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 CmdLineOpts ( FloatOutSwitches(..) )
58 import CoreUtils ( exprType, exprIsTrivial, exprIsBottom, mkPiTypes )
59 import CoreFVs -- all of it
61 import Id ( Id, idType, mkSysLocal, isOneShotLambda, zapDemandIdInfo,
62 idSpecialisation, idWorkerInfo, setIdInfo
64 import IdInfo ( workerExists, vanillaIdInfo, )
68 import Name ( getOccName )
69 import OccName ( occNameUserString )
70 import Type ( isUnLiftedType, Type )
71 import BasicTypes ( TopLevelFlag(..) )
73 import Util ( sortLt, isSingleton, count )
77 %************************************************************************
79 \subsection{Level numbers}
81 %************************************************************************
84 data Level = InlineCtxt -- A level that's used only for
85 -- the context parameter ctxt_lvl
86 | Level Int -- Level number of enclosing lambdas
87 Int -- Number of big-lambda and/or case expressions between
88 -- here and the nearest enclosing lambda
91 The {\em level number} on a (type-)lambda-bound variable is the
92 nesting depth of the (type-)lambda which binds it. The outermost lambda
93 has level 1, so (Level 0 0) means that the variable is bound outside any lambda.
95 On an expression, it's the maximum level number of its free
96 (type-)variables. On a let(rec)-bound variable, it's the level of its
97 RHS. On a case-bound variable, it's the number of enclosing lambdas.
99 Top-level variables: level~0. Those bound on the RHS of a top-level
100 definition but ``before'' a lambda; e.g., the \tr{x} in (levels shown
101 as ``subscripts'')...
103 a_0 = let b_? = ... in
104 x_1 = ... b ... in ...
107 The main function @lvlExpr@ carries a ``context level'' (@ctxt_lvl@).
108 That's meant to be the level number of the enclosing binder in the
109 final (floated) program. If the level number of a sub-expression is
110 less than that of the context, then it might be worth let-binding the
111 sub-expression so that it will indeed float.
113 If you can float to level @Level 0 0@ worth doing so because then your
114 allocation becomes static instead of dynamic. We always start with
120 @InlineCtxt@ very similar to @Level 0 0@, but is used for one purpose:
121 to say "don't float anything out of here". That's exactly what we
122 want for the body of an INLINE, where we don't want to float anything
123 out at all. See notes with lvlMFE below.
127 -- At one time I tried the effect of not float anything out of an InlineMe,
128 -- but it sometimes works badly. For example, consider PrelArr.done. It
129 -- has the form __inline (\d. e)
130 -- where e doesn't mention d. If we float this to
131 -- __inline (let x = e in \d. x)
132 -- things are bad. The inliner doesn't even inline it because it doesn't look
133 -- like a head-normal form. So it seems a lesser evil to let things float.
134 -- In SetLevels we do set the context to (Level 0 0) when we get to an InlineMe
135 -- which discourages floating out.
137 So the conclusion is: don't do any floating at all inside an InlineMe.
138 (In the above example, don't float the {x=e} out of the \d.)
