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
212 let { recd_binds = [Rec (flattenBinds binds)] };
214 (termination_msg, it_count, counts_out, binds') <- iteration us 1 zeroSimplCount recd_binds;
216 dumpIfSet (opt_D_verbose_core2core && opt_D_dump_simpl_stats)
217 "Simplifier statistics"
218 (vcat [text termination_msg <+> text "after" <+> ppr it_count <+> text "iterations",
220 pprSimplCount counts_out]);
223 (opt_D_verbose_core2core && not opt_D_dump_simpl_iterations)
226 return (counts_out, binds')
229 max_iterations = getSimplIntSwitch sw_chkr MaxSimplifierIterations
230 black_list_fn = blackListed rule_lhs_fvs (intSwitchSet sw_chkr SimplInlinePhase)
232 core_iter_dump binds | opt_D_verbose_core2core = pprCoreBindings binds
235 iteration us iteration_no counts binds
237 -- Occurrence analysis
238 let { tagged_binds = _scc_ "OccAnal" occurAnalyseBinds binds } ;
240 dumpIfSet opt_D_dump_occur_anal "Occurrence analysis"
241 (pprCoreBindings tagged_binds);
244 let { (binds', counts') = initSmpl sw_chkr us1 imported_rule_ids
246 (simplTopBinds tagged_binds);
247 all_counts = counts `plusSimplCount` counts'
250 -- Stop if nothing happened; don't dump output
251 if isZeroSimplCount counts' then
252 return ("Simplifier reached fixed point", iteration_no, all_counts, binds')
255 -- Dump the result of this iteration
256 dumpIfSet opt_D_dump_simpl_iterations
257 ("Simplifier iteration " ++ show iteration_no
258 ++ " out of " ++ show max_iterations)
259 (pprSimplCount counts') ;
261 if opt_D_dump_simpl_iterations then
262 endPass ("Simplifier iteration " ++ show iteration_no ++ " result")
263 opt_D_verbose_core2core
268 -- Stop if we've run out of iterations
269 if iteration_no == max_iterations then
271 if max_iterations > 2 then
272 hPutStr stderr ("NOTE: Simplifier still going after " ++
273 show max_iterations ++
274 " iterations; bailing out.\n")
277 return ("Simplifier baled out", iteration_no, all_counts, binds')
281 else iteration us2 (iteration_no + 1) all_counts binds'
284 (us1, us2) = splitUniqSupply us
288 %************************************************************************
290 \subsection{PostSimplification}
292 %************************************************************************
294 Several tasks are performed by the post-simplification pass
296 1. Make the representation of NoRep literals explicit, and
297 float their bindings to the top level. We only do the floating
298 part for NoRep lits inside a lambda (else no gain). We need to
299 take care with let x = "foo" in e
300 that we don't end up with a silly binding
302 with a floated "foo". What a bore.
304 4. Do eta reduction for lambda abstractions appearing in:
305 - the RHS of case alternatives
308 These will otherwise turn into local bindings during Core->STG;
309 better to nuke them if possible. (In general the simplifier does
310 eta expansion not eta reduction, up to this point. It does eta
311 on the RHSs of bindings but not the RHSs of case alternatives and
315 ------------------- NOT DONE ANY MORE ------------------------
316 [March 98] Indirections are now elimianted by the occurrence analyser
317 1. Eliminate indirections. The point here is to transform
323 [Dec 98] [Not now done because there is no penalty in the code
324 generator for using the former form]
326 case x of {...; x' -> ...x'...}
328 case x of {...; _ -> ...x... }
329 See notes in SimplCase.lhs, near simplDefault for the reasoning here.
330 --------------------------------------------------------------
335 NOT ENABLED AT THE MOMENT (because the floated Ids are global-ish
336 things, and we need local Ids for non-floated stuff):
338 Don't float stuff out of a binder that's marked as a bottoming Id.
339 Reason: it doesn't do any good, and creates more CAFs that increase
348 f' = unpackCString# "string"
351 hence f' and f become CAFs. Instead, the special case for
352 tidyTopBinding below makes sure this comes out as
354 f = let f' = unpackCString# "string" in error f'
356 and we can safely ignore f as a CAF, since it can only ever be entered once.
