2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[SimplCore]{Driver for simplifying @Core@ programs}
7 module SimplCore ( core2core ) where
9 #include "HsVersions.h"
11 import CmdLineOpts ( CoreToDo(..), SimplifierSwitch(..),
12 SwitchResult(..), switchIsOn, intSwitchSet,
13 opt_D_dump_occur_anal, opt_D_dump_rules,
14 opt_D_dump_simpl_iterations,
15 opt_D_dump_simpl_stats,
16 opt_D_dump_simpl, opt_D_dump_rules,
17 opt_D_verbose_core2core,
18 opt_D_dump_occur_anal,
21 import CoreLint ( beginPass, endPass )
23 import CSE ( cseProgram )
24 import Rules ( RuleBase, ProtoCoreRule(..), pprProtoCoreRule, prepareRuleBase, orphanRule )
26 import PprCore ( pprCoreBindings )
27 import OccurAnal ( occurAnalyseBinds )
28 import CoreUtils ( exprIsTrivial, coreExprType )
29 import Simplify ( simplTopBinds, simplExpr )
30 import SimplUtils ( etaCoreExpr, findDefault, simplBinders )
32 import Const ( Con(..), Literal(..), literalType, mkMachInt )
33 import ErrUtils ( dumpIfSet )
34 import FloatIn ( floatInwards )
35 import FloatOut ( floatOutwards )
36 import Id ( Id, mkSysLocal, mkVanillaId, isBottomingId,
37 idType, setIdType, idName, idInfo, setIdNoDiscard
41 import Module ( Module )
42 import Name ( mkLocalName, tidyOccName, tidyTopName,
43 NamedThing(..), OccName
45 import TyCon ( TyCon, isDataTyCon )
46 import PrimOp ( PrimOp(..) )
47 import PrelInfo ( unpackCStringId, unpackCString2Id, addr2IntegerId )
48 import Type ( Type, splitAlgTyConApp_maybe,
50 tidyType, tidyTypes, tidyTopType, tidyTyVar, tidyTyVars,
53 import TysWiredIn ( smallIntegerDataCon, isIntegerTy )
54 import LiberateCase ( liberateCase )
55 import SAT ( doStaticArgs )
56 import Specialise ( specProgram)
57 import UsageSPInf ( doUsageSPInf )
58 import StrictAnal ( saBinds )
59 import WorkWrap ( wwTopBinds )
60 import CprAnalyse ( cprAnalyse )
62 import Unique ( Unique, Uniquable(..),
65 import UniqSupply ( UniqSupply, mkSplitUniqSupply, splitUniqSupply, uniqFromSupply )
66 import Constants ( tARGET_MIN_INT, tARGET_MAX_INT )
67 import Util ( mapAccumL )
68 import SrcLoc ( noSrcLoc )
71 import IO ( hPutStr, stderr )
74 import Ratio ( numerator, denominator )
77 %************************************************************************
79 \subsection{The driver for the simplifier}
81 %************************************************************************
84 core2core :: [CoreToDo] -- Spec of what core-to-core passes to do
85 -> [CoreBind] -- Binds in
86 -> [ProtoCoreRule] -- Rules
87 -> IO ([CoreBind], [ProtoCoreRule])
89 core2core core_todos binds rules
91 us <- mkSplitUniqSupply 's'
92 let (cp_us, us1) = splitUniqSupply us
93 (ru_us, ps_us) = splitUniqSupply us1
95 better_rules <- simplRules ru_us rules binds
97 let (binds1, rule_base) = prepareRuleBase binds better_rules
99 -- Do the main business
100 (stats, processed_binds) <- doCorePasses zeroSimplCount cp_us binds1
103 dumpIfSet opt_D_dump_simpl_stats
104 "Grand total simplifier statistics"
105 (pprSimplCount stats)
107 -- Do the post-simplification business
108 post_simpl_binds <- doPostSimplification ps_us processed_binds
111 return (post_simpl_binds, filter orphanRule better_rules)
114 doCorePasses stats us binds irs []
115 = return (stats, binds)
117 doCorePasses stats us binds irs (to_do : to_dos)
119 let (us1, us2) = splitUniqSupply us
120 (stats1, binds1) <- doCorePass us1 binds irs to_do
121 doCorePasses (stats `plusSimplCount` stats1) us2 binds1 irs to_dos
123 doCorePass us binds rb (CoreDoSimplify sw_chkr) = _scc_ "Simplify" simplifyPgm rb sw_chkr us binds
124 doCorePass us binds rb CoreCSE = _scc_ "CommonSubExpr" noStats (cseProgram binds)
125 doCorePass us binds rb CoreLiberateCase = _scc_ "LiberateCase" noStats (liberateCase binds)
