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, wrapNewTypeBody, unwrapNewTypeBody,
24 mkUnpackCase, mkProductBox,
26 -- And some particular Ids; see below for why they are wired in
27 wiredInIds, ghcPrimIds,
28 unsafeCoerceId, realWorldPrimId, voidArgId, nullAddrId, seqId,
29 lazyId, lazyIdUnfolding, lazyIdKey,
32 rEC_CON_ERROR_ID, iRREFUT_PAT_ERROR_ID, rUNTIME_ERROR_ID,
33 nON_EXHAUSTIVE_GUARDS_ERROR_ID, nO_METHOD_BINDING_ERROR_ID,
34 pAT_ERROR_ID, eRROR_ID,
39 #include "HsVersions.h"
42 import BasicTypes ( Arity, StrictnessMark(..), isMarkedUnboxed, isMarkedStrict )
43 import Rules ( mkSpecInfo )
44 import TysPrim ( openAlphaTyVars, alphaTyVar, alphaTy,
45 realWorldStatePrimTy, addrPrimTy
47 import TysWiredIn ( charTy, mkListTy )
48 import PrelRules ( primOpRules )
49 import Type ( TyThing(..), mkForAllTy, tyVarsOfTypes, newTyConInstRhs, coreEqType,
50 mkTopTvSubst, substTyVar )
51 import Coercion ( mkSymCoercion, mkUnsafeCoercion,
52 splitNewTypeRepCo_maybe, isEqPred )
53 import TcType ( Type, ThetaType, mkDictTy, mkPredTys, mkPredTy,
54 mkTyConApp, mkTyVarTys, mkClassPred,
55 mkFunTys, mkFunTy, mkSigmaTy, tcSplitSigmaTy,
56 isUnLiftedType, mkForAllTys, mkTyVarTy, tyVarsOfType,
57 tcSplitFunTys, tcSplitForAllTys, dataConsStupidTheta
59 import CoreUtils ( exprType )
60 import CoreUnfold ( mkTopUnfolding, mkCompulsoryUnfolding )
61 import Literal ( nullAddrLit, mkStringLit )
62 import TyCon ( TyCon, isNewTyCon, tyConDataCons, FieldLabel,
63 tyConStupidTheta, isProductTyCon, isDataTyCon, isRecursiveTyCon,
64 newTyConCo, tyConArity )
65 import Class ( Class, classTyCon, classSelIds )
66 import Var ( Id, TyVar, Var, setIdType, mkWildCoVar )
67 import VarSet ( isEmptyVarSet, subVarSet, varSetElems )
68 import Name ( mkFCallName, mkWiredInName, Name, BuiltInSyntax(..) )
69 import OccName ( mkOccNameFS, varName )
70 import PrimOp ( PrimOp, primOpSig, primOpOcc, primOpTag )
71 import ForeignCall ( ForeignCall )
72 import DataCon ( DataCon, DataConIds(..), dataConTyCon, dataConUnivTyVars,
73 dataConFieldLabels, dataConRepArity, dataConResTys,
74 dataConRepArgTys, dataConRepType, dataConFullSig,
75 dataConSig, dataConStrictMarks, dataConExStricts,
76 splitProductType, isVanillaDataCon, dataConFieldType,
77 dataConInstOrigArgTys, deepSplitProductType
79 import Id ( idType, mkGlobalId, mkVanillaGlobal, mkSysLocal,
80 mkTemplateLocals, mkTemplateLocalsNum, mkExportedLocalId,
81 mkTemplateLocal, idName, mkWildId
83 import IdInfo ( IdInfo, noCafIdInfo, setUnfoldingInfo,
84 setArityInfo, setSpecInfo, setCafInfo,
85 setAllStrictnessInfo, vanillaIdInfo,
86 GlobalIdDetails(..), CafInfo(..)
88 import NewDemand ( mkStrictSig, DmdResult(..),
89 mkTopDmdType, topDmd, evalDmd, lazyDmd, retCPR,
90 Demand(..), Demands(..) )
91 import DmdAnal ( dmdAnalTopRhs )
93 import Unique ( mkBuiltinUnique, mkPrimOpIdUnique )
96 import Util ( dropList, isSingleton )
99 import ListSetOps ( assoc, minusList )
102 %************************************************************************
104 \subsection{Wired in Ids}
106 %************************************************************************
110 = [ -- These error-y things are wired in because we don't yet have
111 -- a way to express in an interface file that the result type variable
112 -- is 'open'; that is can be unified with an unboxed type
114 -- [The interface file format now carry such information, but there's
115 -- no way yet of expressing at the definition site for these
116 -- error-reporting functions that they have an 'open'
117 -- result type. -- sof 1/99]
119 eRROR_ID, -- This one isn't used anywhere else in the compiler
120 -- But we still need it in wiredInIds so that when GHC
121 -- compiles a program that mentions 'error' we don't
122 -- import its type from the interface file; we just get
123 -- the Id defined here. Which has an 'open-tyvar' type.
126 iRREFUT_PAT_ERROR_ID,
127 nON_EXHAUSTIVE_GUARDS_ERROR_ID,
128 nO_METHOD_BINDING_ERROR_ID,
135 -- These Ids are exported from GHC.Prim
137 = [ -- These can't be defined in Haskell, but they have
138 -- perfectly reasonable unfoldings in Core
146 %************************************************************************
148 \subsection{Data constructors}
150 %************************************************************************
152 The wrapper for a constructor is an ordinary top-level binding that evaluates
153 any strict args, unboxes any args that are going to be flattened, and calls
156 We're going to build a constructor that looks like:
158 data (Data a, C b) => T a b = T1 !a !Int b
161 \d1::Data a, d2::C b ->
162 \p q r -> case p of { p ->
164 Con T1 [a,b] [p,q,r]}}
168 * d2 is thrown away --- a context in a data decl is used to make sure
169 one *could* construct dictionaries at the site the constructor
170 is used, but the dictionary isn't actually used.
