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 mkDataConWorkId, 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,
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,
36 #include "HsVersions.h"
39 import BasicTypes ( Arity, StrictnessMark(..), isMarkedUnboxed, isMarkedStrict )
40 import TysPrim ( openAlphaTyVars, alphaTyVar, alphaTy, betaTyVar, betaTy,
41 intPrimTy, realWorldStatePrimTy, addrPrimTy
43 import TysWiredIn ( charTy, mkListTy )
44 import PrelRules ( primOpRules )
45 import Rules ( addRule )
46 import TcType ( Type, ThetaType, mkDictTy, mkPredTys, mkTyConApp,
47 mkTyVarTys, mkClassPred, tcEqPred,
48 mkFunTys, mkFunTy, mkSigmaTy, tcSplitSigmaTy,
49 isUnLiftedType, mkForAllTys, mkTyVarTy, tyVarsOfType,
50 tcSplitFunTys, tcSplitForAllTys, mkPredTy
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 ( mkFCallName, Name )
61 import PrimOp ( PrimOp(DataToTagOp), primOpSig, mkPrimOpIdName )
62 import ForeignCall ( ForeignCall )
63 import DataCon ( DataCon,
64 dataConFieldLabels, dataConRepArity, dataConTyCon,
65 dataConArgTys, dataConRepType,
68 dataConSig, dataConStrictMarks, dataConWorkId,
71 import Id ( idType, mkGlobalId, mkVanillaGlobal, mkSysLocal, mkLocalId,
72 mkTemplateLocals, mkTemplateLocalsNum, setIdLocalExported,
73 mkTemplateLocal, idNewStrictness, idName
75 import IdInfo ( IdInfo, noCafIdInfo, hasCafIdInfo,
77 setArityInfo, setSpecInfo, setCafInfo,
79 GlobalIdDetails(..), CafInfo(..)
81 import NewDemand ( mkStrictSig, strictSigResInfo, DmdResult(..),
82 mkTopDmdType, topDmd, evalDmd, lazyDmd, retCPR,
83 Demand(..), Demands(..) )
84 import FieldLabel ( mkFieldLabel, fieldLabelName,
85 firstFieldLabelTag, allFieldLabelTags, fieldLabelType
87 import DmdAnal ( dmdAnalTopRhs )
89 import Unique ( mkBuiltinUnique )
92 import Maybe ( isJust )
93 import Util ( dropList, isSingleton )
96 import ListSetOps ( assoc, assocMaybe )
97 import UnicodeUtil ( stringToUtf8 )
101 %************************************************************************
103 \subsection{Wired in Ids}
105 %************************************************************************
109 = [ -- These error-y things are wired in because we don't yet have
110 -- a way to express in an interface file that the result type variable
111 -- is 'open'; that is can be unified with an unboxed type
113 -- [The interface file format now carry such information, but there's
114 -- no way yet of expressing at the definition site for these
115 -- error-reporting functions that they have an 'open'
116 -- result type. -- sof 1/99]
118 eRROR_ID, -- This one isn't used anywhere else in the compiler
119 -- But we still need it in wiredInIds so that when GHC
120 -- compiles a program that mentions 'error' we don't
121 -- import its type from the interface file; we just get
122 -- the Id defined here. Which has an 'open-tyvar' type.
125 iRREFUT_PAT_ERROR_ID,
126 nON_EXHAUSTIVE_GUARDS_ERROR_ID,
127 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
145 %************************************************************************
147 \subsection{Data constructors}
149 %************************************************************************
152 mkDataConWorkId :: Name -> DataCon -> Id
153 -- Makes the *worker* for the data constructor; that is, the function
154 -- that takes the reprsentation arguments and builds the constructor.
155 mkDataConWorkId wkr_name data_con
156 = mkGlobalId (DataConWorkId data_con) wkr_name
157 (dataConRepType data_con) info
161 `setAllStrictnessInfo` Just strict_sig
163 arity = dataConRepArity data_con
164 strict_sig = mkStrictSig (mkTopDmdType (replicate arity topDmd) cpr_info)
165 -- Notice that we do *not* say the worker is strict
166 -- even if the data constructor is declared strict
167 -- e.g. data T = MkT !(Int,Int)
168 -- Why? Because the *wrapper* is strict (and its unfolding has case
169 -- expresssions that do the evals) but the *worker* itself is not.