140 One particular case is that of workers: we don't want to float the
141 call to the worker outside the wrapper, otherwise the worker might get
142 inlined into the floated expression, and an importing module won't see
146 type LevelledExpr = TaggedExpr Level
147 type LevelledBind = TaggedBind Level
149 tOP_LEVEL = Level 0 0
150 iNLINE_CTXT = InlineCtxt
152 incMajorLvl :: Level -> Level
153 -- For InlineCtxt we ignore any inc's; we don't want
154 -- to do any floating at all; see notes above
155 incMajorLvl InlineCtxt = InlineCtxt
156 incMajorLvl (Level major minor) = Level (major+1) 0
158 incMinorLvl :: Level -> Level
159 incMinorLvl InlineCtxt = InlineCtxt
160 incMinorLvl (Level major minor) = Level major (minor+1)
162 maxLvl :: Level -> Level -> Level
163 maxLvl InlineCtxt l2 = l2
164 maxLvl l1 InlineCtxt = l1
165 maxLvl l1@(Level maj1 min1) l2@(Level maj2 min2)
166 | (maj1 > maj2) || (maj1 == maj2 && min1 > min2) = l1
169 ltLvl :: Level -> Level -> Bool
170 ltLvl any_lvl InlineCtxt = False
171 ltLvl InlineCtxt (Level _ _) = True
172 ltLvl (Level maj1 min1) (Level maj2 min2)
173 = (maj1 < maj2) || (maj1 == maj2 && min1 < min2)
175 ltMajLvl :: Level -> Level -> Bool
176 -- Tells if one level belongs to a difft *lambda* level to another
177 ltMajLvl any_lvl InlineCtxt = False
178 ltMajLvl InlineCtxt (Level maj2 _) = 0 < maj2
179 ltMajLvl (Level maj1 _) (Level maj2 _) = maj1 < maj2
181 isTopLvl :: Level -> Bool
182 isTopLvl (Level 0 0) = True
183 isTopLvl other = False
185 isInlineCtxt :: Level -> Bool
186 isInlineCtxt InlineCtxt = True
187 isInlineCtxt other = False
189 instance Outputable Level where
190 ppr InlineCtxt = text "<INLINE>"
191 ppr (Level maj min) = hcat [ char '<', int maj, char ',', int min, char '>' ]
193 instance Eq Level where
194 InlineCtxt == InlineCtxt = True
195 (Level maj1 min1) == (Level maj2 min2) = maj1==maj2 && min1==min2
200 %************************************************************************
202 \subsection{Main level-setting code}
204 %************************************************************************
207 setLevels :: FloatOutSwitches
212 setLevels float_lams binds us
213 = initLvl us (do_them binds)
215 -- "do_them"'s main business is to thread the monad along
216 -- It gives each top binding the same empty envt, because
217 -- things unbound in the envt have level number zero implicitly
218 do_them :: [CoreBind] -> LvlM [LevelledBind]
220 do_them [] = returnLvl []
222 = lvlTopBind init_env b `thenLvl` \ (lvld_bind, _) ->
223 do_them bs `thenLvl` \ lvld_binds ->
224 returnLvl (lvld_bind : lvld_binds)
226 init_env = initialEnv float_lams
228 lvlTopBind env (NonRec binder rhs)
229 = lvlBind TopLevel tOP_LEVEL env (AnnNonRec binder (freeVars rhs))
230 -- Rhs can have no free vars!
232 lvlTopBind env (Rec pairs)
233 = lvlBind TopLevel tOP_LEVEL env (AnnRec [(b,freeVars rhs) | (b,rhs) <- pairs])
236 %************************************************************************
238 \subsection{Setting expression levels}
240 %************************************************************************
243 lvlExpr :: Level -- ctxt_lvl: Level of enclosing expression
244 -> LevelEnv -- Level of in-scope names/tyvars
245 -> CoreExprWithFVs -- input expression
246 -> LvlM LevelledExpr -- Result expression
249 The @ctxt_lvl@ is, roughly, the level of the innermost enclosing
250 binder. Here's an example
252 v = \x -> ...\y -> let r = case (..x..) of
256 When looking at the rhs of @r@, @ctxt_lvl@ will be 1 because that's
257 the level of @r@, even though it's inside a level-2 @\y@. It's
258 important that @ctxt_lvl@ is 1 and not 2 in @r@'s rhs, because we
259 don't want @lvlExpr@ to turn the scrutinee of the @case@ into an MFE
260 --- because it isn't a *maximal* free expression.
