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.
49 LevelledBind, LevelledExpr,
51 incMinorLvl, ltMajLvl, ltLvl, isTopLvl, isInlineCtxt
54 #include "HsVersions.h"
58 import CmdLineOpts ( FloatOutSwitches(..) )
59 import CoreUtils ( exprType, exprIsTrivial, exprIsCheap, mkPiTypes )
60 import CoreFVs -- all of it
62 import Id ( Id, idType, mkSysLocalUnencoded,
63 isOneShotLambda, zapDemandIdInfo,
64 idSpecialisation, idWorkerInfo, setIdInfo
66 import IdInfo ( workerExists, vanillaIdInfo, )
70 import Name ( getOccName )
71 import OccName ( occNameUserString )
72 import Type ( isUnLiftedType, Type )
73 import BasicTypes ( TopLevelFlag(..) )
75 import Util ( sortLt, isSingleton, count )
80 %************************************************************************
82 \subsection{Level numbers}
84 %************************************************************************
87 data Level = InlineCtxt -- A level that's used only for
88 -- the context parameter ctxt_lvl
89 | Level Int -- Level number of enclosing lambdas
90 Int -- Number of big-lambda and/or case expressions between
91 -- here and the nearest enclosing lambda
94 The {\em level number} on a (type-)lambda-bound variable is the
95 nesting depth of the (type-)lambda which binds it. The outermost lambda
96 has level 1, so (Level 0 0) means that the variable is bound outside any lambda.
98 On an expression, it's the maximum level number of its free
99 (type-)variables. On a let(rec)-bound variable, it's the level of its
100 RHS. On a case-bound variable, it's the number of enclosing lambdas.
102 Top-level variables: level~0. Those bound on the RHS of a top-level
103 definition but ``before'' a lambda; e.g., the \tr{x} in (levels shown
104 as ``subscripts'')...
106 a_0 = let b_? = ... in
107 x_1 = ... b ... in ...
110 The main function @lvlExpr@ carries a ``context level'' (@ctxt_lvl@).
111 That's meant to be the level number of the enclosing binder in the
112 final (floated) program. If the level number of a sub-expression is
113 less than that of the context, then it might be worth let-binding the
114 sub-expression so that it will indeed float.
116 If you can float to level @Level 0 0@ worth doing so because then your
117 allocation becomes static instead of dynamic. We always start with
123 @InlineCtxt@ very similar to @Level 0 0@, but is used for one purpose:
124 to say "don't float anything out of here". That's exactly what we
125 want for the body of an INLINE, where we don't want to float anything
126 out at all. See notes with lvlMFE below.
130 -- At one time I tried the effect of not float anything out of an InlineMe,
131 -- but it sometimes works badly. For example, consider PrelArr.done. It
132 -- has the form __inline (\d. e)
133 -- where e doesn't mention d. If we float this to
134 -- __inline (let x = e in \d. x)
135 -- things are bad. The inliner doesn't even inline it because it doesn't look
136 -- like a head-normal form. So it seems a lesser evil to let things float.
137 -- In SetLevels we do set the context to (Level 0 0) when we get to an InlineMe
138 -- which discourages floating out.
140 So the conclusion is: don't do any floating at all inside an InlineMe.
141 (In the above example, don't float the {x=e} out of the \d.)
