2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section{Tidying up Core}
7 module TidyPgm( mkBootModDetailsDs, mkBootModDetailsTc,
8 tidyProgram, globaliseAndTidyId ) where
10 #include "HsVersions.h"
22 import Class ( classSelIds )
45 import FastBool hiding ( fastOr )
47 import Data.List ( partition )
48 import Data.Maybe ( isJust )
49 import Data.IORef ( IORef, readIORef, writeIORef )
53 Constructing the TypeEnv, Instances, Rules from which the ModIface is
54 constructed, and which goes on to subsequent modules in --make mode.
56 Most of the interface file is obtained simply by serialising the
57 TypeEnv. One important consequence is that if the *interface file*
58 has pragma info if and only if the final TypeEnv does. This is not so
59 important for *this* module, but it's essential for ghc --make:
60 subsequent compilations must not see (e.g.) the arity if the interface
61 file does not contain arity If they do, they'll exploit the arity;
62 then the arity might change, but the iface file doesn't change =>
63 recompilation does not happen => disaster.
65 For data types, the final TypeEnv will have a TyThing for the TyCon,
66 plus one for each DataCon; the interface file will contain just one
67 data type declaration, but it is de-serialised back into a collection
70 %************************************************************************
74 %************************************************************************
77 Plan A: mkBootModDetails: omit pragmas, make interfaces small
78 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
81 * Drop all WiredIn things from the TypeEnv
82 (we never want them in interface files)
84 * Retain all TyCons and Classes in the TypeEnv, to avoid
85 having to find which ones are mentioned in the
88 * Trim off the constructors of non-exported TyCons, both
89 from the TyCon and from the TypeEnv
91 * Drop non-exported Ids from the TypeEnv
93 * Tidy the types of the DFunIds of Instances,
94 make them into GlobalIds, (they already have External Names)
95 and add them to the TypeEnv
97 * Tidy the types of the (exported) Ids in the TypeEnv,
98 make them into GlobalIds (they already have External Names)
100 * Drop rules altogether
102 * Tidy the bindings, to ensure that the Caf and Arity
103 information is correct for each top-level binder; the
104 code generator needs it. And to ensure that local names have
105 distinct OccNames in case of object-file splitting
108 -- This is Plan A: make a small type env when typechecking only,
109 -- or when compiling a hs-boot file, or simply when not using -O
111 -- We don't look at the bindings at all -- there aren't any
114 mkBootModDetailsTc :: HscEnv -> TcGblEnv -> IO ModDetails
115 mkBootModDetailsTc hsc_env
116 TcGblEnv{ tcg_exports = exports,
117 tcg_type_env = type_env,
119 tcg_fam_insts = fam_insts
121 = mkBootModDetails hsc_env exports type_env insts fam_insts
123 mkBootModDetailsDs :: HscEnv -> ModGuts -> IO ModDetails
124 mkBootModDetailsDs hsc_env
125 ModGuts{ mg_exports = exports,
128 mg_fam_insts = fam_insts
130 = mkBootModDetails hsc_env exports type_env insts fam_insts
132 mkBootModDetails :: HscEnv -> [AvailInfo] -> NameEnv TyThing
133 -> [Instance] -> [FamInstEnv.FamInst] -> IO ModDetails
134 mkBootModDetails hsc_env exports type_env insts fam_insts
135 = do { let dflags = hsc_dflags hsc_env
136 ; showPass dflags "Tidy [hoot] type env"
138 ; let { insts' = tidyInstances globaliseAndTidyId insts
139 ; dfun_ids = map instanceDFunId insts'
140 ; type_env1 = tidyBootTypeEnv (availsToNameSet exports) type_env
141 ; type_env' = extendTypeEnvWithIds type_env1 dfun_ids
143 ; return (ModDetails { md_types = type_env'
145 , md_fam_insts = fam_insts
148 , md_exports = exports
149 , md_vect_info = noVectInfo
154 tidyBootTypeEnv :: NameSet -> TypeEnv -> TypeEnv
155 tidyBootTypeEnv exports type_env
156 = tidyTypeEnv True False exports type_env final_ids
158 -- Find the LocalIds in the type env that are exported
159 -- Make them into GlobalIds, and tidy their types
161 -- It's very important to remove the non-exported ones
162 -- because we don't tidy the OccNames, and if we don't remove
163 -- the non-exported ones we'll get many things with the
164 -- same name in the interface file, giving chaos.
