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 ( addRules )
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 )
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 Util ( dropList, isSingleton )
91 import ListSetOps ( assoc, assocMaybe )
95 %************************************************************************
97 \subsection{Wired in Ids}
99 %************************************************************************
103 = [ -- These error-y things are wired in because we don't yet have
104 -- a way to express in an interface file that the result type variable
105 -- is 'open'; that is can be unified with an unboxed type
107 -- [The interface file format now carry such information, but there's
108 -- no way yet of expressing at the definition site for these
109 -- error-reporting functions that they have an 'open'
110 -- result type. -- sof 1/99]
112 eRROR_ID, -- This one isn't used anywhere else in the compiler
113 -- But we still need it in wiredInIds so that when GHC
114 -- compiles a program that mentions 'error' we don't
115 -- import its type from the interface file; we just get
116 -- the Id defined here. Which has an 'open-tyvar' type.
119 iRREFUT_PAT_ERROR_ID,
120 nON_EXHAUSTIVE_GUARDS_ERROR_ID,
121 nO_METHOD_BINDING_ERROR_ID,
128 -- These Ids are exported from GHC.Prim
130 = [ -- These can't be defined in Haskell, but they have
131 -- perfectly reasonable unfoldings in Core
139 %************************************************************************
141 \subsection{Data constructors}
143 %************************************************************************
145 The wrapper for a constructor is an ordinary top-level binding that evaluates
146 any strict args, unboxes any args that are going to be flattened, and calls
149 We're going to build a constructor that looks like:
151 data (Data a, C b) => T a b = T1 !a !Int b
154 \d1::Data a, d2::C b ->
155 \p q r -> case p of { p ->
157 Con T1 [a,b] [p,q,r]}}
161 * d2 is thrown away --- a context in a data decl is used to make sure
162 one *could* construct dictionaries at the site the constructor
163 is used, but the dictionary isn't actually used.
165 * We have to check that we can construct Data dictionaries for
166 the types a and Int. Once we've done that we can throw d1 away too.
168 * We use (case p of q -> ...) to evaluate p, rather than "seq" because
169 all that matters is that the arguments are evaluated. "seq" is
170 very careful to preserve evaluation order, which we don't need
173 You might think that we could simply give constructors some strictness
174 info, like PrimOps, and let CoreToStg do the let-to-case transformation.
175 But we don't do that because in the case of primops and functions strictness
176 is a *property* not a *requirement*. In the case of constructors we need to
177 do something active to evaluate the argument.
179 Making an explicit case expression allows the simplifier to eliminate
180 it in the (common) case where the constructor arg is already evaluated.
184 mkDataConIds :: Name -> Name -> DataCon -> DataConIds
185 -- Makes the *worker* for the data constructor; that is, the function
186 -- that takes the reprsentation arguments and builds the constructor.
187 mkDataConIds wrap_name wkr_name data_con
191 | any isMarkedStrict all_strict_marks -- Algebraic, needs wrapper
192 = AlgDC (Just alg_wrap_id) wrk_id
194 | otherwise -- Algebraic, no wrapper
195 = AlgDC Nothing wrk_id
197 (tyvars, theta, orig_arg_tys, tycon, res_tys) = dataConSig data_con
199 dict_tys = mkPredTys theta
200 all_arg_tys = dict_tys ++ orig_arg_tys
201 result_ty = mkTyConApp tycon res_tys
203 wrap_ty = mkForAllTys tyvars (mkFunTys all_arg_tys result_ty)
204 -- We used to include the stupid theta in the wrapper's args
205 -- but now we don't. Instead the type checker just injects these
206 -- extra constraints where necessary.
208 ----------- Worker (algebraic data types only) --------------
209 wrk_id = mkGlobalId (DataConWorkId data_con) wkr_name
210 (dataConRepType data_con) wkr_info
212 wkr_arity = dataConRepArity data_con
213 wkr_info = noCafIdInfo
214 `setArityInfo` wkr_arity
215 `setAllStrictnessInfo` Just wkr_sig
216 `setUnfoldingInfo` evaldUnfolding -- Record that it's evaluated,
219 wkr_sig = mkStrictSig (mkTopDmdType (replicate wkr_arity topDmd) cpr_info)
220 -- Notice that we do *not* say the worker is strict
221 -- even if the data constructor is declared strict
222 -- e.g. data T = MkT !(Int,Int)
223 -- Why? Because the *wrapper* is strict (and its unfolding has case
224 -- expresssions that do the evals) but the *worker* itself is not.
