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 )
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 )
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 (field_tyvars,field_theta,field_tau) = tcSplitSigmaTy field_ty
472 field_dict_tys = mkPredTys field_theta
473 n_field_dict_tys = length field_dict_tys
474 -- If the field has a universally quantified type we have to
475 -- be a bit careful. Suppose we have
476 -- data R = R { op :: forall a. Foo a => a -> a }
477 -- Then we can't give op the type
478 -- op :: R -> forall a. Foo a => a -> a
479 -- because the typechecker doesn't understand foralls to the
480 -- right of an arrow. The "right" type to give it is
481 -- op :: forall a. Foo a => R -> a -> a
482 -- But then we must generate the right unfolding too:
483 -- op = /\a -> \dfoo -> \ r ->
486 -- Note that this is exactly the type we'd infer from a user defn
490 selector_ty = mkForAllTys res_tvs $ mkForAllTys field_tyvars $
491 mkFunTys stupid_dict_tys $ mkFunTys field_dict_tys $
492 mkFunTy data_ty field_tau
494 arity = 1 + n_stupid_dicts + n_field_dict_tys
496 (strict_sig, rhs_w_str) = dmdAnalTopRhs sel_rhs
497 -- Use the demand analyser to work out strictness.
498 -- With all this unpackery it's not easy!
501 `setCafInfo` caf_info
503 `setUnfoldingInfo` mkTopUnfolding rhs_w_str
504 `setAllStrictnessInfo` Just strict_sig
506 -- Allocate Ids. We do it a funny way round because field_dict_tys is
507 -- almost always empty. Also note that we use max_dict_tys
508 -- rather than n_dict_tys, because the latter gives an infinite loop:
509 -- n_dict tys depends on the_alts, which depens on arg_ids, which depends
510 -- on arity, which depends on n_dict tys. Sigh! Mega sigh!
511 stupid_dict_ids = mkTemplateLocalsNum 1 stupid_dict_tys
512 max_stupid_dicts = length (tyConStupidTheta tycon)
513 field_dict_base = max_stupid_dicts + 1
514 field_dict_ids = mkTemplateLocalsNum field_dict_base field_dict_tys
515 dict_id_base = field_dict_base + n_field_dict_tys
516 data_id = mkTemplateLocal dict_id_base data_ty
517 arg_base = dict_id_base + 1
519 the_alts :: [CoreAlt]
520 the_alts = map mk_alt data_cons_w_field -- Already sorted by data-con
521 no_default = length data_cons == length data_cons_w_field -- No default needed
523 default_alt | no_default = []
524 | otherwise = [(DEFAULT, [], error_expr)]
526 -- The default branch may have CAF refs, because it calls recSelError etc.
527 caf_info | no_default = NoCafRefs
528 | otherwise = MayHaveCafRefs
530 sel_rhs = mkLams res_tvs $ mkLams field_tyvars $
531 mkLams stupid_dict_ids $ mkLams field_dict_ids $
532 Lam data_id $ mk_result sel_body
534 -- NB: A newtype always has a vanilla DataCon; no existentials etc
535 -- res_tys will simply be the dataConUnivTyVars
536 sel_body | isNewTyCon tycon = unwrapNewTypeBody tycon res_tys (Var data_id)
537 | otherwise = Case (Var data_id) data_id field_ty (default_alt ++ the_alts)
539 mk_result poly_result = mkVarApps (mkVarApps poly_result field_tyvars) field_dict_ids
540 -- We pull the field lambdas to the top, so we need to
541 -- apply them in the body. For example:
542 -- data T = MkT { foo :: forall a. a->a }
544 -- foo :: forall a. T -> a -> a
545 -- foo = /\a. \t:T. case t of { MkT f -> f a }
548 = -- In the non-vanilla case, the pattern must bind type variables and
549 -- the context stuff; hence the arg_prefix binding below
550 mkReboxingAlt uniqs data_con (arg_prefix ++ arg_ids) (Var the_arg_id)
552 (arg_prefix, arg_ids)
553 | isVanillaDataCon data_con -- Instantiate from commmon base
554 = ([], mkTemplateLocalsNum arg_base (dataConInstOrigArgTys data_con res_tys))
555 | otherwise -- The case pattern binds type variables, which are used
556 -- in the types of the arguments of the pattern
557 = (dc_tvs ++ mkTemplateLocalsNum arg_base (mkPredTys dc_theta),
558 mkTemplateLocalsNum arg_base' dc_arg_tys)
560 (dc_tvs, dc_theta, dc_arg_tys) = dataConSig data_con
561 arg_base' = arg_base + length dc_theta
563 unpack_base = arg_base' + length dc_arg_tys
564 uniqs = map mkBuiltinUnique [unpack_base..]