165 final_ids = [ globaliseAndTidyId id
166 | id <- typeEnvIds type_env
170 -- default methods have their export flag set, but everything
171 -- else doesn't (yet), because this is pre-desugaring, so we
173 keep_it id = isExportedId id || idName id `elemNameSet` exports
177 globaliseAndTidyId :: Id -> Id
178 -- Takes an LocalId with an External Name,
179 -- makes it into a GlobalId
180 -- * unchanged Name (might be Internal or External)
181 -- * unchanged details
182 -- * VanillaIdInfo (makes a conservative assumption about Caf-hood)
183 globaliseAndTidyId id
184 = Id.setIdType (globaliseId id) tidy_type
186 tidy_type = tidyTopType (idType id)
190 %************************************************************************
192 Plan B: tidy bindings, make TypeEnv full of IdInfo
194 %************************************************************************
196 Plan B: include pragmas, make interfaces
197 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
198 * Figure out which Ids are externally visible
200 * Tidy the bindings, externalising appropriate Ids
202 * Drop all Ids from the TypeEnv, and add all the External Ids from
203 the bindings. (This adds their IdInfo to the TypeEnv; and adds
204 floated-out Ids that weren't even in the TypeEnv before.)
206 Step 1: Figure out external Ids
207 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
208 First we figure out which Ids are "external" Ids. An
209 "external" Id is one that is visible from outside the compilation
211 a) the user exported ones
212 b) ones mentioned in the unfoldings, workers,
213 or rules of externally-visible ones
214 This exercise takes a sweep of the bindings bottom to top. Actually,
215 in Step 2 we're also going to need to know which Ids should be
216 exported with their unfoldings, so we produce not an IdSet but an
220 Step 2: Tidy the program
221 ~~~~~~~~~~~~~~~~~~~~~~~~
222 Next we traverse the bindings top to bottom. For each *top-level*
225 1. Make it into a GlobalId; its IdDetails becomes VanillaGlobal,
226 reflecting the fact that from now on we regard it as a global,
229 2. Give it a system-wide Unique.
230 [Even non-exported things need system-wide Uniques because the
231 byte-code generator builds a single Name->BCO symbol table.]
233 We use the NameCache kept in the HscEnv as the
234 source of such system-wide uniques.
236 For external Ids, use the original-name cache in the NameCache
237 to ensure that the unique assigned is the same as the Id had
238 in any previous compilation run.
240 3. If it's an external Id, make it have a External Name, otherwise
241 make it have an Internal Name.
242 This is used by the code generator to decide whether
243 to make the label externally visible
245 4. Give external Ids a "tidy" OccName. This means
246 we can print them in interface files without confusing
247 "x" (unique 5) with "x" (unique 10).
249 5. Give it its UTTERLY FINAL IdInfo; in ptic,
250 * its unfolding, if it should have one
252 * its arity, computed from the number of visible lambdas
254 * its CAF info, computed from what is free in its RHS
257 Finally, substitute these new top-level binders consistently
258 throughout, including in unfoldings. We also tidy binders in
259 RHSs, so that they print nicely in interfaces.
262 tidyProgram :: HscEnv -> ModGuts -> IO (CgGuts, ModDetails)
263 tidyProgram hsc_env (ModGuts { mg_module = mod, mg_exports = exports,
265 mg_insts = insts, mg_fam_insts = fam_insts,
267 mg_rules = imp_rules,
268 mg_vect_info = vect_info,
269 mg_dir_imps = dir_imps,
272 mg_foreign = foreign_stubs,
273 mg_hpc_info = hpc_info,
274 mg_modBreaks = modBreaks })
276 = do { let dflags = hsc_dflags hsc_env
277 ; showPass dflags "Tidy Core"
279 ; let { omit_prags = dopt Opt_OmitInterfacePragmas dflags
280 ; th = dopt Opt_TemplateHaskell dflags
281 ; ext_ids = findExternalIds omit_prags binds
284 | otherwise = findExternalRules binds imp_rules ext_ids
285 -- findExternalRules filters imp_rules to avoid binders that
286 -- aren't externally visible; but the externally-visible binders
287 -- are computed (by findExternalIds) assuming that all orphan
288 -- rules are exported (they get their Exported flag set in the desugarer)
289 -- So in fact we may export more than we need.
290 -- (It's a sort of mutual recursion.)
