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, mkSysLocalUnencoded,
62 isOneShotLambda, zapDemandIdInfo,
63 idSpecialisation, idWorkerInfo, setIdInfo
65 import IdInfo ( workerExists, vanillaIdInfo, )
69 import Name ( getOccName )
70 import OccName ( occNameUserString )
71 import Type ( isUnLiftedType, Type )
72 import BasicTypes ( TopLevelFlag(..) )
74 import Util ( sortLt, isSingleton, count )
79 %************************************************************************
81 \subsection{Level numbers}
83 %************************************************************************
86 data Level = InlineCtxt -- A level that's used only for
87 -- the context parameter ctxt_lvl
88 | Level Int -- Level number of enclosing lambdas
89 Int -- Number of big-lambda and/or case expressions between
90 -- here and the nearest enclosing lambda
93 The {\em level number} on a (type-)lambda-bound variable is the
94 nesting depth of the (type-)lambda which binds it. The outermost lambda
95 has level 1, so (Level 0 0) means that the variable is bound outside any lambda.
97 On an expression, it's the maximum level number of its free
98 (type-)variables. On a let(rec)-bound variable, it's the level of its
99 RHS. On a case-bound variable, it's the number of enclosing lambdas.
101 Top-level variables: level~0. Those bound on the RHS of a top-level
102 definition but ``before'' a lambda; e.g., the \tr{x} in (levels shown
103 as ``subscripts'')...
105 a_0 = let b_? = ... in
106 x_1 = ... b ... in ...
109 The main function @lvlExpr@ carries a ``context level'' (@ctxt_lvl@).
110 That's meant to be the level number of the enclosing binder in the
111 final (floated) program. If the level number of a sub-expression is
112 less than that of the context, then it might be worth let-binding the
113 sub-expression so that it will indeed float.
115 If you can float to level @Level 0 0@ worth doing so because then your
116 allocation becomes static instead of dynamic. We always start with
122 @InlineCtxt@ very similar to @Level 0 0@, but is used for one purpose:
123 to say "don't float anything out of here". That's exactly what we
124 want for the body of an INLINE, where we don't want to float anything
125 out at all. See notes with lvlMFE below.
129 -- At one time I tried the effect of not float anything out of an InlineMe,
130 -- but it sometimes works badly. For example, consider PrelArr.done. It
131 -- has the form __inline (\d. e)
132 -- where e doesn't mention d. If we float this to
133 -- __inline (let x = e in \d. x)
134 -- things are bad. The inliner doesn't even inline it because it doesn't look
135 -- like a head-normal form. So it seems a lesser evil to let things float.
136 -- In SetLevels we do set the context to (Level 0 0) when we get to an InlineMe
137 -- which discourages floating out.
139 So the conclusion is: don't do any floating at all inside an InlineMe.
140 (In the above example, don't float the {x=e} out of the \d.)
