2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
6 We attach binding levels to Core bindings, in preparation for floating
9 We also let-ify many applications (notably case scrutinees), so they
10 will have a fighting chance of being floated sensible.
13 #include "HsVersions.h"
20 incMinorLvl, ltMajLvl, ltLvl, isTopLvl
21 -- not exported: , incMajorLvl, isTopMajLvl, unTopify
29 import CoreUtils ( coreExprType, manifestlyWHNF, manifestlyBottom )
30 import FreeVars -- all of it
31 import Id ( idType, mkSysLocal, toplevelishId,
32 nullIdEnv, addOneToIdEnv, growIdEnvList,
33 unionManyIdSets, minusIdSet, mkIdSet,
35 lookupIdEnv, IdEnv(..)
37 import Pretty ( ppStr, ppBesides, ppChar, ppInt )
38 import SrcLoc ( mkUnknownSrcLoc )
39 import Type ( isPrimType, mkTyVarTys )
40 import TyVar ( nullTyVarEnv, addOneToTyVarEnv,
41 growTyVarEnvList, lookupTyVarEnv,
46 import UniqSupply ( thenUs, returnUs, mapUs, mapAndUnzipUs,
47 mapAndUnzip3Us, getUnique, UniqSM(..)
49 import Usage ( UVar(..) )
50 import Util ( mapAccumL, zipWithEqual, panic, assertPanic )
52 quantifyTy = panic "SetLevels.quantifyTy (ToDo)"
53 isLeakFreeType = panic "SetLevels.isLeakFreeType (ToDo)"
56 %************************************************************************
58 \subsection{Level numbers}
60 %************************************************************************
64 = Top -- Means *really* the top level.
65 | Level Int -- Level number of enclosing lambdas
66 Int -- Number of big-lambda and/or case expressions between
67 -- here and the nearest enclosing lambda
70 The {\em level number} on a (type-)lambda-bound variable is the
71 nesting depth of the (type-)lambda which binds it. On an expression,
72 it's the maximum level number of its free (type-)variables. On a
73 let(rec)-bound variable, it's the level of its RHS. On a case-bound
74 variable, it's the number of enclosing lambdas.
76 Top-level variables: level~0. Those bound on the RHS of a top-level
77 definition but ``before'' a lambda; e.g., the \tr{x} in (levels shown
80 a_0 = let b_? = ... in
81 x_1 = ... b ... in ...
84 Level 0 0 will make something get floated to a top-level "equals",
85 @Top@ makes it go right to the top.
87 The main function @lvlExpr@ carries a ``context level'' (@ctxt_lvl@).
88 That's meant to be the level number of the enclosing binder in the
89 final (floated) program. If the level number of a sub-expression is
90 less than that of the context, then it might be worth let-binding the
91 sub-expression so that it will indeed float. This context level starts
92 at @Level 0 0@; it is never @Top@.
95 type LevelledExpr = GenCoreExpr (Id, Level) Id TyVar UVar
96 type LevelledArg = GenCoreArg Id TyVar UVar
97 type LevelledBind = GenCoreBinding (Id, Level) Id TyVar UVar
99 type LevelEnvs = (IdEnv Level, -- bind Ids to levels
100 TyVarEnv Level) -- bind type variables to levels
104 incMajorLvl :: Level -> Level
105 incMajorLvl Top = Level 1 0
106 incMajorLvl (Level major minor) = Level (major+1) 0
108 incMinorLvl :: Level -> Level
109 incMinorLvl Top = Level 0 1
110 incMinorLvl (Level major minor) = Level major (minor+1)
112 maxLvl :: Level -> Level -> Level
115 maxLvl l1@(Level maj1 min1) l2@(Level maj2 min2)
116 | (maj1 > maj2) || (maj1 == maj2 && min1 > min2) = l1
119 ltLvl :: Level -> Level -> Bool
121 ltLvl Top (Level _ _) = True
122 ltLvl (Level maj1 min1) (Level maj2 min2)
123 = (maj1 < maj2) || (maj1 == maj2 && min1 < min2)
125 ltMajLvl :: Level -> Level -> Bool
126 -- Tells if one level belongs to a difft *lambda* level to another
127 ltMajLvl l1 Top = False
128 ltMajLvl Top (Level 0 _) = False
129 ltMajLvl Top (Level _ _) = True
130 ltMajLvl (Level maj1 _) (Level maj2 _) = maj1 < maj2
132 isTopLvl :: Level -> Bool
134 isTopLvl other = False
136 isTopMajLvl :: Level -> Bool -- Tells if it's the top *lambda* level
137 isTopMajLvl Top = True
138 isTopMajLvl (Level maj _) = maj == 0
140 unTopify :: Level -> Level
141 unTopify Top = Level 0 0
144 instance Outputable Level where
145 ppr sty Top = ppStr "<Top>"
146 ppr sty (Level maj min) = ppBesides [ ppChar '<', ppInt maj, ppChar ',', ppInt min, ppChar '>' ]
149 %************************************************************************
151 \subsection{Main level-setting code}
153 %************************************************************************
156 setLevels :: [CoreBinding]
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 :: [CoreBinding] -> LvlM [LevelledBind]
168 do_them [] = returnLvl []
170 = lvlTopBind b `thenLvl` \ (lvld_bind, _) ->
171 do_them bs `thenLvl` \ lvld_binds ->
172 returnLvl (lvld_bind ++ lvld_binds)
174 initial_envs = (nullIdEnv, nullTyVarEnv)
176 lvlTopBind (NonRec binder rhs)
177 = lvlBind (Level 0 0) initial_envs (AnnNonRec binder (freeVars rhs))
178 -- Rhs can have no free vars!