126 doCorePass us binds rb CoreDoFloatInwards = _scc_ "FloatInwards" noStats (floatInwards binds)
127 doCorePass us binds rb CoreDoFullLaziness = _scc_ "FloatOutwards" noStats (floatOutwards us binds)
128 doCorePass us binds rb CoreDoStaticArgs = _scc_ "StaticArgs" noStats (doStaticArgs us binds)
129 doCorePass us binds rb CoreDoStrictness = _scc_ "Stranal" noStats (saBinds binds)
130 doCorePass us binds rb CoreDoWorkerWrapper = _scc_ "WorkWrap" noStats (wwTopBinds us binds)
131 doCorePass us binds rb CoreDoSpecialising = _scc_ "Specialise" noStats (specProgram us binds)
132 doCorePass us binds rb CoreDoCPResult = _scc_ "CPResult" noStats (cprAnalyse binds)
133 doCorePass us binds rb CoreDoPrintCore = _scc_ "PrintCore" noStats (printCore binds)
134 doCorePass us binds rb CoreDoUSPInf
135 = _scc_ "CoreUsageSPInf"
136 if opt_UsageSPOn then
137 noStats (doUsageSPInf us binds)
139 trace "WARNING: ignoring requested -fusagesp pass; requires -fusagesp-on" $
140 noStats (return binds)
142 printCore binds = do dumpIfSet True "Print Core"
143 (pprCoreBindings binds)
146 noStats thing = do { result <- thing; return (zeroSimplCount, result) }
150 %************************************************************************
152 \subsection{Dealing with rules}
154 %************************************************************************
156 We must do some gentle simplifiation on the template (but not the RHS)
157 of each rule. The case that forced me to add this was the fold/build rule,
158 which without simplification looked like:
159 fold k z (build (/\a. g a)) ==> ...
160 This doesn't match unless you do eta reduction on the build argument.
163 simplRules :: UniqSupply -> [ProtoCoreRule] -> [CoreBind] -> IO [ProtoCoreRule]
164 simplRules us rules binds
165 = do let (better_rules,_) = initSmpl sw_chkr us bind_vars black_list_all (mapSmpl simplRule rules)
167 dumpIfSet opt_D_dump_rules
168 "Transformation rules"
169 (vcat (map pprProtoCoreRule better_rules))
173 black_list_all v = True -- This stops all inlining
174 sw_chkr any = SwBool False -- A bit bogus
176 -- Boringly, we need to gather the in-scope set.
177 -- Typically this thunk won't even be force, but the test in
178 -- simpVar fails if it isn't right, and it might conceivably matter
179 bind_vars = foldr (unionVarSet . mkVarSet . bindersOf) emptyVarSet binds
182 simplRule rule@(ProtoCoreRule is_local id (Rule name bndrs args rhs))
184 = returnSmpl rule -- No need to fiddle with imported rules
186 = simplBinders bndrs $ \ bndrs' ->
187 mapSmpl simplExpr args `thenSmpl` \ args' ->
188 simplExpr rhs `thenSmpl` \ rhs' ->
189 returnSmpl (ProtoCoreRule is_local id (Rule name bndrs' args' rhs'))
192 %************************************************************************
194 \subsection{The driver for the simplifier}
196 %************************************************************************
199 simplifyPgm :: RuleBase
200 -> (SimplifierSwitch -> SwitchResult)
202 -> [CoreBind] -- Input
203 -> IO (SimplCount, [CoreBind]) -- New bindings
205 simplifyPgm (imported_rule_ids, rule_lhs_fvs)
208 beginPass "Simplify";
210 -- Glom all binds together in one Rec, in case any
211 -- transformations have introduced any new dependencies
213 -- NB: the global invariant is this:
214 -- *** the top level bindings are never cloned, and are always unique ***
216 -- We sort them into dependency order, but applying transformation rules may
217 -- make something at the top refer to something at the bottom:
221 -- RULE: p (q x) = h x
223 -- Applying this rule makes f refer to h, although it doesn't appear to in the
224 -- source program. Our solution is to do this occasional glom-together step,
225 -- just once per overall simplfication step.