143 One particular case is that of workers: we don't want to float the
144 call to the worker outside the wrapper, otherwise the worker might get
145 inlined into the floated expression, and an importing module won't see
149 type LevelledExpr = TaggedExpr Level
150 type LevelledBind = TaggedBind Level
152 tOP_LEVEL = Level 0 0
153 iNLINE_CTXT = InlineCtxt
155 incMajorLvl :: Level -> Level
156 -- For InlineCtxt we ignore any inc's; we don't want
157 -- to do any floating at all; see notes above
158 incMajorLvl InlineCtxt = InlineCtxt
159 incMajorLvl (Level major minor) = Level (major+1) 0
161 incMinorLvl :: Level -> Level
162 incMinorLvl InlineCtxt = InlineCtxt
163 incMinorLvl (Level major minor) = Level major (minor+1)
165 maxLvl :: Level -> Level -> Level
166 maxLvl InlineCtxt l2 = l2
167 maxLvl l1 InlineCtxt = l1
168 maxLvl l1@(Level maj1 min1) l2@(Level maj2 min2)
169 | (maj1 > maj2) || (maj1 == maj2 && min1 > min2) = l1
172 ltLvl :: Level -> Level -> Bool
173 ltLvl any_lvl InlineCtxt = False
174 ltLvl InlineCtxt (Level _ _) = True
175 ltLvl (Level maj1 min1) (Level maj2 min2)
176 = (maj1 < maj2) || (maj1 == maj2 && min1 < min2)
178 ltMajLvl :: Level -> Level -> Bool
179 -- Tells if one level belongs to a difft *lambda* level to another
180 ltMajLvl any_lvl InlineCtxt = False
181 ltMajLvl InlineCtxt (Level maj2 _) = 0 < maj2
182 ltMajLvl (Level maj1 _) (Level maj2 _) = maj1 < maj2
184 isTopLvl :: Level -> Bool
185 isTopLvl (Level 0 0) = True
186 isTopLvl other = False
188 isInlineCtxt :: Level -> Bool
189 isInlineCtxt InlineCtxt = True
190 isInlineCtxt other = False
192 instance Outputable Level where
193 ppr InlineCtxt = text "<INLINE>"
194 ppr (Level maj min) = hcat [ char '<', int maj, char ',', int min, char '>' ]
196 instance Eq Level where
197 InlineCtxt == InlineCtxt = True
198 (Level maj1 min1) == (Level maj2 min2) = maj1==maj2 && min1==min2
203 %************************************************************************
205 \subsection{Main level-setting code}
207 %************************************************************************
210 setLevels :: FloatOutSwitches
215 setLevels float_lams binds us
216 = initLvl us (do_them binds)
218 -- "do_them"'s main business is to thread the monad along
219 -- It gives each top binding the same empty envt, because
220 -- things unbound in the envt have level number zero implicitly
221 do_them :: [CoreBind] -> LvlM [LevelledBind]
223 do_them [] = returnLvl []
225 = lvlTopBind init_env b `thenLvl` \ (lvld_bind, _) ->
226 do_them bs `thenLvl` \ lvld_binds ->
227 returnLvl (lvld_bind : lvld_binds)
229 init_env = initialEnv float_lams
231 lvlTopBind env (NonRec binder rhs)
232 = lvlBind TopLevel tOP_LEVEL env (AnnNonRec binder (freeVars rhs))
233 -- Rhs can have no free vars!
235 lvlTopBind env (Rec pairs)
236 = lvlBind TopLevel tOP_LEVEL env (AnnRec [(b,freeVars rhs) | (b,rhs) <- pairs])
239 %************************************************************************
241 \subsection{Setting expression levels}
243 %************************************************************************
246 lvlExpr :: Level -- ctxt_lvl: Level of enclosing expression
247 -> LevelEnv -- Level of in-scope names/tyvars
248 -> CoreExprWithFVs -- input expression
249 -> LvlM LevelledExpr -- Result expression
252 The @ctxt_lvl@ is, roughly, the level of the innermost enclosing
253 binder. Here's an example
255 v = \x -> ...\y -> let r = case (..x..) of
259 When looking at the rhs of @r@, @ctxt_lvl@ will be 1 because that's
260 the level of @r@, even though it's inside a level-2 @\y@. It's
261 important that @ctxt_lvl@ is 1 and not 2 in @r@'s rhs, because we
262 don't want @lvlExpr@ to turn the scrutinee of the @case@ into an MFE
263 --- because it isn't a *maximal* free expression.