566 the_arg_id = assoc "mkRecordSelId:mk_alt" (field_lbls `zip` arg_ids) field_label
567 field_lbls = dataConFieldLabels data_con
569 error_expr = mkRuntimeErrorApp rEC_SEL_ERROR_ID field_tau full_msg
570 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
572 -- unbox a product type...
573 -- we will recurse into newtypes, casting along the way, and unbox at the
574 -- first product data constructor we find. e.g.
576 -- data PairInt = PairInt Int Int
577 -- newtype S = MkS PairInt
580 -- If we have e = MkT (MkS (PairInt 0 1)) and some body expecting a list of
581 -- ids, we get (modulo int passing)
583 -- case (e `cast` (sym CoT)) `cast` (sym CoS) of
584 -- PairInt a b -> body [a,b]
586 -- The Ints passed around are just for creating fresh locals
587 unboxProduct :: Int -> CoreExpr -> Type -> (Int -> [Id] -> CoreExpr) -> Type -> CoreExpr
588 unboxProduct i arg arg_ty body res_ty
591 result = mkUnpackCase the_id arg arg_ty con_args boxing_con rhs
592 (tycon, tycon_args, boxing_con, tys) = deepSplitProductType "unboxProduct" arg_ty
593 ([the_id], i') = mkLocals i [arg_ty]
594 (con_args, i'') = mkLocals i' tys
595 rhs = body i'' con_args
597 mkUnpackCase :: Id -> CoreExpr -> Type -> [Id] -> DataCon -> CoreExpr -> CoreExpr
598 -- (mkUnpackCase x e args Con body)
600 -- case (e `cast` ...) of bndr { Con args -> body }
602 -- the type of the bndr passed in is irrelevent
603 mkUnpackCase bndr arg arg_ty unpk_args boxing_con body
604 = Case cast_arg (setIdType bndr bndr_ty) (exprType body) [(DataAlt boxing_con, unpk_args, body)]
606 (cast_arg, bndr_ty) = go (idType bndr) arg
608 | res@(tycon, tycon_args, _, _) <- splitProductType "mkUnpackCase" ty
609 , isNewTyCon tycon && not (isRecursiveTyCon tycon)
610 = go (newTyConInstRhs tycon tycon_args)
611 (unwrapNewTypeBody tycon tycon_args arg)
612 | otherwise = (arg, ty)
615 reboxProduct :: [Unique] -- uniques to create new local binders
616 -> Type -- type of product to box
617 -> ([Unique], -- remaining uniques
618 CoreExpr, -- boxed product
619 [Id]) -- Ids being boxed into product
622 (tycon, tycon_args, pack_con, con_arg_tys) = deepSplitProductType "reboxProduct" ty
624 us' = dropList con_arg_tys us
626 arg_ids = zipWith (mkSysLocal FSLIT("rb")) us con_arg_tys
628 bind_rhs = mkProductBox arg_ids ty
631 (us', bind_rhs, arg_ids)
633 mkProductBox :: [Id] -> Type -> CoreExpr
634 mkProductBox arg_ids ty
637 (tycon, tycon_args, pack_con, con_arg_tys) = splitProductType "mkProductBox" ty
640 | isNewTyCon tycon && not (isRecursiveTyCon tycon)
641 = wrap (mkProductBox arg_ids (newTyConInstRhs tycon tycon_args))
642 | otherwise = mkConApp pack_con (map Type tycon_args ++ map Var arg_ids)
644 wrap expr = wrapNewTypeBody tycon tycon_args expr
647 -- (mkReboxingAlt us con xs rhs) basically constructs the case
648 -- alternative (con, xs, rhs)
649 -- but it does the reboxing necessary to construct the *source*
650 -- arguments, xs, from the representation arguments ys.
