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,
51 mkTopTvSubst, substTyVar )
52 import TcGadt ( gadtRefine, refineType, emptyRefinement )
53 import HsBinds ( ExprCoFn(..), isIdCoercion )
54 import Coercion ( mkSymCoercion, mkUnsafeCoercion,
55 splitNewTypeRepCo_maybe, isEqPred )
56 import TcType ( Type, ThetaType, mkDictTy, mkPredTys, mkPredTy,
57 mkTyConApp, mkTyVarTys, mkClassPred, isPredTy,
58 mkFunTys, mkFunTy, mkSigmaTy, tcSplitSigmaTy, tcEqType,
59 isUnLiftedType, mkForAllTys, mkTyVarTy, tyVarsOfType,
60 tcSplitFunTys, tcSplitForAllTys, dataConsStupidTheta
62 import CoreUtils ( exprType, dataConOrigInstPat )
63 import CoreUnfold ( mkTopUnfolding, mkCompulsoryUnfolding )
64 import Literal ( nullAddrLit, mkStringLit )
65 import TyCon ( TyCon, isNewTyCon, tyConDataCons, FieldLabel,
66 tyConStupidTheta, isProductTyCon, isDataTyCon, isRecursiveTyCon,
67 newTyConCo, tyConArity )
68 import Class ( Class, classTyCon, classSelIds )
69 import Var ( Id, TyVar, Var, setIdType, mkCoVar, mkWildCoVar )
70 import VarSet ( isEmptyVarSet, subVarSet, varSetElems )
71 import Name ( mkFCallName, mkWiredInName, Name, BuiltInSyntax(..),
73 import OccName ( mkOccNameFS, varName )
74 import PrimOp ( PrimOp, primOpSig, primOpOcc, primOpTag )
75 import ForeignCall ( ForeignCall )
76 import DataCon ( DataCon, DataConIds(..), dataConTyCon, dataConUnivTyVars,
77 dataConFieldLabels, dataConRepArity, dataConResTys,
78 dataConRepArgTys, dataConRepType, dataConFullSig,
79 dataConSig, dataConStrictMarks, dataConExStricts,
80 splitProductType, isVanillaDataCon, dataConFieldType,
81 dataConInstOrigArgTys, deepSplitProductType
83 import Id ( idType, mkGlobalId, mkVanillaGlobal, mkSysLocal,
84 mkTemplateLocals, mkTemplateLocalsNum, mkExportedLocalId,
85 mkTemplateLocal, idName, mkWildId
87 import IdInfo ( IdInfo, noCafIdInfo, setUnfoldingInfo,
88 setArityInfo, setSpecInfo, setCafInfo,
89 setAllStrictnessInfo, vanillaIdInfo,
90 GlobalIdDetails(..), CafInfo(..)
92 import NewDemand ( mkStrictSig, DmdResult(..),
93 mkTopDmdType, topDmd, evalDmd, lazyDmd, retCPR,
94 Demand(..), Demands(..) )
95 import DmdAnal ( dmdAnalTopRhs )
97 import Unique ( mkBuiltinUnique, mkPrimOpIdUnique )
100 import Util ( dropList, isSingleton )
103 import ListSetOps ( assoc, minusList )
106 %************************************************************************
108 \subsection{Wired in Ids}
110 %************************************************************************
114 = [ -- These error-y things are wired in because we don't yet have
115 -- a way to express in an interface file that the result type variable
116 -- is 'open'; that is can be unified with an unboxed type
118 -- [The interface file format now carry such information, but there's
119 -- no way yet of expressing at the definition site for these
120 -- error-reporting functions that they have an 'open'
121 -- result type. -- sof 1/99]
123 eRROR_ID, -- This one isn't used anywhere else in the compiler
124 -- But we still need it in wiredInIds so that when GHC
125 -- compiles a program that mentions 'error' we don't
126 -- import its type from the interface file; we just get
127 -- the Id defined here. Which has an 'open-tyvar' type.
130 iRREFUT_PAT_ERROR_ID,
131 nON_EXHAUSTIVE_GUARDS_ERROR_ID,
132 nO_METHOD_BINDING_ERROR_ID,
139 -- These Ids are exported from GHC.Prim
141 = [ -- These can't be defined in Haskell, but they have
142 -- perfectly reasonable unfoldings in Core
150 %************************************************************************
152 \subsection{Data constructors}
154 %************************************************************************
156 The wrapper for a constructor is an ordinary top-level binding that evaluates
157 any strict args, unboxes any args that are going to be flattened, and calls
160 We're going to build a constructor that looks like:
162 data (Data a, C b) => T a b = T1 !a !Int b
165 \d1::Data a, d2::C b ->
166 \p q r -> case p of { p ->
168 Con T1 [a,b] [p,q,r]}}
172 * d2 is thrown away --- a context in a data decl is used to make sure
173 one *could* construct dictionaries at the site the constructor
174 is used, but the dictionary isn't actually used.
176 * We have to check that we can construct Data dictionaries for
177 the types a and Int. Once we've done that we can throw d1 away too.
179 * We use (case p of q -> ...) to evaluate p, rather than "seq" because
180 all that matters is that the arguments are evaluated. "seq" is
181 very careful to preserve evaluation order, which we don't need
184 You might think that we could simply give constructors some strictness
185 info, like PrimOps, and let CoreToStg do the let-to-case transformation.
186 But we don't do that because in the case of primops and functions strictness
187 is a *property* not a *requirement*. In the case of constructors we need to
188 do something active to evaluate the argument.
190 Making an explicit case expression allows the simplifier to eliminate
191 it in the (common) case where the constructor arg is already evaluated.