265 If there were another lambda in @r@'s rhs, it would get level-2 as well.
268 lvlExpr _ _ (_, AnnType ty) = returnLvl (Type ty)
269 lvlExpr _ env (_, AnnVar v) = returnLvl (lookupVar env v)
270 lvlExpr _ env (_, AnnLit lit) = returnLvl (Lit lit)
272 lvlExpr ctxt_lvl env (_, AnnApp fun arg)
273 = lvl_fun fun `thenLvl` \ fun' ->
274 lvlMFE False ctxt_lvl env arg `thenLvl` \ arg' ->
275 returnLvl (App fun' arg')
277 lvl_fun (_, AnnCase _ _ _) = lvlMFE True ctxt_lvl env fun
278 lvl_fun other = lvlExpr ctxt_lvl env fun
279 -- We don't do MFE on partial applications generally,
280 -- but we do if the function is big and hairy, like a case
282 lvlExpr ctxt_lvl env (_, AnnNote InlineMe expr)
283 -- Don't float anything out of an InlineMe; hence the iNLINE_CTXT
284 = lvlExpr iNLINE_CTXT env expr `thenLvl` \ expr' ->
285 returnLvl (Note InlineMe expr')
287 lvlExpr ctxt_lvl env (_, AnnNote note expr)
288 = lvlExpr ctxt_lvl env expr `thenLvl` \ expr' ->
289 returnLvl (Note note expr')
291 -- We don't split adjacent lambdas. That is, given
293 -- we don't float to give
294 -- \x -> let v = x+y in \y -> (v,y)
295 -- Why not? Because partial applications are fairly rare, and splitting
296 -- lambdas makes them more expensive.
298 lvlExpr ctxt_lvl env expr@(_, AnnLam bndr rhs)
299 = lvlMFE True new_lvl new_env body `thenLvl` \ new_body ->
300 returnLvl (mkLams new_bndrs new_body)
302 (bndrs, body) = collectAnnBndrs expr
303 (new_lvl, new_bndrs) = lvlLamBndrs ctxt_lvl bndrs
304 new_env = extendLvlEnv env new_bndrs
305 -- At one time we called a special verion of collectBinders,
306 -- which ignored coercions, because we don't want to split
307 -- a lambda like this (\x -> coerce t (\s -> ...))
308 -- This used to happen quite a bit in state-transformer programs,
309 -- but not nearly so much now non-recursive newtypes are transparent.
310 -- [See SetLevels rev 1.50 for a version with this approach.]
312 lvlExpr ctxt_lvl env (_, AnnLet bind body)
313 = lvlBind NotTopLevel ctxt_lvl env bind `thenLvl` \ (bind', new_env) ->
314 lvlExpr ctxt_lvl new_env body `thenLvl` \ body' ->
315 returnLvl (Let bind' body')
317 lvlExpr ctxt_lvl env (_, AnnCase expr case_bndr alts)
318 = lvlMFE True ctxt_lvl env expr `thenLvl` \ expr' ->
320 alts_env = extendCaseBndrLvlEnv env expr' case_bndr incd_lvl
322 mapLvl (lvl_alt alts_env) alts `thenLvl` \ alts' ->
323 returnLvl (Case expr' (TB case_bndr incd_lvl) alts')
325 incd_lvl = incMinorLvl ctxt_lvl
327 lvl_alt alts_env (con, bs, rhs)
328 = lvlMFE True incd_lvl new_env rhs `thenLvl` \ rhs' ->
329 returnLvl (con, bs', rhs')
331 bs' = [ TB b incd_lvl | b <- bs ]
332 new_env = extendLvlEnv alts_env bs'
335 @lvlMFE@ is just like @lvlExpr@, except that it might let-bind
336 the expression, so that it can itself be floated.
339 lvlMFE :: Bool -- True <=> strict context [body of case or let]
340 -> Level -- Level of innermost enclosing lambda/tylam
341 -> LevelEnv -- Level of in-scope names/tyvars
342 -> CoreExprWithFVs -- input expression
343 -> LvlM LevelledExpr -- Result expression
345 lvlMFE strict_ctxt ctxt_lvl env (_, AnnType ty)
346 = returnLvl (Type ty)
348 lvlMFE strict_ctxt ctxt_lvl env ann_expr@(fvs, _)
349 | isUnLiftedType ty -- Can't let-bind it
350 || isInlineCtxt ctxt_lvl -- Don't float out of an __inline__ context
351 || exprIsTrivial expr -- Never float if it's trivial
352 || not good_destination
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 (TB 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 -- A decision to float entails let-binding this thing, and we only do
368 -- that if we'll escape a value lambda, or will go to the top level.
