2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section{Tidying up Core}
7 module TidyPgm( mkBootModDetails, tidyProgram ) where
9 #include "HsVersions.h"
11 import DynFlags ( DynFlags, DynFlag(..), dopt )
13 import CoreUnfold ( noUnfolding, mkTopUnfolding )
14 import CoreFVs ( ruleLhsFreeIds, exprSomeFreeVars )
15 import CoreTidy ( tidyExpr, tidyVarOcc, tidyRules )
16 import PprCore ( pprRules )
17 import CoreLint ( showPass, endPass )
18 import CoreUtils ( exprArity, rhsIsStatic )
21 import Var ( Id, Var )
22 import Id ( idType, idInfo, idName, idCoreRules, isGlobalId,
23 isExportedId, mkVanillaGlobal, isLocalId,
24 idArity, idCafInfo, idUnfolding, isImplicitId, setIdInfo
26 import IdInfo {- loads of stuff -}
27 import InstEnv ( Instance, DFunId, instanceDFunId, setInstanceDFunId )
28 import NewDemand ( isBottomingSig, topSig )
29 import BasicTypes ( Arity, isNeverActive )
30 import Name ( Name, getOccName, nameOccName, mkInternalName,
31 localiseName, isExternalName, nameSrcLoc, nameParent_maybe,
32 isWiredInName, getName
34 import NameSet ( NameSet, elemNameSet )
35 import IfaceEnv ( allocateGlobalBinder )
36 import NameEnv ( filterNameEnv, mapNameEnv )
37 import OccName ( TidyOccEnv, initTidyOccEnv, tidyOccName )
38 import Type ( tidyTopType )
39 import TcType ( isFFITy )
40 import DataCon ( dataConName, dataConFieldLabels, dataConWrapId_maybe )
41 import TyCon ( TyCon, makeTyConAbstract, tyConDataCons, isNewTyCon,
42 newTyConRep, tyConSelIds, isAlgTyCon )
43 import Class ( classSelIds )
44 import Module ( Module )
45 import HscTypes ( HscEnv(..), NameCache( nsUniqs ), CgGuts(..),
46 TypeEnv, typeEnvIds, typeEnvElts, typeEnvTyCons,
47 extendTypeEnvWithIds, lookupTypeEnv,
48 ModGuts(..), TyThing(..), ModDetails(..), Dependencies(..)
50 import Maybes ( orElse, mapCatMaybes )
51 import ErrUtils ( showPass, dumpIfSet_core )
52 import UniqSupply ( splitUniqSupply, uniqFromSupply )
53 import List ( partition )
54 import Maybe ( isJust )
56 import DATA_IOREF ( IORef, readIORef, writeIORef )
57 import FastTypes hiding ( fastOr )
61 Constructing the TypeEnv, Instances, Rules from which the ModIface is
62 constructed, and which goes on to subsequent modules in --make mode.
64 Most of the interface file is obtained simply by serialising the
65 TypeEnv. One important consequence is that if the *interface file*
66 has pragma info if and only if the final TypeEnv does. This is not so
67 important for *this* module, but it's essential for ghc --make:
68 subsequent compilations must not see (e.g.) the arity if the interface
69 file does not contain arity If they do, they'll exploit the arity;
70 then the arity might change, but the iface file doesn't change =>
71 recompilation does not happen => disaster.