142 One particular case is that of workers: we don't want to float the
143 call to the worker outside the wrapper, otherwise the worker might get
144 inlined into the floated expression, and an importing module won't see
148 type LevelledExpr = TaggedExpr Level
149 type LevelledBind = TaggedBind Level
151 tOP_LEVEL = Level 0 0
152 iNLINE_CTXT = InlineCtxt
154 incMajorLvl :: Level -> Level
155 -- For InlineCtxt we ignore any inc's; we don't want
156 -- to do any floating at all; see notes above
157 incMajorLvl InlineCtxt = InlineCtxt
158 incMajorLvl (Level major minor) = Level (major+1) 0
160 incMinorLvl :: Level -> Level
161 incMinorLvl InlineCtxt = InlineCtxt
162 incMinorLvl (Level major minor) = Level major (minor+1)
164 maxLvl :: Level -> Level -> Level
165 maxLvl InlineCtxt l2 = l2
166 maxLvl l1 InlineCtxt = l1
167 maxLvl l1@(Level maj1 min1) l2@(Level maj2 min2)
168 | (maj1 > maj2) || (maj1 == maj2 && min1 > min2) = l1
171 ltLvl :: Level -> Level -> Bool
172 ltLvl any_lvl InlineCtxt = False
173 ltLvl InlineCtxt (Level _ _) = True
174 ltLvl (Level maj1 min1) (Level maj2 min2)
175 = (maj1 < maj2) || (maj1 == maj2 && min1 < min2)
177 ltMajLvl :: Level -> Level -> Bool
178 -- Tells if one level belongs to a difft *lambda* level to another
179 ltMajLvl any_lvl InlineCtxt = False
180 ltMajLvl InlineCtxt (Level maj2 _) = 0 < maj2
181 ltMajLvl (Level maj1 _) (Level maj2 _) = maj1 < maj2
183 isTopLvl :: Level -> Bool
184 isTopLvl (Level 0 0) = True
185 isTopLvl other = False
187 isInlineCtxt :: Level -> Bool
188 isInlineCtxt InlineCtxt = True
189 isInlineCtxt other = False
191 instance Outputable Level where
192 ppr InlineCtxt = text "<INLINE>"
193 ppr (Level maj min) = hcat [ char '<', int maj, char ',', int min, char '>' ]
195 instance Eq Level where
196 InlineCtxt == InlineCtxt = True
197 (Level maj1 min1) == (Level maj2 min2) = maj1==maj2 && min1==min2
202 %************************************************************************
204 \subsection{Main level-setting code}
206 %************************************************************************
209 setLevels :: FloatOutSwitches
214 setLevels float_lams binds us
215 = initLvl us (do_them binds)
217 -- "do_them"'s main business is to thread the monad along
218 -- It gives each top binding the same empty envt, because
219 -- things unbound in the envt have level number zero implicitly
220 do_them :: [CoreBind] -> LvlM [LevelledBind]
222 do_them [] = returnLvl []
224 = lvlTopBind init_env b `thenLvl` \ (lvld_bind, _) ->
225 do_them bs `thenLvl` \ lvld_binds ->
226 returnLvl (lvld_bind : lvld_binds)
228 init_env = initialEnv float_lams
230 lvlTopBind env (NonRec binder rhs)
231 = lvlBind TopLevel tOP_LEVEL env (AnnNonRec binder (freeVars rhs))
232 -- Rhs can have no free vars!
234 lvlTopBind env (Rec pairs)
235 = lvlBind TopLevel tOP_LEVEL env (AnnRec [(b,freeVars rhs) | (b,rhs) <- pairs])
238 %************************************************************************
240 \subsection{Setting expression levels}
242 %************************************************************************
245 lvlExpr :: Level -- ctxt_lvl: Level of enclosing expression
246 -> LevelEnv -- Level of in-scope names/tyvars
247 -> CoreExprWithFVs -- input expression
248 -> LvlM LevelledExpr -- Result expression
251 The @ctxt_lvl@ is, roughly, the level of the innermost enclosing
252 binder. Here's an example
254 v = \x -> ...\y -> let r = case (..x..) of
258 When looking at the rhs of @r@, @ctxt_lvl@ will be 1 because that's
259 the level of @r@, even though it's inside a level-2 @\y@. It's
260 important that @ctxt_lvl@ is 1 and not 2 in @r@'s rhs, because we
261 don't want @lvlExpr@ to turn the scrutinee of the @case@ into an MFE
262 --- because it isn't a *maximal* free expression.