195 mkDataConIds :: Name -> Name -> DataCon -> DataConIds
196 mkDataConIds wrap_name wkr_name data_con
200 | any isMarkedStrict all_strict_marks -- Algebraic, needs wrapper
201 || not (null eq_spec)
202 = AlgDC (Just alg_wrap_id) wrk_id
204 | otherwise -- Algebraic, no wrapper
205 = AlgDC Nothing wrk_id
207 (univ_tvs, ex_tvs, eq_spec, theta, orig_arg_tys) = dataConFullSig data_con
208 tycon = dataConTyCon data_con
210 ----------- Wrapper --------------
211 -- We used to include the stupid theta in the wrapper's args
212 -- but now we don't. Instead the type checker just injects these
213 -- extra constraints where necessary.
214 wrap_tvs = (univ_tvs `minusList` map fst eq_spec) ++ ex_tvs
215 subst = mkTopTvSubst eq_spec
216 dict_tys = mkPredTys theta
217 result_ty_args = map (substTyVar subst) univ_tvs
218 result_ty = mkTyConApp tycon result_ty_args
219 wrap_ty = mkForAllTys wrap_tvs $ mkFunTys dict_tys $
220 mkFunTys orig_arg_tys $ result_ty
221 -- NB: watch out here if you allow user-written equality
222 -- constraints in data constructor signatures
224 ----------- Worker (algebraic data types only) --------------
225 -- The *worker* for the data constructor is the function that
226 -- takes the representation arguments and builds the constructor.
227 wrk_id = mkGlobalId (DataConWorkId data_con) wkr_name
228 (dataConRepType data_con) wkr_info
230 wkr_arity = dataConRepArity data_con
231 wkr_info = noCafIdInfo
232 `setArityInfo` wkr_arity
233 `setAllStrictnessInfo` Just wkr_sig
234 `setUnfoldingInfo` evaldUnfolding -- Record that it's evaluated,
237 wkr_sig = mkStrictSig (mkTopDmdType (replicate wkr_arity topDmd) cpr_info)
238 -- Notice that we do *not* say the worker is strict
239 -- even if the data constructor is declared strict
240 -- e.g. data T = MkT !(Int,Int)
241 -- Why? Because the *wrapper* is strict (and its unfolding has case
242 -- expresssions that do the evals) but the *worker* itself is not.
243 -- If we pretend it is strict then when we see
244 -- case x of y -> $wMkT y
245 -- the simplifier thinks that y is "sure to be evaluated" (because
246 -- $wMkT is strict) and drops the case. No, $wMkT is not strict.
248 -- When the simplifer sees a pattern
249 -- case e of MkT x -> ...
250 -- it uses the dataConRepStrictness of MkT to mark x as evaluated;
251 -- but that's fine... dataConRepStrictness comes from the data con
252 -- not from the worker Id.
254 cpr_info | isProductTyCon tycon &&
257 wkr_arity <= mAX_CPR_SIZE = retCPR
259 -- RetCPR is only true for products that are real data types;
260 -- that is, not unboxed tuples or [non-recursive] newtypes
262 ----------- Wrappers for newtypes --------------
263 nt_wrap_id = mkGlobalId (DataConWrapId data_con) wrap_name wrap_ty nt_wrap_info
264 nt_wrap_info = noCafIdInfo -- The NoCaf-ness is set by noCafIdInfo
265 `setArityInfo` 1 -- Arity 1
266 `setUnfoldingInfo` newtype_unf
267 newtype_unf = ASSERT( isVanillaDataCon data_con &&
268 isSingleton orig_arg_tys )
269 -- No existentials on a newtype, but it can have a context
270 -- e.g. newtype Eq a => T a = MkT (...)
271 mkCompulsoryUnfolding $
272 mkLams wrap_tvs $ Lam id_arg1 $
273 wrapNewTypeBody tycon result_ty_args
276 id_arg1 = mkTemplateLocal 1 (head orig_arg_tys)
278 ----------- Wrappers for algebraic data types --------------
279 alg_wrap_id = mkGlobalId (DataConWrapId data_con) wrap_name wrap_ty alg_wrap_info
280 alg_wrap_info = noCafIdInfo -- The NoCaf-ness is set by noCafIdInfo
281 `setArityInfo` alg_arity
282 -- It's important to specify the arity, so that partial
283 -- applications are treated as values
284 `setUnfoldingInfo` alg_unf
285 `setAllStrictnessInfo` Just wrap_sig
287 all_strict_marks = dataConExStricts data_con ++ dataConStrictMarks data_con
288 wrap_sig = mkStrictSig (mkTopDmdType arg_dmds cpr_info)
289 arg_dmds = map mk_dmd all_strict_marks
290 mk_dmd str | isMarkedStrict str = evalDmd
291 | otherwise = lazyDmd
292 -- The Cpr info can be important inside INLINE rhss, where the
293 -- wrapper constructor isn't inlined.
294 -- And the argument strictness can be important too; we
295 -- may not inline a contructor when it is partially applied.
297 -- data W = C !Int !Int !Int
298 -- ...(let w = C x in ...(w p q)...)...
