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 ( DynFlag(..), DynFlags(..), 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, isNaughtyRecordSelector,
24 idArity, idCafInfo, idUnfolding, isImplicitId, setIdInfo,
27 import IdInfo {- loads of stuff -}
28 import InstEnv ( Instance, DFunId, instanceDFunId, setInstanceDFunId )
29 import NewDemand ( isBottomingSig, topSig )
30 import BasicTypes ( Arity, isNeverActive, isNonRuleLoopBreaker )
31 import Name ( Name, getOccName, nameOccName, mkInternalName,
32 localiseName, isExternalName, nameSrcLoc,
33 isWiredInName, getName
35 import NameSet ( NameSet, elemNameSet )
36 import IfaceEnv ( allocateGlobalBinder )
37 import NameEnv ( filterNameEnv, mapNameEnv )
38 import OccName ( TidyOccEnv, initTidyOccEnv, tidyOccName )
39 import Type ( tidyTopType )
40 import TcType ( isFFITy )
41 import DataCon ( dataConName, dataConFieldLabels, dataConWrapId_maybe )
42 import TyCon ( TyCon, makeTyConAbstract, tyConDataCons, isNewTyCon,
43 newTyConRep, tyConSelIds, isAlgTyCon,
44 isEnumerationTyCon, isOpenTyCon )
45 import Class ( classSelIds )
46 import Module ( Module )
48 import Maybes ( orElse, mapCatMaybes )
49 import ErrUtils ( showPass, dumpIfSet_core )
50 import PackageConfig ( PackageId )
51 import UniqSupply ( splitUniqSupply, uniqFromSupply )
53 import FastTypes hiding ( fastOr )
55 import Data.List ( partition )
56 import Data.Maybe ( isJust )
57 import Data.IORef ( IORef, readIORef, writeIORef )
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
125 , mg_types = type_env
127 , mg_fam_insts = fam_insts,
128 mg_dbg_sites = sites })
129 = do { let dflags = hsc_dflags hsc_env
130 ; showPass dflags "Tidy [hoot] type env"
132 ; let { insts' = tidyInstances tidyExternalId insts
133 ; type_env1 = filterNameEnv (not . isWiredInThing) type_env
134 ; type_env2 = mapNameEnv tidyBootThing type_env1
135 ; type_env' = extendTypeEnvWithIds type_env2
136 (map instanceDFunId insts')
138 ; return (ModDetails { md_types = type_env'
140 , md_fam_insts = fam_insts
142 , md_exports = exports
143 , md_dbg_sites = sites})
147 isWiredInThing :: TyThing -> Bool
148 isWiredInThing thing = isWiredInName (getName thing)
150 tidyBootThing :: TyThing -> TyThing
151 -- Just externalise the Ids; keep everything
152 tidyBootThing (AnId id) | isLocalId id = AnId (tidyExternalId id)
153 tidyBootThing thing = thing
155 tidyExternalId :: Id -> Id
156 -- Takes an LocalId with an External Name,
157 -- makes it into a GlobalId with VanillaIdInfo, and tidies its type
158 -- (NB: vanillaIdInfo makes a conservative assumption about Caf-hood.)
160 = ASSERT2( isLocalId id && isExternalName (idName id), ppr id )
161 mkVanillaGlobal (idName id) (tidyTopType (idType id)) vanillaIdInfo
165 %************************************************************************
167 Plan B: tidy bindings, make TypeEnv full of IdInfo
169 %************************************************************************
171 Plan B: include pragmas, make interfaces
172 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
173 * Figure out which Ids are externally visible
175 * Tidy the bindings, externalising appropriate Ids
177 * Drop all Ids from the TypeEnv, and add all the External Ids from
178 the bindings. (This adds their IdInfo to the TypeEnv; and adds
179 floated-out Ids that weren't even in the TypeEnv before.)
181 Step 1: Figure out external Ids
182 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
183 First we figure out which Ids are "external" Ids. An
184 "external" Id is one that is visible from outside the compilation
186 a) the user exported ones
187 b) ones mentioned in the unfoldings, workers,
188 or rules of externally-visible ones
189 This exercise takes a sweep of the bindings bottom to top. Actually,
190 in Step 2 we're also going to need to know which Ids should be
191 exported with their unfoldings, so we produce not an IdSet but an
195 Step 2: Tidy the program
196 ~~~~~~~~~~~~~~~~~~~~~~~~
197 Next we traverse the bindings top to bottom. For each *top-level*
200 1. Make it into a GlobalId; its IdDetails becomes VanillaGlobal,
201 reflecting the fact that from now on we regard it as a global,
204 2. Give it a system-wide Unique.
