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, zapDemandIdInfo,
61 idSpecialisation, idWorkerInfo, setIdInfo
63 import IdInfo ( workerExists, vanillaIdInfo, )
67 import Name ( getOccName )
68 import OccName ( occNameUserString )
69 import Type ( isUnLiftedType, Type )
70 import BasicTypes ( TopLevelFlag(..) )
72 import Util ( sortLt, isSingleton, count )
76 %************************************************************************
78 \subsection{Level numbers}
80 %************************************************************************
83 data Level = Level Int -- Level number of enclosing lambdas
84 Int -- Number of big-lambda and/or case expressions between
85 -- here and the nearest enclosing lambda
88 The {\em level number} on a (type-)lambda-bound variable is the
89 nesting depth of the (type-)lambda which binds it. The outermost lambda
90 has level 1, so (Level 0 0) means that the variable is bound outside any lambda.
92 On an expression, it's the maximum level number of its free
93 (type-)variables. On a let(rec)-bound variable, it's the level of its
94 RHS. On a case-bound variable, it's the number of enclosing lambdas.
96 Top-level variables: level~0. Those bound on the RHS of a top-level
97 definition but ``before'' a lambda; e.g., the \tr{x} in (levels shown
100 a_0 = let b_? = ... in
101 x_1 = ... b ... in ...
104 The main function @lvlExpr@ carries a ``context level'' (@ctxt_lvl@).
105 That's meant to be the level number of the enclosing binder in the
106 final (floated) program. If the level number of a sub-expression is
107 less than that of the context, then it might be worth let-binding the
108 sub-expression so that it will indeed float. This context level starts
112 type LevelledExpr = TaggedExpr Level
113 type LevelledBind = TaggedBind Level
115 tOP_LEVEL = Level 0 0
117 incMajorLvl :: Level -> Level
118 incMajorLvl (Level major minor) = Level (major+1) 0
120 incMinorLvl :: Level -> Level
121 incMinorLvl (Level major minor) = Level major (minor+1)
123 maxLvl :: Level -> Level -> Level
124 maxLvl l1@(Level maj1 min1) l2@(Level maj2 min2)
125 | (maj1 > maj2) || (maj1 == maj2 && min1 > min2) = l1
128 ltLvl :: Level -> Level -> Bool
129 ltLvl (Level maj1 min1) (Level maj2 min2)
130 = (maj1 < maj2) || (maj1 == maj2 && min1 < min2)
132 ltMajLvl :: Level -> Level -> Bool
133 -- Tells if one level belongs to a difft *lambda* level to another
134 ltMajLvl (Level maj1 _) (Level maj2 _) = maj1 < maj2
136 isTopLvl :: Level -> Bool
137 isTopLvl (Level 0 0) = True
138 isTopLvl other = False
140 instance Outputable Level where
141 ppr (Level maj min) = hcat [ char '<', int maj, char ',', int min, char '>' ]
143 instance Eq Level where
144 (Level maj1 min1) == (Level maj2 min2) = maj1==maj2 && min1==min2
147 %************************************************************************
149 \subsection{Main level-setting code}
151 %************************************************************************
154 setLevels :: Bool -- True <=> float lambdas to top level
159 setLevels float_lams binds us
160 = initLvl us (do_them binds)
162 -- "do_them"'s main business is to thread the monad along
163 -- It gives each top binding the same empty envt, because
164 -- things unbound in the envt have level number zero implicitly
165 do_them :: [CoreBind] -> LvlM [LevelledBind]
167 do_them [] = returnLvl []
169 = lvlTopBind init_env b `thenLvl` \ (lvld_bind, _) ->
170 do_them bs `thenLvl` \ lvld_binds ->
171 returnLvl (lvld_bind : lvld_binds)
173 init_env = initialEnv float_lams
175 lvlTopBind env (NonRec binder rhs)
176 = lvlBind TopLevel tOP_LEVEL env (AnnNonRec binder (freeVars rhs))
177 -- Rhs can have no free vars!
