2 % (c) The University of Glasgow, 1994-2000
4 \section{Core pass to saturate constructors and PrimOps}
8 corePrepPgm, corePrepExpr
11 #include "HsVersions.h"
13 import CoreUtils( exprType, exprIsValue, etaExpand, exprArity, exprOkForSpeculation )
14 import CoreFVs ( exprFreeVars )
15 import CoreLint ( endPass )
17 import Type ( Type, applyTy, splitFunTy_maybe,
18 isUnLiftedType, isUnboxedTupleType, seqType )
19 import TcType ( TyThing( AnId ) )
20 import NewDemand ( Demand, isStrictDmd, lazyDmd, StrictSig(..), DmdType(..) )
21 import Var ( Var, Id, setVarUnique )
24 import Id ( mkSysLocal, idType, idNewDemandInfo, idArity,
25 isFCallId, isGlobalId, isImplicitId,
26 isLocalId, hasNoBinding, idNewStrictness,
27 idUnfolding, isDataConWorkId_maybe
29 import HscTypes ( ModGuts(..), ModGuts, typeEnvElts )
30 import BasicTypes ( TopLevelFlag(..), isTopLevel, isNotTopLevel,
38 import Util ( listLengthCmp )
42 -- ---------------------------------------------------------------------------
44 -- ---------------------------------------------------------------------------
46 The goal of this pass is to prepare for code generation.
48 1. Saturate constructor and primop applications.
50 2. Convert to A-normal form:
52 * Use case for strict arguments:
53 f E ==> case E of x -> f x
56 * Use let for non-trivial lazy arguments
57 f E ==> let x = E in f x
58 (were f is lazy and x is non-trivial)
60 3. Similarly, convert any unboxed lets into cases.
61 [I'm experimenting with leaving 'ok-for-speculation'
62 rhss in let-form right up to this point.]
64 4. Ensure that lambdas only occur as the RHS of a binding
65 (The code generator can't deal with anything else.)
67 5. [Not any more; nuked Jun 2002] Do the seq/par munging.
69 6. Clone all local Ids.
70 This means that all such Ids are unique, rather than the
71 weaker guarantee of no clashes which the simplifier provides.
72 And that is what the code generator needs.
74 We don't clone TyVars. The code gen doesn't need that,
75 and doing so would be tiresome because then we'd need
76 to substitute in types.
79 7. Give each dynamic CCall occurrence a fresh unique; this is
80 rather like the cloning step above.
82 8. Inject bindings for the "implicit" Ids:
83 * Constructor wrappers
86 We want curried definitions for all of these in case they
87 aren't inlined by some caller.
89 This is all done modulo type applications and abstractions, so that
90 when type erasure is done for conversion to STG, we don't end up with
91 any trivial or useless bindings.
95 -- -----------------------------------------------------------------------------
97 -- -----------------------------------------------------------------------------
100 corePrepPgm :: DynFlags -> ModGuts -> IO ModGuts
101 corePrepPgm dflags mod_impl
102 = do showPass dflags "CorePrep"
103 us <- mkSplitUniqSupply 's'
105 let implicit_binds = mkImplicitBinds (mg_types mod_impl)
106 -- NB: we must feed mkImplicitBinds through corePrep too
107 -- so that they are suitably cloned and eta-expanded
109 binds_out = initUs_ us (
110 corePrepTopBinds (mg_binds mod_impl) `thenUs` \ floats1 ->
111 corePrepTopBinds implicit_binds `thenUs` \ floats2 ->
112 returnUs (deFloatTop (floats1 `appOL` floats2))
115 endPass dflags "CorePrep" Opt_D_dump_prep binds_out
116 return (mod_impl { mg_binds = binds_out })
118 corePrepExpr :: DynFlags -> CoreExpr -> IO CoreExpr
119 corePrepExpr dflags expr
120 = do showPass dflags "CorePrep"
121 us <- mkSplitUniqSupply 's'
122 let new_expr = initUs_ us (corePrepAnExpr emptyVarEnv expr)
123 dumpIfSet_dyn dflags Opt_D_dump_prep "CorePrep"
128 -- -----------------------------------------------------------------------------
130 -- -----------------------------------------------------------------------------
