2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
6 ***************************
8 ***************************
10 1. We attach binding levels to Core bindings, in preparation for floating
11 outwards (@FloatOut@).
13 2. We also let-ify many expressions (notably case scrutinees), so they
14 will have a fighting chance of being floated sensible.
16 3. We clone the binders of any floatable let-binding, so that when it is
17 floated out it will be unique. (This used to be done by the simplifier
18 but the latter now only ensures that there's no shadowing; indeed, even
19 that may not be true.)
21 NOTE: this can't be done using the uniqAway idea, because the variable
22 must be unique in the whole program, not just its current scope,
23 because two variables in different scopes may float out to the
26 NOTE: Very tiresomely, we must apply this substitution to
27 the rules stored inside a variable too.
29 We do *not* clone top-level bindings, because some of them must not change,
30 but we *do* clone bindings that are heading for the top level
33 case x of wild { p -> ...wild... }
34 we substitute x for wild in the RHS of the case alternatives:
35 case x of wild { p -> ...x... }
36 This means that a sub-expression involving x is not "trapped" inside the RHS.
37 And it's not inconvenient because we already have a substitution.
39 Note that this is EXACTLY BACKWARDS from the what the simplifier does.
40 The simplifier tries to get rid of occurrences of x, in favour of wild,
41 in the hope that there will only be one remaining occurrence of x, namely
42 the scrutinee of the case, and we can inline it.
50 incMinorLvl, ltMajLvl, ltLvl, isTopLvl
53 #include "HsVersions.h"
57 import CoreUtils ( exprType, exprIsTrivial, exprIsBottom, mkPiType )
58 import CoreFVs -- all of it
60 import Id ( Id, idType, idFreeTyVars, mkSysLocal, isOneShotLambda, modifyIdInfo,
61 idSpecialisation, idWorkerInfo, setIdInfo
63 import IdInfo ( workerExists, vanillaIdInfo, demandInfo, setDemandInfo )
64 import Var ( Var, setVarUnique )
67 import Name ( getOccName )
68 import OccName ( occNameUserString )
69 import Type ( isUnLiftedType, Type )
70 import BasicTypes ( TopLevelFlag(..) )
71 import Demand ( isStrict, wwLazy )
73 import Util ( sortLt, isSingleton, count )
77 %************************************************************************
79 \subsection{Level numbers}
81 %************************************************************************
84 data Level = Level Int -- Level number of enclosing lambdas
85 Int -- Number of big-lambda and/or case expressions between
86 -- here and the nearest enclosing lambda
89 The {\em level number} on a (type-)lambda-bound variable is the
90 nesting depth of the (type-)lambda which binds it. The outermost lambda
91 has level 1, so (Level 0 0) means that the variable is bound outside any lambda.
93 On an expression, it's the maximum level number of its free
94 (type-)variables. On a let(rec)-bound variable, it's the level of its
95 RHS. On a case-bound variable, it's the number of enclosing lambdas.
97 Top-level variables: level~0. Those bound on the RHS of a top-level
98 definition but ``before'' a lambda; e.g., the \tr{x} in (levels shown
101 a_0 = let b_? = ... in
102 x_1 = ... b ... in ...