225 -- If we pretend it is strict then when we see
226 -- case x of y -> $wMkT y
227 -- the simplifier thinks that y is "sure to be evaluated" (because
228 -- $wMkT is strict) and drops the case. No, $wMkT is not strict.
230 -- When the simplifer sees a pattern
231 -- case e of MkT x -> ...
232 -- it uses the dataConRepStrictness of MkT to mark x as evaluated;
233 -- but that's fine... dataConRepStrictness comes from the data con
234 -- not from the worker Id.
236 cpr_info | isProductTyCon tycon &&
239 wkr_arity <= mAX_CPR_SIZE = retCPR
241 -- RetCPR is only true for products that are real data types;
242 -- that is, not unboxed tuples or [non-recursive] newtypes
244 ----------- Wrappers for newtypes --------------
245 nt_wrap_id = mkGlobalId (DataConWrapId data_con) wrap_name wrap_ty nt_wrap_info
246 nt_wrap_info = noCafIdInfo -- The NoCaf-ness is set by noCafIdInfo
247 `setArityInfo` 1 -- Arity 1
248 `setUnfoldingInfo` newtype_unf
249 newtype_unf = ASSERT( isVanillaDataCon data_con &&
250 isSingleton orig_arg_tys )
251 -- No existentials on a newtype, but it can have a context
252 -- e.g. newtype Eq a => T a = MkT (...)
253 mkTopUnfolding $ Note InlineMe $
254 mkLams tyvars $ Lam id_arg1 $
255 mkNewTypeBody tycon result_ty (Var id_arg1)
257 id_arg1 = mkTemplateLocal 1 (head orig_arg_tys)
259 ----------- Wrappers for algebraic data types --------------
260 alg_wrap_id = mkGlobalId (DataConWrapId data_con) wrap_name wrap_ty alg_wrap_info
261 alg_wrap_info = noCafIdInfo -- The NoCaf-ness is set by noCafIdInfo
262 `setArityInfo` alg_arity
263 -- It's important to specify the arity, so that partial
264 -- applications are treated as values
265 `setUnfoldingInfo` alg_unf
266 `setAllStrictnessInfo` Just wrap_sig
268 all_strict_marks = dataConExStricts data_con ++ dataConStrictMarks data_con
269 wrap_sig = mkStrictSig (mkTopDmdType arg_dmds cpr_info)
270 arg_dmds = map mk_dmd all_strict_marks
271 mk_dmd str | isMarkedStrict str = evalDmd
272 | otherwise = lazyDmd
273 -- The Cpr info can be important inside INLINE rhss, where the
274 -- wrapper constructor isn't inlined.
275 -- And the argument strictness can be important too; we
276 -- may not inline a contructor when it is partially applied.
278 -- data W = C !Int !Int !Int
279 -- ...(let w = C x in ...(w p q)...)...
