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,
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,
28 lazyId, lazyIdUnfolding, lazyIdKey,
31 rEC_CON_ERROR_ID, iRREFUT_PAT_ERROR_ID, rUNTIME_ERROR_ID,
32 nON_EXHAUSTIVE_GUARDS_ERROR_ID, nO_METHOD_BINDING_ERROR_ID,
33 pAT_ERROR_ID, eRROR_ID
36 #include "HsVersions.h"
39 import BasicTypes ( Arity, StrictnessMark(..), isMarkedUnboxed, isMarkedStrict )
40 import TysPrim ( openAlphaTyVars, alphaTyVar, alphaTy,
41 realWorldStatePrimTy, addrPrimTy
43 import TysWiredIn ( charTy, mkListTy )
44 import PrelRules ( primOpRules )
45 import Rules ( addRule )
46 import Type ( TyThing(..) )
47 import TcType ( Type, ThetaType, mkDictTy, mkPredTys, mkPredTy,
48 mkTyConApp, mkTyVarTys, mkClassPred, tcEqPred,
49 mkFunTys, mkFunTy, mkSigmaTy, tcSplitSigmaTy,
50 isUnLiftedType, mkForAllTys, mkTyVarTy, tyVarsOfType,
51 tcSplitFunTys, tcSplitForAllTys
53 import CoreUtils ( exprType )
54 import CoreUnfold ( mkTopUnfolding, mkCompulsoryUnfolding, mkOtherCon )
55 import Literal ( nullAddrLit, mkStringLit )
56 import TyCon ( TyCon, isNewTyCon, tyConTyVars, tyConDataCons,
57 tyConStupidTheta, isProductTyCon, isDataTyCon, isRecursiveTyCon )
58 import Class ( Class, classTyCon, classSelIds )
59 import Var ( Id, TyVar, Var )
60 import VarSet ( isEmptyVarSet )
61 import Name ( mkFCallName, mkWiredInName, Name, BuiltInSyntax(..) )
62 import OccName ( mkOccFS, varName )
63 import PrimOp ( PrimOp, primOpSig, primOpOcc, primOpTag )
64 import ForeignCall ( ForeignCall )
65 import DataCon ( DataCon, DataConIds(..), dataConTyVars,
66 dataConFieldLabels, dataConRepArity,
67 dataConRepArgTys, dataConRepType, dataConStupidTheta,
68 dataConSig, dataConStrictMarks, dataConExStricts,
69 splitProductType, isVanillaDataCon
71 import Id ( idType, mkGlobalId, mkVanillaGlobal, mkSysLocal,
72 mkTemplateLocals, mkTemplateLocalsNum, mkExportedLocalId,
73 mkTemplateLocal, idName
75 import IdInfo ( IdInfo, noCafIdInfo, setUnfoldingInfo,
76 setArityInfo, setSpecInfo, setCafInfo,
77 setAllStrictnessInfo, vanillaIdInfo,
78 GlobalIdDetails(..), CafInfo(..)
80 import NewDemand ( mkStrictSig, DmdResult(..),
81 mkTopDmdType, topDmd, evalDmd, lazyDmd, retCPR,
82 Demand(..), Demands(..) )
83 import DmdAnal ( dmdAnalTopRhs )
85 import Unique ( mkBuiltinUnique, mkPrimOpIdUnique )
88 import Maybe ( isJust )
89 import Util ( dropList, isSingleton )
92 import ListSetOps ( assoc, assocMaybe )
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]
113 eRROR_ID, -- This one isn't used anywhere else in the compiler
114 -- But we still need it in wiredInIds so that when GHC
115 -- compiles a program that mentions 'error' we don't
116 -- import its type from the interface file; we just get
117 -- the Id defined here. Which has an 'open-tyvar' type.
120 iRREFUT_PAT_ERROR_ID,
121 nON_EXHAUSTIVE_GUARDS_ERROR_ID,
122 nO_METHOD_BINDING_ERROR_ID,
129 -- These Ids are exported from GHC.Prim
131 = [ -- These can't be defined in Haskell, but they have
132 -- perfectly reasonable unfoldings in Core
140 %************************************************************************
142 \subsection{Data constructors}
144 %************************************************************************
146 The wrapper for a constructor is an ordinary top-level binding that evaluates
147 any strict args, unboxes any args that are going to be flattened, and calls
150 We're going to build a constructor that looks like:
152 data (Data a, C b) => T a b = T1 !a !Int b
155 \d1::Data a, d2::C b ->
156 \p q r -> case p of { p ->
158 Con T1 [a,b] [p,q,r]}}
162 * d2 is thrown away --- a context in a data decl is used to make sure
163 one *could* construct dictionaries at the site the constructor
164 is used, but the dictionary isn't actually used.