264 If there were another lambda in @r@'s rhs, it would get level-2 as well.
267 lvlExpr _ _ (_, AnnType ty) = returnLvl (Type ty)
268 lvlExpr _ env (_, AnnVar v) = returnLvl (lookupVar env v)
269 lvlExpr _ env (_, AnnLit lit) = returnLvl (Lit lit)
271 lvlExpr ctxt_lvl env (_, AnnApp fun arg)
272 = lvl_fun fun `thenLvl` \ fun' ->
273 lvlMFE False ctxt_lvl env arg `thenLvl` \ arg' ->
274 returnLvl (App fun' arg')
276 lvl_fun (_, AnnCase _ _ _) = lvlMFE True ctxt_lvl env fun
277 lvl_fun other = lvlExpr ctxt_lvl env fun
278 -- We don't do MFE on partial applications generally,
279 -- but we do if the function is big and hairy, like a case
281 lvlExpr ctxt_lvl env (_, AnnNote InlineMe expr)
282 -- Don't float anything out of an InlineMe; hence the iNLINE_CTXT
283 = lvlExpr iNLINE_CTXT env expr `thenLvl` \ expr' ->
284 returnLvl (Note InlineMe expr')
286 lvlExpr ctxt_lvl env (_, AnnNote note expr)
287 = lvlExpr ctxt_lvl env expr `thenLvl` \ expr' ->
288 returnLvl (Note note expr')
290 -- We don't split adjacent lambdas. That is, given
292 -- we don't float to give
293 -- \x -> let v = x+y in \y -> (v,y)
294 -- Why not? Because partial applications are fairly rare, and splitting
295 -- lambdas makes them more expensive.
297 lvlExpr ctxt_lvl env expr@(_, AnnLam bndr rhs)
298 = lvlMFE True new_lvl new_env body `thenLvl` \ new_body ->
299 returnLvl (mkLams new_bndrs new_body)
301 (bndrs, body) = collectAnnBndrs expr
302 (new_lvl, new_bndrs) = lvlLamBndrs ctxt_lvl bndrs
303 new_env = extendLvlEnv env new_bndrs
304 -- At one time we called a special verion of collectBinders,
305 -- which ignored coercions, because we don't want to split
306 -- a lambda like this (\x -> coerce t (\s -> ...))
307 -- This used to happen quite a bit in state-transformer programs,
308 -- but not nearly so much now non-recursive newtypes are transparent.
309 -- [See SetLevels rev 1.50 for a version with this approach.]
311 lvlExpr ctxt_lvl env (_, AnnLet bind body)
312 = lvlBind NotTopLevel ctxt_lvl env bind `thenLvl` \ (bind', new_env) ->
313 lvlExpr ctxt_lvl new_env body `thenLvl` \ body' ->
314 returnLvl (Let bind' body')
316 lvlExpr ctxt_lvl env (_, AnnCase expr case_bndr alts)
317 = lvlMFE True ctxt_lvl env expr `thenLvl` \ expr' ->
319 alts_env = extendCaseBndrLvlEnv env expr' case_bndr incd_lvl
321 mapLvl (lvl_alt alts_env) alts `thenLvl` \ alts' ->
322 returnLvl (Case expr' (case_bndr, incd_lvl) alts')
324 incd_lvl = incMinorLvl ctxt_lvl
326 lvl_alt alts_env (con, bs, rhs)
327 = lvlMFE True incd_lvl new_env rhs `thenLvl` \ rhs' ->
328 returnLvl (con, bs', rhs')
330 bs' = [ (b, incd_lvl) | b <- bs ]
331 new_env = extendLvlEnv alts_env bs'
334 @lvlMFE@ is just like @lvlExpr@, except that it might let-bind
335 the expression, so that it can itself be floated.
338 lvlMFE :: Bool -- True <=> strict context [body of case or let]
339 -> Level -- Level of innermost enclosing lambda/tylam
340 -> LevelEnv -- Level of in-scope names/tyvars
341 -> CoreExprWithFVs -- input expression
342 -> LvlM LevelledExpr -- Result expression
344 lvlMFE strict_ctxt ctxt_lvl env (_, AnnType ty)
345 = returnLvl (Type ty)
347 lvlMFE strict_ctxt ctxt_lvl env ann_expr@(fvs, _)
348 | isUnLiftedType ty -- Can't let-bind it
349 || isInlineCtxt ctxt_lvl -- Don't float out of an __inline__ context
350 || exprIsTrivial expr -- Never float if it's trivial
351 || not good_destination
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 -- A decision to float entails let-binding this thing, and we only do
367 -- that if we'll escape a value lambda, or will go to the top level.
