2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section{Tidying up Core}
12 #include "HsVersions.h"
14 import CmdLineOpts ( DynFlags, DynFlag(..), opt_OmitInterfacePragmas )
16 import CoreUnfold ( noUnfolding, mkTopUnfolding, okToUnfoldInHiFile )
17 import CoreUtils ( exprArity )
18 import CoreFVs ( ruleSomeFreeVars, exprSomeFreeVars )
19 import CoreLint ( showPass, endPass )
22 import Var ( Id, Var )
23 import Id ( idType, idInfo, idName, isExportedId,
24 idCafInfo, mkId, isLocalId, isImplicitId,
25 idFlavour, modifyIdInfo, idArity
27 import IdInfo {- loads of stuff -}
28 import Name ( getOccName, nameOccName, globaliseName, setNameOcc,
29 localiseName, mkLocalName, isGlobalName, isDllName
31 import OccName ( TidyOccEnv, initTidyOccEnv, tidyOccName )
32 import Type ( tidyTopType, tidyType, tidyTyVar )
33 import Module ( Module, moduleName )
34 import PrimOp ( PrimOp(..), setCCallUnique )
35 import HscTypes ( PersistentCompilerState( pcs_PRS ),
36 PersistentRenamerState( prsOrig ),
37 NameSupply( nsNames ), OrigNameCache
40 import DataCon ( DataCon, dataConName )
41 import Literal ( isLitLitLit )
42 import FiniteMap ( lookupFM, addToFM )
43 import Maybes ( maybeToBool, orElse )
44 import ErrUtils ( showPass )
45 import PprCore ( pprIdCoreRule )
46 import SrcLoc ( noSrcLoc )
47 import UniqFM ( mapUFM )
50 import List ( partition )
51 import Util ( mapAccumL )
56 %************************************************************************
58 \subsection{What goes on}
60 %************************************************************************
66 Step 1: Figure out external Ids
67 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
68 First we figure out which Ids are "external" Ids. An
69 "external" Id is one that is visible from outside the compilation
71 a) the user exported ones
72 b) ones mentioned in the unfoldings, workers,
73 or rules of externally-visible ones
74 This exercise takes a sweep of the bindings bottom to top. Actually,
75 in Step 2 we're also going to need to know which Ids should be
76 exported with their unfoldings, so we produce not an IdSet but an
80 Step 2: Tidy the program
81 ~~~~~~~~~~~~~~~~~~~~~~~~
82 Next we traverse the bindings top to bottom. For each top-level
85 - Make all external Ids have Global names and vice versa
86 This is used by the code generator to decide whether
87 to make the label externally visible
89 - Give external ids a "tidy" occurrence name. This means
90 we can print them in interface files without confusing
91 "x" (unique 5) with "x" (unique 10).
93 - Give external Ids the same Unique as they had before
94 if the name is in the renamer's name cache
96 - Clone all local Ids. This means that Tidy Core has the property
97 that all Ids are unique, rather than the weaker guarantee of
98 no clashes which the simplifier provides.
100 - Give each dynamic CCall occurrence a fresh unique; this is
101 rather like the cloning step above.
