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, isInlineCtxt
53 #include "HsVersions.h"
57 import CoreUtils ( exprType, exprIsTrivial, exprIsBottom, mkPiTypes )
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 = InlineCtxt -- A level that's used only for
84 -- the context parameter ctxt_lvl
85 | Level Int -- Level number of enclosing lambdas
86 Int -- Number of big-lambda and/or case expressions between
87 -- here and the nearest enclosing lambda
90 The {\em level number} on a (type-)lambda-bound variable is the
91 nesting depth of the (type-)lambda which binds it. The outermost lambda
92 has level 1, so (Level 0 0) means that the variable is bound outside any lambda.
94 On an expression, it's the maximum level number of its free
95 (type-)variables. On a let(rec)-bound variable, it's the level of its
96 RHS. On a case-bound variable, it's the number of enclosing lambdas.
98 Top-level variables: level~0. Those bound on the RHS of a top-level
99 definition but ``before'' a lambda; e.g., the \tr{x} in (levels shown
100 as ``subscripts'')...
102 a_0 = let b_? = ... in
103 x_1 = ... b ... in ...
106 The main function @lvlExpr@ carries a ``context level'' (@ctxt_lvl@).
107 That's meant to be the level number of the enclosing binder in the
108 final (floated) program. If the level number of a sub-expression is
109 less than that of the context, then it might be worth let-binding the
110 sub-expression so that it will indeed float.
112 If you can float to level @Level 0 0@ worth doing so because then your
113 allocation becomes static instead of dynamic. We always start with
119 @InlineCtxt@ very similar to @Level 0 0@, but is used for one purpose:
120 to say "don't float anything out of here". That's exactly what we
121 want for the body of an INLINE, where we don't want to float anything
122 out at all. See notes with lvlMFE below.
126 -- At one time I tried the effect of not float anything out of an InlineMe,
127 -- but it sometimes works badly. For example, consider PrelArr.done. It
128 -- has the form __inline (\d. e)
129 -- where e doesn't mention d. If we float this to
130 -- __inline (let x = e in \d. x)
131 -- things are bad. The inliner doesn't even inline it because it doesn't look
132 -- like a head-normal form. So it seems a lesser evil to let things float.
133 -- In SetLevels we do set the context to (Level 0 0) when we get to an InlineMe
134 -- which discourages floating out.
136 So the conclusion is: don't do any floating at all inside an InlineMe.
137 (In the above example, don't float the {x=e} out of the \d.)
139 One particular case is that of workers: we don't want to float the
140 call to the worker outside the wrapper, otherwise the worker might get
141 inlined into the floated expression, and an importing module won't see
145 type LevelledExpr = TaggedExpr Level
146 type LevelledBind = TaggedBind Level
148 tOP_LEVEL = Level 0 0
149 iNLINE_CTXT = InlineCtxt
151 incMajorLvl :: Level -> Level
152 -- For InlineCtxt we ignore any inc's; we don't want
153 -- to do any floating at all; see notes above
154 incMajorLvl InlineCtxt = InlineCtxt
155 incMajorLvl (Level major minor) = Level (major+1) 0
157 incMinorLvl :: Level -> Level
158 incMinorLvl InlineCtxt = InlineCtxt
159 incMinorLvl (Level major minor) = Level major (minor+1)
161 maxLvl :: Level -> Level -> Level
162 maxLvl InlineCtxt l2 = l2
163 maxLvl l1 InlineCtxt = l1
164 maxLvl l1@(Level maj1 min1) l2@(Level maj2 min2)
165 | (maj1 > maj2) || (maj1 == maj2 && min1 > min2) = l1
168 ltLvl :: Level -> Level -> Bool
169 ltLvl any_lvl InlineCtxt = False
170 ltLvl InlineCtxt (Level _ _) = True
171 ltLvl (Level maj1 min1) (Level maj2 min2)
172 = (maj1 < maj2) || (maj1 == maj2 && min1 < min2)
174 ltMajLvl :: Level -> Level -> Bool
175 -- Tells if one level belongs to a difft *lambda* level to another