105 The main function @lvlExpr@ carries a ``context level'' (@ctxt_lvl@).
106 That's meant to be the level number of the enclosing binder in the
107 final (floated) program. If the level number of a sub-expression is
108 less than that of the context, then it might be worth let-binding the
109 sub-expression so that it will indeed float. This context level starts
113 type LevelledExpr = TaggedExpr Level
114 type LevelledArg = TaggedArg Level
115 type LevelledBind = TaggedBind Level
117 tOP_LEVEL = Level 0 0
119 incMajorLvl :: Level -> Level
120 incMajorLvl (Level major minor) = Level (major+1) 0
122 incMinorLvl :: Level -> Level
123 incMinorLvl (Level major minor) = Level major (minor+1)
125 maxLvl :: Level -> Level -> Level
126 maxLvl l1@(Level maj1 min1) l2@(Level maj2 min2)
127 | (maj1 > maj2) || (maj1 == maj2 && min1 > min2) = l1
130 ltLvl :: Level -> Level -> Bool
131 ltLvl (Level maj1 min1) (Level maj2 min2)
132 = (maj1 < maj2) || (maj1 == maj2 && min1 < min2)
134 ltMajLvl :: Level -> Level -> Bool
135 -- Tells if one level belongs to a difft *lambda* level to another
136 ltMajLvl (Level maj1 _) (Level maj2 _) = maj1 < maj2
138 isTopLvl :: Level -> Bool
139 isTopLvl (Level 0 0) = True
140 isTopLvl other = False
142 instance Outputable Level where
143 ppr (Level maj min) = hcat [ char '<', int maj, char ',', int min, char '>' ]
145 instance Eq Level where
146 (Level maj1 min1) == (Level maj2 min2) = maj1==maj2 && min1==min2
149 %************************************************************************
151 \subsection{Main level-setting code}
153 %************************************************************************
156 setLevels :: Bool -- True <=> float lambdas to top level
161 setLevels float_lams binds us
162 = initLvl us (do_them binds)
164 -- "do_them"'s main business is to thread the monad along
165 -- It gives each top binding the same empty envt, because
166 -- things unbound in the envt have level number zero implicitly
167 do_them :: [CoreBind] -> LvlM [LevelledBind]
169 do_them [] = returnLvl []
171 = lvlTopBind init_env b `thenLvl` \ (lvld_bind, _) ->
172 do_them bs `thenLvl` \ lvld_binds ->
173 returnLvl (lvld_bind : lvld_binds)
175 init_env = initialEnv float_lams
177 lvlTopBind env (NonRec binder rhs)
178 = lvlBind TopLevel tOP_LEVEL env (AnnNonRec binder (freeVars rhs))
179 -- Rhs can have no free vars!
181 lvlTopBind env (Rec pairs)
182 = lvlBind TopLevel tOP_LEVEL env (AnnRec [(b,freeVars rhs) | (b,rhs) <- pairs])
185 %************************************************************************
187 \subsection{Setting expression levels}
189 %************************************************************************
192 lvlExpr :: Level -- ctxt_lvl: Level of enclosing expression
193 -> LevelEnv -- Level of in-scope names/tyvars
194 -> CoreExprWithFVs -- input expression
195 -> LvlM LevelledExpr -- Result expression
198 The @ctxt_lvl@ is, roughly, the level of the innermost enclosing
199 binder. Here's an example
201 v = \x -> ...\y -> let r = case (..x..) of
205 When looking at the rhs of @r@, @ctxt_lvl@ will be 1 because that's
206 the level of @r@, even though it's inside a level-2 @\y@. It's
207 important that @ctxt_lvl@ is 1 and not 2 in @r@'s rhs, because we
208 don't want @lvlExpr@ to turn the scrutinee of the @case@ into an MFE
209 --- because it isn't a *maximal* free expression.
211 If there were another lambda in @r@'s rhs, it would get level-2 as well.
214 lvlExpr _ _ (_, AnnType ty) = returnLvl (Type ty)
215 lvlExpr _ env (_, AnnVar v) = returnLvl (lookupVar env v)
216 lvlExpr _ env (_, AnnLit lit) = returnLvl (Lit lit)
218 lvlExpr ctxt_lvl env (_, AnnApp fun arg)
219 = lvl_fun fun `thenLvl` \ fun' ->
220 lvlMFE False ctxt_lvl env arg `thenLvl` \ arg' ->
221 returnLvl (App fun' arg')
223 lvl_fun (_, AnnCase _ _ _) = lvlMFE True ctxt_lvl env fun
224 lvl_fun other = lvlExpr ctxt_lvl env fun
225 -- We don't do MFE on partial applications generally,
226 -- but we do if the function is big and hairy, like a case
228 lvlExpr ctxt_lvl env (_, AnnNote InlineMe expr)
229 -- Don't float anything out of an InlineMe; hence the tOP_LEVEL
230 = lvlExpr tOP_LEVEL env expr `thenLvl` \ expr' ->
231 returnLvl (Note InlineMe expr')
233 lvlExpr ctxt_lvl env (_, AnnNote note expr)
234 = lvlExpr ctxt_lvl env expr `thenLvl` \ expr' ->
235 returnLvl (Note note expr')
237 -- We don't split adjacent lambdas. That is, given
239 -- we don't float to give
240 -- \x -> let v = x+y in \y -> (v,y)
241 -- Why not? Because partial applications are fairly rare, and splitting
242 -- lambdas makes them more expensive.