103 - Give the Id its UTTERLY FINAL IdInfo; in ptic,
104 * Its flavour becomes ConstantId, reflecting the fact that
105 from now on we regard it as a constant, not local, Id
107 * its unfolding, if it should have one
109 * its arity, computed from the number of visible lambdas
111 * its CAF info, computed from what is free in its RHS
114 Finally, substitute these new top-level binders consistently
115 throughout, including in unfoldings. We also tidy binders in
116 RHSs, so that they print nicely in interfaces.
119 tidyCorePgm :: DynFlags -> Module
120 -> PersistentCompilerState
121 -> [CoreBind] -> [IdCoreRule]
122 -> IO (PersistentCompilerState, [CoreBind], [IdCoreRule])
123 tidyCorePgm dflags mod pcs binds_in orphans_in
124 = do { showPass dflags "Tidy Core"
126 ; let ext_ids = findExternalSet binds_in orphans_in
128 ; us <- mkSplitUniqSupply 't' -- for "tidy"
130 ; let ((us1, orig_env', occ_env, subst_env), binds_out)
131 = mapAccumL (tidyTopBind mod ext_ids)
132 (init_tidy_env us) binds_in
134 ; let (orphans_out, _)
135 = initUs us1 (tidyIdRules (occ_env,subst_env) orphans_in)
137 ; let prs' = prs { prsOrig = orig { nsNames = orig_env' } }
138 pcs' = pcs { pcs_PRS = prs' }
140 ; endPass dflags "Tidy Core" Opt_D_dump_simpl binds_out
142 ; return (pcs', binds_out, orphans_out)
145 -- We also make sure to avoid any exported binders. Consider
146 -- f{-u1-} = 1 -- Local decl
148 -- f{-u2-} = 2 -- Exported decl
150 -- The second exported decl must 'get' the name 'f', so we
151 -- have to put 'f' in the avoids list before we get to the first
152 -- decl. tidyTopId then does a no-op on exported binders.
155 orig_env = nsNames orig
157 init_tidy_env us = (us, orig_env, initTidyOccEnv avoids, emptyVarEnv)
158 avoids = [getOccName bndr | bndr <- bindersOfBinds binds_in,
159 isGlobalName (idName bndr)]
163 %************************************************************************
165 \subsection{Step 1: finding externals}
167 %************************************************************************
170 findExternalSet :: [CoreBind] -> [IdCoreRule]
171 -> IdEnv Bool -- True <=> show unfolding
172 -- Step 1 from the notes above
173 findExternalSet binds orphan_rules
174 = foldr find init_needed binds
176 orphan_rule_ids :: IdSet
177 orphan_rule_ids = unionVarSets [ ruleSomeFreeVars isIdAndLocal rule
178 | (_, rule) <- orphan_rules]
179 init_needed :: IdEnv Bool
180 init_needed = mapUFM (\_ -> False) orphan_rule_ids
181 -- The mapUFM is a bit cheesy. It is a cheap way
182 -- to turn the set of orphan_rule_ids, which we use to initialise
183 -- the sweep, into a mapping saying 'don't expose unfolding'
184 -- (When we come to the binding site we may change our mind, of course.)
186 find (NonRec id rhs) needed
187 | need_id needed id = addExternal (id,rhs) needed
189 find (Rec prs) needed = find_prs prs needed
191 -- For a recursive group we have to look for a fixed point
193 | null needed_prs = needed
194 | otherwise = find_prs other_prs new_needed
196 (needed_prs, other_prs) = partition (need_pr needed) prs
197 new_needed = foldr addExternal needed needed_prs
199 -- The 'needed' set contains the Ids that are needed by earlier
200 -- interface file emissions. If the Id isn't in this set, and isn't
201 -- exported, there's no need to emit anything
202 need_id needed_set id = id `elemVarEnv` needed_set || isExportedId id
203 need_pr needed_set (id,rhs) = need_id needed_set id
205 isIdAndLocal id = isId id && isLocalId id
207 addExternal :: (Id,CoreExpr) -> IdEnv Bool -> IdEnv Bool
208 -- The Id is needed; extend the needed set
209 -- with it and its dependents (free vars etc)
210 addExternal (id,rhs) needed
211 = extendVarEnv (foldVarSet add_occ needed new_needed_ids)