132 Create any necessary "implicit" bindings (data constructors etc).
134 * Constructor workers
135 * Constructor wrappers
136 * Data type record selectors
139 In the latter three cases, the Id contains the unfolding to use for
140 the binding. In the case of data con workers we create the rather
141 strange (non-recursive!) binding
143 $wC = \x y -> $wC x y
145 i.e. a curried constructor that allocates. This means that we can
146 treat the worker for a constructor like any other function in the rest
147 of the compiler. The point here is that CoreToStg will generate a
148 StgConApp for the RHS, rather than a call to the worker (which would
149 give a loop). As Lennart says: the ice is thin here, but it works.
151 Hmm. Should we create bindings for dictionary constructors? They are
152 always fully applied, and the bindings are just there to support
153 partial applications. But it's easier to let them through.
156 mkImplicitBinds type_env
157 = [ NonRec id (get_unfolding id)
158 | AnId id <- typeEnvElts type_env, isImplicitId id ]
159 -- The type environment already contains all the implicit Ids,
160 -- so we just filter them out
162 -- The etaExpand is so that the manifest arity of the
163 -- binding matches its claimed arity, which is an
164 -- invariant of top level bindings going into the code gen
166 get_unfolding id -- See notes above
167 | Just data_con <- isDataConWorkId_maybe id = Var id -- The ice is thin here, but it works
168 -- CorePrep will eta-expand it
169 | otherwise = unfoldingTemplate (idUnfolding id)
174 -- ---------------------------------------------------------------------------
175 -- Dealing with bindings
176 -- ---------------------------------------------------------------------------
178 data FloatingBind = FloatLet CoreBind
179 | FloatCase Id CoreExpr Bool
180 -- The bool indicates "ok-for-speculation"
182 instance Outputable FloatingBind where
183 ppr (FloatLet bind) = text "FloatLet" <+> ppr bind
184 ppr (FloatCase b rhs spec) = text "FloatCase" <+> ppr b <+> ppr spec <+> equals <+> ppr rhs
186 type CloneEnv = IdEnv Id -- Clone local Ids
188 deFloatTop :: OrdList FloatingBind -> [CoreBind]
189 -- For top level only; we don't expect any FloatCases
191 = foldrOL get [] floats
193 get (FloatLet b) bs = b:bs
194 get b bs = pprPanic "corePrepPgm" (ppr b)
196 allLazy :: TopLevelFlag -> RecFlag -> OrdList FloatingBind -> Bool
197 allLazy top_lvl is_rec floats
198 = foldrOL check True floats
200 unboxed_ok = isNotTopLevel top_lvl && isNonRec is_rec
202 check (FloatLet _) y = y
203 check (FloatCase _ _ ok_for_spec) y = unboxed_ok && ok_for_spec && y
204 -- The ok-for-speculation flag says that it's safe to
205 -- float this Case out of a let, and thereby do it more eagerly
206 -- We need the top-level flag because it's never ok to float
207 -- an unboxed binding to the top level
209 -- ---------------------------------------------------------------------------
211 -- ---------------------------------------------------------------------------
213 corePrepTopBinds :: [CoreBind] -> UniqSM (OrdList FloatingBind)
214 corePrepTopBinds binds
215 = go emptyVarEnv binds
217 go env [] = returnUs nilOL
218 go env (bind : binds) = corePrepTopBind env bind `thenUs` \ (env', bind') ->
219 go env' binds `thenUs` \ binds' ->
220 returnUs (bind' `appOL` binds')
222 -- NB: we do need to float out of top-level bindings
223 -- Consider x = length [True,False]
229 -- We return a *list* of bindings, because we may start with
231 -- where x is demanded, in which case we want to finish with
234 -- And then x will actually end up case-bound
236 --------------------------------
237 corePrepTopBind :: CloneEnv -> CoreBind -> UniqSM (CloneEnv, OrdList FloatingBind)
