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, exprIsCheap, 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 || exprIsTrivial expr -- Never float if it's trivial
349 || not good_destination
350 = -- Don't float it out
351 lvlExpr ctxt_lvl env ann_expr
353 | otherwise -- Float it out!
354 = lvlFloatRhs abs_vars dest_lvl env ann_expr `thenLvl` \ expr' ->
355 newLvlVar "lvl" abs_vars ty `thenLvl` \ var ->
356 returnLvl (Let (NonRec (var,dest_lvl) expr')
357 (mkVarApps (Var var) abs_vars))
359 expr = deAnnotate ann_expr
361 dest_lvl = destLevel env fvs (isFunction ann_expr)
362 abs_vars = abstractVars dest_lvl env fvs
364 -- A decision to float entails let-binding this thing, and we only do
365 -- that if we'll escape a value lambda, or will go to the top level.
367 | dest_lvl `ltMajLvl` ctxt_lvl -- Escapes a value lambda
368 = not (exprIsCheap expr) || isTopLvl dest_lvl
369 -- Even if it escapes a value lambda, we only
370 -- float if it's not cheap (unless it'll get all the
371 -- way to the top). I've seen cases where we
372 -- float dozens of tiny free expressions, which cost
373 -- more to allocate than to evaluate.
374 -- NB: exprIsCheap is also true of bottom expressions, which
375 -- is good; we don't want to share them
377 -- It's only Really Bad to float a cheap expression out of a
378 -- strict context, because that builds a thunk that otherwise
379 -- would never be built. So another alternative would be to
381 -- || (strict_ctxt && not (exprIsBottom expr))
382 -- to the condition above. We should really try this out.
384 | otherwise -- Does not escape a value lambda
385 = isTopLvl dest_lvl -- Only float if we are going to the top level
386 && floatConsts env -- and the floatConsts flag is on
387 && not strict_ctxt -- Don't float from a strict context
388 -- We are keen to float something to the top level, even if it does not
389 -- escape a lambda, because then it needs no allocation. But it's controlled
390 -- by a flag, because doing this too early loses opportunities for RULES
391 -- which (needless to say) are important in some nofib programs
392 -- (gcd is an example).
395 -- concat = /\ a -> foldr ..a.. (++) []
396 -- was getting turned into
397 -- concat = /\ a -> lvl a
398 -- lvl = /\ a -> foldr ..a.. (++) []
399 -- which is pretty stupid. Hence the strict_ctxt test
403 %************************************************************************
405 \subsection{Bindings}
407 %************************************************************************
409 The binding stuff works for top level too.
412 lvlBind :: TopLevelFlag -- Used solely to decide whether to clone
413 -> Level -- Context level; might be Top even for bindings nested in the RHS
414 -- of a top level binding
417 -> LvlM (LevelledBind, LevelEnv)
419 lvlBind top_lvl ctxt_lvl env (AnnNonRec bndr rhs@(rhs_fvs,_))
420 | isInlineCtxt ctxt_lvl -- Don't do anything inside InlineMe
421 = lvlExpr ctxt_lvl env rhs `thenLvl` \ rhs' ->
422 returnLvl (NonRec (bndr, ctxt_lvl) rhs', env)
425 = -- No type abstraction; clone existing binder
426 lvlExpr dest_lvl env rhs `thenLvl` \ rhs' ->
427 cloneVar top_lvl env bndr ctxt_lvl dest_lvl `thenLvl` \ (env', bndr') ->
428 returnLvl (NonRec (bndr', dest_lvl) rhs', env')
431 = -- Yes, type abstraction; create a new binder, extend substitution, etc
432 lvlFloatRhs abs_vars dest_lvl env rhs `thenLvl` \ rhs' ->
433 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (env', [bndr']) ->
434 returnLvl (NonRec (bndr', dest_lvl) rhs', env')
437 bind_fvs = rhs_fvs `unionVarSet` idFreeVars bndr
438 abs_vars = abstractVars dest_lvl env bind_fvs
440 dest_lvl | isUnLiftedType (idType bndr) = destLevel env bind_fvs False `maxLvl` Level 1 0
441 | otherwise = destLevel env bind_fvs (isFunction rhs)
442 -- Hack alert! We do have some unlifted bindings, for cheap primops, and
443 -- it is ok to float them out; but not to the top level. If they would otherwise