176 ltMajLvl any_lvl InlineCtxt = False
177 ltMajLvl InlineCtxt (Level maj2 _) = 0 < maj2
178 ltMajLvl (Level maj1 _) (Level maj2 _) = maj1 < maj2
180 isTopLvl :: Level -> Bool
181 isTopLvl (Level 0 0) = True
182 isTopLvl other = False
184 isInlineCtxt :: Level -> Bool
185 isInlineCtxt InlineCtxt = True
186 isInlineCtxt other = False
188 instance Outputable Level where
189 ppr InlineCtxt = text "<INLINE>"
190 ppr (Level maj min) = hcat [ char '<', int maj, char ',', int min, char '>' ]
192 instance Eq Level where
193 InlineCtxt == InlineCtxt = True
194 (Level maj1 min1) == (Level maj2 min2) = maj1==maj2 && min1==min2
199 %************************************************************************
201 \subsection{Main level-setting code}
203 %************************************************************************
206 setLevels :: Bool -- True <=> float lambdas to top level
211 setLevels float_lams binds us
212 = initLvl us (do_them binds)
214 -- "do_them"'s main business is to thread the monad along
215 -- It gives each top binding the same empty envt, because
216 -- things unbound in the envt have level number zero implicitly
217 do_them :: [CoreBind] -> LvlM [LevelledBind]
219 do_them [] = returnLvl []
221 = lvlTopBind init_env b `thenLvl` \ (lvld_bind, _) ->
222 do_them bs `thenLvl` \ lvld_binds ->
223 returnLvl (lvld_bind : lvld_binds)
225 init_env = initialEnv float_lams
227 lvlTopBind env (NonRec binder rhs)
228 = lvlBind TopLevel tOP_LEVEL env (AnnNonRec binder (freeVars rhs))
229 -- Rhs can have no free vars!
231 lvlTopBind env (Rec pairs)
232 = lvlBind TopLevel tOP_LEVEL env (AnnRec [(b,freeVars rhs) | (b,rhs) <- pairs])
235 %************************************************************************
237 \subsection{Setting expression levels}
239 %************************************************************************
242 lvlExpr :: Level -- ctxt_lvl: Level of enclosing expression
243 -> LevelEnv -- Level of in-scope names/tyvars
244 -> CoreExprWithFVs -- input expression
245 -> LvlM LevelledExpr -- Result expression
248 The @ctxt_lvl@ is, roughly, the level of the innermost enclosing
249 binder. Here's an example
251 v = \x -> ...\y -> let r = case (..x..) of
255 When looking at the rhs of @r@, @ctxt_lvl@ will be 1 because that's
256 the level of @r@, even though it's inside a level-2 @\y@. It's
257 important that @ctxt_lvl@ is 1 and not 2 in @r@'s rhs, because we
258 don't want @lvlExpr@ to turn the scrutinee of the @case@ into an MFE
259 --- because it isn't a *maximal* free expression.
261 If there were another lambda in @r@'s rhs, it would get level-2 as well.
264 lvlExpr _ _ (_, AnnType ty) = returnLvl (Type ty)
265 lvlExpr _ env (_, AnnVar v) = returnLvl (lookupVar env v)
266 lvlExpr _ env (_, AnnLit lit) = returnLvl (Lit lit)
268 lvlExpr ctxt_lvl env (_, AnnApp fun arg)
269 = lvl_fun fun `thenLvl` \ fun' ->
270 lvlMFE False ctxt_lvl env arg `thenLvl` \ arg' ->
271 returnLvl (App fun' arg')
273 lvl_fun (_, AnnCase _ _ _) = lvlMFE True ctxt_lvl env fun
274 lvl_fun other = lvlExpr ctxt_lvl env fun
275 -- We don't do MFE on partial applications generally,
276 -- but we do if the function is big and hairy, like a case
278 lvlExpr ctxt_lvl env (_, AnnNote InlineMe expr)
279 -- Don't float anything out of an InlineMe; hence the iNLINE_CTXT
280 = lvlExpr iNLINE_CTXT env expr `thenLvl` \ expr' ->
281 returnLvl (Note InlineMe expr')
283 lvlExpr ctxt_lvl env (_, AnnNote note expr)
284 = lvlExpr ctxt_lvl env expr `thenLvl` \ expr' ->
285 returnLvl (Note note expr')
287 -- We don't split adjacent lambdas. That is, given
289 -- we don't float to give
290 -- \x -> let v = x+y in \y -> (v,y)
291 -- Why not? Because partial applications are fairly rare, and splitting
292 -- lambdas makes them more expensive.
