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_foreign = foreign_stubs })
242 = do { let dflags = hsc_dflags hsc_env
243 ; showPass dflags "Tidy Core"
245 ; let { omit_prags = dopt Opt_OmitInterfacePragmas dflags
246 ; ext_ids = findExternalIds omit_prags binds
249 | otherwise = findExternalRules binds imp_rules ext_ids
250 -- findExternalRules filters imp_rules to avoid binders that
251 -- aren't externally visible; but the externally-visible binders
252 -- are computed (by findExternalIds) assuming that all orphan
253 -- rules are exported (they get their Exported flag set in the desugarer)
254 -- So in fact we may export more than we need.
255 -- (It's a sort of mutual recursion.)
258 ; (tidy_env, tidy_binds) <- tidyTopBinds hsc_env mod type_env ext_ids binds
260 ; let { tidy_type_env = tidyTypeEnv omit_prags exports type_env tidy_binds
261 ; tidy_ispecs = tidyInstances (lookup_dfun tidy_type_env) insts_tc
262 -- A DFunId will have a binding in tidy_binds, and so
263 -- will now be in final_env, replete with IdInfo
264 -- Its name will be unchanged since it was born, but
265 -- we want Global, IdInfo-rich (or not) DFunId in the tidy_ispecs
267 ; tidy_rules = tidyRules tidy_env ext_rules
268 -- You might worry that the tidy_env contains IdInfo-rich stuff
269 -- and indeed it does, but if omit_prags is on, ext_rules is empty
271 ; implicit_binds = getImplicitBinds type_env
272 ; alg_tycons = filter isAlgTyCon (typeEnvTyCons type_env)
275 ; endPass dflags "Tidy Core" Opt_D_dump_simpl tidy_binds
276 ; dumpIfSet_core dflags Opt_D_dump_simpl
278 (pprRules tidy_rules)
280 ; return (CgGuts { cg_module = mod,
281 cg_tycons = alg_tycons,
282 cg_binds = implicit_binds ++ tidy_binds,
283 cg_dir_imps = dir_imps,
284 cg_foreign = foreign_stubs,
285 cg_dep_pkgs = dep_pkgs deps },
287 ModDetails { md_types = tidy_type_env,
288 md_rules = tidy_rules,
289 md_insts = tidy_ispecs,
290 md_exports = exports })
293 lookup_dfun type_env dfun_id
294 = case lookupTypeEnv type_env (idName dfun_id) of
295 Just (AnId dfun_id') -> dfun_id'
296 other -> pprPanic "lookup_dfun" (ppr dfun_id)
298 tidyTypeEnv :: Bool -> NameSet -> TypeEnv -> [CoreBind] -> TypeEnv
300 -- The competed type environment is gotten from
301 -- Dropping any wired-in things, and then
302 -- a) keeping the types and classes
303 -- b) removing all Ids,
304 -- c) adding Ids with correct IdInfo, including unfoldings,
305 -- gotten from the bindings
306 -- From (c) we keep only those Ids with External names;
307 -- the CoreTidy pass makes sure these are all and only
308 -- the externally-accessible ones
309 -- This truncates the type environment to include only the
310 -- exported Ids and things needed from them, which saves space
312 tidyTypeEnv omit_prags exports type_env tidy_binds
313 = let type_env1 = filterNameEnv keep_it type_env
314 type_env2 = extendTypeEnvWithIds type_env1 final_ids
315 type_env3 | omit_prags = mapNameEnv trim_thing type_env2
316 | otherwise = type_env2
320 final_ids = [ id | id <- bindersOfBinds tidy_binds,
321 isExternalName (idName id)]
323 -- We keep GlobalIds, because they won't appear
324 -- in the bindings from which final_ids are derived!
325 -- (The bindings bind LocalIds.)
