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,
58 mkFunTys, mkFunTy, mkSigmaTy, tcSplitSigmaTy,
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 mkReboxingAlt uniqs' data_con (arg_prefix ++ arg_ids) rhs
558 (arg_prefix, arg_ids)
559 = (ex_tvs ++ co_tvs ++ dict_vs, field_vs)
561 -- get pattern binders with types appropriately instantiated
562 (ex_tvs, co_tvs, arg_vs) = dataConOrigInstPat uniqs data_con res_tys
563 n_vars = (length ex_tvs + length co_tvs + length arg_vs)
564 -- separate dicts vars and field vars so we can associate field lbls
565 (dict_vs, field_vs) = splitAt (length dc_theta) arg_vs
567 (_, pre_dc_theta, dc_arg_tys) = dataConSig data_con
568 dc_theta = filter (not . isEqPred) pre_dc_theta
570 arg_base' = arg_base + length dc_theta
572 unpack_base = arg_base' + length dc_arg_tys
574 uniq_list = map mkBuiltinUnique [unpack_base..]
576 Succeeded refinement = gadtRefine emptyRefinement ex_tvs co_tvs
577 (co_fn, _) = refineType refinement (idType the_arg_id)
579 rhs = perform_co co_fn (Var the_arg_id)
581 perform_co (ExprCoFn co) expr = Cast expr co
582 perform_co id_co expr = ASSERT(isIdCoercion id_co) expr
584 -- split the uniq_list into two
586 uniqs' = drop n_vars uniqs
588 the_arg_id = assoc "mkRecordSelId:mk_alt" (field_lbls `zip` arg_ids) field_label
589 field_lbls = dataConFieldLabels data_con
591 error_expr = mkRuntimeErrorApp rEC_SEL_ERROR_ID field_tau full_msg
592 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
594 -- unbox a product type...
595 -- we will recurse into newtypes, casting along the way, and unbox at the
596 -- first product data constructor we find. e.g.
598 -- data PairInt = PairInt Int Int
599 -- newtype S = MkS PairInt
602 -- If we have e = MkT (MkS (PairInt 0 1)) and some body expecting a list of
603 -- ids, we get (modulo int passing)
605 -- case (e `cast` (sym CoT)) `cast` (sym CoS) of
606 -- PairInt a b -> body [a,b]
608 -- The Ints passed around are just for creating fresh locals
609 unboxProduct :: Int -> CoreExpr -> Type -> (Int -> [Id] -> CoreExpr) -> Type -> CoreExpr
610 unboxProduct i arg arg_ty body res_ty
613 result = mkUnpackCase the_id arg arg_ty con_args boxing_con rhs
614 (tycon, tycon_args, boxing_con, tys) = deepSplitProductType "unboxProduct" arg_ty
615 ([the_id], i') = mkLocals i [arg_ty]
616 (con_args, i'') = mkLocals i' tys
617 rhs = body i'' con_args
619 mkUnpackCase :: Id -> CoreExpr -> Type -> [Id] -> DataCon -> CoreExpr -> CoreExpr
620 -- (mkUnpackCase x e args Con body)
622 -- case (e `cast` ...) of bndr { Con args -> body }
624 -- the type of the bndr passed in is irrelevent
625 mkUnpackCase bndr arg arg_ty unpk_args boxing_con body
626 = Case cast_arg (setIdType bndr bndr_ty) (exprType body) [(DataAlt boxing_con, unpk_args, body)]
628 (cast_arg, bndr_ty) = go (idType bndr) arg
630 | res@(tycon, tycon_args, _, _) <- splitProductType "mkUnpackCase" ty
631 , isNewTyCon tycon && not (isRecursiveTyCon tycon)
632 = go (newTyConInstRhs tycon tycon_args)
633 (unwrapNewTypeBody tycon tycon_args arg)
634 | otherwise = (arg, ty)
637 reboxProduct :: [Unique] -- uniques to create new local binders
638 -> Type -- type of product to box
639 -> ([Unique], -- remaining uniques
640 CoreExpr, -- boxed product
641 [Id]) -- Ids being boxed into product
644 (tycon, tycon_args, pack_con, con_arg_tys) = deepSplitProductType "reboxProduct" ty
646 us' = dropList con_arg_tys us
648 arg_ids = zipWith (mkSysLocal FSLIT("rb")) us con_arg_tys
650 bind_rhs = mkProductBox arg_ids ty
653 (us', bind_rhs, arg_ids)
655 mkProductBox :: [Id] -> Type -> CoreExpr
656 mkProductBox arg_ids ty
659 (tycon, tycon_args, pack_con, con_arg_tys) = splitProductType "mkProductBox" ty
662 | isNewTyCon tycon && not (isRecursiveTyCon tycon)
663 = wrap (mkProductBox arg_ids (newTyConInstRhs tycon tycon_args))
664 | otherwise = mkConApp pack_con (map Type tycon_args ++ map Var arg_ids)
666 wrap expr = wrapNewTypeBody tycon tycon_args expr
669 -- (mkReboxingAlt us con xs rhs) basically constructs the case
670 -- alternative (con, xs, rhs)
671 -- but it does the reboxing necessary to construct the *source*
672 -- arguments, xs, from the representation arguments ys.
