2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section{Tidying up Core}
7 module TidyPgm( mkBootModDetailsDs, mkBootModDetailsTc, tidyProgram ) where
9 #include "HsVersions.h"
43 import FastBool hiding ( fastOr )
45 import Data.List ( partition )
46 import Data.Maybe ( isJust )
47 import Data.IORef ( IORef, readIORef, writeIORef )
51 Constructing the TypeEnv, Instances, Rules from which the ModIface is
52 constructed, and which goes on to subsequent modules in --make mode.
54 Most of the interface file is obtained simply by serialising the
55 TypeEnv. One important consequence is that if the *interface file*
56 has pragma info if and only if the final TypeEnv does. This is not so
57 important for *this* module, but it's essential for ghc --make:
58 subsequent compilations must not see (e.g.) the arity if the interface
59 file does not contain arity If they do, they'll exploit the arity;
60 then the arity might change, but the iface file doesn't change =>
61 recompilation does not happen => disaster.
63 For data types, the final TypeEnv will have a TyThing for the TyCon,
64 plus one for each DataCon; the interface file will contain just one
65 data type declaration, but it is de-serialised back into a collection
68 %************************************************************************
72 %************************************************************************
75 Plan A: mkBootModDetails: omit pragmas, make interfaces small
76 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
79 * Drop all WiredIn things from the TypeEnv
80 (we never want them in interface files)
82 * Retain all TyCons and Classes in the TypeEnv, to avoid
83 having to find which ones are mentioned in the
86 * Trim off the constructors of non-exported TyCons, both
87 from the TyCon and from the TypeEnv
89 * Drop non-exported Ids from the TypeEnv
91 * Tidy the types of the DFunIds of Instances,
92 make them into GlobalIds, (they already have External Names)
93 and add them to the TypeEnv
95 * Tidy the types of the (exported) Ids in the TypeEnv,
96 make them into GlobalIds (they already have External Names)
98 * Drop rules altogether
100 * Tidy the bindings, to ensure that the Caf and Arity
101 information is correct for each top-level binder; the
102 code generator needs it. And to ensure that local names have
103 distinct OccNames in case of object-file splitting
106 -- This is Plan A: make a small type env when typechecking only,
107 -- or when compiling a hs-boot file, or simply when not using -O
109 -- We don't look at the bindings at all -- there aren't any
112 mkBootModDetailsTc :: HscEnv -> TcGblEnv -> IO ModDetails
113 mkBootModDetailsTc hsc_env
114 TcGblEnv{ tcg_exports = exports,
115 tcg_type_env = type_env,
117 tcg_fam_insts = fam_insts
119 = mkBootModDetails hsc_env exports type_env insts fam_insts
121 mkBootModDetailsDs :: HscEnv -> ModGuts -> IO ModDetails
122 mkBootModDetailsDs hsc_env
123 ModGuts{ mg_exports = exports,
126 mg_fam_insts = fam_insts
128 = mkBootModDetails hsc_env exports type_env insts fam_insts
130 mkBootModDetails :: HscEnv -> [AvailInfo] -> NameEnv TyThing
131 -> [Instance] -> [FamInstEnv.FamInst] -> IO ModDetails
132 mkBootModDetails hsc_env exports type_env insts fam_insts
133 = do { let dflags = hsc_dflags hsc_env
134 ; showPass dflags "Tidy [hoot] type env"
136 ; let { insts' = tidyInstances tidyExternalId insts
137 ; dfun_ids = map instanceDFunId insts'
138 ; type_env1 = tidyBootTypeEnv (availsToNameSet exports) type_env
139 ; type_env' = extendTypeEnvWithIds type_env1 dfun_ids
141 ; return (ModDetails { md_types = type_env'
143 , md_fam_insts = fam_insts
146 , md_exports = exports
147 , md_vect_info = noVectInfo
152 tidyBootTypeEnv :: NameSet -> TypeEnv -> TypeEnv
153 tidyBootTypeEnv exports type_env
154 = tidyTypeEnv True False exports type_env final_ids
156 -- Find the LocalIds in the type env that are exported
157 -- Make them into GlobalIds, and tidy their types
159 -- It's very important to remove the non-exported ones
160 -- because we don't tidy the OccNames, and if we don't remove
161 -- the non-exported ones we'll get many things with the
162 -- same name in the interface file, giving chaos.