205 [Even non-exported things need system-wide Uniques because the
206 byte-code generator builds a single Name->BCO symbol table.]
208 We use the NameCache kept in the HscEnv as the
209 source of such system-wide uniques.
211 For external Ids, use the original-name cache in the NameCache
212 to ensure that the unique assigned is the same as the Id had
213 in any previous compilation run.
215 3. If it's an external Id, make it have a External Name, otherwise
216 make it have an Internal Name.
217 This is used by the code generator to decide whether
218 to make the label externally visible
220 4. Give external Ids a "tidy" OccName. This means
221 we can print them in interface files without confusing
222 "x" (unique 5) with "x" (unique 10).
224 5. Give it its UTTERLY FINAL IdInfo; in ptic,
225 * its unfolding, if it should have one
227 * its arity, computed from the number of visible lambdas
229 * its CAF info, computed from what is free in its RHS
232 Finally, substitute these new top-level binders consistently
233 throughout, including in unfoldings. We also tidy binders in
234 RHSs, so that they print nicely in interfaces.
237 tidyProgram :: HscEnv -> ModGuts -> IO (CgGuts, ModDetails)
239 mod_impl@(ModGuts { mg_module = mod, mg_exports = exports,
241 mg_insts = insts, mg_fam_insts = fam_insts,
243 mg_rules = imp_rules,
244 mg_dir_imps = dir_imps, mg_deps = deps,
245 mg_foreign = foreign_stubs,
246 mg_hpc_info = hpc_info,
247 mg_dbg_sites = sites })
249 = do { let dflags = hsc_dflags hsc_env
250 ; showPass dflags "Tidy Core"
252 ; let { omit_prags = dopt Opt_OmitInterfacePragmas dflags
253 ; ext_ids = findExternalIds omit_prags binds
256 | otherwise = findExternalRules binds imp_rules ext_ids
257 -- findExternalRules filters imp_rules to avoid binders that
258 -- aren't externally visible; but the externally-visible binders
259 -- are computed (by findExternalIds) assuming that all orphan
260 -- rules are exported (they get their Exported flag set in the desugarer)
261 -- So in fact we may export more than we need.
262 -- (It's a sort of mutual recursion.)
265 ; (tidy_env, tidy_binds) <- tidyTopBinds hsc_env mod type_env ext_ids
268 ; let { export_set = availsToNameSet exports
269 ; tidy_type_env = tidyTypeEnv omit_prags export_set type_env
271 ; tidy_insts = tidyInstances (lookup_dfun tidy_type_env) insts
272 -- A DFunId will have a binding in tidy_binds, and so
273 -- will now be in final_env, replete with IdInfo
274 -- Its name will be unchanged since it was born, but
275 -- we want Global, IdInfo-rich (or not) DFunId in the
278 ; tidy_rules = tidyRules tidy_env ext_rules
279 -- You might worry that the tidy_env contains IdInfo-rich stuff
280 -- and indeed it does, but if omit_prags is on, ext_rules is
283 ; implicit_binds = getImplicitBinds type_env
284 ; all_tidy_binds = implicit_binds ++ tidy_binds
285 ; alg_tycons = filter isAlgTyCon (typeEnvTyCons type_env)
288 ; endPass dflags "Tidy Core" Opt_D_dump_simpl all_tidy_binds
289 ; dumpIfSet_core dflags Opt_D_dump_simpl
291 (pprRules tidy_rules)
293 ; return (CgGuts { cg_module = mod,
294 cg_tycons = alg_tycons,
295 cg_binds = all_tidy_binds,
296 cg_dir_imps = dir_imps,
297 cg_foreign = foreign_stubs,
298 cg_dep_pkgs = dep_pkgs deps,
299 cg_hpc_info = hpc_info },
301 ModDetails { md_types = tidy_type_env,
302 md_rules = tidy_rules,
303 md_insts = tidy_insts,
304 md_fam_insts = fam_insts,
305 md_exports = exports,
306 md_dbg_sites = sites })
309 lookup_dfun type_env dfun_id
310 = case lookupTypeEnv type_env (idName dfun_id) of
311 Just (AnId dfun_id') -> dfun_id'
312 other -> pprPanic "lookup_dfun" (ppr dfun_id)
314 tidyTypeEnv :: Bool -> NameSet -> TypeEnv -> [CoreBind] -> TypeEnv
316 -- The competed type environment is gotten from
317 -- Dropping any wired-in things, and then