166 * We have to check that we can construct Data dictionaries for
167 the types a and Int. Once we've done that we can throw d1 away too.
169 * We use (case p of q -> ...) to evaluate p, rather than "seq" because
170 all that matters is that the arguments are evaluated. "seq" is
171 very careful to preserve evaluation order, which we don't need
174 You might think that we could simply give constructors some strictness
175 info, like PrimOps, and let CoreToStg do the let-to-case transformation.
176 But we don't do that because in the case of primops and functions strictness
177 is a *property* not a *requirement*. In the case of constructors we need to
178 do something active to evaluate the argument.
180 Making an explicit case expression allows the simplifier to eliminate
181 it in the (common) case where the constructor arg is already evaluated.
185 mkDataConIds :: Name -> Name -> DataCon -> DataConIds
186 -- Makes the *worker* for the data constructor; that is, the function
187 -- that takes the reprsentation arguments and builds the constructor.
188 mkDataConIds wrap_name wkr_name data_con
192 | any isMarkedStrict all_strict_marks -- Algebraic, needs wrapper
193 = AlgDC (Just alg_wrap_id) wrk_id
195 | otherwise -- Algebraic, no wrapper
196 = AlgDC Nothing wrk_id
198 (tyvars, theta, orig_arg_tys, tycon, res_tys) = dataConSig data_con
200 dict_tys = mkPredTys theta
201 all_arg_tys = dict_tys ++ orig_arg_tys
202 result_ty = mkTyConApp tycon res_tys
204 wrap_ty = mkForAllTys tyvars (mkFunTys all_arg_tys result_ty)
205 -- We used to include the stupid theta in the wrapper's args
206 -- but now we don't. Instead the type checker just injects these
207 -- extra constraints where necessary.
209 ----------- Worker (algebraic data types only) --------------
210 wrk_id = mkGlobalId (DataConWorkId data_con) wkr_name
211 (dataConRepType data_con) wkr_info
213 wkr_arity = dataConRepArity data_con
214 wkr_info = noCafIdInfo
215 `setArityInfo` wkr_arity
216 `setAllStrictnessInfo` Just wkr_sig
217 `setUnfoldingInfo` evaldUnfolding -- Record that it's evaluated,
220 wkr_sig = mkStrictSig (mkTopDmdType (replicate wkr_arity topDmd) cpr_info)
221 -- Notice that we do *not* say the worker is strict
222 -- even if the data constructor is declared strict
223 -- e.g. data T = MkT !(Int,Int)
224 -- Why? Because the *wrapper* is strict (and its unfolding has case
225 -- expresssions that do the evals) but the *worker* itself is not.
226 -- If we pretend it is strict then when we see
227 -- case x of y -> $wMkT y
228 -- the simplifier thinks that y is "sure to be evaluated" (because
229 -- $wMkT is strict) and drops the case. No, $wMkT is not strict.
231 -- When the simplifer sees a pattern
232 -- case e of MkT x -> ...
233 -- it uses the dataConRepStrictness of MkT to mark x as evaluated;
234 -- but that's fine... dataConRepStrictness comes from the data con
235 -- not from the worker Id.
237 cpr_info | isProductTyCon tycon &&
240 wkr_arity <= mAX_CPR_SIZE = retCPR
242 -- RetCPR is only true for products that are real data types;
243 -- that is, not unboxed tuples or [non-recursive] newtypes
245 ----------- Wrappers for newtypes --------------
246 nt_wrap_id = mkGlobalId (DataConWrapId data_con) wrap_name wrap_ty nt_wrap_info
247 nt_wrap_info = noCafIdInfo -- The NoCaf-ness is set by noCafIdInfo
248 `setArityInfo` 1 -- Arity 1
249 `setUnfoldingInfo` newtype_unf
250 newtype_unf = ASSERT( isVanillaDataCon data_con &&
251 isSingleton orig_arg_tys )
252 -- No existentials on a newtype, but it can have a context
253 -- e.g. newtype Eq a => T a = MkT (...)
254 mkTopUnfolding $ Note InlineMe $
255 mkLams tyvars $ Lam id_arg1 $
256 mkNewTypeBody tycon result_ty (Var id_arg1)
258 id_arg1 = mkTemplateLocal 1 (head orig_arg_tys)
260 ----------- Wrappers for algebraic data types --------------
261 alg_wrap_id = mkGlobalId (DataConWrapId data_con) wrap_name wrap_ty alg_wrap_info
262 alg_wrap_info = noCafIdInfo -- The NoCaf-ness is set by noCafIdInfo
263 `setArityInfo` alg_arity
264 -- It's important to specify the arity, so that partial
265 -- applications are treated as values
266 `setUnfoldingInfo` alg_unf
267 `setAllStrictnessInfo` Just wrap_sig
269 all_strict_marks = dataConExStricts data_con ++ dataConStrictMarks data_con
270 wrap_sig = mkStrictSig (mkTopDmdType arg_dmds cpr_info)
271 arg_dmds = map mk_dmd all_strict_marks
272 mk_dmd str | isMarkedStrict str = evalDmd
273 | otherwise = lazyDmd
274 -- The Cpr info can be important inside INLINE rhss, where the
275 -- wrapper constructor isn't inlined.
