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,
21 mkPrimOpId, mkFCallId,
23 mkReboxingAlt, mkNewTypeBody,
25 -- And some particular Ids; see below for why they are wired in
26 wiredInIds, ghcPrimIds,
27 unsafeCoerceId, realWorldPrimId, voidArgId, nullAddrId, seqId,
30 rEC_CON_ERROR_ID, iRREFUT_PAT_ERROR_ID, rUNTIME_ERROR_ID,
31 nON_EXHAUSTIVE_GUARDS_ERROR_ID, nO_METHOD_BINDING_ERROR_ID,
35 #include "HsVersions.h"
38 import BasicTypes ( Arity, StrictnessMark(..), isMarkedUnboxed, isMarkedStrict )
39 import TysPrim ( openAlphaTyVars, alphaTyVar, alphaTy, betaTyVar, betaTy,
40 intPrimTy, realWorldStatePrimTy, addrPrimTy
42 import TysWiredIn ( charTy, mkListTy )
43 import PrelRules ( primOpRules )
44 import Rules ( addRule )
45 import TcType ( Type, ThetaType, mkDictTy, mkPredTys, mkTyConApp,
46 mkTyVarTys, mkClassPred, tcEqPred,
47 mkFunTys, mkFunTy, mkSigmaTy, tcSplitSigmaTy,
48 isUnLiftedType, mkForAllTys, mkTyVarTy, tyVarsOfType,
49 tcSplitFunTys, tcSplitForAllTys, mkPredTy
51 import Module ( Module )
52 import CoreUtils ( exprType )
53 import CoreUnfold ( mkTopUnfolding, mkCompulsoryUnfolding, mkOtherCon )
54 import Literal ( Literal(..), nullAddrLit )
55 import TyCon ( TyCon, isNewTyCon, tyConTyVars, tyConDataCons,
56 tyConTheta, isProductTyCon, isDataTyCon, isRecursiveTyCon )
57 import Class ( Class, classTyCon, classTyVars, classSelIds )
58 import Var ( Id, TyVar, Var )
59 import VarSet ( isEmptyVarSet )
60 import Name ( mkWiredInName, mkFCallName, Name )
61 import OccName ( mkVarOcc )
62 import PrimOp ( PrimOp(DataToTagOp), primOpSig, mkPrimOpIdName )
63 import ForeignCall ( ForeignCall )
64 import DataCon ( DataCon,
65 dataConFieldLabels, dataConRepArity, dataConTyCon,
66 dataConArgTys, dataConRepType,
68 dataConName, dataConTheta,
69 dataConSig, dataConStrictMarks, dataConWorkId,
72 import Id ( idType, mkGlobalId, mkVanillaGlobal, mkSysLocal,
73 mkTemplateLocals, mkTemplateLocalsNum,
74 mkTemplateLocal, idNewStrictness, idName
76 import IdInfo ( IdInfo, noCafIdInfo,
78 setArityInfo, setSpecInfo, setCafInfo,
80 GlobalIdDetails(..), CafInfo(..)
82 import NewDemand ( mkStrictSig, strictSigResInfo, DmdResult(..),
83 mkTopDmdType, topDmd, evalDmd, lazyDmd, retCPR,
84 Demand(..), Demands(..) )
85 import FieldLabel ( mkFieldLabel, fieldLabelName,
86 firstFieldLabelTag, allFieldLabelTags, fieldLabelType
88 import DmdAnal ( dmdAnalTopRhs )
90 import Unique ( mkBuiltinUnique )
93 import Maybe ( isJust )
94 import Util ( dropList, isSingleton )
97 import ListSetOps ( assoc, assocMaybe )
98 import UnicodeUtil ( stringToUtf8 )
103 %************************************************************************
105 \subsection{Wired in Ids}
107 %************************************************************************
111 = [ -- These error-y things are wired in because we don't yet have
112 -- a way to express in an interface file that the result type variable
113 -- is 'open'; that is can be unified with an unboxed type
115 -- [The interface file format now carry such information, but there's
116 -- no way yet of expressing at the definition site for these
117 -- error-reporting functions that they have an 'open'
118 -- result type. -- sof 1/99]
120 eRROR_ID, -- This one isn't used anywhere else in the compiler
121 -- But we still need it in wiredInIds so that when GHC
122 -- compiles a program that mentions 'error' we don't
123 -- import its type from the interface file; we just get
124 -- the Id defined here. Which has an 'open-tyvar' type.
