X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FsimplCore%2FSimplCore.lhs;h=a386a3d6b021e5138480656f480042fff77dbeae;hb=28a464a75e14cece5db40f2765a29348273ff2d2;hp=f3a5d145b8c1d98de39ef1fac0f520aa354f31c4;hpb=d4e0a55c3761544989209a2180d6d0489470db3d;p=ghc-hetmet.git diff --git a/ghc/compiler/simplCore/SimplCore.lhs b/ghc/compiler/simplCore/SimplCore.lhs index f3a5d14..a386a3d 100644 --- a/ghc/compiler/simplCore/SimplCore.lhs +++ b/ghc/compiler/simplCore/SimplCore.lhs @@ -4,73 +4,55 @@ \section[SimplCore]{Driver for simplifying @Core@ programs} \begin{code} -module SimplCore ( core2core ) where +module SimplCore ( core2core, simplifyExpr ) where #include "HsVersions.h" -import CmdLineOpts ( CoreToDo(..), SimplifierSwitch(..), - SwitchResult(..), switchIsOn, intSwitchSet, - opt_D_dump_occur_anal, opt_D_dump_rules, - opt_D_dump_simpl_iterations, - opt_D_dump_simpl_stats, - opt_D_dump_simpl, opt_D_dump_rules, - opt_D_verbose_core2core, - opt_D_dump_occur_anal, - opt_UsageSPOn, - ) -import CoreLint ( beginPass, endPass ) +import DynFlags ( CoreToDo(..), SimplifierSwitch(..), + SimplifierMode(..), DynFlags, DynFlag(..), dopt, + getCoreToDo ) import CoreSyn +import HscTypes ( HscEnv(..), ModGuts(..), ExternalPackageState(..), + Dependencies( dep_mods ), + hscEPS, hptRules ) import CSE ( cseProgram ) -import Rules ( RuleBase, ProtoCoreRule(..), pprProtoCoreRule, prepareRuleBase, orphanRule ) -import CoreUnfold -import PprCore ( pprCoreBindings ) -import OccurAnal ( occurAnalyseBinds ) -import CoreUtils ( exprIsTrivial, etaReduceExpr ) +import Rules ( RuleBase, emptyRuleBase, mkRuleBase, unionRuleBase, + extendRuleBaseList, pprRuleBase, ruleCheckProgram, + addSpecInfo, addIdSpecialisations ) +import PprCore ( pprCoreBindings, pprCoreExpr, pprRules ) +import OccurAnal ( occurAnalysePgm, occurAnalyseExpr ) +import IdInfo ( setNewStrictnessInfo, newStrictnessInfo, + setWorkerInfo, workerInfo, + setSpecInfo, specInfo, specInfoRules ) +import CoreUtils ( coreBindsSize ) import Simplify ( simplTopBinds, simplExpr ) -import SimplUtils ( findDefault, simplBinders ) +import SimplEnv ( SimplEnv, simplBinders, mkSimplEnv, setInScopeSet ) import SimplMonad -import Literal ( Literal(..), literalType, mkMachInt ) -import ErrUtils ( dumpIfSet ) +import ErrUtils ( dumpIfSet, dumpIfSet_dyn, showPass ) +import CoreLint ( endPass ) import FloatIn ( floatInwards ) import FloatOut ( floatOutwards ) -import Id ( Id, mkSysLocal, mkVanillaId, isBottomingId, isDataConWrapId, - idType, setIdType, idName, idInfo, setIdNoDiscard - ) -import VarEnv +import Id ( Id, modifyIdInfo, idInfo, isExportedId, isLocalId, + idSpecialisation, idName ) import VarSet -import Module ( Module ) -import Name ( mkLocalName, tidyOccName, tidyTopName, - NamedThing(..), OccName - ) -import TyCon ( TyCon, isDataTyCon ) -import PrelInfo ( unpackCStringId, unpackCString2Id, addr2IntegerId ) -import PrelRules ( builtinRules ) -import Type ( Type, - isUnLiftedType, - tidyType, tidyTypes, tidyTopType, tidyTyVar, tidyTyVars, - Type - ) -import TysWiredIn ( smallIntegerDataCon, isIntegerTy ) +import VarEnv +import NameEnv ( lookupNameEnv ) import LiberateCase ( liberateCase ) import SAT ( doStaticArgs ) import Specialise ( specProgram) -import UsageSPInf ( doUsageSPInf ) -import StrictAnal ( saBinds ) +import SpecConstr ( specConstrProgram) +import DmdAnal ( dmdAnalPgm ) import WorkWrap ( wwTopBinds ) +#ifdef OLD_STRICTNESS +import StrictAnal ( saBinds ) import CprAnalyse ( cprAnalyse ) +#endif -import Unique ( Unique, Uniquable(..), - ratioTyConKey - ) -import UniqSupply ( UniqSupply, mkSplitUniqSupply, splitUniqSupply, uniqFromSupply ) -import Util ( mapAccumL ) -import SrcLoc ( noSrcLoc ) -import Bag -import Maybes +import UniqSupply ( UniqSupply, mkSplitUniqSupply, splitUniqSupply ) import IO ( hPutStr, stderr ) import Outputable - -import Ratio ( numerator, denominator ) +import List ( partition ) +import Maybes ( orElse ) \end{code} %************************************************************************ @@ -80,128 +62,304 @@ import Ratio ( numerator, denominator ) %************************************************************************ \begin{code} -core2core :: [CoreToDo] -- Spec of what core-to-core passes to do - -> [CoreBind] -- Binds in - -> [ProtoCoreRule] -- Rules - -> IO ([CoreBind], [ProtoCoreRule]) +core2core :: HscEnv + -> ModGuts + -> IO ModGuts -core2core core_todos binds rules +core2core hsc_env guts = do - us <- mkSplitUniqSupply 's' - let (cp_us, us1) = splitUniqSupply us - (ru_us, ps_us) = splitUniqSupply us1 + let dflags = hsc_dflags hsc_env + core_todos = getCoreToDo dflags - better_rules <- simplRules ru_us rules binds + us <- mkSplitUniqSupply 's' + let (cp_us, ru_us) = splitUniqSupply us - let all_rules = builtinRules ++ better_rules - -- Here is where we add in the built-in rules + -- COMPUTE THE RULE BASE TO USE + (imp_rule_base, guts') <- prepareRules hsc_env guts ru_us - let (binds1, rule_base) = prepareRuleBase binds all_rules + -- DO THE BUSINESS + (stats, guts'') <- doCorePasses hsc_env imp_rule_base cp_us + (zeroSimplCount dflags) + guts' core_todos - -- Do the main business - (stats, processed_binds) <- doCorePasses zeroSimplCount cp_us binds1 - rule_base core_todos - - dumpIfSet opt_D_dump_simpl_stats + dumpIfSet_dyn dflags Opt_D_dump_simpl_stats "Grand total simplifier statistics" (pprSimplCount stats) - -- Return results - return (processed_binds, filter orphanRule better_rules) - + return guts'' + + +simplifyExpr :: DynFlags -- includes spec of what core-to-core passes to do + -> CoreExpr + -> IO CoreExpr +-- simplifyExpr is called by the driver to simplify an +-- expression typed in at the interactive prompt +simplifyExpr dflags expr + = do { + ; showPass dflags "Simplify" + + ; us <- mkSplitUniqSupply 's' + + ; let (expr', _counts) = initSmpl dflags us $ + simplExprGently gentleSimplEnv expr -doCorePasses stats us binds irs [] - = return (stats, binds) + ; dumpIfSet_dyn dflags Opt_D_dump_simpl "Simplified expression" + (pprCoreExpr expr') -doCorePasses stats us binds irs (to_do : to_dos) + ; return expr' + } + +gentleSimplEnv :: SimplEnv +gentleSimplEnv = mkSimplEnv SimplGently + (isAmongSimpl []) + emptyRuleBase + +doCorePasses :: HscEnv + -> RuleBase -- the imported main rule base + -> UniqSupply -- uniques + -> SimplCount -- simplifier stats + -> ModGuts -- local binds in (with rules attached) + -> [CoreToDo] -- which passes to do + -> IO (SimplCount, ModGuts) + +doCorePasses hsc_env rb us stats guts [] + = return (stats, guts) + +doCorePasses hsc_env rb us stats guts (to_do : to_dos) = do - let (us1, us2) = splitUniqSupply us - (stats1, binds1) <- doCorePass us1 binds irs to_do - doCorePasses (stats `plusSimplCount` stats1) us2 binds1 irs to_dos - -doCorePass us binds rb (CoreDoSimplify sw_chkr) = _scc_ "Simplify" simplifyPgm rb sw_chkr us binds -doCorePass us binds rb CoreCSE = _scc_ "CommonSubExpr" noStats (cseProgram binds) -doCorePass us binds rb CoreLiberateCase = _scc_ "LiberateCase" noStats (liberateCase binds) -doCorePass us binds rb CoreDoFloatInwards = _scc_ "FloatInwards" noStats (floatInwards binds) -doCorePass us binds rb (CoreDoFloatOutwards f) = _scc_ "FloatOutwards" noStats (floatOutwards f us binds) -doCorePass us binds rb CoreDoStaticArgs = _scc_ "StaticArgs" noStats (doStaticArgs us binds) -doCorePass us binds rb CoreDoStrictness = _scc_ "Stranal" noStats (saBinds binds) -doCorePass us binds rb CoreDoWorkerWrapper = _scc_ "WorkWrap" noStats (wwTopBinds us binds) -doCorePass us binds rb CoreDoSpecialising = _scc_ "Specialise" noStats (specProgram us binds) -doCorePass us binds rb CoreDoCPResult = _scc_ "CPResult" noStats (cprAnalyse binds) -doCorePass us binds rb CoreDoPrintCore = _scc_ "PrintCore" noStats (printCore binds) -doCorePass us binds rb CoreDoUSPInf - = _scc_ "CoreUsageSPInf" - if opt_UsageSPOn then - noStats (doUsageSPInf us binds) - else - trace "WARNING: ignoring requested -fusagesp pass; requires -fusagesp-on" $ - noStats (return binds) + let (us1, us2) = splitUniqSupply us + (stats1, guts1) <- doCorePass to_do hsc_env us1 rb guts + doCorePasses hsc_env rb us2 (stats `plusSimplCount` stats1) guts1 to_dos + +doCorePass (CoreDoSimplify mode sws) = _scc_ "Simplify" simplifyPgm mode sws +doCorePass CoreCSE = _scc_ "CommonSubExpr" trBinds cseProgram +doCorePass CoreLiberateCase = _scc_ "LiberateCase" trBinds liberateCase +doCorePass CoreDoFloatInwards = _scc_ "FloatInwards" trBinds floatInwards +doCorePass (CoreDoFloatOutwards f) = _scc_ "FloatOutwards" trBindsU (floatOutwards f) +doCorePass CoreDoStaticArgs = _scc_ "StaticArgs" trBinds doStaticArgs +doCorePass CoreDoStrictness = _scc_ "Stranal" trBinds dmdAnalPgm +doCorePass CoreDoWorkerWrapper = _scc_ "WorkWrap" trBindsU wwTopBinds +doCorePass CoreDoSpecialising = _scc_ "Specialise" trBindsU specProgram +doCorePass CoreDoSpecConstr = _scc_ "SpecConstr" trBindsU specConstrProgram +doCorePass CoreDoGlomBinds = trBinds glomBinds +doCorePass CoreDoPrintCore = observe printCore +doCorePass (CoreDoRuleCheck phase pat) = observe (ruleCheck phase pat) +doCorePass CoreDoNothing = observe (\ _ _ -> return ()) +#ifdef OLD_STRICTNESS +doCorePass CoreDoOldStrictness = _scc_ "OldStrictness" trBinds doOldStrictness +#endif -printCore binds = do dumpIfSet True "Print Core" - (pprCoreBindings binds) - return binds +#ifdef OLD_STRICTNESS +doOldStrictness dfs binds + = do binds1 <- saBinds dfs binds + binds2 <- cprAnalyse dfs binds1 + return binds2 +#endif + +printCore _ binds = dumpIfSet True "Print Core" (pprCoreBindings binds) + +ruleCheck phase pat dflags binds = do showPass dflags "RuleCheck" + printDump (ruleCheckProgram phase pat binds) -noStats thing = do { result <- thing; return (zeroSimplCount, result) } +-- Most passes return no stats and don't change rules +trBinds :: (DynFlags -> [CoreBind] -> IO [CoreBind]) + -> HscEnv -> UniqSupply -> RuleBase -> ModGuts + -> IO (SimplCount, ModGuts) +trBinds do_pass hsc_env us rb guts + = do { binds' <- do_pass dflags (mg_binds guts) + ; return (zeroSimplCount dflags, guts { mg_binds = binds' }) } + where + dflags = hsc_dflags hsc_env + +trBindsU :: (DynFlags -> UniqSupply -> [CoreBind] -> IO [CoreBind]) + -> HscEnv -> UniqSupply -> RuleBase -> ModGuts + -> IO (SimplCount, ModGuts) +trBindsU do_pass hsc_env us rb guts + = do { binds' <- do_pass dflags us (mg_binds guts) + ; return (zeroSimplCount dflags, guts { mg_binds = binds' }) } + where + dflags = hsc_dflags hsc_env + +-- Observer passes just peek; don't modify the bindings at all +observe :: (DynFlags -> [CoreBind] -> IO a) + -> HscEnv -> UniqSupply -> RuleBase -> ModGuts + -> IO (SimplCount, ModGuts) +observe do_pass hsc_env us rb guts + = do { binds <- do_pass dflags (mg_binds guts) + ; return (zeroSimplCount dflags, guts) } + where + dflags = hsc_dflags hsc_env \end{code} + %************************************************************************ %* * \subsection{Dealing with rules} %* * %************************************************************************ -We must do some gentle