276 -- And the argument strictness can be important too; we
277 -- may not inline a contructor when it is partially applied.
279 -- data W = C !Int !Int !Int
280 -- ...(let w = C x in ...(w p q)...)...
281 -- we want to see that w is strict in its two arguments
283 alg_unf = mkTopUnfolding $ Note InlineMe $
285 mkLams dict_args $ mkLams id_args $
286 foldr mk_case con_app
287 (zip (dict_args ++ id_args) all_strict_marks)
290 con_app i rep_ids = mkApps (Var wrk_id)
291 (map varToCoreExpr (tyvars ++ reverse rep_ids))
293 (dict_args,i2) = mkLocals 1 dict_tys
294 (id_args,i3) = mkLocals i2 orig_arg_tys
298 :: (Id, StrictnessMark) -- Arg, strictness
299 -> (Int -> [Id] -> CoreExpr) -- Body
300 -> Int -- Next rep arg id
301 -> [Id] -- Rep args so far, reversed
303 mk_case (arg,strict) body i rep_args
305 NotMarkedStrict -> body i (arg:rep_args)
307 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
309 Case (Var arg) arg result_ty [(DEFAULT,[], body i (arg:rep_args))]
312 -> case splitProductType "do_unbox" (idType arg) of
313 (tycon, tycon_args, con, tys) ->
314 Case (Var arg) arg result_ty
317 body i' (reverse con_args ++ rep_args))]
319 (con_args, i') = mkLocals i tys
321 mAX_CPR_SIZE :: Arity
323 -- We do not treat very big tuples as CPR-ish:
324 -- a) for a start we get into trouble because there aren't
325 -- "enough" unboxed tuple types (a tiresome restriction,
327 -- b) more importantly, big unboxed tuples get returned mainly
328 -- on the stack, and are often then allocated in the heap
329 -- by the caller. So doing CPR for them may in fact make
332 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
338 %************************************************************************
340 \subsection{Record selectors}
342 %************************************************************************
344 We're going to build a record selector unfolding that looks like this:
346 data T a b c = T1 { ..., op :: a, ...}
347 | T2 { ..., op :: a, ...}
350 sel = /\ a b c -> \ d -> case d of
355 Similarly for newtypes
357 newtype N a = MkN { unN :: a->a }
360 unN n = coerce (a->a) n
362 We need to take a little care if the field has a polymorphic type:
364 data R = R { f :: forall a. a->a }
368 f :: forall a. R -> a -> a
369 f = /\ a \ r = case r of
372 (not f :: R -> forall a. a->a, which gives the type inference mechanism
373 problems at call sites)
375 Similarly for (recursive) newtypes
377 newtype N = MkN { unN :: forall a. a->a }
379 unN :: forall b. N -> b -> b
380 unN = /\b -> \n:N -> (coerce (forall a. a->a) n)
383 mkRecordSelId tycon field_label field_ty
384 -- Assumes that all fields with the same field label have the same type
387 sel_id = mkGlobalId (RecordSelId tycon field_label) field_label selector_ty info
388 data_cons = tyConDataCons tycon
389 tyvars = tyConTyVars tycon -- These scope over the types in
390 -- the FieldLabels of constructors of this type
391 data_ty = mkTyConApp tycon tyvar_tys
392 tyvar_tys = mkTyVarTys tyvars
394 -- Very tiresomely, the selectors are (unnecessarily!) overloaded over
395 -- just the dictionaries in the types of the constructors that contain
396 -- the relevant field. [The Report says that pattern matching on a
397 -- constructor gives the same constraints as applying it.] Urgh.
399 -- However, not all data cons have all constraints (because of
400 -- TcTyDecls.thinContext). So we need to find all the data cons
401 -- involved in the pattern match and take the union of their constraints.