127 iRREFUT_PAT_ERROR_ID,
128 nON_EXHAUSTIVE_GUARDS_ERROR_ID,
129 nO_METHOD_BINDING_ERROR_ID,
134 -- These Ids are exported from GHC.Prim
136 = [ -- These can't be defined in Haskell, but they have
137 -- perfectly reasonable unfoldings in Core
146 %************************************************************************
148 \subsection{Data constructors}
150 %************************************************************************
153 mkDataConId :: Name -> DataCon -> Id
154 -- Makes the *worker* for the data constructor; that is, the function
155 -- that takes the reprsentation arguments and builds the constructor.
156 mkDataConId work_name data_con
157 = mkGlobalId (DataConId data_con) work_name (dataConRepType data_con) info
161 `setAllStrictnessInfo` Just strict_sig
163 arity = dataConRepArity data_con
165 strict_sig = mkStrictSig (mkTopDmdType (replicate arity topDmd) cpr_info)
166 -- Notice that we do *not* say the worker is strict
167 -- even if the data constructor is declared strict
168 -- e.g. data T = MkT !(Int,Int)
169 -- Why? Because the *wrapper* is strict (and its unfolding has case
170 -- expresssions that do the evals) but the *worker* itself is not.
171 -- If we pretend it is strict then when we see
172 -- case x of y -> $wMkT y
173 -- the simplifier thinks that y is "sure to be evaluated" (because
174 -- $wMkT is strict) and drops the case. No, $wMkT is not strict.
176 -- When the simplifer sees a pattern
177 -- case e of MkT x -> ...
178 -- it uses the dataConRepStrictness of MkT to mark x as evaluated;
179 -- but that's fine... dataConRepStrictness comes from the data con
180 -- not from the worker Id.
182 tycon = dataConTyCon data_con
183 cpr_info | isProductTyCon tycon &&
186 arity <= mAX_CPR_SIZE = retCPR
188 -- RetCPR is only true for products that are real data types;
189 -- that is, not unboxed tuples or [non-recursive] newtypes
191 mAX_CPR_SIZE :: Arity
193 -- We do not treat very big tuples as CPR-ish:
194 -- a) for a start we get into trouble because there aren't
195 -- "enough" unboxed tuple types (a tiresome restriction,
197 -- b) more importantly, big unboxed tuples get returned mainly
198 -- on the stack, and are often then allocated in the heap
199 -- by the caller. So doing CPR for them may in fact make
203 The wrapper for a constructor is an ordinary top-level binding that evaluates
204 any strict args, unboxes any args that are going to be flattened, and calls
207 We're going to build a constructor that looks like:
209 data (Data a, C b) => T a b = T1 !a !Int b
212 \d1::Data a, d2::C b ->
213 \p q r -> case p of { p ->
215 Con T1 [a,b] [p,q,r]}}
219 * d2 is thrown away --- a context in a data decl is used to make sure
220 one *could* construct dictionaries at the site the constructor
221 is used, but the dictionary isn't actually used.
223 * We have to check that we can construct Data dictionaries for
224 the types a and Int. Once we've done that we can throw d1 away too.
226 * We use (case p of q -> ...) to evaluate p, rather than "seq" because
227 all that matters is that the arguments are evaluated. "seq" is
228 very careful to preserve evaluation order, which we don't need
231 You might think that we could simply give constructors some strictness
232 info, like PrimOps, and let CoreToStg do the let-to-case transformation.
233 But we don't do that because in the case of primops and functions strictness
234 is a *property* not a *requirement*. In the case of constructors we need to
235 do something active to evaluate the argument.
237 Making an explicit case expression allows the simplifier to eliminate
238 it in the (common) case where the constructor arg is already evaluated.
241 mkDataConWrapId data_con
242 = mkGlobalId (DataConWrapId data_con) (dataConName data_con) wrap_ty info
244 work_id = dataConWorkId data_con
247 `setUnfoldingInfo` wrap_unf
248 -- The NoCaf-ness is set by noCafIdInfo
250 -- It's important to specify the arity, so that partial
251 -- applications are treated as values
252 `setAllStrictnessInfo` Just wrap_sig
254 wrap_sig = mkStrictSig (mkTopDmdType arg_dmds res_info)
255 res_info = strictSigResInfo (idNewStrictness work_id)
256 arg_dmds = map mk_dmd strict_marks
257 mk_dmd str | isMarkedStrict str = evalDmd
258 | otherwise = lazyDmd
259 -- The Cpr info can be important inside INLINE rhss, where the
260 -- wrapper constructor isn't inlined.