73 For data types, the final TypeEnv will have a TyThing for the TyCon,
74 plus one for each DataCon; the interface file will contain just one
75 data type declaration, but it is de-serialised back into a collection
78 %************************************************************************
82 %************************************************************************
85 Plan A: mkBootModDetails: omit pragmas, make interfaces small
86 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
89 * Drop all WiredIn things from the TypeEnv
90 (we never want them in interface files)
92 * Retain all TyCons and Classes in the TypeEnv, to avoid
93 having to find which ones are mentioned in the
96 * Trim off the constructors of non-exported TyCons, both
97 from the TyCon and from the TypeEnv
99 * Drop non-exported Ids from the TypeEnv
101 * Tidy the types of the DFunIds of Instances,
102 make them into GlobalIds, (they already have External Names)
103 and add them to the TypeEnv
105 * Tidy the types of the (exported) Ids in the TypeEnv,
106 make them into GlobalIds (they already have External Names)
108 * Drop rules altogether
110 * Tidy the bindings, to ensure that the Caf and Arity
111 information is correct for each top-level binder; the
112 code generator needs it. And to ensure that local names have
113 distinct OccNames in case of object-file splitting
116 mkBootModDetails :: HscEnv -> ModGuts -> IO ModDetails
117 -- This is Plan A: make a small type env when typechecking only,
118 -- or when compiling a hs-boot file, or simply when not using -O
120 -- We don't look at the bindings at all -- there aren't any
123 mkBootModDetails hsc_env (ModGuts { mg_module = mod,
124 mg_exports = exports,
127 = do { let dflags = hsc_dflags hsc_env
128 ; showPass dflags "Tidy [hoot] type env"
130 ; let { ispecs' = tidyInstances tidyExternalId ispecs
131 ; type_env1 = filterNameEnv (not . isWiredInThing) type_env
132 ; type_env2 = mapNameEnv tidyBootThing type_env1
133 ; type_env' = extendTypeEnvWithIds type_env2
134 (map instanceDFunId ispecs')
136 ; return (ModDetails { md_types = type_env',
139 md_exports = exports })
143 isWiredInThing :: TyThing -> Bool
144 isWiredInThing thing = isWiredInName (getName thing)
146 tidyBootThing :: TyThing -> TyThing
147 -- Just externalise the Ids; keep everything
148 tidyBootThing (AnId id) | isLocalId id = AnId (tidyExternalId id)
149 tidyBootThing thing = thing
151 tidyExternalId :: Id -> Id
152 -- Takes an LocalId with an External Name,
153 -- makes it into a GlobalId with VanillaIdInfo, and tidies its type
154 -- (NB: vanillaIdInfo makes a conservative assumption about Caf-hood.)
156 = ASSERT2( isLocalId id && isExternalName (idName id), ppr id )
157 mkVanillaGlobal (idName id) (tidyTopType (idType id)) vanillaIdInfo
161 %************************************************************************
163 Plan B: tidy bindings, make TypeEnv full of IdInfo
165 %************************************************************************
167 Plan B: include pragmas, make interfaces
168 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
169 * Figure out which Ids are externally visible
171 * Tidy the bindings, externalising appropriate Ids
173 * Drop all Ids from the TypeEnv, and add all the External Ids from
174 the bindings. (This adds their IdInfo to the TypeEnv; and adds
175 floated-out Ids that weren't even in the TypeEnv before.)
177 Step 1: Figure out external Ids
178 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
179 First we figure out which Ids are "external" Ids. An
180 "external" Id is one that is visible from outside the compilation
182 a) the user exported ones
183 b) ones mentioned in the unfoldings, workers,
184 or rules of externally-visible ones
185 This exercise takes a sweep of the bindings bottom to top. Actually,
186 in Step 2 we're also going to need to know which Ids should be
187 exported with their unfoldings, so we produce not an IdSet but an
191 Step 2: Tidy the program
192 ~~~~~~~~~~~~~~~~~~~~~~~~
193 Next we traverse the bindings top to bottom. For each *top-level*
196 1. Make it into a GlobalId; its IdDetails becomes VanillaGlobal,
197 reflecting the fact that from now on we regard it as a global,
200 2. Give it a system-wide Unique.
201 [Even non-exported things need system-wide Uniques because the
202 byte-code generator builds a single Name->BCO symbol table.]
204 We use the NameCache kept in the HscEnv as the
205 source of such system-wide uniques.
207 For external Ids, use the original-name cache in the NameCache
208 to ensure that the unique assigned is the same as the Id had
209 in any previous compilation run.
211 3. If it's an external Id, make it have a External Name, otherwise
212 make it have an Internal Name.
213 This is used by the code generator to decide whether
214 to make the label externally visible
216 4. Give external Ids a "tidy" OccName. This means
217 we can print them in interface files without confusing
218 "x" (unique 5) with "x" (unique 10).