674 -- data T = MkT !(Int,Int) Bool
676 -- mkReboxingAlt MkT [x,b] r
677 -- = (DataAlt MkT, [y::Int,z::Int,b], let x = (y,z) in r)
679 -- mkDataAlt should really be in DataCon, but it can't because
680 -- it manipulates CoreSyn.
683 :: [Unique] -- Uniques for the new Ids
685 -> [Var] -- Source-level args, including existential dicts
689 mkReboxingAlt us con args rhs
690 | not (any isMarkedUnboxed stricts)
691 = (DataAlt con, args, rhs)
695 (binds, args') = go args stricts us
697 (DataAlt con, args', mkLets binds rhs)
700 stricts = dataConExStricts con ++ dataConStrictMarks con
702 go [] stricts us = ([], [])
704 -- Type variable case
705 go (arg:args) stricts us
707 = let (binds, args') = go args stricts us
708 in (binds, arg:args')
710 -- Term variable case
711 go (arg:args) (str:stricts) us
712 | isMarkedUnboxed str
714 let (binds, unpacked_args') = go args stricts us'
715 (us', bind_rhs, unpacked_args) = reboxProduct us (idType arg)
717 (NonRec arg bind_rhs : binds, unpacked_args ++ unpacked_args')
719 = let (binds, args') = go args stricts us
720 in (binds, arg:args')
724 %************************************************************************
726 \subsection{Dictionary selectors}
728 %************************************************************************
730 Selecting a field for a dictionary. If there is just one field, then
731 there's nothing to do.
733 Dictionary selectors may get nested forall-types. Thus:
736 op :: forall b. Ord b => a -> b -> b
738 Then the top-level type for op is
740 op :: forall a. Foo a =>
744 This is unlike ordinary record selectors, which have all the for-alls
745 at the outside. When dealing with classes it's very convenient to
746 recover the original type signature from the class op selector.