326 keep_it thing | isWiredInThing thing = False
327 keep_it (AnId id) = isGlobalId id -- Keep GlobalIds (e.g. class ops)
328 keep_it other = True -- Keep all TyCons, DataCons, and Classes
332 ATyCon tc | mustExposeTyCon exports tc -> thing
333 | otherwise -> ATyCon (makeTyConAbstract tc)
335 AnId id | isImplicitId id -> thing
336 | otherwise -> AnId (id `setIdInfo` vanillaIdInfo)
340 mustExposeTyCon :: NameSet -- Exports
341 -> TyCon -- The tycon
342 -> Bool -- Can its rep be hidden?
343 -- We are compiling without -O, and thus trying to write as little as
344 -- possible into the interface file. But we must expose the details of
345 -- any data types whose constructors or fields are exported
346 mustExposeTyCon exports tc
347 | not (isAlgTyCon tc) -- Synonyms
349 | otherwise -- Newtype, datatype
350 = any exported_con (tyConDataCons tc)
351 -- Expose rep if any datacon or field is exported
353 || (isNewTyCon tc && isFFITy (snd (newTyConRep tc)))
354 -- Expose the rep for newtypes if the rep is an FFI type.
355 -- For a very annoying reason. 'Foreign import' is meant to
356 -- be able to look through newtypes transparently, but it
357 -- can only do that if it can "see" the newtype representation
359 exported_con con = any (`elemNameSet` exports)
360 (dataConName con : dataConFieldLabels con)
362 tidyInstances :: (DFunId -> DFunId) -> [Instance] -> [Instance]
363 tidyInstances tidy_dfun ispecs
366 tidy ispec = setInstanceDFunId ispec $
367 tidy_dfun (instanceDFunId ispec)
369 getImplicitBinds :: TypeEnv -> [CoreBind]
370 getImplicitBinds type_env
371 = map get_defn (concatMap implicit_con_ids (typeEnvTyCons type_env)
372 ++ concatMap other_implicit_ids (typeEnvElts type_env))
373 -- Put the constructor wrappers first, because
374 -- other implicit bindings (notably the fromT functions arising
375 -- from generics) use the constructor wrappers. At least that's
376 -- what External Core likes
378 implicit_con_ids tc = mapCatMaybes dataConWrapId_maybe (tyConDataCons tc)
380 other_implicit_ids (ATyCon tc) = tyConSelIds tc
381 other_implicit_ids (AClass cl) = classSelIds cl
382 other_implicit_ids other = []
384 get_defn :: Id -> CoreBind
385 get_defn id = NonRec id (tidyExpr emptyTidyEnv rhs)
387 rhs = unfoldingTemplate (idUnfolding id)
388 -- Don't forget to tidy the body ! Otherwise you get silly things like
389 -- \ tpl -> case tpl of tpl -> (tpl,tpl) -> tpl
393 %************************************************************************
395 \subsection{Step 1: finding externals}
397 %************************************************************************
400 findExternalIds :: Bool
402 -> IdEnv Bool -- In domain => external
403 -- Range = True <=> show unfolding
404 -- Step 1 from the notes above
405 findExternalIds omit_prags binds
407 = mkVarEnv [ (id,False) | id <- bindersOfBinds binds, isExportedId id ]
410 = foldr find emptyVarEnv binds
412 find (NonRec id rhs) needed
413 | need_id needed id = addExternal (id,rhs) needed
415 find (Rec prs) needed = find_prs prs needed
417 -- For a recursive group we have to look for a fixed point
419 | null needed_prs = needed
420 | otherwise = find_prs other_prs new_needed
422 (needed_prs, other_prs) = partition (need_pr needed) prs
423 new_needed = foldr addExternal needed needed_prs
425 -- The 'needed' set contains the Ids that are needed by earlier
426 -- interface file emissions. If the Id isn't in this set, and isn't
427 -- exported, there's no need to emit anything
428 need_id needed_set id = id `elemVarEnv` needed_set || isExportedId id
429 need_pr needed_set (id,rhs) = need_id needed_set id
431 addExternal :: (Id,CoreExpr) -> IdEnv Bool -> IdEnv Bool
