk_dmd strict_marks
247 mk_dmd str | isMarkedStrict str = Eval
249 -- The Cpr info can be important inside INLINE rhss, where the
250 -- wrapper constructor isn't inlined
251 -- And the argument strictness can be important too; we
252 -- may not inline a contructor when it is partially applied.
254 -- data W = C !Int !Int !Int
255 -- ...(let w = C x in ...(w p q)...)...
256 -- we want to see that w is strict in its two arguments
258 wrap_rhs | isNewTyCon tycon
259 = ASSERT( null ex_tyvars && null ex_dict_args && length orig_arg_tys == 1 )
260 -- No existentials on a newtype, but it can have a context
261 -- e.g. newtype Eq a => T a = MkT (...)
262 mkLams tyvars $ mkLams dict_args $ Lam id_arg1 $
263 mkNewTypeBody tycon result_ty id_arg1
265 | null dict_args && not (any isMarkedStrict strict_marks)
266 = Var work_id -- The common case. Not only is this efficient,
267 -- but it also ensures that the wrapper is replaced
268 -- by the worker even when there are no args.
272 -- This is really important in rule matching,
273 -- (We could match on the wrappers,
274 -- but that makes it less likely that rules will match
275 -- when we bring bits of unfoldings together.)
277 -- NB: because of this special case, (map (:) ys) turns into
278 -- (map $w: ys), and thence into (map (\x xs. $w: x xs) ys)
279 -- in core-to-stg. The top-level defn for (:) is never used.
280 -- This is somewhat of a bore, but I'm currently leaving it
281 -- as is, so that there still is a top level curried (:) for
282 -- the interpreter to call.
285 = mkLams all_tyvars $ mkLams dict_args $
286 mkLams ex_dict_args $ mkLams id_args $
287 foldr mk_case con_app
288 (zip (ex_dict_args++id_args) strict_marks) i3 []
290 con_app i rep_ids = mkApps (Var work_id)
291 (map varToCoreExpr (all_tyvars ++ reverse rep_ids))
293 (tyvars, theta, ex_tyvars, ex_theta, orig_arg_tys, tycon) = dataConSig data_con
294 all_tyvars = tyvars ++ ex_tyvars
296 dict_tys = mkPredTys theta
297 ex_dict_tys = mkPredTys ex_theta
298 all_arg_tys = dict_tys ++ ex_dict_tys ++ orig_arg_tys
299 result_ty = mkTyConApp tycon (mkTyVarTys tyvars)
301 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
305 (dict_args, i1) = mkLocals 1 dict_tys
306 (ex_dict_args,i2) = mkLocals i1 ex_dict_tys
307 (id_args,i3) = mkLocals i2 orig_arg_tys
309 (id_arg1:_) = id_args -- Used for newtype only
311 strict_marks = dataConStrictMarks data_con
314 :: (Id, StrictnessMark) -- Arg, strictness
315 -> (Int -> [Id] -> CoreExpr) -- Body
316 -> Int -- Next rep arg id
317 -> [Id] -- Rep args so far, reversed
319 mk_case (arg,strict) body i rep_args
321 NotMarkedStrict -> body i (arg:rep_args)
323 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
325 Case (Var arg) arg [(DEFAULT,[], body i (arg:rep_args))]
328 -> case splitProductType "do_unbox" (idType arg) of
329 (tycon, tycon_args, con, tys) ->
330 Case (Var arg) arg [(DataAlt con, con_args,
331 body i' (reverse con_args ++ rep_args))]
333 (con_args, i') = mkLocals i tys
337 %************************************************************************
339 \subsection{Record selectors}
341 %************************************************************************
343 We're going to build a record selector unfolding that looks like this:
345 data T a b c = T1 { ..., op :: a, ...}
346 | T2 { ..., op :: a, ...}
349 sel = /\ a b c -> \ d -> case d of
354 Similarly for newtypes
356 newtype N a = MkN { unN :: a->a }
359 unN n = coerce (a->a) n
361 We need to take a little care if the field has a polymorphic type:
363 data R = R { f :: forall a. a->a }
367 f :: forall a. R -> a -> a
368 f = /\ a \ r = case r of
371 (not f :: R -> forall a. a->a, which gives the type inference mechanism
372 problems at call sites)
374 Similarly for newtypes
376 newtype N = MkN { unN :: forall a. a->a }
378 unN :: forall a. N -> a -> a
379 unN = /\a -> \n:N -> coerce (a->a) n
382 mkRecordSelId tycon field_label unpack_id unpackUtf8_id
383 -- Assumes that all fields with the same field label have the same type
385 -- Annoyingly, we have to pass in the unpackCString# Id, because
386 -- we can't conjure it up out of thin air
389 sel_id = mkGlobalId (RecordSelId field_label) (fieldLabelName field_label) selector_ty info
390 field_ty = fieldLabelType field_label
391 data_cons = tyConDataCons tycon
392 tyvars = tyConTyVars tycon -- These scope over the types in
393 -- the FieldLabels of constructors of this type
394 data_ty = mkTyConApp tycon tyvar_tys
395 tyvar_tys = mkTyVarTys tyvars
397 tycon_theta = tyConTheta tycon -- The context on the data decl
398 -- eg data (Eq a, Ord b) => T a b = ...