262 If there were another lambda in @r@'s rhs, it would get level-2 as well.
265 lvlExpr _ _ (_, AnnType ty) = returnLvl (Type ty)
266 lvlExpr _ env (_, AnnVar v) = returnLvl (lookupVar env v)
267 lvlExpr _ env (_, AnnLit lit) = returnLvl (Lit lit)
269 lvlExpr ctxt_lvl env (_, AnnApp fun arg)
270 = lvl_fun fun `thenLvl` \ fun' ->
271 lvlMFE False ctxt_lvl env arg `thenLvl` \ arg' ->
272 returnLvl (App fun' arg')
274 lvl_fun (_, AnnCase _ _ _) = lvlMFE True ctxt_lvl env fun
275 lvl_fun other = lvlExpr ctxt_lvl env fun
276 -- We don't do MFE on partial applications generally,
277 -- but we do if the function is big and hairy, like a case
279 lvlExpr ctxt_lvl env (_, AnnNote InlineMe expr)
280 -- Don't float anything out of an InlineMe; hence the iNLINE_CTXT
281 = lvlExpr iNLINE_CTXT env expr `thenLvl` \ expr' ->
282 returnLvl (Note InlineMe expr')
284 lvlExpr ctxt_lvl env (_, AnnNote note expr)
285 = lvlExpr ctxt_lvl env expr `thenLvl` \ expr' ->
286 returnLvl (Note note expr')
288 -- We don't split adjacent lambdas. That is, given
290 -- we don't float to give
291 -- \x -> let v = x+y in \y -> (v,y)
292 -- Why not? Because partial applications are fairly rare, and splitting
293 -- lambdas makes them more expensive.
295 lvlExpr ctxt_lvl env expr@(_, AnnLam bndr rhs)
296 = lvlMFE True new_lvl new_env body `thenLvl` \ new_body ->
297 returnLvl (mkLams new_bndrs new_body)
299 (bndrs, body) = collectAnnBndrs expr
300 (new_lvl, new_bndrs) = lvlLamBndrs ctxt_lvl bndrs
301 new_env = extendLvlEnv env new_bndrs
302 -- At one time we called a special verion of collectBinders,
303 -- which ignored coercions, because we don't want to split
304 -- a lambda like this (\x -> coerce t (\s -> ...))
305 -- This used to happen quite a bit in state-transformer programs,
306 -- but not nearly so much now non-recursive newtypes are transparent.
307 -- [See SetLevels rev 1.50 for a version with this approach.]
309 lvlExpr ctxt_lvl env (_, AnnLet bind body)
310 = lvlBind NotTopLevel ctxt_lvl env bind `thenLvl` \ (bind', new_env) ->
311 lvlExpr ctxt_lvl new_env body `thenLvl` \ body' ->
312 returnLvl (Let bind' body')
314 lvlExpr ctxt_lvl env (_, AnnCase expr case_bndr alts)
315 = lvlMFE True ctxt_lvl env expr `thenLvl` \ expr' ->
317 alts_env = extendCaseBndrLvlEnv env expr' case_bndr incd_lvl
319 mapLvl (lvl_alt alts_env) alts `thenLvl` \ alts' ->
320 returnLvl (Case expr' (case_bndr, incd_lvl) alts')
322 incd_lvl = incMinorLvl ctxt_lvl
324 lvl_alt alts_env (con, bs, rhs)
325 = lvlMFE True incd_lvl new_env rhs `thenLvl` \ rhs' ->
326 returnLvl (con, bs', rhs')
328 bs' = [ (b, incd_lvl) | b <- bs ]
329 new_env = extendLvlEnv alts_env bs'
332 @lvlMFE@ is just like @lvlExpr@, except that it might let-bind
333 the expression, so that it can itself be floated.