280 -- we want to see that w is strict in its two arguments
282 alg_unf = mkTopUnfolding $ Note InlineMe $
284 mkLams dict_args $ mkLams id_args $
285 foldr mk_case con_app
286 (zip (dict_args ++ id_args) all_strict_marks)
289 con_app i rep_ids = mkApps (Var wrk_id)
290 (map varToCoreExpr (tyvars ++ reverse rep_ids))
292 (dict_args,i2) = mkLocals 1 dict_tys
293 (id_args,i3) = mkLocals i2 orig_arg_tys
297 :: (Id, StrictnessMark) -- Arg, strictness
298 -> (Int -> [Id] -> CoreExpr) -- Body
299 -> Int -- Next rep arg id
300 -> [Id] -- Rep args so far, reversed
302 mk_case (arg,strict) body i rep_args
304 NotMarkedStrict -> body i (arg:rep_args)
306 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
308 Case (Var arg) arg result_ty [(DEFAULT,[], body i (arg:rep_args))]
311 -> case splitProductType "do_unbox" (idType arg) of
312 (tycon, tycon_args, con, tys) ->
313 Case (Var arg) arg result_ty
316 body i' (reverse con_args ++ rep_args))]
318 (con_args, i') = mkLocals i tys
320 mAX_CPR_SIZE :: Arity
322 -- We do not treat very big tuples as CPR-ish:
323 -- a) for a start we get into trouble because there aren't
324 -- "enough" unboxed tuple types (a tiresome restriction,
326 -- b) more importantly, big unboxed tuples get returned mainly
327 -- on the stack, and are often then allocated in the heap
328 -- by the caller. So doing CPR for them may in fact make
331 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
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 (recursive) newtypes
376 newtype N = MkN { unN :: forall a. a->a }
378 unN :: forall b. N -> b -> b
379 unN = /\b -> \n:N -> (coerce (forall a. a->a) n)
382 mkRecordSelId tycon field_label field_ty
383 -- Assumes that all fields with the same field label have the same type
386 sel_id = mkGlobalId (RecordSelId tycon field_label) field_label selector_ty info
387 data_cons = tyConDataCons tycon
388 tyvars = tyConTyVars tycon -- These scope over the types in
389 -- the FieldLabels of constructors of this type
390 data_ty = mkTyConApp tycon tyvar_tys
391 tyvar_tys = mkTyVarTys tyvars
393 -- Very tiresomely, the selectors are (unnecessarily!) overloaded over
394 -- just the dictionaries in the types of the constructors that contain
395 -- the relevant field. [The Report says that pattern matching on a
396 -- constructor gives the same constraints as applying it.] Urgh.
398 -- However, not all data cons have all constraints (because of
399 -- TcTyDecls.thinContext). So we need to find all the data cons
400 -- involved in the pattern match and take the union of their constraints.
402 -- NB: this code relies on the fact that DataCons are quantified over
403 -- the identical type variables as their parent TyCon
404 needed_preds = [pred | (DataAlt dc, _, _) <- the_alts, pred <- dataConStupidTheta dc]
405 dict_tys = mkPredTys (nubBy tcEqPred needed_preds)
406 n_dict_tys = length dict_tys
408 (field_tyvars,field_theta,field_tau) = tcSplitSigmaTy field_ty
409 field_dict_tys = mkPredTys field_theta
410 n_field_dict_tys = length field_dict_tys
411 -- If the field has a universally quantified type we have to
412 -- be a bit careful. Suppose we have
413 -- data R = R { op :: forall a. Foo a => a -> a }
414 -- Then we can't give op the type
415 -- op :: R -> forall a. Foo a => a -> a
416 -- because the typechecker doesn't understand foralls to the
417 -- right of an arrow. The "right" type to give it is
418 -- op :: forall a. Foo a => R -> a -> a
419 -- But then we must generate the right unfolding too:
420 -- op = /\a -> \dfoo -> \ r ->
423 -- Note that this is exactly the type we'd infer from a user defn
427 selector_ty = mkForAllTys tyvars $ mkForAllTys field_tyvars $
428 mkFunTys dict_tys $ mkFunTys field_dict_tys $
429 mkFunTy data_ty field_tau
431 arity = 1 + n_dict_tys + n_field_dict_tys
433 (strict_sig, rhs_w_str) = dmdAnalTopRhs sel_rhs
434 -- Use the demand analyser to work out strictness.
435 -- With all this unpackery it's not easy!
438 `setCafInfo` caf_info
440 `setUnfoldingInfo` mkTopUnfolding rhs_w_str
441 `setAllStrictnessInfo` Just strict_sig
443 -- Allocate Ids. We do it a funny way round because field_dict_tys is
444 -- almost always empty. Also note that we use max_dict_tys
445 -- rather than n_dict_tys, because the latter gives an infinite loop:
446 -- n_dict tys depends on the_alts, which depens on arg_ids, which depends
447 -- on arity, which depends on n_dict tys. Sigh! Mega sigh!
448 dict_ids = mkTemplateLocalsNum 1 dict_tys
449 max_dict_tys = length (tyConStupidTheta tycon)
450 field_dict_base = max_dict_tys + 1
451 field_dict_ids = mkTemplateLocalsNum field_dict_base field_dict_tys
452 dict_id_base = field_dict_base + n_field_dict_tys
453 data_id = mkTemplateLocal dict_id_base data_ty
454 arg_base = dict_id_base + 1
456 alts = map mk_maybe_alt data_cons
457 the_alts = catMaybes alts -- Already sorted by data-con
459 no_default = all isJust alts -- No default needed
460 default_alt | no_default = []
461 | otherwise = [(DEFAULT, [], error_expr)]
463 -- The default branch may have CAF refs, because it calls recSelError etc.