432 -- The Id is needed; extend the needed set
433 -- with it and its dependents (free vars etc)
434 addExternal (id,rhs) needed
435 = extendVarEnv (foldVarSet add_occ needed new_needed_ids)
438 add_occ id needed = extendVarEnv needed id False
439 -- "False" because we don't know we need the Id's unfolding
440 -- We'll override it later when we find the binding site
442 new_needed_ids = worker_ids `unionVarSet`
443 unfold_ids `unionVarSet`
447 dont_inline = isNeverActive (inlinePragInfo idinfo)
448 loop_breaker = isLoopBreaker (occInfo idinfo)
449 bottoming_fn = isBottomingSig (newStrictnessInfo idinfo `orElse` topSig)
450 spec_ids = specInfoFreeVars (specInfo idinfo)
451 worker_info = workerInfo idinfo
453 -- Stuff to do with the Id's unfolding
454 -- The simplifier has put an up-to-date unfolding
455 -- in the IdInfo, but the RHS will do just as well
456 unfolding = unfoldingInfo idinfo
457 rhs_is_small = not (neverUnfold unfolding)
459 -- We leave the unfolding there even if there is a worker
460 -- In GHCI the unfolding is used by importers
461 -- When writing an interface file, we omit the unfolding
462 -- if there is a worker
463 show_unfold = not bottoming_fn && -- Not necessary
466 rhs_is_small -- Small enough
468 unfold_ids | show_unfold = exprSomeFreeVars isLocalId rhs
469 | otherwise = emptyVarSet
471 worker_ids = case worker_info of
472 HasWorker work_id _ -> unitVarSet work_id
473 otherwise -> emptyVarSet
478 findExternalRules :: [CoreBind]
479 -> [CoreRule] -- Non-local rules (i.e. ones for imported fns)
480 -> IdEnv a -- Ids that are exported, so we need their rules
482 -- The complete rules are gotten by combining
483 -- a) the non-local rules
484 -- b) rules embedded in the top-level Ids
485 findExternalRules binds non_local_rules ext_ids
486 = filter (not . internal_rule) (non_local_rules ++ local_rules)
489 | id <- bindersOfBinds binds,
490 id `elemVarEnv` ext_ids,
491 rule <- idCoreRules id
495 = any internal_id (varSetElems (ruleLhsFreeIds rule))
496 -- Don't export a rule whose LHS mentions a locally-defined
497 -- Id that is completely internal (i.e. not visible to an
500 internal_id id = not (id `elemVarEnv` ext_ids)
505 %************************************************************************
507 \subsection{Step 2: top-level tidying}
509 %************************************************************************
513 -- TopTidyEnv: when tidying we need to know
514 -- * nc_var: The NameCache, containing a unique supply and any pre-ordained Names.
515 -- These may have arisen because the
516 -- renamer read in an interface file mentioning M.$wf, say,
517 -- and assigned it unique r77. If, on this compilation, we've
518 -- invented an Id whose name is $wf (but with a different unique)
519 -- we want to rename it to have unique r77, so that we can do easy
520 -- comparisons with stuff from the interface file
522 -- * occ_env: The TidyOccEnv, which tells us which local occurrences
525 -- * subst_env: A Var->Var mapping that substitutes the new Var for the old
527 tidyTopBinds :: HscEnv
530 -> IdEnv Bool -- Domain = Ids that should be external
531 -- True <=> their unfolding is external too
533 -> IO (TidyEnv, [CoreBind])
535 tidyTopBinds hsc_env mod type_env ext_ids binds
536 = tidy init_env binds
538 dflags = hsc_dflags hsc_env
539 nc_var = hsc_NC hsc_env
541 -- We also make sure to avoid any exported binders. Consider
542 -- f{-u1-} = 1 -- Local decl
544 -- f{-u2-} = 2 -- Exported decl
546 -- The second exported decl must 'get' the name 'f', so we
547 -- have to put 'f' in the avoids list before we get to the first
548 -- decl. tidyTopId then does a no-op on exported binders.