336 lvlMFE :: Bool -- True <=> strict context [body of case or let]
337 -> Level -- Level of innermost enclosing lambda/tylam
338 -> LevelEnv -- Level of in-scope names/tyvars
339 -> CoreExprWithFVs -- input expression
340 -> LvlM LevelledExpr -- Result expression
342 lvlMFE strict_ctxt ctxt_lvl env (_, AnnType ty)
343 = returnLvl (Type ty)
345 lvlMFE strict_ctxt ctxt_lvl env ann_expr@(fvs, _)
346 | isUnLiftedType ty -- Can't let-bind it
347 || isInlineCtxt ctxt_lvl -- Don't float out of an __inline__ context
348 || not good_destination
349 || exprIsTrivial expr -- Is trivial
350 || (strict_ctxt && exprIsBottom expr) -- Strict context and is bottom
351 -- e.g. \x -> error "foo"
352 -- No gain from floating this
353 = -- Don't float it out
354 lvlExpr ctxt_lvl env ann_expr
356 | otherwise -- Float it out!
357 = lvlFloatRhs abs_vars dest_lvl env ann_expr `thenLvl` \ expr' ->
358 newLvlVar "lvl" abs_vars ty `thenLvl` \ var ->
359 returnLvl (Let (NonRec (var,dest_lvl) expr')
360 (mkVarApps (Var var) abs_vars))
362 expr = deAnnotate ann_expr
364 dest_lvl = destLevel env fvs (isFunction ann_expr)
365 abs_vars = abstractVars dest_lvl env fvs
367 good_destination = dest_lvl `ltMajLvl` ctxt_lvl -- Escapes a value lambda
368 || (isTopLvl dest_lvl -- Goes to the top
370 && not strict_ctxt) -- or from a strict context
371 -- A decision to float entails let-binding this thing, and we only do
372 -- that if we'll escape a value lambda, or will go to the top level.
375 -- concat = /\ a -> foldr ..a.. (++) []
376 -- was getting turned into
377 -- concat = /\ a -> lvl a
378 -- lvl = /\ a -> foldr ..a.. (++) []
379 -- which is pretty stupid. Hence the strict_ctxt test
381 -- We are keen to float something to the top level, even if it does not
382 -- escape a lambda, because then it needs no allocation. But it's controlled
383 -- by a flag, because doing this too early loses opportunities for RULES
384 -- which (needless to say) are important in some nofib programs
385 -- (gcd is an example).
389 %************************************************************************
391 \subsection{Bindings}
393 %************************************************************************
395 The binding stuff works for top level too.
398 lvlBind :: TopLevelFlag -- Used solely to decide whether to clone
399 -> Level -- Context level; might be Top even for bindings nested in the RHS
400 -- of a top level binding
403 -> LvlM (LevelledBind, LevelEnv)
405 lvlBind top_lvl ctxt_lvl env (AnnNonRec bndr rhs@(rhs_fvs,_))
406 | isInlineCtxt ctxt_lvl -- Don't do anything inside InlineMe
407 = lvlExpr ctxt_lvl env rhs `thenLvl` \ rhs' ->
408 returnLvl (NonRec (bndr, ctxt_lvl) rhs', env)
411 = -- No type abstraction; clone existing binder
412 lvlExpr dest_lvl env rhs `thenLvl` \ rhs' ->
413 cloneVar top_lvl env bndr ctxt_lvl dest_lvl `thenLvl` \ (env', bndr') ->
414 returnLvl (NonRec (bndr', dest_lvl) rhs', env')
417 = -- Yes, type abstraction; create a new binder, extend substitution, etc
418 lvlFloatRhs abs_vars dest_lvl env rhs `thenLvl` \ rhs' ->
419 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (env', [bndr']) ->
420 returnLvl (NonRec (bndr', dest_lvl) rhs', env')
423 bind_fvs = rhs_fvs `unionVarSet` idFreeVars bndr
424 abs_vars = abstractVars dest_lvl env bind_fvs
426 dest_lvl | isUnLiftedType (idType bndr) = destLevel env bind_fvs False `maxLvl` Level 1 0
427 | otherwise = destLevel env bind_fvs (isFunction rhs)
428 -- Hack alert! We do have some unlifted bindings, for cheap primops, and
429 -- it is ok to float them out; but not to the top level. If they would otherwise
430 -- go to the top level, we pin them inside the topmost lambda
435 lvlBind top_lvl ctxt_lvl env (AnnRec pairs)
436 | isInlineCtxt ctxt_lvl -- Don't do anything inside InlineMe