172 * We have to check that we can construct Data dictionaries for
173 the types a and Int. Once we've done that we can throw d1 away too.
175 * We use (case p of q -> ...) to evaluate p, rather than "seq" because
176 all that matters is that the arguments are evaluated. "seq" is
177 very careful to preserve evaluation order, which we don't need
180 You might think that we could simply give constructors some strictness
181 info, like PrimOps, and let CoreToStg do the let-to-case transformation.
182 But we don't do that because in the case of primops and functions strictness
183 is a *property* not a *requirement*. In the case of constructors we need to
184 do something active to evaluate the argument.
186 Making an explicit case expression allows the simplifier to eliminate
187 it in the (common) case where the constructor arg is already evaluated.
191 mkDataConIds :: Name -> Name -> DataCon -> DataConIds
192 mkDataConIds wrap_name wkr_name data_con
196 | any isMarkedStrict all_strict_marks -- Algebraic, needs wrapper
197 || not (null eq_spec)
198 = AlgDC (Just alg_wrap_id) wrk_id
200 | otherwise -- Algebraic, no wrapper
201 = AlgDC Nothing wrk_id
203 (univ_tvs, ex_tvs, eq_spec, theta, orig_arg_tys) = dataConFullSig data_con
204 tycon = dataConTyCon data_con
206 ----------- Wrapper --------------
207 -- We used to include the stupid theta in the wrapper's args
208 -- but now we don't. Instead the type checker just injects these
209 -- extra constraints where necessary.
210 wrap_tvs = (univ_tvs `minusList` map fst eq_spec) ++ ex_tvs
211 subst = mkTopTvSubst eq_spec
212 dict_tys = mkPredTys theta
213 result_ty_args = map (substTyVar subst) univ_tvs
214 result_ty = mkTyConApp tycon result_ty_args
215 wrap_ty = mkForAllTys wrap_tvs $ mkFunTys dict_tys $
216 mkFunTys orig_arg_tys $ result_ty
217 -- NB: watch out here if you allow user-written equality
218 -- constraints in data constructor signatures
220 ----------- Worker (algebraic data types only) --------------
221 -- The *worker* for the data constructor is the function that
222 -- takes the representation arguments and builds the constructor.
223 wrk_id = mkGlobalId (DataConWorkId data_con) wkr_name
224 (dataConRepType data_con) wkr_info
226 wkr_arity = dataConRepArity data_con
227 wkr_info = noCafIdInfo
228 `setArityInfo` wkr_arity
229 `setAllStrictnessInfo` Just wkr_sig
230 `setUnfoldingInfo` evaldUnfolding -- Record that it's evaluated,
233 wkr_sig = mkStrictSig (mkTopDmdType (replicate wkr_arity topDmd) cpr_info)
234 -- Notice that we do *not* say the worker is strict
235 -- even if the data constructor is declared strict
236 -- e.g. data T = MkT !(Int,Int)
237 -- Why? Because the *wrapper* is strict (and its unfolding has case
238 -- expresssions that do the evals) but the *worker* itself is not.
239 -- If we pretend it is strict then when we see
240 -- case x of y -> $wMkT y
241 -- the simplifier thinks that y is "sure to be evaluated" (because
242 -- $wMkT is strict) and drops the case. No, $wMkT is not strict.
244 -- When the simplifer sees a pattern
245 -- case e of MkT x -> ...
246 -- it uses the dataConRepStrictness of MkT to mark x as evaluated;
247 -- but that's fine... dataConRepStrictness comes from the data con
248 -- not from the worker Id.
250 cpr_info | isProductTyCon tycon &&
253 wkr_arity <= mAX_CPR_SIZE = retCPR
255 -- RetCPR is only true for products that are real data types;
256 -- that is, not unboxed tuples or [non-recursive] newtypes
258 ----------- Wrappers for newtypes --------------
259 nt_wrap_id = mkGlobalId (DataConWrapId data_con) wrap_name wrap_ty nt_wrap_info
260 nt_wrap_info = noCafIdInfo -- The NoCaf-ness is set by noCafIdInfo
261 `setArityInfo` 1 -- Arity 1
262 `setUnfoldingInfo` newtype_unf
263 newtype_unf = ASSERT( isVanillaDataCon data_con &&
264 isSingleton orig_arg_tys )
265 -- No existentials on a newtype, but it can have a context
266 -- e.g. newtype Eq a => T a = MkT (...)
267 mkCompulsoryUnfolding $
268 mkLams wrap_tvs $ Lam id_arg1 $
269 wrapNewTypeBody tycon result_ty_args
272 id_arg1 = mkTemplateLocal 1 (head orig_arg_tys)
274 ----------- Wrappers for algebraic data types --------------
275 alg_wrap_id = mkGlobalId (DataConWrapId data_con) wrap_name wrap_ty alg_wrap_info
276 alg_wrap_info = noCafIdInfo -- The NoCaf-ness is set by noCafIdInfo
277 `setArityInfo` alg_arity
278 -- It's important to specify the arity, so that partial
279 -- applications are treated as values
280 `setUnfoldingInfo` alg_unf
281 `setAllStrictnessInfo` Just wrap_sig
283 all_strict_marks = dataConExStricts data_con ++ dataConStrictMarks data_con
284 wrap_sig = mkStrictSig (mkTopDmdType arg_dmds cpr_info)
285 arg_dmds = map mk_dmd all_strict_marks
286 mk_dmd str | isMarkedStrict str = evalDmd
287 | otherwise = lazyDmd
288 -- The Cpr info can be important inside INLINE rhss, where the
289 -- wrapper constructor isn't inlined.