220 5. Give it its UTTERLY FINAL IdInfo; in ptic,
221 * its unfolding, if it should have one
223 * its arity, computed from the number of visible lambdas
225 * its CAF info, computed from what is free in its RHS
228 Finally, substitute these new top-level binders consistently
229 throughout, including in unfoldings. We also tidy binders in
230 RHSs, so that they print nicely in interfaces.
233 tidyProgram :: HscEnv -> ModGuts -> IO (CgGuts, ModDetails)
235 mod_impl@(ModGuts { mg_module = mod, mg_exports = exports,
236 mg_types = type_env, mg_insts = insts_tc,
238 mg_rules = imp_rules,
239 mg_dir_imps = dir_imps, mg_deps = deps,
240 mg_home_mods = home_mods,
241 mg_foreign = foreign_stubs })
243 = do { let dflags = hsc_dflags hsc_env
244 ; showPass dflags "Tidy Core"
246 ; let { omit_prags = dopt Opt_OmitInterfacePragmas dflags
247 ; ext_ids = findExternalIds omit_prags binds
250 | otherwise = findExternalRules binds imp_rules ext_ids
251 -- findExternalRules filters imp_rules to avoid binders that
252 -- aren't externally visible; but the externally-visible binders
253 -- are computed (by findExternalIds) assuming that all orphan
254 -- rules are exported (they get their Exported flag set in the desugarer)
255 -- So in fact we may export more than we need.
256 -- (It's a sort of mutual recursion.)
259 ; (tidy_env, tidy_binds) <- tidyTopBinds hsc_env mod type_env ext_ids binds
261 ; let { tidy_type_env = tidyTypeEnv omit_prags exports type_env tidy_binds
262 ; tidy_ispecs = tidyInstances (lookup_dfun tidy_type_env) insts_tc
263 -- A DFunId will have a binding in tidy_binds, and so
264 -- will now be in final_env, replete with IdInfo
265 -- Its name will be unchanged since it was born, but
266 -- we want Global, IdInfo-rich (or not) DFunId in the tidy_ispecs
268 ; tidy_rules = tidyRules tidy_env ext_rules
269 -- You might worry that the tidy_env contains IdInfo-rich stuff
270 -- and indeed it does, but if omit_prags is on, ext_rules is empty
272 ; implicit_binds = getImplicitBinds type_env
273 ; alg_tycons = filter isAlgTyCon (typeEnvTyCons type_env)
276 ; endPass dflags "Tidy Core" Opt_D_dump_simpl tidy_binds
277 ; dumpIfSet_core dflags Opt_D_dump_simpl
279 (pprRules tidy_rules)
281 ; return (CgGuts { cg_module = mod,
282 cg_tycons = alg_tycons,
283 cg_binds = implicit_binds ++ tidy_binds,
284 cg_dir_imps = dir_imps,
285 cg_foreign = foreign_stubs,
286 cg_home_mods = home_mods,
287 cg_dep_pkgs = dep_pkgs deps },
289 ModDetails { md_types = tidy_type_env,
290 md_rules = tidy_rules,
291 md_insts = tidy_ispecs,
292 md_exports = exports })
295 lookup_dfun type_env dfun_id
296 = case lookupTypeEnv type_env (idName dfun_id) of
297 Just (AnId dfun_id') -> dfun_id'
298 other -> pprPanic "lookup_dfun" (ppr dfun_id)
300 tidyTypeEnv :: Bool -> NameSet -> TypeEnv -> [CoreBind] -> TypeEnv
302 -- The competed type environment is gotten from
303 -- Dropping any wired-in things, and then
304 -- a) keeping the types and classes
305 -- b) removing all Ids,
306 -- c) adding Ids with correct IdInfo, including unfoldings,
307 -- gotten from the bindings
308 -- From (c) we keep only those Ids with External names;
309 -- the CoreTidy pass makes sure these are all and only
310 -- the externally-accessible ones
311 -- This truncates the type environment to include only the
312 -- exported Ids and things needed from them, which saves space
314 tidyTypeEnv omit_prags exports type_env tidy_binds
315 = let type_env1 = filterNameEnv keep_it type_env
316 type_env2 = extendTypeEnvWithIds type_env1 final_ids
317 type_env3 | omit_prags = mapNameEnv trim_thing type_env2
318 | otherwise = type_env2
322 final_ids = [ id | id <- bindersOfBinds tidy_binds,
323 isExternalName (idName id)]
325 -- We keep GlobalIds, because they won't appear
326 -- in the bindings from which final_ids are derived!