444 -- go to the top level, we pin them inside the topmost lambda
449 lvlBind top_lvl ctxt_lvl env (AnnRec pairs)
450 | isInlineCtxt ctxt_lvl -- Don't do anything inside InlineMe
451 = mapLvl (lvlExpr ctxt_lvl env) rhss `thenLvl` \ rhss' ->
452 returnLvl (Rec ((bndrs `zip` repeat ctxt_lvl) `zip` rhss'), env)
455 = cloneRecVars top_lvl env bndrs ctxt_lvl dest_lvl `thenLvl` \ (new_env, new_bndrs) ->
456 mapLvl (lvlExpr ctxt_lvl new_env) rhss `thenLvl` \ new_rhss ->
457 returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env)
459 | isSingleton pairs && count isId abs_vars > 1
460 = -- Special case for self recursion where there are
461 -- several variables carried around: build a local loop:
462 -- poly_f = \abs_vars. \lam_vars . letrec f = \lam_vars. rhs in f lam_vars
463 -- This just makes the closures a bit smaller. If we don't do
464 -- this, allocation rises significantly on some programs
466 -- We could elaborate it for the case where there are several
467 -- mutually functions, but it's quite a bit more complicated
469 -- This all seems a bit ad hoc -- sigh
471 (bndr,rhs) = head pairs
472 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
473 rhs_env = extendLvlEnv env abs_vars_w_lvls
475 cloneVar NotTopLevel rhs_env bndr rhs_lvl rhs_lvl `thenLvl` \ (rhs_env', new_bndr) ->
477 (lam_bndrs, rhs_body) = collectAnnBndrs rhs
478 (body_lvl, new_lam_bndrs) = lvlLamBndrs rhs_lvl lam_bndrs
479 body_env = extendLvlEnv rhs_env' new_lam_bndrs
481 lvlExpr body_lvl body_env rhs_body `thenLvl` \ new_rhs_body ->
482 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (poly_env, [poly_bndr]) ->
483 returnLvl (Rec [((poly_bndr,dest_lvl), mkLams abs_vars_w_lvls $
484 mkLams new_lam_bndrs $
485 Let (Rec [((new_bndr,rhs_lvl), mkLams new_lam_bndrs new_rhs_body)])
486 (mkVarApps (Var new_bndr) lam_bndrs))],
489 | otherwise -- Non-null abs_vars
490 = newPolyBndrs dest_lvl env abs_vars bndrs `thenLvl` \ (new_env, new_bndrs) ->
491 mapLvl (lvlFloatRhs abs_vars dest_lvl new_env) rhss `thenLvl` \ new_rhss ->
492 returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env)
495 (bndrs,rhss) = unzip pairs
497 -- Finding the free vars of the binding group is annoying
498 bind_fvs = (unionVarSets [ idFreeVars bndr `unionVarSet` rhs_fvs
499 | (bndr, (rhs_fvs,_)) <- pairs])
503 dest_lvl = destLevel env bind_fvs (all isFunction rhss)
504 abs_vars = abstractVars dest_lvl env bind_fvs
506 ----------------------------------------------------
507 -- Three help functons for the type-abstraction case
509 lvlFloatRhs abs_vars dest_lvl env rhs
510 = lvlExpr rhs_lvl rhs_env rhs `thenLvl` \ rhs' ->
511 returnLvl (mkLams abs_vars_w_lvls rhs')
513 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
514 rhs_env = extendLvlEnv env abs_vars_w_lvls
518 %************************************************************************
520 \subsection{Deciding floatability}
522 %************************************************************************
525 lvlLamBndrs :: Level -> [CoreBndr] -> (Level, [(CoreBndr, Level)])
526 -- Compute the levels for the binders of a lambda group
527 -- The binders returned are exactly the same as the ones passed,
528 -- but they are now paired with a level
532 lvlLamBndrs lvl bndrs
533 = go (incMinorLvl lvl)
534 False -- Havn't bumped major level in this group
537 go old_lvl bumped_major rev_lvld_bndrs (bndr:bndrs)
538 | isId bndr && -- Go to the next major level if this is a value binder,
539 not bumped_major && -- and we havn't already gone to the next level (one jump per group)
540 not (isOneShotLambda bndr) -- and it isn't a one-shot lambda
541 = go new_lvl True ((bndr,new_lvl) : rev_lvld_bndrs) bndrs
544 = go old_lvl bumped_major ((bndr,old_lvl) : rev_lvld_bndrs) bndrs
547 new_lvl = incMajorLvl old_lvl
549 go old_lvl _ rev_lvld_bndrs []
550 = (old_lvl, reverse rev_lvld_bndrs)
551 -- a lambda like this (\x -> coerce t (\s -> ...))