290 -- And the argument strictness can be important too; we
291 -- may not inline a contructor when it is partially applied.
293 -- data W = C !Int !Int !Int
294 -- ...(let w = C x in ...(w p q)...)...
295 -- we want to see that w is strict in its two arguments
297 alg_unf = mkTopUnfolding $ Note InlineMe $
299 mkLams dict_args $ mkLams id_args $
300 foldr mk_case con_app
301 (zip (dict_args ++ id_args) all_strict_marks)
304 con_app i rep_ids = Var wrk_id `mkTyApps` result_ty_args
306 `mkTyApps` map snd eq_spec
307 `mkVarApps` reverse rep_ids
309 (dict_args,i2) = mkLocals 1 dict_tys
310 (id_args,i3) = mkLocals i2 orig_arg_tys
314 :: (Id, StrictnessMark) -- Arg, strictness
315 -> (Int -> [Id] -> CoreExpr) -- Body
316 -> Int -- Next rep arg id
317 -> [Id] -- Rep args so far, reversed
319 mk_case (arg,strict) body i rep_args
321 NotMarkedStrict -> body i (arg:rep_args)
323 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
325 Case (Var arg) arg result_ty [(DEFAULT,[], body i (arg:rep_args))]
328 -> unboxProduct i (Var arg) (idType arg) the_body result_ty
330 the_body i con_args = body i (reverse con_args ++ rep_args)
332 mAX_CPR_SIZE :: Arity
334 -- We do not treat very big tuples as CPR-ish:
335 -- a) for a start we get into trouble because there aren't
336 -- "enough" unboxed tuple types (a tiresome restriction,
338 -- b) more importantly, big unboxed tuples get returned mainly
339 -- on the stack, and are often then allocated in the heap
340 -- by the caller. So doing CPR for them may in fact make
343 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
349 %************************************************************************
351 \subsection{Record selectors}
353 %************************************************************************
355 We're going to build a record selector unfolding that looks like this:
357 data T a b c = T1 { ..., op :: a, ...}
358 | T2 { ..., op :: a, ...}
361 sel = /\ a b c -> \ d -> case d of
366 Similarly for newtypes
368 newtype N a = MkN { unN :: a->a }
371 unN n = coerce (a->a) n
373 We need to take a little care if the field has a polymorphic type:
375 data R = R { f :: forall a. a->a }
379 f :: forall a. R -> a -> a
380 f = /\ a \ r = case r of
383 (not f :: R -> forall a. a->a, which gives the type inference mechanism
384 problems at call sites)
386 Similarly for (recursive) newtypes
388 newtype N = MkN { unN :: forall a. a->a }
390 unN :: forall b. N -> b -> b
391 unN = /\b -> \n:N -> (coerce (forall a. a->a) n)
394 Note [Naughty record selectors]
395 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
396 A "naughty" field is one for which we can't define a record
397 selector, because an existential type variable would escape. For example:
398 data T = forall a. MkT { x,y::a }
399 We obviously can't define
401 Nevertheless we *do* put a RecordSelId into the type environment
402 so that if the user tries to use 'x' as a selector we can bleat
403 helpfully, rather than saying unhelpfully that 'x' is not in scope.
404 Hence the sel_naughty flag, to identify record selectors that don't really exist.
406 In general, a field is naughty if its type mentions a type variable that
407 isn't in the result type of the constructor.
409 Note [GADT record selectors]
410 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
411 For GADTs, we require that all constructors with a common field 'f' have the same
412 result type (modulo alpha conversion). [Checked in TcTyClsDecls.checkValidTyCon]
415 T1 { f :: a } :: T [a]
416 T2 { f :: a, y :: b } :: T [a]
417 and now the selector takes that type as its argument:
418 f :: forall a. T [a] -> a
422 Note the forall'd tyvars of the selector are just the free tyvars
423 of the result type; there may be other tyvars in the constructor's
424 type (e.g. 'b' in T2).
428 -- Steps for handling "naughty" vs "non-naughty" selectors:
429 -- 1. Determine naughtiness by comparing field type vs result type
430 -- 2. Install naughty ones with selector_ty of type _|_ and fill in mzero for info
431 -- 3. If it's not naughty, do the normal plan.
433 mkRecordSelId :: TyCon -> FieldLabel -> Id
434 mkRecordSelId tycon field_label
435 -- Assumes that all fields with the same field label have the same type
436 | is_naughty = naughty_id
439 is_naughty = not (tyVarsOfType field_ty `subVarSet` res_tv_set)
440 sel_id_details = RecordSelId tycon field_label is_naughty
442 -- Escapist case here for naughty construcotrs
443 -- We give it no IdInfo, and a type of forall a.a (never looked at)
444 naughty_id = mkGlobalId sel_id_details field_label forall_a_a noCafIdInfo
445 forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar)
447 -- Normal case starts here
448 sel_id = mkGlobalId sel_id_details field_label selector_ty info
449 data_cons = tyConDataCons tycon
450 data_cons_w_field = filter has_field data_cons -- Can't be empty!
451 has_field con = field_label `elem` dataConFieldLabels con
453 con1 = head data_cons_w_field
454 res_tys = dataConResTys con1
455 res_tv_set = tyVarsOfTypes res_tys
456 res_tvs = varSetElems res_tv_set
457 data_ty = mkTyConApp tycon res_tys
458 field_ty = dataConFieldType con1 field_label
460 -- *Very* tiresomely, the selectors are (unnecessarily!) overloaded over
461 -- just the dictionaries in the types of the constructors that contain
462 -- the relevant field. [The Report says that pattern matching on a
463 -- constructor gives the same constraints as applying it.] Urgh.
465 -- However, not all data cons have all constraints (because of
466 -- BuildTyCl.mkDataConStupidTheta). So we need to find all the data cons
467 -- involved in the pattern match and take the union of their constraints.