294 lvlExpr ctxt_lvl env expr@(_, AnnLam bndr rhs)
295 = lvlMFE True new_lvl new_env body `thenLvl` \ new_body ->
296 returnLvl (mkLams new_bndrs new_body)
298 (bndrs, body) = collectAnnBndrs expr
299 (new_lvl, new_bndrs) = lvlLamBndrs ctxt_lvl bndrs
300 new_env = extendLvlEnv env new_bndrs
301 -- At one time we called a special verion of collectBinders,
302 -- which ignored coercions, because we don't want to split
303 -- a lambda like this (\x -> coerce t (\s -> ...))
304 -- This used to happen quite a bit in state-transformer programs,
305 -- but not nearly so much now non-recursive newtypes are transparent.
306 -- [See SetLevels rev 1.50 for a version with this approach.]
308 lvlExpr ctxt_lvl env (_, AnnLet bind body)
309 = lvlBind NotTopLevel ctxt_lvl env bind `thenLvl` \ (bind', new_env) ->
310 lvlExpr ctxt_lvl new_env body `thenLvl` \ body' ->
311 returnLvl (Let bind' body')
313 lvlExpr ctxt_lvl env (_, AnnCase expr case_bndr alts)
314 = lvlMFE True ctxt_lvl env expr `thenLvl` \ expr' ->
316 alts_env = extendCaseBndrLvlEnv env expr' case_bndr incd_lvl
318 mapLvl (lvl_alt alts_env) alts `thenLvl` \ alts' ->
319 returnLvl (Case expr' (case_bndr, incd_lvl) alts')
321 incd_lvl = incMinorLvl ctxt_lvl
323 lvl_alt alts_env (con, bs, rhs)
324 = lvlMFE True incd_lvl new_env rhs `thenLvl` \ rhs' ->
325 returnLvl (con, bs', rhs')
327 bs' = [ (b, incd_lvl) | b <- bs ]
328 new_env = extendLvlEnv alts_env bs'
331 @lvlMFE@ is just like @lvlExpr@, except that it might let-bind
332 the expression, so that it can itself be floated.
335 lvlMFE :: Bool -- True <=> strict context [body of case or let]
336 -> Level -- Level of innermost enclosing lambda/tylam
337 -> LevelEnv -- Level of in-scope names/tyvars
338 -> CoreExprWithFVs -- input expression
339 -> LvlM LevelledExpr -- Result expression
341 lvlMFE strict_ctxt ctxt_lvl env (_, AnnType ty)
342 = returnLvl (Type ty)
344 lvlMFE strict_ctxt ctxt_lvl env ann_expr@(fvs, _)
345 | isUnLiftedType ty -- Can't let-bind it
346 || isInlineCtxt ctxt_lvl -- Don't float out of an __inline__ context
347 || not good_destination
348 || exprIsTrivial expr -- Is trivial
349 || (strict_ctxt && exprIsBottom expr) -- Strict context and is bottom
350 -- e.g. \x -> error "foo"
351 -- No gain from floating this
352 = -- Don't float it out
353 lvlExpr ctxt_lvl env ann_expr
355 | otherwise -- Float it out!
356 = lvlFloatRhs abs_vars dest_lvl env ann_expr `thenLvl` \ expr' ->
357 newLvlVar "lvl" abs_vars ty `thenLvl` \ var ->
358 returnLvl (Let (NonRec (var,dest_lvl) expr')
359 (mkVarApps (Var var) abs_vars))
361 expr = deAnnotate ann_expr
363 dest_lvl = destLevel env fvs (isFunction ann_expr)
364 abs_vars = abstractVars dest_lvl env fvs
366 good_destination = dest_lvl `ltMajLvl` ctxt_lvl -- Escapes a value lambda
367 || (isTopLvl dest_lvl -- Goes to the top
368 && not strict_ctxt) -- or from a strict context
369 -- A decision to float entails let-binding this thing, and we only do
370 -- that if we'll escape a value lambda, or will go to the top level.