299 -- we want to see that w is strict in its two arguments
301 alg_unf = mkTopUnfolding $ Note InlineMe $
303 mkLams dict_args $ mkLams id_args $
304 foldr mk_case con_app
305 (zip (dict_args ++ id_args) all_strict_marks)
308 con_app i rep_ids = Var wrk_id `mkTyApps` result_ty_args
310 `mkTyApps` map snd eq_spec
311 `mkVarApps` reverse rep_ids
313 (dict_args,i2) = mkLocals 1 dict_tys
314 (id_args,i3) = mkLocals i2 orig_arg_tys
318 :: (Id, StrictnessMark) -- Arg, strictness
319 -> (Int -> [Id] -> CoreExpr) -- Body
320 -> Int -- Next rep arg id
321 -> [Id] -- Rep args so far, reversed
323 mk_case (arg,strict) body i rep_args
325 NotMarkedStrict -> body i (arg:rep_args)
327 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
329 Case (Var arg) arg result_ty [(DEFAULT,[], body i (arg:rep_args))]
332 -> unboxProduct i (Var arg) (idType arg) the_body result_ty
334 the_body i con_args = body i (reverse con_args ++ rep_args)
336 mAX_CPR_SIZE :: Arity
338 -- We do not treat very big tuples as CPR-ish:
339 -- a) for a start we get into trouble because there aren't
340 -- "enough" unboxed tuple types (a tiresome restriction,
342 -- b) more importantly, big unboxed tuples get returned mainly
343 -- on the stack, and are often then allocated in the heap
344 -- by the caller. So doing CPR for them may in fact make
347 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
353 %************************************************************************
355 \subsection{Record selectors}
357 %************************************************************************
359 We're going to build a record selector unfolding that looks like this:
361 data T a b c = T1 { ..., op :: a, ...}
362 | T2 { ..., op :: a, ...}
365 sel = /\ a b c -> \ d -> case d of
370 Similarly for newtypes
372 newtype N a = MkN { unN :: a->a }
375 unN n = coerce (a->a) n
377 We need to take a little care if the field has a polymorphic type:
379 data R = R { f :: forall a. a->a }
383 f :: forall a. R -> a -> a
384 f = /\ a \ r = case r of
387 (not f :: R -> forall a. a->a, which gives the type inference mechanism
388 problems at call sites)
390 Similarly for (recursive) newtypes
392 newtype N = MkN { unN :: forall a. a->a }
394 unN :: forall b. N -> b -> b
395 unN = /\b -> \n:N -> (coerce (forall a. a->a) n)
398 Note [Naughty record selectors]
399 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
400 A "naughty" field is one for which we can't define a record
401 selector, because an existential type variable would escape. For example:
402 data T = forall a. MkT { x,y::a }
403 We obviously can't define
405 Nevertheless we *do* put a RecordSelId into the type environment
406 so that if the user tries to use 'x' as a selector we can bleat
407 helpfully, rather than saying unhelpfully that 'x' is not in scope.
408 Hence the sel_naughty flag, to identify record selectors that don't really exist.
410 In general, a field is naughty if its type mentions a type variable that
411 isn't in the result type of the constructor.
413 Note [GADT record selectors]
414 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
415 For GADTs, we require that all constructors with a common field 'f' have the same
416 result type (modulo alpha conversion). [Checked in TcTyClsDecls.checkValidTyCon]
419 T1 { f :: a } :: T [a]
420 T2 { f :: a, y :: b } :: T [a]
421 and now the selector takes that type as its argument:
422 f :: forall a. T [a] -> a
426 Note the forall'd tyvars of the selector are just the free tyvars
427 of the result type; there may be other tyvars in the constructor's
428 type (e.g. 'b' in T2).
432 -- Steps for handling "naughty" vs "non-naughty" selectors:
433 -- 1. Determine naughtiness by comparing field type vs result type
434 -- 2. Install naughty ones with selector_ty of type _|_ and fill in mzero for info
435 -- 3. If it's not naughty, do the normal plan.
437 mkRecordSelId :: TyCon -> FieldLabel -> Id
438 mkRecordSelId tycon field_label
439 -- Assumes that all fields with the same field label have the same type
440 | is_naughty = naughty_id
443 is_naughty = not (tyVarsOfType field_ty `subVarSet` res_tv_set)
444 sel_id_details = RecordSelId tycon field_label is_naughty
446 -- Escapist case here for naughty construcotrs
447 -- We give it no IdInfo, and a type of forall a.a (never looked at)
448 naughty_id = mkGlobalId sel_id_details field_label forall_a_a noCafIdInfo
449 forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar)
451 -- Normal case starts here
452 sel_id = mkGlobalId sel_id_details field_label selector_ty info
453 data_cons = tyConDataCons tycon
454 data_cons_w_field = filter has_field data_cons -- Can't be empty!
455 has_field con = field_label `elem` dataConFieldLabels con
457 con1 = head data_cons_w_field
458 res_tys = dataConResTys con1
459 res_tv_set = tyVarsOfTypes res_tys
460 res_tvs = varSetElems res_tv_set
461 data_ty = mkTyConApp tycon res_tys
462 field_ty = dataConFieldType con1 field_label
464 -- *Very* tiresomely, the selectors are (unnecessarily!) overloaded over
465 -- just the dictionaries in the types of the constructors that contain
466 -- the relevant field. [The Report says that pattern matching on a
467 -- constructor gives the same constraints as applying it.] Urgh.
469 -- However, not all data cons have all constraints (because of
470 -- BuildTyCl.mkDataConStupidTheta). So we need to find all the data cons
471 -- involved in the pattern match and take the union of their constraints.