180 lvlTopBind (Rec pairs)
181 = lvlBind (Level 0 0) initial_envs (AnnRec [(b,freeVars rhs) | (b,rhs) <- pairs])
184 %************************************************************************
186 \subsection{Bindings}
188 %************************************************************************
190 The binding stuff works for top level too.
193 type CoreBindingWithFVs = AnnCoreBinding Id Id TyVar UVar FVInfo
197 -> CoreBindingWithFVs
198 -> LvlM ([LevelledBind], LevelEnvs)
200 lvlBind ctxt_lvl envs@(venv, tenv) (AnnNonRec name rhs)
201 = setFloatLevel True {- Already let-bound -}
202 ctxt_lvl envs rhs ty `thenLvl` \ (final_lvl, rhs') ->
204 new_envs = (addOneToIdEnv venv name final_lvl, tenv)
206 returnLvl ([NonRec (name, final_lvl) rhs'], new_envs)
211 lvlBind ctxt_lvl envs@(venv, tenv) (AnnRec pairs)
212 = decideRecFloatLevel ctxt_lvl envs binders rhss
213 `thenLvl` \ (final_lvl, extra_binds, rhss') ->
215 binders_w_lvls = binders `zip` repeat final_lvl
216 new_envs = (growIdEnvList venv binders_w_lvls, tenv)
218 returnLvl (extra_binds ++ [Rec (binders_w_lvls `zip` rhss')], new_envs)
220 (binders,rhss) = unzip pairs
223 %************************************************************************
225 \subsection{Setting expression levels}
227 %************************************************************************
230 lvlExpr :: Level -- ctxt_lvl: Level of enclosing expression
231 -> LevelEnvs -- Level of in-scope names/tyvars
232 -> CoreExprWithFVs -- input expression
233 -> LvlM LevelledExpr -- Result expression
236 The @ctxt_lvl@ is, roughly, the level of the innermost enclosing
241 v = \x -> ...\y -> let r = case (..x..) of
245 When looking at the rhs of @r@, @ctxt_lvl@ will be 1 because that's
246 the level of @r@, even though it's inside a level-2 @\y@. It's
247 important that @ctxt_lvl@ is 1 and not 2 in @r@'s rhs, because we
248 don't want @lvlExpr@ to turn the scrutinee of the @case@ into an MFE
249 --- because it isn't a *maximal* free expression.