369 | dest_lvl `ltMajLvl` ctxt_lvl -- Escapes a value lambda
370 = not (exprIsCheap expr) || isTopLvl dest_lvl
371 -- Even if it escapes a value lambda, we only
372 -- float if it's not cheap (unless it'll get all the
373 -- way to the top). I've seen cases where we
374 -- float dozens of tiny free expressions, which cost
375 -- more to allocate than to evaluate.
376 -- NB: exprIsCheap is also true of bottom expressions, which
377 -- is good; we don't want to share them
379 -- It's only Really Bad to float a cheap expression out of a
380 -- strict context, because that builds a thunk that otherwise
381 -- would never be built. So another alternative would be to
383 -- || (strict_ctxt && not (exprIsBottom expr))
384 -- to the condition above. We should really try this out.
386 | otherwise -- Does not escape a value lambda
387 = isTopLvl dest_lvl -- Only float if we are going to the top level
388 && floatConsts env -- and the floatConsts flag is on
389 && not strict_ctxt -- Don't float from a strict context
390 -- We are keen to float something to the top level, even if it does not
391 -- escape a lambda, because then it needs no allocation. But it's controlled
392 -- by a flag, because doing this too early loses opportunities for RULES
393 -- which (needless to say) are important in some nofib programs
394 -- (gcd is an example).
397 -- concat = /\ a -> foldr ..a.. (++) []
398 -- was getting turned into
399 -- concat = /\ a -> lvl a
400 -- lvl = /\ a -> foldr ..a.. (++) []
401 -- which is pretty stupid. Hence the strict_ctxt test
405 %************************************************************************
407 \subsection{Bindings}
409 %************************************************************************
411 The binding stuff works for top level too.
414 lvlBind :: TopLevelFlag -- Used solely to decide whether to clone
415 -> Level -- Context level; might be Top even for bindings nested in the RHS
416 -- of a top level binding
419 -> LvlM (LevelledBind, LevelEnv)
421 lvlBind top_lvl ctxt_lvl env (AnnNonRec bndr rhs@(rhs_fvs,_))
422 | isInlineCtxt ctxt_lvl -- Don't do anything inside InlineMe
423 = lvlExpr ctxt_lvl env rhs `thenLvl` \ rhs' ->
424 returnLvl (NonRec (bndr, ctxt_lvl) rhs', env)
427 = -- No type abstraction; clone existing binder
428 lvlExpr dest_lvl env rhs `thenLvl` \ rhs' ->
429 cloneVar top_lvl env bndr ctxt_lvl dest_lvl `thenLvl` \ (env', bndr') ->
430 returnLvl (NonRec (bndr', dest_lvl) rhs', env')
433 = -- Yes, type abstraction; create a new binder, extend substitution, etc
434 lvlFloatRhs abs_vars dest_lvl env rhs `thenLvl` \ rhs' ->
435 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (env', [bndr']) ->
436 returnLvl (NonRec (bndr', dest_lvl) rhs', env')
439 bind_fvs = rhs_fvs `unionVarSet` idFreeVars bndr
440 abs_vars = abstractVars dest_lvl env bind_fvs
442 dest_lvl | isUnLiftedType (idType bndr) = destLevel env bind_fvs False `maxLvl` Level 1 0
443 | otherwise = destLevel env bind_fvs (isFunction rhs)
444 -- Hack alert! We do have some unlifted bindings, for cheap primops, and
445 -- it is ok to float them out; but not to the top level. If they would otherwise
446 -- go to the top level, we pin them inside the topmost lambda
451 lvlBind top_lvl ctxt_lvl env (AnnRec pairs)
452 | isInlineCtxt ctxt_lvl -- Don't do anything inside InlineMe
453 = mapLvl (lvlExpr ctxt_lvl env) rhss `thenLvl` \ rhss' ->
454 returnLvl (Rec ((bndrs `zip` repeat ctxt_lvl) `zip` rhss'), env)
457 = cloneRecVars top_lvl env bndrs ctxt_lvl dest_lvl `thenLvl` \ (new_env, new_bndrs) ->