464 caf_info | no_default = NoCafRefs
465 | otherwise = MayHaveCafRefs
467 sel_rhs = mkLams tyvars $ mkLams field_tyvars $
468 mkLams dict_ids $ mkLams field_dict_ids $
469 Lam data_id $ sel_body
471 sel_body | isNewTyCon tycon = mk_result (mkNewTypeBody tycon field_ty (Var data_id))
472 | otherwise = Case (Var data_id) data_id field_tau (default_alt ++ the_alts)
474 mk_result poly_result = mkVarApps (mkVarApps poly_result field_tyvars) field_dict_ids
475 -- We pull the field lambdas to the top, so we need to
476 -- apply them in the body. For example:
477 -- data T = MkT { foo :: forall a. a->a }
479 -- foo :: forall a. T -> a -> a
480 -- foo = /\a. \t:T. case t of { MkT f -> f a }
482 mk_maybe_alt data_con
483 = ASSERT( dc_tyvars == tyvars )
484 -- The only non-vanilla case we allow is when we have an existential
485 -- context that binds no type variables, thus
486 -- data T a = (?v::Int) => MkT a
487 -- In the non-vanilla case, the pattern must bind type variables and
488 -- the context stuff; hence the arg_prefix binding below
490 case maybe_the_arg_id of
492 Just the_arg_id -> Just (mkReboxingAlt uniqs data_con (arg_prefix ++ arg_src_ids) $
493 mk_result (Var the_arg_id))
495 (dc_tyvars, dc_theta, dc_arg_tys, _, _) = dataConSig data_con
496 arg_src_ids = mkTemplateLocalsNum arg_base dc_arg_tys
497 arg_base' = arg_base + length arg_src_ids
498 arg_prefix | isVanillaDataCon data_con = []
499 | otherwise = tyvars ++ mkTemplateLocalsNum arg_base' (mkPredTys dc_theta)
501 unpack_base = arg_base' + length dc_theta
502 uniqs = map mkBuiltinUnique [unpack_base..]
504 maybe_the_arg_id = assocMaybe (field_lbls `zip` arg_src_ids) field_label
505 field_lbls = dataConFieldLabels data_con
507 error_expr = mkRuntimeErrorApp rEC_SEL_ERROR_ID field_tau full_msg
508 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
511 -- (mkReboxingAlt us con xs rhs) basically constructs the case
512 -- alternative (con, xs, rhs)
513 -- but it does the reboxing necessary to construct the *source*
514 -- arguments, xs, from the representation arguments ys.
516 -- data T = MkT !(Int,Int) Bool
518 -- mkReboxingAlt MkT [x,b] r
519 -- = (DataAlt MkT, [y::Int,z::Int,b], let x = (y,z) in r)
521 -- mkDataAlt should really be in DataCon, but it can't because
522 -- it manipulates CoreSyn.
525 :: [Unique] -- Uniques for the new Ids
527 -> [Var] -- Source-level args, including existential dicts
531 mkReboxingAlt us con args rhs
532 | not (any isMarkedUnboxed stricts)
533 = (DataAlt con, args, rhs)
537 (binds, args') = go args stricts us
539 (DataAlt con, args', mkLets binds rhs)
542 stricts = dataConExStricts con ++ dataConStrictMarks con
544 go [] stricts us = ([], [])
546 -- Type variable case
547 go (arg:args) stricts us
549 = let (binds, args') = go args stricts us
550 in (binds, arg:args')
552 -- Term variable case
553 go (arg:args) (str:stricts) us
554 | isMarkedUnboxed str
556 (_, tycon_args, pack_con, con_arg_tys)
557 = splitProductType "mkReboxingAlt" (idType arg)
559 unpacked_args = zipWith (mkSysLocal FSLIT("rb")) us con_arg_tys
560 (binds, args') = go args stricts (dropList con_arg_tys us)
561 con_app = mkConApp pack_con (map Type tycon_args ++ map Var unpacked_args)
563 (NonRec arg con_app : binds, unpacked_args ++ args')
566 = let (binds, args') = go args stricts us
567 in (binds, arg:args')
571 %************************************************************************
573 \subsection{Dictionary selectors}
575 %************************************************************************
577 Selecting a field for a dictionary. If there is just one field, then
578 there's nothing to do.