261 -- And the argument strictness can be important too; we
262 -- may not inline a contructor when it is partially applied.
264 -- data W = C !Int !Int !Int
265 -- ...(let w = C x in ...(w p q)...)...
266 -- we want to see that w is strict in its two arguments
268 wrap_unf | isNewTyCon tycon
269 = ASSERT( null ex_tyvars && null ex_dict_args && isSingleton orig_arg_tys )
270 -- No existentials on a newtype, but it can have a context
271 -- e.g. newtype Eq a => T a = MkT (...)
272 mkTopUnfolding $ Note InlineMe $
273 mkLams tyvars $ Lam id_arg1 $
274 mkNewTypeBody tycon result_ty (Var id_arg1)
276 | not (any isMarkedStrict strict_marks)
277 = mkCompulsoryUnfolding (Var work_id)
278 -- The common case. Not only is this efficient,
279 -- but it also ensures that the wrapper is replaced
280 -- by the worker even when there are no args.
284 -- This is really important in rule matching,
285 -- (We could match on the wrappers,
286 -- but that makes it less likely that rules will match
287 -- when we bring bits of unfoldings together.)
289 -- NB: because of this special case, (map (:) ys) turns into
290 -- (map $w: ys). The top-level defn for (:) is never used.
291 -- This is somewhat of a bore, but I'm currently leaving it
292 -- as is, so that there still is a top level curried (:) for
293 -- the interpreter to call.
296 = mkTopUnfolding $ Note InlineMe $
298 mkLams ex_dict_args $ mkLams id_args $
299 foldr mk_case con_app
300 (zip (ex_dict_args++id_args) strict_marks) i3 []
302 con_app i rep_ids = mkApps (Var work_id)
303 (map varToCoreExpr (all_tyvars ++ reverse rep_ids))
305 (tyvars, _, ex_tyvars, ex_theta, orig_arg_tys, tycon) = dataConSig data_con
306 all_tyvars = tyvars ++ ex_tyvars
308 ex_dict_tys = mkPredTys ex_theta
309 all_arg_tys = ex_dict_tys ++ orig_arg_tys
310 result_ty = mkTyConApp tycon (mkTyVarTys tyvars)
312 wrap_ty = mkForAllTys all_tyvars (mkFunTys all_arg_tys result_ty)
313 -- We used to include the stupid theta in the wrapper's args
314 -- but now we don't. Instead the type checker just injects these
315 -- extra constraints where necessary.
317 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
321 (ex_dict_args,i2) = mkLocals 1 ex_dict_tys
322 (id_args,i3) = mkLocals i2 orig_arg_tys
324 (id_arg1:_) = id_args -- Used for newtype only
326 strict_marks = dataConStrictMarks data_con
329 :: (Id, StrictnessMark) -- Arg, strictness
330 -> (Int -> [Id] -> CoreExpr) -- Body
331 -> Int -- Next rep arg id
332 -> [Id] -- Rep args so far, reversed
334 mk_case (arg,strict) body i rep_args
336 NotMarkedStrict -> body i (arg:rep_args)
338 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
340 Case (Var arg) arg [(DEFAULT,[], body i (arg:rep_args))]
343 -> case splitProductType "do_unbox" (idType arg) of
344 (tycon, tycon_args, con, tys) ->
345 Case (Var arg) arg [(DataAlt con, con_args,
346 body i' (reverse con_args ++ rep_args))]
348 (con_args, i') = mkLocals i tys
352 %************************************************************************
354 \subsection{Record selectors}
356 %************************************************************************
358 We're going to build a record selector unfolding that looks like this:
360 data T a b c = T1 { ..., op :: a, ...}
361 | T2 { ..., op :: a, ...}
364 sel = /\ a b c -> \ d -> case d of
369 Similarly for newtypes
371 newtype N a = MkN { unN :: a->a }
374 unN n = coerce (a->a) n
376 We need to take a little care if the field has a polymorphic type:
378 data R = R { f :: forall a. a->a }
382 f :: forall a. R -> a -> a
383 f = /\ a \ r = case r of
386 (not f :: R -> forall a. a->a, which gives the type inference mechanism
387 problems at call sites)
389 Similarly for newtypes
391 newtype N = MkN { unN :: forall a. a->a }
393 unN :: forall a. N -> a -> a
394 unN = /\a -> \n:N -> coerce (a->a) n
397 mkRecordSelId tycon field_label
398 -- Assumes that all fields with the same field label have the same type
400 -- Annoyingly, we have to pass in the unpackCString# Id, because
401 -- we can't conjure it up out of thin air
404 sel_id = mkGlobalId (RecordSelId field_label) (fieldLabelName field_label) selector_ty info
405 field_ty = fieldLabelType field_label
406 data_cons = tyConDataCons tycon
407 tyvars = tyConTyVars tycon -- These scope over the types in
408 -- the FieldLabels of constructors of this type
409 data_ty = mkTyConApp tycon tyvar_tys
410 tyvar_tys = mkTyVarTys tyvars
412 -- Very tiresomely, the selectors are (unnecessarily!) overloaded over
413 -- just the dictionaries in the types of the constructors that contain
414 -- the relevant field. [The Report says that pattern matching on a
415 -- constructor gives the same constraints as applying it.] Urgh.