163 final_ids = [ tidyExternalId id
164 | id <- typeEnvIds type_env
168 -- default methods have their export flag set, but everything
169 -- else doesn't (yet), because this is pre-desugaring, so we
171 keep_it id = isExportedId id || idName id `elemNameSet` exports
174 tidyExternalId :: Id -> Id
175 -- Takes an LocalId with an External Name,
176 -- makes it into a GlobalId with VanillaIdInfo, and tidies its type
177 -- (NB: vanillaIdInfo makes a conservative assumption about Caf-hood.)
179 = ASSERT2( isLocalId id && isExternalName (idName id), ppr id )
180 mkVanillaGlobal (idName id) (tidyTopType (idType id))
184 %************************************************************************
186 Plan B: tidy bindings, make TypeEnv full of IdInfo
188 %************************************************************************
190 Plan B: include pragmas, make interfaces
191 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
192 * Figure out which Ids are externally visible
194 * Tidy the bindings, externalising appropriate Ids
196 * Drop all Ids from the TypeEnv, and add all the External Ids from
197 the bindings. (This adds their IdInfo to the TypeEnv; and adds
198 floated-out Ids that weren't even in the TypeEnv before.)
200 Step 1: Figure out external Ids
201 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
202 First we figure out which Ids are "external" Ids. An
203 "external" Id is one that is visible from outside the compilation
205 a) the user exported ones
206 b) ones mentioned in the unfoldings, workers,
207 or rules of externally-visible ones
208 This exercise takes a sweep of the bindings bottom to top. Actually,
209 in Step 2 we're also going to need to know which Ids should be
210 exported with their unfoldings, so we produce not an IdSet but an
211 ExtIdEnv = IdEnv Bool
214 Step 2: Tidy the program
215 ~~~~~~~~~~~~~~~~~~~~~~~~
216 Next we traverse the bindings top to bottom. For each *top-level*
219 1. Make it into a GlobalId; its IdDetails becomes VanillaGlobal,
220 reflecting the fact that from now on we regard it as a global,
223 2. Give it a system-wide Unique.
224 [Even non-exported things need system-wide Uniques because the
225 byte-code generator builds a single Name->BCO symbol table.]
227 We use the NameCache kept in the HscEnv as the
228 source of such system-wide uniques.
230 For external Ids, use the original-name cache in the NameCache
231 to ensure that the unique assigned is the same as the Id had
232 in any previous compilation run.
234 3. If it's an external Id, make it have a External Name, otherwise
235 make it have an Internal Name.
236 This is used by the code generator to decide whether
237 to make the label externally visible
239 4. Give external Ids a "tidy" OccName. This means
240 we can print them in interface files without confusing
241 "x" (unique 5) with "x" (unique 10).
243 5. Give it its UTTERLY FINAL IdInfo; in ptic,
244 * its unfolding, if it should have one
246 * its arity, computed from the number of visible lambdas
248 * its CAF info, computed from what is free in its RHS
251 Finally, substitute these new top-level binders consistently
252 throughout, including in unfoldings. We also tidy binders in
253 RHSs, so that they print nicely in interfaces.
256 tidyProgram :: HscEnv -> ModGuts -> IO (CgGuts, ModDetails)
257 tidyProgram hsc_env (ModGuts { mg_module = mod, mg_exports = exports,
259 mg_insts = insts, mg_fam_insts = fam_insts,
261 mg_rules = imp_rules,
262 mg_vect_info = vect_info,
263 mg_dir_imps = dir_imps,
266 mg_foreign = foreign_stubs,
267 mg_hpc_info = hpc_info,
268 mg_modBreaks = modBreaks })
270 = do { let dflags = hsc_dflags hsc_env
271 ; showPass dflags "Tidy Core"
273 ; let { omit_prags = dopt Opt_OmitInterfacePragmas dflags
274 ; th = dopt Opt_TemplateHaskell dflags
275 ; ext_ids = findExternalIds omit_prags binds
278 | otherwise = findExternalRules binds imp_rules ext_ids
279 -- findExternalRules filters imp_rules to avoid binders that
280 -- aren't externally visible; but the externally-visible binders
281 -- are computed (by findExternalIds) assuming that all orphan
282 -- rules are exported (they get their Exported flag set in the desugarer)
283 -- So in fact we may export more than we need.