458 mapLvl (lvlExpr ctxt_lvl new_env) rhss `thenLvl` \ new_rhss ->
459 returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env)
461 | isSingleton pairs && count isId abs_vars > 1
462 = -- Special case for self recursion where there are
463 -- several variables carried around: build a local loop:
464 -- poly_f = \abs_vars. \lam_vars . letrec f = \lam_vars. rhs in f lam_vars
465 -- This just makes the closures a bit smaller. If we don't do
466 -- this, allocation rises significantly on some programs
468 -- We could elaborate it for the case where there are several
469 -- mutually functions, but it's quite a bit more complicated
471 -- This all seems a bit ad hoc -- sigh
473 (bndr,rhs) = head pairs
474 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
475 rhs_env = extendLvlEnv env abs_vars_w_lvls
477 cloneVar NotTopLevel rhs_env bndr rhs_lvl rhs_lvl `thenLvl` \ (rhs_env', new_bndr) ->
479 (lam_bndrs, rhs_body) = collectAnnBndrs rhs
480 (body_lvl, new_lam_bndrs) = lvlLamBndrs rhs_lvl lam_bndrs
481 body_env = extendLvlEnv rhs_env' new_lam_bndrs
483 lvlExpr body_lvl body_env rhs_body `thenLvl` \ new_rhs_body ->
484 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (poly_env, [poly_bndr]) ->
485 returnLvl (Rec [((poly_bndr,dest_lvl), mkLams abs_vars_w_lvls $
486 mkLams new_lam_bndrs $
487 Let (Rec [((new_bndr,rhs_lvl), mkLams new_lam_bndrs new_rhs_body)])
488 (mkVarApps (Var new_bndr) lam_bndrs))],
491 | otherwise -- Non-null abs_vars
492 = newPolyBndrs dest_lvl env abs_vars bndrs `thenLvl` \ (new_env, new_bndrs) ->
493 mapLvl (lvlFloatRhs abs_vars dest_lvl new_env) rhss `thenLvl` \ new_rhss ->
494 returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env)
497 (bndrs,rhss) = unzip pairs
499 -- Finding the free vars of the binding group is annoying
500 bind_fvs = (unionVarSets [ idFreeVars bndr `unionVarSet` rhs_fvs
501 | (bndr, (rhs_fvs,_)) <- pairs])
505 dest_lvl = destLevel env bind_fvs (all isFunction rhss)
506 abs_vars = abstractVars dest_lvl env bind_fvs
508 ----------------------------------------------------
509 -- Three help functons for the type-abstraction case
511 lvlFloatRhs abs_vars dest_lvl env rhs
512 = lvlExpr rhs_lvl rhs_env rhs `thenLvl` \ rhs' ->
513 returnLvl (mkLams abs_vars_w_lvls rhs')
515 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
516 rhs_env = extendLvlEnv env abs_vars_w_lvls
520 %************************************************************************
522 \subsection{Deciding floatability}
524 %************************************************************************
527 lvlLamBndrs :: Level -> [CoreBndr] -> (Level, [(CoreBndr, Level)])
528 -- Compute the levels for the binders of a lambda group
529 -- The binders returned are exactly the same as the ones passed,
530 -- but they are now paired with a level
534 lvlLamBndrs lvl bndrs
535 = go (incMinorLvl lvl)
536 False -- Havn't bumped major level in this group
539 go old_lvl bumped_major rev_lvld_bndrs (bndr:bndrs)
540 | isId bndr && -- Go to the next major level if this is a value binder,
541 not bumped_major && -- and we havn't already gone to the next level (one jump per group)
542 not (isOneShotLambda bndr) -- and it isn't a one-shot lambda
543 = go new_lvl True ((bndr,new_lvl) : rev_lvld_bndrs) bndrs
546 = go old_lvl bumped_major ((bndr,old_lvl) : rev_lvld_bndrs) bndrs
549 new_lvl = incMajorLvl old_lvl
551 go old_lvl _ rev_lvld_bndrs []
552 = (old_lvl, reverse rev_lvld_bndrs)
553 -- a lambda like this (\x -> coerce t (\s -> ...))