293 ; (tidy_env, tidy_binds) <- tidyTopBinds hsc_env mod type_env ext_ids
296 ; let { export_set = availsToNameSet exports
297 ; final_ids = [ id | id <- bindersOfBinds tidy_binds,
298 isExternalName (idName id)]
299 ; tidy_type_env = tidyTypeEnv omit_prags th export_set
301 ; tidy_insts = tidyInstances (lookup_dfun tidy_type_env) insts
302 -- A DFunId will have a binding in tidy_binds, and so
303 -- will now be in final_env, replete with IdInfo
304 -- Its name will be unchanged since it was born, but
305 -- we want Global, IdInfo-rich (or not) DFunId in the
308 ; tidy_rules = tidyRules tidy_env ext_rules
309 -- You might worry that the tidy_env contains IdInfo-rich stuff
310 -- and indeed it does, but if omit_prags is on, ext_rules is
313 -- See Note [Injecting implicit bindings]
314 ; implicit_binds = getImplicitBinds type_env
315 ; all_tidy_binds = implicit_binds ++ tidy_binds
317 ; alg_tycons = filter isAlgTyCon (typeEnvTyCons type_env)
320 ; endPass dflags "Tidy Core" Opt_D_dump_simpl all_tidy_binds
321 ; dumpIfSet_core dflags Opt_D_dump_simpl
323 (pprRules tidy_rules)
325 ; let dir_imp_mods = moduleEnvKeys dir_imps
327 ; return (CgGuts { cg_module = mod,
328 cg_tycons = alg_tycons,
329 cg_binds = all_tidy_binds,
330 cg_dir_imps = dir_imp_mods,
331 cg_foreign = foreign_stubs,
332 cg_dep_pkgs = dep_pkgs deps,
333 cg_hpc_info = hpc_info,
334 cg_modBreaks = modBreaks },
336 ModDetails { md_types = tidy_type_env,
337 md_rules = tidy_rules,
338 md_insts = tidy_insts,
339 md_fam_insts = fam_insts,
340 md_exports = exports,
341 md_anns = anns, -- are already tidy
342 md_vect_info = vect_info --
346 lookup_dfun :: TypeEnv -> Var -> Id
347 lookup_dfun type_env dfun_id
348 = case lookupTypeEnv type_env (idName dfun_id) of
349 Just (AnId dfun_id') -> dfun_id'
350 _other -> pprPanic "lookup_dfun" (ppr dfun_id)
352 --------------------------
353 tidyTypeEnv :: Bool -- Compiling without -O, so omit prags
354 -> Bool -- Template Haskell is on
355 -> NameSet -> TypeEnv -> [Id] -> TypeEnv
357 -- The competed type environment is gotten from
358 -- Dropping any wired-in things, and then
359 -- a) keeping the types and classes
360 -- b) removing all Ids,
361 -- c) adding Ids with correct IdInfo, including unfoldings,
362 -- gotten from the bindings
363 -- From (c) we keep only those Ids with External names;
364 -- the CoreTidy pass makes sure these are all and only
365 -- the externally-accessible ones
366 -- This truncates the type environment to include only the
367 -- exported Ids and things needed from them, which saves space
369 tidyTypeEnv omit_prags th exports type_env final_ids
370 = let type_env1 = filterNameEnv keep_it type_env
371 type_env2 = extendTypeEnvWithIds type_env1 final_ids
372 type_env3 | omit_prags = mapNameEnv (trimThing th exports) type_env2
373 | otherwise = type_env2
377 -- We keep GlobalIds, because they won't appear
378 -- in the bindings from which final_ids are derived!
379 -- (The bindings bind LocalIds.)
380 keep_it thing | isWiredInThing thing = False
381 keep_it (AnId id) = isGlobalId id -- Keep GlobalIds (e.g. class ops)
382 keep_it _other = True -- Keep all TyCons, DataCons, and Classes
384 --------------------------
385 isWiredInThing :: TyThing -> Bool
386 isWiredInThing thing = isWiredInName (getName thing)
388 --------------------------
389 trimThing :: Bool -> NameSet -> TyThing -> TyThing
390 -- Trim off inessentials, for boot files and no -O
391 trimThing th exports (ATyCon tc)
392 | not th && not (mustExposeTyCon exports tc)
393 = ATyCon (makeTyConAbstract tc) -- Note [Trimming and Template Haskell]
395 trimThing _th _exports (AnId id)
396 | not (isImplicitId id)
397 = AnId (id `setIdInfo` vanillaIdInfo)
399 trimThing _th _exports other_thing
403 {- Note [Trimming and Template Haskell]
404 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
405 Consider (Trac #2386) this
406 module M(T, makeOne) where
408 makeOne = [| Yay "Yep" |]
409 Notice that T is exported abstractly, but makeOne effectively exports it too!
410 A module that splices in $(makeOne) will then look for a declartion of Yay,
411 so it'd better be there. Hence, brutally but simply, we switch off type
412 constructor trimming if TH is enabled in this module. -}
415 mustExposeTyCon :: NameSet -- Exports
416 -> TyCon -- The tycon
417 -> Bool -- Can its rep be hidden?