327 -- (The bindings bind LocalIds.)
328 keep_it thing | isWiredInThing thing = False
329 keep_it (AnId id) = isGlobalId id -- Keep GlobalIds (e.g. class ops)
330 keep_it other = True -- Keep all TyCons, DataCons, and Classes
334 ATyCon tc | mustExposeTyCon exports tc -> thing
335 | otherwise -> ATyCon (makeTyConAbstract tc)
337 AnId id | isImplicitId id -> thing
338 | otherwise -> AnId (id `setIdInfo` vanillaIdInfo)
342 mustExposeTyCon :: NameSet -- Exports
343 -> TyCon -- The tycon
344 -> Bool -- Can its rep be hidden?
345 -- We are compiling without -O, and thus trying to write as little as
346 -- possible into the interface file. But we must expose the details of
347 -- any data types whose constructors or fields are exported
348 mustExposeTyCon exports tc
349 | not (isAlgTyCon tc) -- Synonyms
351 | otherwise -- Newtype, datatype
352 = any exported_con (tyConDataCons tc)
353 -- Expose rep if any datacon or field is exported
355 || (isNewTyCon tc && isFFITy (snd (newTyConRep tc)))
356 -- Expose the rep for newtypes if the rep is an FFI type.
357 -- For a very annoying reason. 'Foreign import' is meant to
358 -- be able to look through newtypes transparently, but it
359 -- can only do that if it can "see" the newtype representation
361 exported_con con = any (`elemNameSet` exports)
362 (dataConName con : dataConFieldLabels con)
364 tidyInstances :: (DFunId -> DFunId) -> [Instance] -> [Instance]
365 tidyInstances tidy_dfun ispecs
368 tidy ispec = setInstanceDFunId ispec $
369 tidy_dfun (instanceDFunId ispec)
371 getImplicitBinds :: TypeEnv -> [CoreBind]
372 getImplicitBinds type_env
373 = map get_defn (concatMap implicit_con_ids (typeEnvTyCons type_env)
374 ++ concatMap other_implicit_ids (typeEnvElts type_env))
375 -- Put the constructor wrappers first, because
376 -- other implicit bindings (notably the fromT functions arising
377 -- from generics) use the constructor wrappers. At least that's
378 -- what External Core likes
380 implicit_con_ids tc = mapCatMaybes dataConWrapId_maybe (tyConDataCons tc)
382 other_implicit_ids (ATyCon tc) = tyConSelIds tc
383 other_implicit_ids (AClass cl) = classSelIds cl
384 other_implicit_ids other = []
386 get_defn :: Id -> CoreBind
387 get_defn id = NonRec id (tidyExpr emptyTidyEnv rhs)
389 rhs = unfoldingTemplate (idUnfolding id)
390 -- Don't forget to tidy the body ! Otherwise you get silly things like
391 -- \ tpl -> case tpl of tpl -> (tpl,tpl) -> tpl
395 %************************************************************************
397 \subsection{Step 1: finding externals}
399 %************************************************************************
402 findExternalIds :: Bool
404 -> IdEnv Bool -- In domain => external
405 -- Range = True <=> show unfolding
406 -- Step 1 from the notes above
407 findExternalIds omit_prags binds
409 = mkVarEnv [ (id,False) | id <- bindersOfBinds binds, isExportedId id ]
412 = foldr find emptyVarEnv binds
414 find (NonRec id rhs) needed
415 | need_id needed id = addExternal (id,rhs) needed
417 find (Rec prs) needed = find_prs prs needed
419 -- For a recursive group we have to look for a fixed point
421 | null needed_prs = needed
422 | otherwise = find_prs other_prs new_needed
424 (needed_prs, other_prs) = partition (need_pr needed) prs
425 new_needed = foldr addExternal needed needed_prs
427 -- The 'needed' set contains the Ids that are needed by earlier
428 -- interface file emissions. If the Id isn't in this set, and isn't
429 -- exported, there's no need to emit anything
430 need_id needed_set id = id `elemVarEnv` needed_set || isExportedId id
431 need_pr needed_set (id,rhs) = need_id needed_set id
433 addExternal :: (Id,CoreExpr) -> IdEnv Bool -> IdEnv Bool