749 mkDictSelId :: Name -> Class -> Id
750 mkDictSelId name clas
751 = mkGlobalId (ClassOpId clas) name sel_ty info
753 sel_ty = mkForAllTys tyvars (mkFunTy (idType dict_id) (idType the_arg_id))
754 -- We can't just say (exprType rhs), because that would give a type
756 -- for a single-op class (after all, the selector is the identity)
757 -- But it's type must expose the representation of the dictionary
758 -- to gat (say) C a -> (a -> a)
762 `setUnfoldingInfo` mkTopUnfolding rhs
763 `setAllStrictnessInfo` Just strict_sig
765 -- We no longer use 'must-inline' on record selectors. They'll
766 -- inline like crazy if they scrutinise a constructor
768 -- The strictness signature is of the form U(AAAVAAAA) -> T
769 -- where the V depends on which item we are selecting
770 -- It's worth giving one, so that absence info etc is generated
771 -- even if the selector isn't inlined
772 strict_sig = mkStrictSig (mkTopDmdType [arg_dmd] TopRes)
773 arg_dmd | isNewTyCon tycon = evalDmd
774 | otherwise = Eval (Prod [ if the_arg_id == id then evalDmd else Abs
777 tycon = classTyCon clas
778 [data_con] = tyConDataCons tycon
779 tyvars = dataConUnivTyVars data_con
780 arg_tys = ASSERT( isVanillaDataCon data_con ) dataConRepArgTys data_con
781 the_arg_id = assoc "MkId.mkDictSelId" (map idName (classSelIds clas) `zip` arg_ids) name
783 pred = mkClassPred clas (mkTyVarTys tyvars)
784 (dict_id:arg_ids) = mkTemplateLocals (mkPredTy pred : arg_tys)
786 rhs = mkLams tyvars (Lam dict_id rhs_body)
787 rhs_body | isNewTyCon tycon = unwrapNewTypeBody tycon (map mkTyVarTy tyvars) (Var dict_id)
788 | otherwise = Case (Var dict_id) dict_id (idType the_arg_id)
789 [(DataAlt data_con, arg_ids, Var the_arg_id)]
791 wrapNewTypeBody :: TyCon -> [Type] -> CoreExpr -> CoreExpr
792 -- The wrapper for the data constructor for a newtype looks like this:
793 -- newtype T a = MkT (a,Int)
794 -- MkT :: forall a. (a,Int) -> T a
795 -- MkT = /\a. \(x:(a,Int)). x `cast` CoT a
796 -- where CoT is the coercion TyCon assoicated with the newtype
798 -- The call (wrapNewTypeBody T [a] e) returns the
799 -- body of the wrapper, namely
802 -- If a coercion constructor is prodivided in the newtype, then we use
803 -- it, otherwise the wrap/unwrap are both no-ops
805 wrapNewTypeBody tycon args result_expr
806 | Just co_con <- newTyConCo tycon
807 = Cast result_expr (mkTyConApp co_con args)
811 unwrapNewTypeBody :: TyCon -> [Type] -> CoreExpr -> CoreExpr
812 unwrapNewTypeBody tycon args result_expr
813 | Just co_con <- newTyConCo tycon
814 = Cast result_expr (mkSymCoercion (mkTyConApp co_con args))
822 %************************************************************************
824 \subsection{Primitive operations
826 %************************************************************************
829 mkPrimOpId :: PrimOp -> Id
833 (tyvars,arg_tys,res_ty, arity, strict_sig) = primOpSig prim_op
834 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
835 name = mkWiredInName gHC_PRIM (primOpOcc prim_op)
836 (mkPrimOpIdUnique (primOpTag prim_op))
837 Nothing (AnId id) UserSyntax
838 id = mkGlobalId (PrimOpId prim_op) name ty info
841 `setSpecInfo` mkSpecInfo (primOpRules prim_op name)
843 `setAllStrictnessInfo` Just strict_sig
845 -- For each ccall we manufacture a separate CCallOpId, giving it
846 -- a fresh unique, a type that is correct for this particular ccall,
847 -- and a CCall structure that gives the correct details about calling
850 -- The *name* of this Id is a local name whose OccName gives the full
851 -- details of the ccall, type and all. This means that the interface
852 -- file reader can reconstruct a suitable Id
854 mkFCallId :: Unique -> ForeignCall -> Type -> Id
855 mkFCallId uniq fcall ty
856 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
857 -- A CCallOpId should have no free type variables;
858 -- when doing substitutions won't substitute over it
859 mkGlobalId (FCallId fcall) name ty info
861 occ_str = showSDoc (braces (ppr fcall <+> ppr ty))
862 -- The "occurrence name" of a ccall is the full info about the
863 -- ccall; it is encoded, but may have embedded spaces etc!
865 name = mkFCallName uniq occ_str
869 `setAllStrictnessInfo` Just strict_sig
871 (_, tau) = tcSplitForAllTys ty
872 (arg_tys, _) = tcSplitFunTys tau
873 arity = length arg_tys
874 strict_sig = mkStrictSig (mkTopDmdType (replicate arity evalDmd) TopRes)
878 %************************************************************************
880 \subsection{DictFuns and default methods}
882 %************************************************************************
884 Important notes about dict funs and default methods
885 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
886 Dict funs and default methods are *not* ImplicitIds. Their definition
887 involves user-written code, so we can't figure out their strictness etc
888 based on fixed info, as we can for constructors and record selectors (say).