244 lvlExpr ctxt_lvl env expr@(_, AnnLam bndr rhs)
245 = lvlMFE True new_lvl new_env body `thenLvl` \ new_body ->
246 returnLvl (glue_binders new_bndrs expr new_body)
248 (bndrs, body) = collect_binders expr
249 (new_lvl, new_bndrs) = lvlLamBndrs ctxt_lvl bndrs
250 new_env = extendLvlEnv env new_bndrs
252 lvlExpr ctxt_lvl env (_, AnnLet bind body)
253 = lvlBind NotTopLevel ctxt_lvl env bind `thenLvl` \ (bind', new_env) ->
254 lvlExpr ctxt_lvl new_env body `thenLvl` \ body' ->
255 returnLvl (Let bind' body')
257 lvlExpr ctxt_lvl env (_, AnnCase expr case_bndr alts)
258 = lvlMFE True ctxt_lvl env expr `thenLvl` \ expr' ->
260 alts_env = extendCaseBndrLvlEnv env expr' case_bndr incd_lvl
262 mapLvl (lvl_alt alts_env) alts `thenLvl` \ alts' ->
263 returnLvl (Case expr' (case_bndr, incd_lvl) alts')
265 incd_lvl = incMinorLvl ctxt_lvl
267 lvl_alt alts_env (con, bs, rhs)
268 = lvlMFE True incd_lvl new_env rhs `thenLvl` \ rhs' ->
269 returnLvl (con, bs', rhs')
271 bs' = [ (b, incd_lvl) | b <- bs ]
272 new_env = extendLvlEnv alts_env bs'
277 go rev_bndrs (_, AnnLam b e) = go (b:rev_bndrs) e
278 go rev_bndrs (_, AnnNote n e) = go rev_bndrs e
279 go rev_bndrs rhs = (reverse rev_bndrs, rhs)
280 -- Ignore notes, because we don't want to split
281 -- a lambda like this (\x -> coerce t (\s -> ...))
282 -- This happens quite a bit in state-transformer programs
284 -- glue_binders puts the lambda back together
285 glue_binders (b:bs) (_, AnnLam _ e) body = Lam b (glue_binders bs e body)
286 glue_binders bs (_, AnnNote n e) body = Note n (glue_binders bs e body)
287 glue_binders [] e body = body
290 @lvlMFE@ is just like @lvlExpr@, except that it might let-bind
291 the expression, so that it can itself be floated.
294 lvlMFE :: Bool -- True <=> strict context [body of case or let]
295 -> Level -- Level of innermost enclosing lambda/tylam
296 -> LevelEnv -- Level of in-scope names/tyvars
297 -> CoreExprWithFVs -- input expression
298 -> LvlM LevelledExpr -- Result expression
300 lvlMFE strict_ctxt ctxt_lvl env (_, AnnType ty)
301 = returnLvl (Type ty)
303 lvlMFE strict_ctxt ctxt_lvl env ann_expr@(fvs, _)
304 | isUnLiftedType ty -- Can't let-bind it
305 || not good_destination
306 || exprIsTrivial expr -- Is trivial
307 || (strict_ctxt && exprIsBottom expr) -- Strict context and is bottom
308 -- e.g. \x -> error "foo"
309 -- No gain from floating this
310 = -- Don't float it out
311 lvlExpr ctxt_lvl env ann_expr
313 | otherwise -- Float it out!
314 = lvlFloatRhs abs_vars dest_lvl env ann_expr `thenLvl` \ expr' ->
315 newLvlVar "lvl" abs_vars ty `thenLvl` \ var ->
316 returnLvl (Let (NonRec (var,dest_lvl) expr')
317 (mkVarApps (Var var) abs_vars))
319 expr = deAnnotate ann_expr
321 dest_lvl = destLevel env fvs (isFunction ann_expr)
322 abs_vars = abstractVars dest_lvl env fvs
324 good_destination = dest_lvl `ltMajLvl` ctxt_lvl -- Escapes a value lambda
325 || (isTopLvl dest_lvl && not strict_ctxt) -- Goes to the top
326 -- A decision to float entails let-binding this thing, and we only do
327 -- that if we'll escape a value lambda, or will go to the top level.