214 add_occ id needed = extendVarEnv needed id False
215 -- "False" because we don't know we need the Id's unfolding
216 -- We'll override it later when we find the binding site
218 new_needed_ids | opt_OmitInterfacePragmas = emptyVarSet
219 | otherwise = worker_ids `unionVarSet`
220 unfold_ids `unionVarSet`
224 dont_inline = isNeverInlinePrag (inlinePragInfo idinfo)
225 loop_breaker = isLoopBreaker (occInfo idinfo)
226 bottoming_fn = isBottomingStrictness (strictnessInfo idinfo)
227 spec_ids = rulesRhsFreeVars (specInfo idinfo)
228 worker_info = workerInfo idinfo
230 -- Stuff to do with the Id's unfolding
231 -- The simplifier has put an up-to-date unfolding
232 -- in the IdInfo, but the RHS will do just as well
233 unfolding = unfoldingInfo idinfo
234 rhs_is_small = not (neverUnfold unfolding)
236 -- We leave the unfolding there even if there is a worker
237 -- In GHCI the unfolding is used by importers
238 -- When writing an interface file, we omit the unfolding
239 -- if there is a worker
240 show_unfold = not bottoming_fn && -- Not necessary
243 rhs_is_small && -- Small enough
244 okToUnfoldInHiFile rhs -- No casms etc
246 unfold_ids | show_unfold = exprSomeFreeVars isIdAndLocal rhs
247 | otherwise = emptyVarSet
249 worker_ids = case worker_info of
250 HasWorker work_id _ -> unitVarSet work_id
251 otherwise -> emptyVarSet
255 %************************************************************************
257 \subsection{Step 2: top-level tidying}
259 %************************************************************************
263 type TopTidyEnv = (UniqSupply, OrigNameCache, TidyOccEnv, VarEnv Var)
265 -- TopTidyEnv: when tidying we need to know
266 -- * orig_env: Any pre-ordained Names. These may have arisen because the
267 -- renamer read in an interface file mentioning M.$wf, say,
268 -- and assigned it unique r77. If, on this compilation, we've
269 -- invented an Id whose name is $wf (but with a different unique)
270 -- we want to rename it to have unique r77, so that we can do easy
271 -- comparisons with stuff from the interface file
273 -- * occ_env: The TidyOccEnv, which tells us which local occurrences
276 -- * subst_env: A Var->Var mapping that substitutes the new Var for the old
278 -- * uniqsuppy: so we can clone any Ids with non-preordained names.
284 tidyTopBind :: Module
285 -> IdEnv Bool -- Domain = Ids that should be external
286 -- True <=> their unfolding is external too
287 -> TopTidyEnv -> CoreBind
288 -> (TopTidyEnv, CoreBind)
290 tidyTopBind mod ext_ids env (NonRec bndr rhs)
291 = ((us2,orig,occ,subst) , NonRec bndr' rhs')
293 ((us1,orig,occ,subst), bndr')
294 = tidyTopBinder mod ext_ids tidy_env rhs' caf_info env bndr
295 tidy_env = (occ,subst)
296 caf_info = hasCafRefs (const True) rhs'
297 (rhs',us2) = initUs us1 (tidyExpr tidy_env rhs)
299 tidyTopBind mod ext_ids env (Rec prs)
300 = (final_env, Rec prs')
302 (final_env@(_,_,occ,subst), prs') = mapAccumL do_one env prs
303 final_tidy_env = (occ,subst)
305 do_one env (bndr,rhs)
306 = ((us',orig,occ,subst), (bndr',rhs'))
308 ((us,orig,occ,subst), bndr')
309 = tidyTopBinder mod ext_ids final_tidy_env rhs' caf_info env bndr
310 (rhs', us') = initUs us (tidyExpr final_tidy_env rhs)
312 -- the CafInfo for a recursive group says whether *any* rhs in
313 -- the group may refer indirectly to a CAF (because then, they all do).
314 (bndrs, rhss) = unzip prs'
315 caf_info = hasCafRefss pred rhss
316 pred v = v `notElem` bndrs
319 tidyTopBinder :: Module -> IdEnv Bool
320 -> TidyEnv -> CoreExpr -> CafInfo
321 -- The TidyEnv is used to tidy the IdInfo
322 -- The expr is the already-tided RHS
323 -- Both are knot-tied: don't look at them!