437 = mapLvl (lvlExpr ctxt_lvl env) rhss `thenLvl` \ rhss' ->
438 returnLvl (Rec ((bndrs `zip` repeat ctxt_lvl) `zip` rhss'), env)
441 = cloneRecVars top_lvl env bndrs ctxt_lvl dest_lvl `thenLvl` \ (new_env, new_bndrs) ->
442 mapLvl (lvlExpr ctxt_lvl new_env) rhss `thenLvl` \ new_rhss ->
443 returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env)
445 | isSingleton pairs && count isId abs_vars > 1
446 = -- Special case for self recursion where there are
447 -- several variables carried around: build a local loop:
448 -- poly_f = \abs_vars. \lam_vars . letrec f = \lam_vars. rhs in f lam_vars
449 -- This just makes the closures a bit smaller. If we don't do
450 -- this, allocation rises significantly on some programs
452 -- We could elaborate it for the case where there are several
453 -- mutually functions, but it's quite a bit more complicated
455 -- This all seems a bit ad hoc -- sigh
457 (bndr,rhs) = head pairs
458 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
459 rhs_env = extendLvlEnv env abs_vars_w_lvls
461 cloneVar NotTopLevel rhs_env bndr rhs_lvl rhs_lvl `thenLvl` \ (rhs_env', new_bndr) ->
463 (lam_bndrs, rhs_body) = collectAnnBndrs rhs
464 (body_lvl, new_lam_bndrs) = lvlLamBndrs rhs_lvl lam_bndrs
465 body_env = extendLvlEnv rhs_env' new_lam_bndrs
467 lvlExpr body_lvl body_env rhs_body `thenLvl` \ new_rhs_body ->
468 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (poly_env, [poly_bndr]) ->
469 returnLvl (Rec [((poly_bndr,dest_lvl), mkLams abs_vars_w_lvls $
470 mkLams new_lam_bndrs $
471 Let (Rec [((new_bndr,rhs_lvl), mkLams new_lam_bndrs new_rhs_body)])
472 (mkVarApps (Var new_bndr) lam_bndrs))],
475 | otherwise -- Non-null abs_vars
476 = newPolyBndrs dest_lvl env abs_vars bndrs `thenLvl` \ (new_env, new_bndrs) ->
477 mapLvl (lvlFloatRhs abs_vars dest_lvl new_env) rhss `thenLvl` \ new_rhss ->
478 returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env)
481 (bndrs,rhss) = unzip pairs
483 -- Finding the free vars of the binding group is annoying
484 bind_fvs = (unionVarSets [ idFreeVars bndr `unionVarSet` rhs_fvs
485 | (bndr, (rhs_fvs,_)) <- pairs])
489 dest_lvl = destLevel env bind_fvs (all isFunction rhss)
490 abs_vars = abstractVars dest_lvl env bind_fvs
492 ----------------------------------------------------
493 -- Three help functons for the type-abstraction case
495 lvlFloatRhs abs_vars dest_lvl env rhs
496 = lvlExpr rhs_lvl rhs_env rhs `thenLvl` \ rhs' ->
497 returnLvl (mkLams abs_vars_w_lvls rhs')
499 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
500 rhs_env = extendLvlEnv env abs_vars_w_lvls
504 %************************************************************************
506 \subsection{Deciding floatability}
508 %************************************************************************
511 lvlLamBndrs :: Level -> [CoreBndr] -> (Level, [(CoreBndr, Level)])
512 -- Compute the levels for the binders of a lambda group
513 -- The binders returned are exactly the same as the ones passed,
514 -- but they are now paired with a level
518 lvlLamBndrs lvl bndrs
519 = go (incMinorLvl lvl)
520 False -- Havn't bumped major level in this group
523 go old_lvl bumped_major rev_lvld_bndrs (bndr:bndrs)
524 | isId bndr && -- Go to the next major level if this is a value binder,
525 not bumped_major && -- and we havn't already gone to the next level (one jump per group)
526 not (isOneShotLambda bndr) -- and it isn't a one-shot lambda
527 = go new_lvl True ((bndr,new_lvl) : rev_lvld_bndrs) bndrs
530 = go old_lvl bumped_major ((bndr,old_lvl) : rev_lvld_bndrs) bndrs
533 new_lvl = incMajorLvl old_lvl
535 go old_lvl _ rev_lvld_bndrs []
536 = (old_lvl, reverse rev_lvld_bndrs)
537 -- a lambda like this (\x -> coerce t (\s -> ...))