238 corePrepTopBind env (NonRec bndr rhs)
239 = cloneBndr env bndr `thenUs` \ (env', bndr') ->
240 corePrepRhs TopLevel NonRecursive env (bndr, rhs) `thenUs` \ (floats, rhs') ->
241 returnUs (env', floats `snocOL` FloatLet (NonRec bndr' rhs'))
243 corePrepTopBind env (Rec pairs) = corePrepRecPairs TopLevel env pairs
245 --------------------------------
246 corePrepBind :: CloneEnv -> CoreBind -> UniqSM (CloneEnv, OrdList FloatingBind)
247 -- This one is used for *local* bindings
248 corePrepBind env (NonRec bndr rhs)
249 = etaExpandRhs bndr rhs `thenUs` \ rhs1 ->
250 corePrepExprFloat env rhs1 `thenUs` \ (floats, rhs2) ->
251 cloneBndr env bndr `thenUs` \ (env', bndr') ->
252 mkLocalNonRec bndr' (bdrDem bndr') floats rhs2 `thenUs` \ floats' ->
253 returnUs (env', floats')
255 corePrepBind env (Rec pairs) = corePrepRecPairs NotTopLevel env pairs
257 --------------------------------
258 corePrepRecPairs :: TopLevelFlag -> CloneEnv
259 -> [(Id,CoreExpr)] -- Recursive bindings
260 -> UniqSM (CloneEnv, OrdList FloatingBind)
261 -- Used for all recursive bindings, top level and otherwise
262 corePrepRecPairs lvl env pairs
263 = cloneBndrs env (map fst pairs) `thenUs` \ (env', bndrs') ->
264 mapAndUnzipUs (corePrepRhs lvl Recursive env') pairs `thenUs` \ (floats_s, rhss') ->
265 returnUs (env', unitOL (FloatLet (Rec (flatten (concatOL floats_s) bndrs' rhss'))))
267 -- Flatten all the floats, and the currrent
268 -- group into a single giant Rec
269 flatten floats bndrs rhss = foldrOL get (bndrs `zip` rhss) floats
271 get (FloatLet (NonRec b r)) prs2 = (b,r) : prs2
272 get (FloatLet (Rec prs1)) prs2 = prs1 ++ prs2
274 --------------------------------
275 corePrepRhs :: TopLevelFlag -> RecFlag
276 -> CloneEnv -> (Id, CoreExpr)
277 -> UniqSM (OrdList FloatingBind, CoreExpr)
278 -- Used for top-level bindings, and local recursive bindings
279 corePrepRhs top_lvl is_rec env (bndr, rhs)
280 = etaExpandRhs bndr rhs `thenUs` \ rhs' ->
281 corePrepExprFloat env rhs' `thenUs` \ floats_w_rhs ->
282 floatRhs top_lvl is_rec bndr floats_w_rhs
285 -- ---------------------------------------------------------------------------
286 -- Making arguments atomic (function args & constructor args)
287 -- ---------------------------------------------------------------------------
289 -- This is where we arrange that a non-trivial argument is let-bound
290 corePrepArg :: CloneEnv -> CoreArg -> RhsDemand
291 -> UniqSM (OrdList FloatingBind, CoreArg)
292 corePrepArg env arg dem
293 = corePrepExprFloat env arg `thenUs` \ (floats, arg') ->
294 if exprIsTrivial arg'
295 then returnUs (floats, arg')
296 else newVar (exprType arg') `thenUs` \ v ->
297 mkLocalNonRec v dem floats arg' `thenUs` \ floats' ->
298 returnUs (floats', Var v)
300 -- version that doesn't consider an scc annotation to be trivial.
301 exprIsTrivial (Var v) = True
302 exprIsTrivial (Type _) = True
303 exprIsTrivial (Lit lit) = True
304 exprIsTrivial (App e arg) = isTypeArg arg && exprIsTrivial e
305 exprIsTrivial (Note (SCC _) e) = False
306 exprIsTrivial (Note _ e) = exprIsTrivial e
307 exprIsTrivial (Lam b body) | isTyVar b = exprIsTrivial body
308 exprIsTrivial other = False
310 -- ---------------------------------------------------------------------------
311 -- Dealing with expressions
312 -- ---------------------------------------------------------------------------
314 corePrepAnExpr :: CloneEnv -> CoreExpr -> UniqSM CoreExpr
315 corePrepAnExpr env expr
316 = corePrepExprFloat env expr `thenUs` \ (floats, expr) ->
320 corePrepExprFloat :: CloneEnv -> CoreExpr -> UniqSM (OrdList FloatingBind, CoreExpr)
324 -- e = let bs in e' (semantically, that is!)