468 stupid_dict_tys = mkPredTys (dataConsStupidTheta data_cons_w_field)
469 n_stupid_dicts = length stupid_dict_tys
471 (pre_field_tyvars,pre_field_theta,field_tau) = tcSplitSigmaTy field_ty
472 -- tcSplitSigmaTy puts tyvars with EqPred kinds in with the theta, but
473 -- this is not what we want here, so we need to split out the EqPreds
474 -- as new wild tyvars
475 field_tyvars = pre_field_tyvars ++ eq_vars
476 eq_vars = map (mkWildCoVar . mkPredTy)
477 (filter isEqPred pre_field_theta)
478 field_theta = filter (not . isEqPred) pre_field_theta
479 field_dict_tys = mkPredTys field_theta
480 n_field_dict_tys = length field_dict_tys
481 -- If the field has a universally quantified type we have to
482 -- be a bit careful. Suppose we have
483 -- data R = R { op :: forall a. Foo a => a -> a }
484 -- Then we can't give op the type
485 -- op :: R -> forall a. Foo a => a -> a
486 -- because the typechecker doesn't understand foralls to the
487 -- right of an arrow. The "right" type to give it is
488 -- op :: forall a. Foo a => R -> a -> a
489 -- But then we must generate the right unfolding too:
490 -- op = /\a -> \dfoo -> \ r ->
493 -- Note that this is exactly the type we'd infer from a user defn
497 selector_ty = mkForAllTys res_tvs $ mkForAllTys field_tyvars $
498 mkFunTys stupid_dict_tys $ mkFunTys field_dict_tys $
499 mkFunTy data_ty field_tau
501 arity = 1 + n_stupid_dicts + n_field_dict_tys
503 (strict_sig, rhs_w_str) = dmdAnalTopRhs sel_rhs
504 -- Use the demand analyser to work out strictness.
505 -- With all this unpackery it's not easy!
508 `setCafInfo` caf_info
510 `setUnfoldingInfo` mkTopUnfolding rhs_w_str
511 `setAllStrictnessInfo` Just strict_sig
513 -- Allocate Ids. We do it a funny way round because field_dict_tys is
514 -- almost always empty. Also note that we use max_dict_tys
515 -- rather than n_dict_tys, because the latter gives an infinite loop:
516 -- n_dict tys depends on the_alts, which depens on arg_ids, which depends
517 -- on arity, which depends on n_dict tys. Sigh! Mega sigh!
518 stupid_dict_ids = mkTemplateLocalsNum 1 stupid_dict_tys
519 max_stupid_dicts = length (tyConStupidTheta tycon)
520 field_dict_base = max_stupid_dicts + 1
521 field_dict_ids = mkTemplateLocalsNum field_dict_base field_dict_tys
522 dict_id_base = field_dict_base + n_field_dict_tys
523 data_id = mkTemplateLocal dict_id_base data_ty
524 arg_base = dict_id_base + 1
526 the_alts :: [CoreAlt]
527 the_alts = map mk_alt data_cons_w_field -- Already sorted by data-con
528 no_default = length data_cons == length data_cons_w_field -- No default needed
530 default_alt | no_default = []
531 | otherwise = [(DEFAULT, [], error_expr)]
533 -- The default branch may have CAF refs, because it calls recSelError etc.
534 caf_info | no_default = NoCafRefs
535 | otherwise = MayHaveCafRefs
537 sel_rhs = mkLams res_tvs $ mkLams field_tyvars $
538 mkLams stupid_dict_ids $ mkLams field_dict_ids $
539 Lam data_id $ mk_result sel_body
541 -- NB: A newtype always has a vanilla DataCon; no existentials etc
542 -- res_tys will simply be the dataConUnivTyVars
543 sel_body | isNewTyCon tycon = unwrapNewTypeBody tycon res_tys (Var data_id)
544 | otherwise = Case (Var data_id) data_id field_ty (default_alt ++ the_alts)
546 mk_result poly_result = mkVarApps (mkVarApps poly_result field_tyvars) field_dict_ids
547 -- We pull the field lambdas to the top, so we need to
548 -- apply them in the body. For example:
549 -- data T = MkT { foo :: forall a. a->a }
551 -- foo :: forall a. T -> a -> a
552 -- foo = /\a. \t:T. case t of { MkT f -> f a }
555 = -- In the non-vanilla case, the pattern must bind type variables and
556 -- the context stuff; hence the arg_prefix binding below
557 pprTrace "mkReboxingAlt" (ppr data_con <+> ppr (arg_prefix ++ arg_ids)) $ mkReboxingAlt uniqs data_con (arg_prefix ++ arg_ids) (Var the_arg_id)
559 (arg_prefix, arg_ids)
560 | isVanillaDataCon data_con -- Instantiate from commmon base
561 = ([], mkTemplateLocalsNum arg_base (dataConInstOrigArgTys data_con res_tys))
562 | otherwise -- The case pattern binds type variables, which are used
563 -- in the types of the arguments of the pattern
564 = (dc_tvs ++ mkTemplateLocalsNum arg_base (mkPredTys dc_theta),
565 mkTemplateLocalsNum arg_base' dc_arg_tys)
567 (pre_dc_tvs, pre_dc_theta, dc_arg_tys) = dataConSig data_con
568 -- again we need to pull the EqPreds out of dc_theta, into dc_tvs
569 dc_eqvars = map (mkWildCoVar . mkPredTy) (filter isEqPred pre_dc_theta)
570 dc_tvs = drop (length (dataConUnivTyVars data_con)) pre_dc_tvs ++ dc_eqvars
571 dc_theta = filter (not . isEqPred) pre_dc_theta
572 arg_base' = arg_base + length dc_theta
574 unpack_base = arg_base' + length dc_arg_tys
575 uniqs = map mkBuiltinUnique [unpack_base..]