399 dict_tys = [mkPredTy pred | pred <- tycon_theta,
401 needed_dict pred = or [ tcEqPred pred p
402 | (DataAlt dc, _, _) <- the_alts, p <- dataConTheta dc]
403 n_dict_tys = length dict_tys
405 (field_tyvars,field_theta,field_tau) = tcSplitSigmaTy field_ty
406 field_dict_tys = map mkPredTy field_theta
407 n_field_dict_tys = length field_dict_tys
408 -- If the field has a universally quantified type we have to
409 -- be a bit careful. Suppose we have
410 -- data R = R { op :: forall a. Foo a => a -> a }
411 -- Then we can't give op the type
412 -- op :: R -> forall a. Foo a => a -> a
413 -- because the typechecker doesn't understand foralls to the
414 -- right of an arrow. The "right" type to give it is
415 -- op :: forall a. Foo a => R -> a -> a
416 -- But then we must generate the right unfolding too:
417 -- op = /\a -> \dfoo -> \ r ->
420 -- Note that this is exactly the type we'd infer from a user defn
423 -- Very tiresomely, the selectors are (unnecessarily!) overloaded over
424 -- just the dictionaries in the types of the constructors that contain
425 -- the relevant field. Urgh.
426 -- NB: this code relies on the fact that DataCons are quantified over
427 -- the identical type variables as their parent TyCon
430 selector_ty = mkForAllTys tyvars $ mkForAllTys field_tyvars $
431 mkFunTys dict_tys $ mkFunTys field_dict_tys $
432 mkFunTy data_ty field_tau
434 arity = 1 + n_dict_tys + n_field_dict_tys
436 (strict_sig, rhs_w_str) = dmdAnalTopRhs sel_rhs
437 -- Use the demand analyser to work out strictness.
438 -- With all this unpackery it's not easy!
440 info = noCafNoTyGenIdInfo
441 `setCafInfo` caf_info
443 `setUnfoldingInfo` mkTopUnfolding rhs_w_str
444 `setNewStrictnessInfo` Just strict_sig
446 -- Allocate Ids. We do it a funny way round because field_dict_tys is
447 -- almost always empty. Also note that we use length_tycon_theta
448 -- rather than n_dict_tys, because the latter gives an infinite loop:
449 -- n_dict tys depends on the_alts, which depens on arg_ids, which depends
450 -- on arity, which depends on n_dict tys. Sigh! Mega sigh!
451 field_dict_base = length tycon_theta + 1
452 dict_id_base = field_dict_base + n_field_dict_tys
453 field_base = dict_id_base + 1
454 dict_ids = mkTemplateLocalsNum 1 dict_tys
455 field_dict_ids = mkTemplateLocalsNum field_dict_base field_dict_tys
456 data_id = mkTemplateLocal dict_id_base data_ty
458 alts = map mk_maybe_alt data_cons
459 the_alts = catMaybes alts
461 no_default = all isJust alts -- No default needed
462 default_alt | no_default = []
463 | otherwise = [(DEFAULT, [], error_expr)]
465 -- the default branch may have CAF refs, because it calls recSelError etc.
