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, 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 LevelledBind = TaggedBind Level
116 tOP_LEVEL = Level 0 0
118 incMajorLvl :: Level -> Level
119 incMajorLvl (Level major minor) = Level (major+1) 0
121 incMinorLvl :: Level -> Level
122 incMinorLvl (Level major minor) = Level major (minor+1)
124 maxLvl :: Level -> Level -> Level
125 maxLvl l1@(Level maj1 min1) l2@(Level maj2 min2)
126 | (maj1 > maj2) || (maj1 == maj2 && min1 > min2) = l1
129 ltLvl :: Level -> Level -> Bool
130 ltLvl (Level maj1 min1) (Level maj2 min2)
131 = (maj1 < maj2) || (maj1 == maj2 && min1 < min2)
133 ltMajLvl :: Level -> Level -> Bool
134 -- Tells if one level belongs to a difft *lambda* level to another
135 ltMajLvl (Level maj1 _) (Level maj2 _) = maj1 < maj2
137 isTopLvl :: Level -> Bool
138 isTopLvl (Level 0 0) = True
139 isTopLvl other = False
141 instance Outputable Level where
142 ppr (Level maj min) = hcat [ char '<', int maj, char ',', int min, char '>' ]
144 instance Eq Level where
145 (Level maj1 min1) == (Level maj2 min2) = maj1==maj2 && min1==min2
148 %************************************************************************
150 \subsection{Main level-setting code}
152 %************************************************************************
155 setLevels :: Bool -- True <=> float lambdas to top level
160 setLevels float_lams binds us
161 = initLvl us (do_them binds)
163 -- "do_them"'s main business is to thread the monad along
164 -- It gives each top binding the same empty envt, because
165 -- things unbound in the envt have level number zero implicitly
166 do_them :: [CoreBind] -> LvlM [LevelledBind]
168 do_them [] = returnLvl []
170 = lvlTopBind init_env b `thenLvl` \ (lvld_bind, _) ->
171 do_them bs `thenLvl` \ lvld_binds ->
172 returnLvl (lvld_bind : lvld_binds)
174 init_env = initialEnv float_lams
176 lvlTopBind env (NonRec binder rhs)
177 = lvlBind TopLevel tOP_LEVEL env (AnnNonRec binder (freeVars rhs))
178 -- Rhs can have no free vars!
180 lvlTopBind env (Rec pairs)
181 = lvlBind TopLevel tOP_LEVEL env (AnnRec [(b,freeVars rhs) | (b,rhs) <- pairs])
184 %************************************************************************
186 \subsection{Setting expression levels}
188 %************************************************************************
191 lvlExpr :: Level -- ctxt_lvl: Level of enclosing expression
192 -> LevelEnv -- Level of in-scope names/tyvars
193 -> CoreExprWithFVs -- input expression
194 -> LvlM LevelledExpr -- Result expression
197 The @ctxt_lvl@ is, roughly, the level of the innermost enclosing
198 binder. Here's an example
200 v = \x -> ...\y -> let r = case (..x..) of
204 When looking at the rhs of @r@, @ctxt_lvl@ will be 1 because that's
205 the level of @r@, even though it's inside a level-2 @\y@. It's
206 important that @ctxt_lvl@ is 1 and not 2 in @r@'s rhs, because we
207 don't want @lvlExpr@ to turn the scrutinee of the @case@ into an MFE
208 --- because it isn't a *maximal* free expression.
210 If there were another lambda in @r@'s rhs, it would get level-2 as well.
213 lvlExpr _ _ (_, AnnType ty) = returnLvl (Type ty)
214 lvlExpr _ env (_, AnnVar v) = returnLvl (lookupVar env v)
215 lvlExpr _ env (_, AnnLit lit) = returnLvl (Lit lit)
217 lvlExpr ctxt_lvl env (_, AnnApp fun arg)
218 = lvl_fun fun `thenLvl` \ fun' ->
219 lvlMFE False ctxt_lvl env arg `thenLvl` \ arg' ->
220 returnLvl (App fun' arg')
222 lvl_fun (_, AnnCase _ _ _) = lvlMFE True ctxt_lvl env fun
223 lvl_fun other = lvlExpr ctxt_lvl env fun
224 -- We don't do MFE on partial applications generally,
225 -- but we do if the function is big and hairy, like a case
227 lvlExpr ctxt_lvl env (_, AnnNote InlineMe expr)
228 -- Don't float anything out of an InlineMe; hence the tOP_LEVEL
229 = lvlExpr tOP_LEVEL env expr `thenLvl` \ expr' ->
230 returnLvl (Note InlineMe expr')
232 lvlExpr ctxt_lvl env (_, AnnNote note expr)
233 = lvlExpr ctxt_lvl env expr `thenLvl` \ expr' ->
234 returnLvl (Note note expr')
236 -- We don't split adjacent lambdas. That is, given
238 -- we don't float to give
239 -- \x -> let v = x+y in \y -> (v,y)
240 -- Why not? Because partial applications are fairly rare, and splitting
241 -- lambdas makes them more expensive.