324 -> TopTidyEnv -> Id -> (TopTidyEnv, Id)
326 tidyTopBinder mod ext_ids tidy_env rhs caf_info
327 env@(us, orig_env2, occ_env2, subst_env2) id
329 | isImplicitId id -- Don't mess with constructors,
330 = (env, id) -- record selectors, and the like
333 -- This function is the heart of Step 2
334 -- The second env is the one to use for the IdInfo
335 -- It's necessary because when we are dealing with a recursive
336 -- group, a variable late in the group might be mentioned
337 -- in the IdInfo of one early in the group
339 -- The rhs is already tidied
341 = ((us_r, orig_env', occ_env', subst_env'), id')
343 (us_l, us_r) = splitUniqSupply us
345 (orig_env', occ_env', name') = tidyTopName mod orig_env2 occ_env2
348 ty' = tidyTopType (idType id)
349 idinfo' = tidyIdInfo us_l tidy_env
350 is_external unfold_info arity_info caf_info id
352 id' = mkId name' ty' idinfo'
353 subst_env' = extendVarEnv subst_env2 id id'
355 maybe_external = lookupVarEnv ext_ids id
356 is_external = maybeToBool maybe_external
358 -- Expose an unfolding if ext_ids tells us to
359 show_unfold = maybe_external `orElse` False
360 unfold_info | show_unfold = mkTopUnfolding rhs
361 | otherwise = noUnfolding
363 arity_info = exprArity rhs
366 tidyIdInfo us tidy_env is_external unfold_info arity_info caf_info id
367 | opt_OmitInterfacePragmas || not is_external
368 -- No IdInfo if the Id isn't external, or if we don't have -O
369 = mkIdInfo new_flavour caf_info
370 `setStrictnessInfo` strictnessInfo core_idinfo
371 `setArityInfo` ArityExactly arity_info
372 -- Keep strictness, arity and CAF info; it's used by the code generator
375 = let (rules', _) = initUs us (tidyRules tidy_env (specInfo core_idinfo))
377 mkIdInfo new_flavour caf_info
378 `setCprInfo` cprInfo core_idinfo
379 `setStrictnessInfo` strictnessInfo core_idinfo
380 `setInlinePragInfo` inlinePragInfo core_idinfo
381 `setUnfoldingInfo` unfold_info
382 `setWorkerInfo` tidyWorker tidy_env arity_info (workerInfo core_idinfo)
384 `setArityInfo` ArityExactly arity_info
385 -- this is the final IdInfo, it must agree with the
386 -- code finally generated (i.e. NO more transformations
389 core_idinfo = idInfo id
390 new_flavour = makeConstantFlavour (flavourInfo core_idinfo)
391 -- A DFunId must stay a DFunId, so that we can gather the
392 -- DFunIds up later. Other local things become ConstantIds.
395 -- This is where we set names to local/global based on whether they really are
396 -- externally visible (see comment at the top of this module). If the name
397 -- was previously local, we have to give it a unique occurrence name if
398 -- we intend to globalise it.
399 tidyTopName mod orig_env occ_env external name
400 | global && internal = (orig_env, occ_env, localiseName name)
402 | local && internal = (orig_env, occ_env', setNameOcc name occ')
403 -- Even local, internal names must get a unique occurrence, because
404 -- if we do -split-objs we globalise the name later, n the code generator
406 | global && external = (orig_env, occ_env, name)
407 -- Global names are assumed to have been allocated by the renamer,
408 -- so they already have the "right" unique
410 | local && external = case lookupFM orig_env key of
411 Just orig -> (orig_env, occ_env', orig)
412 Nothing -> (addToFM orig_env key global_name, occ_env', global_name)
413 -- If we want to globalise a currently-local name, check
414 -- whether we have already assigned a unique for it.
415 -- If so, use it; if not, extend the table
418 (occ_env', occ') = tidyOccName occ_env (nameOccName name)
419 key = (moduleName mod, occ')
420 global_name = globaliseName (setNameOcc name occ') mod
421 global = isGlobalName name
423 internal = not external
425 ------------ Worker --------------
426 -- We only treat a function as having a worker if
427 -- the exported arity (which is now the number of visible lambdas)
428 -- is the same as the arity at the moment of the w/w split
429 -- If so, we can safely omit the unfolding inside the wrapper, and
430 -- instead re-generate it from the type/arity/strictness info
431 -- But if the arity has changed, we just take the simple path and
432 -- put the unfolding into the interface file, forgetting the fact
433 -- that it's a wrapper.