538 -- This happens quite a bit in state-transformer programs
542 -- Destintion level is the max Id level of the expression
543 -- (We'll abstract the type variables, if any.)
544 destLevel :: LevelEnv -> VarSet -> Bool -> Level
545 destLevel env fvs is_function
547 && is_function = tOP_LEVEL -- Send functions to top level; see
548 -- the comments with isFunction
549 | otherwise = maxIdLevel env fvs
551 isFunction :: CoreExprWithFVs -> Bool
552 -- The idea here is that we want to float *functions* to
553 -- the top level. This saves no work, but
554 -- (a) it can make the host function body a lot smaller,
555 -- and hence inlinable.
556 -- (b) it can also save allocation when the function is recursive:
557 -- h = \x -> letrec f = \y -> ...f...y...x...
560 -- f = \x y -> ...(f x)...y...x...
562 -- No allocation for f now.
563 -- We may only want to do this if there are sufficiently few free
564 -- variables. We certainly only want to do it for values, and not for
565 -- constructors. So the simple thing is just to look for lambdas
566 isFunction (_, AnnLam b e) | isId b = True
567 | otherwise = isFunction e
568 isFunction (_, AnnNote n e) = isFunction e
569 isFunction other = False
573 %************************************************************************
575 \subsection{Free-To-Level Monad}
577 %************************************************************************
580 type LevelEnv = (FloatOutSwitches,
581 VarEnv Level, -- Domain is *post-cloned* TyVars and Ids
582 Subst, -- Domain is pre-cloned Ids; tracks the in-scope set
583 -- so that subtitution is capture-avoiding
584 IdEnv ([Var], LevelledExpr)) -- Domain is pre-cloned Ids
585 -- We clone let-bound variables so that they are still
586 -- distinct when floated out; hence the SubstEnv/IdEnv.
587 -- (see point 3 of the module overview comment).
588 -- We also use these envs when making a variable polymorphic
589 -- because we want to float it out past a big lambda.
591 -- The SubstEnv and IdEnv always implement the same mapping, but the
592 -- SubstEnv maps to CoreExpr and the IdEnv to LevelledExpr
593 -- Since the range is always a variable or type application,
594 -- there is never any difference between the two, but sadly
595 -- the types differ. The SubstEnv is used when substituting in
596 -- a variable's IdInfo; the IdEnv when we find a Var.
598 -- In addition the IdEnv records a list of tyvars free in the
599 -- type application, just so we don't have to call freeVars on
600 -- the type application repeatedly.
602 -- The domain of the both envs is *pre-cloned* Ids, though
604 -- The domain of the VarEnv Level is the *post-cloned* Ids
606 initialEnv :: FloatOutSwitches -> LevelEnv
607 initialEnv float_lams = (float_lams, emptyVarEnv, emptySubst, emptyVarEnv)
609 floatLams :: LevelEnv -> Bool
610 floatLams (FloatOutSw float_lams _, _, _, _) = float_lams
612 floatConsts :: LevelEnv -> Bool
613 floatConsts (FloatOutSw _ float_consts, _, _, _) = float_consts
615 extendLvlEnv :: LevelEnv -> [(Var,Level)] -> LevelEnv
616 -- Used when *not* cloning
617 extendLvlEnv (float_lams, lvl_env, subst, id_env) prs
619 foldl add_lvl lvl_env prs,
620 foldl del_subst subst prs,
621 foldl del_id id_env prs)
623 add_lvl env (v,l) = extendVarEnv env v l
624 del_subst env (v,_) = extendInScope env v
625 del_id env (v,_) = delVarEnv env v
626 -- We must remove any clone for this variable name in case of
627 -- shadowing. This bit me in the following case
628 -- (in nofib/real/gg/Spark.hs):
631 -- ... -> case e of wild {
632 -- ... -> ... wild ...