170 -- If we pretend it is strict then when we see
171 -- case x of y -> $wMkT y
172 -- the simplifier thinks that y is "sure to be evaluated" (because
173 -- $wMkT is strict) and drops the case. No, $wMkT is not strict.
175 -- When the simplifer sees a pattern
176 -- case e of MkT x -> ...
177 -- it uses the dataConRepStrictness of MkT to mark x as evaluated;
178 -- but that's fine... dataConRepStrictness comes from the data con
179 -- not from the worker Id.
181 tycon = dataConTyCon data_con
182 cpr_info | isProductTyCon tycon &&
185 arity <= mAX_CPR_SIZE = retCPR
187 -- RetCPR is only true for products that are real data types;
188 -- that is, not unboxed tuples or [non-recursive] newtypes
190 mAX_CPR_SIZE :: Arity
192 -- We do not treat very big tuples as CPR-ish:
193 -- a) for a start we get into trouble because there aren't
194 -- "enough" unboxed tuple types (a tiresome restriction,
196 -- b) more importantly, big unboxed tuples get returned mainly
197 -- on the stack, and are often then allocated in the heap
198 -- by the caller. So doing CPR for them may in fact make
202 The wrapper for a constructor is an ordinary top-level binding that evaluates
203 any strict args, unboxes any args that are going to be flattened, and calls
206 We're going to build a constructor that looks like:
208 data (Data a, C b) => T a b = T1 !a !Int b
211 \d1::Data a, d2::C b ->
212 \p q r -> case p of { p ->
214 Con T1 [a,b] [p,q,r]}}
218 * d2 is thrown away --- a context in a data decl is used to make sure
219 one *could* construct dictionaries at the site the constructor
220 is used, but the dictionary isn't actually used.
222 * We have to check that we can construct Data dictionaries for
223 the types a and Int. Once we've done that we can throw d1 away too.
225 * We use (case p of q -> ...) to evaluate p, rather than "seq" because
226 all that matters is that the arguments are evaluated. "seq" is
227 very careful to preserve evaluation order, which we don't need
230 You might think that we could simply give constructors some strictness
231 info, like PrimOps, and let CoreToStg do the let-to-case transformation.
232 But we don't do that because in the case of primops and functions strictness
233 is a *property* not a *requirement*. In the case of constructors we need to
234 do something active to evaluate the argument.
236 Making an explicit case expression allows the simplifier to eliminate
237 it in the (common) case where the constructor arg is already evaluated.
240 mkDataConWrapId :: Name -> DataCon -> Maybe Id
241 -- Only make a wrapper Id if necessary
243 mkDataConWrapId wrap_name data_con
244 | is_newtype || any isMarkedStrict strict_marks
245 = -- We need a wrapper function
246 Just (mkGlobalId (DataConWrapId data_con) wrap_name wrap_ty info)
249 = Nothing -- The common case, where there is no point in
250 -- having a wrapper function. Not only is this efficient,
251 -- but it also ensures that the wrapper is replaced
252 -- by the worker (becuase it *is* the wroker)
253 -- even when there are no args. E.g. in
255 -- the (:) *is* the worker.
256 -- This is really important in rule matching,
257 -- (We could match on the wrappers,
258 -- but that makes it less likely that rules will match
259 -- when we bring bits of unfoldings together.)
261 (tyvars, _, ex_tyvars, ex_theta, orig_arg_tys, tycon) = dataConSig data_con
262 is_newtype = isNewTyCon tycon
263 all_tyvars = tyvars ++ ex_tyvars
264 work_id = dataConWorkId data_con
266 common_info = noCafIdInfo -- The NoCaf-ness is set by noCafIdInfo
268 -- It's important to specify the arity, so that partial
269 -- applications are treated as values
271 info | is_newtype = common_info `setUnfoldingInfo` newtype_unf
272 | otherwise = common_info `setUnfoldingInfo` data_unf
273 `setAllStrictnessInfo` Just wrap_sig
275 wrap_sig = mkStrictSig (mkTopDmdType arg_dmds res_info)
276 res_info = strictSigResInfo (idNewStrictness work_id)
277 arg_dmds = map mk_dmd strict_marks
278 mk_dmd str | isMarkedStrict str = evalDmd
279 | otherwise = lazyDmd
280 -- The Cpr info can be important inside INLINE rhss, where the
281 -- wrapper constructor isn't inlined.