472 stupid_dict_tys = mkPredTys (dataConsStupidTheta data_cons_w_field)
473 n_stupid_dicts = length stupid_dict_tys
475 (field_tyvars,pre_field_theta,field_tau) = tcSplitSigmaTy field_ty
477 field_theta = filter (not . isEqPred) pre_field_theta
478 field_dict_tys = mkPredTys field_theta
479 n_field_dict_tys = length field_dict_tys
480 -- If the field has a universally quantified type we have to
481 -- be a bit careful. Suppose we have
482 -- data R = R { op :: forall a. Foo a => a -> a }
483 -- Then we can't give op the type
484 -- op :: R -> forall a. Foo a => a -> a
485 -- because the typechecker doesn't understand foralls to the
486 -- right of an arrow. The "right" type to give it is
487 -- op :: forall a. Foo a => R -> a -> a
488 -- But then we must generate the right unfolding too:
489 -- op = /\a -> \dfoo -> \ r ->
492 -- Note that this is exactly the type we'd infer from a user defn
496 selector_ty = mkForAllTys res_tvs $ mkForAllTys field_tyvars $
497 mkFunTys stupid_dict_tys $ mkFunTys field_dict_tys $
498 mkFunTy data_ty field_tau
500 arity = 1 + n_stupid_dicts + n_field_dict_tys
502 (strict_sig, rhs_w_str) = dmdAnalTopRhs sel_rhs
503 -- Use the demand analyser to work out strictness.
504 -- With all this unpackery it's not easy!
507 `setCafInfo` caf_info
509 `setUnfoldingInfo` mkTopUnfolding rhs_w_str
510 `setAllStrictnessInfo` Just strict_sig
512 -- Allocate Ids. We do it a funny way round because field_dict_tys is
513 -- almost always empty. Also note that we use max_dict_tys
514 -- rather than n_dict_tys, because the latter gives an infinite loop:
515 -- n_dict tys depends on the_alts, which depens on arg_ids, which depends
516 -- on arity, which depends on n_dict tys. Sigh! Mega sigh!
517 stupid_dict_ids = mkTemplateLocalsNum 1 stupid_dict_tys
518 max_stupid_dicts = length (tyConStupidTheta tycon)
519 field_dict_base = max_stupid_dicts + 1
520 field_dict_ids = mkTemplateLocalsNum field_dict_base field_dict_tys
521 dict_id_base = field_dict_base + n_field_dict_tys
522 data_id = mkTemplateLocal dict_id_base data_ty
523 arg_base = dict_id_base + 1
525 the_alts :: [CoreAlt]
526 the_alts = map mk_alt data_cons_w_field -- Already sorted by data-con
527 no_default = length data_cons == length data_cons_w_field -- No default needed
529 default_alt | no_default = []
530 | otherwise = [(DEFAULT, [], error_expr)]
532 -- The default branch may have CAF refs, because it calls recSelError etc.
533 caf_info | no_default = NoCafRefs
534 | otherwise = MayHaveCafRefs
536 sel_rhs = mkLams res_tvs $ mkLams field_tyvars $
537 mkLams stupid_dict_ids $ mkLams field_dict_ids $
538 Lam data_id $ mk_result sel_body
540 -- NB: A newtype always has a vanilla DataCon; no existentials etc
541 -- res_tys will simply be the dataConUnivTyVars
542 sel_body | isNewTyCon tycon = unwrapNewTypeBody tycon res_tys (Var data_id)
543 | otherwise = Case (Var data_id) data_id field_ty (default_alt ++ the_alts)
545 mk_result poly_result = mkVarApps (mkVarApps poly_result field_tyvars) field_dict_ids
546 -- We pull the field lambdas to the top, so we need to
547 -- apply them in the body. For example:
548 -- data T = MkT { foo :: forall a. a->a }
550 -- foo :: forall a. T -> a -> a
551 -- foo = /\a. \t:T. case t of { MkT f -> f a }
554 = -- In the non-vanilla case, the pattern must bind type variables and
555 -- the context stuff; hence the arg_prefix binding below
556 ASSERT2( res_ty `tcEqType` field_tau, ppr data_con $$ ppr res_ty $$ ppr field_tau )
557 mkReboxingAlt rebox_uniqs data_con (ex_tvs ++ co_tvs ++ arg_vs) rhs
559 -- get pattern binders with types appropriately instantiated
560 arg_uniqs = map mkBuiltinUnique [arg_base..]
561 (ex_tvs, co_tvs, arg_vs) = dataConOrigInstPat arg_uniqs data_con res_tys
563 rebox_base = arg_base + length ex_tvs + length co_tvs + length arg_vs
564 rebox_uniqs = map mkBuiltinUnique [rebox_base..]
566 -- data T :: *->* where T1 { fld :: Maybe b } -> T [b]
567 -- Hence T1 :: forall a b. (a=[b]) => b -> T a
568 -- fld :: forall b. T [b] -> Maybe b
569 -- fld = /\b.\(t:T[b]). case t of
570 -- T1 b' (c : [b]=[b']) (x:Maybe b')
571 -- -> x `cast` Maybe (sym (right c))
573 Succeeded refinement = gadtRefine emptyRefinement ex_tvs co_tvs
574 (co_fn, res_ty) = refineType refinement (idType the_arg_id)
575 -- Generate the refinement for b'=b,
576 -- and apply to (Maybe b'), to get (Maybe b)
579 ExprCoFn co -> Cast (Var the_arg_id) co
580 id_co -> ASSERT(isIdCoercion id_co) Var the_arg_id
582 field_vs = filter (not . isPredTy . idType) arg_vs
583 the_arg_id = assoc "mkRecordSelId:mk_alt" (field_lbls `zip` field_vs) field_label
584 field_lbls = dataConFieldLabels data_con
586 error_expr = mkRuntimeErrorApp rEC_SEL_ERROR_ID field_tau full_msg
587 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
589 -- unbox a product type...
590 -- we will recurse into newtypes, casting along the way, and unbox at the
591 -- first product data constructor we find. e.g.