227 let { recd_binds = [Rec (flattenBinds binds)] };
229 (termination_msg, it_count, counts_out, binds') <- iteration us 1 zeroSimplCount recd_binds;
231 dumpIfSet (opt_D_verbose_core2core && opt_D_dump_simpl_stats)
232 "Simplifier statistics"
233 (vcat [text termination_msg <+> text "after" <+> ppr it_count <+> text "iterations",
235 pprSimplCount counts_out]);
238 (opt_D_verbose_core2core && not opt_D_dump_simpl_iterations)
241 return (counts_out, binds')
244 max_iterations = getSimplIntSwitch sw_chkr MaxSimplifierIterations
245 black_list_fn = blackListed rule_lhs_fvs (intSwitchSet sw_chkr SimplInlinePhase)
247 core_iter_dump binds | opt_D_verbose_core2core = pprCoreBindings binds
250 iteration us iteration_no counts binds
252 -- Occurrence analysis
253 let { tagged_binds = _scc_ "OccAnal" occurAnalyseBinds binds } ;
255 dumpIfSet opt_D_dump_occur_anal "Occurrence analysis"
256 (pprCoreBindings tagged_binds);
259 let { (binds', counts') = initSmpl sw_chkr us1 imported_rule_ids
261 (simplTopBinds tagged_binds);
262 -- The imported_rule_ids are used by initSmpl to initialise
263 -- the in-scope set. That way, the simplifier will change any
264 -- occurrences of the imported id to the one in the imported_rule_ids
265 -- set, which are decorated with their rules.
267 all_counts = counts `plusSimplCount` counts'
270 -- Stop if nothing happened; don't dump output
271 if isZeroSimplCount counts' then
272 return ("Simplifier reached fixed point", iteration_no, all_counts, binds')
275 -- Dump the result of this iteration
276 dumpIfSet opt_D_dump_simpl_iterations
277 ("Simplifier iteration " ++ show iteration_no
278 ++ " out of " ++ show max_iterations)
279 (pprSimplCount counts') ;
281 if opt_D_dump_simpl_iterations then
282 endPass ("Simplifier iteration " ++ show iteration_no ++ " result")
283 opt_D_verbose_core2core
288 -- Stop if we've run out of iterations
289 if iteration_no == max_iterations then
292 if max_iterations > 2 then
293 hPutStr stderr ("NOTE: Simplifier still going after " ++
294 show max_iterations ++
295 " iterations; bailing out.\n")
300 return ("Simplifier baled out", iteration_no, all_counts, binds')
304 else iteration us2 (iteration_no + 1) all_counts binds'
307 (us1, us2) = splitUniqSupply us
311 %************************************************************************
313 \subsection{PostSimplification}
315 %************************************************************************
317 Several tasks are performed by the post-simplification pass
319 1. Make the representation of NoRep literals explicit, and
320 float their bindings to the top level. We only do the floating
321 part for NoRep lits inside a lambda (else no gain). We need to
322 take care with let x = "foo" in e
323 that we don't end up with a silly binding
325 with a floated "foo". What a bore.
327 4. Do eta reduction for lambda abstractions appearing in:
328 - the RHS of case alternatives
331 These will otherwise turn into local bindings during Core->STG;
332 better to nuke them if possible. (In general the simplifier does
333 eta expansion not eta reduction, up to this point. It does eta
334 on the RHSs of bindings but not the RHSs of case alternatives and
338 ------------------- NOT DONE ANY MORE ------------------------
339 [March 98] Indirections are now elimianted by the occurrence analyser
340 1. Eliminate indirections. The point here is to transform
346 [Dec 98] [Not now done because there is no penalty in the code
347 generator for using the former form]
349 case x of {...; x' -> ...x'...}
351 case x of {...; _ -> ...x... }
352 See notes in SimplCase.lhs, near simplDefault for the reasoning here.
353 --------------------------------------------------------------
358 NOT ENABLED AT THE MOMENT (because the floated Ids are global-ish
359 things, and we need local Ids for non-floated stuff):
361 Don't float stuff out of a binder that's marked as a bottoming Id.
362 Reason: it doesn't do any good, and creates more CAFs that increase
371 f' = unpackCString# "string"
374 hence f' and f become CAFs. Instead, the special case for
375 tidyTopBinding below makes sure this comes out as
377 f = let f' = unpackCString# "string" in error f'
379 and we can safely ignore f as a CAF, since it can only ever be entered once.