552 -- This happens quite a bit in state-transformer programs
556 -- Destintion level is the max Id level of the expression
557 -- (We'll abstract the type variables, if any.)
558 destLevel :: LevelEnv -> VarSet -> Bool -> Level
559 destLevel env fvs is_function
561 && is_function = tOP_LEVEL -- Send functions to top level; see
562 -- the comments with isFunction
563 | otherwise = maxIdLevel env fvs
565 isFunction :: CoreExprWithFVs -> Bool
566 -- The idea here is that we want to float *functions* to
567 -- the top level. This saves no work, but
568 -- (a) it can make the host function body a lot smaller,
569 -- and hence inlinable.
570 -- (b) it can also save allocation when the function is recursive:
571 -- h = \x -> letrec f = \y -> ...f...y...x...
574 -- f = \x y -> ...(f x)...y...x...
576 -- No allocation for f now.
577 -- We may only want to do this if there are sufficiently few free
578 -- variables. We certainly only want to do it for values, and not for
579 -- constructors. So the simple thing is just to look for lambdas
580 isFunction (_, AnnLam b e) | isId b = True
581 | otherwise = isFunction e
582 isFunction (_, AnnNote n e) = isFunction e
583 isFunction other = False
587 %************************************************************************
589 \subsection{Free-To-Level Monad}
591 %************************************************************************
594 type LevelEnv = (FloatOutSwitches,
595 VarEnv Level, -- Domain is *post-cloned* TyVars and Ids
596 Subst, -- Domain is pre-cloned Ids; tracks the in-scope set
597 -- so that subtitution is capture-avoiding
598 IdEnv ([Var], LevelledExpr)) -- Domain is pre-cloned Ids
599 -- We clone let-bound variables so that they are still
600 -- distinct when floated out; hence the SubstEnv/IdEnv.
601 -- (see point 3 of the module overview comment).
602 -- We also use these envs when making a variable polymorphic
603 -- because we want to float it out past a big lambda.
605 -- The SubstEnv and IdEnv always implement the same mapping, but the
606 -- SubstEnv maps to CoreExpr and the IdEnv to LevelledExpr
607 -- Since the range is always a variable or type application,
608 -- there is never any difference between the two, but sadly
609 -- the types differ. The SubstEnv is used when substituting in
610 -- a variable's IdInfo; the IdEnv when we find a Var.
612 -- In addition the IdEnv records a list of tyvars free in the
613 -- type application, just so we don't have to call freeVars on
614 -- the type application repeatedly.