417 -- However, not all data cons have all constraints (because of
418 -- TcTyDecls.thinContext). So we need to find all the data cons
419 -- involved in the pattern match and take the union of their constraints.
421 -- NB: this code relies on the fact that DataCons are quantified over
422 -- the identical type variables as their parent TyCon
423 tycon_theta = tyConTheta tycon -- The context on the data decl
424 -- eg data (Eq a, Ord b) => T a b = ...
425 needed_preds = [pred | (DataAlt dc, _, _) <- the_alts, pred <- dataConTheta dc]
426 dict_tys = map mkPredTy (nubBy tcEqPred needed_preds)
427 n_dict_tys = length dict_tys
429 (field_tyvars,field_theta,field_tau) = tcSplitSigmaTy field_ty
430 field_dict_tys = map mkPredTy field_theta
431 n_field_dict_tys = length field_dict_tys
432 -- If the field has a universally quantified type we have to
433 -- be a bit careful. Suppose we have
434 -- data R = R { op :: forall a. Foo a => a -> a }
435 -- Then we can't give op the type
436 -- op :: R -> forall a. Foo a => a -> a
437 -- because the typechecker doesn't understand foralls to the
438 -- right of an arrow. The "right" type to give it is
439 -- op :: forall a. Foo a => R -> a -> a
440 -- But then we must generate the right unfolding too:
441 -- op = /\a -> \dfoo -> \ r ->
444 -- Note that this is exactly the type we'd infer from a user defn
448 selector_ty = mkForAllTys tyvars $ mkForAllTys field_tyvars $
449 mkFunTys dict_tys $ mkFunTys field_dict_tys $
450 mkFunTy data_ty field_tau
452 arity = 1 + n_dict_tys + n_field_dict_tys
454 (strict_sig, rhs_w_str) = dmdAnalTopRhs sel_rhs
455 -- Use the demand analyser to work out strictness.
456 -- With all this unpackery it's not easy!
459 `setCafInfo` caf_info
461 `setUnfoldingInfo` mkTopUnfolding rhs_w_str
462 `setAllStrictnessInfo` Just strict_sig
464 -- Allocate Ids. We do it a funny way round because field_dict_tys is
465 -- almost always empty. Also note that we use length_tycon_theta
466 -- rather than n_dict_tys, because the latter gives an infinite loop:
467 -- n_dict tys depends on the_alts, which depens on arg_ids, which depends
468 -- on arity, which depends on n_dict tys. Sigh! Mega sigh!
469 field_dict_base = length tycon_theta + 1
470 dict_id_base = field_dict_base + n_field_dict_tys
471 field_base = dict_id_base + 1
472 dict_ids = mkTemplateLocalsNum 1 dict_tys
473 field_dict_ids = mkTemplateLocalsNum field_dict_base field_dict_tys
474 data_id = mkTemplateLocal dict_id_base data_ty
476 alts = map mk_maybe_alt data_cons
477 the_alts = catMaybes alts
479 no_default = all isJust alts -- No default needed
480 default_alt | no_default = []
481 | otherwise = [(DEFAULT, [], error_expr)]
483 -- the default branch may have CAF refs, because it calls recSelError etc.