282 -- And the argument strictness can be important too; we
283 -- may not inline a contructor when it is partially applied.
285 -- data W = C !Int !Int !Int
286 -- ...(let w = C x in ...(w p q)...)...
287 -- we want to see that w is strict in its two arguments
289 newtype_unf = ASSERT( null ex_tyvars && null ex_dict_args &&
290 isSingleton orig_arg_tys )
291 -- No existentials on a newtype, but it can have a context
292 -- e.g. newtype Eq a => T a = MkT (...)
293 mkTopUnfolding $ Note InlineMe $
294 mkLams tyvars $ Lam id_arg1 $
295 mkNewTypeBody tycon result_ty (Var id_arg1)
297 data_unf = mkTopUnfolding $ Note InlineMe $
299 mkLams ex_dict_args $ mkLams id_args $
300 foldr mk_case con_app
301 (zip (ex_dict_args++id_args) strict_marks) i3 []
303 con_app i rep_ids = mkApps (Var work_id)
304 (map varToCoreExpr (all_tyvars ++ reverse rep_ids))
306 ex_dict_tys = mkPredTys ex_theta
307 all_arg_tys = ex_dict_tys ++ orig_arg_tys
308 result_ty = mkTyConApp tycon (mkTyVarTys tyvars)
310 wrap_ty = mkForAllTys all_tyvars (mkFunTys all_arg_tys result_ty)
311 -- We used to include the stupid theta in the wrapper's args
312 -- but now we don't. Instead the type checker just injects these
313 -- extra constraints where necessary.
315 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
319 (ex_dict_args,i2) = mkLocals 1 ex_dict_tys
320 (id_args,i3) = mkLocals i2 orig_arg_tys
322 (id_arg1:_) = id_args -- Used for newtype only
324 strict_marks = dataConStrictMarks data_con
327 :: (Id, StrictnessMark) -- Arg, strictness
328 -> (Int -> [Id] -> CoreExpr) -- Body
329 -> Int -- Next rep arg id
330 -> [Id] -- Rep args so far, reversed
332 mk_case (arg,strict) body i rep_args
334 NotMarkedStrict -> body i (arg:rep_args)
336 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
338 Case (Var arg) arg [(DEFAULT,[], body i (arg:rep_args))]
341 -> case splitProductType "do_unbox" (idType arg) of
342 (tycon, tycon_args, con, tys) ->
343 Case (Var arg) arg [(DataAlt con, con_args,
344 body i' (reverse con_args ++ rep_args))]
346 (con_args, i') = mkLocals i tys
350 %************************************************************************
352 \subsection{Record selectors}
354 %************************************************************************
356 We're going to build a record selector unfolding that looks like this:
358 data T a b c = T1 { ..., op :: a, ...}
359 | T2 { ..., op :: a, ...}
362 sel = /\ a b c -> \ d -> case d of
367 Similarly for newtypes
369 newtype N a = MkN { unN :: a->a }
372 unN n = coerce (a->a) n
374 We need to take a little care if the field has a polymorphic type:
376 data R = R { f :: forall a. a->a }
380 f :: forall a. R -> a -> a
381 f = /\ a \ r = case r of
384 (not f :: R -> forall a. a->a, which gives the type inference mechanism
385 problems at call sites)
387 Similarly for (recursive) newtypes
389 newtype N = MkN { unN :: forall a. a->a }
391 unN :: forall b. N -> b -> b
392 unN = /\b -> \n:N -> (coerce (forall a. a->a) n)
395 mkRecordSelId tycon field_label
396 -- Assumes that all fields with the same field label have the same type
398 -- Annoyingly, we have to pass in the unpackCString# Id, because
399 -- we can't conjure it up out of thin air
402 sel_id = mkGlobalId (RecordSelId field_label) (fieldLabelName field_label) selector_ty info
403 field_ty = fieldLabelType field_label
404 data_cons = tyConDataCons tycon
405 tyvars = tyConTyVars tycon -- These scope over the types in
406 -- the FieldLabels of constructors of this type
407 data_ty = mkTyConApp tycon tyvar_tys
408 tyvar_tys = mkTyVarTys tyvars
410 -- Very tiresomely, the selectors are (unnecessarily!) overloaded over
411 -- just the dictionaries in the types of the constructors that contain
412 -- the relevant field. [The Report says that pattern matching on a
413 -- constructor gives the same constraints as applying it.] Urgh.
