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 -- But it returns True regardless if l1 is the top level
137 -- We always like to float to the top!
138 ltMajLvl (Level 0 0) _ = True
139 ltMajLvl (Level maj1 _) (Level maj2 _) = maj1 < maj2
141 isTopLvl :: Level -> Bool
142 isTopLvl (Level 0 0) = True
143 isTopLvl other = False
145 instance Outputable Level where
146 ppr (Level maj min) = hcat [ char '<', int maj, char ',', int min, char '>' ]
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
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 = -- Don't float it out
309 lvlExpr ctxt_lvl env ann_expr
311 | otherwise -- Float it out!
312 = lvlFloatRhs abs_vars dest_lvl env ann_expr `thenLvl` \ expr' ->
313 newLvlVar "lvl" abs_vars ty `thenLvl` \ var ->
314 returnLvl (Let (NonRec (var,dest_lvl) expr')
315 (mkVarApps (Var var) abs_vars))
317 expr = deAnnotate ann_expr
319 dest_lvl = destLevel env fvs (isFunction ann_expr)
320 abs_vars = abstractVars dest_lvl env fvs
322 good_destination = dest_lvl `ltMajLvl` ctxt_lvl -- Escapes a value lambda
323 || (isTopLvl dest_lvl && not strict_ctxt) -- Goes to the top
324 -- A decision to float entails let-binding this thing, and we only do
325 -- that if we'll escape a value lambda, or will go to the top level.
327 -- concat = /\ a -> foldr ..a.. (++) []
328 -- was getting turned into
329 -- concat = /\ a -> lvl a
330 -- lvl = /\ a -> foldr ..a.. (++) []
331 -- which is pretty stupid. Hence the strict_ctxt test
335 %************************************************************************
337 \subsection{Bindings}
339 %************************************************************************
341 The binding stuff works for top level too.
344 lvlBind :: TopLevelFlag -- Used solely to decide whether to clone
345 -> Level -- Context level; might be Top even for bindings nested in the RHS
346 -- of a top level binding
349 -> LvlM (LevelledBind, LevelEnv)
351 lvlBind top_lvl ctxt_lvl env (AnnNonRec bndr rhs@(rhs_fvs,_))
353 = -- No type abstraction; clone existing binder
354 lvlExpr ctxt_lvl env rhs `thenLvl` \ rhs' ->
355 cloneVar top_lvl env bndr ctxt_lvl dest_lvl `thenLvl` \ (env', bndr') ->
356 returnLvl (NonRec (bndr', dest_lvl) rhs', env')
359 = -- Yes, type abstraction; create a new binder, extend substitution, etc
360 lvlFloatRhs abs_vars dest_lvl env rhs `thenLvl` \ rhs' ->
361 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (env', [bndr']) ->
362 returnLvl (NonRec (bndr', dest_lvl) rhs', env')
365 bind_fvs = rhs_fvs `unionVarSet` idFreeVars bndr
366 abs_vars = abstractVars dest_lvl env bind_fvs
368 dest_lvl | isUnLiftedType (idType bndr) = destLevel env bind_fvs False `maxLvl` Level 1 0
369 | otherwise = destLevel env bind_fvs (isFunction rhs)
370 -- Hack alert! We do have some unlifted bindings, for cheap primops, and
371 -- it is ok to float them out; but not to the top level. If they would otherwise
372 -- go to the top level, we pin them inside the topmost lambda
377 lvlBind top_lvl ctxt_lvl env (AnnRec pairs)
379 = cloneVars top_lvl env bndrs ctxt_lvl dest_lvl `thenLvl` \ (new_env, new_bndrs) ->
380 mapLvl (lvlExpr ctxt_lvl new_env) rhss `thenLvl` \ new_rhss ->
381 returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env)
383 | isSingleton pairs && count isId abs_vars > 1
384 = -- Special case for self recursion where there are
385 -- several variables carried around: build a local loop:
386 -- poly_f = \abs_vars. \lam_vars . letrec f = \lam_vars. rhs in f lam_vars
387 -- This just makes the closures a bit smaller. If we don't do
388 -- this, allocation rises significantly on some programs
390 -- We could elaborate it for the case where there are several
391 -- mutually functions, but it's quite a bit more complicated
393 -- This all seems a bit ad hoc -- sigh
395 (bndr,rhs) = head pairs
396 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
397 rhs_env = extendLvlEnv env abs_vars_w_lvls
399 cloneVar NotTopLevel rhs_env bndr rhs_lvl rhs_lvl `thenLvl` \ (rhs_env', new_bndr) ->