466 caf_info | no_default = NoCafRefs
467 | otherwise = MayHaveCafRefs
469 sel_rhs = mkLams tyvars $ mkLams field_tyvars $
470 mkLams dict_ids $ mkLams field_dict_ids $
471 Lam data_id $ sel_body
473 sel_body | isNewTyCon tycon = mkNewTypeBody tycon field_tau data_id
474 | otherwise = Case (Var data_id) data_id (default_alt ++ the_alts)
476 mk_maybe_alt data_con
477 = case maybe_the_arg_id of
479 Just the_arg_id -> Just (DataAlt data_con, real_args, mkLets binds body)
481 body = mkVarApps (mkVarApps (Var the_arg_id) field_tyvars) field_dict_ids
482 strict_marks = dataConStrictMarks data_con
483 (binds, real_args) = rebuildConArgs arg_ids strict_marks
484 (map mkBuiltinUnique [unpack_base..])
486 arg_ids = mkTemplateLocalsNum field_base (dataConInstOrigArgTys data_con tyvar_tys)
488 unpack_base = field_base + length arg_ids
490 -- arity+1 avoids all shadowing
491 maybe_the_arg_id = assocMaybe (field_lbls `zip` arg_ids) field_label
492 field_lbls = dataConFieldLabels data_con
494 error_expr = mkApps (Var rEC_SEL_ERROR_ID) [Type field_tau, err_string]
496 | all safeChar full_msg
497 = App (Var unpack_id) (Lit (MachStr (_PK_ full_msg)))
499 = App (Var unpackUtf8_id) (Lit (MachStr (_PK_ (stringToUtf8 (map ord full_msg)))))
501 safeChar c = c >= '\1' && c <= '\xFF'
502 -- TODO: Putting this Unicode stuff here is ugly. Find a better
503 -- generic place to make string literals. This logic is repeated
505 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
508 -- This rather ugly function converts the unpacked data con
509 -- arguments back into their packed form.
512 :: [Id] -- Source-level args
513 -> [StrictnessMark] -- Strictness annotations (per-arg)
514 -> [Unique] -- Uniques for the new Ids
515 -> ([CoreBind], [Id]) -- A binding for each source-level arg, plus
516 -- a list of the representation-level arguments
517 -- e.g. data T = MkT Int !Int
519 -- rebuild [x::Int, y::Int] [Not, Unbox]
520 -- = ([ y = I# t ], [x,t])
522 rebuildConArgs [] stricts us = ([], [])
524 -- Type variable case
525 rebuildConArgs (arg:args) stricts us
527 = let (binds, args') = rebuildConArgs args stricts us
528 in (binds, arg:args')
530 -- Term variable case
531 rebuildConArgs (arg:args) (str:stricts) us
532 | isMarkedUnboxed str
536 (_, tycon_args, pack_con, con_arg_tys)
537 = splitProductType "rebuildConArgs" arg_ty
539 unpacked_args = zipWith (mkSysLocal SLIT("rb")) us con_arg_tys
540 (binds, args') = rebuildConArgs args stricts (drop (length con_arg_tys) us)
541 con_app = mkConApp pack_con (map Type tycon_args ++ map Var unpacked_args)
543 (NonRec arg con_app : binds, unpacked_args ++ args')
546 = let (binds, args') = rebuildConArgs args stricts us
547 in (binds, arg:args')
551 %************************************************************************
553 \subsection{Dictionary selectors}
555 %************************************************************************
557 Selecting a field for a dictionary. If there is just one field, then
558 there's nothing to do.
