2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
6 ***************************
8 ***************************
10 * We attach binding levels to Core bindings, in preparation for floating
11 outwards (@FloatOut@).
13 * We also let-ify many expressions (notably case scrutinees), so they
14 will have a fighting chance of being floated sensible.
16 * 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.)
19 NOTE: Very tiresomely, we must apply this substitution to
20 the rules stored inside a variable too.
22 We do *not* clone top-level bindings, because some of them must not change,
23 but we *do* clone bindings that are heading for the top level
26 case x of wild { p -> ...wild... }
27 we substitute x for wild in the RHS of the case alternatives:
28 case x of wild { p -> ...x... }
29 This means that a sub-expression involving x is not "trapped" inside the RHS.
30 And it's not inconvenient because we already have a substitution.
38 incMinorLvl, ltMajLvl, ltLvl, isTopLvl
41 #include "HsVersions.h"
45 import CoreUtils ( exprType, exprIsTrivial, exprIsBottom, mkPiType )
46 import CoreFVs -- all of it
48 import Id ( Id, idType, idFreeTyVars, mkSysLocal, isOneShotLambda, modifyIdInfo,
49 idSpecialisation, idWorkerInfo, setIdInfo
51 import IdInfo ( workerExists, vanillaIdInfo, demandInfo, setDemandInfo )
52 import Var ( Var, TyVar, setVarUnique )
55 import Name ( getOccName )
56 import OccName ( occNameUserString )
57 import Type ( isUnLiftedType, Type )
58 import BasicTypes ( TopLevelFlag(..) )
59 import Demand ( isStrict, wwLazy )
61 import Util ( sortLt, isSingleton, count )
65 %************************************************************************
67 \subsection{Level numbers}
69 %************************************************************************
72 data Level = Level Int -- Level number of enclosing lambdas
73 Int -- Number of big-lambda and/or case expressions between
74 -- here and the nearest enclosing lambda
77 The {\em level number} on a (type-)lambda-bound variable is the
78 nesting depth of the (type-)lambda which binds it. The outermost lambda
79 has level 1, so (Level 0 0) means that the variable is bound outside any lambda.
81 On an expression, it's the maximum level number of its free
82 (type-)variables. On a let(rec)-bound variable, it's the level of its
83 RHS. On a case-bound variable, it's the number of enclosing lambdas.
85 Top-level variables: level~0. Those bound on the RHS of a top-level
86 definition but ``before'' a lambda; e.g., the \tr{x} in (levels shown
89 a_0 = let b_? = ... in
90 x_1 = ... b ... in ...
93 The main function @lvlExpr@ carries a ``context level'' (@ctxt_lvl@).
94 That's meant to be the level number of the enclosing binder in the
95 final (floated) program. If the level number of a sub-expression is
96 less than that of the context, then it might be worth let-binding the
97 sub-expression so that it will indeed float. This context level starts
101 type LevelledExpr = TaggedExpr Level
102 type LevelledArg = TaggedArg Level
103 type LevelledBind = TaggedBind Level
105 tOP_LEVEL = Level 0 0
107 incMajorLvl :: Level -> Level
108 incMajorLvl (Level major minor) = Level (major+1) 0
110 incMinorLvl :: Level -> Level
111 incMinorLvl (Level major minor) = Level major (minor+1)
113 maxLvl :: Level -> Level -> Level
114 maxLvl l1@(Level maj1 min1) l2@(Level maj2 min2)
115 | (maj1 > maj2) || (maj1 == maj2 && min1 > min2) = l1
118 ltLvl :: Level -> Level -> Bool
119 ltLvl (Level maj1 min1) (Level maj2 min2)
120 = (maj1 < maj2) || (maj1 == maj2 && min1 < min2)
122 ltMajLvl :: Level -> Level -> Bool
123 -- Tells if one level belongs to a difft *lambda* level to another
124 -- But it returns True regardless if l1 is the top level
125 -- We always like to float to the top!