327 -- f (g x) ===> ([v = g x], f v)
329 corePrepExprFloat env (Var v)
330 = fiddleCCall v `thenUs` \ v1 ->
331 let v2 = lookupVarEnv env v1 `orElse` v1 in
332 maybeSaturate v2 (Var v2) 0 (idType v2) `thenUs` \ app ->
333 returnUs (nilOL, app)
335 corePrepExprFloat env expr@(Type _)
336 = returnUs (nilOL, expr)
338 corePrepExprFloat env expr@(Lit lit)
339 = returnUs (nilOL, expr)
341 corePrepExprFloat env (Let bind body)
342 = corePrepBind env bind `thenUs` \ (env', new_binds) ->
343 corePrepExprFloat env' body `thenUs` \ (floats, new_body) ->
344 returnUs (new_binds `appOL` floats, new_body)
346 corePrepExprFloat env (Note n@(SCC _) expr)
347 = corePrepAnExpr env expr `thenUs` \ expr1 ->
348 deLamFloat expr1 `thenUs` \ (floats, expr2) ->
349 returnUs (floats, Note n expr2)
351 corePrepExprFloat env (Note other_note expr)
352 = corePrepExprFloat env expr `thenUs` \ (floats, expr') ->
353 returnUs (floats, Note other_note expr')
355 corePrepExprFloat env expr@(Lam _ _)
356 = cloneBndrs env bndrs `thenUs` \ (env', bndrs') ->
357 corePrepAnExpr env' body `thenUs` \ body' ->
358 returnUs (nilOL, mkLams bndrs' body')
360 (bndrs,body) = collectBinders expr
362 corePrepExprFloat env (Case scrut bndr alts)
363 = corePrepExprFloat env scrut `thenUs` \ (floats1, scrut1) ->
364 deLamFloat scrut1 `thenUs` \ (floats2, scrut2) ->
365 cloneBndr env bndr `thenUs` \ (env', bndr') ->
366 mapUs (sat_alt env') alts `thenUs` \ alts' ->
367 returnUs (floats1 `appOL` floats2 , Case scrut2 bndr' alts')
369 sat_alt env (con, bs, rhs)
370 = cloneBndrs env bs `thenUs` \ (env', bs') ->
371 corePrepAnExpr env' rhs `thenUs` \ rhs1 ->
372 deLam rhs1 `thenUs` \ rhs2 ->
373 returnUs (con, bs', rhs2)
375 corePrepExprFloat env expr@(App _ _)
376 = collect_args expr 0 `thenUs` \ (app, (head,depth), ty, floats, ss) ->
377 ASSERT(null ss) -- make sure we used all the strictness info
379 -- Now deal with the function
381 Var fn_id -> maybeSaturate fn_id app depth ty `thenUs` \ app' ->
382 returnUs (floats, app')
384 _other -> returnUs (floats, app)
388 -- Deconstruct and rebuild the application, floating any non-atomic
389 -- arguments to the outside. We collect the type of the expression,
390 -- the head of the application, and the number of actual value arguments,
391 -- all of which are used to possibly saturate this application if it
392 -- has a constructor or primop at the head.