401 (lam_bndrs, rhs_body) = collect_binders rhs
402 (body_lvl, new_lam_bndrs) = lvlLamBndrs rhs_lvl lam_bndrs
403 body_env = extendLvlEnv rhs_env' new_lam_bndrs
405 lvlExpr body_lvl body_env rhs_body `thenLvl` \ new_rhs_body ->
406 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (poly_env, [poly_bndr]) ->
407 returnLvl (Rec [((poly_bndr,dest_lvl), mkLams abs_vars_w_lvls $
408 glue_binders new_lam_bndrs rhs $
409 Let (Rec [((new_bndr,rhs_lvl), mkLams new_lam_bndrs new_rhs_body)])
410 (mkVarApps (Var new_bndr) lam_bndrs))],
414 = newPolyBndrs dest_lvl env abs_vars bndrs `thenLvl` \ (new_env, new_bndrs) ->
415 mapLvl (lvlFloatRhs abs_vars dest_lvl new_env) rhss `thenLvl` \ new_rhss ->
416 returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env)
419 (bndrs,rhss) = unzip pairs
421 -- Finding the free vars of the binding group is annoying
422 bind_fvs = (unionVarSets [ idFreeVars bndr `unionVarSet` rhs_fvs
423 | (bndr, (rhs_fvs,_)) <- pairs])
427 dest_lvl = destLevel env bind_fvs (all isFunction rhss)
428 abs_vars = abstractVars dest_lvl env bind_fvs
430 ----------------------------------------------------
431 -- Three help functons for the type-abstraction case
433 lvlFloatRhs abs_vars dest_lvl env rhs
434 = lvlExpr rhs_lvl rhs_env rhs `thenLvl` \ rhs' ->
435 returnLvl (mkLams abs_vars_w_lvls rhs')
437 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
438 rhs_env = extendLvlEnv env abs_vars_w_lvls
442 %************************************************************************
444 \subsection{Deciding floatability}
446 %************************************************************************
449 lvlLamBndrs :: Level -> [CoreBndr] -> (Level, [(CoreBndr, Level)])
450 -- Compute the levels for the binders of a lambda group
451 -- The binders returned are exactly the same as the ones passed,
452 -- but they are now paired with a level
456 lvlLamBndrs lvl bndrs
457 = go (incMinorLvl lvl)
458 False -- Havn't bumped major level in this group
461 go old_lvl bumped_major rev_lvld_bndrs (bndr:bndrs)
462 | isId bndr && -- Go to the next major level if this is a value binder,
463 not bumped_major && -- and we havn't already gone to the next level (one jump per group)
464 not (isOneShotLambda bndr) -- and it isn't a one-shot lambda
465 = go new_lvl True ((bndr,new_lvl) : rev_lvld_bndrs) bndrs
468 = go old_lvl bumped_major ((bndr,old_lvl) : rev_lvld_bndrs) bndrs
471 new_lvl = incMajorLvl old_lvl
473 go old_lvl _ rev_lvld_bndrs []
474 = (old_lvl, reverse rev_lvld_bndrs)
475 -- a lambda like this (\x -> coerce t (\s -> ...))
476 -- This happens quite a bit in state-transformer programs
480 abstractVars :: Level -> LevelEnv -> VarSet -> [Var]
481 -- Find the variables in fvs, free vars of the target expresion,
482 -- whose level is less than than the supplied level
483 -- These are the ones we are going to abstract out
484 abstractVars dest_lvl env fvs
485 = uniq (sortLt lt [var | fv <- varSetElems fvs, var <- absVarsOf dest_lvl env fv])
487 -- Sort the variables so we don't get
488 -- mixed-up tyvars and Ids; it's just messy
489 v1 `lt` v2 = case (isId v1, isId v2) of
490 (True, False) -> False
491 (False, True) -> True
492 other -> v1 < v2 -- Same family
493 uniq :: [Var] -> [Var]
494 -- Remove adjacent duplicates; the sort will have brought them together
495 uniq (v1:v2:vs) | v1 == v2 = uniq (v2:vs)
496 | otherwise = v1 : uniq (v2:vs)
499 -- Destintion level is the max Id level of the expression
500 -- (We'll abstract the type variables, if any.)
501 destLevel :: LevelEnv -> VarSet -> Bool -> Level
502 destLevel env fvs is_function
504 && is_function = tOP_LEVEL -- Send functions to top level; see
505 -- the comments with isFunction
506 | otherwise = maxIdLevel env fvs
508 isFunction :: CoreExprWithFVs -> Bool
509 -- The idea here is that we want to float *functions* to
510 -- the top level. This saves no work, but
511 -- (a) it can make the host function body a lot smaller,
512 -- and hence inlinable.