329 -- concat = /\ a -> foldr ..a.. (++) []
330 -- was getting turned into
331 -- concat = /\ a -> lvl a
332 -- lvl = /\ a -> foldr ..a.. (++) []
333 -- which is pretty stupid. Hence the strict_ctxt test
337 %************************************************************************
339 \subsection{Bindings}
341 %************************************************************************
343 The binding stuff works for top level too.
346 lvlBind :: TopLevelFlag -- Used solely to decide whether to clone
347 -> Level -- Context level; might be Top even for bindings nested in the RHS
348 -- of a top level binding
351 -> LvlM (LevelledBind, LevelEnv)
353 lvlBind top_lvl ctxt_lvl env (AnnNonRec bndr rhs@(rhs_fvs,_))
355 = -- No type abstraction; clone existing binder
356 lvlExpr dest_lvl env rhs `thenLvl` \ rhs' ->
357 cloneVar top_lvl env bndr ctxt_lvl dest_lvl `thenLvl` \ (env', bndr') ->
358 returnLvl (NonRec (bndr', dest_lvl) rhs', env')
361 = -- Yes, type abstraction; create a new binder, extend substitution, etc
362 lvlFloatRhs abs_vars dest_lvl env rhs `thenLvl` \ rhs' ->
363 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (env', [bndr']) ->
364 returnLvl (NonRec (bndr', dest_lvl) rhs', env')
367 bind_fvs = rhs_fvs `unionVarSet` idFreeVars bndr
368 abs_vars = abstractVars dest_lvl env bind_fvs
370 dest_lvl | isUnLiftedType (idType bndr) = destLevel env bind_fvs False `maxLvl` Level 1 0
371 | otherwise = destLevel env bind_fvs (isFunction rhs)
372 -- Hack alert! We do have some unlifted bindings, for cheap primops, and
373 -- it is ok to float them out; but not to the top level. If they would otherwise
374 -- go to the top level, we pin them inside the topmost lambda
379 lvlBind top_lvl ctxt_lvl env (AnnRec pairs)
381 = cloneVars top_lvl env bndrs ctxt_lvl dest_lvl `thenLvl` \ (new_env, new_bndrs) ->
382 mapLvl (lvlExpr ctxt_lvl new_env) rhss `thenLvl` \ new_rhss ->
383 returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env)
385 | isSingleton pairs && count isId abs_vars > 1
386 = -- Special case for self recursion where there are
387 -- several variables carried around: build a local loop:
388 -- poly_f = \abs_vars. \lam_vars . letrec f = \lam_vars. rhs in f lam_vars
389 -- This just makes the closures a bit smaller. If we don't do
390 -- this, allocation rises significantly on some programs
392 -- We could elaborate it for the case where there are several
393 -- mutually functions, but it's quite a bit more complicated
395 -- This all seems a bit ad hoc -- sigh
397 (bndr,rhs) = head pairs
398 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
399 rhs_env = extendLvlEnv env abs_vars_w_lvls
401 cloneVar NotTopLevel rhs_env bndr rhs_lvl rhs_lvl `thenLvl` \ (rhs_env', new_bndr) ->
403 (lam_bndrs, rhs_body) = collect_binders rhs
404 (body_lvl, new_lam_bndrs) = lvlLamBndrs rhs_lvl lam_bndrs
405 body_env = extendLvlEnv rhs_env' new_lam_bndrs
407 lvlExpr body_lvl body_env rhs_body `thenLvl` \ new_rhs_body ->
408 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (poly_env, [poly_bndr]) ->
409 returnLvl (Rec [((poly_bndr,dest_lvl), mkLams abs_vars_w_lvls $
410 glue_binders new_lam_bndrs rhs $
411 Let (Rec [((new_bndr,rhs_lvl), mkLams new_lam_bndrs new_rhs_body)])
412 (mkVarApps (Var new_bndr) lam_bndrs))],
416 = newPolyBndrs dest_lvl env abs_vars bndrs `thenLvl` \ (new_env, new_bndrs) ->
417 mapLvl (lvlFloatRhs abs_vars dest_lvl new_env) rhss `thenLvl` \ new_rhss ->
418 returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env)
421 (bndrs,rhss) = unzip pairs
423 -- Finding the free vars of the binding group is annoying
424 bind_fvs = (unionVarSets [ idFreeVars bndr `unionVarSet` rhs_fvs
425 | (bndr, (rhs_fvs,_)) <- pairs])
429 dest_lvl = destLevel env bind_fvs (all isFunction rhss)
430 abs_vars = abstractVars dest_lvl env bind_fvs
432 ----------------------------------------------------
433 -- Three help functons for the type-abstraction case