384 doPostSimplification :: UniqSupply -> [CoreBind] -> IO [CoreBind]
385 doPostSimplification us binds_in
387 beginPass "Post-simplification pass"
388 let binds_out = initPM us (postSimplTopBinds binds_in)
389 endPass "Post-simplification pass" opt_D_verbose_core2core binds_out
391 postSimplTopBinds :: [CoreBind] -> PostM [CoreBind]
392 postSimplTopBinds binds
393 = mapPM postSimplTopBind binds `thenPM` \ binds' ->
394 returnPM (bagToList (unionManyBags binds'))
396 postSimplTopBind :: CoreBind -> PostM (Bag CoreBind)
397 postSimplTopBind (NonRec bndr rhs)
398 | isBottomingId bndr -- Don't lift out floats for bottoming Ids
400 = getFloatsPM (postSimplExpr rhs) `thenPM` \ (rhs', floats) ->
401 returnPM (unitBag (NonRec bndr (foldrBag Let rhs' floats)))
403 postSimplTopBind bind
404 = getFloatsPM (postSimplBind bind) `thenPM` \ (bind', floats) ->
405 returnPM (floats `snocBag` bind')
407 postSimplBind (NonRec bndr rhs)
408 = postSimplExpr rhs `thenPM` \ rhs' ->
409 returnPM (NonRec bndr rhs')
411 postSimplBind (Rec pairs)
412 = mapPM postSimplExpr rhss `thenPM` \ rhss' ->
413 returnPM (Rec (bndrs `zip` rhss'))
415 (bndrs, rhss) = unzip pairs
422 postSimplExpr (Var v) = returnPM (Var v)
423 postSimplExpr (Type ty) = returnPM (Type ty)
425 postSimplExpr (App fun arg)
426 = postSimplExpr fun `thenPM` \ fun' ->
427 postSimplExpr arg `thenPM` \ arg' ->
428 returnPM (App fun' arg')
430 postSimplExpr (Con (Literal lit) args)
431 = ASSERT( null args )
432 litToRep lit `thenPM` \ (lit_ty, lit_expr) ->
433 getInsideLambda `thenPM` \ in_lam ->
434 if in_lam && not (exprIsTrivial lit_expr) then
435 -- It must have been a no-rep literal with a
436 -- non-trivial representation; and we're inside a lambda;
437 -- so float it to the top
438 addTopFloat lit_ty lit_expr `thenPM` \ v ->
443 postSimplExpr (Con con args)
444 = mapPM postSimplExpr args `thenPM` \ args' ->
445 returnPM (Con con args')
447 postSimplExpr (Lam bndr body)
448 = insideLambda bndr $
449 postSimplExpr body `thenPM` \ body' ->
450 returnPM (Lam bndr body')
452 postSimplExpr (Let bind body)
453 = postSimplBind bind `thenPM` \ bind' ->
454 postSimplExprEta body `thenPM` \ body' ->
455 returnPM (Let bind' body')
457 postSimplExpr (Note note body)
458 = postSimplExpr body `thenPM` \ body' ->
459 -- Do *not* call postSimplExprEta here
460 -- We don't want to turn f = \x -> coerce t (\y -> f x y)
461 -- into f = \x -> coerce t (f x)
462 -- because then f has a lower arity.
463 -- This is not only bad in general, it causes the arity to
464 -- not match the [Demand] on an Id,
465 -- which confuses the importer of this module.