251 If there were another lambda in @r@'s rhs, it would get level-2 as well.
254 lvlExpr _ _ (_, AnnVar v) = returnLvl (Var v)
255 lvlExpr _ _ (_, AnnLit l) = returnLvl (Lit l)
256 lvlExpr _ _ (_, AnnCon con args) = returnLvl (Con con args)
257 lvlExpr _ _ (_, AnnPrim op args) = returnLvl (Prim op args)
259 lvlExpr ctxt_lvl envs@(venv, tenv) (_, AnnApp fun arg)
260 = lvlExpr ctxt_lvl envs fun `thenLvl` \ fun' ->
261 returnLvl (App fun' arg)
263 lvlExpr ctxt_lvl envs (_, AnnSCC cc expr)
264 = lvlExpr ctxt_lvl envs expr `thenLvl` \ expr' ->
265 returnLvl (SCC cc expr')
267 lvlExpr ctxt_lvl envs@(venv, tenv) (_, AnnLam (ValBinder arg) rhs)
268 = lvlMFE incd_lvl (new_venv, tenv) rhs `thenLvl` \ rhs' ->
269 returnLvl (Lam (ValBinder (arg,incd_lvl)) rhs')
271 incd_lvl = incMajorLvl ctxt_lvl
272 new_venv = growIdEnvList venv [(arg,incd_lvl)]
274 lvlExpr ctxt_lvl (venv, tenv) (_, AnnLam (TyBinder tyvar) e)
275 = lvlExpr incd_lvl (venv, new_tenv) e `thenLvl` \ e' ->
276 returnLvl (Lam (TyBinder tyvar) e')
278 incd_lvl = incMinorLvl ctxt_lvl
279 new_tenv = addOneToTyVarEnv tenv tyvar incd_lvl
281 lvlExpr ctxt_lvl (venv, tenv) (_, AnnLam (UsageBinder u) e)
282 = panic "SetLevels.lvlExpr:AnnLam UsageBinder"
284 lvlExpr ctxt_lvl envs (_, AnnLet bind body)
285 = lvlBind ctxt_lvl envs bind `thenLvl` \ (binds', new_envs) ->
286 lvlExpr ctxt_lvl new_envs body `thenLvl` \ body' ->
287 returnLvl (foldr Let body' binds') -- mkCoLet* requires Core...
289 lvlExpr ctxt_lvl envs@(venv, tenv) (_, AnnCase expr alts)
290 = lvlMFE ctxt_lvl envs expr `thenLvl` \ expr' ->
291 lvl_alts alts `thenLvl` \ alts' ->
292 returnLvl (Case expr' alts')
294 expr_type = coreExprType (deAnnotate expr)
295 incd_lvl = incMinorLvl ctxt_lvl
297 lvl_alts (AnnAlgAlts alts deflt)
298 = mapLvl lvl_alt alts `thenLvl` \ alts' ->
299 lvl_deflt deflt `thenLvl` \ deflt' ->
300 returnLvl (AlgAlts alts' deflt')
304 bs' = [ (b, incd_lvl) | b <- bs ]
305 new_envs = (growIdEnvList venv bs', tenv)
307 lvlMFE incd_lvl new_envs e `thenLvl` \ e' ->
308 returnLvl (con, bs', e')
310 lvl_alts (AnnPrimAlts alts deflt)
311 = mapLvl lvl_alt alts `thenLvl` \ alts' ->
312 lvl_deflt deflt `thenLvl` \ deflt' ->
313 returnLvl (PrimAlts alts' deflt')
316 = lvlMFE incd_lvl envs e `thenLvl` \ e' ->
319 lvl_deflt AnnNoDefault = returnLvl NoDefault
321 lvl_deflt (AnnBindDefault b expr)
323 new_envs = (addOneToIdEnv venv b incd_lvl, tenv)
325 lvlMFE incd_lvl new_envs expr `thenLvl` \ expr' ->
326 returnLvl (BindDefault (b, incd_lvl) expr')
329 @lvlMFE@ is just like @lvlExpr@, except that it might let-bind
330 the expression, so that it can itself be floated.
333 lvlMFE :: Level -- Level of innermost enclosing lambda/tylam
334 -> LevelEnvs -- Level of in-scope names/tyvars
335 -> CoreExprWithFVs -- input expression
336 -> LvlM LevelledExpr -- Result expression
338 lvlMFE ctxt_lvl envs@(venv,_) ann_expr
339 | isPrimType ty -- Can't let-bind it
340 = lvlExpr ctxt_lvl envs ann_expr
342 | otherwise -- Not primitive type so could be let-bound
343 = setFloatLevel False {- Not already let-bound -}
344 ctxt_lvl envs ann_expr ty `thenLvl` \ (final_lvl, expr') ->
347 ty = coreExprType (deAnnotate ann_expr)
351 %************************************************************************
353 \subsection{Deciding floatability}
355 %************************************************************************
357 @setFloatLevel@ is used for let-bound right-hand-sides, or for MFEs which
358 are being created as let-bindings
362 YES. -> (a) try abstracting type variables.
363 If we abstract type variables it will go further, that is, past more
364 lambdas. same as asking if the level number given by the free
365 variables is less than the level number given by free variables
366 and type variables together.