652 -- data T = MkT !(Int,Int) Bool
654 -- mkReboxingAlt MkT [x,b] r
655 -- = (DataAlt MkT, [y::Int,z::Int,b], let x = (y,z) in r)
657 -- mkDataAlt should really be in DataCon, but it can't because
658 -- it manipulates CoreSyn.
661 :: [Unique] -- Uniques for the new Ids
663 -> [Var] -- Source-level args, including existential dicts
667 mkReboxingAlt us con args rhs
668 | not (any isMarkedUnboxed stricts)
669 = (DataAlt con, args, rhs)
673 (binds, args') = go args stricts us
675 (DataAlt con, args', mkLets binds rhs)
678 stricts = dataConExStricts con ++ dataConStrictMarks con
680 go [] stricts us = ([], [])
682 -- Type variable case
683 go (arg:args) stricts us
685 = let (binds, args') = go args stricts us
686 in (binds, arg:args')
688 -- Term variable case
689 go (arg:args) (str:stricts) us
690 | isMarkedUnboxed str
692 let (binds, unpacked_args') = go args stricts us'
693 (us', bind_rhs, unpacked_args) = reboxProduct us (idType arg)
695 (NonRec arg bind_rhs : binds, unpacked_args ++ unpacked_args')
697 = let (binds, args') = go args stricts us
698 in (binds, arg:args')
702 %************************************************************************
704 \subsection{Dictionary selectors}
706 %************************************************************************
708 Selecting a field for a dictionary. If there is just one field, then
709 there's nothing to do.
711 Dictionary selectors may get nested forall-types. Thus:
714 op :: forall b. Ord b => a -> b -> b
716 Then the top-level type for op is
718 op :: forall a. Foo a =>
722 This is unlike ordinary record selectors, which have all the for-alls
723 at the outside. When dealing with classes it's very convenient to
724 recover the original type signature from the class op selector.
727 mkDictSelId :: Name -> Class -> Id
728 mkDictSelId name clas
729 = mkGlobalId (ClassOpId clas) name sel_ty info
731 sel_ty = mkForAllTys tyvars (mkFunTy (idType dict_id) (idType the_arg_id))
732 -- We can't just say (exprType rhs), because that would give a type
734 -- for a single-op class (after all, the selector is the identity)
735 -- But it's type must expose the representation of the dictionary
736 -- to gat (say) C a -> (a -> a)
740 `setUnfoldingInfo` mkTopUnfolding rhs
741 `setAllStrictnessInfo` Just strict_sig
743 -- We no longer use 'must-inline' on record selectors. They'll
744 -- inline like crazy if they scrutinise a constructor
746 -- The strictness signature is of the form U(AAAVAAAA) -> T
747 -- where the V depends on which item we are selecting
748 -- It's worth giving one, so that absence info etc is generated
749 -- even if the selector isn't inlined
750 strict_sig = mkStrictSig (mkTopDmdType [arg_dmd] TopRes)
751 arg_dmd | isNewTyCon tycon = evalDmd
752 | otherwise = Eval (Prod [ if the_arg_id == id then evalDmd else Abs
755 tycon = classTyCon clas
756 [data_con] = tyConDataCons tycon
757 tyvars = dataConUnivTyVars data_con
758 arg_tys = ASSERT( isVanillaDataCon data_con ) dataConRepArgTys data_con
759 the_arg_id = assoc "MkId.mkDictSelId" (map idName (classSelIds clas) `zip` arg_ids) name
761 pred = mkClassPred clas (mkTyVarTys tyvars)
762 (dict_id:arg_ids) = mkTemplateLocals (mkPredTy pred : arg_tys)
764 rhs = mkLams tyvars (Lam dict_id rhs_body)
765 rhs_body | isNewTyCon tycon = unwrapNewTypeBody tycon (map mkTyVarTy tyvars) (Var dict_id)
766 | otherwise = Case (Var dict_id) dict_id (idType the_arg_id)