284 -- (It's a sort of mutual recursion.)
287 ; (tidy_env, tidy_binds) <- tidyTopBinds hsc_env mod type_env ext_ids
290 ; let { export_set = availsToNameSet exports
291 ; final_ids = [ id | id <- bindersOfBinds tidy_binds,
292 isExternalName (idName id)]
293 ; tidy_type_env = tidyTypeEnv omit_prags th export_set
295 ; tidy_insts = tidyInstances (lookup_dfun tidy_type_env) insts
296 -- A DFunId will have a binding in tidy_binds, and so
297 -- will now be in final_env, replete with IdInfo
298 -- Its name will be unchanged since it was born, but
299 -- we want Global, IdInfo-rich (or not) DFunId in the
302 ; tidy_rules = tidyRules tidy_env ext_rules
303 -- You might worry that the tidy_env contains IdInfo-rich stuff
304 -- and indeed it does, but if omit_prags is on, ext_rules is
307 ; alg_tycons = filter isAlgTyCon (typeEnvTyCons type_env)
310 ; endPass dflags "Tidy Core" Opt_D_dump_simpl tidy_binds
311 ; dumpIfSet_core dflags Opt_D_dump_simpl
313 (pprRules tidy_rules)
315 ; let dir_imp_mods = moduleEnvKeys dir_imps
317 ; return (CgGuts { cg_module = mod,
318 cg_tycons = alg_tycons,
319 cg_binds = tidy_binds,
320 cg_dir_imps = dir_imp_mods,
321 cg_foreign = foreign_stubs,
322 cg_dep_pkgs = dep_pkgs deps,
323 cg_hpc_info = hpc_info,
324 cg_modBreaks = modBreaks },
326 ModDetails { md_types = tidy_type_env,
327 md_rules = tidy_rules,
328 md_insts = tidy_insts,
329 md_fam_insts = fam_insts,
330 md_exports = exports,
331 md_anns = anns, -- are already tidy
332 md_vect_info = vect_info --
336 lookup_dfun :: TypeEnv -> Var -> Id
337 lookup_dfun type_env dfun_id
338 = case lookupTypeEnv type_env (idName dfun_id) of
339 Just (AnId dfun_id') -> dfun_id'
340 _other -> pprPanic "lookup_dfun" (ppr dfun_id)
342 --------------------------
343 tidyTypeEnv :: Bool -- Compiling without -O, so omit prags
344 -> Bool -- Template Haskell is on
345 -> NameSet -> TypeEnv -> [Id] -> TypeEnv
347 -- The competed type environment is gotten from
348 -- Dropping any wired-in things, and then
349 -- a) keeping the types and classes
350 -- b) removing all Ids,
351 -- c) adding Ids with correct IdInfo, including unfoldings,
352 -- gotten from the bindings
353 -- From (c) we keep only those Ids with External names;
354 -- the CoreTidy pass makes sure these are all and only
355 -- the externally-accessible ones
356 -- This truncates the type environment to include only the
357 -- exported Ids and things needed from them, which saves space
359 tidyTypeEnv omit_prags th exports type_env final_ids
360 = let type_env1 = filterNameEnv keep_it type_env
361 type_env2 = extendTypeEnvWithIds type_env1 final_ids
362 type_env3 | omit_prags = mapNameEnv (trimThing th exports) type_env2
363 | otherwise = type_env2
367 -- We keep GlobalIds, because they won't appear
368 -- in the bindings from which final_ids are derived!
369 -- (The bindings bind LocalIds.)