484 caf_info | no_default = NoCafRefs
485 | otherwise = MayHaveCafRefs
487 sel_rhs = mkLams tyvars $ mkLams field_tyvars $
488 mkLams dict_ids $ mkLams field_dict_ids $
489 Lam data_id $ sel_body
491 sel_body | isNewTyCon tycon = mkNewTypeBody tycon field_tau (mk_result data_id)
492 | otherwise = Case (Var data_id) data_id (default_alt ++ the_alts)
494 mk_result result_id = mkVarApps (mkVarApps (Var result_id) field_tyvars) field_dict_ids
495 -- We pull the field lambdas to the top, so we need to
496 -- apply them in the body. For example:
497 -- data T = MkT { foo :: forall a. a->a }
499 -- foo :: forall a. T -> a -> a
500 -- foo = /\a. \t:T. case t of { MkT f -> f a }
502 mk_maybe_alt data_con
503 = case maybe_the_arg_id of
505 Just the_arg_id -> Just (mkReboxingAlt uniqs data_con arg_ids body)
507 body = mk_result the_arg_id
509 arg_ids = mkTemplateLocalsNum field_base (dataConOrigArgTys data_con)
510 -- No need to instantiate; same tyvars in datacon as tycon
512 unpack_base = field_base + length arg_ids
513 uniqs = map mkBuiltinUnique [unpack_base..]
515 -- arity+1 avoids all shadowing
516 maybe_the_arg_id = assocMaybe (field_lbls `zip` arg_ids) field_label
517 field_lbls = dataConFieldLabels data_con
519 error_expr = mkRuntimeErrorApp rEC_SEL_ERROR_ID field_tau full_msg
520 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
523 -- (mkReboxingAlt us con xs rhs) basically constructs the case
524 -- alternative (con, xs, rhs)
525 -- but it does the reboxing necessary to construct the *source*
526 -- arguments, xs, from the representation arguments ys.
528 -- data T = MkT !(Int,Int) Bool
530 -- mkReboxingAlt MkT [x,b] r
531 -- = (DataAlt MkT, [y::Int,z::Int,b], let x = (y,z) in r)
533 -- mkDataAlt should really be in DataCon, but it can't because
534 -- it manipulates CoreSyn.
537 :: [Unique] -- Uniques for the new Ids
539 -> [Var] -- Source-level args
543 mkReboxingAlt us con args rhs
544 | not (any isMarkedUnboxed stricts)
545 = (DataAlt con, args, rhs)
549 (binds, args') = go args stricts us
551 (DataAlt con, args', mkLets binds rhs)
554 stricts = dataConStrictMarks con
556 go [] stricts us = ([], [])
558 -- Type variable case
559 go (arg:args) stricts us
561 = let (binds, args') = go args stricts us
562 in (binds, arg:args')
564 -- Term variable case
565 go (arg:args) (str:stricts) us
566 | isMarkedUnboxed str
568 (_, tycon_args, pack_con, con_arg_tys)
569 = splitProductType "mkReboxingAlt" (idType arg)
571 unpacked_args = zipWith (mkSysLocal FSLIT("rb")) us con_arg_tys
572 (binds, args') = go args stricts (dropList con_arg_tys us)
573 con_app = mkConApp pack_con (map Type tycon_args ++ map Var unpacked_args)
575 (NonRec arg con_app : binds, unpacked_args ++ args')
578 = let (binds, args') = go args stricts us
579 in (binds, arg:args')
583 %************************************************************************
585 \subsection{Dictionary selectors}
587 %************************************************************************
589 Selecting a field for a dictionary. If there is just one field, then
590 there's nothing to do.