435 lvlFloatRhs abs_vars dest_lvl env rhs
436 = lvlExpr rhs_lvl rhs_env rhs `thenLvl` \ rhs' ->
437 returnLvl (mkLams abs_vars_w_lvls rhs')
439 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
440 rhs_env = extendLvlEnv env abs_vars_w_lvls
444 %************************************************************************
446 \subsection{Deciding floatability}
448 %************************************************************************
451 lvlLamBndrs :: Level -> [CoreBndr] -> (Level, [(CoreBndr, Level)])
452 -- Compute the levels for the binders of a lambda group
453 -- The binders returned are exactly the same as the ones passed,
454 -- but they are now paired with a level
458 lvlLamBndrs lvl bndrs
459 = go (incMinorLvl lvl)
460 False -- Havn't bumped major level in this group
463 go old_lvl bumped_major rev_lvld_bndrs (bndr:bndrs)
464 | isId bndr && -- Go to the next major level if this is a value binder,
465 not bumped_major && -- and we havn't already gone to the next level (one jump per group)
466 not (isOneShotLambda bndr) -- and it isn't a one-shot lambda
467 = go new_lvl True ((bndr,new_lvl) : rev_lvld_bndrs) bndrs
470 = go old_lvl bumped_major ((bndr,old_lvl) : rev_lvld_bndrs) bndrs
473 new_lvl = incMajorLvl old_lvl
475 go old_lvl _ rev_lvld_bndrs []
476 = (old_lvl, reverse rev_lvld_bndrs)
477 -- a lambda like this (\x -> coerce t (\s -> ...))
478 -- This happens quite a bit in state-transformer programs
482 abstractVars :: Level -> LevelEnv -> VarSet -> [Var]
483 -- Find the variables in fvs, free vars of the target expresion,
484 -- whose level is less than than the supplied level
485 -- These are the ones we are going to abstract out
486 abstractVars dest_lvl env fvs
487 = uniq (sortLt lt [var | fv <- varSetElems fvs, var <- absVarsOf dest_lvl env fv])
489 -- Sort the variables so we don't get
490 -- mixed-up tyvars and Ids; it's just messy
491 v1 `lt` v2 = case (isId v1, isId v2) of
492 (True, False) -> False
493 (False, True) -> True
494 other -> v1 < v2 -- Same family
495 uniq :: [Var] -> [Var]
496 -- Remove adjacent duplicates; the sort will have brought them together
497 uniq (v1:v2:vs) | v1 == v2 = uniq (v2:vs)
498 | otherwise = v1 : uniq (v2:vs)
501 -- Destintion level is the max Id level of the expression
502 -- (We'll abstract the type variables, if any.)
503 destLevel :: LevelEnv -> VarSet -> Bool -> Level
504 destLevel env fvs is_function
506 && is_function = tOP_LEVEL -- Send functions to top level; see
507 -- the comments with isFunction
508 | otherwise = maxIdLevel env fvs
510 isFunction :: CoreExprWithFVs -> Bool
511 -- The idea here is that we want to float *functions* to
512 -- the top level. This saves no work, but
513 -- (a) it can make the host function body a lot smaller,
514 -- and hence inlinable.
515 -- (b) it can also save allocation when the function is recursive:
516 -- h = \x -> letrec f = \y -> ...f...y...x...
519 -- f = \x y -> ...(f x)...y...x...
521 -- No allocation for f now.
522 -- We may only want to do this if there are sufficiently few free
523 -- variables. We certainly only want to do it for values, and not for
524 -- constructors. So the simple thing is just to look for lambdas
525 isFunction (_, AnnLam b e) | isId b = True
526 | otherwise = isFunction e
527 isFunction (_, AnnNote n e) = isFunction e
528 isFunction other = False
532 %************************************************************************
534 \subsection{Free-To-Level Monad}
536 %************************************************************************
539 type LevelEnv = (Bool, -- True <=> Float lambdas too
540 VarEnv Level, -- Domain is *post-cloned* TyVars and Ids
541 Subst, -- Domain is pre-cloned Ids; tracks the in-scope set
542 -- so that subtitution is capture-avoiding
543 IdEnv ([Var], LevelledExpr)) -- Domain is pre-cloned Ids
544 -- We clone let-bound variables so that they are still
545 -- distinct when floated out; hence the SubstEnv/IdEnv.