361 doPostSimplification :: UniqSupply -> [CoreBind] -> IO [CoreBind]
362 doPostSimplification us binds_in
364 beginPass "Post-simplification pass"
365 let binds_out = initPM us (postSimplTopBinds binds_in)
366 endPass "Post-simplification pass" opt_D_verbose_core2core binds_out
368 postSimplTopBinds :: [CoreBind] -> PostM [CoreBind]
369 postSimplTopBinds binds
370 = mapPM postSimplTopBind binds `thenPM` \ binds' ->
371 returnPM (bagToList (unionManyBags binds'))
373 postSimplTopBind :: CoreBind -> PostM (Bag CoreBind)
374 postSimplTopBind (NonRec bndr rhs)
375 | isBottomingId bndr -- Don't lift out floats for bottoming Ids
377 = getFloatsPM (postSimplExpr rhs) `thenPM` \ (rhs', floats) ->
378 returnPM (unitBag (NonRec bndr (foldrBag Let rhs' floats)))
380 postSimplTopBind bind
381 = getFloatsPM (postSimplBind bind) `thenPM` \ (bind', floats) ->
382 returnPM (floats `snocBag` bind')
384 postSimplBind (NonRec bndr rhs)
385 = postSimplExpr rhs `thenPM` \ rhs' ->
386 returnPM (NonRec bndr rhs')
388 postSimplBind (Rec pairs)
389 = mapPM postSimplExpr rhss `thenPM` \ rhss' ->
390 returnPM (Rec (bndrs `zip` rhss'))
392 (bndrs, rhss) = unzip pairs
399 postSimplExpr (Var v) = returnPM (Var v)
400 postSimplExpr (Type ty) = returnPM (Type ty)
402 postSimplExpr (App fun arg)
403 = postSimplExpr fun `thenPM` \ fun' ->
404 postSimplExpr arg `thenPM` \ arg' ->
405 returnPM (App fun' arg')
407 postSimplExpr (Con (Literal lit) args)
408 = ASSERT( null args )
409 litToRep lit `thenPM` \ (lit_ty, lit_expr) ->
410 getInsideLambda `thenPM` \ in_lam ->
411 if in_lam && not (exprIsTrivial lit_expr) then
412 -- It must have been a no-rep literal with a
413 -- non-trivial representation; and we're inside a lambda;
414 -- so float it to the top
415 addTopFloat lit_ty lit_expr `thenPM` \ v ->
420 postSimplExpr (Con con args)
421 = mapPM postSimplExpr args `thenPM` \ args' ->
422 returnPM (Con con args')
424 postSimplExpr (Lam bndr body)
425 = insideLambda bndr $
426 postSimplExpr body `thenPM` \ body' ->
427 returnPM (Lam bndr body')
429 postSimplExpr (Let bind body)
430 = postSimplBind bind `thenPM` \ bind' ->
431 postSimplExprEta body `thenPM` \ body' ->
432 returnPM (Let bind' body')
434 postSimplExpr (Note note body)
435 = postSimplExprEta body `thenPM` \ body' ->
436 returnPM (Note note body')
438 postSimplExpr (Case scrut case_bndr alts)
439 = postSimplExpr scrut `thenPM` \ scrut' ->
440 mapPM ps_alt alts `thenPM` \ alts' ->
441 returnPM (Case scrut' case_bndr alts')
443 ps_alt (con,bndrs,rhs) = postSimplExprEta rhs `thenPM` \ rhs' ->
444 returnPM (con, bndrs, rhs')
446 postSimplExprEta e = postSimplExpr e `thenPM` \ e' ->
447 returnPM (etaCoreExpr e')
451 %************************************************************************
453 \subsection[coreToStg-lits]{Converting literals}
455 %************************************************************************
457 Literals: the NoRep kind need to be de-no-rep'd.
458 We always replace them with a simple variable, and float a suitable
459 binding out to the top level.