554 -- This happens quite a bit in state-transformer programs
558 -- Destintion level is the max Id level of the expression
559 -- (We'll abstract the type variables, if any.)
560 destLevel :: LevelEnv -> VarSet -> Bool -> Level
561 destLevel env fvs is_function
563 && is_function = tOP_LEVEL -- Send functions to top level; see
564 -- the comments with isFunction
565 | otherwise = maxIdLevel env fvs
567 isFunction :: CoreExprWithFVs -> Bool
568 -- The idea here is that we want to float *functions* to
569 -- the top level. This saves no work, but
570 -- (a) it can make the host function body a lot smaller,
571 -- and hence inlinable.
572 -- (b) it can also save allocation when the function is recursive:
573 -- h = \x -> letrec f = \y -> ...f...y...x...
576 -- f = \x y -> ...(f x)...y...x...
578 -- No allocation for f now.
579 -- We may only want to do this if there are sufficiently few free
580 -- variables. We certainly only want to do it for values, and not for
581 -- constructors. So the simple thing is just to look for lambdas
582 isFunction (_, AnnLam b e) | isId b = True
583 | otherwise = isFunction e
584 isFunction (_, AnnNote n e) = isFunction e
585 isFunction other = False
589 %************************************************************************
591 \subsection{Free-To-Level Monad}
593 %************************************************************************
596 type LevelEnv = (FloatOutSwitches,
597 VarEnv Level, -- Domain is *post-cloned* TyVars and Ids
598 Subst, -- Domain is pre-cloned Ids; tracks the in-scope set
599 -- so that subtitution is capture-avoiding
600 IdEnv ([Var], LevelledExpr)) -- Domain is pre-cloned Ids
601 -- We clone let-bound variables so that they are still
602 -- distinct when floated out; hence the SubstEnv/IdEnv.
603 -- (see point 3 of the module overview comment).
604 -- We also use these envs when making a variable polymorphic
605 -- because we want to float it out past a big lambda.
607 -- The SubstEnv and IdEnv always implement the same mapping, but the
608 -- SubstEnv maps to CoreExpr and the IdEnv to LevelledExpr
609 -- Since the range is always a variable or type application,
610 -- there is never any difference between the two, but sadly
611 -- the types differ. The SubstEnv is used when substituting in
612 -- a variable's IdInfo; the IdEnv when we find a Var.
614 -- In addition the IdEnv records a list of tyvars free in the
615 -- type application, just so we don't have to call freeVars on
616 -- the type application repeatedly.
618 -- The domain of the both envs is *pre-cloned* Ids, though
620 -- The domain of the VarEnv Level is the *post-cloned* Ids
622 initialEnv :: FloatOutSwitches -> LevelEnv
623 initialEnv float_lams = (float_lams, emptyVarEnv, emptySubst, emptyVarEnv)
625 floatLams :: LevelEnv -> Bool
626 floatLams (FloatOutSw float_lams _, _, _, _) = float_lams
628 floatConsts :: LevelEnv -> Bool
629 floatConsts (FloatOutSw _ float_consts, _, _, _) = float_consts
631 extendLvlEnv :: LevelEnv -> [(Var,Level)] -> LevelEnv
632 -- Used when *not* cloning
633 extendLvlEnv (float_lams, lvl_env, subst, id_env) prs
635 foldl add_lvl lvl_env prs,
636 foldl del_subst subst prs,
637 foldl del_id id_env prs)
639 add_lvl env (v,l) = extendVarEnv env v l
640 del_subst env (v,_) = extendInScope env v
641 del_id env (v,_) = delVarEnv env v
642 -- We must remove any clone for this variable name in case of
643 -- shadowing. This bit me in the following case
644 -- (in nofib/real/gg/Spark.hs):
647 -- ... -> case e of wild {
648 -- ... -> ... wild ...