415 -- However, not all data cons have all constraints (because of
416 -- TcTyDecls.thinContext). So we need to find all the data cons
417 -- involved in the pattern match and take the union of their constraints.
419 -- NB: this code relies on the fact that DataCons are quantified over
420 -- the identical type variables as their parent TyCon
421 tycon_theta = tyConTheta tycon -- The context on the data decl
422 -- eg data (Eq a, Ord b) => T a b = ...
423 needed_preds = [pred | (DataAlt dc, _, _) <- the_alts, pred <- dataConTheta dc]
424 dict_tys = map mkPredTy (nubBy tcEqPred needed_preds)
425 n_dict_tys = length dict_tys
427 (field_tyvars,field_theta,field_tau) = tcSplitSigmaTy field_ty
428 field_dict_tys = map mkPredTy field_theta
429 n_field_dict_tys = length field_dict_tys
430 -- If the field has a universally quantified type we have to
431 -- be a bit careful. Suppose we have
432 -- data R = R { op :: forall a. Foo a => a -> a }
433 -- Then we can't give op the type
434 -- op :: R -> forall a. Foo a => a -> a
435 -- because the typechecker doesn't understand foralls to the
436 -- right of an arrow. The "right" type to give it is
437 -- op :: forall a. Foo a => R -> a -> a
438 -- But then we must generate the right unfolding too:
439 -- op = /\a -> \dfoo -> \ r ->
442 -- Note that this is exactly the type we'd infer from a user defn
446 selector_ty = mkForAllTys tyvars $ mkForAllTys field_tyvars $
447 mkFunTys dict_tys $ mkFunTys field_dict_tys $
448 mkFunTy data_ty field_tau
450 arity = 1 + n_dict_tys + n_field_dict_tys
452 (strict_sig, rhs_w_str) = dmdAnalTopRhs sel_rhs
453 -- Use the demand analyser to work out strictness.
454 -- With all this unpackery it's not easy!
457 `setCafInfo` caf_info
459 `setUnfoldingInfo` mkTopUnfolding rhs_w_str
460 `setAllStrictnessInfo` Just strict_sig
462 -- Allocate Ids. We do it a funny way round because field_dict_tys is
463 -- almost always empty. Also note that we use length_tycon_theta
464 -- rather than n_dict_tys, because the latter gives an infinite loop:
465 -- n_dict tys depends on the_alts, which depens on arg_ids, which depends
466 -- on arity, which depends on n_dict tys. Sigh! Mega sigh!
467 field_dict_base = length tycon_theta + 1
468 dict_id_base = field_dict_base + n_field_dict_tys
469 field_base = dict_id_base + 1
470 dict_ids = mkTemplateLocalsNum 1 dict_tys
471 field_dict_ids = mkTemplateLocalsNum field_dict_base field_dict_tys
472 data_id = mkTemplateLocal dict_id_base data_ty
474 alts = map mk_maybe_alt data_cons
475 the_alts = catMaybes alts
477 no_default = all isJust alts -- No default needed
478 default_alt | no_default = []
479 | otherwise = [(DEFAULT, [], error_expr)]
481 -- The default branch may have CAF refs, because it calls recSelError etc.
482 caf_info | no_default = NoCafRefs
483 | otherwise = MayHaveCafRefs
485 sel_rhs = mkLams tyvars $ mkLams field_tyvars $
486 mkLams dict_ids $ mkLams field_dict_ids $
487 Lam data_id $ sel_body
489 sel_body | isNewTyCon tycon = mk_result (mkNewTypeBody tycon field_ty (Var data_id))
490 | otherwise = Case (Var data_id) data_id (default_alt ++ the_alts)
492 mk_result poly_result = mkVarApps (mkVarApps poly_result field_tyvars) field_dict_ids
493 -- We pull the field lambdas to the top, so we need to
494 -- apply them in the body. For example:
495 -- data T = MkT { foo :: forall a. a->a }
497 -- foo :: forall a. T -> a -> a
498 -- foo = /\a. \t:T. case t of { MkT f -> f a }
500 mk_maybe_alt data_con
501 = case maybe_the_arg_id of
503 Just the_arg_id -> Just (mkReboxingAlt uniqs data_con arg_ids body)
505 body = mk_result (Var the_arg_id)
507 arg_ids = mkTemplateLocalsNum field_base (dataConOrigArgTys data_con)
508 -- No need to instantiate; same tyvars in datacon as tycon
510 unpack_base = field_base + length arg_ids
511 uniqs = map mkBuiltinUnique [unpack_base..]