179 lvlTopBind env (Rec pairs)
180 = lvlBind TopLevel tOP_LEVEL env (AnnRec [(b,freeVars rhs) | (b,rhs) <- pairs])
183 %************************************************************************
185 \subsection{Setting expression levels}
187 %************************************************************************
190 lvlExpr :: Level -- ctxt_lvl: Level of enclosing expression
191 -> LevelEnv -- Level of in-scope names/tyvars
192 -> CoreExprWithFVs -- input expression
193 -> LvlM LevelledExpr -- Result expression
196 The @ctxt_lvl@ is, roughly, the level of the innermost enclosing
197 binder. Here's an example
199 v = \x -> ...\y -> let r = case (..x..) of
203 When looking at the rhs of @r@, @ctxt_lvl@ will be 1 because that's
204 the level of @r@, even though it's inside a level-2 @\y@. It's
205 important that @ctxt_lvl@ is 1 and not 2 in @r@'s rhs, because we
206 don't want @lvlExpr@ to turn the scrutinee of the @case@ into an MFE
207 --- because it isn't a *maximal* free expression.
209 If there were another lambda in @r@'s rhs, it would get level-2 as well.
212 lvlExpr _ _ (_, AnnType ty) = returnLvl (Type ty)
213 lvlExpr _ env (_, AnnVar v) = returnLvl (lookupVar env v)
214 lvlExpr _ env (_, AnnLit lit) = returnLvl (Lit lit)
216 lvlExpr ctxt_lvl env (_, AnnApp fun arg)
217 = lvl_fun fun `thenLvl` \ fun' ->
218 lvlMFE False ctxt_lvl env arg `thenLvl` \ arg' ->
219 returnLvl (App fun' arg')
221 lvl_fun (_, AnnCase _ _ _) = lvlMFE True ctxt_lvl env fun
222 lvl_fun other = lvlExpr ctxt_lvl env fun
223 -- We don't do MFE on partial applications generally,
224 -- but we do if the function is big and hairy, like a case
226 lvlExpr ctxt_lvl env (_, AnnNote InlineMe expr)
227 -- Don't float anything out of an InlineMe; hence the tOP_LEVEL
228 = lvlExpr tOP_LEVEL env expr `thenLvl` \ expr' ->
229 returnLvl (Note InlineMe expr')
231 lvlExpr ctxt_lvl env (_, AnnNote note expr)
232 = lvlExpr ctxt_lvl env expr `thenLvl` \ expr' ->
233 returnLvl (Note note expr')
235 -- We don't split adjacent lambdas. That is, given
237 -- we don't float to give
238 -- \x -> let v = x+y in \y -> (v,y)
239 -- Why not? Because partial applications are fairly rare, and splitting
240 -- lambdas makes them more expensive.
242 lvlExpr ctxt_lvl env expr@(_, AnnLam bndr rhs)
243 = lvlMFE True new_lvl new_env body `thenLvl` \ new_body ->
244 returnLvl (glue_binders new_bndrs expr new_body)
246 (bndrs, body) = collect_binders expr
247 (new_lvl, new_bndrs) = lvlLamBndrs ctxt_lvl bndrs
248 new_env = extendLvlEnv env new_bndrs
250 lvlExpr ctxt_lvl env (_, AnnLet bind body)
251 = lvlBind NotTopLevel ctxt_lvl env bind `thenLvl` \ (bind', new_env) ->
252 lvlExpr ctxt_lvl new_env body `thenLvl` \ body' ->
253 returnLvl (Let bind' body')
255 lvlExpr ctxt_lvl env (_, AnnCase expr case_bndr alts)
256 = lvlMFE True ctxt_lvl env expr `thenLvl` \ expr' ->
258 alts_env = extendCaseBndrLvlEnv env expr' case_bndr incd_lvl
260 mapLvl (lvl_alt alts_env) alts `thenLvl` \ alts' ->
261 returnLvl (Case expr' (case_bndr, incd_lvl) alts')
263 incd_lvl = incMinorLvl ctxt_lvl
265 lvl_alt alts_env (con, bs, rhs)
266 = lvlMFE True incd_lvl new_env rhs `thenLvl` \ rhs' ->
267 returnLvl (con, bs', rhs')
269 bs' = [ (b, incd_lvl) | b <- bs ]
270 new_env = extendLvlEnv alts_env bs'
275 go rev_bndrs (_, AnnLam b e) = go (b:rev_bndrs) e
276 go rev_bndrs (_, AnnNote n e) = go rev_bndrs e
277 go rev_bndrs rhs = (reverse rev_bndrs, rhs)
278 -- Ignore notes, because we don't want to split
279 -- a lambda like this (\x -> coerce t (\s -> ...))