513 -- (b) it can also save allocation when the function is recursive:
514 -- h = \x -> letrec f = \y -> ...f...y...x...
517 -- f = \x y -> ...(f x)...y...x...
519 -- No allocation for f now.
520 -- We may only want to do this if there are sufficiently few free
521 -- variables. We certainly only want to do it for values, and not for
522 -- constructors. So the simple thing is just to look for lambdas
523 isFunction (_, AnnLam b e) | isId b = True
524 | otherwise = isFunction e
525 isFunction (_, AnnNote n e) = isFunction e
526 isFunction other = False
530 %************************************************************************
532 \subsection{Free-To-Level Monad}
534 %************************************************************************
537 type LevelEnv = (Bool, -- True <=> Float lambdas too
538 VarEnv Level, -- Domain is *post-cloned* TyVars and Ids
539 Subst, -- Domain is pre-cloned Ids; tracks the in-scope set
540 -- so that subtitution is capture-avoiding
541 IdEnv ([Var], LevelledExpr)) -- Domain is pre-cloned Ids
542 -- We clone let-bound variables so that they are still
543 -- distinct when floated out; hence the SubstEnv/IdEnv.
544 -- (see point 3 of the module overview comment).
545 -- We also use these envs when making a variable polymorphic
546 -- because we want to float it out past a big lambda.
548 -- The SubstEnv and IdEnv always implement the same mapping, but the
549 -- SubstEnv maps to CoreExpr and the IdEnv to LevelledExpr
550 -- Since the range is always a variable or type application,
551 -- there is never any difference between the two, but sadly
552 -- the types differ. The SubstEnv is used when substituting in
553 -- a variable's IdInfo; the IdEnv when we find a Var.
555 -- In addition the IdEnv records a list of tyvars free in the
556 -- type application, just so we don't have to call freeVars on
557 -- the type application repeatedly.
559 -- The domain of the both envs is *pre-cloned* Ids, though
561 -- The domain of the VarEnv Level is the *post-cloned* Ids
563 initialEnv :: Bool -> LevelEnv
564 initialEnv float_lams = (float_lams, emptyVarEnv, emptySubst, emptyVarEnv)
566 floatLams :: LevelEnv -> Bool
567 floatLams (float_lams, _, _, _) = float_lams
569 extendLvlEnv :: LevelEnv -> [(Var,Level)] -> LevelEnv
570 -- Used when *not* cloning
571 extendLvlEnv (float_lams, lvl_env, subst, id_env) prs
573 foldl add_lvl lvl_env prs,
574 foldl del_subst subst prs,
575 foldl del_id id_env prs)
577 add_lvl env (v,l) = extendVarEnv env v l
578 del_subst env (v,_) = extendInScope env v
579 del_id env (v,_) = delVarEnv env v
580 -- We must remove any clone for this variable name in case of
581 -- shadowing. This bit me in the following case
582 -- (in nofib/real/gg/Spark.hs):
585 -- ... -> case e of wild {
586 -- ... -> ... wild ...
590 -- The inside occurrence of @wild@ was being replaced with @ds@,
591 -- incorrectly, because the SubstEnv was still lying around. Ouch!
594 -- extendCaseBndrLvlEnv adds the mapping case-bndr->scrut-var if it can
595 -- (see point 4 of the module overview comment)
596 extendCaseBndrLvlEnv env scrut case_bndr lvl
598 Var v -> extendCloneLvlEnv lvl env [(case_bndr, v)]
599 other -> extendLvlEnv env [(case_bndr,lvl)]
601 extendPolyLvlEnv dest_lvl (float_lams, lvl_env, subst, id_env) abs_vars bndr_pairs
603 foldl add_lvl lvl_env bndr_pairs,
604 foldl add_subst subst bndr_pairs,
605 foldl add_id id_env bndr_pairs)
607 add_lvl env (v,v') = extendVarEnv env v' dest_lvl
608 add_subst env (v,v') = extendSubst env v (DoneEx (mkVarApps (Var v') abs_vars))
609 add_id env (v,v') = extendVarEnv env v ((v':abs_vars), mkVarApps (Var v') abs_vars)
611 extendCloneLvlEnv lvl (float_lams, lvl_env, subst, id_env) bndr_pairs