549 init_env = (initTidyOccEnv avoids, emptyVarEnv)
550 avoids = [getOccName name | bndr <- typeEnvIds type_env,
551 let name = idName bndr,
553 -- In computing our "avoids" list, we must include
555 -- all things with global names (assigned once and for
556 -- all by the renamer)
557 -- since their names are "taken".
558 -- The type environment is a convenient source of such things.
560 tidy env [] = return (env, [])
561 tidy env (b:bs) = do { (env1, b') <- tidyTopBind dflags mod nc_var ext_ids env b
562 ; (env2, bs') <- tidy env1 bs
563 ; return (env2, b':bs') }
565 ------------------------
566 tidyTopBind :: DynFlags
568 -> IORef NameCache -- For allocating new unique names
569 -> IdEnv Bool -- Domain = Ids that should be external
570 -- True <=> their unfolding is external too
571 -> TidyEnv -> CoreBind
572 -> IO (TidyEnv, CoreBind)
574 tidyTopBind dflags mod nc_var ext_ids tidy_env1@(occ_env1,subst1) (NonRec bndr rhs)
575 = do { (occ_env2, name') <- tidyTopName mod nc_var ext_ids occ_env1 bndr
576 ; let { (bndr', rhs') = tidyTopPair ext_ids tidy_env2 caf_info name' (bndr, rhs)
577 ; subst2 = extendVarEnv subst1 bndr bndr'
578 ; tidy_env2 = (occ_env2, subst2) }
579 ; return (tidy_env2, NonRec bndr' rhs') }
581 caf_info = hasCafRefs dflags subst1 (idArity bndr) rhs
583 tidyTopBind dflags mod nc_var ext_ids tidy_env1@(occ_env1,subst1) (Rec prs)
584 = do { (occ_env2, names') <- tidyTopNames mod nc_var ext_ids occ_env1 bndrs
585 ; let { prs' = zipWith (tidyTopPair ext_ids tidy_env2 caf_info)
587 ; subst2 = extendVarEnvList subst1 (bndrs `zip` map fst prs')
588 ; tidy_env2 = (occ_env2, subst2) }
589 ; return (tidy_env2, Rec prs') }
593 -- the CafInfo for a recursive group says whether *any* rhs in
594 -- the group may refer indirectly to a CAF (because then, they all do).
596 | or [ mayHaveCafRefs (hasCafRefs dflags subst1 (idArity bndr) rhs)
597 | (bndr,rhs) <- prs ] = MayHaveCafRefs
598 | otherwise = NoCafRefs
600 --------------------------------------------------------------------
602 -- This is where we set names to local/global based on whether they really are
603 -- externally visible (see comment at the top of this module). If the name
604 -- was previously local, we have to give it a unique occurrence name if
605 -- we intend to externalise it.