513 -- arity+1 avoids all shadowing
514 maybe_the_arg_id = assocMaybe (field_lbls `zip` arg_ids) field_label
515 field_lbls = dataConFieldLabels data_con
517 error_expr = mkRuntimeErrorApp rEC_SEL_ERROR_ID field_tau full_msg
518 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
521 -- (mkReboxingAlt us con xs rhs) basically constructs the case
522 -- alternative (con, xs, rhs)
523 -- but it does the reboxing necessary to construct the *source*
524 -- arguments, xs, from the representation arguments ys.
526 -- data T = MkT !(Int,Int) Bool
528 -- mkReboxingAlt MkT [x,b] r
529 -- = (DataAlt MkT, [y::Int,z::Int,b], let x = (y,z) in r)
531 -- mkDataAlt should really be in DataCon, but it can't because
532 -- it manipulates CoreSyn.
535 :: [Unique] -- Uniques for the new Ids
537 -> [Var] -- Source-level args
541 mkReboxingAlt us con args rhs
542 | not (any isMarkedUnboxed stricts)
543 = (DataAlt con, args, rhs)
547 (binds, args') = go args stricts us
549 (DataAlt con, args', mkLets binds rhs)
552 stricts = dataConStrictMarks con
554 go [] stricts us = ([], [])
556 -- Type variable case
557 go (arg:args) stricts us
559 = let (binds, args') = go args stricts us
560 in (binds, arg:args')
562 -- Term variable case
563 go (arg:args) (str:stricts) us
564 | isMarkedUnboxed str
566 (_, tycon_args, pack_con, con_arg_tys)
567 = splitProductType "mkReboxingAlt" (idType arg)
569 unpacked_args = zipWith (mkSysLocal FSLIT("rb")) us con_arg_tys
570 (binds, args') = go args stricts (dropList con_arg_tys us)
571 con_app = mkConApp pack_con (map Type tycon_args ++ map Var unpacked_args)
573 (NonRec arg con_app : binds, unpacked_args ++ args')
576 = let (binds, args') = go args stricts us
577 in (binds, arg:args')
581 %************************************************************************
583 \subsection{Dictionary selectors}
585 %************************************************************************
587 Selecting a field for a dictionary. If there is just one field, then
588 there's nothing to do.
590 Dictionary selectors may get nested forall-types. Thus:
593 op :: forall b. Ord b => a -> b -> b
595 Then the top-level type for op is
597 op :: forall a. Foo a =>
601 This is unlike ordinary record selectors, which have all the for-alls
602 at the outside. When dealing with classes it's very convenient to
603 recover the original type signature from the class op selector.