613 foldl add_lvl lvl_env bndr_pairs,
614 foldl add_subst subst bndr_pairs,
615 foldl add_id id_env bndr_pairs)
617 add_lvl env (v,v') = extendVarEnv env v' lvl
618 add_subst env (v,v') = extendSubst env v (DoneEx (Var v'))
619 add_id env (v,v') = extendVarEnv env v ([v'], Var v')
622 maxIdLevel :: LevelEnv -> VarSet -> Level
623 maxIdLevel (_, lvl_env,_,id_env) var_set
624 = foldVarSet max_in tOP_LEVEL var_set
626 max_in in_var lvl = foldr max_out lvl (case lookupVarEnv id_env in_var of
627 Just (abs_vars, _) -> abs_vars
631 | isId out_var = case lookupVarEnv lvl_env out_var of
632 Just lvl' -> maxLvl lvl' lvl
634 | otherwise = lvl -- Ignore tyvars in *maxIdLevel*
636 lookupVar :: LevelEnv -> Id -> LevelledExpr
637 lookupVar (_, _, _, id_env) v = case lookupVarEnv id_env v of
638 Just (_, expr) -> expr
641 absVarsOf :: Level -> LevelEnv -> Var -> [Var]
642 -- If f is free in the exression, and f maps to poly_f a b c in the
643 -- current substitution, then we must report a b c as candidate type
645 absVarsOf dest_lvl (_, lvl_env, _, id_env) v
647 = [final_av | av <- lookup_avs v, abstract_me av, final_av <- add_tyvars av]
650 = if abstract_me v then [v] else []
653 abstract_me v = case lookupVarEnv lvl_env v of
654 Just lvl -> dest_lvl `ltLvl` lvl
657 lookup_avs v = case lookupVarEnv id_env v of
658 Just (abs_vars, _) -> abs_vars
661 -- We are going to lambda-abstract, so nuke any IdInfo,
662 -- and add the tyvars of the Id
663 add_tyvars v | isId v = zap v : varSetElems (idFreeTyVars v)
666 zap v = WARN( workerExists (idWorkerInfo v)
667 || not (isEmptyCoreRules (idSpecialisation v)),
668 text "absVarsOf: discarding info on" <+> ppr v )
669 setIdInfo v vanillaIdInfo
673 type LvlM result = UniqSM result
682 newPolyBndrs dest_lvl env abs_vars bndrs
683 = getUniquesUs (length bndrs) `thenLvl` \ uniqs ->
685 new_bndrs = zipWith mk_poly_bndr bndrs uniqs
687 returnLvl (extendPolyLvlEnv dest_lvl env abs_vars (bndrs `zip` new_bndrs), new_bndrs)
689 mk_poly_bndr bndr uniq = mkSysLocal (_PK_ str) uniq poly_ty
691 str = "poly_" ++ occNameUserString (getOccName bndr)
692 poly_ty = foldr mkPiType (idType bndr) abs_vars
696 -> [CoreBndr] -> Type -- Abstract wrt these bndrs
698 newLvlVar str vars body_ty
699 = getUniqueUs `thenLvl` \ uniq ->
700 returnUs (mkSysLocal (_PK_ str) uniq (foldr mkPiType body_ty vars))
702 -- The deeply tiresome thing is that we have to apply the substitution
703 -- to the rules inside each Id. Grr. But it matters.
705 cloneVar :: TopLevelFlag -> LevelEnv -> Id -> Level -> Level -> LvlM (LevelEnv, Id)
706 cloneVar TopLevel env v ctxt_lvl dest_lvl
707 = returnUs (env, v) -- Don't clone top level things
708 cloneVar NotTopLevel env v ctxt_lvl dest_lvl
710 getUniqueUs `thenLvl` \ uniq ->
712 v' = setVarUnique v uniq
713 v'' = subst_id_info env ctxt_lvl dest_lvl v'
714 env' = extendCloneLvlEnv dest_lvl env [(v,v'')]
718 cloneVars :: TopLevelFlag -> LevelEnv -> [Id] -> Level -> Level -> LvlM (LevelEnv, [Id])
719 cloneVars TopLevel env vs ctxt_lvl dest_lvl
720 = returnUs (env, vs) -- Don't clone top level things
721 cloneVars NotTopLevel env vs ctxt_lvl dest_lvl
722 = ASSERT( all isId vs )
723 getUniquesUs (length vs) `thenLvl` \ uniqs ->
725 vs' = zipWith setVarUnique vs uniqs
726 vs'' = map (subst_id_info env' ctxt_lvl dest_lvl) vs'
727 env' = extendCloneLvlEnv dest_lvl env (vs `zip` vs'')
729 returnUs (env', vs'')
731 subst_id_info (_, _, subst, _) ctxt_lvl dest_lvl v
732 = modifyIdInfo (\info -> substIdInfo subst info (zap_dmd info)) v
734 -- VERY IMPORTANT: we must zap the demand info
735 -- if the thing is going to float out past a lambda
737 | float_past_lam && isStrict (demandInfo info)
738 = setDemandInfo info wwLazy
742 float_past_lam = ctxt_lvl `ltMajLvl` dest_lvl