2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section{Tidying up Core}
7 module TidyPgm( mkBootModDetailsDs, mkBootModDetailsTc,
8 tidyProgram, globaliseAndTidyId ) where
10 #include "HsVersions.h"
22 import CoreArity ( exprArity, exprBotStrictness_maybe )
23 import Class ( classSelIds )
32 import Name hiding (varName)
44 import FastBool hiding ( fastOr )
48 import Data.List ( sortBy )
49 import Data.IORef ( IORef, readIORef, writeIORef )
53 Constructing the TypeEnv, Instances, Rules, VectInfo from which the
54 ModIface is constructed, and which goes on to subsequent modules in
57 Most of the interface file is obtained simply by serialising the
58 TypeEnv. One important consequence is that if the *interface file*
59 has pragma info if and only if the final TypeEnv does. This is not so
60 important for *this* module, but it's essential for ghc --make:
61 subsequent compilations must not see (e.g.) the arity if the interface
62 file does not contain arity If they do, they'll exploit the arity;
63 then the arity might change, but the iface file doesn't change =>
64 recompilation does not happen => disaster.
66 For data types, the final TypeEnv will have a TyThing for the TyCon,
67 plus one for each DataCon; the interface file will contain just one
68 data type declaration, but it is de-serialised back into a collection
71 %************************************************************************
75 %************************************************************************
78 Plan A: mkBootModDetails: omit pragmas, make interfaces small
79 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
82 * Drop all WiredIn things from the TypeEnv
83 (we never want them in interface files)
85 * Retain all TyCons and Classes in the TypeEnv, to avoid
86 having to find which ones are mentioned in the
89 * Trim off the constructors of non-exported TyCons, both
90 from the TyCon and from the TypeEnv
92 * Drop non-exported Ids from the TypeEnv
94 * Tidy the types of the DFunIds of Instances,
95 make them into GlobalIds, (they already have External Names)
96 and add them to the TypeEnv
98 * Tidy the types of the (exported) Ids in the TypeEnv,
99 make them into GlobalIds (they already have External Names)
101 * Drop rules altogether
103 * Tidy the bindings, to ensure that the Caf and Arity
104 information is correct for each top-level binder; the
105 code generator needs it. And to ensure that local names have
106 distinct OccNames in case of object-file splitting
109 -- This is Plan A: make a small type env when typechecking only,
110 -- or when compiling a hs-boot file, or simply when not using -O
112 -- We don't look at the bindings at all -- there aren't any
115 mkBootModDetailsTc :: HscEnv -> TcGblEnv -> IO ModDetails
116 mkBootModDetailsTc hsc_env
117 TcGblEnv{ tcg_exports = exports,
118 tcg_type_env = type_env,
120 tcg_fam_insts = fam_insts
122 = mkBootModDetails hsc_env exports type_env insts fam_insts
124 mkBootModDetailsDs :: HscEnv -> ModGuts -> IO ModDetails
125 mkBootModDetailsDs hsc_env
126 ModGuts{ mg_exports = exports,
129 mg_fam_insts = fam_insts
131 = mkBootModDetails hsc_env exports type_env insts fam_insts
133 mkBootModDetails :: HscEnv -> [AvailInfo] -> NameEnv TyThing
134 -> [Instance] -> [FamInstEnv.FamInst] -> IO ModDetails
135 mkBootModDetails hsc_env exports type_env insts fam_insts
136 = do { let dflags = hsc_dflags hsc_env
137 ; showPass dflags CoreTidy
139 ; let { insts' = tidyInstances globaliseAndTidyId insts
140 ; dfun_ids = map instanceDFunId insts'
141 ; type_env1 = tidyBootTypeEnv (availsToNameSet exports) type_env
142 ; type_env' = extendTypeEnvWithIds type_env1 dfun_ids
144 ; return (ModDetails { md_types = type_env'
146 , md_fam_insts = fam_insts
149 , md_exports = exports
150 , md_vect_info = noVectInfo
155 tidyBootTypeEnv :: NameSet -> TypeEnv -> TypeEnv
156 tidyBootTypeEnv exports type_env
157 = tidyTypeEnv True False exports type_env final_ids
159 -- Find the LocalIds in the type env that are exported
160 -- Make them into GlobalIds, and tidy their types
162 -- It's very important to remove the non-exported ones
163 -- because we don't tidy the OccNames, and if we don't remove
164 -- the non-exported ones we'll get many things with the
165 -- same name in the interface file, giving chaos.
166 final_ids = [ globaliseAndTidyId id
167 | id <- typeEnvIds type_env
171 -- default methods have their export flag set, but everything
172 -- else doesn't (yet), because this is pre-desugaring, so we
174 keep_it id = isExportedId id || idName id `elemNameSet` exports
178 globaliseAndTidyId :: Id -> Id
179 -- Takes an LocalId with an External Name,
180 -- makes it into a GlobalId
181 -- * unchanged Name (might be Internal or External)
182 -- * unchanged details
183 -- * VanillaIdInfo (makes a conservative assumption about Caf-hood)
184 globaliseAndTidyId id
185 = Id.setIdType (globaliseId id) tidy_type
187 tidy_type = tidyTopType (idType id)
191 %************************************************************************
193 Plan B: tidy bindings, make TypeEnv full of IdInfo
195 %************************************************************************
197 Plan B: include pragmas, make interfaces
198 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
199 * Figure out which Ids are externally visible
201 * Tidy the bindings, externalising appropriate Ids
203 * Drop all Ids from the TypeEnv, and add all the External Ids from
204 the bindings. (This adds their IdInfo to the TypeEnv; and adds
205 floated-out Ids that weren't even in the TypeEnv before.)