367 Abstract offending type variables, e.g.
369 to let v = /\ty' -> f ty' a b
371 so that v' is not stopped by the level number of ty
372 tag the original let with its level number
373 (from its variables and type variables)
375 YES. -> No point in let binding to float a WHNF.
376 Pin (leave) expression here.
377 NO. -> Will float past a lambda?
378 (check using free variables only, not type variables)
379 YES. -> do the same as (a) above.
380 NO. -> No point in let binding if it is not going anywhere
381 Pin (leave) expression here.
384 setFloatLevel :: Bool -- True <=> the expression is already let-bound
385 -- False <=> it's a possible MFE
386 -> Level -- of context
389 -> CoreExprWithFVs -- Original rhs
390 -> Type -- Type of rhs
392 -> LvlM (Level, -- Level to attribute to this let-binding
393 LevelledExpr) -- Final rhs
395 setFloatLevel alreadyLetBound ctxt_lvl envs@(venv, tenv)
396 expr@(FVInfo fvs tfvs might_leak, _) ty
397 -- Invariant: ctxt_lvl is never = Top
398 -- Beautiful ASSERT, dudes (WDP 95/04)...
400 -- Now deal with (by not floating) trivial non-let-bound expressions
401 -- which just aren't worth let-binding in order to float. We always
402 -- choose to float even trivial let-bound things because it doesn't do
403 -- any harm, and not floating it may pin something important. For
410 -- Here, if we don't float v we won't float w, which is Bad News.
411 -- If this gives any problems we could restrict the idea to things destined
414 | not alreadyLetBound
415 && (manifestly_whnf || not will_float_past_lambda)
416 = -- Pin whnf non-let-bound expressions,
417 -- or ones which aren't going anywhere useful
418 lvlExpr ctxt_lvl envs expr `thenLvl` \ expr' ->
419 returnLvl (ctxt_lvl, expr')
421 | alreadyLetBound && not worth_type_abstraction
422 = -- Process the expression with a new ctxt_lvl, obtained from
423 -- the free vars of the expression itself
424 lvlExpr (unTopify expr_lvl) envs expr `thenLvl` \ expr' ->
425 returnLvl (maybe_unTopify expr_lvl, expr')
427 | otherwise -- This will create a let anyway, even if there is no
428 -- type variable to abstract, so we try to abstract anyway
429 = abstractWrtTyVars offending_tyvars ty envs lvl_after_ty_abstr expr
430 `thenLvl` \ final_expr ->
431 returnLvl (expr_lvl, final_expr)
432 -- OLD LIE: The body of the let, just a type application, isn't worth floating
433 -- so pin it with ctxt_lvl
434 -- The truth: better to give it expr_lvl in case it is pinning
435 -- something non-trivial which depends on it.
437 fv_list = idSetToList fvs
438 tv_list = tyVarSetToList tfvs
439 expr_lvl = ids_only_lvl `maxLvl` tyvars_only_lvl
440 ids_only_lvl = foldr (maxLvl . idLevel venv) tOP_LEVEL fv_list
441 tyvars_only_lvl = foldr (maxLvl . tyvarLevel tenv) tOP_LEVEL tv_list
442 lvl_after_ty_abstr = ids_only_lvl --`maxLvl` non_offending_tyvars_lvl
444 will_float_past_lambda = -- Will escape lambda if let-bound
445 ids_only_lvl `ltMajLvl` ctxt_lvl
447 worth_type_abstraction = -- Will escape (more) lambda(s)/type lambda(s)
448 -- if type abstracted
449 (ids_only_lvl `ltLvl` tyvars_only_lvl)
450 && not (is_trivial de_ann_expr) -- avoids abstracting trivial type applications
452 de_ann_expr = deAnnotate expr
455 | notValArg a = is_trivial e
456 is_trivial (Var _) = True
459 offending_tyvars = filter offending tv_list
460 --non_offending_tyvars = filter (not . offending) tv_list
461 --non_offending_tyvars_lvl = foldr (maxLvl . tyvarLevel tenv) tOP_LEVEL non_offending_tyvars
463 offending tyvar = ids_only_lvl `ltLvl` tyvarLevel tenv tyvar
465 manifestly_whnf = manifestlyWHNF de_ann_expr || manifestlyBottom de_ann_expr
467 maybe_unTopify Top | not (canFloatToTop (ty, expr)) = Level 0 0
468 maybe_unTopify lvl = lvl
469 {- ToDo [Andre]: the line above (maybe) should be Level 1 0,
470 -- so that the let will not go past the *last* lambda if it can
471 -- generate a space leak. If it is already in major level 0
472 -- It won't do any harm to give it a Level 1 0.