434 -- The Id is needed; extend the needed set
435 -- with it and its dependents (free vars etc)
436 addExternal (id,rhs) needed
437 = extendVarEnv (foldVarSet add_occ needed new_needed_ids)
440 add_occ id needed = extendVarEnv needed id False
441 -- "False" because we don't know we need the Id's unfolding
442 -- We'll override it later when we find the binding site
444 new_needed_ids = worker_ids `unionVarSet`
445 unfold_ids `unionVarSet`
449 dont_inline = isNeverActive (inlinePragInfo idinfo)
450 loop_breaker = isLoopBreaker (occInfo idinfo)
451 bottoming_fn = isBottomingSig (newStrictnessInfo idinfo `orElse` topSig)
452 spec_ids = specInfoFreeVars (specInfo idinfo)
453 worker_info = workerInfo idinfo
455 -- Stuff to do with the Id's unfolding
456 -- The simplifier has put an up-to-date unfolding
457 -- in the IdInfo, but the RHS will do just as well
458 unfolding = unfoldingInfo idinfo
459 rhs_is_small = not (neverUnfold unfolding)
461 -- We leave the unfolding there even if there is a worker
462 -- In GHCI the unfolding is used by importers
463 -- When writing an interface file, we omit the unfolding
464 -- if there is a worker
465 show_unfold = not bottoming_fn && -- Not necessary
468 rhs_is_small -- Small enough
470 unfold_ids | show_unfold = exprSomeFreeVars isLocalId rhs
471 | otherwise = emptyVarSet
473 worker_ids = case worker_info of
474 HasWorker work_id _ -> unitVarSet work_id
475 otherwise -> emptyVarSet
480 findExternalRules :: [CoreBind]
481 -> [CoreRule] -- Non-local rules (i.e. ones for imported fns)
482 -> IdEnv a -- Ids that are exported, so we need their rules
484 -- The complete rules are gotten by combining
485 -- a) the non-local rules
486 -- b) rules embedded in the top-level Ids
487 findExternalRules binds non_local_rules ext_ids
488 = filter (not . internal_rule) (non_local_rules ++ local_rules)
491 | id <- bindersOfBinds binds,
492 id `elemVarEnv` ext_ids,
493 rule <- idCoreRules id
497 = any internal_id (varSetElems (ruleLhsFreeIds rule))
498 -- Don't export a rule whose LHS mentions a locally-defined
499 -- Id that is completely internal (i.e. not visible to an
502 internal_id id = not (id `elemVarEnv` ext_ids)
507 %************************************************************************
509 \subsection{Step 2: top-level tidying}
511 %************************************************************************
515 -- TopTidyEnv: when tidying we need to know
516 -- * nc_var: The NameCache, containing a unique supply and any pre-ordained Names.
517 -- These may have arisen because the
518 -- renamer read in an interface file mentioning M.$wf, say,
519 -- and assigned it unique r77. If, on this compilation, we've
520 -- invented an Id whose name is $wf (but with a different unique)
521 -- we want to rename it to have unique r77, so that we can do easy
522 -- comparisons with stuff from the interface file
524 -- * occ_env: The TidyOccEnv, which tells us which local occurrences
527 -- * subst_env: A Var->Var mapping that substitutes the new Var for the old
529 tidyTopBinds :: HscEnv
532 -> IdEnv Bool -- Domain = Ids that should be external
533 -- True <=> their unfolding is external too
535 -> IO (TidyEnv, [CoreBind])
537 tidyTopBinds hsc_env mod type_env ext_ids binds
538 = tidy init_env binds
540 dflags = hsc_dflags hsc_env
541 nc_var = hsc_NC hsc_env
543 -- We also make sure to avoid any exported binders. Consider
544 -- f{-u1-} = 1 -- Local decl
546 -- f{-u2-} = 2 -- Exported decl
548 -- The second exported decl must 'get' the name 'f', so we
549 -- have to put 'f' in the avoids list before we get to the first
550 -- decl. tidyTopId then does a no-op on exported binders.