370 keep_it thing | isWiredInThing thing = False
371 keep_it (AnId id) = isGlobalId id -- Keep GlobalIds (e.g. class ops)
372 keep_it _other = True -- Keep all TyCons, DataCons, and Classes
374 --------------------------
375 isWiredInThing :: TyThing -> Bool
376 isWiredInThing thing = isWiredInName (getName thing)
378 --------------------------
379 trimThing :: Bool -> NameSet -> TyThing -> TyThing
380 -- Trim off inessentials, for boot files and no -O
381 trimThing th exports (ATyCon tc)
382 | not th && not (mustExposeTyCon exports tc)
383 = ATyCon (makeTyConAbstract tc) -- Note [Trimming and Template Haskell]
385 trimThing _th _exports (AnId id)
386 | not (isImplicitId id)
387 = AnId (id `setIdInfo` vanillaIdInfo)
389 trimThing _th _exports other_thing
393 {- Note [Trimming and Template Haskell]
394 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
395 Consider (Trac #2386) this
396 module M(T, makeOne) where
398 makeOne = [| Yay "Yep" |]
399 Notice that T is exported abstractly, but makeOne effectively exports it too!
400 A module that splices in $(makeOne) will then look for a declartion of Yay,
401 so it'd better be there. Hence, brutally but simply, we switch off type
402 constructor trimming if TH is enabled in this module. -}
405 mustExposeTyCon :: NameSet -- Exports
406 -> TyCon -- The tycon
407 -> Bool -- Can its rep be hidden?
408 -- We are compiling without -O, and thus trying to write as little as
409 -- possible into the interface file. But we must expose the details of
410 -- any data types whose constructors or fields are exported
411 mustExposeTyCon exports tc
412 | not (isAlgTyCon tc) -- Synonyms
414 | isEnumerationTyCon tc -- For an enumeration, exposing the constructors
415 = True -- won't lead to the need for further exposure
416 -- (This includes data types with no constructors.)
417 | isOpenTyCon tc -- Open type family
420 | otherwise -- Newtype, datatype
421 = any exported_con (tyConDataCons tc)
422 -- Expose rep if any datacon or field is exported
424 || (isNewTyCon tc && isFFITy (snd (newTyConRhs tc)))
425 -- Expose the rep for newtypes if the rep is an FFI type.
426 -- For a very annoying reason. 'Foreign import' is meant to
427 -- be able to look through newtypes transparently, but it
428 -- can only do that if it can "see" the newtype representation
430 exported_con con = any (`elemNameSet` exports)
431 (dataConName con : dataConFieldLabels con)
433 tidyInstances :: (DFunId -> DFunId) -> [Instance] -> [Instance]
434 tidyInstances tidy_dfun ispecs
437 tidy ispec = setInstanceDFunId ispec $
438 tidy_dfun (instanceDFunId ispec)
442 %************************************************************************
444 \subsection{Step 1: finding externals}
446 %************************************************************************
449 type ExtIdEnv = IdEnv Bool
450 -- In domain => Id is external
451 -- Range = True <=> show unfolding,
452 -- Always True for InlineRule
454 findExternalIds :: Bool -> [CoreBind] -> ExtIdEnv
455 -- Step 1 from the notes above
456 findExternalIds omit_prags binds
458 = mkVarEnv [ (id,False) | id <- bindersOfBinds binds, isExportedId id ]
461 = foldr find emptyVarEnv binds
463 find (NonRec id rhs) needed
464 | need_id needed id = addExternal (id,rhs) needed
466 find (Rec prs) needed = find_prs prs needed
468 -- For a recursive group we have to look for a fixed point
470 | null needed_prs = needed
471 | otherwise = find_prs other_prs new_needed
473 (needed_prs, other_prs) = partition (need_pr needed) prs
474 new_needed = foldr addExternal needed needed_prs
476 -- The 'needed' set contains the Ids that are needed by earlier
477 -- interface file emissions. If the Id isn't in this set, and isn't
478 -- exported, there's no need to emit anything
479 need_id needed_set id = id `elemVarEnv` needed_set || isExportedId id
480 need_pr needed_set (id,_) = need_id needed_set id
482 addExternal :: (Id,CoreExpr) -> IdEnv Bool -> IdEnv Bool