370 | dest_lvl `ltMajLvl` ctxt_lvl -- Escapes a value lambda
371 = not (exprIsCheap expr) || isTopLvl dest_lvl
372 -- Even if it escapes a value lambda, we only
373 -- float if it's not cheap (unless it'll get all the
374 -- way to the top). I've seen cases where we
375 -- float dozens of tiny free expressions, which cost
376 -- more to allocate than to evaluate.
377 -- NB: exprIsCheap is also true of bottom expressions, which
378 -- is good; we don't want to share them
380 -- It's only Really Bad to float a cheap expression out of a
381 -- strict context, because that builds a thunk that otherwise
382 -- would never be built. So another alternative would be to
384 -- || (strict_ctxt && not (exprIsBottom expr))
385 -- to the condition above. We should really try this out.
387 | otherwise -- Does not escape a value lambda
388 = isTopLvl dest_lvl -- Only float if we are going to the top level
389 && floatConsts env -- and the floatConsts flag is on
390 && not strict_ctxt -- Don't float from a strict context
391 -- We are keen to float something to the top level, even if it does not
392 -- escape a lambda, because then it needs no allocation. But it's controlled
393 -- by a flag, because doing this too early loses opportunities for RULES
394 -- which (needless to say) are important in some nofib programs
395 -- (gcd is an example).
398 -- concat = /\ a -> foldr ..a.. (++) []
399 -- was getting turned into
400 -- concat = /\ a -> lvl a
401 -- lvl = /\ a -> foldr ..a.. (++) []
402 -- which is pretty stupid. Hence the strict_ctxt test
406 %************************************************************************
408 \subsection{Bindings}
410 %************************************************************************
412 The binding stuff works for top level too.
415 lvlBind :: TopLevelFlag -- Used solely to decide whether to clone
416 -> Level -- Context level; might be Top even for bindings nested in the RHS
417 -- of a top level binding
420 -> LvlM (LevelledBind, LevelEnv)
422 lvlBind top_lvl ctxt_lvl env (AnnNonRec bndr rhs@(rhs_fvs,_))
423 | isInlineCtxt ctxt_lvl -- Don't do anything inside InlineMe
424 = lvlExpr ctxt_lvl env rhs `thenLvl` \ rhs' ->
425 returnLvl (NonRec (TB bndr ctxt_lvl) rhs', env)
428 = -- No type abstraction; clone existing binder
429 lvlExpr dest_lvl env rhs `thenLvl` \ rhs' ->
430 cloneVar top_lvl env bndr ctxt_lvl dest_lvl `thenLvl` \ (env', bndr') ->
431 returnLvl (NonRec (TB bndr' dest_lvl) rhs', env')
434 = -- Yes, type abstraction; create a new binder, extend substitution, etc
435 lvlFloatRhs abs_vars dest_lvl env rhs `thenLvl` \ rhs' ->
436 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (env', [bndr']) ->
437 returnLvl (NonRec (TB bndr' dest_lvl) rhs', env')
440 bind_fvs = rhs_fvs `unionVarSet` idFreeVars bndr
441 abs_vars = abstractVars dest_lvl env bind_fvs
443 dest_lvl | isUnLiftedType (idType bndr) = destLevel env bind_fvs False `maxLvl` Level 1 0
444 | otherwise = destLevel env bind_fvs (isFunction rhs)
445 -- Hack alert! We do have some unlifted bindings, for cheap primops, and
446 -- it is ok to float them out; but not to the top level. If they would otherwise
447 -- go to the top level, we pin them inside the topmost lambda
452 lvlBind top_lvl ctxt_lvl env (AnnRec pairs)
453 | isInlineCtxt ctxt_lvl -- Don't do anything inside InlineMe
454 = mapLvl (lvlExpr ctxt_lvl env) rhss `thenLvl` \ rhss' ->
455 returnLvl (Rec ([TB b ctxt_lvl | b <- bndrs] `zip` rhss'), env)
458 = cloneRecVars top_lvl env bndrs ctxt_lvl dest_lvl `thenLvl` \ (new_env, new_bndrs) ->