280 -- This happens quite a bit in state-transformer programs
282 -- glue_binders puts the lambda back together
283 glue_binders (b:bs) (_, AnnLam _ e) body = Lam b (glue_binders bs e body)
284 glue_binders bs (_, AnnNote n e) body = Note n (glue_binders bs e body)
285 glue_binders [] e body = body
288 @lvlMFE@ is just like @lvlExpr@, except that it might let-bind
289 the expression, so that it can itself be floated.
292 lvlMFE :: Bool -- True <=> strict context [body of case or let]
293 -> Level -- Level of innermost enclosing lambda/tylam
294 -> LevelEnv -- Level of in-scope names/tyvars
295 -> CoreExprWithFVs -- input expression
296 -> LvlM LevelledExpr -- Result expression
298 lvlMFE strict_ctxt ctxt_lvl env (_, AnnType ty)
299 = returnLvl (Type ty)
301 lvlMFE strict_ctxt ctxt_lvl env ann_expr@(fvs, _)
302 | isUnLiftedType ty -- Can't let-bind it
303 || not good_destination
304 || exprIsTrivial expr -- Is trivial
305 || (strict_ctxt && exprIsBottom expr) -- Strict context and is bottom
306 -- e.g. \x -> error "foo"
307 -- No gain from floating this
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 dest_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 = cloneRecVars 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 (float_lams, lvl_env, subst, id_env) (Var scrut_var) case_bndr lvl
598 extendVarEnv lvl_env case_bndr lvl,
599 extendSubst subst case_bndr (DoneEx (Var scrut_var)),
600 extendVarEnv id_env case_bndr ([scrut_var], Var scrut_var))
602 extendCaseBndrLvlEnv env scrut case_bndr lvl
603 = extendLvlEnv env [(case_bndr,lvl)]
605 extendPolyLvlEnv dest_lvl (float_lams, lvl_env, subst, id_env) abs_vars bndr_pairs
607 foldl add_lvl lvl_env bndr_pairs,
608 foldl add_subst subst bndr_pairs,
609 foldl add_id id_env bndr_pairs)
611 add_lvl env (v,v') = extendVarEnv env v' dest_lvl
612 add_subst env (v,v') = extendSubst env v (DoneEx (mkVarApps (Var v') abs_vars))
613 add_id env (v,v') = extendVarEnv env v ((v':abs_vars), mkVarApps (Var v') abs_vars)
615 extendCloneLvlEnv lvl (float_lams, lvl_env, _, id_env) new_subst bndr_pairs
617 foldl add_lvl lvl_env bndr_pairs,
619 foldl add_id id_env bndr_pairs)
621 add_lvl env (v,v') = extendVarEnv env v' lvl
622 add_id env (v,v') = extendVarEnv env v ([v'], Var v')
625 maxIdLevel :: LevelEnv -> VarSet -> Level
626 maxIdLevel (_, lvl_env,_,id_env) var_set
627 = foldVarSet max_in tOP_LEVEL var_set
629 max_in in_var lvl = foldr max_out lvl (case lookupVarEnv id_env in_var of
630 Just (abs_vars, _) -> abs_vars
634 | isId out_var = case lookupVarEnv lvl_env out_var of
635 Just lvl' -> maxLvl lvl' lvl
637 | otherwise = lvl -- Ignore tyvars in *maxIdLevel*
639 lookupVar :: LevelEnv -> Id -> LevelledExpr
640 lookupVar (_, _, _, id_env) v = case lookupVarEnv id_env v of
641 Just (_, expr) -> expr