551 init_env = (initTidyOccEnv avoids, emptyVarEnv)
552 avoids = [getOccName name | bndr <- typeEnvIds type_env,
553 let name = idName bndr,
555 -- In computing our "avoids" list, we must include
557 -- all things with global names (assigned once and for
558 -- all by the renamer)
559 -- since their names are "taken".
560 -- The type environment is a convenient source of such things.
562 tidy env [] = return (env, [])
563 tidy env (b:bs) = do { (env1, b') <- tidyTopBind dflags mod nc_var ext_ids env b
564 ; (env2, bs') <- tidy env1 bs
565 ; return (env2, b':bs') }
567 ------------------------
568 tidyTopBind :: DynFlags
570 -> IORef NameCache -- For allocating new unique names
571 -> IdEnv Bool -- Domain = Ids that should be external
572 -- True <=> their unfolding is external too
573 -> TidyEnv -> CoreBind
574 -> IO (TidyEnv, CoreBind)
576 tidyTopBind dflags mod nc_var ext_ids tidy_env1@(occ_env1,subst1) (NonRec bndr rhs)
577 = do { (occ_env2, name') <- tidyTopName mod nc_var ext_ids occ_env1 bndr
578 ; let { (bndr', rhs') = tidyTopPair ext_ids tidy_env2 caf_info name' (bndr, rhs)
579 ; subst2 = extendVarEnv subst1 bndr bndr'
580 ; tidy_env2 = (occ_env2, subst2) }
581 ; return (tidy_env2, NonRec bndr' rhs') }
583 caf_info = hasCafRefs dflags subst1 (idArity bndr) rhs
585 tidyTopBind dflags mod nc_var ext_ids tidy_env1@(occ_env1,subst1) (Rec prs)
586 = do { (occ_env2, names') <- tidyTopNames mod nc_var ext_ids occ_env1 bndrs
587 ; let { prs' = zipWith (tidyTopPair ext_ids tidy_env2 caf_info)
589 ; subst2 = extendVarEnvList subst1 (bndrs `zip` map fst prs')
590 ; tidy_env2 = (occ_env2, subst2) }
591 ; return (tidy_env2, Rec prs') }
595 -- the CafInfo for a recursive group says whether *any* rhs in
596 -- the group may refer indirectly to a CAF (because then, they all do).
598 | or [ mayHaveCafRefs (hasCafRefs dflags subst1 (idArity bndr) rhs)
599 | (bndr,rhs) <- prs ] = MayHaveCafRefs
600 | otherwise = NoCafRefs
602 --------------------------------------------------------------------
604 -- This is where we set names to local/global based on whether they really are
605 -- externally visible (see comment at the top of this module). If the name
606 -- was previously local, we have to give it a unique occurrence name if
607 -- we intend to externalise it.