767 [(DataAlt data_con, arg_ids, Var the_arg_id)]
769 wrapNewTypeBody :: TyCon -> [Type] -> CoreExpr -> CoreExpr
770 -- The wrapper for the data constructor for a newtype looks like this:
771 -- newtype T a = MkT (a,Int)
772 -- MkT :: forall a. (a,Int) -> T a
773 -- MkT = /\a. \(x:(a,Int)). x `cast` CoT a
774 -- where CoT is the coercion TyCon assoicated with the newtype
776 -- The call (wrapNewTypeBody T [a] e) returns the
777 -- body of the wrapper, namely
780 -- If a coercion constructor is prodivided in the newtype, then we use
781 -- it, otherwise the wrap/unwrap are both no-ops
783 wrapNewTypeBody tycon args result_expr
784 | Just co_con <- newTyConCo tycon
785 = Cast result_expr (mkTyConApp co_con args)
789 unwrapNewTypeBody :: TyCon -> [Type] -> CoreExpr -> CoreExpr
790 unwrapNewTypeBody tycon args result_expr
791 | Just co_con <- newTyConCo tycon
792 = Cast result_expr (mkSymCoercion (mkTyConApp co_con args))
800 %************************************************************************
802 \subsection{Primitive operations
804 %************************************************************************
807 mkPrimOpId :: PrimOp -> Id
811 (tyvars,arg_tys,res_ty, arity, strict_sig) = primOpSig prim_op
812 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
813 name = mkWiredInName gHC_PRIM (primOpOcc prim_op)
814 (mkPrimOpIdUnique (primOpTag prim_op))
815 Nothing (AnId id) UserSyntax
816 id = mkGlobalId (PrimOpId prim_op) name ty info
819 `setSpecInfo` mkSpecInfo (primOpRules prim_op name)
821 `setAllStrictnessInfo` Just strict_sig
823 -- For each ccall we manufacture a separate CCallOpId, giving it
824 -- a fresh unique, a type that is correct for this particular ccall,
825 -- and a CCall structure that gives the correct details about calling
828 -- The *name* of this Id is a local name whose OccName gives the full
829 -- details of the ccall, type and all. This means that the interface
830 -- file reader can reconstruct a suitable Id
832 mkFCallId :: Unique -> ForeignCall -> Type -> Id
833 mkFCallId uniq fcall ty
834 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
835 -- A CCallOpId should have no free type variables;
836 -- when doing substitutions won't substitute over it
837 mkGlobalId (FCallId fcall) name ty info
839 occ_str = showSDoc (braces (ppr fcall <+> ppr ty))
840 -- The "occurrence name" of a ccall is the full info about the
841 -- ccall; it is encoded, but may have embedded spaces etc!
843 name = mkFCallName uniq occ_str
847 `setAllStrictnessInfo` Just strict_sig
849 (_, tau) = tcSplitForAllTys ty
850 (arg_tys, _) = tcSplitFunTys tau
851 arity = length arg_tys
852 strict_sig = mkStrictSig (mkTopDmdType (replicate arity evalDmd) TopRes)
856 %************************************************************************
858 \subsection{DictFuns and default methods}
860 %************************************************************************
862 Important notes about dict funs and default methods
863 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
864 Dict funs and default methods are *not* ImplicitIds. Their definition
865 involves user-written code, so we can't figure out their strictness etc
866 based on fixed info, as we can for constructors and record selectors (say).
868 We build them as LocalIds, but with External Names. This ensures that
869 they are taken to account by free-variable finding and dependency
870 analysis (e.g. CoreFVs.exprFreeVars).