483 -- The Id is needed; extend the needed set
484 -- with it and its dependents (free vars etc)
485 addExternal (id,rhs) needed
486 = extendVarEnv (foldVarSet add_occ needed new_needed_ids)
489 add_occ id needed | id `elemVarEnv` needed = needed
490 | otherwise = extendVarEnv needed id False
491 -- "False" because we don't know we need the Id's unfolding
492 -- Don't override existing bindings; we might have already set it to True
494 new_needed_ids = (mb_unfold_ids `orElse` emptyVarSet) `unionVarSet`
498 dont_inline = isNeverActive (inlinePragInfo idinfo)
499 loop_breaker = isNonRuleLoopBreaker (occInfo idinfo)
500 bottoming_fn = isBottomingSig (newStrictnessInfo idinfo `orElse` topSig)
501 spec_ids = specInfoFreeVars (specInfo idinfo)
503 -- Stuff to do with the Id's unfolding
504 -- We leave the unfolding there even if there is a worker
505 -- In GHCI the unfolding is used by importers
506 show_unfold = isJust mb_unfold_ids
508 mb_unfold_ids :: Maybe IdSet -- Nothing => don't unfold
509 mb_unfold_ids = case unfoldingInfo idinfo of
510 InlineRule { uf_worker = Just wkr_id } -> Just (unitVarSet wkr_id)
511 InlineRule { uf_tmpl = rhs } -> Just (exprFreeIds rhs)
512 CoreUnfolding { uf_guidance = guide }
513 | not bottoming_fn -- Not necessary
516 , not (neverUnfoldGuidance guide)
517 -> Just (exprFreeIds rhs) -- The simplifier has put an up-to-date unfolding
518 -- in the IdInfo, but the RHS will do just as well
525 findExternalRules :: [CoreBind]
526 -> [CoreRule] -- Non-local rules (i.e. ones for imported fns)
527 -> IdEnv a -- Ids that are exported, so we need their rules
529 -- The complete rules are gotten by combining
530 -- a) the non-local rules
531 -- b) rules embedded in the top-level Ids
532 findExternalRules binds non_local_rules ext_ids
533 = filter (not . internal_rule) (non_local_rules ++ local_rules)
536 | id <- bindersOfBinds binds,
537 id `elemVarEnv` ext_ids,
538 rule <- idCoreRules id
542 = any internal_id (varSetElems (ruleLhsFreeIds rule))
543 -- Don't export a rule whose LHS mentions a locally-defined
544 -- Id that is completely internal (i.e. not visible to an
547 internal_id id = not (id `elemVarEnv` ext_ids)
552 %************************************************************************
554 \subsection{Step 2: top-level tidying}
556 %************************************************************************
560 -- TopTidyEnv: when tidying we need to know
561 -- * nc_var: The NameCache, containing a unique supply and any pre-ordained Names.
562 -- These may have arisen because the
563 -- renamer read in an interface file mentioning M.$wf, say,
564 -- and assigned it unique r77. If, on this compilation, we've
565 -- invented an Id whose name is $wf (but with a different unique)
566 -- we want to rename it to have unique r77, so that we can do easy
567 -- comparisons with stuff from the interface file
569 -- * occ_env: The TidyOccEnv, which tells us which local occurrences
572 -- * subst_env: A Var->Var mapping that substitutes the new Var for the old
574 tidyTopBinds :: HscEnv
579 -> IO (TidyEnv, [CoreBind])
581 tidyTopBinds hsc_env mod type_env ext_ids binds
582 = tidy init_env binds
584 nc_var = hsc_NC hsc_env
586 -- We also make sure to avoid any exported binders. Consider
587 -- f{-u1-} = 1 -- Local decl
589 -- f{-u2-} = 2 -- Exported decl
591 -- The second exported decl must 'get' the name 'f', so we
592 -- have to put 'f' in the avoids list before we get to the first
593 -- decl. tidyTopId then does a no-op on exported binders.
594 init_env = (initTidyOccEnv avoids, emptyVarEnv)
595 avoids = [getOccName name | bndr <- typeEnvIds type_env,
596 let name = idName bndr,
598 -- In computing our "avoids" list, we must include
600 -- all things with global names (assigned once and for
601 -- all by the renamer)
602 -- since their names are "taken".
603 -- The type environment is a convenient source of such things.