373 -- concat = /\ a -> foldr ..a.. (++) []
374 -- was getting turned into
375 -- concat = /\ a -> lvl a
376 -- lvl = /\ a -> foldr ..a.. (++) []
377 -- which is pretty stupid. Hence the strict_ctxt test
381 %************************************************************************
383 \subsection{Bindings}
385 %************************************************************************
387 The binding stuff works for top level too.
390 lvlBind :: TopLevelFlag -- Used solely to decide whether to clone
391 -> Level -- Context level; might be Top even for bindings nested in the RHS
392 -- of a top level binding
395 -> LvlM (LevelledBind, LevelEnv)
397 lvlBind top_lvl ctxt_lvl env (AnnNonRec bndr rhs@(rhs_fvs,_))
398 | isInlineCtxt ctxt_lvl -- Don't do anything inside InlineMe
399 = lvlExpr ctxt_lvl env rhs `thenLvl` \ rhs' ->
400 returnLvl (NonRec (bndr, ctxt_lvl) rhs', env)
403 = -- No type abstraction; clone existing binder
404 lvlExpr dest_lvl env rhs `thenLvl` \ rhs' ->
405 cloneVar top_lvl env bndr ctxt_lvl dest_lvl `thenLvl` \ (env', bndr') ->
406 returnLvl (NonRec (bndr', dest_lvl) rhs', env')
409 = -- Yes, type abstraction; create a new binder, extend substitution, etc
410 lvlFloatRhs abs_vars dest_lvl env rhs `thenLvl` \ rhs' ->
411 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (env', [bndr']) ->
412 returnLvl (NonRec (bndr', dest_lvl) rhs', env')
415 bind_fvs = rhs_fvs `unionVarSet` idFreeVars bndr
416 abs_vars = abstractVars dest_lvl env bind_fvs
418 dest_lvl | isUnLiftedType (idType bndr) = destLevel env bind_fvs False `maxLvl` Level 1 0
419 | otherwise = destLevel env bind_fvs (isFunction rhs)
420 -- Hack alert! We do have some unlifted bindings, for cheap primops, and
421 -- it is ok to float them out; but not to the top level. If they would otherwise
422 -- go to the top level, we pin them inside the topmost lambda
427 lvlBind top_lvl ctxt_lvl env (AnnRec pairs)
428 | isInlineCtxt ctxt_lvl -- Don't do anything inside InlineMe
429 = mapLvl (lvlExpr ctxt_lvl env) rhss `thenLvl` \ rhss' ->
430 returnLvl (Rec ((bndrs `zip` repeat ctxt_lvl) `zip` rhss'), env)
433 = cloneRecVars top_lvl env bndrs ctxt_lvl dest_lvl `thenLvl` \ (new_env, new_bndrs) ->
434 mapLvl (lvlExpr ctxt_lvl new_env) rhss `thenLvl` \ new_rhss ->
435 returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env)
437 | isSingleton pairs && count isId abs_vars > 1
438 = -- Special case for self recursion where there are
439 -- several variables carried around: build a local loop:
440 -- poly_f = \abs_vars. \lam_vars . letrec f = \lam_vars. rhs in f lam_vars
441 -- This just makes the closures a bit smaller. If we don't do
442 -- this, allocation rises significantly on some programs
444 -- We could elaborate it for the case where there are several
445 -- mutually functions, but it's quite a bit more complicated
447 -- This all seems a bit ad hoc -- sigh
449 (bndr,rhs) = head pairs
450 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
451 rhs_env = extendLvlEnv env abs_vars_w_lvls
453 cloneVar NotTopLevel rhs_env bndr rhs_lvl rhs_lvl `thenLvl` \ (rhs_env', new_bndr) ->
455 (lam_bndrs, rhs_body) = collectAnnBndrs rhs
456 (body_lvl, new_lam_bndrs) = lvlLamBndrs rhs_lvl lam_bndrs
457 body_env = extendLvlEnv rhs_env' new_lam_bndrs
459 lvlExpr body_lvl body_env rhs_body `thenLvl` \ new_rhs_body ->
460 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (poly_env, [poly_bndr]) ->
461 returnLvl (Rec [((poly_bndr,dest_lvl), mkLams abs_vars_w_lvls $
462 mkLams new_lam_bndrs $
463 Let (Rec [((new_bndr,rhs_lvl), mkLams new_lam_bndrs new_rhs_body)])
464 (mkVarApps (Var new_bndr) lam_bndrs))],
467 | otherwise -- Non-null abs_vars
468 = newPolyBndrs dest_lvl env abs_vars bndrs `thenLvl` \ (new_env, new_bndrs) ->
469 mapLvl (lvlFloatRhs abs_vars dest_lvl new_env) rhss `thenLvl` \ new_rhss ->
470 returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env)
473 (bndrs,rhss) = unzip pairs
475 -- Finding the free vars of the binding group is annoying
476 bind_fvs = (unionVarSets [ idFreeVars bndr `unionVarSet` rhs_fvs
477 | (bndr, (rhs_fvs,_)) <- pairs])
481 dest_lvl = destLevel env bind_fvs (all isFunction rhss)