577 the_arg_id = assoc "mkRecordSelId:mk_alt" (field_lbls `zip` arg_ids) field_label
578 field_lbls = dataConFieldLabels data_con
580 error_expr = mkRuntimeErrorApp rEC_SEL_ERROR_ID field_tau full_msg
581 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
583 -- unbox a product type...
584 -- we will recurse into newtypes, casting along the way, and unbox at the
585 -- first product data constructor we find. e.g.
587 -- data PairInt = PairInt Int Int
588 -- newtype S = MkS PairInt
591 -- If we have e = MkT (MkS (PairInt 0 1)) and some body expecting a list of
592 -- ids, we get (modulo int passing)
594 -- case (e `cast` (sym CoT)) `cast` (sym CoS) of
595 -- PairInt a b -> body [a,b]
597 -- The Ints passed around are just for creating fresh locals
598 unboxProduct :: Int -> CoreExpr -> Type -> (Int -> [Id] -> CoreExpr) -> Type -> CoreExpr
599 unboxProduct i arg arg_ty body res_ty
602 result = mkUnpackCase the_id arg arg_ty con_args boxing_con rhs
603 (tycon, tycon_args, boxing_con, tys) = deepSplitProductType "unboxProduct" arg_ty
604 ([the_id], i') = mkLocals i [arg_ty]
605 (con_args, i'') = mkLocals i' tys
606 rhs = body i'' con_args
608 mkUnpackCase :: Id -> CoreExpr -> Type -> [Id] -> DataCon -> CoreExpr -> CoreExpr
609 -- (mkUnpackCase x e args Con body)
611 -- case (e `cast` ...) of bndr { Con args -> body }
613 -- the type of the bndr passed in is irrelevent
614 mkUnpackCase bndr arg arg_ty unpk_args boxing_con body
615 = Case cast_arg (setIdType bndr bndr_ty) (exprType body) [(DataAlt boxing_con, unpk_args, body)]
617 (cast_arg, bndr_ty) = go (idType bndr) arg
619 | res@(tycon, tycon_args, _, _) <- splitProductType "mkUnpackCase" ty
620 , isNewTyCon tycon && not (isRecursiveTyCon tycon)
621 = go (newTyConInstRhs tycon tycon_args)
622 (unwrapNewTypeBody tycon tycon_args arg)
623 | otherwise = (arg, ty)
626 reboxProduct :: [Unique] -- uniques to create new local binders
627 -> Type -- type of product to box
628 -> ([Unique], -- remaining uniques
629 CoreExpr, -- boxed product
630 [Id]) -- Ids being boxed into product
633 (tycon, tycon_args, pack_con, con_arg_tys) = deepSplitProductType "reboxProduct" ty
635 us' = dropList con_arg_tys us
637 arg_ids = zipWith (mkSysLocal FSLIT("rb")) us con_arg_tys
639 bind_rhs = mkProductBox arg_ids ty
642 (us', bind_rhs, arg_ids)
644 mkProductBox :: [Id] -> Type -> CoreExpr
645 mkProductBox arg_ids ty
648 (tycon, tycon_args, pack_con, con_arg_tys) = splitProductType "mkProductBox" ty
651 | isNewTyCon tycon && not (isRecursiveTyCon tycon)
652 = wrap (mkProductBox arg_ids (newTyConInstRhs tycon tycon_args))
653 | otherwise = mkConApp pack_con (map Type tycon_args ++ map Var arg_ids)
655 wrap expr = wrapNewTypeBody tycon tycon_args expr
658 -- (mkReboxingAlt us con xs rhs) basically constructs the case
659 -- alternative (con, xs, rhs)
660 -- but it does the reboxing necessary to construct the *source*
661 -- arguments, xs, from the representation arguments ys.
663 -- data T = MkT !(Int,Int) Bool
665 -- mkReboxingAlt MkT [x,b] r
666 -- = (DataAlt MkT, [y::Int,z::Int,b], let x = (y,z) in r)
668 -- mkDataAlt should really be in DataCon, but it can't because
669 -- it manipulates CoreSyn.
672 :: [Unique] -- Uniques for the new Ids
674 -> [Var] -- Source-level args, including existential dicts
678 mkReboxingAlt us con args rhs
679 | not (any isMarkedUnboxed stricts)
680 = (DataAlt con, args, rhs)
684 (binds, args') = go args stricts us
686 (DataAlt con, args', mkLets binds rhs)
689 stricts = dataConExStricts con ++ dataConStrictMarks con
691 go [] stricts us = ([], [])
693 -- Type variable case
694 go (arg:args) stricts us
696 = let (binds, args') = go args stricts us
697 in (binds, arg:args')
699 -- Term variable case
700 go (arg:args) (str:stricts) us
701 | isMarkedUnboxed str
703 let (binds, unpacked_args') = go args stricts us'
704 (us', bind_rhs, unpacked_args) = reboxProduct us (idType arg)
706 (NonRec arg bind_rhs : binds, unpacked_args ++ unpacked_args')
708 = let (binds, args') = go args stricts us
709 in (binds, arg:args')
713 %************************************************************************
715 \subsection{Dictionary selectors}
717 %************************************************************************
719 Selecting a field for a dictionary. If there is just one field, then
720 there's nothing to do.
722 Dictionary selectors may get nested forall-types. Thus:
725 op :: forall b. Ord b => a -> b -> b
727 Then the top-level type for op is
729 op :: forall a. Foo a =>
733 This is unlike ordinary record selectors, which have all the for-alls
734 at the outside. When dealing with classes it's very convenient to
735 recover the original type signature from the class op selector.