126 ltMajLvl (Level 0 0) _ = True
127 ltMajLvl (Level maj1 _) (Level maj2 _) = maj1 < maj2
129 isTopLvl :: Level -> Bool
130 isTopLvl (Level 0 0) = True
131 isTopLvl other = False
133 instance Outputable Level where
134 ppr (Level maj min) = hcat [ char '<', int maj, char ',', int min, char '>' ]
137 %************************************************************************
139 \subsection{Main level-setting code}
141 %************************************************************************
144 setLevels :: Bool -- True <=> float lambdas to top level
149 setLevels float_lams binds us
150 = initLvl us (do_them binds)
152 -- "do_them"'s main business is to thread the monad along
153 -- It gives each top binding the same empty envt, because
154 -- things unbound in the envt have level number zero implicitly
155 do_them :: [CoreBind] -> LvlM [LevelledBind]
157 do_them [] = returnLvl []
159 = lvlTopBind init_env b `thenLvl` \ (lvld_bind, _) ->
160 do_them bs `thenLvl` \ lvld_binds ->
161 returnLvl (lvld_bind : lvld_binds)
163 init_env = initialEnv float_lams
165 lvlTopBind env (NonRec binder rhs)
166 = lvlBind TopLevel tOP_LEVEL env (AnnNonRec binder (freeVars rhs))
167 -- Rhs can have no free vars!
169 lvlTopBind env (Rec pairs)
170 = lvlBind TopLevel tOP_LEVEL env (AnnRec [(b,freeVars rhs) | (b,rhs) <- pairs])
173 %************************************************************************
175 \subsection{Setting expression levels}
177 %************************************************************************
180 lvlExpr :: Level -- ctxt_lvl: Level of enclosing expression
181 -> LevelEnv -- Level of in-scope names/tyvars
182 -> CoreExprWithFVs -- input expression
183 -> LvlM LevelledExpr -- Result expression
186 The @ctxt_lvl@ is, roughly, the level of the innermost enclosing
187 binder. Here's an example
189 v = \x -> ...\y -> let r = case (..x..) of
193 When looking at the rhs of @r@, @ctxt_lvl@ will be 1 because that's
194 the level of @r@, even though it's inside a level-2 @\y@. It's
195 important that @ctxt_lvl@ is 1 and not 2 in @r@'s rhs, because we
196 don't want @lvlExpr@ to turn the scrutinee of the @case@ into an MFE
197 --- because it isn't a *maximal* free expression.
199 If there were another lambda in @r@'s rhs, it would get level-2 as well.
202 lvlExpr _ _ (_, AnnType ty) = returnLvl (Type ty)
203 lvlExpr _ env (_, AnnVar v) = returnLvl (lookupVar env v)
204 lvlExpr _ env (_, AnnLit lit) = returnLvl (Lit lit)
206 lvlExpr ctxt_lvl env (_, AnnApp fun arg)
207 = lvl_fun fun `thenLvl` \ fun' ->
208 lvlMFE False ctxt_lvl env arg `thenLvl` \ arg' ->
209 returnLvl (App fun' arg')
211 lvl_fun (_, AnnCase _ _ _) = lvlMFE True ctxt_lvl env fun
212 lvl_fun other = lvlExpr ctxt_lvl env fun
213 -- We don't do MFE on partial applications generally,
214 -- but we do if the function is big and hairy, like a case
216 lvlExpr ctxt_lvl env (_, AnnNote InlineMe expr)
217 -- Don't float anything out of an InlineMe
218 = lvlExpr tOP_LEVEL env expr `thenLvl` \ expr' ->
219 returnLvl (Note InlineMe expr')
221 lvlExpr ctxt_lvl env (_, AnnNote note expr)
222 = lvlExpr ctxt_lvl env expr `thenLvl` \ expr' ->
223 returnLvl (Note note expr')
225 -- We don't split adjacent lambdas. That is, given
227 -- we don't float to give
228 -- \x -> let v = x+y in \y -> (v,y)
229 -- Why not? Because partial applications are fairly rare, and splitting
230 -- lambdas makes them more expensive.