403 -- NB: this code relies on the fact that DataCons are quantified over
404 -- the identical type variables as their parent TyCon
405 needed_preds = [pred | (DataAlt dc, _, _) <- the_alts, pred <- dataConStupidTheta dc]
406 dict_tys = mkPredTys (nubBy tcEqPred needed_preds)
407 n_dict_tys = length dict_tys
409 (field_tyvars,field_theta,field_tau) = tcSplitSigmaTy field_ty
410 field_dict_tys = mkPredTys field_theta
411 n_field_dict_tys = length field_dict_tys
412 -- If the field has a universally quantified type we have to
413 -- be a bit careful. Suppose we have
414 -- data R = R { op :: forall a. Foo a => a -> a }
415 -- Then we can't give op the type
416 -- op :: R -> forall a. Foo a => a -> a
417 -- because the typechecker doesn't understand foralls to the
418 -- right of an arrow. The "right" type to give it is
419 -- op :: forall a. Foo a => R -> a -> a
420 -- But then we must generate the right unfolding too:
421 -- op = /\a -> \dfoo -> \ r ->
424 -- Note that this is exactly the type we'd infer from a user defn
428 selector_ty = mkForAllTys tyvars $ mkForAllTys field_tyvars $
429 mkFunTys dict_tys $ mkFunTys field_dict_tys $
430 mkFunTy data_ty field_tau
432 arity = 1 + n_dict_tys + n_field_dict_tys
434 (strict_sig, rhs_w_str) = dmdAnalTopRhs sel_rhs
435 -- Use the demand analyser to work out strictness.
436 -- With all this unpackery it's not easy!
439 `setCafInfo` caf_info
441 `setUnfoldingInfo` mkTopUnfolding rhs_w_str
442 `setAllStrictnessInfo` Just strict_sig
444 -- Allocate Ids. We do it a funny way round because field_dict_tys is
445 -- almost always empty. Also note that we use max_dict_tys
446 -- rather than n_dict_tys, because the latter gives an infinite loop:
447 -- n_dict tys depends on the_alts, which depens on arg_ids, which depends
448 -- on arity, which depends on n_dict tys. Sigh! Mega sigh!
449 dict_ids = mkTemplateLocalsNum 1 dict_tys
450 max_dict_tys = length (tyConStupidTheta tycon)
451 field_dict_base = max_dict_tys + 1
452 field_dict_ids = mkTemplateLocalsNum field_dict_base field_dict_tys
453 dict_id_base = field_dict_base + n_field_dict_tys
454 data_id = mkTemplateLocal dict_id_base data_ty
455 arg_base = dict_id_base + 1
457 alts = map mk_maybe_alt data_cons
458 the_alts = catMaybes alts -- Already sorted by data-con
460 no_default = all isJust alts -- No default needed
461 default_alt | no_default = []
462 | otherwise = [(DEFAULT, [], error_expr)]
464 -- The default branch may have CAF refs, because it calls recSelError etc.
465 caf_info | no_default = NoCafRefs
466 | otherwise = MayHaveCafRefs
468 sel_rhs = mkLams tyvars $ mkLams field_tyvars $
469 mkLams dict_ids $ mkLams field_dict_ids $
470 Lam data_id $ sel_body
472 sel_body | isNewTyCon tycon = mk_result (mkNewTypeBody tycon field_ty (Var data_id))
473 | otherwise = Case (Var data_id) data_id field_tau (default_alt ++ the_alts)
475 mk_result poly_result = mkVarApps (mkVarApps poly_result field_tyvars) field_dict_ids
476 -- We pull the field lambdas to the top, so we need to
477 -- apply them in the body. For example:
478 -- data T = MkT { foo :: forall a. a->a }
480 -- foo :: forall a. T -> a -> a
481 -- foo = /\a. \t:T. case t of { MkT f -> f a }
483 mk_maybe_alt data_con
484 = ASSERT( dc_tyvars == tyvars )
485 -- The only non-vanilla case we allow is when we have an existential
486 -- context that binds no type variables, thus
487 -- data T a = (?v::Int) => MkT a
488 -- In the non-vanilla case, the pattern must bind type variables and
489 -- the context stuff; hence the arg_prefix binding below
491 case maybe_the_arg_id of
493 Just the_arg_id -> Just (mkReboxingAlt uniqs data_con (arg_prefix ++ arg_src_ids) $
494 mk_result (Var the_arg_id))
496 (dc_tyvars, dc_theta, dc_arg_tys, _, _) = dataConSig data_con
497 arg_src_ids = mkTemplateLocalsNum arg_base dc_arg_tys
498 arg_base' = arg_base + length arg_src_ids
499 arg_prefix | isVanillaDataCon data_con = []
500 | otherwise = tyvars ++ mkTemplateLocalsNum arg_base' (mkPredTys dc_theta)
502 unpack_base = arg_base' + length dc_theta
503 uniqs = map mkBuiltinUnique [unpack_base..]