738 mkDictSelId :: Name -> Class -> Id
739 mkDictSelId name clas
740 = mkGlobalId (ClassOpId clas) name sel_ty info
742 sel_ty = mkForAllTys tyvars (mkFunTy (idType dict_id) (idType the_arg_id))
743 -- We can't just say (exprType rhs), because that would give a type
745 -- for a single-op class (after all, the selector is the identity)
746 -- But it's type must expose the representation of the dictionary
747 -- to gat (say) C a -> (a -> a)
751 `setUnfoldingInfo` mkTopUnfolding rhs
752 `setAllStrictnessInfo` Just strict_sig
754 -- We no longer use 'must-inline' on record selectors. They'll
755 -- inline like crazy if they scrutinise a constructor
757 -- The strictness signature is of the form U(AAAVAAAA) -> T
758 -- where the V depends on which item we are selecting
759 -- It's worth giving one, so that absence info etc is generated
760 -- even if the selector isn't inlined
761 strict_sig = mkStrictSig (mkTopDmdType [arg_dmd] TopRes)
762 arg_dmd | isNewTyCon tycon = evalDmd
763 | otherwise = Eval (Prod [ if the_arg_id == id then evalDmd else Abs
766 tycon = classTyCon clas
767 [data_con] = tyConDataCons tycon
768 tyvars = dataConUnivTyVars data_con
769 arg_tys = ASSERT( isVanillaDataCon data_con ) dataConRepArgTys data_con
770 the_arg_id = assoc "MkId.mkDictSelId" (map idName (classSelIds clas) `zip` arg_ids) name
772 pred = mkClassPred clas (mkTyVarTys tyvars)
773 (dict_id:arg_ids) = mkTemplateLocals (mkPredTy pred : arg_tys)
775 rhs = mkLams tyvars (Lam dict_id rhs_body)
776 rhs_body | isNewTyCon tycon = unwrapNewTypeBody tycon (map mkTyVarTy tyvars) (Var dict_id)
777 | otherwise = Case (Var dict_id) dict_id (idType the_arg_id)
778 [(DataAlt data_con, arg_ids, Var the_arg_id)]
780 wrapNewTypeBody :: TyCon -> [Type] -> CoreExpr -> CoreExpr
781 -- The wrapper for the data constructor for a newtype looks like this:
782 -- newtype T a = MkT (a,Int)
783 -- MkT :: forall a. (a,Int) -> T a
784 -- MkT = /\a. \(x:(a,Int)). x `cast` CoT a
785 -- where CoT is the coercion TyCon assoicated with the newtype
787 -- The call (wrapNewTypeBody T [a] e) returns the
788 -- body of the wrapper, namely
791 -- If a coercion constructor is prodivided in the newtype, then we use
792 -- it, otherwise the wrap/unwrap are both no-ops
794 wrapNewTypeBody tycon args result_expr
795 | Just co_con <- newTyConCo tycon
796 = Cast result_expr (mkTyConApp co_con args)
800 unwrapNewTypeBody :: TyCon -> [Type] -> CoreExpr -> CoreExpr
801 unwrapNewTypeBody tycon args result_expr
802 | Just co_con <- newTyConCo tycon
803 = Cast result_expr (mkSymCoercion (mkTyConApp co_con args))
811 %************************************************************************
813 \subsection{Primitive operations
815 %************************************************************************
818 mkPrimOpId :: PrimOp -> Id
822 (tyvars,arg_tys,res_ty, arity, strict_sig) = primOpSig prim_op
823 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
824 name = mkWiredInName gHC_PRIM (primOpOcc prim_op)
825 (mkPrimOpIdUnique (primOpTag prim_op))
826 Nothing (AnId id) UserSyntax
827 id = mkGlobalId (PrimOpId prim_op) name ty info
830 `setSpecInfo` mkSpecInfo (primOpRules prim_op name)
832 `setAllStrictnessInfo` Just strict_sig
834 -- For each ccall we manufacture a separate CCallOpId, giving it
835 -- a fresh unique, a type that is correct for this particular ccall,
836 -- and a CCall structure that gives the correct details about calling
839 -- The *name* of this Id is a local name whose OccName gives the full
840 -- details of the ccall, type and all. This means that the interface
841 -- file reader can reconstruct a suitable Id
843 mkFCallId :: Unique -> ForeignCall -> Type -> Id
844 mkFCallId uniq fcall ty
845 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
846 -- A CCallOpId should have no free type variables;
847 -- when doing substitutions won't substitute over it
848 mkGlobalId (FCallId fcall) name ty info
850 occ_str = showSDoc (braces (ppr fcall <+> ppr ty))
851 -- The "occurrence name" of a ccall is the full info about the
852 -- ccall; it is encoded, but may have embedded spaces etc!
854 name = mkFCallName uniq occ_str
858 `setAllStrictnessInfo` Just strict_sig
860 (_, tau) = tcSplitForAllTys ty
861 (arg_tys, _) = tcSplitFunTys tau
862 arity = length arg_tys
863 strict_sig = mkStrictSig (mkTopDmdType (replicate arity evalDmd) TopRes)
867 %************************************************************************
869 \subsection{DictFuns and default methods}
871 %************************************************************************
873 Important notes about dict funs and default methods
874 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
875 Dict funs and default methods are *not* ImplicitIds. Their definition
876 involves user-written code, so we can't figure out their strictness etc
877 based on fixed info, as we can for constructors and record selectors (say).
879 We build them as LocalIds, but with External Names. This ensures that
880 they are taken to account by free-variable finding and dependency
881 analysis (e.g. CoreFVs.exprFreeVars).
883 Why shouldn't they be bound as GlobalIds? Because, in particular, if
884 they are globals, the specialiser floats dict uses above their defns,
885 which prevents good simplifications happening. Also the strictness
886 analyser treats a occurrence of a GlobalId as imported and assumes it
887 contains strictness in its IdInfo, which isn't true if the thing is
888 bound in the same module as the occurrence.