435 -- How can this happen? Sometimes we get
436 -- f = coerce t (\x y -> $wf x y)
437 -- at the moment of w/w split; but the eta reducer turns it into
439 -- which is perfectly fine except that the exposed arity so far as
440 -- the code generator is concerned (zero) differs from the arity
441 -- when we did the split (2).
443 -- All this arises because we use 'arity' to mean "exactly how many
444 -- top level lambdas are there" in interface files; but during the
445 -- compilation of this module it means "how many things can I apply
447 tidyWorker tidy_env real_arity (HasWorker work_id wrap_arity)
448 | real_arity == wrap_arity
449 = HasWorker (tidyVarOcc tidy_env work_id) wrap_arity
450 tidyWorker tidy_env real_arity other
453 ------------ Rules --------------
454 tidyIdRules :: TidyEnv -> [IdCoreRule] -> UniqSM [IdCoreRule]
455 tidyIdRules env [] = returnUs []
456 tidyIdRules env ((fn,rule) : rules)
457 = tidyRule env rule `thenUs` \ rule ->
458 tidyIdRules env rules `thenUs` \ rules ->
459 returnUs ((tidyVarOcc env fn, rule) : rules)
461 tidyRules :: TidyEnv -> CoreRules -> UniqSM CoreRules
462 tidyRules env (Rules rules fvs)
463 = mapUs (tidyRule env) rules `thenUs` \ rules ->
464 returnUs (Rules rules (foldVarSet tidy_set_elem emptyVarSet fvs))
466 tidy_set_elem var new_set = extendVarSet new_set (tidyVarOcc env var)
468 tidyRule :: TidyEnv -> CoreRule -> UniqSM CoreRule
469 tidyRule env rule@(BuiltinRule _) = returnUs rule
470 tidyRule env (Rule name vars tpl_args rhs)
471 = tidyBndrs env vars `thenUs` \ (env', vars) ->
472 mapUs (tidyExpr env') tpl_args `thenUs` \ tpl_args ->
473 tidyExpr env' rhs `thenUs` \ rhs ->
474 returnUs (Rule name vars tpl_args rhs)
477 %************************************************************************
479 \subsection{Step 2: inner tidying
481 %************************************************************************
486 -> UniqSM (TidyEnv, CoreBind)
487 tidyBind env (NonRec bndr rhs)
488 = tidyBndrWithRhs env (bndr,rhs) `thenUs` \ (env', bndr') ->
489 tidyExpr env' rhs `thenUs` \ rhs' ->
490 returnUs (env', NonRec bndr' rhs')
492 tidyBind env (Rec prs)
493 = mapAccumLUs tidyBndrWithRhs env prs `thenUs` \ (env', bndrs') ->
494 mapUs (tidyExpr env') (map snd prs) `thenUs` \ rhss' ->
495 returnUs (env', Rec (zip bndrs' rhss'))
498 = fiddleCCall v `thenUs` \ v ->
499 returnUs (Var (tidyVarOcc env v))
501 tidyExpr env (Type ty) = returnUs (Type (tidyType env ty))
502 tidyExpr env (Lit lit) = returnUs (Lit lit)
504 tidyExpr env (App f a)
505 = tidyExpr env f `thenUs` \ f ->
506 tidyExpr env a `thenUs` \ a ->
509 tidyExpr env (Note n e)
510 = tidyExpr env e `thenUs` \ e ->
511 returnUs (Note (tidyNote env n) e)
513 tidyExpr env (Let b e)
514 = tidyBind env b `thenUs` \ (env', b') ->
515 tidyExpr env' e `thenUs` \ e ->
518 tidyExpr env (Case e b alts)
519 = tidyExpr env e `thenUs` \ e ->
520 tidyBndr env b `thenUs` \ (env', b) ->
521 mapUs (tidyAlt env') alts `thenUs` \ alts ->
522 returnUs (Case e b alts)
524 tidyExpr env (Lam b e)
525 = tidyBndr env b `thenUs` \ (env', b) ->
526 tidyExpr env' e `thenUs` \ e ->
530 tidyAlt env (con, vs, rhs)
531 = tidyBndrs env vs `thenUs` \ (env', vs) ->
532 tidyExpr env' rhs `thenUs` \ rhs ->
533 returnUs (con, vs, rhs)
