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 all_counts = counts `plusSimplCount` counts'
265 -- Stop if nothing happened; don't dump output
266 if isZeroSimplCount counts' then
267 return ("Simplifier reached fixed point", iteration_no, all_counts, binds')
270 -- Dump the result of this iteration
271 dumpIfSet opt_D_dump_simpl_iterations
272 ("Simplifier iteration " ++ show iteration_no
273 ++ " out of " ++ show max_iterations)
274 (pprSimplCount counts') ;
276 if opt_D_dump_simpl_iterations then
277 endPass ("Simplifier iteration " ++ show iteration_no ++ " result")
278 opt_D_verbose_core2core
283 -- Stop if we've run out of iterations
284 if iteration_no == max_iterations then
286 if max_iterations > 2 then
287 hPutStr stderr ("NOTE: Simplifier still going after " ++
288 show max_iterations ++
289 " iterations; bailing out.\n")
292 return ("Simplifier baled out", iteration_no, all_counts, binds')
296 else iteration us2 (iteration_no + 1) all_counts binds'
299 (us1, us2) = splitUniqSupply us
303 %************************************************************************
305 \subsection{PostSimplification}
307 %************************************************************************
309 Several tasks are performed by the post-simplification pass
311 1. Make the representation of NoRep literals explicit, and
312 float their bindings to the top level. We only do the floating
313 part for NoRep lits inside a lambda (else no gain). We need to
314 take care with let x = "foo" in e
315 that we don't end up with a silly binding
317 with a floated "foo". What a bore.
319 4. Do eta reduction for lambda abstractions appearing in:
320 - the RHS of case alternatives
323 These will otherwise turn into local bindings during Core->STG;
324 better to nuke them if possible. (In general the simplifier does
325 eta expansion not eta reduction, up to this point. It does eta
326 on the RHSs of bindings but not the RHSs of case alternatives and
330 ------------------- NOT DONE ANY MORE ------------------------
331 [March 98] Indirections are now elimianted by the occurrence analyser
332 1. Eliminate indirections. The point here is to transform
338 [Dec 98] [Not now done because there is no penalty in the code
339 generator for using the former form]
341 case x of {...; x' -> ...x'...}
343 case x of {...; _ -> ...x... }
344 See notes in SimplCase.lhs, near simplDefault for the reasoning here.
345 --------------------------------------------------------------
350 NOT ENABLED AT THE MOMENT (because the floated Ids are global-ish
351 things, and we need local Ids for non-floated stuff):
353 Don't float stuff out of a binder that's marked as a bottoming Id.
354 Reason: it doesn't do any good, and creates more CAFs that increase
363 f' = unpackCString# "string"
366 hence f' and f become CAFs. Instead, the special case for
367 tidyTopBinding below makes sure this comes out as
369 f = let f' = unpackCString# "string" in error f'
371 and we can safely ignore f as a CAF, since it can only ever be entered once.
376 doPostSimplification :: UniqSupply -> [CoreBind] -> IO [CoreBind]
377 doPostSimplification us binds_in
379 beginPass "Post-simplification pass"
380 let binds_out = initPM us (postSimplTopBinds binds_in)
381 endPass "Post-simplification pass" opt_D_verbose_core2core binds_out
383 postSimplTopBinds :: [CoreBind] -> PostM [CoreBind]
384 postSimplTopBinds binds
385 = mapPM postSimplTopBind binds `thenPM` \ binds' ->
386 returnPM (bagToList (unionManyBags binds'))
388 postSimplTopBind :: CoreBind -> PostM (Bag CoreBind)
389 postSimplTopBind (NonRec bndr rhs)
390 | isBottomingId bndr -- Don't lift out floats for bottoming Ids
392 = getFloatsPM (postSimplExpr rhs) `thenPM` \ (rhs', floats) ->
393 returnPM (unitBag (NonRec bndr (foldrBag Let rhs' floats)))
395 postSimplTopBind bind
396 = getFloatsPM (postSimplBind bind) `thenPM` \ (bind', floats) ->
397 returnPM (floats `snocBag` bind')
399 postSimplBind (NonRec bndr rhs)
400 = postSimplExpr rhs `thenPM` \ rhs' ->
401 returnPM (NonRec bndr rhs')
403 postSimplBind (Rec pairs)
404 = mapPM postSimplExpr rhss `thenPM` \ rhss' ->
405 returnPM (Rec (bndrs `zip` rhss'))
407 (bndrs, rhss) = unzip pairs
414 postSimplExpr (Var v) = returnPM (Var v)
415 postSimplExpr (Type ty) = returnPM (Type ty)
417 postSimplExpr (App fun arg)
418 = postSimplExpr fun `thenPM` \ fun' ->
419 postSimplExpr arg `thenPM` \ arg' ->
420 returnPM (App fun' arg')
422 postSimplExpr (Con (Literal lit) args)
423 = ASSERT( null args )
424 litToRep lit `thenPM` \ (lit_ty, lit_expr) ->
425 getInsideLambda `thenPM` \ in_lam ->
426 if in_lam && not (exprIsTrivial lit_expr) then
427 -- It must have been a no-rep literal with a
428 -- non-trivial representation; and we're inside a lambda;
429 -- so float it to the top
430 addTopFloat lit_ty lit_expr `thenPM` \ v ->
435 postSimplExpr (Con con args)
436 = mapPM postSimplExpr args `thenPM` \ args' ->
437 returnPM (Con con args')
439 postSimplExpr (Lam bndr body)
440 = insideLambda bndr $
441 postSimplExpr body `thenPM` \ body' ->
442 returnPM (Lam bndr body')
444 postSimplExpr (Let bind body)
445 = postSimplBind bind `thenPM` \ bind' ->
446 postSimplExprEta body `thenPM` \ body' ->
447 returnPM (Let bind' body')
449 postSimplExpr (Note note body)
450 = postSimplExprEta body `thenPM` \ body' ->
451 returnPM (Note note body')
453 postSimplExpr (Case scrut case_bndr alts)
454 = postSimplExpr scrut `thenPM` \ scrut' ->
455 mapPM ps_alt alts `thenPM` \ alts' ->
456 returnPM (Case scrut' case_bndr alts')
458 ps_alt (con,bndrs,rhs) = postSimplExprEta rhs `thenPM` \ rhs' ->
459 returnPM (con, bndrs, rhs')
461 postSimplExprEta e = postSimplExpr e `thenPM` \ e' ->
462 returnPM (etaCoreExpr e')