473 -- we should do the same test not only for things with level Top,
474 -- but also for anything that gets a major level 0.
476 f = \a -> let x = [1..1000]
479 f = let x = [1..1000]
481 is just as bad as floating x to the top level.
482 Notice it would be OK in cases like
483 f = \a -> let x = [1..1000]
487 f = let x = [1..1000]
490 as x will be gc'd after y is updated.
491 [We did not hit any problems with the above (Level 0 0) code
496 Abstract wrt tyvars, by making it just as if we had seen
501 instead of simply E. The idea is that v can be freely floated, since it
502 has no free type variables. Of course, if E has no free type
503 variables, then we just return E.
506 abstractWrtTyVars offending_tyvars ty (venv,tenv) lvl expr
507 = lvlExpr incd_lvl new_envs expr `thenLvl` \ expr' ->
508 newLvlVar poly_ty `thenLvl` \ poly_var ->
510 poly_var_rhs = mkTyLam offending_tyvars expr'
511 poly_var_binding = NonRec (poly_var, lvl) poly_var_rhs
512 poly_var_app = mkTyApp (Var poly_var) (mkTyVarTys offending_tyvars)
513 final_expr = Let poly_var_binding poly_var_app -- mkCoLet* requires Core
517 poly_ty = snd (quantifyTy offending_tyvars ty)
519 -- These defns are just like those in the TyLam case of lvlExpr
520 (incd_lvl, tyvar_lvls) = mapAccumL next (unTopify lvl) offending_tyvars
522 next lvl tyvar = (lvl1, (tyvar,lvl1))
523 where lvl1 = incMinorLvl lvl
525 new_tenv = growTyVarEnvList tenv tyvar_lvls
526 new_envs = (venv, new_tenv)
529 Recursive definitions. We want to transform
541 x1' = /\ ab -> let D' in e1
543 xn' = /\ ab -> let D' in en
547 where ab are the tyvars pinning the defn further in than it
548 need be, and D is a bunch of simple type applications:
554 The "_cl" indicates that in D, the level numbers on the xi are the context level
555 number; type applications aren't worth floating. The D' decls are
562 but differ in their level numbers; here the ab are the newly-introduced
566 decideRecFloatLevel ctxt_lvl envs@(venv, tenv) ids rhss
567 | isTopMajLvl ids_only_lvl && -- Destination = top
568 not (all canFloatToTop (tys `zip` rhss)) -- Some can't float to top
571 ids_w_lvls = ids `zip` repeat ctxt_lvl
572 new_envs = (growIdEnvList venv ids_w_lvls, tenv)
574 mapLvl (lvlExpr ctxt_lvl new_envs) rhss `thenLvl` \ rhss' ->
575 returnLvl (ctxt_lvl, [], rhss')
577 {- OMITTED; see comments above near isWorthFloatingExpr
579 | not (any (isWorthFloating True . deAnnotate) rhss)
581 mapLvl (lvlExpr ctxt_lvl envs) rhss `thenLvl` \ rhss' ->
582 returnLvl (ctxt_lvl, [], rhss')
586 | ids_only_lvl `ltLvl` tyvars_only_lvl
587 = -- Abstract wrt tyvars;
588 -- offending_tyvars is definitely non-empty
589 -- (I love the ASSERT to check this... WDP 95/02)
591 -- These defns are just like those in the TyLam case of lvlExpr
592 (incd_lvl, tyvar_lvls) = mapAccumL next (unTopify ids_only_lvl) offending_tyvars
594 next lvl tyvar = (lvl1, (tyvar,lvl1))
595 where lvl1 = incMinorLvl lvl
597 ids_w_incd_lvl = [(id,incd_lvl) | id <- ids]
598 new_tenv = growTyVarEnvList tenv tyvar_lvls
599 new_venv = growIdEnvList venv ids_w_incd_lvl
600 new_envs = (new_venv, new_tenv)
602 mapLvl (lvlExpr incd_lvl new_envs) rhss `thenLvl` \ rhss' ->
603 mapLvl newLvlVar poly_tys `thenLvl` \ poly_vars ->
605 ids_w_poly_vars = ids `zip` poly_vars
607 -- The "d_rhss" are the right-hand sides of "D" and "D'"
608 -- in the documentation above
609 d_rhss = [ mkTyApp (Var poly_var) offending_tyvar_tys | poly_var <- poly_vars]
611 -- "local_binds" are "D'" in the documentation above
612 local_binds = zipWithEqual NonRec ids_w_incd_lvl d_rhss
614 poly_var_rhss = [ mkTyLam offending_tyvars (foldr Let rhs' local_binds)
615 | rhs' <- rhss' -- mkCoLet* requires Core...