207 Step 1: Figure out external Ids
208 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
209 Note [choosing external names]
211 See also the section "Interface stability" in the
212 RecompilationAvoidance commentary:
213 http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/RecompilationAvoidance
215 First we figure out which Ids are "external" Ids. An
216 "external" Id is one that is visible from outside the compilation
218 a) the user exported ones
219 b) ones mentioned in the unfoldings, workers,
220 or rules of externally-visible ones
222 While figuring out which Ids are external, we pick a "tidy" OccName
223 for each one. That is, we make its OccName distinct from the other
224 external OccNames in this module, so that in interface files and
225 object code we can refer to it unambiguously by its OccName. The
226 OccName for each binder is prefixed by the name of the exported Id
227 that references it; e.g. if "f" references "x" in its unfolding, then
228 "x" is renamed to "f_x". This helps distinguish the different "x"s
229 from each other, and means that if "f" is later removed, things that
230 depend on the other "x"s will not need to be recompiled. Of course,
231 if there are multiple "f_x"s, then we have to disambiguate somehow; we
232 use "f_x0", "f_x1" etc.
234 As far as possible we should assign names in a deterministic fashion.
235 Each time this module is compiled with the same options, we should end
236 up with the same set of external names with the same types. That is,
237 the ABI hash in the interface should not change. This turns out to be
238 quite tricky, since the order of the bindings going into the tidy
239 phase is already non-deterministic, as it is based on the ordering of
240 Uniques, which are assigned unpredictably.
242 To name things in a stable way, we do a depth-first-search of the
243 bindings, starting from the exports sorted by name. This way, as long
244 as the bindings themselves are deterministic (they sometimes aren't!),
245 the order in which they are presented to the tidying phase does not
246 affect the names we assign.
248 Step 2: Tidy the program
249 ~~~~~~~~~~~~~~~~~~~~~~~~
250 Next we traverse the bindings top to bottom. For each *top-level*
253 1. Make it into a GlobalId; its IdDetails becomes VanillaGlobal,
254 reflecting the fact that from now on we regard it as a global,
257 2. Give it a system-wide Unique.
258 [Even non-exported things need system-wide Uniques because the
259 byte-code generator builds a single Name->BCO symbol table.]
261 We use the NameCache kept in the HscEnv as the
262 source of such system-wide uniques.
264 For external Ids, use the original-name cache in the NameCache
265 to ensure that the unique assigned is the same as the Id had
266 in any previous compilation run.
268 3. Rename top-level Ids according to the names we chose in step 1.
269 If it's an external Id, make it have a External Name, otherwise
270 make it have an Internal Name. This is used by the code generator
271 to decide whether to make the label externally visible
273 4. Give it its UTTERLY FINAL IdInfo; in ptic,
274 * its unfolding, if it should have one
276 * its arity, computed from the number of visible lambdas
278 * its CAF info, computed from what is free in its RHS
281 Finally, substitute these new top-level binders consistently
282 throughout, including in unfoldings. We also tidy binders in
283 RHSs, so that they print nicely in interfaces.
286 tidyProgram :: HscEnv -> ModGuts -> IO (CgGuts, ModDetails)
287 tidyProgram hsc_env (ModGuts { mg_module = mod, mg_exports = exports,
289 mg_insts = insts, mg_fam_insts = fam_insts,
291 mg_rules = imp_rules,
292 mg_vect_info = vect_info,
293 mg_dir_imps = dir_imps,
296 mg_foreign = foreign_stubs,
297 mg_hpc_info = hpc_info,
298 mg_modBreaks = modBreaks })
300 = do { let { dflags = hsc_dflags hsc_env
301 ; omit_prags = dopt Opt_OmitInterfacePragmas dflags
302 ; expose_all = dopt Opt_ExposeAllUnfoldings dflags
303 ; th = dopt Opt_TemplateHaskell dflags
305 ; showPass dflags CoreTidy
307 ; let { implicit_binds = getImplicitBinds type_env }
309 ; (unfold_env, tidy_occ_env)
310 <- chooseExternalIds hsc_env mod omit_prags expose_all
311 binds implicit_binds imp_rules
313 ; let { ext_rules = findExternalRules omit_prags binds imp_rules unfold_env }
314 -- Glom together imp_rules and rules currently attached to binders
315 -- Then pick just the ones we need to expose
316 -- See Note [Which rules to expose]
318 ; let { (tidy_env, tidy_binds)
319 = tidyTopBinds hsc_env unfold_env tidy_occ_env binds }
321 ; let { export_set = availsToNameSet exports
322 ; final_ids = [ id | id <- bindersOfBinds tidy_binds,
323 isExternalName (idName id)]
324 ; tidy_type_env = tidyTypeEnv omit_prags th export_set
326 ; tidy_insts = tidyInstances (lookup_dfun tidy_type_env) insts
327 -- A DFunId will have a binding in tidy_binds, and so
328 -- will now be in final_env, replete with IdInfo
329 -- Its name will be unchanged since it was born, but
330 -- we want Global, IdInfo-rich (or not) DFunId in the
333 ; tidy_rules = tidyRules tidy_env ext_rules
334 -- You might worry that the tidy_env contains IdInfo-rich stuff
335 -- and indeed it does, but if omit_prags is on, ext_rules is
338 ; tidy_vect_info = tidyVectInfo tidy_env vect_info
340 -- See Note [Injecting implicit bindings]
341 ; all_tidy_binds = implicit_binds ++ tidy_binds