560 ToDo: unify with mkRecordSelId.
563 mkDictSelId :: Name -> Class -> Id
564 mkDictSelId name clas
565 = mkGlobalId (RecordSelId field_lbl) name sel_ty info
567 sel_ty = mkForAllTys tyvars (mkFunTy (idType dict_id) (idType the_arg_id))
568 -- We can't just say (exprType rhs), because that would give a type
570 -- for a single-op class (after all, the selector is the identity)
571 -- But it's type must expose the representation of the dictionary
572 -- to gat (say) C a -> (a -> a)
574 field_lbl = mkFieldLabel name tycon sel_ty tag
575 tag = assoc "MkId.mkDictSelId" (map idName (classSelIds clas) `zip` allFieldLabelTags) name
577 info = noCafNoTyGenIdInfo
579 `setUnfoldingInfo` mkTopUnfolding rhs
580 `setNewStrictnessInfo` Just strict_sig
582 -- We no longer use 'must-inline' on record selectors. They'll
583 -- inline like crazy if they scrutinise a constructor
585 -- The strictness signature is of the form U(AAAVAAAA) -> T
586 -- where the V depends on which item we are selecting
587 -- It's worth giving one, so that absence info etc is generated
588 -- even if the selector isn't inlined
589 strict_sig = mkStrictSig (mkTopDmdType [arg_dmd] TopRes)
590 arg_dmd | isNewTyCon tycon = Eval
591 | otherwise = Seq Drop [ if the_arg_id == id then Eval else Abs
594 tyvars = classTyVars clas
596 tycon = classTyCon clas
597 [data_con] = tyConDataCons tycon
598 tyvar_tys = mkTyVarTys tyvars
599 arg_tys = dataConArgTys data_con tyvar_tys
600 the_arg_id = arg_ids !! (tag - firstFieldLabelTag)
602 pred = mkClassPred clas tyvar_tys
603 (dict_id:arg_ids) = mkTemplateLocals (mkPredTy pred : arg_tys)
605 rhs | isNewTyCon tycon = mkLams tyvars $ Lam dict_id $
606 mkNewTypeBody tycon (head arg_tys) dict_id
607 | otherwise = mkLams tyvars $ Lam dict_id $
608 Case (Var dict_id) dict_id
609 [(DataAlt data_con, arg_ids, Var the_arg_id)]
611 mkNewTypeBody tycon result_ty result_id
612 | isRecursiveTyCon tycon -- Recursive case; use a coerce
613 = Note (Coerce result_ty (idType result_id)) (Var result_id)
614 | otherwise -- Normal case
619 %************************************************************************
621 \subsection{Primitive operations
623 %************************************************************************
626 mkPrimOpId :: PrimOp -> Id
630 (tyvars,arg_tys,res_ty, arity, strict_info) = primOpSig prim_op
631 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
632 name = mkPrimOpIdName prim_op
633 id = mkGlobalId (PrimOpId prim_op) name ty info
635 info = noCafNoTyGenIdInfo
638 `setNewStrictnessInfo` Just (mkNewStrictnessInfo id arity strict_info NoCPRInfo)
639 -- Until we modify the primop generation code
641 rules = foldl (addRule id) emptyCoreRules (primOpRules prim_op)
644 -- For each ccall we manufacture a separate CCallOpId, giving it
645 -- a fresh unique, a type that is correct for this particular ccall,
646 -- and a CCall structure that gives the correct details about calling
649 -- The *name* of this Id is a local name whose OccName gives the full
650 -- details of the ccall, type and all. This means that the interface
651 -- file reader can reconstruct a suitable Id
653 mkFCallId :: Unique -> ForeignCall -> Type -> Id
654 mkFCallId uniq fcall ty
655 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
656 -- A CCallOpId should have no free type variables;
657 -- when doing substitutions won't substitute over it
658 mkGlobalId (FCallId fcall) name ty info
660 occ_str = showSDocIface (braces (ppr fcall <+> ppr ty))
661 -- The "occurrence name" of a ccall is the full info about the
662 -- ccall; it is encoded, but may have embedded spaces etc!
664 name = mkFCallName uniq occ_str
666 info = noCafNoTyGenIdInfo
668 `setNewStrictnessInfo` Just strict_sig
670 (_, tau) = tcSplitForAllTys ty
671 (arg_tys, _) = tcSplitFunTys tau
672 arity = length arg_tys
673 strict_sig = mkStrictSig (mkTopDmdType (replicate arity evalDmd) TopRes)
677 %************************************************************************
679 \subsection{DictFuns and default methods}
681 %************************************************************************
683 Important notes about dict funs and default methods
684 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
685 Dict funs and default methods are *not* ImplicitIds. Their definition
686 involves user-written code, so we can't figure out their strictness etc
687 based on fixed info, as we can for constructors and record selectors (say).
689 We build them as GlobalIds, but when in the module where they are
690 bound, we turn the Id at the *binding site* into an exported LocalId.
691 This ensures that they are taken to account by free-variable finding
692 and dependency analysis (e.g. CoreFVs.exprFreeVars). The simplifier
693 will propagate the LocalId to all occurrence sites.