459 mapLvl (lvlExpr ctxt_lvl new_env) rhss `thenLvl` \ new_rhss ->
460 returnLvl (Rec ([TB b dest_lvl | b <- new_bndrs] `zip` new_rhss), new_env)
462 | isSingleton pairs && count isId abs_vars > 1
463 = -- Special case for self recursion where there are
464 -- several variables carried around: build a local loop:
465 -- poly_f = \abs_vars. \lam_vars . letrec f = \lam_vars. rhs in f lam_vars
466 -- This just makes the closures a bit smaller. If we don't do
467 -- this, allocation rises significantly on some programs
469 -- We could elaborate it for the case where there are several
470 -- mutually functions, but it's quite a bit more complicated
472 -- This all seems a bit ad hoc -- sigh
474 (bndr,rhs) = head pairs
475 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
476 rhs_env = extendLvlEnv env abs_vars_w_lvls
478 cloneVar NotTopLevel rhs_env bndr rhs_lvl rhs_lvl `thenLvl` \ (rhs_env', new_bndr) ->
480 (lam_bndrs, rhs_body) = collectAnnBndrs rhs
481 (body_lvl, new_lam_bndrs) = lvlLamBndrs rhs_lvl lam_bndrs
482 body_env = extendLvlEnv rhs_env' new_lam_bndrs
484 lvlExpr body_lvl body_env rhs_body `thenLvl` \ new_rhs_body ->
485 newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (poly_env, [poly_bndr]) ->
486 returnLvl (Rec [(TB poly_bndr dest_lvl,
487 mkLams abs_vars_w_lvls $
488 mkLams new_lam_bndrs $
489 Let (Rec [(TB new_bndr rhs_lvl, mkLams new_lam_bndrs new_rhs_body)])
490 (mkVarApps (Var new_bndr) lam_bndrs))],
493 | otherwise -- Non-null abs_vars
494 = newPolyBndrs dest_lvl env abs_vars bndrs `thenLvl` \ (new_env, new_bndrs) ->
495 mapLvl (lvlFloatRhs abs_vars dest_lvl new_env) rhss `thenLvl` \ new_rhss ->
496 returnLvl (Rec ([TB b dest_lvl | b <- new_bndrs] `zip` new_rhss), new_env)
499 (bndrs,rhss) = unzip pairs
501 -- Finding the free vars of the binding group is annoying
502 bind_fvs = (unionVarSets [ idFreeVars bndr `unionVarSet` rhs_fvs
503 | (bndr, (rhs_fvs,_)) <- pairs])
507 dest_lvl = destLevel env bind_fvs (all isFunction rhss)
508 abs_vars = abstractVars dest_lvl env bind_fvs
510 ----------------------------------------------------
511 -- Three help functons for the type-abstraction case
513 lvlFloatRhs abs_vars dest_lvl env rhs
514 = lvlExpr rhs_lvl rhs_env rhs `thenLvl` \ rhs' ->
515 returnLvl (mkLams abs_vars_w_lvls rhs')
517 (rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
518 rhs_env = extendLvlEnv env abs_vars_w_lvls
522 %************************************************************************
524 \subsection{Deciding floatability}
526 %************************************************************************
529 lvlLamBndrs :: Level -> [CoreBndr] -> (Level, [TaggedBndr Level])
530 -- Compute the levels for the binders of a lambda group
531 -- The binders returned are exactly the same as the ones passed,
532 -- but they are now paired with a level
536 lvlLamBndrs lvl bndrs
537 = go (incMinorLvl lvl)
538 False -- Havn't bumped major level in this group
541 go old_lvl bumped_major rev_lvld_bndrs (bndr:bndrs)
542 | isId bndr && -- Go to the next major level if this is a value binder,
543 not bumped_major && -- and we havn't already gone to the next level (one jump per group)
544 not (isOneShotLambda bndr) -- and it isn't a one-shot lambda
545 = go new_lvl True (TB bndr new_lvl : rev_lvld_bndrs) bndrs
548 = go old_lvl bumped_major (TB bndr old_lvl : rev_lvld_bndrs) bndrs
551 new_lvl = incMajorLvl old_lvl
553 go old_lvl _ rev_lvld_bndrs []
554 = (old_lvl, reverse rev_lvld_bndrs)
555 -- a lambda like this (\x -> coerce t (\s -> ...))