318 -- a) keeping the types and classes
319 -- b) removing all Ids,
320 -- c) adding Ids with correct IdInfo, including unfoldings,
321 -- gotten from the bindings
322 -- From (c) we keep only those Ids with External names;
323 -- the CoreTidy pass makes sure these are all and only
324 -- the externally-accessible ones
325 -- This truncates the type environment to include only the
326 -- exported Ids and things needed from them, which saves space
328 tidyTypeEnv omit_prags exports type_env tidy_binds
329 = let type_env1 = filterNameEnv keep_it type_env
330 type_env2 = extendTypeEnvWithIds type_env1 final_ids
331 type_env3 | omit_prags = mapNameEnv trim_thing type_env2
332 | otherwise = type_env2
336 final_ids = [ id | id <- bindersOfBinds tidy_binds,
337 isExternalName (idName id)]
339 -- We keep GlobalIds, because they won't appear
340 -- in the bindings from which final_ids are derived!
341 -- (The bindings bind LocalIds.)
342 keep_it thing | isWiredInThing thing = False
343 keep_it (AnId id) = isGlobalId id -- Keep GlobalIds (e.g. class ops)
344 keep_it other = True -- Keep all TyCons, DataCons, and Classes
348 ATyCon tc | mustExposeTyCon exports tc -> thing
349 | otherwise -> ATyCon (makeTyConAbstract tc)
351 AnId id | isImplicitId id -> thing
352 | otherwise -> AnId (id `setIdInfo` vanillaIdInfo)
356 mustExposeTyCon :: NameSet -- Exports
357 -> TyCon -- The tycon
358 -> Bool -- Can its rep be hidden?
359 -- We are compiling without -O, and thus trying to write as little as
360 -- possible into the interface file. But we must expose the details of
361 -- any data types whose constructors or fields are exported
362 mustExposeTyCon exports tc
363 | not (isAlgTyCon tc) -- Synonyms
365 | isEnumerationTyCon tc -- For an enumeration, exposing the constructors
366 = True -- won't lead to the need for further exposure
367 -- (This includes data types with no constructors.)
368 | isOpenTyCon tc -- open type family
370 | otherwise -- Newtype, datatype
371 = any exported_con (tyConDataCons tc)
372 -- Expose rep if any datacon or field is exported
374 || (isNewTyCon tc && isFFITy (snd (newTyConRep tc)))
375 -- Expose the rep for newtypes if the rep is an FFI type.
376 -- For a very annoying reason. 'Foreign import' is meant to
377 -- be able to look through newtypes transparently, but it
378 -- can only do that if it can "see" the newtype representation
380 exported_con con = any (`elemNameSet` exports)
381 (dataConName con : dataConFieldLabels con)
383 tidyInstances :: (DFunId -> DFunId) -> [Instance] -> [Instance]
384 tidyInstances tidy_dfun ispecs
387 tidy ispec = setInstanceDFunId ispec $
388 tidy_dfun (instanceDFunId ispec)
390 getImplicitBinds :: TypeEnv -> [CoreBind]
391 getImplicitBinds type_env
392 = map get_defn (concatMap implicit_con_ids (typeEnvTyCons type_env)
393 ++ concatMap other_implicit_ids (typeEnvElts type_env))
394 -- Put the constructor wrappers first, because
395 -- other implicit bindings (notably the fromT functions arising
396 -- from generics) use the constructor wrappers. At least that's
397 -- what External Core likes
399 implicit_con_ids tc = mapCatMaybes dataConWrapId_maybe (tyConDataCons tc)
401 other_implicit_ids (ATyCon tc) = filter (not . isNaughtyRecordSelector) (tyConSelIds tc)
402 -- The "naughty" ones are not real functions at all
403 -- They are there just so we can get decent error messages
404 -- See Note [Naughty record selectors] in MkId.lhs
405 other_implicit_ids (AClass cl) = classSelIds cl
406 other_implicit_ids other = []
408 get_defn :: Id -> CoreBind
409 get_defn id = NonRec id (tidyExpr emptyTidyEnv rhs)
411 rhs = unfoldingTemplate (idUnfolding id)
412 -- Don't forget to tidy the body ! Otherwise you get silly things like
413 -- \ tpl -> case tpl of tpl -> (tpl,tpl) -> tpl