546 -- (see point 3 of the module overview comment).
547 -- We also use these envs when making a variable polymorphic
548 -- because we want to float it out past a big lambda.
550 -- The SubstEnv and IdEnv always implement the same mapping, but the
551 -- SubstEnv maps to CoreExpr and the IdEnv to LevelledExpr
552 -- Since the range is always a variable or type application,
553 -- there is never any difference between the two, but sadly
554 -- the types differ. The SubstEnv is used when substituting in
555 -- a variable's IdInfo; the IdEnv when we find a Var.
557 -- In addition the IdEnv records a list of tyvars free in the
558 -- type application, just so we don't have to call freeVars on
559 -- the type application repeatedly.
561 -- The domain of the both envs is *pre-cloned* Ids, though
563 -- The domain of the VarEnv Level is the *post-cloned* Ids
565 initialEnv :: Bool -> LevelEnv
566 initialEnv float_lams = (float_lams, emptyVarEnv, emptySubst, emptyVarEnv)
568 floatLams :: LevelEnv -> Bool
569 floatLams (float_lams, _, _, _) = float_lams
571 extendLvlEnv :: LevelEnv -> [(Var,Level)] -> LevelEnv
572 -- Used when *not* cloning
573 extendLvlEnv (float_lams, lvl_env, subst, id_env) prs
575 foldl add_lvl lvl_env prs,
576 foldl del_subst subst prs,
577 foldl del_id id_env prs)
579 add_lvl env (v,l) = extendVarEnv env v l
580 del_subst env (v,_) = extendInScope env v
581 del_id env (v,_) = delVarEnv env v
582 -- We must remove any clone for this variable name in case of
583 -- shadowing. This bit me in the following case
584 -- (in nofib/real/gg/Spark.hs):
587 -- ... -> case e of wild {
588 -- ... -> ... wild ...
592 -- The inside occurrence of @wild@ was being replaced with @ds@,
593 -- incorrectly, because the SubstEnv was still lying around. Ouch!
596 -- extendCaseBndrLvlEnv adds the mapping case-bndr->scrut-var if it can
597 -- (see point 4 of the module overview comment)
598 extendCaseBndrLvlEnv env scrut case_bndr lvl
600 Var v -> extendCloneLvlEnv lvl env [(case_bndr, v)]
601 other -> extendLvlEnv env [(case_bndr,lvl)]
603 extendPolyLvlEnv dest_lvl (float_lams, lvl_env, subst, id_env) abs_vars bndr_pairs
605 foldl add_lvl lvl_env bndr_pairs,
606 foldl add_subst subst bndr_pairs,
607 foldl add_id id_env bndr_pairs)
609 add_lvl env (v,v') = extendVarEnv env v' dest_lvl
610 add_subst env (v,v') = extendSubst env v (DoneEx (mkVarApps (Var v') abs_vars))
611 add_id env (v,v') = extendVarEnv env v ((v':abs_vars), mkVarApps (Var v') abs_vars)
613 extendCloneLvlEnv lvl (float_lams, lvl_env, subst, id_env) bndr_pairs
615 foldl add_lvl lvl_env bndr_pairs,
616 foldl add_subst subst bndr_pairs,
617 foldl add_id id_env bndr_pairs)
619 add_lvl env (v,v') = extendVarEnv env v' lvl
620 add_subst env (v,v') = extendSubst env v (DoneEx (Var v'))
621 add_id env (v,v') = extendVarEnv env v ([v'], Var v')
624 maxIdLevel :: LevelEnv -> VarSet -> Level
625 maxIdLevel (_, lvl_env,_,id_env) var_set
626 = foldVarSet max_in tOP_LEVEL var_set
628 max_in in_var lvl = foldr max_out lvl (case lookupVarEnv id_env in_var of
629 Just (abs_vars, _) -> abs_vars
633 | isId out_var = case lookupVarEnv lvl_env out_var of