232 lvlExpr ctxt_lvl env expr@(_, AnnLam bndr rhs)
233 = lvlMFE True new_lvl new_env body `thenLvl` \ new_body ->
234 returnLvl (glue_binders new_bndrs expr new_body)
236 (bndrs, body) = collect_binders expr
237 (new_lvl, new_bndrs) = lvlLamBndrs ctxt_lvl bndrs
238 new_env = extendLvlEnv env new_bndrs
240 lvlExpr ctxt_lvl env (_, AnnLet bind body)
241 = lvlBind NotTopLevel ctxt_lvl env bind `thenLvl` \ (bind', new_env) ->
242 lvlExpr ctxt_lvl new_env body `thenLvl` \ body' ->
243 returnLvl (Let bind' body')
245 lvlExpr ctxt_lvl env (_, AnnCase expr case_bndr alts)
246 = lvlMFE True ctxt_lvl env expr `thenLvl` \ expr' ->
248 alts_env = extendCaseBndrLvlEnv env expr' case_bndr incd_lvl
250 mapLvl (lvl_alt alts_env) alts `thenLvl` \ alts' ->
251 returnLvl (Case expr' (case_bndr, incd_lvl) alts')
253 expr_type = exprType (deAnnotate expr)
254 incd_lvl = incMinorLvl ctxt_lvl
256 lvl_alt alts_env (con, bs, rhs)
257 = lvlMFE True incd_lvl new_env rhs `thenLvl` \ rhs' ->
258 returnLvl (con, bs', rhs')
260 bs' = [ (b, incd_lvl) | b <- bs ]
261 new_env = extendLvlEnv alts_env bs'
266 go rev_bndrs (_, AnnLam b e) = go (b:rev_bndrs) e
267 go rev_bndrs (_, AnnNote n e) = go rev_bndrs e
268 go rev_bndrs rhs = (reverse rev_bndrs, rhs)
269 -- Ignore notes, because we don't want to split
270 -- a lambda like this (\x -> coerce t (\s -> ...))
271 -- This happens quite a bit in state-transformer programs
273 -- glue_binders puts the lambda back together
274 glue_binders (b:bs) (_, AnnLam _ e) body = Lam b (glue_binders bs e body)
275 glue_binders bs (_, AnnNote n e) body = Note n (glue_binders bs e body)
276 glue_binders [] e body = body
279 @lvlMFE@ is just like @lvlExpr@, except that it might let-bind
280 the expression, so that it can itself be floated.
283 lvlMFE :: Bool -- True <=> strict context [body of case or let]
284 -> Level -- Level of innermost enclosing lambda/tylam
285 -> LevelEnv -- Level of in-scope names/tyvars
286 -> CoreExprWithFVs -- input expression
287 -> LvlM LevelledExpr -- Result expression
289 lvlMFE strict_ctxt ctxt_lvl env (_, AnnType ty)
290 = returnLvl (Type ty)
292 lvlMFE strict_ctxt ctxt_lvl env ann_expr@(fvs, _)
293 | isUnLiftedType ty -- Can't let-bind it
294 || not good_destination
295 || exprIsTrivial expr -- Is trivial
296 || (strict_ctxt && exprIsBottom expr) -- Strict context and is bottom
297 = -- Don't float it out
298 lvlExpr ctxt_lvl env ann_expr
300 | otherwise -- Float it out!
301 = lvlFloatRhs abs_vars dest_lvl env ann_expr `thenLvl` \ expr' ->
302 newLvlVar "lvl" abs_vars ty `thenLvl` \ var ->
303 returnLvl (Let (NonRec (var,dest_lvl) expr')
304 (mkVarApps (Var var) abs_vars))
306 expr = deAnnotate ann_expr
308 dest_lvl = destLevel env fvs (isFunction ann_expr)
309 abs_vars = abstractVars dest_lvl env fvs
311 good_destination = dest_lvl `ltMajLvl` ctxt_lvl -- Escapes a value lambda
312 || (isTopLvl dest_lvl && not strict_ctxt) -- Goes to the top
313 -- A decision to float entails let-binding this thing, and we only do
314 -- that if we'll escape a value lambda, or will go to the top level.