636 -- The inside occurrence of @wild@ was being replaced with @ds@,
637 -- incorrectly, because the SubstEnv was still lying around. Ouch!
640 -- extendCaseBndrLvlEnv adds the mapping case-bndr->scrut-var if it can
641 -- (see point 4 of the module overview comment)
642 extendCaseBndrLvlEnv (float_lams, lvl_env, subst, id_env) (Var scrut_var) case_bndr lvl
644 extendVarEnv lvl_env case_bndr lvl,
645 extendSubst subst case_bndr (DoneEx (Var scrut_var)),
646 extendVarEnv id_env case_bndr ([scrut_var], Var scrut_var))
648 extendCaseBndrLvlEnv env scrut case_bndr lvl
649 = extendLvlEnv env [(case_bndr,lvl)]
651 extendPolyLvlEnv dest_lvl (float_lams, lvl_env, subst, id_env) abs_vars bndr_pairs
653 foldl add_lvl lvl_env bndr_pairs,
654 foldl add_subst subst bndr_pairs,
655 foldl add_id id_env bndr_pairs)
657 add_lvl env (v,v') = extendVarEnv env v' dest_lvl
658 add_subst env (v,v') = extendSubst env v (DoneEx (mkVarApps (Var v') abs_vars))
659 add_id env (v,v') = extendVarEnv env v ((v':abs_vars), mkVarApps (Var v') abs_vars)
661 extendCloneLvlEnv lvl (float_lams, lvl_env, _, id_env) new_subst bndr_pairs
663 foldl add_lvl lvl_env bndr_pairs,
665 foldl add_id id_env bndr_pairs)
667 add_lvl env (v,v') = extendVarEnv env v' lvl
668 add_id env (v,v') = extendVarEnv env v ([v'], Var v')
671 maxIdLevel :: LevelEnv -> VarSet -> Level
672 maxIdLevel (_, lvl_env,_,id_env) var_set
673 = foldVarSet max_in tOP_LEVEL var_set
675 max_in in_var lvl = foldr max_out lvl (case lookupVarEnv id_env in_var of
676 Just (abs_vars, _) -> abs_vars
680 | isId out_var = case lookupVarEnv lvl_env out_var of
681 Just lvl' -> maxLvl lvl' lvl
683 | otherwise = lvl -- Ignore tyvars in *maxIdLevel*
685 lookupVar :: LevelEnv -> Id -> LevelledExpr
686 lookupVar (_, _, _, id_env) v = case lookupVarEnv id_env v of
687 Just (_, expr) -> expr
690 abstractVars :: Level -> LevelEnv -> VarSet -> [Var]
691 -- Find the variables in fvs, free vars of the target expresion,
692 -- whose level is greater than the destination level
693 -- These are the ones we are going to abstract out
694 abstractVars dest_lvl env fvs
695 = uniq (sortLt lt [var | fv <- varSetElems fvs, var <- absVarsOf dest_lvl env fv])
697 -- Sort the variables so we don't get
698 -- mixed-up tyvars and Ids; it's just messy
699 v1 `lt` v2 = case (isId v1, isId v2) of
700 (True, False) -> False
701 (False, True) -> True
702 other -> v1 < v2 -- Same family
704 uniq :: [Var] -> [Var]
705 -- Remove adjacent duplicates; the sort will have brought them together
706 uniq (v1:v2:vs) | v1 == v2 = uniq (v2:vs)
707 | otherwise = v1 : uniq (v2:vs)
710 absVarsOf :: Level -> LevelEnv -> Var -> [Var]
711 -- If f is free in the expression, and f maps to poly_f a b c in the