890 It's OK for dfuns to be LocalIds, because we form the instance-env to
891 pass on to the next module (md_insts) in CoreTidy, afer tidying
892 and globalising the top-level Ids.
894 BUT make sure they are *exported* LocalIds (mkExportedLocalId) so
895 that they aren't discarded by the occurrence analyser.
898 mkDefaultMethodId dm_name ty = mkExportedLocalId dm_name ty
900 mkDictFunId :: Name -- Name to use for the dict fun;
907 mkDictFunId dfun_name inst_tyvars dfun_theta clas inst_tys
908 = mkExportedLocalId dfun_name dfun_ty
910 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
912 {- 1 dec 99: disable the Mark Jones optimisation for the sake
913 of compatibility with Hugs.
914 See `types/InstEnv' for a discussion related to this.
916 (class_tyvars, sc_theta, _, _) = classBigSig clas
917 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
918 sc_theta' = substClasses (zipTopTvSubst class_tyvars inst_tys) sc_theta
919 dfun_theta = case inst_decl_theta of
920 [] -> [] -- If inst_decl_theta is empty, then we don't
921 -- want to have any dict arguments, so that we can
922 -- expose the constant methods.
924 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
925 -- Otherwise we pass the superclass dictionaries to
926 -- the dictionary function; the Mark Jones optimisation.
928 -- NOTE the "nub". I got caught by this one:
929 -- class Monad m => MonadT t m where ...
930 -- instance Monad m => MonadT (EnvT env) m where ...
931 -- Here, the inst_decl_theta has (Monad m); but so
932 -- does the sc_theta'!
934 -- NOTE the "not_const". I got caught by this one too:
935 -- class Foo a => Baz a b where ...
936 -- instance Wob b => Baz T b where..
937 -- Now sc_theta' has Foo T
942 %************************************************************************
944 \subsection{Un-definable}
946 %************************************************************************
948 These Ids can't be defined in Haskell. They could be defined in
949 unfoldings in the wired-in GHC.Prim interface file, but we'd have to
950 ensure that they were definitely, definitely inlined, because there is
951 no curried identifier for them. That's what mkCompulsoryUnfolding
952 does. If we had a way to get a compulsory unfolding from an interface
953 file, we could do that, but we don't right now.
955 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
956 just gets expanded into a type coercion wherever it occurs. Hence we
957 add it as a built-in Id with an unfolding here.
959 The type variables we use here are "open" type variables: this means
960 they can unify with both unlifted and lifted types. Hence we provide
961 another gun with which to shoot yourself in the foot.
964 mkWiredInIdName mod fs uniq id
965 = mkWiredInName mod (mkOccNameFS varName fs) uniq Nothing (AnId id) UserSyntax
967 unsafeCoerceName = mkWiredInIdName gHC_PRIM FSLIT("unsafeCoerce#") unsafeCoerceIdKey unsafeCoerceId
968 nullAddrName = mkWiredInIdName gHC_PRIM FSLIT("nullAddr#") nullAddrIdKey nullAddrId
969 seqName = mkWiredInIdName gHC_PRIM FSLIT("seq") seqIdKey seqId
970 realWorldName = mkWiredInIdName gHC_PRIM FSLIT("realWorld#") realWorldPrimIdKey realWorldPrimId
971 lazyIdName = mkWiredInIdName gHC_BASE FSLIT("lazy") lazyIdKey lazyId
973 errorName = mkWiredInIdName gHC_ERR FSLIT("error") errorIdKey eRROR_ID
974 recSelErrorName = mkWiredInIdName gHC_ERR FSLIT("recSelError") recSelErrorIdKey rEC_SEL_ERROR_ID
975 runtimeErrorName = mkWiredInIdName gHC_ERR FSLIT("runtimeError") runtimeErrorIdKey rUNTIME_ERROR_ID
976 irrefutPatErrorName = mkWiredInIdName gHC_ERR FSLIT("irrefutPatError") irrefutPatErrorIdKey iRREFUT_PAT_ERROR_ID
977 recConErrorName = mkWiredInIdName gHC_ERR FSLIT("recConError") recConErrorIdKey rEC_CON_ERROR_ID
978 patErrorName = mkWiredInIdName gHC_ERR FSLIT("patError") patErrorIdKey pAT_ERROR_ID
979 noMethodBindingErrorName = mkWiredInIdName gHC_ERR FSLIT("noMethodBindingError")
980 noMethodBindingErrorIdKey nO_METHOD_BINDING_ERROR_ID
981 nonExhaustiveGuardsErrorName
982 = mkWiredInIdName gHC_ERR FSLIT("nonExhaustiveGuardsError")
983 nonExhaustiveGuardsErrorIdKey nON_EXHAUSTIVE_GUARDS_ERROR_ID
987 -- unsafeCoerce# :: forall a b. a -> b
989 = pcMiscPrelId unsafeCoerceName ty info
991 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
994 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
995 (mkFunTy openAlphaTy openBetaTy)
996 [x] = mkTemplateLocals [openAlphaTy]
997 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
998 -- Note (Coerce openBetaTy openAlphaTy) (Var x)
999 Cast (Var x) (mkUnsafeCoercion openAlphaTy openBetaTy)
1001 -- nullAddr# :: Addr#
1002 -- The reason is is here is because we don't provide
1003 -- a way to write this literal in Haskell.