605 this_pkg = thisPackage (hsc_dflags hsc_env)
607 tidy env [] = return (env, [])
608 tidy env (b:bs) = do { (env1, b') <- tidyTopBind this_pkg mod nc_var ext_ids env b
609 ; (env2, bs') <- tidy env1 bs
610 ; return (env2, b':bs') }
612 ------------------------
613 tidyTopBind :: PackageId
615 -> IORef NameCache -- For allocating new unique names
617 -> TidyEnv -> CoreBind
618 -> IO (TidyEnv, CoreBind)
620 tidyTopBind this_pkg mod nc_var ext_ids (occ_env1,subst1) (NonRec bndr rhs)
621 = do { (occ_env2, name') <- tidyTopName mod nc_var ext_ids occ_env1 bndr
622 ; let { (bndr', rhs') = tidyTopPair ext_ids tidy_env2 caf_info name' (bndr, rhs)
623 ; subst2 = extendVarEnv subst1 bndr bndr'
624 ; tidy_env2 = (occ_env2, subst2) }
625 ; return (tidy_env2, NonRec bndr' rhs') }
627 caf_info = hasCafRefs this_pkg subst1 (idArity bndr) rhs
629 tidyTopBind this_pkg mod nc_var ext_ids (occ_env1,subst1) (Rec prs)
630 = do { (occ_env2, names') <- tidyTopNames mod nc_var ext_ids occ_env1 bndrs
631 ; let { prs' = zipWith (tidyTopPair ext_ids tidy_env2 caf_info)
633 ; subst2 = extendVarEnvList subst1 (bndrs `zip` map fst prs')
634 ; tidy_env2 = (occ_env2, subst2) }
635 ; return (tidy_env2, Rec prs') }
639 -- the CafInfo for a recursive group says whether *any* rhs in
640 -- the group may refer indirectly to a CAF (because then, they all do).
642 | or [ mayHaveCafRefs (hasCafRefs this_pkg subst1 (idArity bndr) rhs)
643 | (bndr,rhs) <- prs ] = MayHaveCafRefs
644 | otherwise = NoCafRefs
646 --------------------------------------------------------------------
648 -- This is where we set names to local/global based on whether they really are
649 -- externally visible (see comment at the top of this module). If the name
650 -- was previously local, we have to give it a unique occurrence name if
651 -- we intend to externalise it.
652 tidyTopNames :: Module -> IORef NameCache -> VarEnv Bool -> TidyOccEnv
653 -> [Id] -> IO (TidyOccEnv, [Name])
654 tidyTopNames _mod _nc_var _ext_ids occ_env [] = return (occ_env, [])
655 tidyTopNames mod nc_var ext_ids occ_env (id:ids)
656 = do { (occ_env1, name) <- tidyTopName mod nc_var ext_ids occ_env id
657 ; (occ_env2, names) <- tidyTopNames mod nc_var ext_ids occ_env1 ids
658 ; return (occ_env2, name:names) }
660 tidyTopName :: Module -> IORef NameCache -> VarEnv Bool -> TidyOccEnv
661 -> Id -> IO (TidyOccEnv, Name)
662 tidyTopName mod nc_var ext_ids occ_env id
663 | global && internal = return (occ_env, localiseName name)
665 | global && external = return (occ_env, name)
666 -- Global names are assumed to have been allocated by the renamer,
667 -- so they already have the "right" unique
668 -- And it's a system-wide unique too
670 -- Now we get to the real reason that all this is in the IO Monad:
671 -- we have to update the name cache in a nice atomic fashion
673 | local && internal = do { nc <- readIORef nc_var
674 ; let (nc', new_local_name) = mk_new_local nc
675 ; writeIORef nc_var nc'
676 ; return (occ_env', new_local_name) }
677 -- Even local, internal names must get a unique occurrence, because
678 -- if we do -split-objs we externalise the name later, in the code generator
680 -- Similarly, we must make sure it has a system-wide Unique, because
681 -- the byte-code generator builds a system-wide Name->BCO symbol table
683 | local && external = do { nc <- readIORef nc_var
684 ; let (nc', new_external_name) = mk_new_external nc
685 ; writeIORef nc_var nc'
686 ; return (occ_env', new_external_name) }
688 | otherwise = panic "tidyTopName"
691 external = id `elemVarEnv` ext_ids
692 global = isExternalName name
694 internal = not external
695 loc = nameSrcSpan name
697 (occ_env', occ') = tidyOccName occ_env (nameOccName name)
699 mk_new_local nc = (nc { nsUniqs = us2 }, mkInternalName uniq occ' loc)
701 (us1, us2) = splitUniqSupply (nsUniqs nc)
702 uniq = uniqFromSupply us1
704 mk_new_external nc = allocateGlobalBinder nc mod occ' loc
705 -- If we want to externalise a currently-local name, check
706 -- whether we have already assigned a unique for it.