605 ToDo: unify with mkRecordSelId?
608 mkDictSelId :: Name -> Class -> Id
609 mkDictSelId name clas
610 = mkGlobalId (RecordSelId field_lbl) name sel_ty info
612 sel_ty = mkForAllTys tyvars (mkFunTy (idType dict_id) (idType the_arg_id))
613 -- We can't just say (exprType rhs), because that would give a type
615 -- for a single-op class (after all, the selector is the identity)
616 -- But it's type must expose the representation of the dictionary
617 -- to gat (say) C a -> (a -> a)
619 field_lbl = mkFieldLabel name tycon sel_ty tag
620 tag = assoc "MkId.mkDictSelId" (map idName (classSelIds clas) `zip` allFieldLabelTags) name
624 `setUnfoldingInfo` mkTopUnfolding rhs
625 `setAllStrictnessInfo` Just strict_sig
627 -- We no longer use 'must-inline' on record selectors. They'll
628 -- inline like crazy if they scrutinise a constructor
630 -- The strictness signature is of the form U(AAAVAAAA) -> T
631 -- where the V depends on which item we are selecting
632 -- It's worth giving one, so that absence info etc is generated
633 -- even if the selector isn't inlined
634 strict_sig = mkStrictSig (mkTopDmdType [arg_dmd] TopRes)
635 arg_dmd | isNewTyCon tycon = evalDmd
636 | otherwise = Eval (Prod [ if the_arg_id == id then evalDmd else Abs
639 tyvars = classTyVars clas
641 tycon = classTyCon clas
642 [data_con] = tyConDataCons tycon
643 tyvar_tys = mkTyVarTys tyvars
644 arg_tys = dataConArgTys data_con tyvar_tys
645 the_arg_id = arg_ids !! (tag - firstFieldLabelTag)
647 pred = mkClassPred clas tyvar_tys
648 (dict_id:arg_ids) = mkTemplateLocals (mkPredTy pred : arg_tys)
650 rhs | isNewTyCon tycon = mkLams tyvars $ Lam dict_id $
651 mkNewTypeBody tycon (head arg_tys) (Var dict_id)
652 | otherwise = mkLams tyvars $ Lam dict_id $
653 Case (Var dict_id) dict_id
654 [(DataAlt data_con, arg_ids, Var the_arg_id)]
656 mkNewTypeBody tycon result_ty result_expr
657 -- Adds a coerce where necessary
658 -- Used for both wrapping and unwrapping
659 | isRecursiveTyCon tycon -- Recursive case; use a coerce
660 = Note (Coerce result_ty (exprType result_expr)) result_expr
661 | otherwise -- Normal case
666 %************************************************************************
668 \subsection{Primitive operations
670 %************************************************************************
673 mkPrimOpId :: PrimOp -> Id
677 (tyvars,arg_tys,res_ty, arity, strict_sig) = primOpSig prim_op
678 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
679 name = mkPrimOpIdName prim_op
680 id = mkGlobalId (PrimOpId prim_op) name ty info
685 `setAllStrictnessInfo` Just strict_sig
687 rules = foldl (addRule id) emptyCoreRules (primOpRules prim_op)
690 -- For each ccall we manufacture a separate CCallOpId, giving it
691 -- a fresh unique, a type that is correct for this particular ccall,
692 -- and a CCall structure that gives the correct details about calling
695 -- The *name* of this Id is a local name whose OccName gives the full
696 -- details of the ccall, type and all. This means that the interface
697 -- file reader can reconstruct a suitable Id
699 mkFCallId :: Unique -> ForeignCall -> Type -> Id
700 mkFCallId uniq fcall ty
701 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
702 -- A CCallOpId should have no free type variables;
703 -- when doing substitutions won't substitute over it
704 mkGlobalId (FCallId fcall) name ty info
706 occ_str = showSDoc (braces (ppr fcall <+> ppr ty))
707 -- The "occurrence name" of a ccall is the full info about the
708 -- ccall; it is encoded, but may have embedded spaces etc!
710 name = mkFCallName uniq occ_str
714 `setAllStrictnessInfo` Just strict_sig
716 (_, tau) = tcSplitForAllTys ty
717 (arg_tys, _) = tcSplitFunTys tau
718 arity = length arg_tys
719 strict_sig = mkStrictSig (mkTopDmdType (replicate arity evalDmd) TopRes)
723 %************************************************************************
725 \subsection{DictFuns and default methods}
727 %************************************************************************
729 Important notes about dict funs and default methods
730 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
731 Dict funs and default methods are *not* ImplicitIds. Their definition
732 involves user-written code, so we can't figure out their strictness etc
733 based on fixed info, as we can for constructors and record selectors (say).
735 We build them as GlobalIds, but when in the module where they are
736 bound, we turn the Id at the *binding site* into an exported LocalId.
737 This ensures that they are taken to account by free-variable finding
738 and dependency analysis (e.g. CoreFVs.exprFreeVars). The simplifier
739 will propagate the LocalId to all occurrence sites.
741 Why shouldn't they be bound as GlobalIds? Because, in particular, if
742 they are globals, the specialiser floats dict uses above their defns,
743 which prevents good simplifications happening. Also the strictness
744 analyser treats a occurrence of a GlobalId as imported and assumes it
745 contains strictness in its IdInfo, which isn't true if the thing is
746 bound in the same module as the occurrence.
748 It's OK for dfuns to be LocalIds, because we form the instance-env to
749 pass on to the next module (md_insts) in CoreTidy, afer tidying
750 and globalising the top-level Ids.