556 -- This happens quite a bit in state-transformer programs
560 -- Destintion level is the max Id level of the expression
561 -- (We'll abstract the type variables, if any.)
562 destLevel :: LevelEnv -> VarSet -> Bool -> Level
563 destLevel env fvs is_function
565 && is_function = tOP_LEVEL -- Send functions to top level; see
566 -- the comments with isFunction
567 | otherwise = maxIdLevel env fvs
569 isFunction :: CoreExprWithFVs -> Bool
570 -- The idea here is that we want to float *functions* to
571 -- the top level. This saves no work, but
572 -- (a) it can make the host function body a lot smaller,
573 -- and hence inlinable.
574 -- (b) it can also save allocation when the function is recursive:
575 -- h = \x -> letrec f = \y -> ...f...y...x...
578 -- f = \x y -> ...(f x)...y...x...
580 -- No allocation for f now.
581 -- We may only want to do this if there are sufficiently few free
582 -- variables. We certainly only want to do it for values, and not for
583 -- constructors. So the simple thing is just to look for lambdas
584 isFunction (_, AnnLam b e) | isId b = True
585 | otherwise = isFunction e
586 isFunction (_, AnnNote n e) = isFunction e
587 isFunction other = False
591 %************************************************************************
593 \subsection{Free-To-Level Monad}
595 %************************************************************************
598 type LevelEnv = (FloatOutSwitches,
599 VarEnv Level, -- Domain is *post-cloned* TyVars and Ids
600 Subst, -- Domain is pre-cloned Ids; tracks the in-scope set
601 -- so that subtitution is capture-avoiding
602 IdEnv ([Var], LevelledExpr)) -- Domain is pre-cloned Ids
603 -- We clone let-bound variables so that they are still
604 -- distinct when floated out; hence the SubstEnv/IdEnv.
605 -- (see point 3 of the module overview comment).
606 -- We also use these envs when making a variable polymorphic
607 -- because we want to float it out past a big lambda.
609 -- The SubstEnv and IdEnv always implement the same mapping, but the
610 -- SubstEnv maps to CoreExpr and the IdEnv to LevelledExpr
611 -- Since the range is always a variable or type application,
612 -- there is never any difference between the two, but sadly
613 -- the types differ. The SubstEnv is used when substituting in
614 -- a variable's IdInfo; the IdEnv when we find a Var.
616 -- In addition the IdEnv records a list of tyvars free in the
617 -- type application, just so we don't have to call freeVars on
618 -- the type application repeatedly.
620 -- The domain of the both envs is *pre-cloned* Ids, though
622 -- The domain of the VarEnv Level is the *post-cloned* Ids
624 initialEnv :: FloatOutSwitches -> LevelEnv
625 initialEnv float_lams = (float_lams, emptyVarEnv, emptySubst, emptyVarEnv)
627 floatLams :: LevelEnv -> Bool
628 floatLams (FloatOutSw float_lams _, _, _, _) = float_lams
630 floatConsts :: LevelEnv -> Bool
631 floatConsts (FloatOutSw _ float_consts, _, _, _) = float_consts
633 extendLvlEnv :: LevelEnv -> [TaggedBndr Level] -> LevelEnv
634 -- Used when *not* cloning
635 extendLvlEnv (float_lams, lvl_env, subst, id_env) prs
637 foldl add_lvl lvl_env prs,
638 foldl del_subst subst prs,
639 foldl del_id id_env prs)
641 add_lvl env (TB v l) = extendVarEnv env v l
642 del_subst env (TB v _) = extendInScope env v
643 del_id env (TB v _) = delVarEnv env v
644 -- We must remove any clone for this variable name in case of
645 -- shadowing. This bit me in the following case
646 -- (in nofib/real/gg/Spark.hs):
649 -- ... -> case e of wild {
650 -- ... -> ... wild ...