535 tidyNote env (Coerce t1 t2) = Coerce (tidyType env t1) (tidyType env t2)
536 tidyNote env note = note
540 %************************************************************************
542 \subsection{Tidying up non-top-level binders}
544 %************************************************************************
547 tidyVarOcc (_, var_env) v = case lookupVarEnv var_env v of
551 -- tidyBndr is used for lambda and case binders
552 tidyBndr :: TidyEnv -> Var -> UniqSM (TidyEnv, Var)
554 | isTyVar var = returnUs (tidyTyVar env var)
555 | otherwise = tidyId env var vanillaIdInfo
557 tidyBndrs :: TidyEnv -> [Var] -> UniqSM (TidyEnv, [Var])
558 tidyBndrs env vars = mapAccumLUs tidyBndr env vars
560 -- tidyBndrWithRhs is used for let binders
561 tidyBndrWithRhs :: TidyEnv -> (Var, CoreExpr) -> UniqSM (TidyEnv, Var)
562 tidyBndrWithRhs env (id,rhs)
563 = tidyId env id idinfo
565 idinfo = vanillaIdInfo `setArityInfo` ArityExactly (exprArity rhs)
566 -- NB: This throws away the IdInfo of the Id, which we
567 -- no longer need. That means we don't need to
568 -- run over it with env, nor renumber it.
570 tidyId :: TidyEnv -> Id -> IdInfo -> UniqSM (TidyEnv, Id)
571 tidyId env@(tidy_env, var_env) id idinfo
572 = -- Non-top-level variables
573 getUniqueUs `thenUs` \ uniq ->
575 -- Give the Id a fresh print-name, *and* rename its type
576 -- The SrcLoc isn't important now,
577 -- though we could extract it from the Id
578 name' = mkLocalName uniq occ' noSrcLoc
579 (tidy_env', occ') = tidyOccName tidy_env (getOccName id)
580 ty' = tidyType (tidy_env,var_env) (idType id)
581 id' = mkId name' ty' idinfo
582 var_env' = extendVarEnv var_env id id'
584 returnUs ((tidy_env', var_env'), id')
588 = case idFlavour id of
589 PrimOpId (CCallOp ccall) ->
590 -- Make a guaranteed unique name for a dynamic ccall.
591 getUniqueUs `thenUs` \ uniq ->
592 returnUs (modifyIdInfo (`setFlavourInfo`
593 PrimOpId (CCallOp (setCCallUnique ccall uniq))) id)
598 %************************************************************************
600 \subsection{Figuring out CafInfo for an expression}
602 %************************************************************************
604 hasCafRefs decides whether a top-level closure can point into the dynamic heap.
605 We mark such things as `MayHaveCafRefs' because this information is
606 used to decide whether a particular closure needs to be referenced
609 There are two reasons for setting MayHaveCafRefs:
610 a) The RHS is a CAF: a top-level updatable thunk.
611 b) The RHS refers to something that MayHaveCafRefs
613 Possible improvement: In an effort to keep the number of CAFs (and
614 hence the size of the SRTs) down, we could also look at the expression and
615 decide whether it requires a small bounded amount of heap, so we can ignore
616 it as a CAF. In these cases however, we would need to use an additional
617 CAF list to keep track of non-collectable CAFs.
620 hasCafRefs :: (Id -> Bool) -> CoreExpr -> CafInfo
621 -- Only called for the RHS of top-level lets
622 hasCafRefss :: (Id -> Bool) -> [CoreExpr] -> CafInfo
623 -- predicate returns True for a given Id if we look at this Id when
624 -- calculating the result. Used to *avoid* looking at the CafInfo
625 -- field for an Id that is part of the current recursive group.