695 Why shouldn't they be bound as GlobalIds? Because, in particular, if
696 they are globals, the specialiser floats dict uses above their defns,
697 which prevents good simplifications happening. Also the strictness
698 analyser treats a occurrence of a GlobalId as imported and assumes it
699 contains strictness in its IdInfo, which isn't true if the thing is
700 bound in the same module as the occurrence.
702 It's OK for dfuns to be LocalIds, because we form the instance-env to
703 pass on to the next module (md_insts) in CoreTidy, afer tidying
704 and globalising the top-level Ids.
706 BUT make sure they are *exported* LocalIds (setIdLocalExported) so
707 that they aren't discarded by the occurrence analyser.
710 mkDefaultMethodId dm_name ty = mkVanillaGlobal dm_name ty noCafNoTyGenIdInfo
712 mkDictFunId :: Name -- Name to use for the dict fun;
719 mkDictFunId dfun_name clas inst_tyvars inst_tys dfun_theta
720 = mkVanillaGlobal dfun_name dfun_ty noCafNoTyGenIdInfo
722 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
724 {- 1 dec 99: disable the Mark Jones optimisation for the sake
725 of compatibility with Hugs.
726 See `types/InstEnv' for a discussion related to this.
728 (class_tyvars, sc_theta, _, _) = classBigSig clas
729 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
730 sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys) sc_theta
731 dfun_theta = case inst_decl_theta of
732 [] -> [] -- If inst_decl_theta is empty, then we don't
733 -- want to have any dict arguments, so that we can
734 -- expose the constant methods.
736 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
737 -- Otherwise we pass the superclass dictionaries to
738 -- the dictionary function; the Mark Jones optimisation.
740 -- NOTE the "nub". I got caught by this one:
741 -- class Monad m => MonadT t m where ...
742 -- instance Monad m => MonadT (EnvT env) m where ...
743 -- Here, the inst_decl_theta has (Monad m); but so
744 -- does the sc_theta'!
746 -- NOTE the "not_const". I got caught by this one too:
747 -- class Foo a => Baz a b where ...
748 -- instance Wob b => Baz T b where..
749 -- Now sc_theta' has Foo T
754 %************************************************************************
756 \subsection{Un-definable}
758 %************************************************************************
760 These Ids can't be defined in Haskell. They could be defined in
761 unfoldings in PrelGHC.hi-boot, but we'd have to ensure that they
762 were definitely, definitely inlined, because there is no curried
763 identifier for them. That's what mkCompulsoryUnfolding does.
764 If we had a way to get a compulsory unfolding from an interface file,
765 we could do that, but we don't right now.
767 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
768 just gets expanded into a type coercion wherever it occurs. Hence we
769 add it as a built-in Id with an unfolding here.
771 The type variables we use here are "open" type variables: this means
772 they can unify with both unlifted and lifted types. Hence we provide
773 another gun with which to shoot yourself in the foot.
776 -- unsafeCoerce# :: forall a b. a -> b
778 = pcMiscPrelId unsafeCoerceIdKey pREL_GHC SLIT("unsafeCoerce#") ty info
780 info = noCafNoTyGenIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
783 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
784 (mkFunTy openAlphaTy openBetaTy)
785 [x] = mkTemplateLocals [openAlphaTy]
786 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
787 Note (Coerce openBetaTy openAlphaTy) (Var x)
789 -- nullAddr# :: Addr#
790 -- The reason is is here is because we don't provide
791 -- a way to write this literal in Haskell.
793 = pcMiscPrelId nullAddrIdKey pREL_GHC SLIT("nullAddr#") addrPrimTy info
795 info = noCafNoTyGenIdInfo `setUnfoldingInfo`
796 mkCompulsoryUnfolding (Lit nullAddrLit)
799 = pcMiscPrelId seqIdKey pREL_GHC SLIT("seq") ty info
801 info = noCafNoTyGenIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
804 ty = mkForAllTys [alphaTyVar,betaTyVar]
805 (mkFunTy alphaTy (mkFunTy betaTy betaTy))
806 [x,y] = mkTemplateLocals [alphaTy, betaTy]
807 rhs = mkLams [alphaTyVar,betaTyVar,x,y] (Case (Var x) x [(DEFAULT, [], Var y)])
810 @getTag#@ is another function which can't be defined in Haskell. It needs to
811 evaluate its argument and call the dataToTag# primitive.