890 We build them as LocalIds, but with External Names. This ensures that
891 they are taken to account by free-variable finding and dependency
892 analysis (e.g. CoreFVs.exprFreeVars).
894 Why shouldn't they be bound as GlobalIds? Because, in particular, if
895 they are globals, the specialiser floats dict uses above their defns,
896 which prevents good simplifications happening. Also the strictness
897 analyser treats a occurrence of a GlobalId as imported and assumes it
898 contains strictness in its IdInfo, which isn't true if the thing is
899 bound in the same module as the occurrence.
901 It's OK for dfuns to be LocalIds, because we form the instance-env to
902 pass on to the next module (md_insts) in CoreTidy, afer tidying
903 and globalising the top-level Ids.
905 BUT make sure they are *exported* LocalIds (mkExportedLocalId) so
906 that they aren't discarded by the occurrence analyser.
909 mkDefaultMethodId dm_name ty = mkExportedLocalId dm_name ty
911 mkDictFunId :: Name -- Name to use for the dict fun;
918 mkDictFunId dfun_name inst_tyvars dfun_theta clas inst_tys
919 = mkExportedLocalId dfun_name dfun_ty
921 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
923 {- 1 dec 99: disable the Mark Jones optimisation for the sake
924 of compatibility with Hugs.
925 See `types/InstEnv' for a discussion related to this.
927 (class_tyvars, sc_theta, _, _) = classBigSig clas
928 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
929 sc_theta' = substClasses (zipTopTvSubst class_tyvars inst_tys) sc_theta
930 dfun_theta = case inst_decl_theta of
931 [] -> [] -- If inst_decl_theta is empty, then we don't
932 -- want to have any dict arguments, so that we can
933 -- expose the constant methods.
935 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
936 -- Otherwise we pass the superclass dictionaries to
937 -- the dictionary function; the Mark Jones optimisation.
939 -- NOTE the "nub". I got caught by this one:
940 -- class Monad m => MonadT t m where ...
941 -- instance Monad m => MonadT (EnvT env) m where ...
942 -- Here, the inst_decl_theta has (Monad m); but so
943 -- does the sc_theta'!
945 -- NOTE the "not_const". I got caught by this one too:
946 -- class Foo a => Baz a b where ...
947 -- instance Wob b => Baz T b where..
948 -- Now sc_theta' has Foo T
953 %************************************************************************
955 \subsection{Un-definable}
957 %************************************************************************
959 These Ids can't be defined in Haskell. They could be defined in
960 unfoldings in the wired-in GHC.Prim interface file, but we'd have to
961 ensure that they were definitely, definitely inlined, because there is
962 no curried identifier for them. That's what mkCompulsoryUnfolding
963 does. If we had a way to get a compulsory unfolding from an interface
964 file, we could do that, but we don't right now.
966 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
967 just gets expanded into a type coercion wherever it occurs. Hence we
968 add it as a built-in Id with an unfolding here.
970 The type variables we use here are "open" type variables: this means
971 they can unify with both unlifted and lifted types. Hence we provide
972 another gun with which to shoot yourself in the foot.