482 abs_vars = abstractVars dest_lvl env bind_fvs
484 ----------------------------------------------------
485 -- Three help functons for the type-abstraction case
487 lvlFloatRhs abs_vars dest_lvl env rhs
488 = lvlExpr rhs_lvl rhs_env rhs `thenLvl` \ rhs' ->
489 returnLvl (mkLams abs_vars_w_lvls rhs')
491 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
492 rhs_env = extendLvlEnv env abs_vars_w_lvls
496 %************************************************************************
498 \subsection{Deciding floatability}
500 %************************************************************************
503 collectAnnBndrs :: CoreExprWithFVs -> ([CoreBndr], CoreExprWithFVs)
504 collectAnnBndrs (_, AnnLam b e) = case collectAnnBndrs e of
505 (bs,e') -> (b:bs, e')
506 collectAnnBndrs e = ([], e)
508 lvlLamBndrs :: Level -> [CoreBndr] -> (Level, [(CoreBndr, Level)])
509 -- Compute the levels for the binders of a lambda group
510 -- The binders returned are exactly the same as the ones passed,
511 -- but they are now paired with a level
515 lvlLamBndrs lvl bndrs
516 = go (incMinorLvl lvl)
517 False -- Havn't bumped major level in this group
520 go old_lvl bumped_major rev_lvld_bndrs (bndr:bndrs)
521 | isId bndr && -- Go to the next major level if this is a value binder,
522 not bumped_major && -- and we havn't already gone to the next level (one jump per group)
523 not (isOneShotLambda bndr) -- and it isn't a one-shot lambda
524 = go new_lvl True ((bndr,new_lvl) : rev_lvld_bndrs) bndrs
527 = go old_lvl bumped_major ((bndr,old_lvl) : rev_lvld_bndrs) bndrs
530 new_lvl = incMajorLvl old_lvl
532 go old_lvl _ rev_lvld_bndrs []
533 = (old_lvl, reverse rev_lvld_bndrs)
534 -- a lambda like this (\x -> coerce t (\s -> ...))
535 -- This happens quite a bit in state-transformer programs
539 -- Destintion level is the max Id level of the expression
540 -- (We'll abstract the type variables, if any.)
541 destLevel :: LevelEnv -> VarSet -> Bool -> Level
542 destLevel env fvs is_function
544 && is_function = tOP_LEVEL -- Send functions to top level; see
545 -- the comments with isFunction
546 | otherwise = maxIdLevel env fvs
548 isFunction :: CoreExprWithFVs -> Bool
549 -- The idea here is that we want to float *functions* to
550 -- the top level. This saves no work, but
551 -- (a) it can make the host function body a lot smaller,
552 -- and hence inlinable.
553 -- (b) it can also save allocation when the function is recursive:
554 -- h = \x -> letrec f = \y -> ...f...y...x...
557 -- f = \x y -> ...(f x)...y...x...
559 -- No allocation for f now.
560 -- We may only want to do this if there are sufficiently few free
561 -- variables. We certainly only want to do it for values, and not for
562 -- constructors. So the simple thing is just to look for lambdas
563 isFunction (_, AnnLam b e) | isId b = True
564 | otherwise = isFunction e
565 isFunction (_, AnnNote n e) = isFunction e
566 isFunction other = False
570 %************************************************************************
572 \subsection{Free-To-Level Monad}
574 %************************************************************************
577 type LevelEnv = (Bool, -- True <=> Float lambdas too
578 VarEnv Level, -- Domain is *post-cloned* TyVars and Ids
579 Subst, -- Domain is pre-cloned Ids; tracks the in-scope set
580 -- so that subtitution is capture-avoiding
581 IdEnv ([Var], LevelledExpr)) -- Domain is pre-cloned Ids
582 -- We clone let-bound variables so that they are still
583 -- distinct when floated out; hence the SubstEnv/IdEnv.
584 -- (see point 3 of the module overview comment).
585 -- We also use these envs when making a variable polymorphic
586 -- because we want to float it out past a big lambda.
588 -- The SubstEnv and IdEnv always implement the same mapping, but the
589 -- SubstEnv maps to CoreExpr and the IdEnv to LevelledExpr
590 -- Since the range is always a variable or type application,
591 -- there is never any difference between the two, but sadly
592 -- the types differ. The SubstEnv is used when substituting in
593 -- a variable's IdInfo; the IdEnv when we find a Var.