815 = pcMiscPrelId getTagIdKey pREL_GHC SLIT("getTag#") ty info
817 info = noCafNoTyGenIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
818 -- We don't provide a defn for this; you must inline it
820 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy intPrimTy)
821 [x,y] = mkTemplateLocals [alphaTy,alphaTy]
822 rhs = mkLams [alphaTyVar,x] $
823 Case (Var x) y [ (DEFAULT, [], mkApps (Var dataToTagId) [Type alphaTy, Var y]) ]
825 dataToTagId = mkPrimOpId DataToTagOp
828 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
829 nasty as-is, change it back to a literal (@Literal@).
832 realWorldPrimId -- :: State# RealWorld
833 = pcMiscPrelId realWorldPrimIdKey pREL_GHC SLIT("realWorld#")
835 (noCafNoTyGenIdInfo `setUnfoldingInfo` mkOtherCon [])
836 -- The mkOtherCon makes it look that realWorld# is evaluated
837 -- which in turn makes Simplify.interestingArg return True,
838 -- which in turn makes INLINE things applied to realWorld# likely
843 %************************************************************************
845 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
847 %************************************************************************
849 GHC randomly injects these into the code.
851 @patError@ is just a version of @error@ for pattern-matching
852 failures. It knows various ``codes'' which expand to longer
853 strings---this saves space!
855 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
856 well shouldn't be yanked on, but if one is, then you will get a
857 friendly message from @absentErr@ (rather than a totally random
860 @parError@ is a special version of @error@ which the compiler does
861 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
862 templates, but we don't ever expect to generate code for it.
866 = pc_bottoming_Id errorIdKey pREL_ERR SLIT("error") errorTy
868 = pc_bottoming_Id errorCStringIdKey pREL_ERR SLIT("errorCString")
869 (mkSigmaTy [openAlphaTyVar] [] (mkFunTy addrPrimTy openAlphaTy))
871 = generic_ERROR_ID patErrorIdKey SLIT("patError")
873 = generic_ERROR_ID recSelErrIdKey SLIT("recSelError")
875 = generic_ERROR_ID recConErrorIdKey SLIT("recConError")
877 = generic_ERROR_ID recUpdErrorIdKey SLIT("recUpdError")
879 = generic_ERROR_ID irrefutPatErrorIdKey SLIT("irrefutPatError")
880 nON_EXHAUSTIVE_GUARDS_ERROR_ID
881 = generic_ERROR_ID nonExhaustiveGuardsErrorIdKey SLIT("nonExhaustiveGuardsError")
882 nO_METHOD_BINDING_ERROR_ID
883 = generic_ERROR_ID noMethodBindingErrorIdKey SLIT("noMethodBindingError")
886 = pc_bottoming_Id absentErrorIdKey pREL_ERR SLIT("absentErr")
887 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy)
890 = pcMiscPrelId parErrorIdKey pREL_ERR SLIT("parError")
891 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy) noCafNoTyGenIdInfo
895 %************************************************************************
897 \subsection{Utilities}
899 %************************************************************************
902 pcMiscPrelId :: Unique{-IdKey-} -> Module -> FAST_STRING -> Type -> IdInfo -> Id
903 pcMiscPrelId key mod str ty info
905 name = mkWiredInName mod (mkVarOcc str) key
906 imp = mkVanillaGlobal name ty info -- the usual case...
909 -- We lie and say the thing is imported; otherwise, we get into
910 -- a mess with dependency analysis; e.g., core2stg may heave in
911 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
912 -- being compiled, then it's just a matter of luck if the definition
913 -- will be in "the right place" to be in scope.
915 pc_bottoming_Id key mod name ty
916 = pcMiscPrelId key mod name ty bottoming_info
918 strict_sig = mkStrictSig (mkTopDmdType [evalDmd] BotRes)
919 bottoming_info = noCafNoTyGenIdInfo `setNewStrictnessInfo` Just strict_sig
920 -- these "bottom" out, no matter what their arguments
922 generic_ERROR_ID u n = pc_bottoming_Id u pREL_ERR n errorTy
924 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
925 openAlphaTy = mkTyVarTy openAlphaTyVar
926 openBetaTy = mkTyVarTy openBetaTyVar
929 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy]
931 -- Notice the openAlphaTyVar. It says that "error" can be applied
932 -- to unboxed as well as boxed types. This is OK because it never
933 -- returns, so the return type is irrelevant.