418 -- We are compiling without -O, and thus trying to write as little as
419 -- possible into the interface file. But we must expose the details of
420 -- any data types whose constructors or fields are exported
421 mustExposeTyCon exports tc
422 | not (isAlgTyCon tc) -- Synonyms
424 | isEnumerationTyCon tc -- For an enumeration, exposing the constructors
425 = True -- won't lead to the need for further exposure
426 -- (This includes data types with no constructors.)
427 | isOpenTyCon tc -- Open type family
430 | otherwise -- Newtype, datatype
431 = any exported_con (tyConDataCons tc)
432 -- Expose rep if any datacon or field is exported
434 || (isNewTyCon tc && isFFITy (snd (newTyConRhs tc)))
435 -- Expose the rep for newtypes if the rep is an FFI type.
436 -- For a very annoying reason. 'Foreign import' is meant to
437 -- be able to look through newtypes transparently, but it
438 -- can only do that if it can "see" the newtype representation
440 exported_con con = any (`elemNameSet` exports)
441 (dataConName con : dataConFieldLabels con)
443 tidyInstances :: (DFunId -> DFunId) -> [Instance] -> [Instance]
444 tidyInstances tidy_dfun ispecs
447 tidy ispec = setInstanceDFunId ispec $
448 tidy_dfun (instanceDFunId ispec)
452 %************************************************************************
456 %************************************************************************
458 Note [Injecting implicit bindings]
459 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
460 We inject the implict bindings right at the end, in CoreTidy.
461 Some of these bindings, notably record selectors, are not
462 constructed in an optimised form. E.g. record selector for
463 data T = MkT { x :: {-# UNPACK #-} !Int }
464 Then the unfolding looks like
465 x = \t. case t of MkT x1 -> let x = I# x1 in x
466 This generates bad code unless it's first simplified a bit. That is
467 why CoreUnfold.mkImplicitUnfolding uses simleExprOpt to do a bit of
468 optimisation first. (Only matters when the selector is used curried;
469 eg map x ys.) See Trac #2070.
471 At one time I tried injecting the implicit bindings *early*, at the
472 beginning of SimplCore. But that gave rise to real difficulty,
473 becuase GlobalIds are supposed to have *fixed* IdInfo, but the
474 simplifier and other core-to-core passes mess with IdInfo all the
475 time. The straw that broke the camels back was when a class selector
476 got the wrong arity -- ie the simplifier gave it arity 2, whereas
477 importing modules were expecting it to have arity 1 (Trac #2844).