simplifiation on the template (but not the RHS) -of each rule. The case that forced me to add this was the fold/build rule, -which without simplification looked like: - fold k z (build (/\a. g a)) ==> ... -This doesn't match unless you do eta reduction on the build argument. +-- prepareLocalRuleBase takes the CoreBinds and rules defined in this module. +-- It attaches those rules that are for local Ids to their binders, and +-- returns the remainder attached to Ids in an IdSet. \begin{code} -simplRules :: UniqSupply -> [ProtoCoreRule] -> [CoreBind] -> IO [ProtoCoreRule] -simplRules us rules binds - = do let (better_rules,_) = initSmpl sw_chkr us bind_vars black_list_all (mapSmpl simplRule rules) - - dumpIfSet opt_D_dump_rules - "Transformation rules" - (vcat (map pprProtoCoreRule better_rules)) +prepareRules :: HscEnv + -> ModGuts + -> UniqSupply + -> IO (RuleBase, -- Rule base for imported things, incl + -- (a) rules defined in this module (orphans) + -- (b) rules from other modules in home package + -- but not things from other packages + + ModGuts) -- Modified fields are + -- (a) Bindings have rules attached, + -- (b) Rules are now just orphan rules + +prepareRules hsc_env@(HscEnv { hsc_dflags = dflags, hsc_HPT = hpt }) + guts@(ModGuts { mg_binds = binds, mg_deps = deps, mg_rules = local_rules }) + us + = do { let -- Simplify the local rules; boringly, we need to make an in-scope set + -- from the local binders, to avoid warnings from Simplify.simplVar + local_ids = mkInScopeSet (mkVarSet (bindersOfBinds binds)) + env = setInScopeSet gentleSimplEnv local_ids + (better_rules,_) = initSmpl dflags us (mapSmpl (simplRule env) local_rules) + home_pkg_rules = hptRules hsc_env (dep_mods deps) + + -- Find the rules for locally-defined Ids; then we can attach them + -- to the binders in the top-level bindings + -- + -- Reason + -- - It makes the rules easier to look up + -- - It means that transformation rules and specialisations for + -- locally defined Ids are handled uniformly + -- - It keeps alive things that are referred to only from a rule + -- (the occurrence analyser knows about rules attached to Ids) + -- - It makes sure that, when we apply a rule, the free vars + -- of the RHS are more likely to be in scope + -- - The imported rules are carried in the in-scope set + -- which is extended on each iteration by the new wave of + -- local binders; any rules which aren't on the binding will + -- thereby get dropped + (rules_for_locals, rules_for_imps) = partition isLocalRule better_rules + local_rule_base = extendRuleBaseList emptyRuleBase rules_for_locals + binds_w_rules = updateBinders local_rule_base binds + + hpt_rule_base = mkRuleBase home_pkg_rules + imp_rule_base = extendRuleBaseList hpt_rule_base rules_for_imps + + ; dumpIfSet_dyn dflags Opt_D_dump_rules "Transformation rules" + (vcat [text "Local rules", pprRules better_rules, + text "", + text "Imported rules", pprRuleBase imp_rule_base]) + + ; return (imp_rule_base, guts { mg_binds = binds_w_rules, + mg_rules = rules_for_imps }) + } - return better_rules +updateBinders :: RuleBase -> [CoreBind] -> [CoreBind] +updateBinders local_rules binds + = map update_bndrs binds where - black_list_all v = not (isDataConWrapId v) - -- This stops all inlining except the - -- wrappers for data constructors - - sw_chkr any = SwBool False -- A bit bogus - - -- Boringly, we need to gather the in-scope set. - -- Typically this thunk won't even be force, but the test in - -- simpVar fails if it isn't right, and it might conceivably matter - bind_vars = foldr (unionVarSet . mkVarSet . bindersOf) emptyVarSet binds + update_bndrs (NonRec b r) = NonRec (update_bndr b) r + update_bndrs (Rec prs) = Rec [(update_bndr b, r) | (b,r) <- prs] + + update_bndr bndr = case lookupNameEnv local_rules (idName bndr) of + Nothing -> bndr + Just rules -> bndr `addIdSpecialisations` rules + -- The binder might have some existing rules, + -- arising from specialisation pragmas +\end{code} -simplRule rule@(ProtoCoreRule is_local id (Rule name bndrs args rhs)) - | not is_local - = returnSmpl rule -- No need to fiddle with imported rules - | otherwise - = simplBinders bndrs $ \ bndrs' -> - mapSmpl simpl_arg args `thenSmpl` \ args' -> - simplExpr rhs `thenSmpl` \ rhs' -> - returnSmpl (ProtoCoreRule is_local id (Rule name bndrs' args' rhs')) +We must do some gentle simplification on the template (but not the RHS) +of each rule. The case that forced me to add this was the fold/build rule, +which without simplification looked like: + fold k z (build (/\a. g a)) ==> ... +This doesn't match unless you do eta reduction on the build argument. -simpl_arg e --- I've seen rules in which a LHS like +\begin{code} +simplRule env rule@(BuiltinRule {}) + = returnSmpl rule +simplRule env rule@(Rule { ru_bndrs = bndrs, ru_args = args, ru_rhs = rhs }) + = simplBinders env bndrs `thenSmpl` \ (env, bndrs') -> + mapSmpl (simplExprGently env) args `thenSmpl` \ args' -> + simplExprGently env rhs `thenSmpl` \ rhs' -> + returnSmpl (rule { ru_bndrs = bndrs', ru_args = args', ru_rhs = rhs' }) + +-- It's important that simplExprGently does eta reduction. +-- For example, in a rule like: -- augment g (build h) --- turns into +-- we do not want to get -- augment (\a. g a) (build h) --- So it's a help to eta-reduce the args as we simplify them. --- Otherwise we don't match when given an argument like +-- otherwise we don't match when given an argument like -- (\a. h a a) - = simplExpr e `thenSmpl` \ e' -> - returnSmpl (etaReduceExpr e') +-- +-- The simplifier does indeed do eta reduction (it's in +-- Simplify.completeLam) but only if -O is on. +\end{code} + +\begin{code} +simplExprGently :: SimplEnv -> CoreExpr -> SimplM CoreExpr +-- Simplifies an expression +-- does occurrence analysis, then simplification +-- and repeats (twice currently) because one pass +-- alone leaves tons of crud. +-- Used (a) for user expressions typed in at the interactive prompt +-- (b) the LHS and RHS of a RULE +-- +-- The name 'Gently' suggests that the SimplifierMode is SimplGently, +-- and in fact that is so.... but the 'Gently' in simplExprGently doesn't +-- enforce that; it just simplifies the expression twice + +simplExprGently env expr + = simplExpr env (occurAnalyseExpr expr) `thenSmpl` \ expr1 -> + simplExpr env (occurAnalyseExpr expr1) +\end{code} + + +%************************************************************************ +%* * +\subsection{Glomming} +%* * +%************************************************************************ + +\begin{code} +glomBinds :: DynFlags -> [CoreBind] -> IO [CoreBind] +-- Glom all binds together in one Rec, in case any +-- transformations have introduced any new dependencies +-- +-- NB: the global invariant is this: +-- *** the top level bindings are never cloned, and are always unique *** +-- +-- We sort them into dependency order, but applying transformation rules may +-- make something at the top refer to something at the bottom: +-- f = \x -> p (q x) +-- h = \y -> 3 +-- +-- RULE: p (q x) = h x +-- +-- Applying this rule makes f refer to h, +-- although it doesn't appear to in the source program. +-- This pass lets us control where it happens. +-- +-- NOTICE that this cannot happen for rules whose head is a locally-defined +-- function. It only happens for rules whose head is an imported function +-- (p in the example above). So, for