618 poly_binds = [(poly_var, ids_only_lvl) | poly_var <- poly_vars] `zip` poly_var_rhss
621 returnLvl (ctxt_lvl, [Rec poly_binds], d_rhss)
622 -- The new right-hand sides, just a type application, aren't worth floating
623 -- so pin it with ctxt_lvl
626 = -- Let it float freely
628 ids_w_lvls = ids `zip` repeat expr_lvl
629 new_envs = (growIdEnvList venv ids_w_lvls, tenv)
631 mapLvl (lvlExpr (unTopify expr_lvl) new_envs) rhss `thenLvl` \ rhss' ->
632 returnLvl (expr_lvl, [], rhss')
637 fvs = unionManyIdSets [freeVarsOf rhs | rhs <- rhss] `minusIdSet` mkIdSet ids
638 tfvs = unionManyTyVarSets [freeTyVarsOf rhs | rhs <- rhss]
639 fv_list = idSetToList fvs
640 tv_list = tyVarSetToList tfvs
642 ids_only_lvl = foldr (maxLvl . idLevel venv) tOP_LEVEL fv_list
643 tyvars_only_lvl = foldr (maxLvl . tyvarLevel tenv) tOP_LEVEL tv_list
644 expr_lvl = ids_only_lvl `maxLvl` tyvars_only_lvl
647 | ids_only_lvl `ltLvl` tyvars_only_lvl = filter offending tv_list
650 offending_tyvar_tys = mkTyVarTys offending_tyvars
651 poly_tys = [ snd (quantifyTy offending_tyvars ty)
655 offending tyvar = ids_only_lvl `ltLvl` tyvarLevel tenv tyvar
660 {- ******** OMITTED NOW
662 isWorthFloating :: Bool -- True <=> already let-bound
663 -> CoreExpr -- The expression
666 isWorthFloating alreadyLetBound expr
668 | alreadyLetBound = isWorthFloatingExpr expr
670 | otherwise = -- No point in adding a fresh let-binding for a WHNF, because
671 -- floating it isn't beneficial enough.
672 isWorthFloatingExpr expr &&
673 not (manifestlyWHNF expr || manifestlyBottom expr)
676 isWorthFloatingExpr :: CoreExpr -> Bool
678 isWorthFloatingExpr (Var v) = False
679 isWorthFloatingExpr (Lit lit) = False
680 isWorthFloatingExpr (App e arg)
681 | notValArg arg = isWorthFloatingExpr e
682 isWorthFloatingExpr (Con con as)
683 | all notValArg as = False -- Just a type application
684 isWorthFloatingExpr _ = True
686 canFloatToTop :: (Type, CoreExprWithFVs) -> Bool
688 canFloatToTop (ty, (FVInfo _ _ (LeakFree _), expr)) = True
689 canFloatToTop (ty, (FVInfo _ _ MightLeak, expr)) = isLeakFreeType [] ty
691 valSuggestsLeakFree expr = manifestlyWHNF expr || manifestlyBottom expr
696 %************************************************************************
698 \subsection{Help functions}
700 %************************************************************************
703 idLevel :: IdEnv Level -> Id -> Level
705 = case lookupIdEnv venv v of
707 Nothing -> ASSERT(toplevelishId v)
710 tyvarLevel :: TyVarEnv Level -> TyVar -> Level
711 tyvarLevel tenv tyvar
712 = case lookupTyVarEnv tenv tyvar of
717 %************************************************************************
719 \subsection{Free-To-Level Monad}
721 %************************************************************************
724 type LvlM result = UniqSM result
729 mapAndUnzipLvl = mapAndUnzipUs
730 mapAndUnzip3Lvl = mapAndUnzip3Us
733 We create a let-binding for `interesting' (non-utterly-trivial)
734 applications, to give them a fighting chance of being floated.
737 newLvlVar :: Type -> LvlM Id
740 = mkSysLocal SLIT("lvl") (getUnique us) ty mkUnknownSrcLoc