616 -- The domain of the both envs is *pre-cloned* Ids, though
618 -- The domain of the VarEnv Level is the *post-cloned* Ids
620 initialEnv :: FloatOutSwitches -> LevelEnv
621 initialEnv float_lams = (float_lams, emptyVarEnv, emptySubst, emptyVarEnv)
623 floatLams :: LevelEnv -> Bool
624 floatLams (FloatOutSw float_lams _, _, _, _) = float_lams
626 floatConsts :: LevelEnv -> Bool
627 floatConsts (FloatOutSw _ float_consts, _, _, _) = float_consts
629 extendLvlEnv :: LevelEnv -> [(Var,Level)] -> LevelEnv
630 -- Used when *not* cloning
631 extendLvlEnv (float_lams, lvl_env, subst, id_env) prs
633 foldl add_lvl lvl_env prs,
634 foldl del_subst subst prs,
635 foldl del_id id_env prs)
637 add_lvl env (v,l) = extendVarEnv env v l
638 del_subst env (v,_) = extendInScope env v
639 del_id env (v,_) = delVarEnv env v
640 -- We must remove any clone for this variable name in case of
641 -- shadowing. This bit me in the following case
642 -- (in nofib/real/gg/Spark.hs):
645 -- ... -> case e of wild {
646 -- ... -> ... wild ...
650 -- The inside occurrence of @wild@ was being replaced with @ds@,
651 -- incorrectly, because the SubstEnv was still lying around. Ouch!
654 -- extendCaseBndrLvlEnv adds the mapping case-bndr->scrut-var if it can
655 -- (see point 4 of the module overview comment)
656 extendCaseBndrLvlEnv (float_lams, lvl_env, subst, id_env) (Var scrut_var) case_bndr lvl
658 extendVarEnv lvl_env case_bndr lvl,
659 extendSubst subst case_bndr (DoneEx (Var scrut_var)),
660 extendVarEnv id_env case_bndr ([scrut_var], Var scrut_var))
662 extendCaseBndrLvlEnv env scrut case_bndr lvl
663 = extendLvlEnv env [(case_bndr,lvl)]
665 extendPolyLvlEnv dest_lvl (float_lams, lvl_env, subst, id_env) abs_vars bndr_pairs
667 foldl add_lvl lvl_env bndr_pairs,
668 foldl add_subst subst bndr_pairs,
669 foldl add_id id_env bndr_pairs)
671 add_lvl env (v,v') = extendVarEnv env v' dest_lvl
672 add_subst env (v,v') = extendSubst env v (DoneEx (mkVarApps (Var v') abs_vars))
673 add_id env (v,v') = extendVarEnv env v ((v':abs_vars), mkVarApps (Var v') abs_vars)
675 extendCloneLvlEnv lvl (float_lams, lvl_env, _, id_env) new_subst bndr_pairs
677 foldl add_lvl lvl_env bndr_pairs,
679 foldl add_id id_env bndr_pairs)
681 add_lvl env (v,v') = extendVarEnv env v' lvl
682 add_id env (v,v') = extendVarEnv env v ([v'], Var v')
685 maxIdLevel :: LevelEnv -> VarSet -> Level
686 maxIdLevel (_, lvl_env,_,id_env) var_set
687 = foldVarSet max_in tOP_LEVEL var_set
689 max_in in_var lvl = foldr max_out lvl (case lookupVarEnv id_env in_var of
690 Just (abs_vars, _) -> abs_vars
694 | isId out_var = case lookupVarEnv lvl_env out_var of
695 Just lvl' -> maxLvl lvl' lvl
697 | otherwise = lvl -- Ignore tyvars in *maxIdLevel*
699 lookupVar :: LevelEnv -> Id -> LevelledExpr
700 lookupVar (_, _, _, id_env) v = case lookupVarEnv id_env v of
701 Just (_, expr) -> expr
704 abstractVars :: Level -> LevelEnv -> VarSet -> [Var]
705 -- Find the variables in fvs, free vars of the target expresion,
706 -- whose level is greater than the destination level
707 -- These are the ones we are going to abstract out
708 abstractVars dest_lvl env fvs
709 = uniq (sortLt lt [var | fv <- varSetElems fvs, var <- absVarsOf dest_lvl env fv])