580 Dictionary selectors may get nested forall-types. Thus:
583 op :: forall b. Ord b => a -> b -> b
585 Then the top-level type for op is
587 op :: forall a. Foo a =>
591 This is unlike ordinary record selectors, which have all the for-alls
592 at the outside. When dealing with classes it's very convenient to
593 recover the original type signature from the class op selector.
596 mkDictSelId :: Name -> Class -> Id
597 mkDictSelId name clas
598 = mkGlobalId (ClassOpId clas) name sel_ty info
600 sel_ty = mkForAllTys tyvars (mkFunTy (idType dict_id) (idType the_arg_id))
601 -- We can't just say (exprType rhs), because that would give a type
603 -- for a single-op class (after all, the selector is the identity)
604 -- But it's type must expose the representation of the dictionary
605 -- to gat (say) C a -> (a -> a)
609 `setUnfoldingInfo` mkTopUnfolding rhs
610 `setAllStrictnessInfo` Just strict_sig
612 -- We no longer use 'must-inline' on record selectors. They'll
613 -- inline like crazy if they scrutinise a constructor
615 -- The strictness signature is of the form U(AAAVAAAA) -> T
616 -- where the V depends on which item we are selecting
617 -- It's worth giving one, so that absence info etc is generated
618 -- even if the selector isn't inlined
619 strict_sig = mkStrictSig (mkTopDmdType [arg_dmd] TopRes)
620 arg_dmd | isNewTyCon tycon = evalDmd
621 | otherwise = Eval (Prod [ if the_arg_id == id then evalDmd else Abs
624 tycon = classTyCon clas
625 [data_con] = tyConDataCons tycon
626 tyvars = dataConTyVars data_con
627 arg_tys = dataConRepArgTys data_con
628 the_arg_id = assoc "MkId.mkDictSelId" (map idName (classSelIds clas) `zip` arg_ids) name
630 pred = mkClassPred clas (mkTyVarTys tyvars)
631 (dict_id:arg_ids) = mkTemplateLocals (mkPredTy pred : arg_tys)
633 rhs | isNewTyCon tycon = mkLams tyvars $ Lam dict_id $
634 mkNewTypeBody tycon (head arg_tys) (Var dict_id)
635 | otherwise = mkLams tyvars $ Lam dict_id $
636 Case (Var dict_id) dict_id (idType the_arg_id)
637 [(DataAlt data_con, arg_ids, Var the_arg_id)]
639 mkNewTypeBody tycon result_ty result_expr
640 -- Adds a coerce where necessary
641 -- Used for both wrapping and unwrapping
642 | isRecursiveTyCon tycon -- Recursive case; use a coerce
643 = Note (Coerce result_ty (exprType result_expr)) result_expr
644 | otherwise -- Normal case
649 %************************************************************************
651 \subsection{Primitive operations
653 %************************************************************************
656 mkPrimOpId :: PrimOp -> Id
660 (tyvars,arg_tys,res_ty, arity, strict_sig) = primOpSig prim_op
661 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
662 name = mkWiredInName gHC_PRIM (primOpOcc prim_op)
663 (mkPrimOpIdUnique (primOpTag prim_op))
664 Nothing (AnId id) UserSyntax
665 id = mkGlobalId (PrimOpId prim_op) name ty info
670 `setAllStrictnessInfo` Just strict_sig
672 rules = addRules id emptyCoreRules (primOpRules prim_op)
675 -- For each ccall we manufacture a separate CCallOpId, giving it
676 -- a fresh unique, a type that is correct for this particular ccall,
677 -- and a CCall structure that gives the correct details about calling
680 -- The *name* of this Id is a local name whose OccName gives the full
681 -- details of the ccall, type and all. This means that the interface
682 -- file reader can reconstruct a suitable Id
684 mkFCallId :: Unique -> ForeignCall -> Type -> Id
685 mkFCallId uniq fcall ty
686 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
687 -- A CCallOpId should have no free type variables;
688 -- when doing substitutions won't substitute over it
689 mkGlobalId (FCallId fcall) name ty info
691 occ_str = showSDoc (braces (ppr fcall <+> ppr ty))
692 -- The "occurrence name" of a ccall is the full info about the
693 -- ccall; it is encoded, but may have embedded spaces etc!