478 It's much safer just to inject them right at the end, after tidying.
482 getImplicitBinds :: TypeEnv -> [CoreBind]
483 getImplicitBinds type_env
484 = map get_defn (concatMap implicit_ids (typeEnvElts type_env))
486 implicit_ids (ATyCon tc) = mapCatMaybes dataConWrapId_maybe (tyConDataCons tc)
487 implicit_ids (AClass cls) = classSelIds cls
490 get_defn :: Id -> CoreBind
491 get_defn id = NonRec id (unfoldingTemplate (idUnfolding id))
495 %************************************************************************
497 \subsection{Step 1: finding externals}
499 %************************************************************************
502 findExternalIds :: Bool
504 -> IdEnv Bool -- In domain => external
505 -- Range = True <=> show unfolding
506 -- Step 1 from the notes above
507 findExternalIds omit_prags binds
509 = mkVarEnv [ (id,False) | id <- bindersOfBinds binds, isExportedId id ]
512 = foldr find emptyVarEnv binds
514 find (NonRec id rhs) needed
515 | need_id needed id = addExternal (id,rhs) needed
517 find (Rec prs) needed = find_prs prs needed
519 -- For a recursive group we have to look for a fixed point
521 | null needed_prs = needed
522 | otherwise = find_prs other_prs new_needed
524 (needed_prs, other_prs) = partition (need_pr needed) prs
525 new_needed = foldr addExternal needed needed_prs
527 -- The 'needed' set contains the Ids that are needed by earlier
528 -- interface file emissions. If the Id isn't in this set, and isn't
529 -- exported, there's no need to emit anything
530 need_id needed_set id = id `elemVarEnv` needed_set || isExportedId id
531 need_pr needed_set (id,_) = need_id needed_set id
533 addExternal :: (Id,CoreExpr) -> IdEnv Bool -> IdEnv Bool
534 -- The Id is needed; extend the needed set
535 -- with it and its dependents (free vars etc)
536 addExternal (id,rhs) needed
537 = extendVarEnv (foldVarSet add_occ needed new_needed_ids)
540 add_occ id needed | id `elemVarEnv` needed = needed
541 | otherwise = extendVarEnv needed id False
542 -- "False" because we don't know we need the Id's unfolding
543 -- Don't override existing bindings; we might have already set it to True
545 new_needed_ids = worker_ids `unionVarSet`
546 unfold_ids `unionVarSet`
550 dont_inline = isNeverActive (inlinePragInfo idinfo)
551 loop_breaker = isNonRuleLoopBreaker (occInfo idinfo)
552 bottoming_fn = isBottomingSig (newStrictnessInfo idinfo `orElse` topSig)
553 spec_ids = specInfoFreeVars (specInfo idinfo)
554 worker_info = workerInfo idinfo
556 -- Stuff to do with the Id's unfolding
557 -- The simplifier has put an up-to-date unfolding
558 -- in the IdInfo, but the RHS will do just as well
559 unfolding = unfoldingInfo idinfo
560 rhs_is_small = not (neverUnfold unfolding)
562 -- We leave the unfolding there even if there is a worker
563 -- In GHCI the unfolding is used by importers
564 -- When writing an interface file, we omit the unfolding
565 -- if there is a worker
566 show_unfold = not bottoming_fn && -- Not necessary
569 rhs_is_small -- Small enough
571 unfold_ids | show_unfold = exprSomeFreeVars isLocalId rhs
572 | otherwise = emptyVarSet
574 worker_ids = case worker_info of
575 HasWorker work_id _ -> unitVarSet work_id
576 _otherwise -> emptyVarSet
581 findExternalRules :: [CoreBind]
582 -> [CoreRule] -- Non-local rules (i.e. ones for imported fns)
583 -> IdEnv a -- Ids that are exported, so we need their rules
585 -- The complete rules are gotten by combining
586 -- a) the non-local rules
587 -- b) rules embedded in the top-level Ids
588 findExternalRules binds non_local_rules ext_ids
589 = filter (not . internal_rule) (non_local_rules ++ local_rules)
592 | id <- bindersOfBinds binds,
593 id `elemVarEnv` ext_ids,
594 rule <- idCoreRules id
598 = any internal_id (varSetElems (ruleLhsFreeIds rule))
599 -- Don't export a rule whose LHS mentions a locally-defined
600 -- Id that is completely internal (i.e. not visible to an
603 internal_id id = not (id `elemVarEnv` ext_ids)
608 %************************************************************************
610 \subsection{Step 2: top-level tidying}
612 %************************************************************************
616 -- TopTidyEnv: when tidying we need to know
617 -- * nc_var: The NameCache, containing a unique supply and any pre-ordained Names.
618 -- These may have arisen because the
619 -- renamer read in an interface file mentioning M.$wf, say,
620 -- and assigned it unique r77. If, on this compilation, we've
621 -- invented an Id whose name is $wf (but with a different unique)
622 -- we want to rename it to have unique r77, so that we can do easy
623 -- comparisons with stuff from the interface file
625 -- * occ_env: The TidyOccEnv, which tells us which local occurrences
628 -- * subst_env: A Var->Var mapping that substitutes the new Var for the old
630 tidyTopBinds :: HscEnv
633 -> IdEnv Bool -- Domain = Ids that should be external
634 -- True <=> their unfolding is external too
636 -> IO (TidyEnv, [CoreBind])
638 tidyTopBinds hsc_env mod type_env ext_ids binds
639 = tidy init_env binds
641 nc_var = hsc_NC hsc_env
643 -- We also make sure to avoid any exported binders. Consider
644 -- f{-u1-} = 1 -- Local decl
646 -- f{-u2-} = 2 -- Exported decl
648 -- The second exported decl must 'get' the name 'f', so we
649 -- have to put 'f' in the avoids list before we get to the first
650 -- decl. tidyTopId then does a no-op on exported binders.