608 tidyTopNames mod nc_var ext_ids occ_env [] = return (occ_env, [])
609 tidyTopNames mod nc_var ext_ids occ_env (id:ids)
610 = do { (occ_env1, name) <- tidyTopName mod nc_var ext_ids occ_env id
611 ; (occ_env2, names) <- tidyTopNames mod nc_var ext_ids occ_env1 ids
612 ; return (occ_env2, name:names) }
614 tidyTopName :: Module -> IORef NameCache -> VarEnv Bool -> TidyOccEnv
615 -> Id -> IO (TidyOccEnv, Name)
616 tidyTopName mod nc_var ext_ids occ_env id
617 | global && internal = return (occ_env, localiseName name)
619 | global && external = return (occ_env, name)
620 -- Global names are assumed to have been allocated by the renamer,
621 -- so they already have the "right" unique
622 -- And it's a system-wide unique too
624 -- Now we get to the real reason that all this is in the IO Monad:
625 -- we have to update the name cache in a nice atomic fashion
627 | local && internal = do { nc <- readIORef nc_var
628 ; let (nc', new_local_name) = mk_new_local nc
629 ; writeIORef nc_var nc'
630 ; return (occ_env', new_local_name) }
631 -- Even local, internal names must get a unique occurrence, because
632 -- if we do -split-objs we externalise the name later, in the code generator
634 -- Similarly, we must make sure it has a system-wide Unique, because
635 -- the byte-code generator builds a system-wide Name->BCO symbol table
637 | local && external = do { nc <- readIORef nc_var
638 ; let (nc', new_external_name) = mk_new_external nc
639 ; writeIORef nc_var nc'
640 ; return (occ_env', new_external_name) }
643 external = id `elemVarEnv` ext_ids
644 global = isExternalName name
646 internal = not external
647 mb_parent = nameParent_maybe name
648 loc = nameSrcLoc name
650 (occ_env', occ') = tidyOccName occ_env (nameOccName name)
652 mk_new_local nc = (nc { nsUniqs = us2 }, mkInternalName uniq occ' loc)
654 (us1, us2) = splitUniqSupply (nsUniqs nc)
655 uniq = uniqFromSupply us1
657 mk_new_external nc = allocateGlobalBinder nc mod occ' mb_parent loc
658 -- If we want to externalise a currently-local name, check
659 -- whether we have already assigned a unique for it.
660 -- If so, use it; if not, extend the table.
661 -- All this is done by allcoateGlobalBinder.
662 -- This is needed when *re*-compiling a module in GHCi; we must
663 -- use the same name for externally-visible things as we did before.
666 -----------------------------------------------------------
667 tidyTopPair :: VarEnv Bool
668 -> TidyEnv -- The TidyEnv is used to tidy the IdInfo
669 -- It is knot-tied: don't look at it!
672 -> (Id, CoreExpr) -- Binder and RHS before tidying
674 -- This function is the heart of Step 2
675 -- The rec_tidy_env is the one to use for the IdInfo
676 -- It's necessary because when we are dealing with a recursive
677 -- group, a variable late in the group might be mentioned
678 -- in the IdInfo of one early in the group
680 tidyTopPair ext_ids rhs_tidy_env caf_info name' (bndr, rhs)
681 | isGlobalId bndr -- Injected binding for record selector, etc
682 = (bndr, tidyExpr rhs_tidy_env rhs)
686 bndr' = mkVanillaGlobal name' ty' idinfo'
687 ty' = tidyTopType (idType bndr)
688 rhs' = tidyExpr rhs_tidy_env rhs
689 idinfo' = tidyTopIdInfo rhs_tidy_env (isJust maybe_external)
690 (idInfo bndr) unfold_info arity
693 -- Expose an unfolding if ext_ids tells us to
694 -- Remember that ext_ids maps an Id to a Bool:
695 -- True to show the unfolding, False to hide it
696 maybe_external = lookupVarEnv ext_ids bndr
697 show_unfold = maybe_external `orElse` False
698 unfold_info | show_unfold = mkTopUnfolding rhs'
699 | otherwise = noUnfolding
701 -- Usually the Id will have an accurate arity on it, because
702 -- the simplifier has just run, but not always.
703 -- One case I found was when the last thing the simplifier
704 -- did was to let-bind a non-atomic argument and then float
705 -- it to the top level. So it seems more robust just to
707 arity = exprArity rhs
710 -- tidyTopIdInfo creates the final IdInfo for top-level
711 -- binders. There are two delicate pieces:
713 -- * Arity. After CoreTidy, this arity must not change any more.
714 -- Indeed, CorePrep must eta expand where necessary to make
715 -- the manifest arity equal to the claimed arity.
717 -- * CAF info. This must also remain valid through to code generation.