712 -- current substitution, then we must report a b c as candidate type
714 absVarsOf dest_lvl (_, lvl_env, _, id_env) v
716 = [zap av2 | av1 <- lookup_avs v, av2 <- add_tyvars av1, abstract_me av2]
719 = if abstract_me v then [v] else []
722 abstract_me v = case lookupVarEnv lvl_env v of
723 Just lvl -> dest_lvl `ltLvl` lvl
726 lookup_avs v = case lookupVarEnv id_env v of
727 Just (abs_vars, _) -> abs_vars
730 add_tyvars v | isId v = v : varSetElems (idFreeTyVars v)
733 -- We are going to lambda-abstract, so nuke any IdInfo,
734 -- and add the tyvars of the Id (if necessary)
735 zap v | isId v = WARN( workerExists (idWorkerInfo v) ||
736 not (isEmptyCoreRules (idSpecialisation v)),
737 text "absVarsOf: discarding info on" <+> ppr v )
738 setIdInfo v vanillaIdInfo
743 type LvlM result = UniqSM result
752 newPolyBndrs dest_lvl env abs_vars bndrs
753 = getUniquesUs `thenLvl` \ uniqs ->
755 new_bndrs = zipWith mk_poly_bndr bndrs uniqs
757 returnLvl (extendPolyLvlEnv dest_lvl env abs_vars (bndrs `zip` new_bndrs), new_bndrs)
759 mk_poly_bndr bndr uniq = mkSysLocal (_PK_ str) uniq poly_ty
761 str = "poly_" ++ occNameUserString (getOccName bndr)
762 poly_ty = mkPiTypes abs_vars (idType bndr)
766 -> [CoreBndr] -> Type -- Abstract wrt these bndrs
768 newLvlVar str vars body_ty
769 = getUniqueUs `thenLvl` \ uniq ->
770 returnUs (mkSysLocal (_PK_ str) uniq (mkPiTypes vars body_ty))
772 -- The deeply tiresome thing is that we have to apply the substitution
773 -- to the rules inside each Id. Grr. But it matters.
775 cloneVar :: TopLevelFlag -> LevelEnv -> Id -> Level -> Level -> LvlM (LevelEnv, Id)
776 cloneVar TopLevel env v ctxt_lvl dest_lvl
777 = returnUs (env, v) -- Don't clone top level things
778 cloneVar NotTopLevel env@(_,_,subst,_) v ctxt_lvl dest_lvl
780 getUs `thenLvl` \ us ->
782 (subst', v1) = substAndCloneId subst us v
783 v2 = zap_demand ctxt_lvl dest_lvl v1
784 env' = extendCloneLvlEnv dest_lvl env subst' [(v,v2)]
788 cloneRecVars :: TopLevelFlag -> LevelEnv -> [Id] -> Level -> Level -> LvlM (LevelEnv, [Id])
789 cloneRecVars TopLevel env vs ctxt_lvl dest_lvl
790 = returnUs (env, vs) -- Don't clone top level things
791 cloneRecVars NotTopLevel env@(_,_,subst,_) vs ctxt_lvl dest_lvl
792 = ASSERT( all isId vs )
793 getUs `thenLvl` \ us ->
795 (subst', vs1) = substAndCloneRecIds subst us vs
796 vs2 = map (zap_demand ctxt_lvl dest_lvl) vs1
797 env' = extendCloneLvlEnv dest_lvl env subst' (vs `zip` vs2)
801 -- VERY IMPORTANT: we must zap the demand info
802 -- if the thing is going to float out past a lambda
803 zap_demand dest_lvl ctxt_lvl id
804 | ctxt_lvl == dest_lvl = id -- Stays put
805 | otherwise = zapDemandIdInfo id -- Floats out