505 maybe_the_arg_id = assocMaybe (field_lbls `zip` arg_src_ids) field_label
506 field_lbls = dataConFieldLabels data_con
508 error_expr = mkRuntimeErrorApp rEC_SEL_ERROR_ID field_tau full_msg
509 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
512 -- (mkReboxingAlt us con xs rhs) basically constructs the case
513 -- alternative (con, xs, rhs)
514 -- but it does the reboxing necessary to construct the *source*
515 -- arguments, xs, from the representation arguments ys.
517 -- data T = MkT !(Int,Int) Bool
519 -- mkReboxingAlt MkT [x,b] r
520 -- = (DataAlt MkT, [y::Int,z::Int,b], let x = (y,z) in r)
522 -- mkDataAlt should really be in DataCon, but it can't because
523 -- it manipulates CoreSyn.
526 :: [Unique] -- Uniques for the new Ids
528 -> [Var] -- Source-level args, including existential dicts
532 mkReboxingAlt us con args rhs
533 | not (any isMarkedUnboxed stricts)
534 = (DataAlt con, args, rhs)
538 (binds, args') = go args stricts us
540 (DataAlt con, args', mkLets binds rhs)
543 stricts = dataConExStricts con ++ dataConStrictMarks con
545 go [] stricts us = ([], [])
547 -- Type variable case
548 go (arg:args) stricts us
550 = let (binds, args') = go args stricts us
551 in (binds, arg:args')
553 -- Term variable case
554 go (arg:args) (str:stricts) us
555 | isMarkedUnboxed str
557 (_, tycon_args, pack_con, con_arg_tys)
558 = splitProductType "mkReboxingAlt" (idType arg)
560 unpacked_args = zipWith (mkSysLocal FSLIT("rb")) us con_arg_tys
561 (binds, args') = go args stricts (dropList con_arg_tys us)
562 con_app = mkConApp pack_con (map Type tycon_args ++ map Var unpacked_args)
564 (NonRec arg con_app : binds, unpacked_args ++ args')
567 = let (binds, args') = go args stricts us
568 in (binds, arg:args')
572 %************************************************************************
574 \subsection{Dictionary selectors}
576 %************************************************************************
578 Selecting a field for a dictionary. If there is just one field, then
579 there's nothing to do.
581 Dictionary selectors may get nested forall-types. Thus:
584 op :: forall b. Ord b => a -> b -> b
586 Then the top-level type for op is
588 op :: forall a. Foo a =>
592 This is unlike ordinary record selectors, which have all the for-alls
593 at the outside. When dealing with classes it's very convenient to
594 recover the original type signature from the class op selector.
597 mkDictSelId :: Name -> Class -> Id
598 mkDictSelId name clas
599 = mkGlobalId (ClassOpId clas) name sel_ty info
601 sel_ty = mkForAllTys tyvars (mkFunTy (idType dict_id) (idType the_arg_id))
602 -- We can't just say (exprType rhs), because that would give a type
604 -- for a single-op class (after all, the selector is the identity)
605 -- But it's type must expose the representation of the dictionary
606 -- to gat (say) C a -> (a -> a)
610 `setUnfoldingInfo` mkTopUnfolding rhs
611 `setAllStrictnessInfo` Just strict_sig
613 -- We no longer use 'must-inline' on record selectors. They'll
614 -- inline like crazy if they scrutinise a constructor
616 -- The strictness signature is of the form U(AAAVAAAA) -> T
617 -- where the V depends on which item we are selecting
618 -- It's worth giving one, so that absence info etc is generated
619 -- even if the selector isn't inlined
620 strict_sig = mkStrictSig (mkTopDmdType [arg_dmd] TopRes)
621 arg_dmd | isNewTyCon tycon = evalDmd
622 | otherwise = Eval (Prod [ if the_arg_id == id then evalDmd else Abs
625 tycon = classTyCon clas
626 [data_con] = tyConDataCons tycon
627 tyvars = dataConTyVars data_con
628 arg_tys = dataConRepArgTys data_con
629 the_arg_id = assoc "MkId.mkDictSelId" (map idName (classSelIds clas) `zip` arg_ids) name
631 pred = mkClassPred clas (mkTyVarTys tyvars)
632 (dict_id:arg_ids) = mkTemplateLocals (mkPredTy pred : arg_tys)
634 rhs | isNewTyCon tycon = mkLams tyvars $ Lam dict_id $
635 mkNewTypeBody tycon (head arg_tys) (Var dict_id)
636 | otherwise = mkLams tyvars $ Lam dict_id $
637 Case (Var dict_id) dict_id (idType the_arg_id)
638 [(DataAlt data_con, arg_ids, Var the_arg_id)]
640 mkNewTypeBody tycon result_ty result_expr
641 -- Adds a coerce where necessary
642 -- Used for both wrapping and unwrapping
643 | isRecursiveTyCon tycon -- Recursive case; use a coerce
644 = Note (Coerce result_ty (exprType result_expr)) result_expr
645 | otherwise -- Normal case
650 %************************************************************************
652 \subsection{Primitive operations
654 %************************************************************************