243 lvlExpr ctxt_lvl env expr@(_, AnnLam bndr rhs)
244 = lvlMFE True new_lvl new_env body `thenLvl` \ new_body ->
245 returnLvl (glue_binders new_bndrs expr new_body)
247 (bndrs, body) = collect_binders expr
248 (new_lvl, new_bndrs) = lvlLamBndrs ctxt_lvl bndrs
249 new_env = extendLvlEnv env new_bndrs
251 lvlExpr ctxt_lvl env (_, AnnLet bind body)
252 = lvlBind NotTopLevel ctxt_lvl env bind `thenLvl` \ (bind', new_env) ->
253 lvlExpr ctxt_lvl new_env body `thenLvl` \ body' ->
254 returnLvl (Let bind' body')
256 lvlExpr ctxt_lvl env (_, AnnCase expr case_bndr alts)
257 = lvlMFE True ctxt_lvl env expr `thenLvl` \ expr' ->
259 alts_env = extendCaseBndrLvlEnv env expr' case_bndr incd_lvl
261 mapLvl (lvl_alt alts_env) alts `thenLvl` \ alts' ->
262 returnLvl (Case expr' (case_bndr, incd_lvl) alts')
264 incd_lvl = incMinorLvl ctxt_lvl
266 lvl_alt alts_env (con, bs, rhs)
267 = lvlMFE True incd_lvl new_env rhs `thenLvl` \ rhs' ->
268 returnLvl (con, bs', rhs')
270 bs' = [ (b, incd_lvl) | b <- bs ]
271 new_env = extendLvlEnv alts_env bs'
276 go rev_bndrs (_, AnnLam b e) = go (b:rev_bndrs) e
277 go rev_bndrs (_, AnnNote n e) = go rev_bndrs e
278 go rev_bndrs rhs = (reverse rev_bndrs, rhs)
279 -- Ignore notes, because we don't want to split
280 -- a lambda like this (\x -> coerce t (\s -> ...))
281 -- This happens quite a bit in state-transformer programs
283 -- glue_binders puts the lambda back together
284 glue_binders (b:bs) (_, AnnLam _ e) body = Lam b (glue_binders bs e body)
285 glue_binders bs (_, AnnNote n e) body = Note n (glue_binders bs e body)
286 glue_binders [] e body = body
289 @lvlMFE@ is just like @lvlExpr@, except that it might let-bind
290 the expression, so that it can itself be floated.
293 lvlMFE :: Bool -- True <=> strict context [body of case or let]
294 -> Level -- Level of innermost enclosing lambda/tylam
295 -> LevelEnv -- Level of in-scope names/tyvars
296 -> CoreExprWithFVs -- input expression
297 -> LvlM LevelledExpr -- Result expression
299 lvlMFE strict_ctxt ctxt_lvl env (_, AnnType ty)
300 = returnLvl (Type ty)
302 lvlMFE strict_ctxt ctxt_lvl env ann_expr@(fvs, _)
303 | isUnLiftedType ty -- Can't let-bind it
304 || not good_destination
305 || exprIsTrivial expr -- Is trivial
306 || (strict_ctxt && exprIsBottom expr) -- Strict context and is bottom
307 -- e.g. \x -> error "foo"
308 -- No gain from floating this
309 = -- Don't float it out
310 lvlExpr ctxt_lvl env ann_expr
312 | otherwise -- Float it out!