718 -- We add the info here so that it propagates to all
719 -- occurrences of the binders in RHSs, and hence to occurrences in
720 -- unfoldings, which are inside Ids imported by GHCi. Ditto RULES.
721 -- CoreToStg makes use of this when constructing SRTs.
723 tidyTopIdInfo tidy_env is_external idinfo unfold_info arity caf_info
724 | not is_external -- For internal Ids (not externally visible)
725 = vanillaIdInfo -- we only need enough info for code generation
726 -- Arity and strictness info are enough;
727 -- c.f. CoreTidy.tidyLetBndr
728 `setCafInfo` caf_info
730 `setAllStrictnessInfo` newStrictnessInfo idinfo
732 | otherwise -- Externally-visible Ids get the whole lot
734 `setCafInfo` caf_info
736 `setAllStrictnessInfo` newStrictnessInfo idinfo
737 `setInlinePragInfo` inlinePragInfo idinfo
738 `setUnfoldingInfo` unfold_info
739 `setWorkerInfo` tidyWorker tidy_env (workerInfo idinfo)
740 -- NB: we throw away the Rules
741 -- They have already been extracted by findExternalRules
745 ------------ Worker --------------
746 tidyWorker tidy_env (HasWorker work_id wrap_arity)
747 = HasWorker (tidyVarOcc tidy_env work_id) wrap_arity
748 tidyWorker tidy_env other
752 %************************************************************************
754 \subsection{Figuring out CafInfo for an expression}
756 %************************************************************************
758 hasCafRefs decides whether a top-level closure can point into the dynamic heap.
759 We mark such things as `MayHaveCafRefs' because this information is
760 used to decide whether a particular closure needs to be referenced
763 There are two reasons for setting MayHaveCafRefs:
764 a) The RHS is a CAF: a top-level updatable thunk.
765 b) The RHS refers to something that MayHaveCafRefs
767 Possible improvement: In an effort to keep the number of CAFs (and
768 hence the size of the SRTs) down, we could also look at the expression and
769 decide whether it requires a small bounded amount of heap, so we can ignore
770 it as a CAF. In these cases however, we would need to use an additional
771 CAF list to keep track of non-collectable CAFs.
774 hasCafRefs :: DynFlags -> VarEnv Var -> Arity -> CoreExpr -> CafInfo
775 hasCafRefs dflags p arity expr
776 | is_caf || mentions_cafs = MayHaveCafRefs
777 | otherwise = NoCafRefs
779 mentions_cafs = isFastTrue (cafRefs p expr)
780 is_caf = not (arity > 0 || rhsIsStatic dflags expr)
781 -- NB. we pass in the arity of the expression, which is expected
782 -- to be calculated by exprArity. This is because exprArity
783 -- knows how much eta expansion is going to be done by
784 -- CorePrep later on, and we don't want to duplicate that
785 -- knowledge in rhsIsStatic below.
788 -- imported Ids first:
789 | not (isLocalId id) = fastBool (mayHaveCafRefs (idCafInfo id))
790 -- now Ids local to this module:
792 case lookupVarEnv p id of
793 Just id' -> fastBool (mayHaveCafRefs (idCafInfo id'))
794 Nothing -> fastBool False
796 cafRefs p (Lit l) = fastBool False
797 cafRefs p (App f a) = fastOr (cafRefs p f) (cafRefs p) a
798 cafRefs p (Lam x e) = cafRefs p e
799 cafRefs p (Let b e) = fastOr (cafRefss p (rhssOfBind b)) (cafRefs p) e
800 cafRefs p (Case e bndr _ alts) = fastOr (cafRefs p e) (cafRefss p) (rhssOfAlts alts)
801 cafRefs p (Note n e) = cafRefs p e
802 cafRefs p (Type t) = fastBool False
804 cafRefss p [] = fastBool False
805 cafRefss p (e:es) = fastOr (cafRefs p e) (cafRefss p) es
807 -- hack for lazy-or over FastBool.
808 fastOr a f x = fastBool (isFastTrue a || isFastTrue (f x))