343 ; alg_tycons = filter isAlgTyCon (typeEnvTyCons type_env)
346 ; endPass dflags CoreTidy all_tidy_binds tidy_rules
348 -- If the endPass didn't print the rules, but ddump-rules is on, print now
349 ; dumpIfSet (dopt Opt_D_dump_rules dflags
350 && (not (dopt Opt_D_dump_simpl dflags)))
352 (ptext (sLit "rules"))
353 (pprRulesForUser tidy_rules)
355 ; let dir_imp_mods = moduleEnvKeys dir_imps
357 ; return (CgGuts { cg_module = mod,
358 cg_tycons = alg_tycons,
359 cg_binds = all_tidy_binds,
360 cg_dir_imps = dir_imp_mods,
361 cg_foreign = foreign_stubs,
362 cg_dep_pkgs = dep_pkgs deps,
363 cg_hpc_info = hpc_info,
364 cg_modBreaks = modBreaks },
366 ModDetails { md_types = tidy_type_env,
367 md_rules = tidy_rules,
368 md_insts = tidy_insts,
369 md_vect_info = tidy_vect_info,
370 md_fam_insts = fam_insts,
371 md_exports = exports,
372 md_anns = anns -- are already tidy
376 lookup_dfun :: TypeEnv -> Var -> Id
377 lookup_dfun type_env dfun_id
378 = case lookupTypeEnv type_env (idName dfun_id) of
379 Just (AnId dfun_id') -> dfun_id'
380 _other -> pprPanic "lookup_dfun" (ppr dfun_id)
382 --------------------------
383 tidyTypeEnv :: Bool -- Compiling without -O, so omit prags
384 -> Bool -- Template Haskell is on
385 -> NameSet -> TypeEnv -> [Id] -> TypeEnv
387 -- The competed type environment is gotten from
388 -- Dropping any wired-in things, and then
389 -- a) keeping the types and classes
390 -- b) removing all Ids,
391 -- c) adding Ids with correct IdInfo, including unfoldings,
392 -- gotten from the bindings
393 -- From (c) we keep only those Ids with External names;
394 -- the CoreTidy pass makes sure these are all and only
395 -- the externally-accessible ones
396 -- This truncates the type environment to include only the
397 -- exported Ids and things needed from them, which saves space
399 tidyTypeEnv omit_prags th exports type_env final_ids
400 = let type_env1 = filterNameEnv keep_it type_env
401 type_env2 = extendTypeEnvWithIds type_env1 final_ids
402 type_env3 | omit_prags = mapNameEnv (trimThing th exports) type_env2
403 | otherwise = type_env2
407 -- We keep GlobalIds, because they won't appear
408 -- in the bindings from which final_ids are derived!
409 -- (The bindings bind LocalIds.)
410 keep_it thing | isWiredInThing thing = False
411 keep_it (AnId id) = isGlobalId id -- Keep GlobalIds (e.g. class ops)
412 keep_it _other = True -- Keep all TyCons, DataCons, and Classes
414 --------------------------
415 isWiredInThing :: TyThing -> Bool
416 isWiredInThing thing = isWiredInName (getName thing)
418 --------------------------
419 trimThing :: Bool -> NameSet -> TyThing -> TyThing
420 -- Trim off inessentials, for boot files and no -O
421 trimThing th exports (ATyCon tc)
422 | not th && not (mustExposeTyCon exports tc)
423 = ATyCon (makeTyConAbstract tc) -- Note [Trimming and Template Haskell]
425 trimThing _th _exports (AnId id)
426 | not (isImplicitId id)
427 = AnId (id `setIdInfo` vanillaIdInfo)
429 trimThing _th _exports other_thing
433 {- Note [Trimming and Template Haskell]
434 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
435 Consider (Trac #2386) this
436 module M(T, makeOne) where
438 makeOne = [| Yay "Yep" |]
439 Notice that T is exported abstractly, but makeOne effectively exports it too!
440 A module that splices in $(makeOne) will then look for a declartion of Yay,
441 so it'd better be there. Hence, brutally but simply, we switch off type
442 constructor trimming if TH is enabled in this module. -}
445 mustExposeTyCon :: NameSet -- Exports
446 -> TyCon -- The tycon
447 -> Bool -- Can its rep be hidden?
448 -- We are compiling without -O, and thus trying to write as little as
449 -- possible into the interface file. But we must expose the details of
450 -- any data types whose constructors or fields are exported
451 mustExposeTyCon exports tc
452 | not (isAlgTyCon tc) -- Synonyms
454 | isEnumerationTyCon tc -- For an enumeration, exposing the constructors
455 = True -- won't lead to the need for further exposure
456 -- (This includes data types with no constructors.)
457 | isOpenTyCon tc -- Open type family
460 | otherwise -- Newtype, datatype
461 = any exported_con (tyConDataCons tc)
462 -- Expose rep if any datacon or field is exported
464 || (isNewTyCon tc && isFFITy (snd (newTyConRhs tc)))
465 -- Expose the rep for newtypes if the rep is an FFI type.
466 -- For a very annoying reason. 'Foreign import' is meant to
467 -- be able to look through newtypes transparently, but it
468 -- can only do that if it can "see" the newtype representation
470 exported_con con = any (`elemNameSet` exports)
471 (dataConName con : dataConFieldLabels con)
473 tidyInstances :: (DFunId -> DFunId) -> [Instance] -> [Instance]
474 tidyInstances tidy_dfun ispecs
477 tidy ispec = setInstanceDFunId ispec $
478 tidy_dfun (instanceDFunId ispec)
482 tidyVectInfo :: TidyEnv -> VectInfo -> VectInfo
483 tidyVectInfo (_, var_env) info@(VectInfo { vectInfoVar = vars
484 , vectInfoPADFun = pas
485 , vectInfoIso = isos })
486 = info { vectInfoVar = tidy_vars
487 , vectInfoPADFun = tidy_pas
488 , vectInfoIso = tidy_isos }
491 $ map tidy_var_mapping
494 tidy_pas = mapNameEnv tidy_snd_var pas
495 tidy_isos = mapNameEnv tidy_snd_var isos
497 tidy_var_mapping (from, to) = (from', (from', lookup_var to))
498 where from' = lookup_var from
499 tidy_snd_var (x, var) = (x, lookup_var var)