975 mkWiredInIdName mod fs uniq id
976 = mkWiredInName mod (mkOccNameFS varName fs) uniq Nothing (AnId id) UserSyntax
978 unsafeCoerceName = mkWiredInIdName gHC_PRIM FSLIT("unsafeCoerce#") unsafeCoerceIdKey unsafeCoerceId
979 nullAddrName = mkWiredInIdName gHC_PRIM FSLIT("nullAddr#") nullAddrIdKey nullAddrId
980 seqName = mkWiredInIdName gHC_PRIM FSLIT("seq") seqIdKey seqId
981 realWorldName = mkWiredInIdName gHC_PRIM FSLIT("realWorld#") realWorldPrimIdKey realWorldPrimId
982 lazyIdName = mkWiredInIdName gHC_BASE FSLIT("lazy") lazyIdKey lazyId
984 errorName = mkWiredInIdName gHC_ERR FSLIT("error") errorIdKey eRROR_ID
985 recSelErrorName = mkWiredInIdName gHC_ERR FSLIT("recSelError") recSelErrorIdKey rEC_SEL_ERROR_ID
986 runtimeErrorName = mkWiredInIdName gHC_ERR FSLIT("runtimeError") runtimeErrorIdKey rUNTIME_ERROR_ID
987 irrefutPatErrorName = mkWiredInIdName gHC_ERR FSLIT("irrefutPatError") irrefutPatErrorIdKey iRREFUT_PAT_ERROR_ID
988 recConErrorName = mkWiredInIdName gHC_ERR FSLIT("recConError") recConErrorIdKey rEC_CON_ERROR_ID
989 patErrorName = mkWiredInIdName gHC_ERR FSLIT("patError") patErrorIdKey pAT_ERROR_ID
990 noMethodBindingErrorName = mkWiredInIdName gHC_ERR FSLIT("noMethodBindingError")
991 noMethodBindingErrorIdKey nO_METHOD_BINDING_ERROR_ID
992 nonExhaustiveGuardsErrorName
993 = mkWiredInIdName gHC_ERR FSLIT("nonExhaustiveGuardsError")
994 nonExhaustiveGuardsErrorIdKey nON_EXHAUSTIVE_GUARDS_ERROR_ID
998 -- unsafeCoerce# :: forall a b. a -> b
1000 = pcMiscPrelId unsafeCoerceName ty info
1002 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
1005 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
1006 (mkFunTy openAlphaTy openBetaTy)
1007 [x] = mkTemplateLocals [openAlphaTy]
1008 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
1009 -- Note (Coerce openBetaTy openAlphaTy) (Var x)
1010 Cast (Var x) (mkUnsafeCoercion openAlphaTy openBetaTy)
1012 -- nullAddr# :: Addr#
1013 -- The reason is is here is because we don't provide
1014 -- a way to write this literal in Haskell.
1016 = pcMiscPrelId nullAddrName addrPrimTy info
1018 info = noCafIdInfo `setUnfoldingInfo`
1019 mkCompulsoryUnfolding (Lit nullAddrLit)
1022 = pcMiscPrelId seqName ty info
1024 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
1027 ty = mkForAllTys [alphaTyVar,openBetaTyVar]
1028 (mkFunTy alphaTy (mkFunTy openBetaTy openBetaTy))
1029 [x,y] = mkTemplateLocals [alphaTy, openBetaTy]
1030 rhs = mkLams [alphaTyVar,openBetaTyVar,x,y] (Case (Var x) x openBetaTy [(DEFAULT, [], Var y)])
1032 -- lazy :: forall a?. a? -> a? (i.e. works for unboxed types too)
1033 -- Used to lazify pseq: pseq a b = a `seq` lazy b
1035 -- Also, no strictness: by being a built-in Id, all the info about lazyId comes from here,
1036 -- not from GHC.Base.hi. This is important, because the strictness
1037 -- analyser will spot it as strict!
1039 -- Also no unfolding in lazyId: it gets "inlined" by a HACK in the worker/wrapper pass
1040 -- (see WorkWrap.wwExpr)
1041 -- We could use inline phases to do this, but that would be vulnerable to changes in
1042 -- phase numbering....we must inline precisely after strictness analysis.
1044 = pcMiscPrelId lazyIdName ty info
1047 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy alphaTy)
1049 lazyIdUnfolding :: CoreExpr -- Used to expand 'lazyId' after strictness anal
1050 lazyIdUnfolding = mkLams [openAlphaTyVar,x] (Var x)
1052 [x] = mkTemplateLocals [openAlphaTy]
1055 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
1056 nasty as-is, change it back to a literal (@Literal@).
1058 voidArgId is a Local Id used simply as an argument in functions
1059 where we just want an arg to avoid having a thunk of unlifted type.