593 -- data PairInt = PairInt Int Int
594 -- newtype S = MkS PairInt
597 -- If we have e = MkT (MkS (PairInt 0 1)) and some body expecting a list of
598 -- ids, we get (modulo int passing)
600 -- case (e `cast` (sym CoT)) `cast` (sym CoS) of
601 -- PairInt a b -> body [a,b]
603 -- The Ints passed around are just for creating fresh locals
604 unboxProduct :: Int -> CoreExpr -> Type -> (Int -> [Id] -> CoreExpr) -> Type -> CoreExpr
605 unboxProduct i arg arg_ty body res_ty
608 result = mkUnpackCase the_id arg arg_ty con_args boxing_con rhs
609 (_tycon, _tycon_args, boxing_con, tys) = deepSplitProductType "unboxProduct" arg_ty
610 ([the_id], i') = mkLocals i [arg_ty]
611 (con_args, i'') = mkLocals i' tys
612 rhs = body i'' con_args
614 mkUnpackCase :: Id -> CoreExpr -> Type -> [Id] -> DataCon -> CoreExpr -> CoreExpr
615 -- (mkUnpackCase x e args Con body)
617 -- case (e `cast` ...) of bndr { Con args -> body }
619 -- the type of the bndr passed in is irrelevent
620 mkUnpackCase bndr arg arg_ty unpk_args boxing_con body
621 = Case cast_arg (setIdType bndr bndr_ty) (exprType body) [(DataAlt boxing_con, unpk_args, body)]
623 (cast_arg, bndr_ty) = go (idType bndr) arg
625 | res@(tycon, tycon_args, _, _) <- splitProductType "mkUnpackCase" ty
626 , isNewTyCon tycon && not (isRecursiveTyCon tycon)
627 = go (newTyConInstRhs tycon tycon_args)
628 (unwrapNewTypeBody tycon tycon_args arg)
629 | otherwise = (arg, ty)
632 reboxProduct :: [Unique] -- uniques to create new local binders
633 -> Type -- type of product to box
634 -> ([Unique], -- remaining uniques
635 CoreExpr, -- boxed product
636 [Id]) -- Ids being boxed into product
639 (_tycon, _tycon_args, _pack_con, con_arg_tys) = deepSplitProductType "reboxProduct" ty
641 us' = dropList con_arg_tys us
643 arg_ids = zipWith (mkSysLocal FSLIT("rb")) us con_arg_tys
645 bind_rhs = mkProductBox arg_ids ty
648 (us', bind_rhs, arg_ids)
650 mkProductBox :: [Id] -> Type -> CoreExpr
651 mkProductBox arg_ids ty
654 (tycon, tycon_args, pack_con, _con_arg_tys) = splitProductType "mkProductBox" ty
657 | isNewTyCon tycon && not (isRecursiveTyCon tycon)
658 = wrap (mkProductBox arg_ids (newTyConInstRhs tycon tycon_args))
659 | otherwise = mkConApp pack_con (map Type tycon_args ++ map Var arg_ids)
661 wrap expr = wrapNewTypeBody tycon tycon_args expr
664 -- (mkReboxingAlt us con xs rhs) basically constructs the case
665 -- alternative (con, xs, rhs)
666 -- but it does the reboxing necessary to construct the *source*
667 -- arguments, xs, from the representation arguments ys.
669 -- data T = MkT !(Int,Int) Bool
671 -- mkReboxingAlt MkT [x,b] r
672 -- = (DataAlt MkT, [y::Int,z::Int,b], let x = (y,z) in r)
674 -- mkDataAlt should really be in DataCon, but it can't because
675 -- it manipulates CoreSyn.
678 :: [Unique] -- Uniques for the new Ids
680 -> [Var] -- Source-level args, including existential dicts
684 mkReboxingAlt us con args rhs
685 | not (any isMarkedUnboxed stricts)
686 = (DataAlt con, args, rhs)
690 (binds, args') = go args stricts us
692 (DataAlt con, args', mkLets binds rhs)
695 stricts = dataConExStricts con ++ dataConStrictMarks con
697 go [] stricts us = ([], [])
699 -- Type variable case
700 go (arg:args) stricts us
702 = let (binds, args') = go args stricts us
703 in (binds, arg:args')
705 -- Term variable case
706 go (arg:args) (str:stricts) us
707 | isMarkedUnboxed str
709 let (binds, unpacked_args') = go args stricts us'
710 (us', bind_rhs, unpacked_args) = reboxProduct us (idType arg)
712 (NonRec arg bind_rhs : binds, unpacked_args ++ unpacked_args')
714 = let (binds, args') = go args stricts us
715 in (binds, arg:args')
719 %************************************************************************
721 \subsection{Dictionary selectors}
723 %************************************************************************
725 Selecting a field for a dictionary. If there is just one field, then
726 there's nothing to do.
728 Dictionary selectors may get nested forall-types. Thus:
731 op :: forall b. Ord b => a -> b -> b
733 Then the top-level type for op is
735 op :: forall a. Foo a =>
739 This is unlike ordinary record selectors, which have all the for-alls
740 at the outside. When dealing with classes it's very convenient to
741 recover the original type signature from the class op selector.