396 -> Int -- current app depth
397 -> UniqSM (CoreExpr, -- the rebuilt expression
398 (CoreExpr,Int), -- the head of the application,
399 -- and no. of args it was applied to
400 Type, -- type of the whole expr
401 OrdList FloatingBind, -- any floats we pulled out
402 [Demand]) -- remaining argument demands
404 collect_args (App fun arg@(Type arg_ty)) depth
405 = collect_args fun depth `thenUs` \ (fun',hd,fun_ty,floats,ss) ->
406 returnUs (App fun' arg, hd, applyTy fun_ty arg_ty, floats, ss)
408 collect_args (App fun arg) depth
409 = collect_args fun (depth+1) `thenUs` \ (fun',hd,fun_ty,floats,ss) ->
411 (ss1, ss_rest) = case ss of
412 (ss1:ss_rest) -> (ss1, ss_rest)
414 (arg_ty, res_ty) = expectJust "corePrepExprFloat:collect_args" $
415 splitFunTy_maybe fun_ty
417 corePrepArg env arg (mkDemTy ss1 arg_ty) `thenUs` \ (fs, arg') ->
418 returnUs (App fun' arg', hd, res_ty, fs `appOL` floats, ss_rest)
420 collect_args (Var v) depth
421 = fiddleCCall v `thenUs` \ v1 ->
422 let v2 = lookupVarEnv env v1 `orElse` v1 in
423 returnUs (Var v2, (Var v2, depth), idType v2, nilOL, stricts)
425 stricts = case idNewStrictness v of
426 StrictSig (DmdType _ demands _)
427 | listLengthCmp demands depth /= GT -> demands
428 -- length demands <= depth
430 -- If depth < length demands, then we have too few args to
431 -- satisfy strictness info so we have to ignore all the
432 -- strictness info, e.g. + (error "urk")
433 -- Here, we can't evaluate the arg strictly, because this
434 -- partial application might be seq'd
437 collect_args (Note (Coerce ty1 ty2) fun) depth
438 = collect_args fun depth `thenUs` \ (fun', hd, fun_ty, floats, ss) ->
439 returnUs (Note (Coerce ty1 ty2) fun', hd, ty1, floats, ss)
441 collect_args (Note note fun) depth
443 = collect_args fun depth `thenUs` \ (fun', hd, fun_ty, floats, ss) ->
444 returnUs (Note note fun', hd, fun_ty, floats, ss)
446 -- non-variable fun, better let-bind it
447 -- ToDo: perhaps we can case-bind rather than let-bind this closure,
448 -- since it is sure to be evaluated.
449 collect_args fun depth
450 = corePrepExprFloat env fun `thenUs` \ (fun_floats, fun') ->
451 newVar ty `thenUs` \ fn_id ->
452 mkLocalNonRec fn_id onceDem fun_floats fun' `thenUs` \ floats ->
453 returnUs (Var fn_id, (Var fn_id, depth), ty, floats, [])
457 ignore_note InlineCall = True
458 ignore_note InlineMe = True
459 ignore_note _other = False
460 -- we don't ignore SCCs, since they require some code generation
462 ------------------------------------------------------------------------------
463 -- Building the saturated syntax
464 -- ---------------------------------------------------------------------------
466 -- maybeSaturate deals with saturating primops and constructors
467 -- The type is the type of the entire application
468 maybeSaturate :: Id -> CoreExpr -> Int -> Type -> UniqSM CoreExpr
469 maybeSaturate fn expr n_args ty
470 | hasNoBinding fn = saturate_it
471 | otherwise = returnUs expr
473 fn_arity = idArity fn
474 excess_arity = fn_arity - n_args
475 saturate_it = getUniquesUs `thenUs` \ us ->
476 returnUs (etaExpand excess_arity us expr ty)
478 -- ---------------------------------------------------------------------------
479 -- Precipitating the floating bindings
480 -- ---------------------------------------------------------------------------
482 floatRhs :: TopLevelFlag -> RecFlag
484 -> (OrdList FloatingBind, CoreExpr) -- Rhs: let binds in body
485 -> UniqSM (OrdList FloatingBind, -- Floats out of this bind
486 CoreExpr) -- Final Rhs
488 floatRhs top_lvl is_rec bndr (floats, rhs)
489 | isTopLevel top_lvl || exprIsValue rhs, -- Float to expose value or
490 allLazy top_lvl is_rec floats -- at top level
491 = -- Why the test for allLazy?