872 Why shouldn't they be bound as GlobalIds? Because, in particular, if
873 they are globals, the specialiser floats dict uses above their defns,
874 which prevents good simplifications happening. Also the strictness
875 analyser treats a occurrence of a GlobalId as imported and assumes it
876 contains strictness in its IdInfo, which isn't true if the thing is
877 bound in the same module as the occurrence.
879 It's OK for dfuns to be LocalIds, because we form the instance-env to
880 pass on to the next module (md_insts) in CoreTidy, afer tidying
881 and globalising the top-level Ids.
883 BUT make sure they are *exported* LocalIds (mkExportedLocalId) so
884 that they aren't discarded by the occurrence analyser.
887 mkDefaultMethodId dm_name ty = mkExportedLocalId dm_name ty
889 mkDictFunId :: Name -- Name to use for the dict fun;
896 mkDictFunId dfun_name inst_tyvars dfun_theta clas inst_tys
897 = mkExportedLocalId dfun_name dfun_ty
899 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
901 {- 1 dec 99: disable the Mark Jones optimisation for the sake
902 of compatibility with Hugs.
903 See `types/InstEnv' for a discussion related to this.
905 (class_tyvars, sc_theta, _, _) = classBigSig clas
906 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
907 sc_theta' = substClasses (zipTopTvSubst class_tyvars inst_tys) sc_theta
908 dfun_theta = case inst_decl_theta of
909 [] -> [] -- If inst_decl_theta is empty, then we don't
910 -- want to have any dict arguments, so that we can
911 -- expose the constant methods.
913 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
914 -- Otherwise we pass the superclass dictionaries to
915 -- the dictionary function; the Mark Jones optimisation.
917 -- NOTE the "nub". I got caught by this one:
918 -- class Monad m => MonadT t m where ...
919 -- instance Monad m => MonadT (EnvT env) m where ...
920 -- Here, the inst_decl_theta has (Monad m); but so
921 -- does the sc_theta'!
923 -- NOTE the "not_const". I got caught by this one too:
924 -- class Foo a => Baz a b where ...
925 -- instance Wob b => Baz T b where..
926 -- Now sc_theta' has Foo T
931 %************************************************************************
933 \subsection{Un-definable}
935 %************************************************************************
937 These Ids can't be defined in Haskell. They could be defined in
938 unfoldings in the wired-in GHC.Prim interface file, but we'd have to
939 ensure that they were definitely, definitely inlined, because there is
940 no curried identifier for them. That's what mkCompulsoryUnfolding
941 does. If we had a way to get a compulsory unfolding from an interface
942 file, we could do that, but we don't right now.
944 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
945 just gets expanded into a type coercion wherever it occurs. Hence we
946 add it as a built-in Id with an unfolding here.
948 The type variables we use here are "open" type variables: this means
949 they can unify with both unlifted and lifted types. Hence we provide
950 another gun with which to shoot yourself in the foot.