695 name = mkFCallName uniq occ_str
699 `setAllStrictnessInfo` Just strict_sig
701 (_, tau) = tcSplitForAllTys ty
702 (arg_tys, _) = tcSplitFunTys tau
703 arity = length arg_tys
704 strict_sig = mkStrictSig (mkTopDmdType (replicate arity evalDmd) TopRes)
708 %************************************************************************
710 \subsection{DictFuns and default methods}
712 %************************************************************************
714 Important notes about dict funs and default methods
715 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
716 Dict funs and default methods are *not* ImplicitIds. Their definition
717 involves user-written code, so we can't figure out their strictness etc
718 based on fixed info, as we can for constructors and record selectors (say).
720 We build them as GlobalIds, but when in the module where they are
721 bound, we turn the Id at the *binding site* into an exported LocalId.
722 This ensures that they are taken to account by free-variable finding
723 and dependency analysis (e.g. CoreFVs.exprFreeVars). The simplifier
724 will propagate the LocalId to all occurrence sites.
726 Why shouldn't they be bound as GlobalIds? Because, in particular, if
727 they are globals, the specialiser floats dict uses above their defns,
728 which prevents good simplifications happening. Also the strictness
729 analyser treats a occurrence of a GlobalId as imported and assumes it
730 contains strictness in its IdInfo, which isn't true if the thing is
731 bound in the same module as the occurrence.
733 It's OK for dfuns to be LocalIds, because we form the instance-env to
734 pass on to the next module (md_insts) in CoreTidy, afer tidying
735 and globalising the top-level Ids.
737 BUT make sure they are *exported* LocalIds (mkExportedLocalId) so
738 that they aren't discarded by the occurrence analyser.
741 mkDefaultMethodId dm_name ty = mkExportedLocalId dm_name ty
743 mkDictFunId :: Name -- Name to use for the dict fun;
750 mkDictFunId dfun_name inst_tyvars dfun_theta clas inst_tys
751 = mkExportedLocalId dfun_name dfun_ty
753 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
755 {- 1 dec 99: disable the Mark Jones optimisation for the sake
756 of compatibility with Hugs.
757 See `types/InstEnv' for a discussion related to this.
759 (class_tyvars, sc_theta, _, _) = classBigSig clas
760 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
761 sc_theta' = substClasses (zipTopTvSubst class_tyvars inst_tys) sc_theta
762 dfun_theta = case inst_decl_theta of
763 [] -> [] -- If inst_decl_theta is empty, then we don't
764 -- want to have any dict arguments, so that we can
765 -- expose the constant methods.
767 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
768 -- Otherwise we pass the superclass dictionaries to
769 -- the dictionary function; the Mark Jones optimisation.
771 -- NOTE the "nub". I got caught by this one:
772 -- class Monad m => MonadT t m where ...
773 -- instance Monad m => MonadT (EnvT env) m where ...
774 -- Here, the inst_decl_theta has (Monad m); but so
775 -- does the sc_theta'!
777 -- NOTE the "not_const". I got caught by this one too:
778 -- class Foo a => Baz a b where ...
779 -- instance Wob b => Baz T b where..
780 -- Now sc_theta' has Foo T
785 %************************************************************************
787 \subsection{Un-definable}
789 %************************************************************************
791 These Ids can't be defined in Haskell. They could be defined in
792 unfoldings in the wired-in GHC.Prim interface file, but we'd have to
793 ensure that they were definitely, definitely inlined, because there is
794 no curried identifier for them. That's what mkCompulsoryUnfolding
795 does. If we had a way to get a compulsory unfolding from an interface
796 file, we could do that, but we don't right now.
798 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
799 just gets expanded into a type coercion wherever it occurs. Hence we
800 add it as a built-in Id with an unfolding here.
802 The type variables we use here are "open" type variables: this means
803 they can unify with both unlifted and lifted types. Hence we provide
804 another gun with which to shoot yourself in the foot.