462 litToRep :: Literal -> PostM (Type, CoreExpr)
464 litToRep (NoRepStr s ty)
467 rhs = if (any is_NUL (_UNPK_ s))
469 then -- Must cater for NULs in literal string
470 mkApps (Var unpackCString2Id)
472 mkLit (mkMachInt (toInteger (_LENGTH_ s)))]
474 else -- No NULs in the string
475 App (Var unpackCStringId) (mkLit (MachStr s))
480 If an Integer is small enough (Haskell implementations must support
481 Ints in the range $[-2^29+1, 2^29-1]$), wrap it up in @int2Integer@;
482 otherwise, wrap with @addr2Integer@.
485 litToRep (NoRepInteger i integer_ty)
486 = returnPM (integer_ty, rhs)
488 rhs | i > tARGET_MIN_INT && -- Small enough, so start from an Int
490 = Con (DataCon smallIntegerDataCon) [Con (Literal (mkMachInt i)) []]
492 | otherwise -- Big, so start from a string
493 = App (Var addr2IntegerId) (Con (Literal (MachStr (_PK_ (show i)))) [])
496 litToRep (NoRepRational r rational_ty)
497 = postSimplExpr (mkLit (NoRepInteger (numerator r) integer_ty)) `thenPM` \ num_arg ->
498 postSimplExpr (mkLit (NoRepInteger (denominator r) integer_ty)) `thenPM` \ denom_arg ->
499 returnPM (rational_ty, mkConApp ratio_data_con [Type integer_ty, num_arg, denom_arg])
501 (ratio_data_con, integer_ty)
502 = case (splitAlgTyConApp_maybe rational_ty) of
503 Just (tycon, [i_ty], [con])
504 -> ASSERT(isIntegerTy i_ty && getUnique tycon == ratioTyConKey)
507 _ -> (panic "ratio_data_con", panic "integer_ty")
509 litToRep other_lit = returnPM (literalType other_lit, mkLit other_lit)
513 %************************************************************************
515 \subsection{The monad}
517 %************************************************************************
520 type PostM a = Bool -- True <=> inside a *value* lambda
521 -> (UniqSupply, Bag CoreBind) -- Unique supply and Floats in
522 -> (a, (UniqSupply, Bag CoreBind))
524 initPM :: UniqSupply -> PostM a -> a
526 = case m False {- not inside lambda -} (us, emptyBag) of
527 (result, _) -> result
529 returnPM v in_lam usf = (v, usf)
530 thenPM m k in_lam usf = case m in_lam usf of
531 (r, usf') -> k r in_lam usf'
533 mapPM f [] = returnPM []
534 mapPM f (x:xs) = f x `thenPM` \ r ->
535 mapPM f xs `thenPM` \ rs ->
538 insideLambda :: CoreBndr -> PostM a -> PostM a
539 insideLambda bndr m in_lam usf | isId bndr = m True usf
540 | otherwise = m in_lam usf
542 getInsideLambda :: PostM Bool
543 getInsideLambda in_lam usf = (in_lam, usf)
545 getFloatsPM :: PostM a -> PostM (a, Bag CoreBind)
546 getFloatsPM m in_lam (us, floats)
548 (a, (us', floats')) = m in_lam (us, emptyBag)
550 ((a, floats'), (us', floats))
552 addTopFloat :: Type -> CoreExpr -> PostM Id
553 addTopFloat lit_ty lit_rhs in_lam (us, floats)
555 (us1, us2) = splitUniqSupply us
556 uniq = uniqFromSupply us1
557 lit_id = mkSysLocal SLIT("lf") uniq lit_ty
559 (lit_id, (us2, floats `snocBag` NonRec lit_id lit_rhs))