316 -- concat = /\ a -> foldr ..a.. (++) []
317 -- was getting turned into
318 -- concat = /\ a -> lvl a
319 -- lvl = /\ a -> foldr ..a.. (++) []
320 -- which is pretty stupid. Hence the strict_ctxt test
324 %************************************************************************
326 \subsection{Bindings}
328 %************************************************************************
330 The binding stuff works for top level too.
333 lvlBind :: TopLevelFlag -- Used solely to decide whether to clone
334 -> Level -- Context level; might be Top even for bindings nested in the RHS
335 -- of a top level binding
338 -> LvlM (LevelledBind, LevelEnv)
340 lvlBind top_lvl ctxt_lvl env (AnnNonRec bndr rhs@(rhs_fvs,_))
342 = -- No type abstraction; clone existing binder
343 lvlExpr ctxt_lvl env rhs `thenLvl` \ rhs' ->
344 cloneVar top_lvl env bndr ctxt_lvl dest_lvl `thenLvl` \ (env', bndr') ->
345 returnLvl (NonRec (bndr', dest_lvl) rhs', env')
348 = -- Yes, type abstraction; create a new binder, extend substitution, etc
349 lvlFloatRhs abs_vars dest_lvl env rhs `thenLvl` \ rhs' ->
350 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (env', [bndr']) ->
351 returnLvl (NonRec (bndr', dest_lvl) rhs', env')
354 bind_fvs = rhs_fvs `unionVarSet` idFreeVars bndr
355 abs_vars = abstractVars dest_lvl env bind_fvs
357 dest_lvl | isUnLiftedType (idType bndr) = destLevel env bind_fvs False `maxLvl` Level 1 0
358 | otherwise = destLevel env bind_fvs (isFunction rhs)
359 -- Hack alert! We do have some unlifted bindings, for cheap primops, and
360 -- it is ok to float them out; but not to the top level. If they would otherwise
361 -- go to the top level, we pin them inside the topmost lambda
366 lvlBind top_lvl ctxt_lvl env (AnnRec pairs)
368 = cloneVars top_lvl env bndrs ctxt_lvl dest_lvl `thenLvl` \ (new_env, new_bndrs) ->
369 mapLvl (lvlExpr ctxt_lvl new_env) rhss `thenLvl` \ new_rhss ->
370 returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env)
372 | isSingleton pairs && count isId abs_vars > 1
373 = -- Special case for self recursion where there are
374 -- several variables carried around: build a local loop:
375 -- poly_f = \abs_vars. \lam_vars . letrec f = \lam_vars. rhs in f lam_vars
376 -- This just makes the closures a bit smaller. If we don't do
377 -- this, allocation rises significantly on some programs
379 -- We could elaborate it for the case where there are several
380 -- mutually functions, but it's quite a bit more complicated
382 -- This all seems a bit ad hoc -- sigh
384 (bndr,rhs) = head pairs
385 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
386 rhs_env = extendLvlEnv env abs_vars_w_lvls
388 cloneVar NotTopLevel rhs_env bndr rhs_lvl rhs_lvl `thenLvl` \ (rhs_env', new_bndr) ->
390 (lam_bndrs, rhs_body) = collect_binders rhs
391 (body_lvl, new_lam_bndrs) = lvlLamBndrs rhs_lvl lam_bndrs
392 body_env = extendLvlEnv rhs_env' new_lam_bndrs
394 lvlExpr body_lvl body_env rhs_body `thenLvl` \ new_rhs_body ->
395 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (poly_env, [poly_bndr]) ->
396 returnLvl (Rec [((poly_bndr,dest_lvl), mkLams abs_vars_w_lvls $
397 glue_binders new_lam_bndrs rhs $
398 Let (Rec [((new_bndr,rhs_lvl), mkLams new_lam_bndrs new_rhs_body)])
399 (mkVarApps (Var new_bndr) lam_bndrs))],
403 = newPolyBndrs dest_lvl env abs_vars bndrs `thenLvl` \ (new_env, new_bndrs) ->