595 -- In addition the IdEnv records a list of tyvars free in the
596 -- type application, just so we don't have to call freeVars on
597 -- the type application repeatedly.
599 -- The domain of the both envs is *pre-cloned* Ids, though
601 -- The domain of the VarEnv Level is the *post-cloned* Ids
603 initialEnv :: Bool -> LevelEnv
604 initialEnv float_lams = (float_lams, emptyVarEnv, emptySubst, emptyVarEnv)
606 floatLams :: LevelEnv -> Bool
607 floatLams (float_lams, _, _, _) = float_lams
609 extendLvlEnv :: LevelEnv -> [(Var,Level)] -> LevelEnv
610 -- Used when *not* cloning
611 extendLvlEnv (float_lams, lvl_env, subst, id_env) prs
613 foldl add_lvl lvl_env prs,
614 foldl del_subst subst prs,
615 foldl del_id id_env prs)
617 add_lvl env (v,l) = extendVarEnv env v l
618 del_subst env (v,_) = extendInScope env v
619 del_id env (v,_) = delVarEnv env v
620 -- We must remove any clone for this variable name in case of
621 -- shadowing. This bit me in the following case
622 -- (in nofib/real/gg/Spark.hs):
625 -- ... -> case e of wild {
626 -- ... -> ... wild ...
630 -- The inside occurrence of @wild@ was being replaced with @ds@,
631 -- incorrectly, because the SubstEnv was still lying around. Ouch!
634 -- extendCaseBndrLvlEnv adds the mapping case-bndr->scrut-var if it can
635 -- (see point 4 of the module overview comment)
636 extendCaseBndrLvlEnv (float_lams, lvl_env, subst, id_env) (Var scrut_var) case_bndr lvl
638 extendVarEnv lvl_env case_bndr lvl,
639 extendSubst subst case_bndr (DoneEx (Var scrut_var)),
640 extendVarEnv id_env case_bndr ([scrut_var], Var scrut_var))
642 extendCaseBndrLvlEnv env scrut case_bndr lvl
643 = extendLvlEnv env [(case_bndr,lvl)]
645 extendPolyLvlEnv dest_lvl (float_lams, lvl_env, subst, id_env) abs_vars bndr_pairs
647 foldl add_lvl lvl_env bndr_pairs,
648 foldl add_subst subst bndr_pairs,
649 foldl add_id id_env bndr_pairs)
651 add_lvl env (v,v') = extendVarEnv env v' dest_lvl
652 add_subst env (v,v') = extendSubst env v (DoneEx (mkVarApps (Var v') abs_vars))
653 add_id env (v,v') = extendVarEnv env v ((v':abs_vars), mkVarApps (Var v') abs_vars)
655 extendCloneLvlEnv lvl (float_lams, lvl_env, _, id_env) new_subst bndr_pairs
657 foldl add_lvl lvl_env bndr_pairs,
659 foldl add_id id_env bndr_pairs)
661 add_lvl env (v,v') = extendVarEnv env v' lvl
662 add_id env (v,v') = extendVarEnv env v ([v'], Var v')
665 maxIdLevel :: LevelEnv -> VarSet -> Level
666 maxIdLevel (_, lvl_env,_,id_env) var_set
667 = foldVarSet max_in tOP_LEVEL var_set
669 max_in in_var lvl = foldr max_out lvl (case lookupVarEnv id_env in_var of
670 Just (abs_vars, _) -> abs_vars
674 | isId out_var = case lookupVarEnv lvl_env out_var of
675 Just lvl' -> maxLvl lvl' lvl
677 | otherwise = lvl -- Ignore tyvars in *maxIdLevel*
679 lookupVar :: LevelEnv -> Id -> LevelledExpr
680 lookupVar (_, _, _, id_env) v = case lookupVarEnv id_env v of
681 Just (_, expr) -> expr
684 abstractVars :: Level -> LevelEnv -> VarSet -> [Var]
685 -- Find the variables in fvs, free vars of the target expresion,
686 -- whose level is greater than the destination level
687 -- These are the ones we are going to abstract out
688 abstractVars dest_lvl env fvs
689 = uniq (sortLt lt [var | fv <- varSetElems fvs, var <- absVarsOf dest_lvl env fv])