644 absVarsOf :: Level -> LevelEnv -> Var -> [Var]
645 -- If f is free in the exression, and f maps to poly_f a b c in the
646 -- current substitution, then we must report a b c as candidate type
648 absVarsOf dest_lvl (_, lvl_env, _, id_env) v
650 = [final_av | av <- lookup_avs v, abstract_me av, final_av <- add_tyvars av]
653 = if abstract_me v then [v] else []
656 abstract_me v = case lookupVarEnv lvl_env v of
657 Just lvl -> dest_lvl `ltLvl` lvl
660 lookup_avs v = case lookupVarEnv id_env v of
661 Just (abs_vars, _) -> abs_vars
664 -- We are going to lambda-abstract, so nuke any IdInfo,
665 -- and add the tyvars of the Id
666 add_tyvars v | isId v = zap v : varSetElems (idFreeTyVars v)
669 zap v = WARN( workerExists (idWorkerInfo v)
670 || not (isEmptyCoreRules (idSpecialisation v)),
671 text "absVarsOf: discarding info on" <+> ppr v )
672 setIdInfo v vanillaIdInfo
676 type LvlM result = UniqSM result
685 newPolyBndrs dest_lvl env abs_vars bndrs
686 = getUniquesUs (length bndrs) `thenLvl` \ uniqs ->
688 new_bndrs = zipWith mk_poly_bndr bndrs uniqs
690 returnLvl (extendPolyLvlEnv dest_lvl env abs_vars (bndrs `zip` new_bndrs), new_bndrs)
692 mk_poly_bndr bndr uniq = mkSysLocal (_PK_ str) uniq poly_ty
694 str = "poly_" ++ occNameUserString (getOccName bndr)
695 poly_ty = foldr mkPiType (idType bndr) abs_vars
699 -> [CoreBndr] -> Type -- Abstract wrt these bndrs
701 newLvlVar str vars body_ty
702 = getUniqueUs `thenLvl` \ uniq ->
703 returnUs (mkSysLocal (_PK_ str) uniq (foldr mkPiType body_ty vars))
705 -- The deeply tiresome thing is that we have to apply the substitution
706 -- to the rules inside each Id. Grr. But it matters.
708 cloneVar :: TopLevelFlag -> LevelEnv -> Id -> Level -> Level -> LvlM (LevelEnv, Id)
709 cloneVar TopLevel env v ctxt_lvl dest_lvl
710 = returnUs (env, v) -- Don't clone top level things
711 cloneVar NotTopLevel env@(_,_,subst,_) v ctxt_lvl dest_lvl
713 getUs `thenLvl` \ us ->
715 (subst', v1) = substAndCloneId subst us v
716 v2 = zap_demand ctxt_lvl dest_lvl v1
717 env' = extendCloneLvlEnv dest_lvl env subst' [(v,v2)]
721 cloneRecVars :: TopLevelFlag -> LevelEnv -> [Id] -> Level -> Level -> LvlM (LevelEnv, [Id])
722 cloneRecVars TopLevel env vs ctxt_lvl dest_lvl
723 = returnUs (env, vs) -- Don't clone top level things
724 cloneRecVars NotTopLevel env@(_,_,subst,_) vs ctxt_lvl dest_lvl
725 = ASSERT( all isId vs )
726 getUs `thenLvl` \ us ->
728 (subst', vs1) = substAndCloneRecIds subst us vs
729 vs2 = map (zap_demand ctxt_lvl dest_lvl) vs1
730 env' = extendCloneLvlEnv dest_lvl env subst' (vs `zip` vs2)
734 -- VERY IMPORTANT: we must zap the demand info
735 -- if the thing is going to float out past a lambda
736 zap_demand dest_lvl ctxt_lvl id
737 | ctxt_lvl == dest_lvl = id -- Stays put
738 | otherwise = zapDemandIdInfo id -- Floats out