466 %************************************************************************
468 \subsection[coreToStg-lits]{Converting literals}
470 %************************************************************************
472 Literals: the NoRep kind need to be de-no-rep'd.
473 We always replace them with a simple variable, and float a suitable
474 binding out to the top level.
477 litToRep :: Literal -> PostM (Type, CoreExpr)
479 litToRep (NoRepStr s ty)
482 rhs = if (any is_NUL (_UNPK_ s))
484 then -- Must cater for NULs in literal string
485 mkApps (Var unpackCString2Id)
487 mkLit (mkMachInt (toInteger (_LENGTH_ s)))]
489 else -- No NULs in the string
490 App (Var unpackCStringId) (mkLit (MachStr s))
495 If an Integer is small enough (Haskell implementations must support
496 Ints in the range $[-2^29+1, 2^29-1]$), wrap it up in @int2Integer@;
497 otherwise, wrap with @addr2Integer@.
500 litToRep (NoRepInteger i integer_ty)
501 = returnPM (integer_ty, rhs)
503 rhs | i > tARGET_MIN_INT && -- Small enough, so start from an Int
505 = Con (DataCon smallIntegerDataCon) [Con (Literal (mkMachInt i)) []]
507 | otherwise -- Big, so start from a string
508 = App (Var addr2IntegerId) (Con (Literal (MachStr (_PK_ (show i)))) [])
511 litToRep (NoRepRational r rational_ty)
512 = postSimplExpr (mkLit (NoRepInteger (numerator r) integer_ty)) `thenPM` \ num_arg ->
513 postSimplExpr (mkLit (NoRepInteger (denominator r) integer_ty)) `thenPM` \ denom_arg ->
514 returnPM (rational_ty, mkConApp ratio_data_con [Type integer_ty, num_arg, denom_arg])
516 (ratio_data_con, integer_ty)
517 = case (splitAlgTyConApp_maybe rational_ty) of
518 Just (tycon, [i_ty], [con])
519 -> ASSERT(isIntegerTy i_ty && getUnique tycon == ratioTyConKey)
522 _ -> (panic "ratio_data_con", panic "integer_ty")
524 litToRep other_lit = returnPM (literalType other_lit, mkLit other_lit)
528 %************************************************************************
530 \subsection{The monad}
532 %************************************************************************
535 type PostM a = Bool -- True <=> inside a *value* lambda
536 -> (UniqSupply, Bag CoreBind) -- Unique supply and Floats in
537 -> (a, (UniqSupply, Bag CoreBind))
539 initPM :: UniqSupply -> PostM a -> a
541 = case m False {- not inside lambda -} (us, emptyBag) of
542 (result, _) -> result
544 returnPM v in_lam usf = (v, usf)
545 thenPM m k in_lam usf = case m in_lam usf of
546 (r, usf') -> k r in_lam usf'
548 mapPM f [] = returnPM []
549 mapPM f (x:xs) = f x `thenPM` \ r ->
550 mapPM f xs `thenPM` \ rs ->
553 insideLambda :: CoreBndr -> PostM a -> PostM a
554 insideLambda bndr m in_lam usf | isId bndr = m True usf
555 | otherwise = m in_lam usf
557 getInsideLambda :: PostM Bool
558 getInsideLambda in_lam usf = (in_lam, usf)
560 getFloatsPM :: PostM a -> PostM (a, Bag CoreBind)
561 getFloatsPM m in_lam (us, floats)
563 (a, (us', floats')) = m in_lam (us, emptyBag)
565 ((a, floats'), (us', floats))
567 addTopFloat :: Type -> CoreExpr -> PostM Id
568 addTopFloat lit_ty lit_rhs in_lam (us, floats)
570 (us1, us2) = splitUniqSupply us
571 uniq = uniqFromSupply us1
572 lit_id = mkSysLocal SLIT("lf") uniq lit_ty
574 (lit_id, (us2, floats `snocBag` NonRec lit_id lit_rhs))