752 BUT make sure they are *exported* LocalIds (setIdLocalExported) so
753 that they aren't discarded by the occurrence analyser.
756 mkDefaultMethodId dm_name ty
757 = setIdLocalExported (mkLocalId dm_name ty)
759 mkDictFunId :: Name -- Name to use for the dict fun;
766 mkDictFunId dfun_name inst_tyvars dfun_theta clas inst_tys
767 = setIdLocalExported (mkLocalId dfun_name dfun_ty)
769 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
771 {- 1 dec 99: disable the Mark Jones optimisation for the sake
772 of compatibility with Hugs.
773 See `types/InstEnv' for a discussion related to this.
775 (class_tyvars, sc_theta, _, _) = classBigSig clas
776 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
777 sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys) sc_theta
778 dfun_theta = case inst_decl_theta of
779 [] -> [] -- If inst_decl_theta is empty, then we don't
780 -- want to have any dict arguments, so that we can
781 -- expose the constant methods.
783 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
784 -- Otherwise we pass the superclass dictionaries to
785 -- the dictionary function; the Mark Jones optimisation.
787 -- NOTE the "nub". I got caught by this one:
788 -- class Monad m => MonadT t m where ...
789 -- instance Monad m => MonadT (EnvT env) m where ...
790 -- Here, the inst_decl_theta has (Monad m); but so
791 -- does the sc_theta'!
793 -- NOTE the "not_const". I got caught by this one too:
794 -- class Foo a => Baz a b where ...
795 -- instance Wob b => Baz T b where..
796 -- Now sc_theta' has Foo T
801 %************************************************************************
803 \subsection{Un-definable}
805 %************************************************************************
807 These Ids can't be defined in Haskell. They could be defined in
808 unfoldings in the wired-in GHC.Prim interface file, but we'd have to
809 ensure that they were definitely, definitely inlined, because there is
810 no curried identifier for them. That's what mkCompulsoryUnfolding
811 does. If we had a way to get a compulsory unfolding from an interface
812 file, we could do that, but we don't right now.
814 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
815 just gets expanded into a type coercion wherever it occurs. Hence we
816 add it as a built-in Id with an unfolding here.
818 The type variables we use here are "open" type variables: this means
819 they can unify with both unlifted and lifted types. Hence we provide
820 another gun with which to shoot yourself in the foot.
823 -- unsafeCoerce# :: forall a b. a -> b
825 = pcMiscPrelId unsafeCoerceName ty info
827 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
830 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
831 (mkFunTy openAlphaTy openBetaTy)
832 [x] = mkTemplateLocals [openAlphaTy]
833 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
834 Note (Coerce openBetaTy openAlphaTy) (Var x)
836 -- nullAddr# :: Addr#
837 -- The reason is is here is because we don't provide
838 -- a way to write this literal in Haskell.
840 = pcMiscPrelId nullAddrName addrPrimTy info
842 info = noCafIdInfo `setUnfoldingInfo`
843 mkCompulsoryUnfolding (Lit nullAddrLit)
846 = pcMiscPrelId seqName ty info
848 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
851 ty = mkForAllTys [alphaTyVar,openBetaTyVar]
852 (mkFunTy alphaTy (mkFunTy openBetaTy openBetaTy))
853 [x,y] = mkTemplateLocals [alphaTy, openBetaTy]
854 rhs = mkLams [alphaTyVar,openBetaTyVar,x,y] (Case (Var x) x [(DEFAULT, [], Var y)])
856 -- lazy :: forall a?. a? -> a? (i.e. works for unboxed types too)
857 -- Used to lazify pseq: pseq a b = a `seq` lazy b
858 -- No unfolding: it gets "inlined" by the worker/wrapper pass
859 -- Also, no strictness: by being a built-in Id, it overrides all
860 -- the info in PrelBase.hi. This is important, because the strictness
861 -- analyser will spot it as strict!
863 = pcMiscPrelId lazyIdName ty info
866 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy alphaTy)
868 lazyIdUnfolding :: CoreExpr -- Used to expand LazyOp after strictness anal
869 lazyIdUnfolding = mkLams [openAlphaTyVar,x] (Var x)
871 [x] = mkTemplateLocals [openAlphaTy]
874 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
875 nasty as-is, change it back to a literal (@Literal@).