744 mkDictSelId :: Name -> Class -> Id
745 mkDictSelId name clas
746 = mkGlobalId (ClassOpId clas) name sel_ty info
748 sel_ty = mkForAllTys tyvars (mkFunTy (idType dict_id) (idType the_arg_id))
749 -- We can't just say (exprType rhs), because that would give a type
751 -- for a single-op class (after all, the selector is the identity)
752 -- But it's type must expose the representation of the dictionary
753 -- to gat (say) C a -> (a -> a)
757 `setUnfoldingInfo` mkTopUnfolding rhs
758 `setAllStrictnessInfo` Just strict_sig
760 -- We no longer use 'must-inline' on record selectors. They'll
761 -- inline like crazy if they scrutinise a constructor
763 -- The strictness signature is of the form U(AAAVAAAA) -> T
764 -- where the V depends on which item we are selecting
765 -- It's worth giving one, so that absence info etc is generated
766 -- even if the selector isn't inlined
767 strict_sig = mkStrictSig (mkTopDmdType [arg_dmd] TopRes)
768 arg_dmd | isNewTyCon tycon = evalDmd
769 | otherwise = Eval (Prod [ if the_arg_id == id then evalDmd else Abs
772 tycon = classTyCon clas
773 [data_con] = tyConDataCons tycon
774 tyvars = dataConUnivTyVars data_con
775 arg_tys = ASSERT( isVanillaDataCon data_con ) dataConRepArgTys data_con
776 the_arg_id = assoc "MkId.mkDictSelId" (map idName (classSelIds clas) `zip` arg_ids) name
778 pred = mkClassPred clas (mkTyVarTys tyvars)
779 (dict_id:arg_ids) = mkTemplateLocals (mkPredTy pred : arg_tys)
781 rhs = mkLams tyvars (Lam dict_id rhs_body)
782 rhs_body | isNewTyCon tycon = unwrapNewTypeBody tycon (map mkTyVarTy tyvars) (Var dict_id)
783 | otherwise = Case (Var dict_id) dict_id (idType the_arg_id)
784 [(DataAlt data_con, arg_ids, Var the_arg_id)]
786 wrapNewTypeBody :: TyCon -> [Type] -> CoreExpr -> CoreExpr
787 -- The wrapper for the data constructor for a newtype looks like this:
788 -- newtype T a = MkT (a,Int)
789 -- MkT :: forall a. (a,Int) -> T a
790 -- MkT = /\a. \(x:(a,Int)). x `cast` CoT a
791 -- where CoT is the coercion TyCon assoicated with the newtype
793 -- The call (wrapNewTypeBody T [a] e) returns the
794 -- body of the wrapper, namely
797 -- If a coercion constructor is prodivided in the newtype, then we use
798 -- it, otherwise the wrap/unwrap are both no-ops
800 wrapNewTypeBody tycon args result_expr
801 | Just co_con <- newTyConCo tycon
802 = Cast result_expr (mkTyConApp co_con args)
806 unwrapNewTypeBody :: TyCon -> [Type] -> CoreExpr -> CoreExpr
807 unwrapNewTypeBody tycon args result_expr
808 | Just co_con <- newTyConCo tycon
809 = Cast result_expr (mkSymCoercion (mkTyConApp co_con args))
817 %************************************************************************
819 \subsection{Primitive operations
821 %************************************************************************
824 mkPrimOpId :: PrimOp -> Id
828 (tyvars,arg_tys,res_ty, arity, strict_sig) = primOpSig prim_op
829 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
830 name = mkWiredInName gHC_PRIM (primOpOcc prim_op)
831 (mkPrimOpIdUnique (primOpTag prim_op))
832 Nothing (AnId id) UserSyntax
833 id = mkGlobalId (PrimOpId prim_op) name ty info
836 `setSpecInfo` mkSpecInfo (primOpRules prim_op name)
838 `setAllStrictnessInfo` Just strict_sig
840 -- For each ccall we manufacture a separate CCallOpId, giving it
841 -- a fresh unique, a type that is correct for this particular ccall,
842 -- and a CCall structure that gives the correct details about calling
845 -- The *name* of this Id is a local name whose OccName gives the full
846 -- details of the ccall, type and all. This means that the interface
847 -- file reader can reconstruct a suitable Id
849 mkFCallId :: Unique -> ForeignCall -> Type -> Id
850 mkFCallId uniq fcall ty
851 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
852 -- A CCallOpId should have no free type variables;
853 -- when doing substitutions won't substitute over it
854 mkGlobalId (FCallId fcall) name ty info
856 occ_str = showSDoc (braces (ppr fcall <+> ppr ty))
857 -- The "occurrence name" of a ccall is the full info about the
858 -- ccall; it is encoded, but may have embedded spaces etc!
860 name = mkFCallName uniq occ_str
864 `setAllStrictnessInfo` Just strict_sig
866 (_, tau) = tcSplitForAllTys ty
867 (arg_tys, _) = tcSplitFunTys tau
868 arity = length arg_tys
869 strict_sig = mkStrictSig (mkTopDmdType (replicate arity evalDmd) TopRes)
873 %************************************************************************
875 \subsection{DictFuns and default methods}
877 %************************************************************************
879 Important notes about dict funs and default methods
880 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
881 Dict funs and default methods are *not* ImplicitIds. Their definition
882 involves user-written code, so we can't figure out their strictness etc
883 based on fixed info, as we can for constructors and record selectors (say).
885 We build them as LocalIds, but with External Names. This ensures that
886 they are taken to account by free-variable finding and dependency
887 analysis (e.g. CoreFVs.exprFreeVars).
889 Why shouldn't they be bound as GlobalIds? Because, in particular, if
890 they are globals, the specialiser floats dict uses above their defns,
891 which prevents good simplifications happening. Also the strictness
892 analyser treats a occurrence of a GlobalId as imported and assumes it
893 contains strictness in its IdInfo, which isn't true if the thing is
894 bound in the same module as the occurrence.
896 It's OK for dfuns to be LocalIds, because we form the instance-env to
897 pass on to the next module (md_insts) in CoreTidy, afer tidying
898 and globalising the top-level Ids.
900 BUT make sure they are *exported* LocalIds (mkExportedLocalId) so
901 that they aren't discarded by the occurrence analyser.