707 -- If so, use it; if not, extend the table.
708 -- All this is done by allcoateGlobalBinder.
709 -- This is needed when *re*-compiling a module in GHCi; we must
710 -- use the same name for externally-visible things as we did before.
713 -----------------------------------------------------------
714 tidyTopPair :: VarEnv Bool
715 -> TidyEnv -- The TidyEnv is used to tidy the IdInfo
716 -- It is knot-tied: don't look at it!
719 -> (Id, CoreExpr) -- Binder and RHS before tidying
721 -- This function is the heart of Step 2
722 -- The rec_tidy_env is the one to use for the IdInfo
723 -- It's necessary because when we are dealing with a recursive
724 -- group, a variable late in the group might be mentioned
725 -- in the IdInfo of one early in the group
727 tidyTopPair ext_ids rhs_tidy_env caf_info name' (bndr, rhs)
730 bndr' = mkGlobalId details name' ty' idinfo'
731 -- Preserve the GlobalIdDetails of existing global-ids
732 details = case globalIdDetails bndr of
733 NotGlobalId -> VanillaGlobal
734 old_details -> old_details
735 ty' = tidyTopType (idType bndr)
736 rhs' = tidyExpr rhs_tidy_env rhs
738 idinfo' = tidyTopIdInfo (isJust maybe_external)
742 -- Expose an unfolding if ext_ids tells us to
743 -- Remember that ext_ids maps an Id to a Bool:
744 -- True to show the unfolding, False to hide it
745 maybe_external = lookupVarEnv ext_ids bndr
746 show_unfold = maybe_external `orElse` False
747 unfold_info | show_unfold = tidyUnfolding rhs_tidy_env rhs' (unfoldingInfo idinfo)
748 | otherwise = noUnfolding
749 -- NB: do *not* expose the worker if show_unfold is off,
750 -- because that means this thing is a loop breaker or
751 -- marked NOINLINE or something like that
752 -- This is important: if you expose the worker for a loop-breaker
753 -- then you can make the simplifier go into an infinite loop, because
754 -- in effect the unfolding is exposed. See Trac #1709
756 -- You might think that if show_unfold is False, then the thing should
757 -- not be w/w'd in the first place. But a legitimate reason is this:
758 -- the function returns bottom
759 -- In this case, show_unfold will be false (we don't expose unfoldings
760 -- for bottoming functions), but we might still have a worker/wrapper
761 -- split (see Note [Worker-wrapper for bottoming functions] in WorkWrap.lhs
763 -- Usually the Id will have an accurate arity on it, because
764 -- the simplifier has just run, but not always.
765 -- One case I found was when the last thing the simplifier
766 -- did was to let-bind a non-atomic argument and then float
767 -- it to the top level. So it seems more robust just to
769 arity = exprArity rhs
772 -- tidyTopIdInfo creates the final IdInfo for top-level
773 -- binders. There are two delicate pieces:
775 -- * Arity. After CoreTidy, this arity must not change any more.
776 -- Indeed, CorePrep must eta expand where necessary to make
777 -- the manifest arity equal to the claimed arity.
779 -- * CAF info. This must also remain valid through to code generation.
780 -- We add the info here so that it propagates to all
781 -- occurrences of the binders in RHSs, and hence to occurrences in
782 -- unfoldings, which are inside Ids imported by GHCi. Ditto RULES.
783 -- CoreToStg makes use of this when constructing SRTs.