313 = lvlFloatRhs abs_vars dest_lvl env ann_expr `thenLvl` \ expr' ->
314 newLvlVar "lvl" abs_vars ty `thenLvl` \ var ->
315 returnLvl (Let (NonRec (var,dest_lvl) expr')
316 (mkVarApps (Var var) abs_vars))
318 expr = deAnnotate ann_expr
320 dest_lvl = destLevel env fvs (isFunction ann_expr)
321 abs_vars = abstractVars dest_lvl env fvs
323 good_destination = dest_lvl `ltMajLvl` ctxt_lvl -- Escapes a value lambda
324 || (isTopLvl dest_lvl && not strict_ctxt) -- Goes to the top
325 -- A decision to float entails let-binding this thing, and we only do
326 -- that if we'll escape a value lambda, or will go to the top level.
328 -- concat = /\ a -> foldr ..a.. (++) []
329 -- was getting turned into
330 -- concat = /\ a -> lvl a
331 -- lvl = /\ a -> foldr ..a.. (++) []
332 -- which is pretty stupid. Hence the strict_ctxt test
336 %************************************************************************
338 \subsection{Bindings}
340 %************************************************************************
342 The binding stuff works for top level too.
345 lvlBind :: TopLevelFlag -- Used solely to decide whether to clone
346 -> Level -- Context level; might be Top even for bindings nested in the RHS
347 -- of a top level binding
350 -> LvlM (LevelledBind, LevelEnv)
352 lvlBind top_lvl ctxt_lvl env (AnnNonRec bndr rhs@(rhs_fvs,_))
354 = -- No type abstraction; clone existing binder
355 lvlExpr dest_lvl env rhs `thenLvl` \ rhs' ->
356 cloneVar top_lvl env bndr ctxt_lvl dest_lvl `thenLvl` \ (env', bndr') ->
357 returnLvl (NonRec (bndr', dest_lvl) rhs', env')
360 = -- Yes, type abstraction; create a new binder, extend substitution, etc
361 lvlFloatRhs abs_vars dest_lvl env rhs `thenLvl` \ rhs' ->
362 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (env', [bndr']) ->
363 returnLvl (NonRec (bndr', dest_lvl) rhs', env')
366 bind_fvs = rhs_fvs `unionVarSet` idFreeVars bndr
367 abs_vars = abstractVars dest_lvl env bind_fvs
369 dest_lvl | isUnLiftedType (idType bndr) = destLevel env bind_fvs False `maxLvl` Level 1 0
370 | otherwise = destLevel env bind_fvs (isFunction rhs)
371 -- Hack alert! We do have some unlifted bindings, for cheap primops, and
372 -- it is ok to float them out; but not to the top level. If they would otherwise
373 -- go to the top level, we pin them inside the topmost lambda
378 lvlBind top_lvl ctxt_lvl env (AnnRec pairs)
380 = cloneVars top_lvl env bndrs ctxt_lvl dest_lvl `thenLvl` \ (new_env, new_bndrs) ->
381 mapLvl (lvlExpr ctxt_lvl new_env) rhss `thenLvl` \ new_rhss ->
382 returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env)
384 | isSingleton pairs && count isId abs_vars > 1
385 = -- Special case for self recursion where there are
386 -- several variables carried around: build a local loop:
387 -- poly_f = \abs_vars. \lam_vars . letrec f = \lam_vars. rhs in f lam_vars
388 -- This just makes the closures a bit smaller. If we don't do
389 -- this, allocation rises significantly on some programs
391 -- We could elaborate it for the case where there are several
392 -- mutually functions, but it's quite a bit more complicated
394 -- This all seems a bit ad hoc -- sigh
396 (bndr,rhs) = head pairs
397 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
398 rhs_env = extendLvlEnv env abs_vars_w_lvls
400 cloneVar NotTopLevel rhs_env bndr rhs_lvl rhs_lvl `thenLvl` \ (rhs_env', new_bndr) ->
402 (lam_bndrs, rhs_body) = collect_binders rhs
403 (body_lvl, new_lam_bndrs) = lvlLamBndrs rhs_lvl lam_bndrs
404 body_env = extendLvlEnv rhs_env' new_lam_bndrs
406 lvlExpr body_lvl body_env rhs_body `thenLvl` \ new_rhs_body ->
407 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (poly_env, [poly_bndr]) ->
408 returnLvl (Rec [((poly_bndr,dest_lvl), mkLams abs_vars_w_lvls $