417 %************************************************************************
419 \subsection{Step 1: finding externals}
421 %************************************************************************
424 findExternalIds :: Bool
426 -> IdEnv Bool -- In domain => external
427 -- Range = True <=> show unfolding
428 -- Step 1 from the notes above
429 findExternalIds omit_prags binds
431 = mkVarEnv [ (id,False) | id <- bindersOfBinds binds, isExportedId id ]
434 = foldr find emptyVarEnv binds
436 find (NonRec id rhs) needed
437 | need_id needed id = addExternal (id,rhs) needed
439 find (Rec prs) needed = find_prs prs needed
441 -- For a recursive group we have to look for a fixed point
443 | null needed_prs = needed
444 | otherwise = find_prs other_prs new_needed
446 (needed_prs, other_prs) = partition (need_pr needed) prs
447 new_needed = foldr addExternal needed needed_prs
449 -- The 'needed' set contains the Ids that are needed by earlier
450 -- interface file emissions. If the Id isn't in this set, and isn't
451 -- exported, there's no need to emit anything
452 need_id needed_set id = id `elemVarEnv` needed_set || isExportedId id
453 need_pr needed_set (id,rhs) = need_id needed_set id
455 addExternal :: (Id,CoreExpr) -> IdEnv Bool -> IdEnv Bool
456 -- The Id is needed; extend the needed set
457 -- with it and its dependents (free vars etc)
458 addExternal (id,rhs) needed
459 = extendVarEnv (foldVarSet add_occ needed new_needed_ids)
462 add_occ id needed | id `elemVarEnv` needed = needed
463 | otherwise = extendVarEnv needed id False
464 -- "False" because we don't know we need the Id's unfolding
465 -- Don't override existing bindings; we might have already set it to True
467 new_needed_ids = worker_ids `unionVarSet`
468 unfold_ids `unionVarSet`
472 dont_inline = isNeverActive (inlinePragInfo idinfo)
473 loop_breaker = isNonRuleLoopBreaker (occInfo idinfo)
474 bottoming_fn = isBottomingSig (newStrictnessInfo idinfo `orElse` topSig)
475 spec_ids = specInfoFreeVars (specInfo idinfo)
476 worker_info = workerInfo idinfo
478 -- Stuff to do with the Id's unfolding
479 -- The simplifier has put an up-to-date unfolding
480 -- in the IdInfo, but the RHS will do just as well
481 unfolding = unfoldingInfo idinfo
482 rhs_is_small = not (neverUnfold unfolding)
484 -- We leave the unfolding there even if there is a worker
485 -- In GHCI the unfolding is used by importers
486 -- When writing an interface file, we omit the unfolding
487 -- if there is a worker
488 show_unfold = not bottoming_fn && -- Not necessary
491 rhs_is_small -- Small enough
493 unfold_ids | show_unfold = exprSomeFreeVars isLocalId rhs
494 | otherwise = emptyVarSet
496 worker_ids = case worker_info of
497 HasWorker work_id _ -> unitVarSet work_id
498 otherwise -> emptyVarSet
503 findExternalRules :: [CoreBind]
504 -> [CoreRule] -- Non-local rules (i.e. ones for imported fns)
505 -> IdEnv a -- Ids that are exported, so we need their rules
507 -- The complete rules are gotten by combining
508 -- a) the non-local rules
509 -- b) rules embedded in the top-level Ids
510 findExternalRules binds non_local_rules ext_ids
511 = filter (not . internal_rule) (non_local_rules ++ local_rules)
514 | id <- bindersOfBinds binds,
515 id `elemVarEnv` ext_ids,
516 rule <- idCoreRules id
520 = any internal_id (varSetElems (ruleLhsFreeIds rule))
521 -- Don't export a rule whose LHS mentions a locally-defined
522 -- Id that is completely internal (i.e. not visible to an
525 internal_id id = not (id `elemVarEnv` ext_ids)
530 %************************************************************************
532 \subsection{Step 2: top-level tidying}
534 %************************************************************************
538 -- TopTidyEnv: when tidying we need to know
539 -- * nc_var: The NameCache, containing a unique supply and any pre-ordained Names.