657 mkPrimOpId :: PrimOp -> Id
661 (tyvars,arg_tys,res_ty, arity, strict_sig) = primOpSig prim_op
662 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
663 name = mkWiredInName gHC_PRIM (primOpOcc prim_op)
664 (mkPrimOpIdUnique (primOpTag prim_op))
665 Nothing (AnId id) UserSyntax
666 id = mkGlobalId (PrimOpId prim_op) name ty info
671 `setAllStrictnessInfo` Just strict_sig
673 rules = foldl (addRule id) emptyCoreRules (primOpRules prim_op)
676 -- For each ccall we manufacture a separate CCallOpId, giving it
677 -- a fresh unique, a type that is correct for this particular ccall,
678 -- and a CCall structure that gives the correct details about calling
681 -- The *name* of this Id is a local name whose OccName gives the full
682 -- details of the ccall, type and all. This means that the interface
683 -- file reader can reconstruct a suitable Id
685 mkFCallId :: Unique -> ForeignCall -> Type -> Id
686 mkFCallId uniq fcall ty
687 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
688 -- A CCallOpId should have no free type variables;
689 -- when doing substitutions won't substitute over it
690 mkGlobalId (FCallId fcall) name ty info
692 occ_str = showSDoc (braces (ppr fcall <+> ppr ty))
693 -- The "occurrence name" of a ccall is the full info about the
694 -- ccall; it is encoded, but may have embedded spaces etc!
696 name = mkFCallName uniq occ_str
700 `setAllStrictnessInfo` Just strict_sig
702 (_, tau) = tcSplitForAllTys ty
703 (arg_tys, _) = tcSplitFunTys tau
704 arity = length arg_tys
705 strict_sig = mkStrictSig (mkTopDmdType (replicate arity evalDmd) TopRes)
709 %************************************************************************
711 \subsection{DictFuns and default methods}
713 %************************************************************************
715 Important notes about dict funs and default methods
716 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
717 Dict funs and default methods are *not* ImplicitIds. Their definition
718 involves user-written code, so we can't figure out their strictness etc
719 based on fixed info, as we can for constructors and record selectors (say).
721 We build them as GlobalIds, but when in the module where they are
722 bound, we turn the Id at the *binding site* into an exported LocalId.
723 This ensures that they are taken to account by free-variable finding
724 and dependency analysis (e.g. CoreFVs.exprFreeVars). The simplifier
725 will propagate the LocalId to all occurrence sites.
727 Why shouldn't they be bound as GlobalIds? Because, in particular, if
728 they are globals, the specialiser floats dict uses above their defns,
729 which prevents good simplifications happening. Also the strictness
730 analyser treats a occurrence of a GlobalId as imported and assumes it
731 contains strictness in its IdInfo, which isn't true if the thing is
732 bound in the same module as the occurrence.
734 It's OK for dfuns to be LocalIds, because we form the instance-env to
735 pass on to the next module (md_insts) in CoreTidy, afer tidying
736 and globalising the top-level Ids.
738 BUT make sure they are *exported* LocalIds (mkExportedLocalId) so
739 that they aren't discarded by the occurrence analyser.
742 mkDefaultMethodId dm_name ty = mkExportedLocalId dm_name ty
744 mkDictFunId :: Name -- Name to use for the dict fun;
751 mkDictFunId dfun_name inst_tyvars dfun_theta clas inst_tys
752 = mkExportedLocalId dfun_name dfun_ty
754 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
756 {- 1 dec 99: disable the Mark Jones optimisation for the sake
757 of compatibility with Hugs.
758 See `types/InstEnv' for a discussion related to this.
760 (class_tyvars, sc_theta, _, _) = classBigSig clas
761 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
762 sc_theta' = substClasses (zipTopTvSubst class_tyvars inst_tys) sc_theta
763 dfun_theta = case inst_decl_theta of
764 [] -> [] -- If inst_decl_theta is empty, then we don't
765 -- want to have any dict arguments, so that we can
766 -- expose the constant methods.
768 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
769 -- Otherwise we pass the superclass dictionaries to
770 -- the dictionary function; the Mark Jones optimisation.
772 -- NOTE the "nub". I got caught by this one:
773 -- class Monad m => MonadT t m where ...
774 -- instance Monad m => MonadT (EnvT env) m where ...
775 -- Here, the inst_decl_theta has (Monad m); but so
776 -- does the sc_theta'!
778 -- NOTE the "not_const". I got caught by this one too:
779 -- class Foo a => Baz a b where ...