691 -- Sort the variables so we don't get
692 -- mixed-up tyvars and Ids; it's just messy
693 v1 `lt` v2 = case (isId v1, isId v2) of
694 (True, False) -> False
695 (False, True) -> True
696 other -> v1 < v2 -- Same family
698 uniq :: [Var] -> [Var]
699 -- Remove adjacent duplicates; the sort will have brought them together
700 uniq (v1:v2:vs) | v1 == v2 = uniq (v2:vs)
701 | otherwise = v1 : uniq (v2:vs)
704 absVarsOf :: Level -> LevelEnv -> Var -> [Var]
705 -- If f is free in the expression, and f maps to poly_f a b c in the
706 -- current substitution, then we must report a b c as candidate type
708 absVarsOf dest_lvl (_, lvl_env, _, id_env) v
710 = [zap av2 | av1 <- lookup_avs v, av2 <- add_tyvars av1, abstract_me av2]
713 = if abstract_me v then [v] else []
716 abstract_me v = case lookupVarEnv lvl_env v of
717 Just lvl -> dest_lvl `ltLvl` lvl
720 lookup_avs v = case lookupVarEnv id_env v of
721 Just (abs_vars, _) -> abs_vars
724 add_tyvars v | isId v = v : varSetElems (idFreeTyVars v)
727 -- We are going to lambda-abstract, so nuke any IdInfo,
728 -- and add the tyvars of the Id (if necessary)
729 zap v | isId v = WARN( workerExists (idWorkerInfo v) ||
730 not (isEmptyCoreRules (idSpecialisation v)),
731 text "absVarsOf: discarding info on" <+> ppr v )
732 setIdInfo v vanillaIdInfo
737 type LvlM result = UniqSM result
746 newPolyBndrs dest_lvl env abs_vars bndrs
747 = getUniquesUs `thenLvl` \ uniqs ->
749 new_bndrs = zipWith mk_poly_bndr bndrs uniqs
751 returnLvl (extendPolyLvlEnv dest_lvl env abs_vars (bndrs `zip` new_bndrs), new_bndrs)
753 mk_poly_bndr bndr uniq = mkSysLocal (_PK_ str) uniq poly_ty
755 str = "poly_" ++ occNameUserString (getOccName bndr)
756 poly_ty = mkPiTypes abs_vars (idType bndr)
760 -> [CoreBndr] -> Type -- Abstract wrt these bndrs
762 newLvlVar str vars body_ty
763 = getUniqueUs `thenLvl` \ uniq ->
764 returnUs (mkSysLocal (_PK_ str) uniq (mkPiTypes vars body_ty))
766 -- The deeply tiresome thing is that we have to apply the substitution
767 -- to the rules inside each Id. Grr. But it matters.
769 cloneVar :: TopLevelFlag -> LevelEnv -> Id -> Level -> Level -> LvlM (LevelEnv, Id)
770 cloneVar TopLevel env v ctxt_lvl dest_lvl
771 = returnUs (env, v) -- Don't clone top level things
772 cloneVar NotTopLevel env@(_,_,subst,_) v ctxt_lvl dest_lvl
774 getUs `thenLvl` \ us ->
776 (subst', v1) = substAndCloneId subst us v
777 v2 = zap_demand ctxt_lvl dest_lvl v1
778 env' = extendCloneLvlEnv dest_lvl env subst' [(v,v2)]
782 cloneRecVars :: TopLevelFlag -> LevelEnv -> [Id] -> Level -> Level -> LvlM (LevelEnv, [Id])
783 cloneRecVars TopLevel env vs ctxt_lvl dest_lvl
784 = returnUs (env, vs) -- Don't clone top level things
785 cloneRecVars NotTopLevel env@(_,_,subst,_) vs ctxt_lvl dest_lvl
786 = ASSERT( all isId vs )
787 getUs `thenLvl` \ us ->
789 (subst', vs1) = substAndCloneRecIds subst us vs
790 vs2 = map (zap_demand ctxt_lvl dest_lvl) vs1
791 env' = extendCloneLvlEnv dest_lvl env subst' (vs `zip` vs2)
795 -- VERY IMPORTANT: we must zap the demand info
796 -- if the thing is going to float out past a lambda
797 zap_demand dest_lvl ctxt_lvl id
798 | ctxt_lvl == dest_lvl = id -- Stays put
799 | otherwise = zapDemandIdInfo id -- Floats out