409 glue_binders new_lam_bndrs rhs $
410 Let (Rec [((new_bndr,rhs_lvl), mkLams new_lam_bndrs new_rhs_body)])
411 (mkVarApps (Var new_bndr) lam_bndrs))],
415 = newPolyBndrs dest_lvl env abs_vars bndrs `thenLvl` \ (new_env, new_bndrs) ->
416 mapLvl (lvlFloatRhs abs_vars dest_lvl new_env) rhss `thenLvl` \ new_rhss ->
417 returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env)
420 (bndrs,rhss) = unzip pairs
422 -- Finding the free vars of the binding group is annoying
423 bind_fvs = (unionVarSets [ idFreeVars bndr `unionVarSet` rhs_fvs
424 | (bndr, (rhs_fvs,_)) <- pairs])
428 dest_lvl = destLevel env bind_fvs (all isFunction rhss)
429 abs_vars = abstractVars dest_lvl env bind_fvs
431 ----------------------------------------------------
432 -- Three help functons for the type-abstraction case
434 lvlFloatRhs abs_vars dest_lvl env rhs
435 = lvlExpr rhs_lvl rhs_env rhs `thenLvl` \ rhs' ->
436 returnLvl (mkLams abs_vars_w_lvls rhs')
438 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
439 rhs_env = extendLvlEnv env abs_vars_w_lvls
443 %************************************************************************
445 \subsection{Deciding floatability}
447 %************************************************************************
450 lvlLamBndrs :: Level -> [CoreBndr] -> (Level, [(CoreBndr, Level)])
451 -- Compute the levels for the binders of a lambda group
452 -- The binders returned are exactly the same as the ones passed,
453 -- but they are now paired with a level
457 lvlLamBndrs lvl bndrs
458 = go (incMinorLvl lvl)
459 False -- Havn't bumped major level in this group
462 go old_lvl bumped_major rev_lvld_bndrs (bndr:bndrs)
463 | isId bndr && -- Go to the next major level if this is a value binder,
464 not bumped_major && -- and we havn't already gone to the next level (one jump per group)
465 not (isOneShotLambda bndr) -- and it isn't a one-shot lambda
466 = go new_lvl True ((bndr,new_lvl) : rev_lvld_bndrs) bndrs
469 = go old_lvl bumped_major ((bndr,old_lvl) : rev_lvld_bndrs) bndrs
472 new_lvl = incMajorLvl old_lvl
474 go old_lvl _ rev_lvld_bndrs []
475 = (old_lvl, reverse rev_lvld_bndrs)
476 -- a lambda like this (\x -> coerce t (\s -> ...))
477 -- This happens quite a bit in state-transformer programs
481 abstractVars :: Level -> LevelEnv -> VarSet -> [Var]
482 -- Find the variables in fvs, free vars of the target expresion,
483 -- whose level is less than than the supplied level
484 -- These are the ones we are going to abstract out
485 abstractVars dest_lvl env fvs
486 = uniq (sortLt lt [var | fv <- varSetElems fvs, var <- absVarsOf dest_lvl env fv])
488 -- Sort the variables so we don't get
489 -- mixed-up tyvars and Ids; it's just messy
490 v1 `lt` v2 = case (isId v1, isId v2) of
491 (True, False) -> False
492 (False, True) -> True
493 other -> v1 < v2 -- Same family
494 uniq :: [Var] -> [Var]
495 -- Remove adjacent duplicates; the sort will have brought them together
496 uniq (v1:v2:vs) | v1 == v2 = uniq (v2:vs)
497 | otherwise = v1 : uniq (v2:vs)
500 -- Destintion level is the max Id level of the expression
501 -- (We'll abstract the type variables, if any.)
502 destLevel :: LevelEnv -> VarSet -> Bool -> Level
503 destLevel env fvs is_function
505 && is_function = tOP_LEVEL -- Send functions to top level; see
506 -- the comments with isFunction
507 | otherwise = maxIdLevel env fvs
509 isFunction :: CoreExprWithFVs -> Bool
510 -- The idea here is that we want to float *functions* to
511 -- the top level. This saves no work, but
512 -- (a) it can make the host function body a lot smaller,
513 -- and hence inlinable.
514 -- (b) it can also save allocation when the function is recursive:
515 -- h = \x -> letrec f = \y -> ...f...y...x...
518 -- f = \x y -> ...(f x)...y...x...
520 -- No allocation for f now.