651 init_env = (initTidyOccEnv avoids, emptyVarEnv)
652 avoids = [getOccName name | bndr <- typeEnvIds type_env,
653 let name = idName bndr,
655 -- In computing our "avoids" list, we must include
657 -- all things with global names (assigned once and for
658 -- all by the renamer)
659 -- since their names are "taken".
660 -- The type environment is a convenient source of such things.
662 this_pkg = thisPackage (hsc_dflags hsc_env)
664 tidy env [] = return (env, [])
665 tidy env (b:bs) = do { (env1, b') <- tidyTopBind this_pkg mod nc_var ext_ids env b
666 ; (env2, bs') <- tidy env1 bs
667 ; return (env2, b':bs') }
669 ------------------------
670 tidyTopBind :: PackageId
672 -> IORef NameCache -- For allocating new unique names
673 -> IdEnv Bool -- Domain = Ids that should be external
674 -- True <=> their unfolding is external too
675 -> TidyEnv -> CoreBind
676 -> IO (TidyEnv, CoreBind)
678 tidyTopBind this_pkg mod nc_var ext_ids (occ_env1,subst1) (NonRec bndr rhs)
679 = do { (occ_env2, name') <- tidyTopName mod nc_var ext_ids occ_env1 bndr
680 ; let { (bndr', rhs') = tidyTopPair ext_ids tidy_env2 caf_info name' (bndr, rhs)
681 ; subst2 = extendVarEnv subst1 bndr bndr'
682 ; tidy_env2 = (occ_env2, subst2) }
683 ; return (tidy_env2, NonRec bndr' rhs') }
685 caf_info = hasCafRefs this_pkg subst1 (idArity bndr) rhs
687 tidyTopBind this_pkg mod nc_var ext_ids (occ_env1,subst1) (Rec prs)
688 = do { (occ_env2, names') <- tidyTopNames mod nc_var ext_ids occ_env1 bndrs
689 ; let { prs' = zipWith (tidyTopPair ext_ids tidy_env2 caf_info)
691 ; subst2 = extendVarEnvList subst1 (bndrs `zip` map fst prs')
692 ; tidy_env2 = (occ_env2, subst2) }
693 ; return (tidy_env2, Rec prs') }
697 -- the CafInfo for a recursive group says whether *any* rhs in
698 -- the group may refer indirectly to a CAF (because then, they all do).
700 | or [ mayHaveCafRefs (hasCafRefs this_pkg subst1 (idArity bndr) rhs)
701 | (bndr,rhs) <- prs ] = MayHaveCafRefs
702 | otherwise = NoCafRefs
704 --------------------------------------------------------------------
706 -- This is where we set names to local/global based on whether they really are
707 -- externally visible (see comment at the top of this module). If the name
708 -- was previously local, we have to give it a unique occurrence name if
709 -- we intend to externalise it.
710 tidyTopNames :: Module -> IORef NameCache -> VarEnv Bool -> TidyOccEnv
711 -> [Id] -> IO (TidyOccEnv, [Name])
712 tidyTopNames _mod _nc_var _ext_ids occ_env [] = return (occ_env, [])
713 tidyTopNames mod nc_var ext_ids occ_env (id:ids)
714 = do { (occ_env1, name) <- tidyTopName mod nc_var ext_ids occ_env id
715 ; (occ_env2, names) <- tidyTopNames mod nc_var ext_ids occ_env1 ids
716 ; return (occ_env2, name:names) }
718 tidyTopName :: Module -> IORef NameCache -> VarEnv Bool -> TidyOccEnv
719 -> Id -> IO (TidyOccEnv, Name)
720 tidyTopName mod nc_var ext_ids occ_env id
721 | global && internal = return (occ_env, localiseName name)
723 | global && external = return (occ_env, name)
724 -- Global names are assumed to have been allocated by the renamer,
725 -- so they already have the "right" unique
726 -- And it's a system-wide unique too
728 -- Now we get to the real reason that all this is in the IO Monad:
729 -- we have to update the name cache in a nice atomic fashion
731 | local && internal = do { nc <- readIORef nc_var
732 ; let (nc', new_local_name) = mk_new_local nc
733 ; writeIORef nc_var nc'
734 ; return (occ_env', new_local_name) }
735 -- Even local, internal names must get a unique occurrence, because
736 -- if we do -split-objs we externalise the name later, in the code generator
738 -- Similarly, we must make sure it has a system-wide Unique, because
739 -- the byte-code generator builds a system-wide Name->BCO symbol table
741 | local && external = do { nc <- readIORef nc_var
742 ; let (nc', new_external_name) = mk_new_external nc
743 ; writeIORef nc_var nc'
744 ; return (occ_env', new_external_name) }
746 | otherwise = panic "tidyTopName"
749 external = id `elemVarEnv` ext_ids
750 global = isExternalName name
752 internal = not external
753 loc = nameSrcSpan name
755 (occ_env', occ') = tidyOccName occ_env (nameOccName name)
757 mk_new_local nc = (nc { nsUniqs = us2 }, mkInternalName uniq occ' loc)
759 (us1, us2) = splitUniqSupply (nsUniqs nc)
760 uniq = uniqFromSupply us1
762 mk_new_external nc = allocateGlobalBinder nc mod occ' loc
763 -- If we want to externalise a currently-local name, check
764 -- whether we have already assigned a unique for it.