404 mapLvl (lvlFloatRhs abs_vars dest_lvl new_env) rhss `thenLvl` \ new_rhss ->
405 returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env)
408 (bndrs,rhss) = unzip pairs
410 -- Finding the free vars of the binding group is annoying
411 bind_fvs = (unionVarSets [ idFreeVars bndr `unionVarSet` rhs_fvs
412 | (bndr, (rhs_fvs,_)) <- pairs])
416 dest_lvl = destLevel env bind_fvs (all isFunction rhss)
417 abs_vars = abstractVars dest_lvl env bind_fvs
419 ----------------------------------------------------
420 -- Three help functons for the type-abstraction case
422 lvlFloatRhs abs_vars dest_lvl env rhs
423 = lvlExpr rhs_lvl rhs_env rhs `thenLvl` \ rhs' ->
424 returnLvl (mkLams abs_vars_w_lvls rhs')
426 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
427 rhs_env = extendLvlEnv env abs_vars_w_lvls
431 %************************************************************************
433 \subsection{Deciding floatability}
435 %************************************************************************
438 lvlLamBndrs :: Level -> [CoreBndr] -> (Level, [(CoreBndr, Level)])
439 -- Compute the levels for the binders of a lambda group
443 lvlLamBndrs lvl bndrs
444 = go (incMinorLvl lvl)
445 False -- Havn't bumped major level in this group
448 go old_lvl bumped_major rev_lvld_bndrs (bndr:bndrs)
449 | isId bndr && -- Go to the next major level if this is a value binder,
450 not bumped_major && -- and we havn't already gone to the next level (one jump per group)
451 not (isOneShotLambda bndr) -- and it isn't a one-shot lambda
452 = go new_lvl True ((bndr,new_lvl) : rev_lvld_bndrs) bndrs
455 = go old_lvl bumped_major ((bndr,old_lvl) : rev_lvld_bndrs) bndrs
458 new_lvl = incMajorLvl old_lvl
460 go old_lvl _ rev_lvld_bndrs []
461 = (old_lvl, reverse rev_lvld_bndrs)
462 -- a lambda like this (\x -> coerce t (\s -> ...))
463 -- This happens quite a bit in state-transformer programs
467 abstractVars :: Level -> LevelEnv -> VarSet -> [Var]
468 -- Find the variables in fvs, free vars of the target expresion,
469 -- whose level is less than than the supplied level
470 -- These are the ones we are going to abstract out
471 abstractVars dest_lvl env fvs
472 = uniq (sortLt lt [var | fv <- varSetElems fvs, var <- absVarsOf dest_lvl env fv])
474 -- Sort the variables so we don't get
475 -- mixed-up tyvars and Ids; it's just messy
476 v1 `lt` v2 = case (isId v1, isId v2) of
477 (True, False) -> False
478 (False, True) -> True
479 other -> v1 < v2 -- Same family
480 uniq :: [Var] -> [Var]
481 -- Remove adjacent duplicates; the sort will have brought them together
482 uniq (v1:v2:vs) | v1 == v2 = uniq (v2:vs)
483 | otherwise = v1 : uniq (v2:vs)
486 -- Destintion level is the max Id level of the expression
487 -- (We'll abstract the type variables, if any.)
488 destLevel :: LevelEnv -> VarSet -> Bool -> Level
489 destLevel env fvs is_function
491 && is_function = tOP_LEVEL -- Send functions to top level; see
492 -- the comments with isFunction
493 | otherwise = maxIdLevel env fvs
495 isFunction :: CoreExprWithFVs -> Bool
496 -- The idea here is that we want to float *functions* to
497 -- the top level. This saves no work, but
498 -- (a) it can make the host function body a lot smaller,
499 -- and hence inlinable.
500 -- (b) it can also save allocation when the function is recursive:
501 -- h = \x -> letrec f = \y -> ...f...y...x...
504 -- f = \x y -> ...(f x)...y...x...
506 -- No allocation for f now.