501 lookup_var var = lookupWithDefaultVarEnv var_env var var
505 %************************************************************************
509 %************************************************************************
511 Note [Injecting implicit bindings]
512 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
513 We inject the implict bindings right at the end, in CoreTidy.
514 Some of these bindings, notably record selectors, are not
515 constructed in an optimised form. E.g. record selector for
516 data T = MkT { x :: {-# UNPACK #-} !Int }
517 Then the unfolding looks like
518 x = \t. case t of MkT x1 -> let x = I# x1 in x
519 This generates bad code unless it's first simplified a bit. That is
520 why CoreUnfold.mkImplicitUnfolding uses simleExprOpt to do a bit of
521 optimisation first. (Only matters when the selector is used curried;
522 eg map x ys.) See Trac #2070.
524 [Oct 09: in fact, record selectors are no longer implicit Ids at all,
525 because we really do want to optimise them properly. They are treated
526 much like any other Id. But doing "light" optimisation on an implicit
527 Id still makes sense.]
529 At one time I tried injecting the implicit bindings *early*, at the
530 beginning of SimplCore. But that gave rise to real difficulty,
531 becuase GlobalIds are supposed to have *fixed* IdInfo, but the
532 simplifier and other core-to-core passes mess with IdInfo all the
533 time. The straw that broke the camels back was when a class selector
534 got the wrong arity -- ie the simplifier gave it arity 2, whereas
535 importing modules were expecting it to have arity 1 (Trac #2844).
536 It's much safer just to inject them right at the end, after tidying.
538 Oh: two other reasons for injecting them late:
540 - If implicit Ids are already in the bindings when we start TidyPgm,
541 we'd have to be careful not to treat them as external Ids (in
542 the sense of findExternalIds); else the Ids mentioned in *their*
543 RHSs will be treated as external and you get an interface file
545 but nothing refererring to a18 (because the implicit Id is the
546 one that does, and implicit Ids don't appear in interface files).
548 - More seriously, the tidied type-envt will include the implicit
549 Id replete with a18 in its unfolding; but we won't take account
550 of a18 when computing a fingerprint for the class; result chaos.
552 There is one sort of implicit binding that is injected still later,
553 namely those for data constructor workers. Reason (I think): it's
554 really just a code generation trick.... binding itself makes no sense.
555 See CorePrep Note [Data constructor workers].
558 getImplicitBinds :: TypeEnv -> [CoreBind]
559 getImplicitBinds type_env
560 = map get_defn (concatMap implicit_ids (typeEnvElts type_env))
562 implicit_ids (ATyCon tc) = mapCatMaybes dataConWrapId_maybe (tyConDataCons tc)
563 implicit_ids (AClass cls) = classSelIds cls
566 get_defn :: Id -> CoreBind
567 get_defn id = NonRec id (unfoldingTemplate (realIdUnfolding id))
571 %************************************************************************
573 \subsection{Step 1: finding externals}
575 %************************************************************************
577 Sete Note [choosing external names].
580 type UnfoldEnv = IdEnv (Name{-new name-}, Bool {-show unfolding-})
581 -- Maps each top-level Id to its new Name (the Id is tidied in step 2)
582 -- The Unique is unchanged. If the new Name is external, it will be
583 -- visible in the interface file.
585 -- Bool => expose unfolding or not.
587 chooseExternalIds :: HscEnv
593 -> IO (UnfoldEnv, TidyOccEnv)
594 -- Step 1 from the notes above
596 chooseExternalIds hsc_env mod omit_prags expose_all binds implicit_binds imp_id_rules
597 = do { (unfold_env1,occ_env1) <- search init_work_list emptyVarEnv init_occ_env
598 ; let internal_ids = filter (not . (`elemVarEnv` unfold_env1)) binders
599 ; tidy_internal internal_ids unfold_env1 occ_env1 }
601 nc_var = hsc_NC hsc_env
603 -- init_ext_ids is the intial list of Ids that should be
604 -- externalised. It serves as the starting point for finding a
605 -- deterministic, tidy, renaming for all external Ids in this
608 -- It is sorted, so that it has adeterministic order (i.e. it's the
609 -- same list every time this module is compiled), in contrast to the
610 -- bindings, which are ordered non-deterministically.
611 init_work_list = zip init_ext_ids init_ext_ids
612 init_ext_ids = sortBy (compare `on` getOccName) $
613 filter is_external binders
615 -- An Id should be external if either (a) it is exported or
616 -- (b) it appears in the RHS of a local rule for an imported Id.
617 -- See Note [Which rules to expose]
618 is_external id = isExportedId id || id `elemVarSet` rule_rhs_vars
619 rule_rhs_vars = foldr (unionVarSet . ruleRhsFreeVars) emptyVarSet imp_id_rules
621 binders = bindersOfBinds binds
622 implicit_binders = bindersOfBinds implicit_binds
623 binder_set = mkVarSet binders
625 avoids = [getOccName name | bndr <- binders ++ implicit_binders,
626 let name = idName bndr,
627 isExternalName name ]
628 -- In computing our "avoids" list, we must include
630 -- all things with global names (assigned once and for
631 -- all by the renamer)
632 -- since their names are "taken".
633 -- The type environment is a convenient source of such things.
634 -- In particular, the set of binders doesn't include
635 -- implicit Ids at this stage.