711 -- Sort the variables so we don't get
712 -- mixed-up tyvars and Ids; it's just messy
713 v1 `lt` v2 = case (isId v1, isId v2) of
714 (True, False) -> False
715 (False, True) -> True
716 other -> v1 < v2 -- Same family
718 uniq :: [Var] -> [Var]
719 -- Remove adjacent duplicates; the sort will have brought them together
720 uniq (v1:v2:vs) | v1 == v2 = uniq (v2:vs)
721 | otherwise = v1 : uniq (v2:vs)
724 absVarsOf :: Level -> LevelEnv -> Var -> [Var]
725 -- If f is free in the expression, and f maps to poly_f a b c in the
726 -- current substitution, then we must report a b c as candidate type
728 absVarsOf dest_lvl (_, lvl_env, _, id_env) v
730 = [zap av2 | av1 <- lookup_avs v, av2 <- add_tyvars av1, abstract_me av2]
733 = if abstract_me v then [v] else []
736 abstract_me v = case lookupVarEnv lvl_env v of
737 Just lvl -> dest_lvl `ltLvl` lvl
740 lookup_avs v = case lookupVarEnv id_env v of
741 Just (abs_vars, _) -> abs_vars
744 add_tyvars v | isId v = v : varSetElems (idFreeTyVars v)
747 -- We are going to lambda-abstract, so nuke any IdInfo,
748 -- and add the tyvars of the Id (if necessary)
749 zap v | isId v = WARN( workerExists (idWorkerInfo v) ||
750 not (isEmptyCoreRules (idSpecialisation v)),
751 text "absVarsOf: discarding info on" <+> ppr v )
752 setIdInfo v vanillaIdInfo
757 type LvlM result = UniqSM result
766 newPolyBndrs dest_lvl env abs_vars bndrs
767 = getUniquesUs `thenLvl` \ uniqs ->
769 new_bndrs = zipWith mk_poly_bndr bndrs uniqs
771 returnLvl (extendPolyLvlEnv dest_lvl env abs_vars (bndrs `zip` new_bndrs), new_bndrs)
773 mk_poly_bndr bndr uniq = mkSysLocal (_PK_ str) uniq poly_ty
775 str = "poly_" ++ occNameUserString (getOccName bndr)
776 poly_ty = mkPiTypes abs_vars (idType bndr)
780 -> [CoreBndr] -> Type -- Abstract wrt these bndrs
782 newLvlVar str vars body_ty
783 = getUniqueUs `thenLvl` \ uniq ->
784 returnUs (mkSysLocal (_PK_ str) uniq (mkPiTypes vars body_ty))
786 -- The deeply tiresome thing is that we have to apply the substitution
787 -- to the rules inside each Id. Grr. But it matters.
789 cloneVar :: TopLevelFlag -> LevelEnv -> Id -> Level -> Level -> LvlM (LevelEnv, Id)
790 cloneVar TopLevel env v ctxt_lvl dest_lvl
791 = returnUs (env, v) -- Don't clone top level things
792 cloneVar NotTopLevel env@(_,_,subst,_) v ctxt_lvl dest_lvl
794 getUs `thenLvl` \ us ->
796 (subst', v1) = substAndCloneId subst us v
797 v2 = zap_demand ctxt_lvl dest_lvl v1
798 env' = extendCloneLvlEnv dest_lvl env subst' [(v,v2)]
802 cloneRecVars :: TopLevelFlag -> LevelEnv -> [Id] -> Level -> Level -> LvlM (LevelEnv, [Id])
803 cloneRecVars TopLevel env vs ctxt_lvl dest_lvl
804 = returnUs (env, vs) -- Don't clone top level things
805 cloneRecVars NotTopLevel env@(_,_,subst,_) vs ctxt_lvl dest_lvl
806 = ASSERT( all isId vs )
807 getUs `thenLvl` \ us ->
809 (subst', vs1) = substAndCloneRecIds subst us vs
810 vs2 = map (zap_demand ctxt_lvl dest_lvl) vs1
811 env' = extendCloneLvlEnv dest_lvl env subst' (vs `zip` vs2)
815 -- VERY IMPORTANT: we must zap the demand info
816 -- if the thing is going to float out past a lambda
817 zap_demand dest_lvl ctxt_lvl id
818 | ctxt_lvl == dest_lvl = id -- Stays put
819 | otherwise = zapDemandIdInfo id -- Floats out