807 mkWiredInIdName mod fs uniq id
808 = mkWiredInName mod (mkOccFS varName fs) uniq Nothing (AnId id) UserSyntax
810 unsafeCoerceName = mkWiredInIdName gHC_PRIM FSLIT("unsafeCoerce#") unsafeCoerceIdKey unsafeCoerceId
811 nullAddrName = mkWiredInIdName gHC_PRIM FSLIT("nullAddr#") nullAddrIdKey nullAddrId
812 seqName = mkWiredInIdName gHC_PRIM FSLIT("seq") seqIdKey seqId
813 realWorldName = mkWiredInIdName gHC_PRIM FSLIT("realWorld#") realWorldPrimIdKey realWorldPrimId
814 lazyIdName = mkWiredInIdName pREL_BASE FSLIT("lazy") lazyIdKey lazyId
816 errorName = mkWiredInIdName pREL_ERR FSLIT("error") errorIdKey eRROR_ID
817 recSelErrorName = mkWiredInIdName pREL_ERR FSLIT("recSelError") recSelErrorIdKey rEC_SEL_ERROR_ID
818 runtimeErrorName = mkWiredInIdName pREL_ERR FSLIT("runtimeError") runtimeErrorIdKey rUNTIME_ERROR_ID
819 irrefutPatErrorName = mkWiredInIdName pREL_ERR FSLIT("irrefutPatError") irrefutPatErrorIdKey iRREFUT_PAT_ERROR_ID
820 recConErrorName = mkWiredInIdName pREL_ERR FSLIT("recConError") recConErrorIdKey rEC_CON_ERROR_ID
821 patErrorName = mkWiredInIdName pREL_ERR FSLIT("patError") patErrorIdKey pAT_ERROR_ID
822 noMethodBindingErrorName = mkWiredInIdName pREL_ERR FSLIT("noMethodBindingError")
823 noMethodBindingErrorIdKey nO_METHOD_BINDING_ERROR_ID
824 nonExhaustiveGuardsErrorName
825 = mkWiredInIdName pREL_ERR FSLIT("nonExhaustiveGuardsError")
826 nonExhaustiveGuardsErrorIdKey nON_EXHAUSTIVE_GUARDS_ERROR_ID
830 -- unsafeCoerce# :: forall a b. a -> b
832 = pcMiscPrelId unsafeCoerceName ty info
834 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
837 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
838 (mkFunTy openAlphaTy openBetaTy)
839 [x] = mkTemplateLocals [openAlphaTy]
840 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
841 Note (Coerce openBetaTy openAlphaTy) (Var x)
843 -- nullAddr# :: Addr#
844 -- The reason is is here is because we don't provide
845 -- a way to write this literal in Haskell.
847 = pcMiscPrelId nullAddrName addrPrimTy info
849 info = noCafIdInfo `setUnfoldingInfo`
850 mkCompulsoryUnfolding (Lit nullAddrLit)
853 = pcMiscPrelId seqName ty info
855 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
858 ty = mkForAllTys [alphaTyVar,openBetaTyVar]
859 (mkFunTy alphaTy (mkFunTy openBetaTy openBetaTy))
860 [x,y] = mkTemplateLocals [alphaTy, openBetaTy]
862 rhs = mkLams [alphaTyVar,openBetaTyVar,x,y] (Case (Var x) x openBetaTy [(DEFAULT, [], Var y)])
864 -- lazy :: forall a?. a? -> a? (i.e. works for unboxed types too)
865 -- Used to lazify pseq: pseq a b = a `seq` lazy b
866 -- No unfolding: it gets "inlined" by the worker/wrapper pass
867 -- Also, no strictness: by being a built-in Id, it overrides all
868 -- the info in PrelBase.hi. This is important, because the strictness
869 -- analyser will spot it as strict!
871 = pcMiscPrelId lazyIdName ty info
874 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy alphaTy)
876 lazyIdUnfolding :: CoreExpr -- Used to expand LazyOp after strictness anal
877 lazyIdUnfolding = mkLams [openAlphaTyVar,x] (Var x)
879 [x] = mkTemplateLocals [openAlphaTy]
882 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
883 nasty as-is, change it back to a literal (@Literal@).
885 voidArgId is a Local Id used simply as an argument in functions
886 where we just want an arg to avoid having a thunk of unlifted type.