521 -- We may only want to do this if there are sufficiently few free
522 -- variables. We certainly only want to do it for values, and not for
523 -- constructors. So the simple thing is just to look for lambdas
524 isFunction (_, AnnLam b e) | isId b = True
525 | otherwise = isFunction e
526 isFunction (_, AnnNote n e) = isFunction e
527 isFunction other = False
531 %************************************************************************
533 \subsection{Free-To-Level Monad}
535 %************************************************************************
538 type LevelEnv = (Bool, -- True <=> Float lambdas too
539 VarEnv Level, -- Domain is *post-cloned* TyVars and Ids
540 Subst, -- Domain is pre-cloned Ids; tracks the in-scope set
541 -- so that subtitution is capture-avoiding
542 IdEnv ([Var], LevelledExpr)) -- Domain is pre-cloned Ids
543 -- We clone let-bound variables so that they are still
544 -- distinct when floated out; hence the SubstEnv/IdEnv.
545 -- (see point 3 of the module overview comment).
546 -- We also use these envs when making a variable polymorphic
547 -- because we want to float it out past a big lambda.
549 -- The SubstEnv and IdEnv always implement the same mapping, but the
550 -- SubstEnv maps to CoreExpr and the IdEnv to LevelledExpr
551 -- Since the range is always a variable or type application,
552 -- there is never any difference between the two, but sadly
553 -- the types differ. The SubstEnv is used when substituting in
554 -- a variable's IdInfo; the IdEnv when we find a Var.
556 -- In addition the IdEnv records a list of tyvars free in the
557 -- type application, just so we don't have to call freeVars on
558 -- the type application repeatedly.
560 -- The domain of the both envs is *pre-cloned* Ids, though
562 -- The domain of the VarEnv Level is the *post-cloned* Ids
564 initialEnv :: Bool -> LevelEnv
565 initialEnv float_lams = (float_lams, emptyVarEnv, emptySubst, emptyVarEnv)
567 floatLams :: LevelEnv -> Bool
568 floatLams (float_lams, _, _, _) = float_lams
570 extendLvlEnv :: LevelEnv -> [(Var,Level)] -> LevelEnv
571 -- Used when *not* cloning
572 extendLvlEnv (float_lams, lvl_env, subst, id_env) prs
574 foldl add_lvl lvl_env prs,
575 foldl del_subst subst prs,
576 foldl del_id id_env prs)
578 add_lvl env (v,l) = extendVarEnv env v l
579 del_subst env (v,_) = extendInScope env v
580 del_id env (v,_) = delVarEnv env v
581 -- We must remove any clone for this variable name in case of
582 -- shadowing. This bit me in the following case
583 -- (in nofib/real/gg/Spark.hs):
586 -- ... -> case e of wild {
587 -- ... -> ... wild ...
591 -- The inside occurrence of @wild@ was being replaced with @ds@,
592 -- incorrectly, because the SubstEnv was still lying around. Ouch!
595 -- extendCaseBndrLvlEnv adds the mapping case-bndr->scrut-var if it can
596 -- (see point 4 of the module overview comment)
597 extendCaseBndrLvlEnv env scrut case_bndr lvl
599 Var v -> extendCloneLvlEnv lvl env [(case_bndr, v)]
600 other -> extendLvlEnv env [(case_bndr,lvl)]
602 extendPolyLvlEnv dest_lvl (float_lams, lvl_env, subst, id_env) abs_vars bndr_pairs
604 foldl add_lvl lvl_env bndr_pairs,
605 foldl add_subst subst bndr_pairs,
606 foldl add_id id_env bndr_pairs)
608 add_lvl env (v,v') = extendVarEnv env v' dest_lvl
609 add_subst env (v,v') = extendSubst env v (DoneEx (mkVarApps (Var v') abs_vars))
610 add_id env (v,v') = extendVarEnv env v ((v':abs_vars), mkVarApps (Var v') abs_vars)
612 extendCloneLvlEnv lvl (float_lams, lvl_env, subst, id_env) bndr_pairs
614 foldl add_lvl lvl_env bndr_pairs,
615 foldl add_subst subst bndr_pairs,
616 foldl add_id id_env bndr_pairs)