637 -- We also make sure to avoid any exported binders. Consider
638 -- f{-u1-} = 1 -- Local decl
640 -- f{-u2-} = 2 -- Exported decl
642 -- The second exported decl must 'get' the name 'f', so we
643 -- have to put 'f' in the avoids list before we get to the first
644 -- decl. tidyTopId then does a no-op on exported binders.
645 init_occ_env = initTidyOccEnv avoids
648 search :: [(Id,Id)] -- The work-list: (external id, referrring id)
649 -- Make a tidy, external Name for the external id,
650 -- add it to the UnfoldEnv, and do the same for the
651 -- transitive closure of Ids it refers to
652 -- The referring id is used to generate a tidy
653 --- name for the external id
654 -> UnfoldEnv -- id -> (new Name, show_unfold)
655 -> TidyOccEnv -- occ env for choosing new Names
656 -> IO (UnfoldEnv, TidyOccEnv)
658 search [] unfold_env occ_env = return (unfold_env, occ_env)
660 search ((idocc,referrer) : rest) unfold_env occ_env
661 | idocc `elemVarEnv` unfold_env = search rest unfold_env occ_env
663 (occ_env', name') <- tidyTopName mod nc_var (Just referrer) occ_env idocc
665 (new_ids, show_unfold)
666 | omit_prags = ([], False)
667 | otherwise = addExternal expose_all refined_id
669 -- 'idocc' is an *occurrence*, but we need to see the
670 -- unfolding in the *definition*; so look up in binder_set
671 refined_id = case lookupVarSet binder_set idocc of
673 Nothing -> WARN( True, ppr idocc ) idocc
675 unfold_env' = extendVarEnv unfold_env idocc (name',show_unfold)
676 referrer' | isExportedId refined_id = refined_id
677 | otherwise = referrer
679 search (zip new_ids (repeat referrer') ++ rest) unfold_env' occ_env'
681 tidy_internal :: [Id] -> UnfoldEnv -> TidyOccEnv
682 -> IO (UnfoldEnv, TidyOccEnv)
683 tidy_internal [] unfold_env occ_env = return (unfold_env,occ_env)
684 tidy_internal (id:ids) unfold_env occ_env = do
685 (occ_env', name') <- tidyTopName mod nc_var Nothing occ_env id
686 let unfold_env' = extendVarEnv unfold_env id (name',False)
687 tidy_internal ids unfold_env' occ_env'
689 addExternal :: Bool -> Id -> ([Id],Bool)
690 addExternal expose_all id = (new_needed_ids, show_unfold)
692 new_needed_ids = unfold_ids ++
693 filter (\id -> isLocalId id &&
694 not (id `elemVarSet` unfold_set))
695 (varSetElems spec_ids) -- XXX non-det ordering
698 never_active = isNeverActive (inlinePragmaActivation (inlinePragInfo idinfo))
699 loop_breaker = isNonRuleLoopBreaker (occInfo idinfo)
700 bottoming_fn = isBottomingSig (strictnessInfo idinfo `orElse` topSig)
701 spec_ids = specInfoFreeVars (specInfo idinfo)
703 -- Stuff to do with the Id's unfolding
704 -- We leave the unfolding there even if there is a worker
705 -- In GHCI the unfolding is used by importers
706 show_unfold = isJust mb_unfold_ids
707 (unfold_set, unfold_ids) = mb_unfold_ids `orElse` (emptyVarSet, [])
709 mb_unfold_ids :: Maybe (IdSet, [Id]) -- Nothing => don't unfold
710 mb_unfold_ids = case unfoldingInfo idinfo of
711 CoreUnfolding { uf_tmpl = unf_rhs, uf_src = src, uf_guidance = guide }
712 | show_unfolding src guide
713 -> Just (exprFvsInOrder unf_rhs)
714 DFunUnfolding _ ops -> Just (exprsFvsInOrder ops)
717 show_unfolding unf_source unf_guidance
718 = expose_all -- 'expose_all' says to expose all
719 -- unfoldings willy-nilly
721 || isInlineRuleSource unf_source -- Always expose things whose
722 -- source is an inline rule
724 || not (bottoming_fn -- No need to inline bottom functions
725 || never_active -- Or ones that say not to
726 || loop_breaker -- Or that are loop breakers
727 || neverUnfoldGuidance unf_guidance)
729 -- We want a deterministic free-variable list. exprFreeVars gives us
730 -- a VarSet, which is in a non-deterministic order when converted to a
731 -- list. Hence, here we define a free-variable finder that returns
732 -- the free variables in the order that they are encountered.
734 -- Note [choosing external names]
736 exprFvsInOrder :: CoreExpr -> (VarSet, [Id])
737 exprFvsInOrder e = run (dffvExpr e)
739 exprsFvsInOrder :: [CoreExpr] -> (VarSet, [Id])
740 exprsFvsInOrder es = run (mapM_ dffvExpr es)
742 run :: DFFV () -> (VarSet, [Id])
743 run (DFFV m) = case m emptyVarSet [] of
744 (set,ids,_) -> (set,ids)
746 newtype DFFV a = DFFV (VarSet -> [Var] -> (VarSet,[Var],a))
748 instance Monad DFFV where
749 return a = DFFV $ \set ids -> (set, ids, a)
750 (DFFV m) >>= k = DFFV $ \set ids ->
752 (set',ids',a) -> case k a of
753 DFFV f -> f set' ids'
755 insert :: Var -> DFFV ()
756 insert v = DFFV $ \ set ids -> case () of
757 _ | v `elemVarSet` set -> (set,ids,())
758 | otherwise -> (extendVarSet set v, v:ids, ())
760 dffvExpr :: CoreExpr -> DFFV ()
761 dffvExpr e = go emptyVarSet e
763 go scope e = case e of
764 Var v | isLocalId v && not (v `elemVarSet` scope) -> insert v
765 App e1 e2 -> do go scope e1; go scope e2
766 Lam v e -> go (extendVarSet scope v) e
767 Note _ e -> go scope e
768 Cast e _ -> go scope e
769 Let (NonRec x r) e -> do go scope r; go (extendVarSet scope x) e
770 Let (Rec prs) e -> do let scope' = extendVarSetList scope (map fst prs)
771 mapM_ (go scope') (map snd prs)
773 Case e b _ as -> do go scope e
774 mapM_ (go_alt (extendVarSet scope b)) as
777 go_alt scope (_,xs,r) = go (extendVarSetList scope xs) r
781 --------------------------------------------------------------------
783 -- This is where we set names to local/global based on whether they really are
784 -- externally visible (see comment at the top of this module). If the name
785 -- was previously local, we have to give it a unique occurrence name if
786 -- we intend to externalise it.