592 ToDo: unify with mkRecordSelId.
595 mkDictSelId :: Name -> Class -> Id
596 mkDictSelId name clas
597 = mkGlobalId (RecordSelId field_lbl) name sel_ty info
599 sel_ty = mkForAllTys tyvars (mkFunTy (idType dict_id) (idType the_arg_id))
600 -- We can't just say (exprType rhs), because that would give a type
602 -- for a single-op class (after all, the selector is the identity)
603 -- But it's type must expose the representation of the dictionary
604 -- to gat (say) C a -> (a -> a)
606 field_lbl = mkFieldLabel name tycon sel_ty tag
607 tag = assoc "MkId.mkDictSelId" (map idName (classSelIds clas) `zip` allFieldLabelTags) name
611 `setUnfoldingInfo` mkTopUnfolding rhs
612 `setAllStrictnessInfo` Just strict_sig
614 -- We no longer use 'must-inline' on record selectors. They'll
615 -- inline like crazy if they scrutinise a constructor
617 -- The strictness signature is of the form U(AAAVAAAA) -> T
618 -- where the V depends on which item we are selecting
619 -- It's worth giving one, so that absence info etc is generated
620 -- even if the selector isn't inlined
621 strict_sig = mkStrictSig (mkTopDmdType [arg_dmd] TopRes)
622 arg_dmd | isNewTyCon tycon = evalDmd
623 | otherwise = Eval (Prod [ if the_arg_id == id then evalDmd else Abs
626 tyvars = classTyVars clas
628 tycon = classTyCon clas
629 [data_con] = tyConDataCons tycon
630 tyvar_tys = mkTyVarTys tyvars
631 arg_tys = dataConArgTys data_con tyvar_tys
632 the_arg_id = arg_ids !! (tag - firstFieldLabelTag)
634 pred = mkClassPred clas tyvar_tys
635 (dict_id:arg_ids) = mkTemplateLocals (mkPredTy pred : arg_tys)
637 rhs | isNewTyCon tycon = mkLams tyvars $ Lam dict_id $
638 mkNewTypeBody tycon (head arg_tys) (Var dict_id)
639 | otherwise = mkLams tyvars $ Lam dict_id $
640 Case (Var dict_id) dict_id
641 [(DataAlt data_con, arg_ids, Var the_arg_id)]
643 mkNewTypeBody tycon result_ty result_expr
644 -- Adds a coerce where necessary
645 -- Used for both wrapping and unwrapping
646 | isRecursiveTyCon tycon -- Recursive case; use a coerce
647 = Note (Coerce result_ty (exprType result_expr)) result_expr
648 | otherwise -- Normal case
653 %************************************************************************
655 \subsection{Primitive operations
657 %************************************************************************
660 mkPrimOpId :: PrimOp -> Id
664 (tyvars,arg_tys,res_ty, arity, strict_sig) = primOpSig prim_op
665 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
666 name = mkPrimOpIdName prim_op
667 id = mkGlobalId (PrimOpId prim_op) name ty info
672 `setAllStrictnessInfo` Just strict_sig
674 rules = foldl (addRule id) emptyCoreRules (primOpRules prim_op)
677 -- For each ccall we manufacture a separate CCallOpId, giving it
678 -- a fresh unique, a type that is correct for this particular ccall,
679 -- and a CCall structure that gives the correct details about calling
682 -- The *name* of this Id is a local name whose OccName gives the full
683 -- details of the ccall, type and all. This means that the interface
684 -- file reader can reconstruct a suitable Id
686 mkFCallId :: Unique -> ForeignCall -> Type -> Id
687 mkFCallId uniq fcall ty
688 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
689 -- A CCallOpId should have no free type variables;
690 -- when doing substitutions won't substitute over it
691 mkGlobalId (FCallId fcall) name ty info
693 occ_str = showSDoc (braces (ppr fcall <+> ppr ty))
694 -- The "occurrence name" of a ccall is the full info about the
695 -- ccall; it is encoded, but may have embedded spaces etc!
697 name = mkFCallName uniq occ_str
701 `setAllStrictnessInfo` Just strict_sig
703 (_, tau) = tcSplitForAllTys ty
704 (arg_tys, _) = tcSplitFunTys tau
705 arity = length arg_tys
706 strict_sig = mkStrictSig (mkTopDmdType (replicate arity evalDmd) TopRes)
710 %************************************************************************
712 \subsection{DictFuns and default methods}
714 %************************************************************************
716 Important notes about dict funs and default methods
717 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
718 Dict funs and default methods are *not* ImplicitIds. Their definition
719 involves user-written code, so we can't figure out their strictness etc
720 based on fixed info, as we can for constructors and record selectors (say).
722 We build them as GlobalIds, but when in the module where they are
723 bound, we turn the Id at the *binding site* into an exported LocalId.
724 This ensures that they are taken to account by free-variable finding
725 and dependency analysis (e.g. CoreFVs.exprFreeVars). The simplifier
726 will propagate the LocalId to all occurrence sites.
728 Why shouldn't they be bound as GlobalIds? Because, in particular, if
729 they are globals, the specialiser floats dict uses above their defns,
730 which prevents good simplifications happening. Also the strictness
731 analyser treats a occurrence of a GlobalId as imported and assumes it
732 contains strictness in its IdInfo, which isn't true if the thing is
733 bound in the same module as the occurrence.
735 It's OK for dfuns to be LocalIds, because we form the instance-env to
736 pass on to the next module (md_insts) in CoreTidy, afer tidying
737 and globalising the top-level Ids.