540 -- These may have arisen because the
541 -- renamer read in an interface file mentioning M.$wf, say,
542 -- and assigned it unique r77. If, on this compilation, we've
543 -- invented an Id whose name is $wf (but with a different unique)
544 -- we want to rename it to have unique r77, so that we can do easy
545 -- comparisons with stuff from the interface file
547 -- * occ_env: The TidyOccEnv, which tells us which local occurrences
550 -- * subst_env: A Var->Var mapping that substitutes the new Var for the old
552 tidyTopBinds :: HscEnv
555 -> IdEnv Bool -- Domain = Ids that should be external
556 -- True <=> their unfolding is external too
558 -> IO (TidyEnv, [CoreBind])
560 tidyTopBinds hsc_env mod type_env ext_ids binds
561 = tidy init_env binds
563 nc_var = hsc_NC hsc_env
565 -- We also make sure to avoid any exported binders. Consider
566 -- f{-u1-} = 1 -- Local decl
568 -- f{-u2-} = 2 -- Exported decl
570 -- The second exported decl must 'get' the name 'f', so we
571 -- have to put 'f' in the avoids list before we get to the first
572 -- decl. tidyTopId then does a no-op on exported binders.
573 init_env = (initTidyOccEnv avoids, emptyVarEnv)
574 avoids = [getOccName name | bndr <- typeEnvIds type_env,
575 let name = idName bndr,
577 -- In computing our "avoids" list, we must include
579 -- all things with global names (assigned once and for
580 -- all by the renamer)
581 -- since their names are "taken".
582 -- The type environment is a convenient source of such things.
584 this_pkg = thisPackage (hsc_dflags hsc_env)
586 tidy env [] = return (env, [])
587 tidy env (b:bs) = do { (env1, b') <- tidyTopBind this_pkg mod nc_var ext_ids env b
588 ; (env2, bs') <- tidy env1 bs
589 ; return (env2, b':bs') }
591 ------------------------
592 tidyTopBind :: PackageId
594 -> IORef NameCache -- For allocating new unique names
595 -> IdEnv Bool -- Domain = Ids that should be external
596 -- True <=> their unfolding is external too
597 -> TidyEnv -> CoreBind
598 -> IO (TidyEnv, CoreBind)
600 tidyTopBind this_pkg mod nc_var ext_ids tidy_env1@(occ_env1,subst1) (NonRec bndr rhs)
601 = do { (occ_env2, name') <- tidyTopName mod nc_var ext_ids occ_env1 bndr
602 ; let { (bndr', rhs') = tidyTopPair ext_ids tidy_env2 caf_info name' (bndr, rhs)
603 ; subst2 = extendVarEnv subst1 bndr bndr'
604 ; tidy_env2 = (occ_env2, subst2) }
605 ; return (tidy_env2, NonRec bndr' rhs') }
607 caf_info = hasCafRefs this_pkg subst1 (idArity bndr) rhs
609 tidyTopBind this_pkg mod nc_var ext_ids tidy_env1@(occ_env1,subst1) (Rec prs)
610 = do { (occ_env2, names') <- tidyTopNames mod nc_var ext_ids occ_env1 bndrs
611 ; let { prs' = zipWith (tidyTopPair ext_ids tidy_env2 caf_info)
613 ; subst2 = extendVarEnvList subst1 (bndrs `zip` map fst prs')
614 ; tidy_env2 = (occ_env2, subst2) }
615 ; return (tidy_env2, Rec prs') }
619 -- the CafInfo for a recursive group says whether *any* rhs in
620 -- the group may refer indirectly to a CAF (because then, they all do).
622 | or [ mayHaveCafRefs (hasCafRefs this_pkg subst1 (idArity bndr) rhs)
623 | (bndr,rhs) <- prs ] = MayHaveCafRefs
624 | otherwise = NoCafRefs
626 --------------------------------------------------------------------
628 -- This is where we set names to local/global based on whether they really are
629 -- externally visible (see comment at the top of this module). If the name
630 -- was previously local, we have to give it a unique occurrence name if
631 -- we intend to externalise it.