example, the rule had been +-- RULE: f (p x) = h x +-- then the rule for f would be attached to f itself (in its IdInfo) +-- by prepareLocalRuleBase and h would be regarded by the occurrency +-- analyser as free in f. + +glomBinds dflags binds + = do { showPass dflags "GlomBinds" ; + let { recd_binds = [Rec (flattenBinds binds)] } ; + return recd_binds } + -- Not much point in printing the result... + -- just consumes output bandwidth \end{code} + %************************************************************************ %* * \subsection{The driver for the simplifier} @@ -209,113 +367,308 @@ simpl_arg e %************************************************************************ \begin{code} -simplifyPgm :: RuleBase - -> (SimplifierSwitch -> SwitchResult) +simplifyPgm :: SimplifierMode + -> [SimplifierSwitch] + -> HscEnv -> UniqSupply - -> [CoreBind] -- Input - -> IO (SimplCount, [CoreBind]) -- New bindings + -> RuleBase + -> ModGuts + -> IO (SimplCount, ModGuts) -- New bindings -simplifyPgm (imported_rule_ids, rule_lhs_fvs) - sw_chkr us binds +simplifyPgm mode switches hsc_env us imp_rule_base guts = do { - beginPass "Simplify"; - - -- Glom all binds together in one Rec, in case any - -- transformations have introduced any new dependencies - -- - -- NB: the global invariant is this: - -- *** the top level bindings are never cloned, and are always unique *** - -- - -- We sort them into dependency order, but applying transformation rules may - -- make something at the top refer to something at the bottom: - -- f = \x -> p (q x) - -- h = \y -> 3 - -- - -- RULE: p (q x) = h x - -- - -- Applying this rule makes f refer to h, although it doesn't appear to in the - -- source program. Our solution is to do this occasional glom-together step, - -- just once per overall simplfication step. - - let { recd_binds = [Rec (flattenBinds binds)] }; - - (termination_msg, it_count, counts_out, binds') <- iteration us 1 zeroSimplCount recd_binds; - - dumpIfSet (opt_D_verbose_core2core && opt_D_dump_simpl_stats) + showPass dflags "Simplify"; + + (termination_msg, it_count, counts_out, binds') + <- do_iteration us 1 (zeroSimplCount dflags) (mg_binds guts) ; + + dumpIfSet (dopt Opt_D_verbose_core2core dflags + && dopt Opt_D_dump_simpl_stats dflags) "Simplifier statistics" (vcat [text termination_msg <+> text "after" <+> ppr it_count <+> text "iterations", text "", pprSimplCount counts_out]); - endPass "Simplify" - (opt_D_verbose_core2core && not opt_D_dump_simpl_iterations) - binds' ; + endPass dflags "Simplify" Opt_D_verbose_core2core binds'; - return (counts_out, binds') + return (counts_out, guts { mg_binds = binds' }) } where - max_iterations = getSimplIntSwitch sw_chkr MaxSimplifierIterations - black_list_fn = blackListed rule_lhs_fvs (intSwitchSet sw_chkr SimplInlinePhase) - - core_iter_dump binds | opt_D_verbose_core2core = pprCoreBindings binds - | otherwise = empty - - iteration us iteration_no counts binds + dflags = hsc_dflags hsc_env + phase_info = case mode of + SimplGently -> "gentle" + SimplPhase n -> show n + + sw_chkr = isAmongSimpl switches + max_iterations = intSwitchSet sw_chkr MaxSimplifierIterations `orElse` 2 + + do_iteration us iteration_no counts binds + -- iteration_no is the number of the iteration we are + -- about to begin, with '1' for the first + | iteration_no > max_iterations -- Stop if we've run out of iterations + = do { +#ifdef DEBUG + if max_iterations > 2 then + hPutStr stderr ("NOTE: Simplifier still going after " ++ + show max_iterations ++ + " iterations; bailing out.