765 -- If so, use it; if not, extend the table.
766 -- All this is done by allcoateGlobalBinder.
767 -- This is needed when *re*-compiling a module in GHCi; we must
768 -- use the same name for externally-visible things as we did before.
771 -----------------------------------------------------------
772 tidyTopPair :: VarEnv Bool
773 -> TidyEnv -- The TidyEnv is used to tidy the IdInfo
774 -- It is knot-tied: don't look at it!
777 -> (Id, CoreExpr) -- Binder and RHS before tidying
779 -- This function is the heart of Step 2
780 -- The rec_tidy_env is the one to use for the IdInfo
781 -- It's necessary because when we are dealing with a recursive
782 -- group, a variable late in the group might be mentioned
783 -- in the IdInfo of one early in the group
785 tidyTopPair ext_ids rhs_tidy_env caf_info name' (bndr, rhs)
788 bndr' = mkGlobalId details name' ty' idinfo'
789 details = idDetails bndr -- Preserve the IdDetails
790 ty' = tidyTopType (idType bndr)
791 rhs' = tidyExpr rhs_tidy_env rhs
793 idinfo' = tidyTopIdInfo (isJust maybe_external)
794 idinfo unfold_info worker_info
797 -- Expose an unfolding if ext_ids tells us to
798 -- Remember that ext_ids maps an Id to a Bool:
799 -- True to show the unfolding, False to hide it
800 maybe_external = lookupVarEnv ext_ids bndr
801 show_unfold = maybe_external `orElse` False
802 unfold_info | show_unfold = mkTopUnfolding rhs'
803 | otherwise = noUnfolding
804 worker_info = tidyWorker rhs_tidy_env show_unfold (workerInfo idinfo)
806 -- Usually the Id will have an accurate arity on it, because
807 -- the simplifier has just run, but not always.
808 -- One case I found was when the last thing the simplifier
809 -- did was to let-bind a non-atomic argument and then float
810 -- it to the top level. So it seems more robust just to
812 arity = exprArity rhs
815 -- tidyTopIdInfo creates the final IdInfo for top-level
816 -- binders. There are two delicate pieces:
818 -- * Arity. After CoreTidy, this arity must not change any more.
819 -- Indeed, CorePrep must eta expand where necessary to make
820 -- the manifest arity equal to the claimed arity.
822 -- * CAF info. This must also remain valid through to code generation.
823 -- We add the info here so that it propagates to all
824 -- occurrences of the binders in RHSs, and hence to occurrences in
825 -- unfoldings, which are inside Ids imported by GHCi. Ditto RULES.
826 -- CoreToStg makes use of this when constructing SRTs.