466 returnPM (Note note body')
468 postSimplExpr (Case scrut case_bndr alts)
469 = postSimplExpr scrut `thenPM` \ scrut' ->
470 mapPM ps_alt alts `thenPM` \ alts' ->
471 returnPM (Case scrut' case_bndr alts')
473 ps_alt (con,bndrs,rhs) = postSimplExprEta rhs `thenPM` \ rhs' ->
474 returnPM (con, bndrs, rhs')
476 postSimplExprEta e = postSimplExpr e `thenPM` \ e' ->
477 returnPM (etaCoreExpr e')
481 %************************************************************************
483 \subsection[coreToStg-lits]{Converting literals}
485 %************************************************************************
487 Literals: the NoRep kind need to be de-no-rep'd.
488 We always replace them with a simple variable, and float a suitable
489 binding out to the top level.
492 litToRep :: Literal -> PostM (Type, CoreExpr)
494 litToRep (NoRepStr s ty)
497 rhs = if (any is_NUL (_UNPK_ s))
499 then -- Must cater for NULs in literal string
500 mkApps (Var unpackCString2Id)
502 mkLit (mkMachInt (toInteger (_LENGTH_ s)))]
504 else -- No NULs in the string
505 App (Var unpackCStringId) (mkLit (MachStr s))
510 If an Integer is small enough (Haskell implementations must support
511 Ints in the range $[-2^29+1, 2^29-1]$), wrap it up in @int2Integer@;
512 otherwise, wrap with @addr2Integer@.
515 litToRep (NoRepInteger i integer_ty)
516 = returnPM (integer_ty, rhs)
518 rhs | i >= tARGET_MIN_INT && -- Small enough, so start from an Int
520 = Con (DataCon smallIntegerDataCon) [Con (Literal (mkMachInt i)) []]
522 | otherwise -- Big, so start from a string
523 = App (Var addr2IntegerId) (Con (Literal (MachStr (_PK_ (show i)))) [])
526 litToRep (NoRepRational r rational_ty)
527 = postSimplExpr (mkLit (NoRepInteger (numerator r) integer_ty)) `thenPM` \ num_arg ->
528 postSimplExpr (mkLit (NoRepInteger (denominator r) integer_ty)) `thenPM` \ denom_arg ->
529 returnPM (rational_ty, mkConApp ratio_data_con [Type integer_ty, num_arg, denom_arg])
531 (ratio_data_con, integer_ty)
532 = case (splitAlgTyConApp_maybe rational_ty) of
533 Just (tycon, [i_ty], [con])
534 -> ASSERT(isIntegerTy i_ty && getUnique tycon == ratioTyConKey)
537 _ -> (panic "ratio_data_con", panic "integer_ty")
539 litToRep other_lit = returnPM (literalType other_lit, mkLit other_lit)
543 %************************************************************************
545 \subsection{The monad}
547 %************************************************************************
550 type PostM a = Bool -- True <=> inside a *value* lambda
551 -> (UniqSupply, Bag CoreBind) -- Unique supply and Floats in
552 -> (a, (UniqSupply, Bag CoreBind))
554 initPM :: UniqSupply -> PostM a -> a
556 = case m False {- not inside lambda -} (us, emptyBag) of
557 (result, _) -> result
559 returnPM v in_lam usf = (v, usf)
560 thenPM m k in_lam usf = case m in_lam usf of
561 (r, usf') -> k r in_lam usf'
563 mapPM f [] = returnPM []
564 mapPM f (x:xs) = f x `thenPM` \ r ->
565 mapPM f xs `thenPM` \ rs ->
568 insideLambda :: CoreBndr -> PostM a -> PostM a
569 insideLambda bndr m in_lam usf | isId bndr = m True usf
570 | otherwise = m in_lam usf
572 getInsideLambda :: PostM Bool
573 getInsideLambda in_lam usf = (in_lam, usf)
575 getFloatsPM :: PostM a -> PostM (a, Bag CoreBind)
576 getFloatsPM m in_lam (us, floats)
578 (a, (us', floats')) = m in_lam (us, emptyBag)
580 ((a, floats'), (us', floats))
582 addTopFloat :: Type -> CoreExpr -> PostM Id
583 addTopFloat lit_ty lit_rhs in_lam (us, floats)
585 (us1, us2) = splitUniqSupply us
586 uniq = uniqFromSupply us1
587 lit_id = mkSysLocal SLIT("lf") uniq lit_ty
589 (lit_id, (us2, floats `snocBag` NonRec lit_id lit_rhs))