888 x = \ void :: State# RealWorld -> (# p, q #)
890 This comes up in strictness analysis
893 realWorldPrimId -- :: State# RealWorld
894 = pcMiscPrelId realWorldName realWorldStatePrimTy
895 (noCafIdInfo `setUnfoldingInfo` evaldUnfolding)
896 -- The evaldUnfolding makes it look that realWorld# is evaluated
897 -- which in turn makes Simplify.interestingArg return True,
898 -- which in turn makes INLINE things applied to realWorld# likely
901 voidArgId -- :: State# RealWorld
902 = mkSysLocal FSLIT("void") voidArgIdKey realWorldStatePrimTy
906 %************************************************************************
908 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
910 %************************************************************************
912 GHC randomly injects these into the code.
914 @patError@ is just a version of @error@ for pattern-matching
915 failures. It knows various ``codes'' which expand to longer
916 strings---this saves space!
918 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
919 well shouldn't be yanked on, but if one is, then you will get a
920 friendly message from @absentErr@ (rather than a totally random
923 @parError@ is a special version of @error@ which the compiler does
924 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
925 templates, but we don't ever expect to generate code for it.
929 :: Id -- Should be of type (forall a. Addr# -> a)
930 -- where Addr# points to a UTF8 encoded string
931 -> Type -- The type to instantiate 'a'
932 -> String -- The string to print
935 mkRuntimeErrorApp err_id res_ty err_msg
936 = mkApps (Var err_id) [Type res_ty, err_string]
938 err_string = Lit (mkStringLit err_msg)
940 rEC_SEL_ERROR_ID = mkRuntimeErrorId recSelErrorName
941 rUNTIME_ERROR_ID = mkRuntimeErrorId runtimeErrorName
942 iRREFUT_PAT_ERROR_ID = mkRuntimeErrorId irrefutPatErrorName
943 rEC_CON_ERROR_ID = mkRuntimeErrorId recConErrorName
944 pAT_ERROR_ID = mkRuntimeErrorId patErrorName
945 nO_METHOD_BINDING_ERROR_ID = mkRuntimeErrorId noMethodBindingErrorName
946 nON_EXHAUSTIVE_GUARDS_ERROR_ID = mkRuntimeErrorId nonExhaustiveGuardsErrorName
948 -- The runtime error Ids take a UTF8-encoded string as argument
949 mkRuntimeErrorId name = pc_bottoming_Id name runtimeErrorTy
950 runtimeErrorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTy addrPrimTy openAlphaTy)
954 eRROR_ID = pc_bottoming_Id errorName errorTy
957 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy] openAlphaTy)
958 -- Notice the openAlphaTyVar. It says that "error" can be applied
959 -- to unboxed as well as boxed types. This is OK because it never
960 -- returns, so the return type is irrelevant.
964 %************************************************************************
966 \subsection{Utilities}
968 %************************************************************************
971 pcMiscPrelId :: Name -> Type -> IdInfo -> Id
972 pcMiscPrelId name ty info
973 = mkVanillaGlobal name ty info
974 -- We lie and say the thing is imported; otherwise, we get into
975 -- a mess with dependency analysis; e.g., core2stg may heave in
976 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
977 -- being compiled, then it's just a matter of luck if the definition
978 -- will be in "the right place" to be in scope.
980 pc_bottoming_Id name ty
981 = pcMiscPrelId name ty bottoming_info
983 bottoming_info = vanillaIdInfo `setAllStrictnessInfo` Just strict_sig
984 -- Do *not* mark them as NoCafRefs, because they can indeed have
985 -- CAF refs. For example, pAT_ERROR_ID calls GHC.Err.untangle,
986 -- which has some CAFs
987 -- In due course we may arrange that these error-y things are
988 -- regarded by the GC as permanently live, in which case we
989 -- can give them NoCaf info. As it is, any function that calls
990 -- any pc_bottoming_Id will itself have CafRefs, which bloats
993 strict_sig = mkStrictSig (mkTopDmdType [evalDmd] BotRes)
994 -- These "bottom" out, no matter what their arguments
996 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
997 openAlphaTy = mkTyVarTy openAlphaTyVar
998 openBetaTy = mkTyVarTy openBetaTyVar