904 mkDefaultMethodId dm_name ty = mkExportedLocalId dm_name ty
906 mkDictFunId :: Name -- Name to use for the dict fun;
913 mkDictFunId dfun_name inst_tyvars dfun_theta clas inst_tys
914 = mkExportedLocalId dfun_name dfun_ty
916 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
918 {- 1 dec 99: disable the Mark Jones optimisation for the sake
919 of compatibility with Hugs.
920 See `types/InstEnv' for a discussion related to this.
922 (class_tyvars, sc_theta, _, _) = classBigSig clas
923 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
924 sc_theta' = substClasses (zipTopTvSubst class_tyvars inst_tys) sc_theta
925 dfun_theta = case inst_decl_theta of
926 [] -> [] -- If inst_decl_theta is empty, then we don't
927 -- want to have any dict arguments, so that we can
928 -- expose the constant methods.
930 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
931 -- Otherwise we pass the superclass dictionaries to
932 -- the dictionary function; the Mark Jones optimisation.
934 -- NOTE the "nub". I got caught by this one:
935 -- class Monad m => MonadT t m where ...
936 -- instance Monad m => MonadT (EnvT env) m where ...
937 -- Here, the inst_decl_theta has (Monad m); but so
938 -- does the sc_theta'!
940 -- NOTE the "not_const". I got caught by this one too:
941 -- class Foo a => Baz a b where ...
942 -- instance Wob b => Baz T b where..
943 -- Now sc_theta' has Foo T
948 %************************************************************************
950 \subsection{Un-definable}
952 %************************************************************************
954 These Ids can't be defined in Haskell. They could be defined in
955 unfoldings in the wired-in GHC.Prim interface file, but we'd have to
956 ensure that they were definitely, definitely inlined, because there is
957 no curried identifier for them. That's what mkCompulsoryUnfolding
958 does. If we had a way to get a compulsory unfolding from an interface
959 file, we could do that, but we don't right now.
961 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
962 just gets expanded into a type coercion wherever it occurs. Hence we
963 add it as a built-in Id with an unfolding here.
965 The type variables we use here are "open" type variables: this means
966 they can unify with both unlifted and lifted types. Hence we provide
967 another gun with which to shoot yourself in the foot.
970 mkWiredInIdName mod fs uniq id
971 = mkWiredInName mod (mkOccNameFS varName fs) uniq Nothing (AnId id) UserSyntax
973 unsafeCoerceName = mkWiredInIdName gHC_PRIM FSLIT("unsafeCoerce#") unsafeCoerceIdKey unsafeCoerceId
974 nullAddrName = mkWiredInIdName gHC_PRIM FSLIT("nullAddr#") nullAddrIdKey nullAddrId
975 seqName = mkWiredInIdName gHC_PRIM FSLIT("seq") seqIdKey seqId
976 realWorldName = mkWiredInIdName gHC_PRIM FSLIT("realWorld#") realWorldPrimIdKey realWorldPrimId
977 lazyIdName = mkWiredInIdName gHC_BASE FSLIT("lazy") lazyIdKey lazyId
979 errorName = mkWiredInIdName gHC_ERR FSLIT("error") errorIdKey eRROR_ID
980 recSelErrorName = mkWiredInIdName gHC_ERR FSLIT("recSelError") recSelErrorIdKey rEC_SEL_ERROR_ID
981 runtimeErrorName = mkWiredInIdName gHC_ERR FSLIT("runtimeError") runtimeErrorIdKey rUNTIME_ERROR_ID
982 irrefutPatErrorName = mkWiredInIdName gHC_ERR FSLIT("irrefutPatError") irrefutPatErrorIdKey iRREFUT_PAT_ERROR_ID
983 recConErrorName = mkWiredInIdName gHC_ERR FSLIT("recConError") recConErrorIdKey rEC_CON_ERROR_ID
984 patErrorName = mkWiredInIdName gHC_ERR FSLIT("patError") patErrorIdKey pAT_ERROR_ID
985 noMethodBindingErrorName = mkWiredInIdName gHC_ERR FSLIT("noMethodBindingError")
986 noMethodBindingErrorIdKey nO_METHOD_BINDING_ERROR_ID
987 nonExhaustiveGuardsErrorName
988 = mkWiredInIdName gHC_ERR FSLIT("nonExhaustiveGuardsError")
989 nonExhaustiveGuardsErrorIdKey nON_EXHAUSTIVE_GUARDS_ERROR_ID
993 -- unsafeCoerce# :: forall a b. a -> b
995 = pcMiscPrelId unsafeCoerceName ty info
997 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
1000 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
1001 (mkFunTy openAlphaTy openBetaTy)
1002 [x] = mkTemplateLocals [openAlphaTy]
1003 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
1004 -- Note (Coerce openBetaTy openAlphaTy) (Var x)
1005 Cast (Var x) (mkUnsafeCoercion openAlphaTy openBetaTy)
1007 -- nullAddr# :: Addr#
1008 -- The reason is is here is because we don't provide
1009 -- a way to write this literal in Haskell.
1011 = pcMiscPrelId nullAddrName addrPrimTy info
1013 info = noCafIdInfo `setUnfoldingInfo`
1014 mkCompulsoryUnfolding (Lit nullAddrLit)
1017 = pcMiscPrelId seqName ty info
1019 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
1022 ty = mkForAllTys [alphaTyVar,openBetaTyVar]
1023 (mkFunTy alphaTy (mkFunTy openBetaTy openBetaTy))
1024 [x,y] = mkTemplateLocals [alphaTy, openBetaTy]
1025 rhs = mkLams [alphaTyVar,openBetaTyVar,x,y] (Case (Var x) x openBetaTy [(DEFAULT, [], Var y)])
1027 -- lazy :: forall a?. a? -> a? (i.e. works for unboxed types too)
1028 -- Used to lazify pseq: pseq a b = a `seq` lazy b
1030 -- Also, no strictness: by being a built-in Id, all the info about lazyId comes from here,
1031 -- not from GHC.Base.hi. This is important, because the strictness
1032 -- analyser will spot it as strict!