654 -- The inside occurrence of @wild@ was being replaced with @ds@,
655 -- incorrectly, because the SubstEnv was still lying around. Ouch!
658 -- extendCaseBndrLvlEnv adds the mapping case-bndr->scrut-var if it can
659 -- (see point 4 of the module overview comment)
660 extendCaseBndrLvlEnv (float_lams, lvl_env, subst, id_env) (Var scrut_var) case_bndr lvl
662 extendVarEnv lvl_env case_bndr lvl,
663 extendSubst subst case_bndr (DoneEx (Var scrut_var)),
664 extendVarEnv id_env case_bndr ([scrut_var], Var scrut_var))
666 extendCaseBndrLvlEnv env scrut case_bndr lvl
667 = extendLvlEnv env [TB case_bndr lvl]
669 extendPolyLvlEnv dest_lvl (float_lams, lvl_env, subst, id_env) abs_vars bndr_pairs
671 foldl add_lvl lvl_env bndr_pairs,
672 foldl add_subst subst bndr_pairs,
673 foldl add_id id_env bndr_pairs)
675 add_lvl env (v,v') = extendVarEnv env v' dest_lvl
676 add_subst env (v,v') = extendSubst env v (DoneEx (mkVarApps (Var v') abs_vars))
677 add_id env (v,v') = extendVarEnv env v ((v':abs_vars), mkVarApps (Var v') abs_vars)
679 extendCloneLvlEnv lvl (float_lams, lvl_env, _, id_env) new_subst bndr_pairs
681 foldl add_lvl lvl_env bndr_pairs,
683 foldl add_id id_env bndr_pairs)
685 add_lvl env (v,v') = extendVarEnv env v' lvl
686 add_id env (v,v') = extendVarEnv env v ([v'], Var v')
689 maxIdLevel :: LevelEnv -> VarSet -> Level
690 maxIdLevel (_, lvl_env,_,id_env) var_set
691 = foldVarSet max_in tOP_LEVEL var_set
693 max_in in_var lvl = foldr max_out lvl (case lookupVarEnv id_env in_var of
694 Just (abs_vars, _) -> abs_vars
698 | isId out_var = case lookupVarEnv lvl_env out_var of
699 Just lvl' -> maxLvl lvl' lvl
701 | otherwise = lvl -- Ignore tyvars in *maxIdLevel*
703 lookupVar :: LevelEnv -> Id -> LevelledExpr
704 lookupVar (_, _, _, id_env) v = case lookupVarEnv id_env v of
705 Just (_, expr) -> expr
708 abstractVars :: Level -> LevelEnv -> VarSet -> [Var]
709 -- Find the variables in fvs, free vars of the target expresion,
710 -- whose level is greater than the destination level
711 -- These are the ones we are going to abstract out
712 abstractVars dest_lvl env fvs
713 = uniq (sortLt lt [var | fv <- varSetElems fvs, var <- absVarsOf dest_lvl env fv])
715 -- Sort the variables so we don't get
716 -- mixed-up tyvars and Ids; it's just messy
717 v1 `lt` v2 = case (isId v1, isId v2) of
718 (True, False) -> False
719 (False, True) -> True
720 other -> v1 < v2 -- Same family
722 uniq :: [Var] -> [Var]
723 -- Remove adjacent duplicates; the sort will have brought them together
724 uniq (v1:v2:vs) | v1 == v2 = uniq (v2:vs)
725 | otherwise = v1 : uniq (v2:vs)
728 absVarsOf :: Level -> LevelEnv -> Var -> [Var]
729 -- If f is free in the expression, and f maps to poly_f a b c in the