877 voidArgId is a Local Id used simply as an argument in functions
878 where we just want an arg to avoid having a thunk of unlifted type.
880 x = \ void :: State# RealWorld -> (# p, q #)
882 This comes up in strictness analysis
885 realWorldPrimId -- :: State# RealWorld
886 = pcMiscPrelId realWorldName realWorldStatePrimTy
887 (noCafIdInfo `setUnfoldingInfo` mkOtherCon [])
888 -- The mkOtherCon makes it look that realWorld# is evaluated
889 -- which in turn makes Simplify.interestingArg return True,
890 -- which in turn makes INLINE things applied to realWorld# likely
893 voidArgId -- :: State# RealWorld
894 = mkSysLocal FSLIT("void") voidArgIdKey realWorldStatePrimTy
898 %************************************************************************
900 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
902 %************************************************************************
904 GHC randomly injects these into the code.
906 @patError@ is just a version of @error@ for pattern-matching
907 failures. It knows various ``codes'' which expand to longer
908 strings---this saves space!
910 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
911 well shouldn't be yanked on, but if one is, then you will get a
912 friendly message from @absentErr@ (rather than a totally random
915 @parError@ is a special version of @error@ which the compiler does
916 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
917 templates, but we don't ever expect to generate code for it.
921 :: Id -- Should be of type (forall a. Addr# -> a)
922 -- where Addr# points to a UTF8 encoded string
923 -> Type -- The type to instantiate 'a'
924 -> String -- The string to print
927 mkRuntimeErrorApp err_id res_ty err_msg
928 = mkApps (Var err_id) [Type res_ty, err_string]
930 err_string = Lit (MachStr (mkFastString (stringToUtf8 err_msg)))
932 rEC_SEL_ERROR_ID = mkRuntimeErrorId recSelErrorName
933 rUNTIME_ERROR_ID = mkRuntimeErrorId runtimeErrorName
934 iRREFUT_PAT_ERROR_ID = mkRuntimeErrorId irrefutPatErrorName
935 rEC_CON_ERROR_ID = mkRuntimeErrorId recConErrorName
936 nON_EXHAUSTIVE_GUARDS_ERROR_ID = mkRuntimeErrorId nonExhaustiveGuardsErrorName
937 pAT_ERROR_ID = mkRuntimeErrorId patErrorName
938 nO_METHOD_BINDING_ERROR_ID = mkRuntimeErrorId noMethodBindingErrorName
940 -- The runtime error Ids take a UTF8-encoded string as argument
941 mkRuntimeErrorId name = pc_bottoming_Id name runtimeErrorTy
942 runtimeErrorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTy addrPrimTy openAlphaTy)
946 eRROR_ID = pc_bottoming_Id errorName errorTy
949 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy] openAlphaTy)
950 -- Notice the openAlphaTyVar. It says that "error" can be applied
951 -- to unboxed as well as boxed types. This is OK because it never
952 -- returns, so the return type is irrelevant.
956 %************************************************************************
958 \subsection{Utilities}
960 %************************************************************************
963 pcMiscPrelId :: Name -> Type -> IdInfo -> Id
964 pcMiscPrelId name ty info
965 = mkVanillaGlobal name ty info
966 -- We lie and say the thing is imported; otherwise, we get into
967 -- a mess with dependency analysis; e.g., core2stg may heave in
968 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
969 -- being compiled, then it's just a matter of luck if the definition
970 -- will be in "the right place" to be in scope.
972 pc_bottoming_Id name ty
973 = pcMiscPrelId name ty bottoming_info
975 bottoming_info = hasCafIdInfo `setAllStrictnessInfo` Just strict_sig
976 -- Do *not* mark them as NoCafRefs, because they can indeed have
977 -- CAF refs. For example, pAT_ERROR_ID calls GHC.Err.untangle,
978 -- which has some CAFs
979 -- In due course we may arrange that these error-y things are
980 -- regarded by the GC as permanently live, in which case we
981 -- can give them NoCaf info. As it is, any function that calls
982 -- any pc_bottoming_Id will itself have CafRefs, which bloats
985 strict_sig = mkStrictSig (mkTopDmdType [evalDmd] BotRes)
986 -- These "bottom" out, no matter what their arguments
988 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
989 openAlphaTy = mkTyVarTy openAlphaTyVar
990 openBetaTy = mkTyVarTy openBetaTyVar