789 tidyTopName :: Module -> IORef NameCache -> Maybe Id -> TidyOccEnv
790 -> Id -> IO (TidyOccEnv, Name)
791 tidyTopName mod nc_var maybe_ref occ_env id
792 | global && internal = return (occ_env, localiseName name)
794 | global && external = return (occ_env, name)
795 -- Global names are assumed to have been allocated by the renamer,
796 -- so they already have the "right" unique
797 -- And it's a system-wide unique too
799 -- Now we get to the real reason that all this is in the IO Monad:
800 -- we have to update the name cache in a nice atomic fashion
802 | local && internal = do { nc <- readIORef nc_var
803 ; let (nc', new_local_name) = mk_new_local nc
804 ; writeIORef nc_var nc'
805 ; return (occ_env', new_local_name) }
806 -- Even local, internal names must get a unique occurrence, because
807 -- if we do -split-objs we externalise the name later, in the code generator
809 -- Similarly, we must make sure it has a system-wide Unique, because
810 -- the byte-code generator builds a system-wide Name->BCO symbol table
812 | local && external = do { nc <- readIORef nc_var
813 ; let (nc', new_external_name) = mk_new_external nc
814 ; writeIORef nc_var nc'
815 ; return (occ_env', new_external_name) }
817 | otherwise = panic "tidyTopName"
820 external = isJust maybe_ref
821 global = isExternalName name
823 internal = not external
824 loc = nameSrcSpan name
826 old_occ = nameOccName name
828 | Just ref <- maybe_ref, ref /= id =
829 mkOccName (occNameSpace old_occ) $
831 ref_str = occNameString (getOccName ref)
832 occ_str = occNameString old_occ
836 -- workers: the worker for a function already
837 -- includes the occname for its parent, so there's
838 -- no need to prepend the referrer.
839 _other | isSystemName name -> ref_str
840 | otherwise -> ref_str ++ '_' : occ_str
841 -- If this name was system-generated, then don't bother
842 -- to retain its OccName, just use the referrer. These
843 -- system-generated names will become "f1", "f2", etc. for
845 | otherwise = old_occ
847 (occ_env', occ') = tidyOccName occ_env new_occ
849 mk_new_local nc = (nc { nsUniqs = us2 }, mkInternalName uniq occ' loc)
851 (us1, us2) = splitUniqSupply (nsUniqs nc)
852 uniq = uniqFromSupply us1
854 mk_new_external nc = allocateGlobalBinder nc mod occ' loc
855 -- If we want to externalise a currently-local name, check
856 -- whether we have already assigned a unique for it.
857 -- If so, use it; if not, extend the table.
858 -- All this is done by allcoateGlobalBinder.
859 -- This is needed when *re*-compiling a module in GHCi; we must
860 -- use the same name for externally-visible things as we did before.
864 findExternalRules :: Bool -- Omit pragmas
866 -> [CoreRule] -- Local rules for imported fns
867 -> UnfoldEnv -- Ids that are exported, so we need their rules
869 -- The complete rules are gotten by combining
870 -- a) local rules for imported Ids
871 -- b) rules embedded in the top-level Ids
872 findExternalRules omit_prags binds imp_id_rules unfold_env
874 | otherwise = filterOut internal_rule (imp_id_rules ++ local_rules)
877 | id <- bindersOfBinds binds,
879 rule <- idCoreRules id
883 = any (not . external_id) (varSetElems (ruleLhsFreeIds rule))
884 -- Don't export a rule whose LHS mentions a locally-defined
885 -- Id that is completely internal (i.e. not visible to an
889 | Just (name,_) <- lookupVarEnv unfold_env id = isExternalName name
893 Note [Which rules to expose]
894 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
895 findExternalRules filters imp_rules to avoid binders that
896 aren't externally visible; but the externally-visible binders
897 are computed (by findExternalIds) assuming that all orphan
898 rules are externalised (see init_ext_ids in function
899 'search'). So in fact we may export more than we need.
900 (It's a sort of mutual recursion.)
902 %************************************************************************
904 \subsection{Step 2: top-level tidying}
906 %************************************************************************
910 -- TopTidyEnv: when tidying we need to know
911 -- * nc_var: The NameCache, containing a unique supply and any pre-ordained Names.