1034 -- Also no unfolding in lazyId: it gets "inlined" by a HACK in the worker/wrapper pass
1035 -- (see WorkWrap.wwExpr)
1036 -- We could use inline phases to do this, but that would be vulnerable to changes in
1037 -- phase numbering....we must inline precisely after strictness analysis.
1039 = pcMiscPrelId lazyIdName ty info
1042 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy alphaTy)
1044 lazyIdUnfolding :: CoreExpr -- Used to expand 'lazyId' after strictness anal
1045 lazyIdUnfolding = mkLams [openAlphaTyVar,x] (Var x)
1047 [x] = mkTemplateLocals [openAlphaTy]
1050 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
1051 nasty as-is, change it back to a literal (@Literal@).
1053 voidArgId is a Local Id used simply as an argument in functions
1054 where we just want an arg to avoid having a thunk of unlifted type.
1056 x = \ void :: State# RealWorld -> (# p, q #)
1058 This comes up in strictness analysis
1061 realWorldPrimId -- :: State# RealWorld
1062 = pcMiscPrelId realWorldName realWorldStatePrimTy
1063 (noCafIdInfo `setUnfoldingInfo` evaldUnfolding)
1064 -- The evaldUnfolding makes it look that realWorld# is evaluated
1065 -- which in turn makes Simplify.interestingArg return True,
1066 -- which in turn makes INLINE things applied to realWorld# likely
1069 voidArgId -- :: State# RealWorld
1070 = mkSysLocal FSLIT("void") voidArgIdKey realWorldStatePrimTy
1074 %************************************************************************
1076 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
1078 %************************************************************************
1080 GHC randomly injects these into the code.
1082 @patError@ is just a version of @error@ for pattern-matching
1083 failures. It knows various ``codes'' which expand to longer
1084 strings---this saves space!
1086 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
1087 well shouldn't be yanked on, but if one is, then you will get a
1088 friendly message from @absentErr@ (rather than a totally random
1091 @parError@ is a special version of @error@ which the compiler does
1092 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
1093 templates, but we don't ever expect to generate code for it.
1097 :: Id -- Should be of type (forall a. Addr# -> a)
1098 -- where Addr# points to a UTF8 encoded string
1099 -> Type -- The type to instantiate 'a'
1100 -> String -- The string to print
1103 mkRuntimeErrorApp err_id res_ty err_msg
1104 = mkApps (Var err_id) [Type res_ty, err_string]
1106 err_string = Lit (mkStringLit err_msg)
1108 rEC_SEL_ERROR_ID = mkRuntimeErrorId recSelErrorName
1109 rUNTIME_ERROR_ID = mkRuntimeErrorId runtimeErrorName
1110 iRREFUT_PAT_ERROR_ID = mkRuntimeErrorId irrefutPatErrorName
1111 rEC_CON_ERROR_ID = mkRuntimeErrorId recConErrorName
1112 pAT_ERROR_ID = mkRuntimeErrorId patErrorName
1113 nO_METHOD_BINDING_ERROR_ID = mkRuntimeErrorId noMethodBindingErrorName
1114 nON_EXHAUSTIVE_GUARDS_ERROR_ID = mkRuntimeErrorId nonExhaustiveGuardsErrorName
1116 -- The runtime error Ids take a UTF8-encoded string as argument
1117 mkRuntimeErrorId name = pc_bottoming_Id name runtimeErrorTy
1118 runtimeErrorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTy addrPrimTy openAlphaTy)
1122 eRROR_ID = pc_bottoming_Id errorName errorTy
1125 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy] openAlphaTy)
1126 -- Notice the openAlphaTyVar. It says that "error" can be applied
1127 -- to unboxed as well as boxed types. This is OK because it never
1128 -- returns, so the return type is irrelevant.
1132 %************************************************************************
1134 \subsection{Utilities}
1136 %************************************************************************
1139 pcMiscPrelId :: Name -> Type -> IdInfo -> Id
1140 pcMiscPrelId name ty info
1141 = mkVanillaGlobal name ty info
1142 -- We lie and say the thing is imported; otherwise, we get into
1143 -- a mess with dependency analysis; e.g., core2stg may heave in
1144 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
1145 -- being compiled, then it's just a matter of luck if the definition
1146 -- will be in "the right place" to be in scope.
1148 pc_bottoming_Id name ty
1149 = pcMiscPrelId name ty bottoming_info
1151 bottoming_info = vanillaIdInfo `setAllStrictnessInfo` Just strict_sig
1152 -- Do *not* mark them as NoCafRefs, because they can indeed have
1153 -- CAF refs. For example, pAT_ERROR_ID calls GHC.Err.untangle,
1154 -- which has some CAFs
1155 -- In due course we may arrange that these error-y things are
1156 -- regarded by the GC as permanently live, in which case we
1157 -- can give them NoCaf info. As it is, any function that calls
1158 -- any pc_bottoming_Id will itself have CafRefs, which bloats
1161 strict_sig = mkStrictSig (mkTopDmdType [evalDmd] BotRes)
1162 -- These "bottom" out, no matter what their arguments
1164 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
1165 openAlphaTy = mkTyVarTy openAlphaTyVar
1166 openBetaTy = mkTyVarTy openBetaTyVar