492 -- v = f (x `divInt#` y)
493 -- we don't want to float the case, even if f has arity 2,
494 -- because floating the case would make it evaluated too early
496 -- Finally, eta-expand the RHS, for the benefit of the code gen
497 returnUs (floats, rhs)
500 -- Don't float; the RHS isn't a value
501 = mkBinds floats rhs `thenUs` \ rhs' ->
502 returnUs (nilOL, rhs')
504 -- mkLocalNonRec is used only for *nested*, *non-recursive* bindings
505 mkLocalNonRec :: Id -> RhsDemand -- Lhs: id with demand
506 -> OrdList FloatingBind -> CoreExpr -- Rhs: let binds in body
507 -> UniqSM (OrdList FloatingBind)
509 mkLocalNonRec bndr dem floats rhs
510 | isUnLiftedType (idType bndr)
511 -- If this is an unlifted binding, we always make a case for it.
512 = ASSERT( not (isUnboxedTupleType (idType bndr)) )
514 float = FloatCase bndr rhs (exprOkForSpeculation rhs)
516 returnUs (floats `snocOL` float)
519 -- It's a strict let so we definitely float all the bindings
520 = let -- Don't make a case for a value binding,
521 -- even if it's strict. Otherwise we get
522 -- case (\x -> e) of ...!
523 float | exprIsValue rhs = FloatLet (NonRec bndr rhs)
524 | otherwise = FloatCase bndr rhs (exprOkForSpeculation rhs)
526 returnUs (floats `snocOL` float)
529 = floatRhs NotTopLevel NonRecursive bndr (floats, rhs) `thenUs` \ (floats', rhs') ->
530 returnUs (floats' `snocOL` FloatLet (NonRec bndr rhs'))
533 bndr_ty = idType bndr
536 mkBinds :: OrdList FloatingBind -> CoreExpr -> UniqSM CoreExpr
538 | isNilOL binds = returnUs body
539 | otherwise = deLam body `thenUs` \ body' ->
540 returnUs (foldrOL mk_bind body' binds)
542 mk_bind (FloatCase bndr rhs _) body = Case rhs bndr [(DEFAULT, [], body)]
543 mk_bind (FloatLet bind) body = Let bind body
545 etaExpandRhs bndr rhs
546 = -- Eta expand to match the arity claimed by the binder
547 -- Remember, after CorePrep we must not change arity
549 -- Eta expansion might not have happened already,
550 -- because it is done by the simplifier only when
551 -- there at least one lambda already.
553 -- NB1:we could refrain when the RHS is trivial (which can happen
554 -- for exported things). This would reduce the amount of code
555 -- generated (a little) and make things a little words for
556 -- code compiled without -O. The case in point is data constructor
559 -- NB2: we have to be careful that the result of etaExpand doesn't
560 -- invalidate any of the assumptions that CorePrep is attempting
561 -- to establish. One possible cause is eta expanding inside of
562 -- an SCC note - we're now careful in etaExpand to make sure the
563 -- SCC is pushed inside any new lambdas that are generated.
565 -- NB3: It's important to do eta expansion, and *then* ANF-ising
566 -- f = /\a -> g (h 3) -- h has arity 2
567 -- If we ANF first we get
568 -- f = /\a -> let s = h 3 in g s
569 -- and now eta expansion gives
570 -- f = /\a -> \ y -> (let s = h 3 in g s) y
571 -- which is horrible.
572 -- Eta expanding first gives
573 -- f = /\a -> \y -> let s = h 3 in g s y
575 getUniquesUs `thenUs` \ us ->
576 returnUs (etaExpand arity us rhs (idType bndr))
578 -- For a GlobalId, take the Arity from the Id.
579 -- It was set in CoreTidy and must not change
580 -- For all others, just expand at will
581 arity | isGlobalId bndr = idArity bndr
582 | otherwise = exprArity rhs
584 -- ---------------------------------------------------------------------------
585 -- Eliminate Lam as a non-rhs (STG doesn't have such a thing)
586 -- We arrange that they only show up as the RHS of a let(rec)
587 -- ---------------------------------------------------------------------------
589 deLam :: CoreExpr -> UniqSM CoreExpr
591 deLamFloat expr `thenUs` \ (floats, expr) ->
595 deLamFloat :: CoreExpr -> UniqSM (OrdList FloatingBind, CoreExpr)
596 -- Remove top level lambdas by let-bindinig
598 deLamFloat (Note n expr)
599 = -- You can get things like
600 -- case e of { p -> coerce t (\s -> ...) }
601 deLamFloat expr `thenUs` \ (floats, expr') ->
602 returnUs (floats, Note n expr')
605 | null bndrs = returnUs (nilOL, expr)
607 = case tryEta bndrs body of
608 Just no_lam_result -> returnUs (nilOL, no_lam_result)
609 Nothing -> newVar (exprType expr) `thenUs` \ fn ->
610 returnUs (unitOL (FloatLet (NonRec fn expr)),
613 (bndrs,body) = collectBinders expr
615 -- Why try eta reduction? Hasn't the simplifier already done eta?