1061 x = \ void :: State# RealWorld -> (# p, q #)
1063 This comes up in strictness analysis
1066 realWorldPrimId -- :: State# RealWorld
1067 = pcMiscPrelId realWorldName realWorldStatePrimTy
1068 (noCafIdInfo `setUnfoldingInfo` evaldUnfolding)
1069 -- The evaldUnfolding makes it look that realWorld# is evaluated
1070 -- which in turn makes Simplify.interestingArg return True,
1071 -- which in turn makes INLINE things applied to realWorld# likely
1074 voidArgId -- :: State# RealWorld
1075 = mkSysLocal FSLIT("void") voidArgIdKey realWorldStatePrimTy
1079 %************************************************************************
1081 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
1083 %************************************************************************
1085 GHC randomly injects these into the code.
1087 @patError@ is just a version of @error@ for pattern-matching
1088 failures. It knows various ``codes'' which expand to longer
1089 strings---this saves space!
1091 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
1092 well shouldn't be yanked on, but if one is, then you will get a
1093 friendly message from @absentErr@ (rather than a totally random
1096 @parError@ is a special version of @error@ which the compiler does
1097 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
1098 templates, but we don't ever expect to generate code for it.
1102 :: Id -- Should be of type (forall a. Addr# -> a)
1103 -- where Addr# points to a UTF8 encoded string
1104 -> Type -- The type to instantiate 'a'
1105 -> String -- The string to print
1108 mkRuntimeErrorApp err_id res_ty err_msg
1109 = mkApps (Var err_id) [Type res_ty, err_string]
1111 err_string = Lit (mkStringLit err_msg)
1113 rEC_SEL_ERROR_ID = mkRuntimeErrorId recSelErrorName
1114 rUNTIME_ERROR_ID = mkRuntimeErrorId runtimeErrorName
1115 iRREFUT_PAT_ERROR_ID = mkRuntimeErrorId irrefutPatErrorName
1116 rEC_CON_ERROR_ID = mkRuntimeErrorId recConErrorName
1117 pAT_ERROR_ID = mkRuntimeErrorId patErrorName
1118 nO_METHOD_BINDING_ERROR_ID = mkRuntimeErrorId noMethodBindingErrorName
1119 nON_EXHAUSTIVE_GUARDS_ERROR_ID = mkRuntimeErrorId nonExhaustiveGuardsErrorName
1121 -- The runtime error Ids take a UTF8-encoded string as argument
1122 mkRuntimeErrorId name = pc_bottoming_Id name runtimeErrorTy
1123 runtimeErrorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTy addrPrimTy openAlphaTy)
1127 eRROR_ID = pc_bottoming_Id errorName errorTy
1130 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy] openAlphaTy)
1131 -- Notice the openAlphaTyVar. It says that "error" can be applied
1132 -- to unboxed as well as boxed types. This is OK because it never
1133 -- returns, so the return type is irrelevant.
1137 %************************************************************************
1139 \subsection{Utilities}
1141 %************************************************************************
1144 pcMiscPrelId :: Name -> Type -> IdInfo -> Id
1145 pcMiscPrelId name ty info
1146 = mkVanillaGlobal name ty info
1147 -- We lie and say the thing is imported; otherwise, we get into
1148 -- a mess with dependency analysis; e.g., core2stg may heave in
1149 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
1150 -- being compiled, then it's just a matter of luck if the definition
1151 -- will be in "the right place" to be in scope.
1153 pc_bottoming_Id name ty
1154 = pcMiscPrelId name ty bottoming_info
1156 bottoming_info = vanillaIdInfo `setAllStrictnessInfo` Just strict_sig
1157 -- Do *not* mark them as NoCafRefs, because they can indeed have
1158 -- CAF refs. For example, pAT_ERROR_ID calls GHC.Err.untangle,
1159 -- which has some CAFs
1160 -- In due course we may arrange that these error-y things are
1161 -- regarded by the GC as permanently live, in which case we
1162 -- can give them NoCaf info. As it is, any function that calls
1163 -- any pc_bottoming_Id will itself have CafRefs, which bloats
1166 strict_sig = mkStrictSig (mkTopDmdType [evalDmd] BotRes)
1167 -- These "bottom" out, no matter what their arguments
1169 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
1170 openAlphaTy = mkTyVarTy openAlphaTyVar
1171 openBetaTy = mkTyVarTy openBetaTyVar