827 tidyTopIdInfo :: Bool -> IdInfo -> Unfolding
828 -> WorkerInfo -> ArityInfo -> CafInfo
830 tidyTopIdInfo is_external idinfo unfold_info worker_info arity caf_info
831 | not is_external -- For internal Ids (not externally visible)
832 = vanillaIdInfo -- we only need enough info for code generation
833 -- Arity and strictness info are enough;
834 -- c.f. CoreTidy.tidyLetBndr
835 `setCafInfo` caf_info
837 `setAllStrictnessInfo` newStrictnessInfo idinfo
839 | otherwise -- Externally-visible Ids get the whole lot
841 `setCafInfo` caf_info
843 `setAllStrictnessInfo` newStrictnessInfo idinfo
844 `setInlinePragInfo` inlinePragInfo idinfo
845 `setUnfoldingInfo` unfold_info
846 `setWorkerInfo` worker_info
847 -- NB: we throw away the Rules
848 -- They have already been extracted by findExternalRules
852 ------------ Worker --------------
853 tidyWorker :: TidyEnv -> Bool -> WorkerInfo -> WorkerInfo
854 tidyWorker _tidy_env _show_unfold NoWorker
856 tidyWorker tidy_env show_unfold (HasWorker work_id wrap_arity)
857 | show_unfold = HasWorker (tidyVarOcc tidy_env work_id) wrap_arity
858 | otherwise = NoWorker
859 -- NB: do *not* expose the worker if show_unfold is off,
860 -- because that means this thing is a loop breaker or
861 -- marked NOINLINE or something like that
862 -- This is important: if you expose the worker for a loop-breaker
863 -- then you can make the simplifier go into an infinite loop, because
864 -- in effect the unfolding is exposed. See Trac #1709
866 -- You might think that if show_unfold is False, then the thing should
867 -- not be w/w'd in the first place. But a legitimate reason is this:
868 -- the function returns bottom
869 -- In this case, show_unfold will be false (we don't expose unfoldings
870 -- for bottoming functions), but we might still have a worker/wrapper
871 -- split (see Note [Worker-wrapper for bottoming functions] in WorkWrap.lhs
874 %************************************************************************
876 \subsection{Figuring out CafInfo for an expression}
878 %************************************************************************
880 hasCafRefs decides whether a top-level closure can point into the dynamic heap.
881 We mark such things as `MayHaveCafRefs' because this information is
882 used to decide whether a particular closure needs to be referenced
885 There are two reasons for setting MayHaveCafRefs:
886 a) The RHS is a CAF: a top-level updatable thunk.
887 b) The RHS refers to something that MayHaveCafRefs
889 Possible improvement: In an effort to keep the number of CAFs (and
890 hence the size of the SRTs) down, we could also look at the expression and
891 decide whether it requires a small bounded amount of heap, so we can ignore
892 it as a CAF. In these cases however, we would need to use an additional
893 CAF list to keep track of non-collectable CAFs.
896 hasCafRefs :: PackageId -> VarEnv Var -> Arity -> CoreExpr -> CafInfo
897 hasCafRefs this_pkg p arity expr
898 | is_caf || mentions_cafs
900 | otherwise = NoCafRefs
902 mentions_cafs = isFastTrue (cafRefs p expr)
903 is_caf = not (arity > 0 || rhsIsStatic this_pkg expr)
905 -- NB. we pass in the arity of the expression, which is expected
906 -- to be calculated by exprArity. This is because exprArity
907 -- knows how much eta expansion is going to be done by
908 -- CorePrep later on, and we don't want to duplicate that
909 -- knowledge in rhsIsStatic below.
911 cafRefs :: VarEnv Id -> Expr a -> FastBool
913 -- imported Ids first:
914 | not (isLocalId id) = fastBool (mayHaveCafRefs (idCafInfo id))
915 -- now Ids local to this module:
917 case lookupVarEnv p id of
918 Just id' -> fastBool (mayHaveCafRefs (idCafInfo id'))
919 Nothing -> fastBool False
921 cafRefs _ (Lit _) = fastBool False
922 cafRefs p (App f a) = fastOr (cafRefs p f) (cafRefs p) a
923 cafRefs p (Lam _ e) = cafRefs p e
924 cafRefs p (Let b e) = fastOr (cafRefss p (rhssOfBind b)) (cafRefs p) e
925 cafRefs p (Case e _bndr _ alts) = fastOr (cafRefs p e) (cafRefss p) (rhssOfAlts alts)
926 cafRefs p (Note _n e) = cafRefs p e
927 cafRefs p (Cast e _co) = cafRefs p e
928 cafRefs _ (Type _) = fastBool False
930 cafRefss :: VarEnv Id -> [Expr a] -> FastBool
931 cafRefss _ [] = fastBool False
932 cafRefss p (e:es) = fastOr (cafRefs p e) (cafRefss p) es
934 fastOr :: FastBool -> (a -> FastBool) -> a -> FastBool
935 -- hack for lazy-or over FastBool.
936 fastOr a f x = fastBool (isFastTrue a || isFastTrue (f x))