616 -- But the simplifier only eta reduces if that leaves something
617 -- trivial (like f, or f Int). But for deLam it would be enough to
618 -- get to a partial application, like (map f).
620 tryEta bndrs expr@(App _ _)
621 | ok_to_eta_reduce f &&
623 and (zipWith ok bndrs last_args) &&
624 not (any (`elemVarSet` fvs_remaining) bndrs)
625 = Just remaining_expr
627 (f, args) = collectArgs expr
628 remaining_expr = mkApps f remaining_args
629 fvs_remaining = exprFreeVars remaining_expr
630 (remaining_args, last_args) = splitAt n_remaining args
631 n_remaining = length args - length bndrs
633 ok bndr (Var arg) = bndr == arg
634 ok bndr other = False
636 -- we can't eta reduce something which must be saturated.
637 ok_to_eta_reduce (Var f) = not (hasNoBinding f)
638 ok_to_eta_reduce _ = False --safe. ToDo: generalise
640 tryEta bndrs (Let bind@(NonRec b r) body)
641 | not (any (`elemVarSet` fvs) bndrs)
642 = case tryEta bndrs body of
643 Just e -> Just (Let bind e)
648 tryEta bndrs _ = Nothing
652 -- -----------------------------------------------------------------------------
654 -- -----------------------------------------------------------------------------
658 = RhsDemand { isStrict :: Bool, -- True => used at least once
659 isOnceDem :: Bool -- True => used at most once
662 mkDem :: Demand -> Bool -> RhsDemand
663 mkDem strict once = RhsDemand (isStrictDmd strict) once
665 mkDemTy :: Demand -> Type -> RhsDemand
666 mkDemTy strict ty = RhsDemand (isStrictDmd strict)
669 bdrDem :: Id -> RhsDemand
670 bdrDem id = mkDem (idNewDemandInfo id)
673 -- safeDem :: RhsDemand
674 -- safeDem = RhsDemand False False -- always safe to use this
677 onceDem = RhsDemand False True -- used at most once
683 %************************************************************************
687 %************************************************************************
690 ------------------------------------------------------------------------------
692 -- ---------------------------------------------------------------------------
694 cloneBndrs :: CloneEnv -> [Var] -> UniqSM (CloneEnv, [Var])
695 cloneBndrs env bs = mapAccumLUs cloneBndr env bs
697 cloneBndr :: CloneEnv -> Var -> UniqSM (CloneEnv, Var)
700 = getUniqueUs `thenUs` \ uniq ->
702 bndr' = setVarUnique bndr uniq
704 returnUs (extendVarEnv env bndr bndr', bndr')
706 | otherwise -- Top level things, which we don't want
707 -- to clone, have become GlobalIds by now
708 -- And we don't clone tyvars
709 = returnUs (env, bndr)
712 ------------------------------------------------------------------------------
713 -- Cloning ccall Ids; each must have a unique name,
714 -- to give the code generator a handle to hang it on
715 -- ---------------------------------------------------------------------------
717 fiddleCCall :: Id -> UniqSM Id
719 | isFCallId id = getUniqueUs `thenUs` \ uniq ->
720 returnUs (id `setVarUnique` uniq)
721 | otherwise = returnUs id
723 ------------------------------------------------------------------------------
724 -- Generating new binders
725 -- ---------------------------------------------------------------------------
727 newVar :: Type -> UniqSM Id
730 getUniqueUs `thenUs` \ uniq ->
731 returnUs (mkSysLocal FSLIT("sat") uniq ty)