730 -- current substitution, then we must report a b c as candidate type
732 absVarsOf dest_lvl (_, lvl_env, _, id_env) v
734 = [zap av2 | av1 <- lookup_avs v, av2 <- add_tyvars av1, abstract_me av2]
737 = if abstract_me v then [v] else []
740 abstract_me v = case lookupVarEnv lvl_env v of
741 Just lvl -> dest_lvl `ltLvl` lvl
744 lookup_avs v = case lookupVarEnv id_env v of
745 Just (abs_vars, _) -> abs_vars
748 add_tyvars v | isId v = v : varSetElems (idFreeTyVars v)
751 -- We are going to lambda-abstract, so nuke any IdInfo,
752 -- and add the tyvars of the Id (if necessary)
753 zap v | isId v = WARN( workerExists (idWorkerInfo v) ||
754 not (isEmptyCoreRules (idSpecialisation v)),
755 text "absVarsOf: discarding info on" <+> ppr v )
756 setIdInfo v vanillaIdInfo
761 type LvlM result = UniqSM result
770 newPolyBndrs dest_lvl env abs_vars bndrs
771 = getUniquesUs `thenLvl` \ uniqs ->
773 new_bndrs = zipWith mk_poly_bndr bndrs uniqs
775 returnLvl (extendPolyLvlEnv dest_lvl env abs_vars (bndrs `zip` new_bndrs), new_bndrs)
777 mk_poly_bndr bndr uniq = mkSysLocalUnencoded (mkFastString str) uniq poly_ty
779 str = "poly_" ++ occNameUserString (getOccName bndr)
780 poly_ty = mkPiTypes abs_vars (idType bndr)
784 -> [CoreBndr] -> Type -- Abstract wrt these bndrs
786 newLvlVar str vars body_ty
787 = getUniqueUs `thenLvl` \ uniq ->
788 returnUs (mkSysLocalUnencoded (mkFastString str) uniq (mkPiTypes vars body_ty))
790 -- The deeply tiresome thing is that we have to apply the substitution
791 -- to the rules inside each Id. Grr. But it matters.
793 cloneVar :: TopLevelFlag -> LevelEnv -> Id -> Level -> Level -> LvlM (LevelEnv, Id)
794 cloneVar TopLevel env v ctxt_lvl dest_lvl
795 = returnUs (env, v) -- Don't clone top level things
796 cloneVar NotTopLevel env@(_,_,subst,_) v ctxt_lvl dest_lvl
798 getUs `thenLvl` \ us ->
800 (subst', v1) = substAndCloneId subst us v
801 v2 = zap_demand ctxt_lvl dest_lvl v1
802 env' = extendCloneLvlEnv dest_lvl env subst' [(v,v2)]
806 cloneRecVars :: TopLevelFlag -> LevelEnv -> [Id] -> Level -> Level -> LvlM (LevelEnv, [Id])
807 cloneRecVars TopLevel env vs ctxt_lvl dest_lvl
808 = returnUs (env, vs) -- Don't clone top level things
809 cloneRecVars NotTopLevel env@(_,_,subst,_) vs ctxt_lvl dest_lvl
810 = ASSERT( all isId vs )
811 getUs `thenLvl` \ us ->
813 (subst', vs1) = substAndCloneRecIds subst us vs
814 vs2 = map (zap_demand ctxt_lvl dest_lvl) vs1
815 env' = extendCloneLvlEnv dest_lvl env subst' (vs `zip` vs2)
819 -- VERY IMPORTANT: we must zap the demand info
820 -- if the thing is going to float out past a lambda
821 zap_demand dest_lvl ctxt_lvl id
822 | ctxt_lvl == dest_lvl = id -- Stays put
823 | otherwise = zapDemandIdInfo id -- Floats out