784 tidyTopIdInfo :: Bool -> IdInfo -> Unfolding
785 -> ArityInfo -> CafInfo
787 tidyTopIdInfo is_external idinfo unfold_info arity caf_info
788 | not is_external -- For internal Ids (not externally visible)
789 = vanillaIdInfo -- we only need enough info for code generation
790 -- Arity and strictness info are enough;
791 -- c.f. CoreTidy.tidyLetBndr
792 `setCafInfo` caf_info
794 `setAllStrictnessInfo` newStrictnessInfo idinfo
796 | otherwise -- Externally-visible Ids get the whole lot
798 `setCafInfo` caf_info
800 `setAllStrictnessInfo` newStrictnessInfo idinfo
801 `setInlinePragInfo` inlinePragInfo idinfo
802 `setUnfoldingInfo` unfold_info
803 -- NB: we throw away the Rules
804 -- They have already been extracted by findExternalRules
808 ------------ Unfolding --------------
809 tidyUnfolding :: TidyEnv -> CoreExpr -> Unfolding -> Unfolding
810 tidyUnfolding tidy_env _ unf@(InlineRule { uf_tmpl = rhs, uf_worker = mb_wkr })
811 = unf { uf_tmpl = tidyExpr tidy_env rhs,
812 uf_worker = fmap (tidyVarOcc tidy_env) mb_wkr }
813 tidyUnfolding _ tidy_rhs (CoreUnfolding {})
814 = mkTopUnfolding tidy_rhs
815 tidyUnfolding _ _ unf = unf
818 %************************************************************************
820 \subsection{Figuring out CafInfo for an expression}
822 %************************************************************************
824 hasCafRefs decides whether a top-level closure can point into the dynamic heap.
825 We mark such things as `MayHaveCafRefs' because this information is
826 used to decide whether a particular closure needs to be referenced
829 There are two reasons for setting MayHaveCafRefs:
830 a) The RHS is a CAF: a top-level updatable thunk.
831 b) The RHS refers to something that MayHaveCafRefs
833 Possible improvement: In an effort to keep the number of CAFs (and
834 hence the size of the SRTs) down, we could also look at the expression and
835 decide whether it requires a small bounded amount of heap, so we can ignore
836 it as a CAF. In these cases however, we would need to use an additional
837 CAF list to keep track of non-collectable CAFs.
840 hasCafRefs :: PackageId -> VarEnv Var -> Arity -> CoreExpr -> CafInfo
841 hasCafRefs this_pkg p arity expr
842 | is_caf || mentions_cafs
844 | otherwise = NoCafRefs
846 mentions_cafs = isFastTrue (cafRefs p expr)
847 is_caf = not (arity > 0 || rhsIsStatic this_pkg expr)
849 -- NB. we pass in the arity of the expression, which is expected
850 -- to be calculated by exprArity. This is because exprArity
851 -- knows how much eta expansion is going to be done by
852 -- CorePrep later on, and we don't want to duplicate that
853 -- knowledge in rhsIsStatic below.
855 cafRefs :: VarEnv Id -> Expr a -> FastBool
857 -- imported Ids first:
858 | not (isLocalId id) = fastBool (mayHaveCafRefs (idCafInfo id))
859 -- now Ids local to this module:
861 case lookupVarEnv p id of
862 Just id' -> fastBool (mayHaveCafRefs (idCafInfo id'))
863 Nothing -> fastBool False
865 cafRefs _ (Lit _) = fastBool False
866 cafRefs p (App f a) = fastOr (cafRefs p f) (cafRefs p) a
867 cafRefs p (Lam _ e) = cafRefs p e
868 cafRefs p (Let b e) = fastOr (cafRefss p (rhssOfBind b)) (cafRefs p) e
869 cafRefs p (Case e _bndr _ alts) = fastOr (cafRefs p e) (cafRefss p) (rhssOfAlts alts)
870 cafRefs p (Note _n e) = cafRefs p e
871 cafRefs p (Cast e _co) = cafRefs p e
872 cafRefs _ (Type _) = fastBool False
874 cafRefss :: VarEnv Id -> [Expr a] -> FastBool
875 cafRefss _ [] = fastBool False
876 cafRefss p (e:es) = fastOr (cafRefs p e) (cafRefss p) es
878 fastOr :: FastBool -> (a -> FastBool) -> a -> FastBool
879 -- hack for lazy-or over FastBool.
880 fastOr a f x = fastBool (isFastTrue a || isFastTrue (f x))