739 BUT make sure they are *exported* LocalIds (setIdLocalExported) so
740 that they aren't discarded by the occurrence analyser.
743 mkDefaultMethodId dm_name ty = mkVanillaGlobal dm_name ty noCafIdInfo
745 mkDictFunId :: Name -- Name to use for the dict fun;
752 mkDictFunId dfun_name clas inst_tyvars inst_tys dfun_theta
753 = mkVanillaGlobal dfun_name dfun_ty noCafIdInfo
755 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
757 {- 1 dec 99: disable the Mark Jones optimisation for the sake
758 of compatibility with Hugs.
759 See `types/InstEnv' for a discussion related to this.
761 (class_tyvars, sc_theta, _, _) = classBigSig clas
762 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
763 sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys) sc_theta
764 dfun_theta = case inst_decl_theta of
765 [] -> [] -- If inst_decl_theta is empty, then we don't
766 -- want to have any dict arguments, so that we can
767 -- expose the constant methods.
769 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
770 -- Otherwise we pass the superclass dictionaries to
771 -- the dictionary function; the Mark Jones optimisation.
773 -- NOTE the "nub". I got caught by this one:
774 -- class Monad m => MonadT t m where ...
775 -- instance Monad m => MonadT (EnvT env) m where ...
776 -- Here, the inst_decl_theta has (Monad m); but so
777 -- does the sc_theta'!
779 -- NOTE the "not_const". I got caught by this one too:
780 -- class Foo a => Baz a b where ...
781 -- instance Wob b => Baz T b where..
782 -- Now sc_theta' has Foo T
787 %************************************************************************
789 \subsection{Un-definable}
791 %************************************************************************
793 These Ids can't be defined in Haskell. They could be defined in
794 unfoldings in the wired-in GHC.Prim interface file, but we'd have to
795 ensure that they were definitely, definitely inlined, because there is
796 no curried identifier for them. That's what mkCompulsoryUnfolding
797 does. If we had a way to get a compulsory unfolding from an interface
798 file, we could do that, but we don't right now.
800 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
801 just gets expanded into a type coercion wherever it occurs. Hence we
802 add it as a built-in Id with an unfolding here.
804 The type variables we use here are "open" type variables: this means
805 they can unify with both unlifted and lifted types. Hence we provide
806 another gun with which to shoot yourself in the foot.
809 -- unsafeCoerce# :: forall a b. a -> b
811 = pcMiscPrelId unsafeCoerceIdKey gHC_PRIM FSLIT("unsafeCoerce#") ty info
813 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
816 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
817 (mkFunTy openAlphaTy openBetaTy)
818 [x] = mkTemplateLocals [openAlphaTy]
819 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
820 Note (Coerce openBetaTy openAlphaTy) (Var x)
822 -- nullAddr# :: Addr#
823 -- The reason is is here is because we don't provide
824 -- a way to write this literal in Haskell.
826 = pcMiscPrelId nullAddrIdKey gHC_PRIM FSLIT("nullAddr#") addrPrimTy info
828 info = noCafIdInfo `setUnfoldingInfo`
829 mkCompulsoryUnfolding (Lit nullAddrLit)
832 = pcMiscPrelId seqIdKey gHC_PRIM FSLIT("seq") ty info
834 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
837 ty = mkForAllTys [alphaTyVar,betaTyVar]
838 (mkFunTy alphaTy (mkFunTy betaTy betaTy))
839 [x,y] = mkTemplateLocals [alphaTy, betaTy]
840 rhs = mkLams [alphaTyVar,betaTyVar,x,y] (Case (Var x) x [(DEFAULT, [], Var y)])
843 @getTag#@ is another function which can't be defined in Haskell. It needs to
844 evaluate its argument and call the dataToTag# primitive.
848 = pcMiscPrelId getTagIdKey gHC_PRIM FSLIT("getTag#") ty info
850 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
851 -- We don't provide a defn for this; you must inline it
853 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy intPrimTy)
854 [x,y] = mkTemplateLocals [alphaTy,alphaTy]
855 rhs = mkLams [alphaTyVar,x] $
856 Case (Var x) y [ (DEFAULT, [], mkApps (Var dataToTagId) [Type alphaTy, Var y]) ]
858 dataToTagId = mkPrimOpId DataToTagOp
861 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
862 nasty as-is, change it back to a literal (@Literal@).