606 tidyTopNames mod nc_var ext_ids occ_env [] = return (occ_env, [])
607 tidyTopNames mod nc_var ext_ids occ_env (id:ids)
608 = do { (occ_env1, name) <- tidyTopName mod nc_var ext_ids occ_env id
609 ; (occ_env2, names) <- tidyTopNames mod nc_var ext_ids occ_env1 ids
610 ; return (occ_env2, name:names) }
612 tidyTopName :: Module -> IORef NameCache -> VarEnv Bool -> TidyOccEnv
613 -> Id -> IO (TidyOccEnv, Name)
614 tidyTopName mod nc_var ext_ids occ_env id
615 | global && internal = return (occ_env, localiseName name)
617 | global && external = return (occ_env, name)
618 -- Global names are assumed to have been allocated by the renamer,
619 -- so they already have the "right" unique
620 -- And it's a system-wide unique too
622 -- Now we get to the real reason that all this is in the IO Monad:
623 -- we have to update the name cache in a nice atomic fashion
625 | local && internal = do { nc <- readIORef nc_var
626 ; let (nc', new_local_name) = mk_new_local nc
627 ; writeIORef nc_var nc'
628 ; return (occ_env', new_local_name) }
629 -- Even local, internal names must get a unique occurrence, because
630 -- if we do -split-objs we externalise the name later, in the code generator
632 -- Similarly, we must make sure it has a system-wide Unique, because
633 -- the byte-code generator builds a system-wide Name->BCO symbol table
635 | local && external = do { nc <- readIORef nc_var
636 ; let (nc', new_external_name) = mk_new_external nc
637 ; writeIORef nc_var nc'
638 ; return (occ_env', new_external_name) }
641 external = id `elemVarEnv` ext_ids
642 global = isExternalName name
644 internal = not external
645 mb_parent = nameParent_maybe name
646 loc = nameSrcLoc name
648 (occ_env', occ') = tidyOccName occ_env (nameOccName name)
650 mk_new_local nc = (nc { nsUniqs = us2 }, mkInternalName uniq occ' loc)
652 (us1, us2) = splitUniqSupply (nsUniqs nc)
653 uniq = uniqFromSupply us1
655 mk_new_external nc = allocateGlobalBinder nc mod occ' mb_parent loc
656 -- If we want to externalise a currently-local name, check
657 -- whether we have already assigned a unique for it.
658 -- If so, use it; if not, extend the table.
659 -- All this is done by allcoateGlobalBinder.
660 -- This is needed when *re*-compiling a module in GHCi; we must
661 -- use the same name for externally-visible things as we did before.
664 -----------------------------------------------------------
665 tidyTopPair :: VarEnv Bool
666 -> TidyEnv -- The TidyEnv is used to tidy the IdInfo
667 -- It is knot-tied: don't look at it!
670 -> (Id, CoreExpr) -- Binder and RHS before tidying
672 -- This function is the heart of Step 2
673 -- The rec_tidy_env is the one to use for the IdInfo
674 -- It's necessary because when we are dealing with a recursive
675 -- group, a variable late in the group might be mentioned
676 -- in the IdInfo of one early in the group
678 tidyTopPair ext_ids rhs_tidy_env caf_info name' (bndr, rhs)
679 | isGlobalId bndr -- Injected binding for record selector, etc
680 = (bndr, tidyExpr rhs_tidy_env rhs)
684 bndr' = mkVanillaGlobal name' ty' idinfo'
685 ty' = tidyTopType (idType bndr)
686 rhs' = tidyExpr rhs_tidy_env rhs
687 idinfo' = tidyTopIdInfo rhs_tidy_env (isJust maybe_external)
688 (idInfo bndr) unfold_info arity
691 -- Expose an unfolding if ext_ids tells us to
692 -- Remember that ext_ids maps an Id to a Bool:
693 -- True to show the unfolding, False to hide it
694 maybe_external = lookupVarEnv ext_ids bndr
695 show_unfold = maybe_external `orElse` False
696 unfold_info | show_unfold = mkTopUnfolding rhs'
697 | otherwise = noUnfolding
699 -- Usually the Id will have an accurate arity on it, because
700 -- the simplifier has just run, but not always.
701 -- One case I found was when the last thing the simplifier
702 -- did was to let-bind a non-atomic argument and then float
703 -- it to the top level. So it seems more robust just to
705 arity = exprArity rhs
708 -- tidyTopIdInfo creates the final IdInfo for top-level
709 -- binders. There are two delicate pieces:
711 -- * Arity. After CoreTidy, this arity must not change any more.
712 -- Indeed, CorePrep must eta expand where necessary to make
713 -- the manifest arity equal to the claimed arity.
715 -- * CAF info. This must also remain valid through to code generation.
716 -- We add the info here so that it propagates to all
717 -- occurrences of the binders in RHSs, and hence to occurrences in
718 -- unfoldings, which are inside Ids imported by GHCi. Ditto RULES.