507 -- We may only want to do this if there are sufficiently few free
508 -- variables. We certainly only want to do it for values, and not for
509 -- constructors. So the simple thing is just to look for lambdas
510 isFunction (_, AnnLam b e) | isId b = True
511 | otherwise = isFunction e
512 isFunction (_, AnnNote n e) = isFunction e
513 isFunction other = False
517 %************************************************************************
519 \subsection{Free-To-Level Monad}
521 %************************************************************************
524 type LevelEnv = (Bool, -- True <=> Float lambdas too
525 VarEnv Level, -- Domain is *post-cloned* TyVars and Ids
526 SubstEnv, -- Domain is pre-cloned Ids
527 IdEnv ([Var], LevelledExpr)) -- Domain is pre-cloned Ids
528 -- We clone let-bound variables so that they are still
529 -- distinct when floated out; hence the SubstEnv/IdEnv.
530 -- We also use these envs when making a variable polymorphic
531 -- because we want to float it out past a big lambda.
533 -- The two Envs always implement the same mapping, but the
534 -- SubstEnv maps to CoreExpr and the IdEnv to LevelledExpr
535 -- Since the range is always a variable or type application,
536 -- there is never any difference between the two, but sadly
537 -- the types differ. The SubstEnv is used when substituting in
538 -- a variable's IdInfo; the IdEnv when we find a Var.
540 -- In addition the IdEnv records a list of tyvars free in the
541 -- type application, just so we don't have to call freeVars on
542 -- the type application repeatedly.
544 -- The domain of the both envs is *pre-cloned* Ids, though
546 -- The domain of the VarEnv Level is the *post-cloned* Ids
548 initialEnv :: Bool -> LevelEnv
549 initialEnv float_lams = (float_lams, emptyVarEnv, emptySubstEnv, emptyVarEnv)
551 floatLams :: LevelEnv -> Bool
552 floatLams (float_lams, _, _, _) = float_lams
554 extendLvlEnv :: LevelEnv -> [(Var,Level)] -> LevelEnv
555 -- Used when *not* cloning
556 extendLvlEnv (float_lams, lvl_env, subst_env, id_env) prs
557 = (float_lams, foldl add lvl_env prs, subst_env, id_env)
559 add env (v,l) = extendVarEnv env v l
561 -- extendCaseBndrLvlEnv adds the mapping case-bndr->scrut-var if it can
562 extendCaseBndrLvlEnv env scrut case_bndr lvl
564 Var v -> extendCloneLvlEnv lvl env [(case_bndr, v)]
565 other -> extendLvlEnv env [(case_bndr,lvl)]
567 extendPolyLvlEnv dest_lvl (float_lams, lvl_env, subst_env, id_env) abs_vars bndr_pairs
569 foldl add_lvl lvl_env bndr_pairs,
570 foldl add_subst subst_env bndr_pairs,
571 foldl add_id id_env bndr_pairs)
573 add_lvl env (v,v') = extendVarEnv env v' dest_lvl
574 add_subst env (v,v') = extendSubstEnv env v (DoneEx (mkVarApps (Var v') abs_vars))
575 add_id env (v,v') = extendVarEnv env v ((v':abs_vars), mkVarApps (Var v') abs_vars)
577 extendCloneLvlEnv lvl (float_lams, lvl_env, subst_env, id_env) bndr_pairs
579 foldl add_lvl lvl_env bndr_pairs,
580 foldl add_subst subst_env bndr_pairs,
581 foldl add_id id_env bndr_pairs)
583 add_lvl env (v,v') = extendVarEnv env v' lvl
584 add_subst env (v,v') = extendSubstEnv env v (DoneEx (Var v'))
585 add_id env (v,v') = extendVarEnv env v ([v'], Var v')
588 maxIdLevel :: LevelEnv -> VarSet -> Level
589 maxIdLevel (_, lvl_env,_,id_env) var_set
590 = foldVarSet max_in tOP_LEVEL var_set