632 tidyTopNames mod nc_var ext_ids occ_env [] = return (occ_env, [])
633 tidyTopNames mod nc_var ext_ids occ_env (id:ids)
634 = do { (occ_env1, name) <- tidyTopName mod nc_var ext_ids occ_env id
635 ; (occ_env2, names) <- tidyTopNames mod nc_var ext_ids occ_env1 ids
636 ; return (occ_env2, name:names) }
638 tidyTopName :: Module -> IORef NameCache -> VarEnv Bool -> TidyOccEnv
639 -> Id -> IO (TidyOccEnv, Name)
640 tidyTopName mod nc_var ext_ids occ_env id
641 | global && internal = return (occ_env, localiseName name)
643 | global && external = return (occ_env, name)
644 -- Global names are assumed to have been allocated by the renamer,
645 -- so they already have the "right" unique
646 -- And it's a system-wide unique too
648 -- Now we get to the real reason that all this is in the IO Monad:
649 -- we have to update the name cache in a nice atomic fashion
651 | local && internal = do { nc <- readIORef nc_var
652 ; let (nc', new_local_name) = mk_new_local nc
653 ; writeIORef nc_var nc'
654 ; return (occ_env', new_local_name) }
655 -- Even local, internal names must get a unique occurrence, because
656 -- if we do -split-objs we externalise the name later, in the code generator
658 -- Similarly, we must make sure it has a system-wide Unique, because
659 -- the byte-code generator builds a system-wide Name->BCO symbol table
661 | local && external = do { nc <- readIORef nc_var
662 ; let (nc', new_external_name) = mk_new_external nc
663 ; writeIORef nc_var nc'
664 ; return (occ_env', new_external_name) }
667 external = id `elemVarEnv` ext_ids
668 global = isExternalName name
670 internal = not external
671 loc = nameSrcLoc name
673 (occ_env', occ') = tidyOccName occ_env (nameOccName name)
675 mk_new_local nc = (nc { nsUniqs = us2 }, mkInternalName uniq occ' loc)
677 (us1, us2) = splitUniqSupply (nsUniqs nc)
678 uniq = uniqFromSupply us1
680 mk_new_external nc = allocateGlobalBinder nc mod occ' loc
681 -- If we want to externalise a currently-local name, check
682 -- whether we have already assigned a unique for it.
683 -- If so, use it; if not, extend the table.
684 -- All this is done by allcoateGlobalBinder.
685 -- This is needed when *re*-compiling a module in GHCi; we must
686 -- use the same name for externally-visible things as we did before.
689 -----------------------------------------------------------
690 tidyTopPair :: VarEnv Bool
691 -> TidyEnv -- The TidyEnv is used to tidy the IdInfo
692 -- It is knot-tied: don't look at it!
695 -> (Id, CoreExpr) -- Binder and RHS before tidying
697 -- This function is the heart of Step 2
698 -- The rec_tidy_env is the one to use for the IdInfo
699 -- It's necessary because when we are dealing with a recursive
700 -- group, a variable late in the group might be mentioned
701 -- in the IdInfo of one early in the group
703 tidyTopPair ext_ids rhs_tidy_env caf_info name' (bndr, rhs)
704 | isGlobalId bndr -- Injected binding for record selector, etc
705 = (bndr, tidyExpr rhs_tidy_env rhs)
709 bndr' = mkVanillaGlobal name' ty' idinfo'
710 ty' = tidyTopType (idType bndr)
711 rhs' = tidyExpr rhs_tidy_env rhs
712 idinfo' = tidyTopIdInfo rhs_tidy_env (isJust maybe_external)
713 (idInfo bndr) unfold_info arity
716 -- Expose an unfolding if ext_ids tells us to
717 -- Remember that ext_ids maps an Id to a Bool:
718 -- True to show the unfolding, False to hide it
719 maybe_external = lookupVarEnv ext_ids bndr
720 show_unfold = maybe_external `orElse` False
721 unfold_info | show_unfold = mkTopUnfolding rhs'
722 | otherwise = noUnfolding
724 -- Usually the Id will have an accurate arity on it, because
725 -- the simplifier has just run, but not always.
726 -- One case I found was when the last thing the simplifier
727 -- did was to let-bind a non-atomic argument and then float
728 -- it to the top level. So it seems more robust just to
730 arity = exprArity rhs
733 -- tidyTopIdInfo creates the final IdInfo for top-level
734 -- binders. There are two delicate pieces:
736 -- * Arity. After CoreTidy, this arity must not change any more.