780 -- instance Wob b => Baz T b where..
781 -- Now sc_theta' has Foo T
786 %************************************************************************
788 \subsection{Un-definable}
790 %************************************************************************
792 These Ids can't be defined in Haskell. They could be defined in
793 unfoldings in the wired-in GHC.Prim interface file, but we'd have to
794 ensure that they were definitely, definitely inlined, because there is
795 no curried identifier for them. That's what mkCompulsoryUnfolding
796 does. If we had a way to get a compulsory unfolding from an interface
797 file, we could do that, but we don't right now.
799 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
800 just gets expanded into a type coercion wherever it occurs. Hence we
801 add it as a built-in Id with an unfolding here.
803 The type variables we use here are "open" type variables: this means
804 they can unify with both unlifted and lifted types. Hence we provide
805 another gun with which to shoot yourself in the foot.
808 mkWiredInIdName mod fs uniq id
809 = mkWiredInName mod (mkOccFS varName fs) uniq Nothing (AnId id) UserSyntax
811 unsafeCoerceName = mkWiredInIdName gHC_PRIM FSLIT("unsafeCoerce#") unsafeCoerceIdKey unsafeCoerceId
812 nullAddrName = mkWiredInIdName gHC_PRIM FSLIT("nullAddr#") nullAddrIdKey nullAddrId
813 seqName = mkWiredInIdName gHC_PRIM FSLIT("seq") seqIdKey seqId
814 realWorldName = mkWiredInIdName gHC_PRIM FSLIT("realWorld#") realWorldPrimIdKey realWorldPrimId
815 lazyIdName = mkWiredInIdName pREL_BASE FSLIT("lazy") lazyIdKey lazyId
817 errorName = mkWiredInIdName pREL_ERR FSLIT("error") errorIdKey eRROR_ID
818 recSelErrorName = mkWiredInIdName pREL_ERR FSLIT("recSelError") recSelErrorIdKey rEC_SEL_ERROR_ID
819 runtimeErrorName = mkWiredInIdName pREL_ERR FSLIT("runtimeError") runtimeErrorIdKey rUNTIME_ERROR_ID
820 irrefutPatErrorName = mkWiredInIdName pREL_ERR FSLIT("irrefutPatError") irrefutPatErrorIdKey iRREFUT_PAT_ERROR_ID
821 recConErrorName = mkWiredInIdName pREL_ERR FSLIT("recConError") recConErrorIdKey rEC_CON_ERROR_ID
822 patErrorName = mkWiredInIdName pREL_ERR FSLIT("patError") patErrorIdKey pAT_ERROR_ID
823 noMethodBindingErrorName = mkWiredInIdName pREL_ERR FSLIT("noMethodBindingError")
824 noMethodBindingErrorIdKey nO_METHOD_BINDING_ERROR_ID
825 nonExhaustiveGuardsErrorName
826 = mkWiredInIdName pREL_ERR FSLIT("nonExhaustiveGuardsError")
827 nonExhaustiveGuardsErrorIdKey nON_EXHAUSTIVE_GUARDS_ERROR_ID
831 -- unsafeCoerce# :: forall a b. a -> b
833 = pcMiscPrelId unsafeCoerceName ty info
835 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
838 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
839 (mkFunTy openAlphaTy openBetaTy)
840 [x] = mkTemplateLocals [openAlphaTy]
841 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
842 Note (Coerce openBetaTy openAlphaTy) (Var x)
844 -- nullAddr# :: Addr#
845 -- The reason is is here is because we don't provide
846 -- a way to write this literal in Haskell.
848 = pcMiscPrelId nullAddrName addrPrimTy info
850 info = noCafIdInfo `setUnfoldingInfo`
851 mkCompulsoryUnfolding (Lit nullAddrLit)
854 = pcMiscPrelId seqName ty info
856 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
859 ty = mkForAllTys [alphaTyVar,openBetaTyVar]
860 (mkFunTy alphaTy (mkFunTy openBetaTy openBetaTy))
861 [x,y] = mkTemplateLocals [alphaTy, openBetaTy]
863 rhs = mkLams [alphaTyVar,openBetaTyVar,x,y] (Case (Var x) x openBetaTy [(DEFAULT, [], Var y)])
865 -- lazy :: forall a?. a? -> a? (i.e. works for unboxed types too)
866 -- Used to lazify pseq: pseq a b = a `seq` lazy b
867 -- No unfolding: it gets "inlined" by the worker/wrapper pass
868 -- Also, no strictness: by being a built-in Id, it overrides all
869 -- the info in PrelBase.hi. This is important, because the strictness
870 -- analyser will spot it as strict!