652 -- The inside occurrence of @wild@ was being replaced with @ds@,
653 -- incorrectly, because the SubstEnv was still lying around. Ouch!
656 -- extendCaseBndrLvlEnv adds the mapping case-bndr->scrut-var if it can
657 -- (see point 4 of the module overview comment)
658 extendCaseBndrLvlEnv (float_lams, lvl_env, subst, id_env) (Var scrut_var) case_bndr lvl
660 extendVarEnv lvl_env case_bndr lvl,
661 extendSubst subst case_bndr (DoneEx (Var scrut_var)),
662 extendVarEnv id_env case_bndr ([scrut_var], Var scrut_var))
664 extendCaseBndrLvlEnv env scrut case_bndr lvl
665 = extendLvlEnv env [(case_bndr,lvl)]
667 extendPolyLvlEnv dest_lvl (float_lams, lvl_env, subst, id_env) abs_vars bndr_pairs
669 foldl add_lvl lvl_env bndr_pairs,
670 foldl add_subst subst bndr_pairs,
671 foldl add_id id_env bndr_pairs)
673 add_lvl env (v,v') = extendVarEnv env v' dest_lvl
674 add_subst env (v,v') = extendSubst env v (DoneEx (mkVarApps (Var v') abs_vars))
675 add_id env (v,v') = extendVarEnv env v ((v':abs_vars), mkVarApps (Var v') abs_vars)
677 extendCloneLvlEnv lvl (float_lams, lvl_env, _, id_env) new_subst bndr_pairs
679 foldl add_lvl lvl_env bndr_pairs,
681 foldl add_id id_env bndr_pairs)
683 add_lvl env (v,v') = extendVarEnv env v' lvl
684 add_id env (v,v') = extendVarEnv env v ([v'], Var v')
687 maxIdLevel :: LevelEnv -> VarSet -> Level
688 maxIdLevel (_, lvl_env,_,id_env) var_set
689 = foldVarSet max_in tOP_LEVEL var_set
691 max_in in_var lvl = foldr max_out lvl (case lookupVarEnv id_env in_var of
692 Just (abs_vars, _) -> abs_vars
696 | isId out_var = case lookupVarEnv lvl_env out_var of
697 Just lvl' -> maxLvl lvl' lvl
699 | otherwise = lvl -- Ignore tyvars in *maxIdLevel*
701 lookupVar :: LevelEnv -> Id -> LevelledExpr
702 lookupVar (_, _, _, id_env) v = case lookupVarEnv id_env v of
703 Just (_, expr) -> expr
706 abstractVars :: Level -> LevelEnv -> VarSet -> [Var]
707 -- Find the variables in fvs, free vars of the target expresion,
708 -- whose level is greater than the destination level
709 -- These are the ones we are going to abstract out
710 abstractVars dest_lvl env fvs
711 = uniq (sortLt lt [var | fv <- varSetElems fvs, var <- absVarsOf dest_lvl env fv])
713 -- Sort the variables so we don't get
714 -- mixed-up tyvars and Ids; it's just messy
715 v1 `lt` v2 = case (isId v1, isId v2) of
716 (True, False) -> False
717 (False, True) -> True
718 other -> v1 < v2 -- Same family
720 uniq :: [Var] -> [Var]
721 -- Remove adjacent duplicates; the sort will have brought them together
722 uniq (v1:v2:vs) | v1 == v2 = uniq (v2:vs)
723 | otherwise = v1 : uniq (v2:vs)
726 absVarsOf :: Level -> LevelEnv -> Var -> [Var]
727 -- If f is free in the expression, and f maps to poly_f a b c in the