1005 = pcMiscPrelId nullAddrName addrPrimTy info
1007 info = noCafIdInfo `setUnfoldingInfo`
1008 mkCompulsoryUnfolding (Lit nullAddrLit)
1011 = pcMiscPrelId seqName ty info
1013 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
1016 ty = mkForAllTys [alphaTyVar,openBetaTyVar]
1017 (mkFunTy alphaTy (mkFunTy openBetaTy openBetaTy))
1018 [x,y] = mkTemplateLocals [alphaTy, openBetaTy]
1019 rhs = mkLams [alphaTyVar,openBetaTyVar,x,y] (Case (Var x) x openBetaTy [(DEFAULT, [], Var y)])
1021 -- lazy :: forall a?. a? -> a? (i.e. works for unboxed types too)
1022 -- Used to lazify pseq: pseq a b = a `seq` lazy b
1024 -- Also, no strictness: by being a built-in Id, all the info about lazyId comes from here,
1025 -- not from GHC.Base.hi. This is important, because the strictness
1026 -- analyser will spot it as strict!
1028 -- Also no unfolding in lazyId: it gets "inlined" by a HACK in the worker/wrapper pass
1029 -- (see WorkWrap.wwExpr)
1030 -- We could use inline phases to do this, but that would be vulnerable to changes in
1031 -- phase numbering....we must inline precisely after strictness analysis.
1033 = pcMiscPrelId lazyIdName ty info
1036 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy alphaTy)
1038 lazyIdUnfolding :: CoreExpr -- Used to expand 'lazyId' after strictness anal
1039 lazyIdUnfolding = mkLams [openAlphaTyVar,x] (Var x)
1041 [x] = mkTemplateLocals [openAlphaTy]
1044 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
1045 nasty as-is, change it back to a literal (@Literal@).
1047 voidArgId is a Local Id used simply as an argument in functions
1048 where we just want an arg to avoid having a thunk of unlifted type.
1050 x = \ void :: State# RealWorld -> (# p, q #)
1052 This comes up in strictness analysis
1055 realWorldPrimId -- :: State# RealWorld
1056 = pcMiscPrelId realWorldName realWorldStatePrimTy
1057 (noCafIdInfo `setUnfoldingInfo` evaldUnfolding)
1058 -- The evaldUnfolding makes it look that realWorld# is evaluated
1059 -- which in turn makes Simplify.interestingArg return True,
1060 -- which in turn makes INLINE things applied to realWorld# likely
1063 voidArgId -- :: State# RealWorld
1064 = mkSysLocal FSLIT("void") voidArgIdKey realWorldStatePrimTy
1068 %************************************************************************
1070 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
1072 %************************************************************************
1074 GHC randomly injects these into the code.
1076 @patError@ is just a version of @error@ for pattern-matching
1077 failures. It knows various ``codes'' which expand to longer
1078 strings---this saves space!
1080 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
1081 well shouldn't be yanked on, but if one is, then you will get a
1082 friendly message from @absentErr@ (rather than a totally random
1085 @parError@ is a special version of @error@ which the compiler does
1086 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
1087 templates, but we don't ever expect to generate code for it.
1091 :: Id -- Should be of type (forall a. Addr# -> a)
1092 -- where Addr# points to a UTF8 encoded string
1093 -> Type -- The type to instantiate 'a'
1094 -> String -- The string to print
1097 mkRuntimeErrorApp err_id res_ty err_msg
1098 = mkApps (Var err_id) [Type res_ty, err_string]
1100 err_string = Lit (mkStringLit err_msg)
1102 rEC_SEL_ERROR_ID = mkRuntimeErrorId recSelErrorName
1103 rUNTIME_ERROR_ID = mkRuntimeErrorId runtimeErrorName
1104 iRREFUT_PAT_ERROR_ID = mkRuntimeErrorId irrefutPatErrorName
1105 rEC_CON_ERROR_ID = mkRuntimeErrorId recConErrorName
1106 pAT_ERROR_ID = mkRuntimeErrorId patErrorName
1107 nO_METHOD_BINDING_ERROR_ID = mkRuntimeErrorId noMethodBindingErrorName
1108 nON_EXHAUSTIVE_GUARDS_ERROR_ID = mkRuntimeErrorId nonExhaustiveGuardsErrorName
1110 -- The runtime error Ids take a UTF8-encoded string as argument
1111 mkRuntimeErrorId name = pc_bottoming_Id name runtimeErrorTy
1112 runtimeErrorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTy addrPrimTy openAlphaTy)
1116 eRROR_ID = pc_bottoming_Id errorName errorTy
1119 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy] openAlphaTy)
1120 -- Notice the openAlphaTyVar. It says that "error" can be applied
1121 -- to unboxed as well as boxed types. This is OK because it never
1122 -- returns, so the return type is irrelevant.
1126 %************************************************************************
1128 \subsection{Utilities}
1130 %************************************************************************
1133 pcMiscPrelId :: Name -> Type -> IdInfo -> Id
1134 pcMiscPrelId name ty info
1135 = mkVanillaGlobal name ty info
1136 -- We lie and say the thing is imported; otherwise, we get into
1137 -- a mess with dependency analysis; e.g., core2stg may heave in
1138 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
1139 -- being compiled, then it's just a matter of luck if the definition
1140 -- will be in "the right place" to be in scope.
1142 pc_bottoming_Id name ty
1143 = pcMiscPrelId name ty bottoming_info
1145 bottoming_info = vanillaIdInfo `setAllStrictnessInfo` Just strict_sig
1146 -- Do *not* mark them as NoCafRefs, because they can indeed have
1147 -- CAF refs. For example, pAT_ERROR_ID calls GHC.Err.untangle,
1148 -- which has some CAFs
1149 -- In due course we may arrange that these error-y things are
1150 -- regarded by the GC as permanently live, in which case we
1151 -- can give them NoCaf info. As it is, any function that calls
1152 -- any pc_bottoming_Id will itself have CafRefs, which bloats
1155 strict_sig = mkStrictSig (mkTopDmdType [evalDmd] BotRes)
1156 -- These "bottom" out, no matter what their arguments
1158 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
1159 openAlphaTy = mkTyVarTy openAlphaTyVar
1160 openBetaTy = mkTyVarTy openBetaTyVar