634 Just lvl' -> maxLvl lvl' lvl
636 | otherwise = lvl -- Ignore tyvars in *maxIdLevel*
638 lookupVar :: LevelEnv -> Id -> LevelledExpr
639 lookupVar (_, _, _, id_env) v = case lookupVarEnv id_env v of
640 Just (_, expr) -> expr
643 absVarsOf :: Level -> LevelEnv -> Var -> [Var]
644 -- If f is free in the exression, and f maps to poly_f a b c in the
645 -- current substitution, then we must report a b c as candidate type
647 absVarsOf dest_lvl (_, lvl_env, _, id_env) v
649 = [final_av | av <- lookup_avs v, abstract_me av, final_av <- add_tyvars av]
652 = if abstract_me v then [v] else []
655 abstract_me v = case lookupVarEnv lvl_env v of
656 Just lvl -> dest_lvl `ltLvl` lvl
659 lookup_avs v = case lookupVarEnv id_env v of
660 Just (abs_vars, _) -> abs_vars
663 -- We are going to lambda-abstract, so nuke any IdInfo,
664 -- and add the tyvars of the Id
665 add_tyvars v | isId v = zap v : varSetElems (idFreeTyVars v)
668 zap v = WARN( workerExists (idWorkerInfo v)
669 || not (isEmptyCoreRules (idSpecialisation v)),
670 text "absVarsOf: discarding info on" <+> ppr v )
671 setIdInfo v vanillaIdInfo
675 type LvlM result = UniqSM result
684 newPolyBndrs dest_lvl env abs_vars bndrs
685 = getUniquesUs (length bndrs) `thenLvl` \ uniqs ->
687 new_bndrs = zipWith mk_poly_bndr bndrs uniqs
689 returnLvl (extendPolyLvlEnv dest_lvl env abs_vars (bndrs `zip` new_bndrs), new_bndrs)
691 mk_poly_bndr bndr uniq = mkSysLocal (_PK_ str) uniq poly_ty
693 str = "poly_" ++ occNameUserString (getOccName bndr)
694 poly_ty = foldr mkPiType (idType bndr) abs_vars
698 -> [CoreBndr] -> Type -- Abstract wrt these bndrs
700 newLvlVar str vars body_ty
701 = getUniqueUs `thenLvl` \ uniq ->
702 returnUs (mkSysLocal (_PK_ str) uniq (foldr mkPiType body_ty vars))
704 -- The deeply tiresome thing is that we have to apply the substitution
705 -- to the rules inside each Id. Grr. But it matters.
707 cloneVar :: TopLevelFlag -> LevelEnv -> Id -> Level -> Level -> LvlM (LevelEnv, Id)
708 cloneVar TopLevel env v ctxt_lvl dest_lvl
709 = returnUs (env, v) -- Don't clone top level things
710 cloneVar NotTopLevel env v ctxt_lvl dest_lvl
712 getUniqueUs `thenLvl` \ uniq ->
714 v' = setVarUnique v uniq
715 v'' = subst_id_info env ctxt_lvl dest_lvl v'
716 env' = extendCloneLvlEnv dest_lvl env [(v,v'')]
720 cloneVars :: TopLevelFlag -> LevelEnv -> [Id] -> Level -> Level -> LvlM (LevelEnv, [Id])
721 cloneVars TopLevel env vs ctxt_lvl dest_lvl
722 = returnUs (env, vs) -- Don't clone top level things
723 cloneVars NotTopLevel env vs ctxt_lvl dest_lvl
724 = ASSERT( all isId vs )
725 getUniquesUs (length vs) `thenLvl` \ uniqs ->
727 vs' = zipWith setVarUnique vs uniqs
728 vs'' = map (subst_id_info env' ctxt_lvl dest_lvl) vs'
729 env' = extendCloneLvlEnv dest_lvl env (vs `zip` vs'')
731 returnUs (env', vs'')
733 subst_id_info (_, _, subst, _) ctxt_lvl dest_lvl v
734 = modifyIdInfo (\info -> substIdInfo subst info (zap_dmd info)) v
736 -- VERY IMPORTANT: we must zap the demand info
737 -- if the thing is going to float out past a lambda
739 | stays_put || not (isStrict (demandInfo info)) = info
740 | otherwise = setDemandInfo info wwLazy
742 stays_put = ctxt_lvl == dest_lvl