719 -- CoreToStg makes use of this when constructing SRTs.
721 tidyTopIdInfo tidy_env is_external idinfo unfold_info arity caf_info
722 | not is_external -- For internal Ids (not externally visible)
723 = vanillaIdInfo -- we only need enough info for code generation
724 -- Arity and strictness info are enough;
725 -- c.f. CoreTidy.tidyLetBndr
726 `setCafInfo` caf_info
728 `setAllStrictnessInfo` newStrictnessInfo idinfo
730 | otherwise -- Externally-visible Ids get the whole lot
732 `setCafInfo` caf_info
734 `setAllStrictnessInfo` newStrictnessInfo idinfo
735 `setInlinePragInfo` inlinePragInfo idinfo
736 `setUnfoldingInfo` unfold_info
737 `setWorkerInfo` tidyWorker tidy_env (workerInfo idinfo)
738 -- NB: we throw away the Rules
739 -- They have already been extracted by findExternalRules
743 ------------ Worker --------------
744 tidyWorker tidy_env (HasWorker work_id wrap_arity)
745 = HasWorker (tidyVarOcc tidy_env work_id) wrap_arity
746 tidyWorker tidy_env other
750 %************************************************************************
752 \subsection{Figuring out CafInfo for an expression}
754 %************************************************************************
756 hasCafRefs decides whether a top-level closure can point into the dynamic heap.
757 We mark such things as `MayHaveCafRefs' because this information is
758 used to decide whether a particular closure needs to be referenced
761 There are two reasons for setting MayHaveCafRefs:
762 a) The RHS is a CAF: a top-level updatable thunk.
763 b) The RHS refers to something that MayHaveCafRefs
765 Possible improvement: In an effort to keep the number of CAFs (and
766 hence the size of the SRTs) down, we could also look at the expression and
767 decide whether it requires a small bounded amount of heap, so we can ignore
768 it as a CAF. In these cases however, we would need to use an additional
769 CAF list to keep track of non-collectable CAFs.
772 hasCafRefs :: DynFlags -> VarEnv Var -> Arity -> CoreExpr -> CafInfo
773 hasCafRefs dflags p arity expr
774 | is_caf || mentions_cafs = MayHaveCafRefs
775 | otherwise = NoCafRefs
777 mentions_cafs = isFastTrue (cafRefs p expr)
778 is_caf = not (arity > 0 || rhsIsStatic dflags expr)
779 -- NB. we pass in the arity of the expression, which is expected
780 -- to be calculated by exprArity. This is because exprArity
781 -- knows how much eta expansion is going to be done by
782 -- CorePrep later on, and we don't want to duplicate that
783 -- knowledge in rhsIsStatic below.
786 -- imported Ids first:
787 | not (isLocalId id) = fastBool (mayHaveCafRefs (idCafInfo id))
788 -- now Ids local to this module:
790 case lookupVarEnv p id of
791 Just id' -> fastBool (mayHaveCafRefs (idCafInfo id'))
792 Nothing -> fastBool False
794 cafRefs p (Lit l) = fastBool False
795 cafRefs p (App f a) = fastOr (cafRefs p f) (cafRefs p) a
796 cafRefs p (Lam x e) = cafRefs p e
797 cafRefs p (Let b e) = fastOr (cafRefss p (rhssOfBind b)) (cafRefs p) e
798 cafRefs p (Case e bndr _ alts) = fastOr (cafRefs p e) (cafRefss p) (rhssOfAlts alts)
799 cafRefs p (Note n e) = cafRefs p e
800 cafRefs p (Type t) = fastBool False
802 cafRefss p [] = fastBool False
803 cafRefss p (e:es) = fastOr (cafRefs p e) (cafRefss p) es
805 -- hack for lazy-or over FastBool.
806 fastOr a f x = fastBool (isFastTrue a || isFastTrue (f x))