953 mkWiredInIdName mod fs uniq id
954 = mkWiredInName mod (mkOccNameFS varName fs) uniq Nothing (AnId id) UserSyntax
956 unsafeCoerceName = mkWiredInIdName gHC_PRIM FSLIT("unsafeCoerce#") unsafeCoerceIdKey unsafeCoerceId
957 nullAddrName = mkWiredInIdName gHC_PRIM FSLIT("nullAddr#") nullAddrIdKey nullAddrId
958 seqName = mkWiredInIdName gHC_PRIM FSLIT("seq") seqIdKey seqId
959 realWorldName = mkWiredInIdName gHC_PRIM FSLIT("realWorld#") realWorldPrimIdKey realWorldPrimId
960 lazyIdName = mkWiredInIdName gHC_BASE FSLIT("lazy") lazyIdKey lazyId
962 errorName = mkWiredInIdName gHC_ERR FSLIT("error") errorIdKey eRROR_ID
963 recSelErrorName = mkWiredInIdName gHC_ERR FSLIT("recSelError") recSelErrorIdKey rEC_SEL_ERROR_ID
964 runtimeErrorName = mkWiredInIdName gHC_ERR FSLIT("runtimeError") runtimeErrorIdKey rUNTIME_ERROR_ID
965 irrefutPatErrorName = mkWiredInIdName gHC_ERR FSLIT("irrefutPatError") irrefutPatErrorIdKey iRREFUT_PAT_ERROR_ID
966 recConErrorName = mkWiredInIdName gHC_ERR FSLIT("recConError") recConErrorIdKey rEC_CON_ERROR_ID
967 patErrorName = mkWiredInIdName gHC_ERR FSLIT("patError") patErrorIdKey pAT_ERROR_ID
968 noMethodBindingErrorName = mkWiredInIdName gHC_ERR FSLIT("noMethodBindingError")
969 noMethodBindingErrorIdKey nO_METHOD_BINDING_ERROR_ID
970 nonExhaustiveGuardsErrorName
971 = mkWiredInIdName gHC_ERR FSLIT("nonExhaustiveGuardsError")
972 nonExhaustiveGuardsErrorIdKey nON_EXHAUSTIVE_GUARDS_ERROR_ID
976 -- unsafeCoerce# :: forall a b. a -> b
978 = pcMiscPrelId unsafeCoerceName ty info
980 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
983 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
984 (mkFunTy openAlphaTy openBetaTy)
985 [x] = mkTemplateLocals [openAlphaTy]
986 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
987 -- Note (Coerce openBetaTy openAlphaTy) (Var x)
988 Cast (Var x) (mkUnsafeCoercion openAlphaTy openBetaTy)
990 -- nullAddr# :: Addr#
991 -- The reason is is here is because we don't provide
992 -- a way to write this literal in Haskell.
994 = pcMiscPrelId nullAddrName addrPrimTy info
996 info = noCafIdInfo `setUnfoldingInfo`
997 mkCompulsoryUnfolding (Lit nullAddrLit)
1000 = pcMiscPrelId seqName ty info
1002 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
1005 ty = mkForAllTys [alphaTyVar,openBetaTyVar]
1006 (mkFunTy alphaTy (mkFunTy openBetaTy openBetaTy))
1007 [x,y] = mkTemplateLocals [alphaTy, openBetaTy]
1008 rhs = mkLams [alphaTyVar,openBetaTyVar,x,y] (Case (Var x) x openBetaTy [(DEFAULT, [], Var y)])
1010 -- lazy :: forall a?. a? -> a? (i.e. works for unboxed types too)
1011 -- Used to lazify pseq: pseq a b = a `seq` lazy b
1013 -- Also, no strictness: by being a built-in Id, all the info about lazyId comes from here,
1014 -- not from GHC.Base.hi. This is important, because the strictness
1015 -- analyser will spot it as strict!
1017 -- Also no unfolding in lazyId: it gets "inlined" by a HACK in the worker/wrapper pass
1018 -- (see WorkWrap.wwExpr)
1019 -- We could use inline phases to do this, but that would be vulnerable to changes in
1020 -- phase numbering....we must inline precisely after strictness analysis.
1022 = pcMiscPrelId lazyIdName ty info
1025 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy alphaTy)
1027 lazyIdUnfolding :: CoreExpr -- Used to expand 'lazyId' after strictness anal
1028 lazyIdUnfolding = mkLams [openAlphaTyVar,x] (Var x)
1030 [x] = mkTemplateLocals [openAlphaTy]
1033 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
1034 nasty as-is, change it back to a literal (@Literal@).
1036 voidArgId is a Local Id used simply as an argument in functions
1037 where we just want an arg to avoid having a thunk of unlifted type.