627 hasCafRefs p expr = if isCAF expr || isFastTrue (cafRefs p expr)
631 -- used for recursive groups. The whole group is set to
632 -- "MayHaveCafRefs" if at least one of the group is a CAF or
633 -- refers to any CAFs.
634 hasCafRefss p exprs = if any isCAF exprs || isFastTrue (cafRefss p exprs)
640 = case idCafInfo id of
641 NoCafRefs -> fastBool False
642 MayHaveCafRefs -> fastBool True
646 cafRefs p (Lit l) = fastBool False
647 cafRefs p (App f a) = cafRefs p f `fastOr` cafRefs p a
648 cafRefs p (Lam x e) = cafRefs p e
649 cafRefs p (Let b e) = cafRefss p (rhssOfBind b) `fastOr` cafRefs p e
650 cafRefs p (Case e bndr alts) = cafRefs p e `fastOr` cafRefss p (rhssOfAlts alts)
651 cafRefs p (Note n e) = cafRefs p e
652 cafRefs p (Type t) = fastBool False
654 cafRefss p [] = fastBool False
655 cafRefss p (e:es) = cafRefs p e `fastOr` cafRefss p es
658 isCAF :: CoreExpr -> Bool
659 -- Only called for the RHS of top-level lets
660 isCAF e = not (rhsIsNonUpd e)
661 {- ToDo: check type for onceness, i.e. non-updatable thunks? -}
663 rhsIsNonUpd :: CoreExpr -> Bool
664 -- True => Value-lambda, constructor, PAP
665 -- This is a bit like CoreUtils.exprIsValue, with the following differences:
666 -- a) scc "foo" (\x -> ...) is updatable (so we catch the right SCC)
668 -- b) (C x xs), where C is a contructors is updatable if the application is
669 -- dynamic: see isDynConApp
671 -- c) don't look through unfolding of f in (f x). I'm suspicious of this one
673 rhsIsNonUpd (Lam b e) = isId b || rhsIsNonUpd e
674 rhsIsNonUpd (Note (SCC _) e) = False
675 rhsIsNonUpd (Note _ e) = rhsIsNonUpd e
676 rhsIsNonUpd other_expr
679 go (Var f) n_args args = idAppIsNonUpd f n_args args
681 go (App f a) n_args args
682 | isTypeArg a = go f n_args args
683 | otherwise = go f (n_args + 1) (a:args)
685 go (Note (SCC _) f) n_args args = False
686 go (Note _ f) n_args args = go f n_args args
688 go other n_args args = False
690 idAppIsNonUpd :: Id -> Int -> [CoreExpr] -> Bool
691 idAppIsNonUpd id n_val_args args
692 = case idFlavour id of
693 DataConId con | not (isDynConApp con args) -> True
694 other -> n_val_args < idArity id
696 isDynConApp :: DataCon -> [CoreExpr] -> Bool
697 isDynConApp con args = isDllName (dataConName con) || any isDynArg args
698 -- Top-level constructor applications can usually be allocated
699 -- statically, but they can't if
700 -- a) the constructor, or any of the arguments, come from another DLL
701 -- b) any of the arguments are LitLits
702 -- (because we can't refer to static labels in other DLLs).
703 -- If this happens we simply make the RHS into an updatable thunk,
704 -- and 'exectute' it rather than allocating it statically.
705 -- All this should match the decision in (see CoreToStg.coreToStgRhs)
708 isDynArg :: CoreExpr -> Bool
709 isDynArg (Var v) = isDllName (idName v)
710 isDynArg (Note _ e) = isDynArg e
711 isDynArg (Lit lit) = isLitLitLit lit
712 isDynArg (App e _) = isDynArg e -- must be a type app
713 isDynArg (Lam _ e) = isDynArg e -- must be a type lam