912 -- These may have arisen because the
913 -- renamer read in an interface file mentioning M.$wf, say,
914 -- and assigned it unique r77. If, on this compilation, we've
915 -- invented an Id whose name is $wf (but with a different unique)
916 -- we want to rename it to have unique r77, so that we can do easy
917 -- comparisons with stuff from the interface file
919 -- * occ_env: The TidyOccEnv, which tells us which local occurrences
922 -- * subst_env: A Var->Var mapping that substitutes the new Var for the old
924 tidyTopBinds :: HscEnv
928 -> (TidyEnv, [CoreBind])
930 tidyTopBinds hsc_env unfold_env init_occ_env binds
931 = tidy init_env binds
933 init_env = (init_occ_env, emptyVarEnv)
935 this_pkg = thisPackage (hsc_dflags hsc_env)
937 tidy env [] = (env, [])
938 tidy env (b:bs) = let (env1, b') = tidyTopBind this_pkg unfold_env env b
939 (env2, bs') = tidy env1 bs
943 ------------------------
944 tidyTopBind :: PackageId
948 -> (TidyEnv, CoreBind)
950 tidyTopBind this_pkg unfold_env (occ_env,subst1) (NonRec bndr rhs)
951 = (tidy_env2, NonRec bndr' rhs')
953 Just (name',show_unfold) = lookupVarEnv unfold_env bndr
954 caf_info = hasCafRefs this_pkg subst1 (idArity bndr) rhs
955 (bndr', rhs') = tidyTopPair show_unfold tidy_env2 caf_info name' (bndr, rhs)
956 subst2 = extendVarEnv subst1 bndr bndr'
957 tidy_env2 = (occ_env, subst2)
959 tidyTopBind this_pkg unfold_env (occ_env,subst1) (Rec prs)
960 = (tidy_env2, Rec prs')
962 prs' = [ tidyTopPair show_unfold tidy_env2 caf_info name' (id,rhs)
964 let (name',show_unfold) =
965 expectJust "tidyTopBind" $ lookupVarEnv unfold_env id
968 subst2 = extendVarEnvList subst1 (bndrs `zip` map fst prs')
969 tidy_env2 = (occ_env, subst2)
973 -- the CafInfo for a recursive group says whether *any* rhs in
974 -- the group may refer indirectly to a CAF (because then, they all do).
976 | or [ mayHaveCafRefs (hasCafRefs this_pkg subst1 (idArity bndr) rhs)
977 | (bndr,rhs) <- prs ] = MayHaveCafRefs
978 | otherwise = NoCafRefs
980 -----------------------------------------------------------
981 tidyTopPair :: Bool -- show unfolding
982 -> TidyEnv -- The TidyEnv is used to tidy the IdInfo
983 -- It is knot-tied: don't look at it!
986 -> (Id, CoreExpr) -- Binder and RHS before tidying
988 -- This function is the heart of Step 2
989 -- The rec_tidy_env is the one to use for the IdInfo
990 -- It's necessary because when we are dealing with a recursive
991 -- group, a variable late in the group might be mentioned
992 -- in the IdInfo of one early in the group
994 tidyTopPair show_unfold rhs_tidy_env caf_info name' (bndr, rhs)
997 bndr1 = mkGlobalId details name' ty' idinfo'
998 details = idDetails bndr -- Preserve the IdDetails
999 ty' = tidyTopType (idType bndr)
1000 rhs1 = tidyExpr rhs_tidy_env rhs
1001 idinfo' = tidyTopIdInfo rhs_tidy_env name' rhs rhs1 (idInfo bndr)
1002 show_unfold caf_info
1004 -- tidyTopIdInfo creates the final IdInfo for top-level
1005 -- binders. There are two delicate pieces:
1007 -- * Arity. After CoreTidy, this arity must not change any more.
1008 -- Indeed, CorePrep must eta expand where necessary to make
1009 -- the manifest arity equal to the claimed arity.
1011 -- * CAF info. This must also remain valid through to code generation.
1012 -- We add the info here so that it propagates to all
1013 -- occurrences of the binders in RHSs, and hence to occurrences in
1014 -- unfoldings, which are inside Ids imported by GHCi. Ditto RULES.
1015 -- CoreToStg makes use of this when constructing SRTs.
1016 tidyTopIdInfo :: TidyEnv -> Name -> CoreExpr -> CoreExpr
1017 -> IdInfo -> Bool -> CafInfo -> IdInfo
1018 tidyTopIdInfo rhs_tidy_env name orig_rhs tidy_rhs idinfo show_unfold caf_info
1019 | not is_external -- For internal Ids (not externally visible)
1020 = vanillaIdInfo -- we only need enough info for code generation
1021 -- Arity and strictness info are enough;
1022 -- c.f. CoreTidy.tidyLetBndr
1023 `setCafInfo` caf_info
1024 `setArityInfo` arity
1025 `setStrictnessInfo` final_sig
1027 | otherwise -- Externally-visible Ids get the whole lot
1029 `setCafInfo` caf_info
1030 `setArityInfo` arity
1031 `setStrictnessInfo` final_sig
1032 `setOccInfo` robust_occ_info
1033 `setInlinePragInfo` (inlinePragInfo idinfo)
1034 `setUnfoldingInfo` unfold_info
1035 -- NB: we throw away the Rules
1036 -- They have already been extracted by findExternalRules
1038 is_external = isExternalName name
1040 --------- OccInfo ------------
1041 robust_occ_info = zapFragileOcc (occInfo idinfo)
1042 -- It's important to keep loop-breaker information
1043 -- when we are doing -fexpose-all-unfoldings
1045 --------- Strictness ------------
1046 final_sig | Just sig <- strictnessInfo idinfo
1047 = WARN( _bottom_hidden sig, ppr name ) Just sig
1048 | Just (_, sig) <- mb_bot_str = Just sig
1049 | otherwise = Nothing
1051 -- If the cheap-and-cheerful bottom analyser can see that
1052 -- the RHS is bottom, it should jolly well be exposed
1053 _bottom_hidden id_sig = case mb_bot_str of
1055 Just (arity, _) -> not (appIsBottom id_sig arity)
1057 mb_bot_str = exprBotStrictness_maybe orig_rhs
1059 --------- Unfolding ------------
1060 unf_info = unfoldingInfo idinfo
1061 unfold_info | show_unfold = tidyUnfolding rhs_tidy_env tidy_rhs final_sig unf_info
1062 | otherwise = noUnfolding
1063 -- NB: do *not* expose the worker if show_unfold is off,
1064 -- because that means this thing is a loop breaker or
1065 -- marked NOINLINE or something like that
1066 -- This is important: if you expose the worker for a loop-breaker
1067 -- then you can make the simplifier go into an infinite loop, because
1068 -- in effect the unfolding is exposed. See Trac #1709
1070 -- You might think that if show_unfold is False, then the thing should
1071 -- not be w/w'd in the first place. But a legitimate reason is this:
1072 -- the function returns bottom
1073 -- In this case, show_unfold will be false (we don't expose unfoldings
1074 -- for bottoming functions), but we might still have a worker/wrapper
1075 -- split (see Note [Worker-wrapper for bottoming functions] in WorkWrap.lhs
1077 --------- Arity ------------
1078 -- Usually the Id will have an accurate arity on it, because
1079 -- the simplifier has just run, but not always.