872 = pcMiscPrelId lazyIdName ty info
875 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy alphaTy)
877 lazyIdUnfolding :: CoreExpr -- Used to expand LazyOp after strictness anal
878 lazyIdUnfolding = mkLams [openAlphaTyVar,x] (Var x)
880 [x] = mkTemplateLocals [openAlphaTy]
883 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
884 nasty as-is, change it back to a literal (@Literal@).
886 voidArgId is a Local Id used simply as an argument in functions
887 where we just want an arg to avoid having a thunk of unlifted type.
889 x = \ void :: State# RealWorld -> (# p, q #)
891 This comes up in strictness analysis
894 realWorldPrimId -- :: State# RealWorld
895 = pcMiscPrelId realWorldName realWorldStatePrimTy
896 (noCafIdInfo `setUnfoldingInfo` evaldUnfolding)
897 -- The evaldUnfolding makes it look that realWorld# is evaluated
898 -- which in turn makes Simplify.interestingArg return True,
899 -- which in turn makes INLINE things applied to realWorld# likely
902 voidArgId -- :: State# RealWorld
903 = mkSysLocal FSLIT("void") voidArgIdKey realWorldStatePrimTy
907 %************************************************************************
909 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
911 %************************************************************************
913 GHC randomly injects these into the code.
915 @patError@ is just a version of @error@ for pattern-matching
916 failures. It knows various ``codes'' which expand to longer
917 strings---this saves space!
919 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
920 well shouldn't be yanked on, but if one is, then you will get a
921 friendly message from @absentErr@ (rather than a totally random
924 @parError@ is a special version of @error@ which the compiler does
925 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
926 templates, but we don't ever expect to generate code for it.
930 :: Id -- Should be of type (forall a. Addr# -> a)
931 -- where Addr# points to a UTF8 encoded string
932 -> Type -- The type to instantiate 'a'
933 -> String -- The string to print
936 mkRuntimeErrorApp err_id res_ty err_msg
937 = mkApps (Var err_id) [Type res_ty, err_string]
939 err_string = Lit (mkStringLit err_msg)
941 rEC_SEL_ERROR_ID = mkRuntimeErrorId recSelErrorName
942 rUNTIME_ERROR_ID = mkRuntimeErrorId runtimeErrorName
943 iRREFUT_PAT_ERROR_ID = mkRuntimeErrorId irrefutPatErrorName
944 rEC_CON_ERROR_ID = mkRuntimeErrorId recConErrorName
945 pAT_ERROR_ID = mkRuntimeErrorId patErrorName
946 nO_METHOD_BINDING_ERROR_ID = mkRuntimeErrorId noMethodBindingErrorName
947 nON_EXHAUSTIVE_GUARDS_ERROR_ID = mkRuntimeErrorId nonExhaustiveGuardsErrorName
949 -- The runtime error Ids take a UTF8-encoded string as argument
950 mkRuntimeErrorId name = pc_bottoming_Id name runtimeErrorTy
951 runtimeErrorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTy addrPrimTy openAlphaTy)
955 eRROR_ID = pc_bottoming_Id errorName errorTy
958 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy] openAlphaTy)
959 -- Notice the openAlphaTyVar. It says that "error" can be applied
960 -- to unboxed as well as boxed types. This is OK because it never
961 -- returns, so the return type is irrelevant.
965 %************************************************************************
967 \subsection{Utilities}
969 %************************************************************************
972 pcMiscPrelId :: Name -> Type -> IdInfo -> Id
973 pcMiscPrelId name ty info
974 = mkVanillaGlobal name ty info
975 -- We lie and say the thing is imported; otherwise, we get into
976 -- a mess with dependency analysis; e.g., core2stg may heave in
977 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
978 -- being compiled, then it's just a matter of luck if the definition
979 -- will be in "the right place" to be in scope.
981 pc_bottoming_Id name ty
982 = pcMiscPrelId name ty bottoming_info
984 bottoming_info = vanillaIdInfo `setAllStrictnessInfo` Just strict_sig
985 -- Do *not* mark them as NoCafRefs, because they can indeed have
986 -- CAF refs. For example, pAT_ERROR_ID calls GHC.Err.untangle,
987 -- which has some CAFs
988 -- In due course we may arrange that these error-y things are
989 -- regarded by the GC as permanently live, in which case we
990 -- can give them NoCaf info. As it is, any function that calls
991 -- any pc_bottoming_Id will itself have CafRefs, which bloats
994 strict_sig = mkStrictSig (mkTopDmdType [evalDmd] BotRes)
995 -- These "bottom" out, no matter what their arguments
997 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
998 openAlphaTy = mkTyVarTy openAlphaTyVar
999 openBetaTy = mkTyVarTy openBetaTyVar