592 max_in in_var lvl = foldr max_out lvl (case lookupVarEnv id_env in_var of
593 Just (abs_vars, _) -> abs_vars
597 | isId out_var = case lookupVarEnv lvl_env out_var of
598 Just lvl' -> maxLvl lvl' lvl
600 | otherwise = lvl -- Ignore tyvars in *maxIdLevel*
602 lookupVar :: LevelEnv -> Id -> LevelledExpr
603 lookupVar (_, _, _, id_env) v = case lookupVarEnv id_env v of
604 Just (_, expr) -> expr
607 absVarsOf :: Level -> LevelEnv -> Var -> [Var]
608 -- If f is free in the exression, and f maps to poly_f a b c in the
609 -- current substitution, then we must report a b c as candidate type
611 absVarsOf dest_lvl (_, lvl_env, _, id_env) v
613 = [final_av | av <- lookup_avs v, abstract_me av, final_av <- add_tyvars av]
616 = if abstract_me v then [v] else []
619 abstract_me v = case lookupVarEnv lvl_env v of
620 Just lvl -> dest_lvl `ltLvl` lvl
623 lookup_avs v = case lookupVarEnv id_env v of
624 Just (abs_vars, _) -> abs_vars
627 -- We are going to lambda-abstract, so nuke any IdInfo,
628 -- and add the tyvars of the Id
629 add_tyvars v | isId v = zap v : varSetElems (idFreeTyVars v)
632 zap v = WARN( workerExists (idWorkerInfo v)
633 || not (isEmptyCoreRules (idSpecialisation v)),
634 text "absVarsOf: discarding info on" <+> ppr v )
635 setIdInfo v vanillaIdInfo
639 type LvlM result = UniqSM result
648 newPolyBndrs dest_lvl env abs_vars bndrs
649 = getUniquesUs (length bndrs) `thenLvl` \ uniqs ->
651 new_bndrs = zipWith mk_poly_bndr bndrs uniqs
653 returnLvl (extendPolyLvlEnv dest_lvl env abs_vars (bndrs `zip` new_bndrs), new_bndrs)
655 mk_poly_bndr bndr uniq = mkSysLocal (_PK_ str) uniq poly_ty
657 str = "poly_" ++ occNameUserString (getOccName bndr)
658 poly_ty = foldr mkPiType (idType bndr) abs_vars
662 -> [CoreBndr] -> Type -- Abstract wrt these bndrs
664 newLvlVar str vars body_ty
665 = getUniqueUs `thenLvl` \ uniq ->
666 returnUs (mkSysLocal (_PK_ str) uniq (foldr mkPiType body_ty vars))
668 -- The deeply tiresome thing is that we have to apply the substitution
669 -- to the rules inside each Id. Grr. But it matters.
671 cloneVar :: TopLevelFlag -> LevelEnv -> Id -> Level -> Level -> LvlM (LevelEnv, Id)
672 cloneVar TopLevel env v ctxt_lvl dest_lvl
673 = returnUs (env, v) -- Don't clone top level things
674 cloneVar NotTopLevel env v ctxt_lvl dest_lvl
676 getUniqueUs `thenLvl` \ uniq ->
678 v' = setVarUnique v uniq
679 v'' = subst_id_info env ctxt_lvl dest_lvl v'
680 env' = extendCloneLvlEnv dest_lvl env [(v,v'')]
684 cloneVars :: TopLevelFlag -> LevelEnv -> [Id] -> Level -> Level -> LvlM (LevelEnv, [Id])
685 cloneVars TopLevel env vs ctxt_lvl dest_lvl
686 = returnUs (env, vs) -- Don't clone top level things
687 cloneVars NotTopLevel env vs ctxt_lvl dest_lvl
688 = ASSERT( all isId vs )
689 getUniquesUs (length vs) `thenLvl` \ uniqs ->
691 vs' = zipWith setVarUnique vs uniqs
692 vs'' = map (subst_id_info env' ctxt_lvl dest_lvl) vs'
693 env' = extendCloneLvlEnv dest_lvl env (vs `zip` vs'')
695 returnUs (env', vs'')
697 subst_id_info (_, _, subst_env, _) ctxt_lvl dest_lvl v
698 = modifyIdInfo (\info -> substIdInfo subst info (zap_dmd info)) v
700 subst = mkSubst emptyVarSet subst_env
702 -- VERY IMPORTANT: we must zap the demand info
703 -- if the thing is going to float out past a lambda
705 | float_past_lam && isStrict (demandInfo info)
706 = setDemandInfo info wwLazy
710 float_past_lam = ctxt_lvl `ltMajLvl` dest_lvl