1039 x = \ void :: State# RealWorld -> (# p, q #)
1041 This comes up in strictness analysis
1044 realWorldPrimId -- :: State# RealWorld
1045 = pcMiscPrelId realWorldName realWorldStatePrimTy
1046 (noCafIdInfo `setUnfoldingInfo` evaldUnfolding)
1047 -- The evaldUnfolding makes it look that realWorld# is evaluated
1048 -- which in turn makes Simplify.interestingArg return True,
1049 -- which in turn makes INLINE things applied to realWorld# likely
1052 voidArgId -- :: State# RealWorld
1053 = mkSysLocal FSLIT("void") voidArgIdKey realWorldStatePrimTy
1057 %************************************************************************
1059 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
1061 %************************************************************************
1063 GHC randomly injects these into the code.
1065 @patError@ is just a version of @error@ for pattern-matching
1066 failures. It knows various ``codes'' which expand to longer
1067 strings---this saves space!
1069 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
1070 well shouldn't be yanked on, but if one is, then you will get a
1071 friendly message from @absentErr@ (rather than a totally random
1074 @parError@ is a special version of @error@ which the compiler does
1075 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
1076 templates, but we don't ever expect to generate code for it.
1080 :: Id -- Should be of type (forall a. Addr# -> a)
1081 -- where Addr# points to a UTF8 encoded string
1082 -> Type -- The type to instantiate 'a'
1083 -> String -- The string to print
1086 mkRuntimeErrorApp err_id res_ty err_msg
1087 = mkApps (Var err_id) [Type res_ty, err_string]
1089 err_string = Lit (mkStringLit err_msg)
1091 rEC_SEL_ERROR_ID = mkRuntimeErrorId recSelErrorName
1092 rUNTIME_ERROR_ID = mkRuntimeErrorId runtimeErrorName
1093 iRREFUT_PAT_ERROR_ID = mkRuntimeErrorId irrefutPatErrorName
1094 rEC_CON_ERROR_ID = mkRuntimeErrorId recConErrorName
1095 pAT_ERROR_ID = mkRuntimeErrorId patErrorName
1096 nO_METHOD_BINDING_ERROR_ID = mkRuntimeErrorId noMethodBindingErrorName
1097 nON_EXHAUSTIVE_GUARDS_ERROR_ID = mkRuntimeErrorId nonExhaustiveGuardsErrorName
1099 -- The runtime error Ids take a UTF8-encoded string as argument
1100 mkRuntimeErrorId name = pc_bottoming_Id name runtimeErrorTy
1101 runtimeErrorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTy addrPrimTy openAlphaTy)
1105 eRROR_ID = pc_bottoming_Id errorName errorTy
1108 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy] openAlphaTy)
1109 -- Notice the openAlphaTyVar. It says that "error" can be applied
1110 -- to unboxed as well as boxed types. This is OK because it never
1111 -- returns, so the return type is irrelevant.
1115 %************************************************************************
1117 \subsection{Utilities}
1119 %************************************************************************
1122 pcMiscPrelId :: Name -> Type -> IdInfo -> Id
1123 pcMiscPrelId name ty info
1124 = mkVanillaGlobal name ty info
1125 -- We lie and say the thing is imported; otherwise, we get into
1126 -- a mess with dependency analysis; e.g., core2stg may heave in
1127 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
1128 -- being compiled, then it's just a matter of luck if the definition
1129 -- will be in "the right place" to be in scope.
1131 pc_bottoming_Id name ty
1132 = pcMiscPrelId name ty bottoming_info
1134 bottoming_info = vanillaIdInfo `setAllStrictnessInfo` Just strict_sig
1135 -- Do *not* mark them as NoCafRefs, because they can indeed have
1136 -- CAF refs. For example, pAT_ERROR_ID calls GHC.Err.untangle,
1137 -- which has some CAFs
1138 -- In due course we may arrange that these error-y things are
1139 -- regarded by the GC as permanently live, in which case we
1140 -- can give them NoCaf info. As it is, any function that calls
1141 -- any pc_bottoming_Id will itself have CafRefs, which bloats
1144 strict_sig = mkStrictSig (mkTopDmdType [evalDmd] BotRes)
1145 -- These "bottom" out, no matter what their arguments
1147 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
1148 openAlphaTy = mkTyVarTy openAlphaTyVar
1149 openBetaTy = mkTyVarTy openBetaTyVar