1080 -- One case I found was when the last thing the simplifier
1081 -- did was to let-bind a non-atomic argument and then float
1082 -- it to the top level. So it seems more robust just to
1084 arity = exprArity orig_rhs
1088 ------------ Unfolding --------------
1089 tidyUnfolding :: TidyEnv -> CoreExpr -> Maybe StrictSig -> Unfolding -> Unfolding
1090 tidyUnfolding tidy_env _ _ (DFunUnfolding con ids)
1091 = DFunUnfolding con (map (tidyExpr tidy_env) ids)
1092 tidyUnfolding tidy_env tidy_rhs strict_sig
1093 unf@(CoreUnfolding { uf_tmpl = unf_rhs, uf_src = src })
1094 | isInlineRuleSource src
1095 = unf { uf_tmpl = tidyExpr tidy_env unf_rhs, -- Preserves OccInfo
1096 uf_src = tidyInl tidy_env src }
1098 = mkTopUnfolding is_bot tidy_rhs
1100 is_bot = case strict_sig of
1101 Just sig -> isBottomingSig sig
1104 tidyUnfolding _ _ _ unf = unf
1106 tidyInl :: TidyEnv -> UnfoldingSource -> UnfoldingSource
1107 tidyInl tidy_env (InlineWrapper w) = InlineWrapper (tidyVarOcc tidy_env w)
1108 tidyInl _ inl_info = inl_info
1111 %************************************************************************
1113 \subsection{Figuring out CafInfo for an expression}
1115 %************************************************************************
1117 hasCafRefs decides whether a top-level closure can point into the dynamic heap.
1118 We mark such things as `MayHaveCafRefs' because this information is
1119 used to decide whether a particular closure needs to be referenced
1122 There are two reasons for setting MayHaveCafRefs:
1123 a) The RHS is a CAF: a top-level updatable thunk.
1124 b) The RHS refers to something that MayHaveCafRefs
1126 Possible improvement: In an effort to keep the number of CAFs (and
1127 hence the size of the SRTs) down, we could also look at the expression and
1128 decide whether it requires a small bounded amount of heap, so we can ignore
1129 it as a CAF. In these cases however, we would need to use an additional
1130 CAF list to keep track of non-collectable CAFs.
1133 hasCafRefs :: PackageId -> VarEnv Var -> Arity -> CoreExpr -> CafInfo
1134 hasCafRefs this_pkg p arity expr
1135 | is_caf || mentions_cafs
1137 | otherwise = NoCafRefs
1139 mentions_cafs = isFastTrue (cafRefs p expr)
1140 is_caf = not (arity > 0 || rhsIsStatic this_pkg expr)
1142 -- NB. we pass in the arity of the expression, which is expected
1143 -- to be calculated by exprArity. This is because exprArity
1144 -- knows how much eta expansion is going to be done by
1145 -- CorePrep later on, and we don't want to duplicate that
1146 -- knowledge in rhsIsStatic below.
1148 cafRefs :: VarEnv Id -> Expr a -> FastBool
1150 -- imported Ids first:
1151 | not (isLocalId id) = fastBool (mayHaveCafRefs (idCafInfo id))
1152 -- now Ids local to this module:
1154 case lookupVarEnv p id of
1155 Just id' -> fastBool (mayHaveCafRefs (idCafInfo id'))
1156 Nothing -> fastBool False
1158 cafRefs _ (Lit _) = fastBool False
1159 cafRefs p (App f a) = fastOr (cafRefs p f) (cafRefs p) a
1160 cafRefs p (Lam _ e) = cafRefs p e
1161 cafRefs p (Let b e) = fastOr (cafRefss p (rhssOfBind b)) (cafRefs p) e
1162 cafRefs p (Case e _bndr _ alts) = fastOr (cafRefs p e) (cafRefss p) (rhssOfAlts alts)
1163 cafRefs p (Note _n e) = cafRefs p e
1164 cafRefs p (Cast e _co) = cafRefs p e
1165 cafRefs _ (Type _) = fastBool False
1167 cafRefss :: VarEnv Id -> [Expr a] -> FastBool
1168 cafRefss _ [] = fastBool False
1169 cafRefss p (e:es) = fastOr (cafRefs p e) (cafRefss p) es
1171 fastOr :: FastBool -> (a -> FastBool) -> a -> FastBool
1172 -- hack for lazy-or over FastBool.
1173 fastOr a f x = fastBool (isFastTrue a || isFastTrue (f x))