618 add_lvl env (v,v') = extendVarEnv env v' lvl
619 add_subst env (v,v') = extendSubst env v (DoneEx (Var v'))
620 add_id env (v,v') = extendVarEnv env v ([v'], Var v')
623 maxIdLevel :: LevelEnv -> VarSet -> Level
624 maxIdLevel (_, lvl_env,_,id_env) var_set
625 = foldVarSet max_in tOP_LEVEL var_set
627 max_in in_var lvl = foldr max_out lvl (case lookupVarEnv id_env in_var of
628 Just (abs_vars, _) -> abs_vars
632 | isId out_var = case lookupVarEnv lvl_env out_var of
633 Just lvl' -> maxLvl lvl' lvl
635 | otherwise = lvl -- Ignore tyvars in *maxIdLevel*
637 lookupVar :: LevelEnv -> Id -> LevelledExpr
638 lookupVar (_, _, _, id_env) v = case lookupVarEnv id_env v of
639 Just (_, expr) -> expr
642 absVarsOf :: Level -> LevelEnv -> Var -> [Var]
643 -- If f is free in the exression, and f maps to poly_f a b c in the
644 -- current substitution, then we must report a b c as candidate type
646 absVarsOf dest_lvl (_, lvl_env, _, id_env) v
648 = [final_av | av <- lookup_avs v, abstract_me av, final_av <- add_tyvars av]
651 = if abstract_me v then [v] else []
654 abstract_me v = case lookupVarEnv lvl_env v of
655 Just lvl -> dest_lvl `ltLvl` lvl
658 lookup_avs v = case lookupVarEnv id_env v of
659 Just (abs_vars, _) -> abs_vars
662 -- We are going to lambda-abstract, so nuke any IdInfo,
663 -- and add the tyvars of the Id
664 add_tyvars v | isId v = zap v : varSetElems (idFreeTyVars v)
667 zap v = WARN( workerExists (idWorkerInfo v)
668 || not (isEmptyCoreRules (idSpecialisation v)),
669 text "absVarsOf: discarding info on" <+> ppr v )
670 setIdInfo v vanillaIdInfo
674 type LvlM result = UniqSM result
683 newPolyBndrs dest_lvl env abs_vars bndrs
684 = getUniquesUs (length bndrs) `thenLvl` \ uniqs ->
686 new_bndrs = zipWith mk_poly_bndr bndrs uniqs
688 returnLvl (extendPolyLvlEnv dest_lvl env abs_vars (bndrs `zip` new_bndrs), new_bndrs)
690 mk_poly_bndr bndr uniq = mkSysLocal (_PK_ str) uniq poly_ty
692 str = "poly_" ++ occNameUserString (getOccName bndr)
693 poly_ty = foldr mkPiType (idType bndr) abs_vars
697 -> [CoreBndr] -> Type -- Abstract wrt these bndrs
699 newLvlVar str vars body_ty
700 = getUniqueUs `thenLvl` \ uniq ->
701 returnUs (mkSysLocal (_PK_ str) uniq (foldr mkPiType body_ty vars))
703 -- The deeply tiresome thing is that we have to apply the substitution
704 -- to the rules inside each Id. Grr. But it matters.
706 cloneVar :: TopLevelFlag -> LevelEnv -> Id -> Level -> Level -> LvlM (LevelEnv, Id)
707 cloneVar TopLevel env v ctxt_lvl dest_lvl
708 = returnUs (env, v) -- Don't clone top level things
709 cloneVar NotTopLevel env v ctxt_lvl dest_lvl
711 getUniqueUs `thenLvl` \ uniq ->
713 v' = setVarUnique v uniq
714 v'' = subst_id_info env ctxt_lvl dest_lvl v'
715 env' = extendCloneLvlEnv dest_lvl env [(v,v'')]
719 cloneVars :: TopLevelFlag -> LevelEnv -> [Id] -> Level -> Level -> LvlM (LevelEnv, [Id])
720 cloneVars TopLevel env vs ctxt_lvl dest_lvl
721 = returnUs (env, vs) -- Don't clone top level things
722 cloneVars NotTopLevel env vs ctxt_lvl dest_lvl
723 = ASSERT( all isId vs )
724 getUniquesUs (length vs) `thenLvl` \ uniqs ->
726 vs' = zipWith setVarUnique vs uniqs
727 vs'' = map (subst_id_info env' ctxt_lvl dest_lvl) vs'
728 env' = extendCloneLvlEnv dest_lvl env (vs `zip` vs'')
730 returnUs (env', vs'')
732 subst_id_info (_, _, subst, _) ctxt_lvl dest_lvl v
733 = modifyIdInfo (\info -> substIdInfo subst info (zap_dmd info)) v
735 -- VERY IMPORTANT: we must zap the demand info
736 -- if the thing is going to float out past a lambda
738 | stays_put || not (isStrict (demandInfo info)) = info
739 | otherwise = setDemandInfo info wwLazy
741 stays_put = ctxt_lvl == dest_lvl