737 -- Indeed, CorePrep must eta expand where necessary to make
738 -- the manifest arity equal to the claimed arity.
740 -- * CAF info. This must also remain valid through to code generation.
741 -- We add the info here so that it propagates to all
742 -- occurrences of the binders in RHSs, and hence to occurrences in
743 -- unfoldings, which are inside Ids imported by GHCi. Ditto RULES.
744 -- CoreToStg makes use of this when constructing SRTs.
746 tidyTopIdInfo tidy_env is_external idinfo unfold_info arity caf_info
747 | not is_external -- For internal Ids (not externally visible)
748 = vanillaIdInfo -- we only need enough info for code generation
749 -- Arity and strictness info are enough;
750 -- c.f. CoreTidy.tidyLetBndr
751 `setCafInfo` caf_info
753 `setAllStrictnessInfo` newStrictnessInfo idinfo
755 | otherwise -- Externally-visible Ids get the whole lot
757 `setCafInfo` caf_info
759 `setAllStrictnessInfo` newStrictnessInfo idinfo
760 `setInlinePragInfo` inlinePragInfo idinfo
761 `setUnfoldingInfo` unfold_info
762 `setWorkerInfo` tidyWorker tidy_env (workerInfo idinfo)
763 -- NB: we throw away the Rules
764 -- They have already been extracted by findExternalRules
768 ------------ Worker --------------
769 tidyWorker tidy_env (HasWorker work_id wrap_arity)
770 = HasWorker (tidyVarOcc tidy_env work_id) wrap_arity
771 tidyWorker tidy_env other
775 %************************************************************************
777 \subsection{Figuring out CafInfo for an expression}
779 %************************************************************************
781 hasCafRefs decides whether a top-level closure can point into the dynamic heap.
782 We mark such things as `MayHaveCafRefs' because this information is
783 used to decide whether a particular closure needs to be referenced
786 There are two reasons for setting MayHaveCafRefs:
787 a) The RHS is a CAF: a top-level updatable thunk.
788 b) The RHS refers to something that MayHaveCafRefs
790 Possible improvement: In an effort to keep the number of CAFs (and
791 hence the size of the SRTs) down, we could also look at the expression and
792 decide whether it requires a small bounded amount of heap, so we can ignore
793 it as a CAF. In these cases however, we would need to use an additional
794 CAF list to keep track of non-collectable CAFs.
797 hasCafRefs :: PackageId -> VarEnv Var -> Arity -> CoreExpr -> CafInfo
798 hasCafRefs this_pkg p arity expr
799 | is_caf || mentions_cafs
801 | otherwise = NoCafRefs
803 mentions_cafs = isFastTrue (cafRefs p expr)
804 is_caf = not (arity > 0 || rhsIsStatic this_pkg expr)
806 -- NB. we pass in the arity of the expression, which is expected
807 -- to be calculated by exprArity. This is because exprArity
808 -- knows how much eta expansion is going to be done by
809 -- CorePrep later on, and we don't want to duplicate that
810 -- knowledge in rhsIsStatic below.
813 -- imported Ids first:
814 | not (isLocalId id) = fastBool (mayHaveCafRefs (idCafInfo id))
815 -- now Ids local to this module:
817 case lookupVarEnv p id of
818 Just id' -> fastBool (mayHaveCafRefs (idCafInfo id'))
819 Nothing -> fastBool False
821 cafRefs p (Lit l) = fastBool False
822 cafRefs p (App f a) = fastOr (cafRefs p f) (cafRefs p) a
823 cafRefs p (Lam x e) = cafRefs p e
824 cafRefs p (Let b e) = fastOr (cafRefss p (rhssOfBind b)) (cafRefs p) e
825 cafRefs p (Case e bndr _ alts) = fastOr (cafRefs p e) (cafRefss p) (rhssOfAlts alts)
826 cafRefs p (Note n e) = cafRefs p e
827 cafRefs p (Cast e co) = cafRefs p e
828 cafRefs p (Type t) = fastBool False
830 cafRefss p [] = fastBool False
831 cafRefss p (e:es) = fastOr (cafRefs p e) (cafRefss p) es
833 -- hack for lazy-or over FastBool.
834 fastOr a f x = fastBool (isFastTrue a || isFastTrue (f x))