728 -- current substitution, then we must report a b c as candidate type
730 absVarsOf dest_lvl (_, lvl_env, _, id_env) v
732 = [zap av2 | av1 <- lookup_avs v, av2 <- add_tyvars av1, abstract_me av2]
735 = if abstract_me v then [v] else []
738 abstract_me v = case lookupVarEnv lvl_env v of
739 Just lvl -> dest_lvl `ltLvl` lvl
742 lookup_avs v = case lookupVarEnv id_env v of
743 Just (abs_vars, _) -> abs_vars
746 add_tyvars v | isId v = v : varSetElems (idFreeTyVars v)
749 -- We are going to lambda-abstract, so nuke any IdInfo,
750 -- and add the tyvars of the Id (if necessary)
751 zap v | isId v = WARN( workerExists (idWorkerInfo v) ||
752 not (isEmptyCoreRules (idSpecialisation v)),
753 text "absVarsOf: discarding info on" <+> ppr v )
754 setIdInfo v vanillaIdInfo
759 type LvlM result = UniqSM result
768 newPolyBndrs dest_lvl env abs_vars bndrs
769 = getUniquesUs `thenLvl` \ uniqs ->
771 new_bndrs = zipWith mk_poly_bndr bndrs uniqs
773 returnLvl (extendPolyLvlEnv dest_lvl env abs_vars (bndrs `zip` new_bndrs), new_bndrs)
775 mk_poly_bndr bndr uniq = mkSysLocalUnencoded (mkFastString str) uniq poly_ty
777 str = "poly_" ++ occNameUserString (getOccName bndr)
778 poly_ty = mkPiTypes abs_vars (idType bndr)
782 -> [CoreBndr] -> Type -- Abstract wrt these bndrs
784 newLvlVar str vars body_ty
785 = getUniqueUs `thenLvl` \ uniq ->
786 returnUs (mkSysLocalUnencoded (mkFastString str) uniq (mkPiTypes vars body_ty))
788 -- The deeply tiresome thing is that we have to apply the substitution
789 -- to the rules inside each Id. Grr. But it matters.
791 cloneVar :: TopLevelFlag -> LevelEnv -> Id -> Level -> Level -> LvlM (LevelEnv, Id)
792 cloneVar TopLevel env v ctxt_lvl dest_lvl
793 = returnUs (env, v) -- Don't clone top level things
794 cloneVar NotTopLevel env@(_,_,subst,_) v ctxt_lvl dest_lvl
796 getUs `thenLvl` \ us ->
798 (subst', v1) = substAndCloneId subst us v
799 v2 = zap_demand ctxt_lvl dest_lvl v1
800 env' = extendCloneLvlEnv dest_lvl env subst' [(v,v2)]
804 cloneRecVars :: TopLevelFlag -> LevelEnv -> [Id] -> Level -> Level -> LvlM (LevelEnv, [Id])
805 cloneRecVars TopLevel env vs ctxt_lvl dest_lvl
806 = returnUs (env, vs) -- Don't clone top level things
807 cloneRecVars NotTopLevel env@(_,_,subst,_) vs ctxt_lvl dest_lvl
808 = ASSERT( all isId vs )
809 getUs `thenLvl` \ us ->
811 (subst', vs1) = substAndCloneRecIds subst us vs
812 vs2 = map (zap_demand ctxt_lvl dest_lvl) vs1
813 env' = extendCloneLvlEnv dest_lvl env subst' (vs `zip` vs2)
817 -- VERY IMPORTANT: we must zap the demand info
818 -- if the thing is going to float out past a lambda
819 zap_demand dest_lvl ctxt_lvl id
820 | ctxt_lvl == dest_lvl = id -- Stays put
821 | otherwise = zapDemandIdInfo id -- Floats out