864 voidArgId is a Local Id used simply as an argument in functions
865 where we just want an arg to avoid having a thunk of unlifted type.
867 x = \ void :: State# RealWorld -> (# p, q #)
869 This comes up in strictness analysis
872 realWorldPrimId -- :: State# RealWorld
873 = pcMiscPrelId realWorldPrimIdKey gHC_PRIM FSLIT("realWorld#")
875 (noCafIdInfo `setUnfoldingInfo` mkOtherCon [])
876 -- The mkOtherCon makes it look that realWorld# is evaluated
877 -- which in turn makes Simplify.interestingArg return True,
878 -- which in turn makes INLINE things applied to realWorld# likely
881 voidArgId -- :: State# RealWorld
882 = mkSysLocal FSLIT("void") voidArgIdKey realWorldStatePrimTy
886 %************************************************************************
888 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
890 %************************************************************************
892 GHC randomly injects these into the code.
894 @patError@ is just a version of @error@ for pattern-matching
895 failures. It knows various ``codes'' which expand to longer
896 strings---this saves space!
898 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
899 well shouldn't be yanked on, but if one is, then you will get a
900 friendly message from @absentErr@ (rather than a totally random
903 @parError@ is a special version of @error@ which the compiler does
904 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
905 templates, but we don't ever expect to generate code for it.
909 :: Id -- Should be of type (forall a. Addr# -> a)
910 -- where Addr# points to a UTF8 encoded string
911 -> Type -- The type to instantiate 'a'
912 -> String -- The string to print
915 mkRuntimeErrorApp err_id res_ty err_msg
916 = mkApps (Var err_id) [Type res_ty, err_string]
918 err_string = Lit (MachStr (mkFastString (stringToUtf8 err_msg)))
920 rEC_SEL_ERROR_ID = mkRuntimeErrorId recSelErrIdKey FSLIT("recSelError")
921 rUNTIME_ERROR_ID = mkRuntimeErrorId runtimeErrorIdKey FSLIT("runtimeError")
923 iRREFUT_PAT_ERROR_ID = mkRuntimeErrorId irrefutPatErrorIdKey FSLIT("irrefutPatError")
924 rEC_CON_ERROR_ID = mkRuntimeErrorId recConErrorIdKey FSLIT("recConError")
925 nON_EXHAUSTIVE_GUARDS_ERROR_ID = mkRuntimeErrorId nonExhaustiveGuardsErrorIdKey FSLIT("nonExhaustiveGuardsError")
926 pAT_ERROR_ID = mkRuntimeErrorId patErrorIdKey FSLIT("patError")
927 nO_METHOD_BINDING_ERROR_ID = mkRuntimeErrorId noMethodBindingErrorIdKey FSLIT("noMethodBindingError")
929 -- The runtime error Ids take a UTF8-encoded string as argument
930 mkRuntimeErrorId key name = pc_bottoming_Id key pREL_ERR name runtimeErrorTy
931 runtimeErrorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTy addrPrimTy openAlphaTy)
935 eRROR_ID = pc_bottoming_Id errorIdKey pREL_ERR FSLIT("error") errorTy
938 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy] openAlphaTy)
939 -- Notice the openAlphaTyVar. It says that "error" can be applied
940 -- to unboxed as well as boxed types. This is OK because it never
941 -- returns, so the return type is irrelevant.
945 %************************************************************************
947 \subsection{Utilities}
949 %************************************************************************
952 pcMiscPrelId :: Unique{-IdKey-} -> Module -> FastString -> Type -> IdInfo -> Id
953 pcMiscPrelId key mod str ty info
955 name = mkWiredInName mod (mkVarOcc str) key
956 imp = mkVanillaGlobal name ty info -- the usual case...
959 -- We lie and say the thing is imported; otherwise, we get into
960 -- a mess with dependency analysis; e.g., core2stg may heave in
961 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
962 -- being compiled, then it's just a matter of luck if the definition
963 -- will be in "the right place" to be in scope.
965 pc_bottoming_Id key mod name ty
966 = pcMiscPrelId key mod name ty bottoming_info
968 strict_sig = mkStrictSig (mkTopDmdType [evalDmd] BotRes)
969 bottoming_info = noCafIdInfo `setAllStrictnessInfo` Just strict_sig
970 -- these "bottom" out, no matter what their arguments
972 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
973 openAlphaTy = mkTyVarTy openAlphaTyVar
974 openBetaTy = mkTyVarTy openBetaTyVar