\n") + else + return (); +#endif + -- Subtract 1 from iteration_no to get the + -- number of iterations we actually completed + return ("Simplifier baled out", iteration_no - 1, counts, binds) + } + + -- Try and force thunks off the binds; significantly reduces + -- space usage, especially with -O. JRS, 000620. + | let sz = coreBindsSize binds in sz == sz = do { -- Occurrence analysis - let { tagged_binds = _scc_ "OccAnal" occurAnalyseBinds binds } ; - - dumpIfSet opt_D_dump_occur_anal "Occurrence analysis" + let { tagged_binds = _scc_ "OccAnal" occurAnalysePgm binds } ; + dumpIfSet_dyn dflags Opt_D_dump_occur_anal "Occurrence analysis" (pprCoreBindings tagged_binds); - -- Simplify - let { (binds', counts') = initSmpl sw_chkr us1 imported_rule_ids - black_list_fn - (simplTopBinds tagged_binds); - -- The imported_rule_ids are used by initSmpl to initialise - -- the in-scope set. That way, the simplifier will change any - -- occurrences of the imported id to the one in the imported_rule_ids - -- set, which are decorated with their rules. - - all_counts = counts `plusSimplCount` counts' - } ; + -- Get any new rules, and extend the rule base + -- We need to do this regularly, because simplification can + -- poke on IdInfo thunks, which in turn brings in new rules + -- behind the scenes. Otherwise there's a danger we'll simply + -- miss the rules for Ids hidden inside imported inlinings + eps <- hscEPS hsc_env ; + let { rule_base' = unionRuleBase imp_rule_base (eps_rule_base eps) + ; simpl_env = mkSimplEnv mode sw_chkr rule_base' } ; + + -- Simplify the program + -- We do this with a *case* not a *let* because lazy pattern + -- matching bit us with bad space leak! + -- With a let, we ended up with + -- let + -- t = initSmpl ... + -- counts' = snd t + -- in + -- case t of {(_,counts') -> if counts'=0 then ... } + -- So the conditional didn't force counts', because the + -- selection got duplicated. Sigh! + case initSmpl dflags us1 (_scc_ "SimplTopBinds" simplTopBinds simpl_env tagged_binds) of { + (binds', counts') -> do { + + let { all_counts = counts `plusSimplCount` counts' + ; herald = "Simplifier phase " ++ phase_info ++ + ", iteration " ++ show iteration_no ++ + " out of " ++ show max_iterations + } ; -- Stop if nothing happened; don't dump output if isZeroSimplCount counts' then - return ("Simplifier reached fixed point", iteration_no, all_counts, binds') + return ("Simplifier reached fixed point", iteration_no, + all_counts, binds') else do { + -- Short out indirections + -- We do this *after* at least one run of the simplifier + -- because indirection-shorting uses the export flag on *occurrences* + -- and that isn't guaranteed to be ok until after the first run propagates + -- stuff from the binding site to its occurrences + let { binds'' = _scc_ "ZapInd" shortOutIndirections binds' } ; -- Dump the result of this iteration - dumpIfSet opt_D_dump_simpl_iterations - ("Simplifier iteration " ++ show iteration_no - ++ " out of " ++ show max_iterations) - (pprSimplCount counts') ; - - if opt_D_dump_simpl_iterations then - endPass ("Simplifier iteration " ++ show iteration_no ++ " result") - opt_D_verbose_core2core - binds' - else - return [] ; - - -- Stop if we've run out of iterations - if iteration_no == max_iterations then - do { -#ifdef DEBUG - if max_iterations > 2 then - hPutStr stderr ("NOTE: Simplifier still going after " ++ - show max_iterations ++ - " iterations; bailing out.\n") - else -#endif - return (); - - return ("Simplifier baled out", iteration_no, all_counts, binds') - } + dumpIfSet_dyn dflags Opt_D_dump_simpl_iterations herald + (pprSimplCount counts') ; + endPass dflags herald Opt_D_dump_simpl_iterations binds'' ; - -- Else loop - else iteration us2 (iteration_no + 1) all_counts binds' - } } + -- Loop + do_iteration us2 (iteration_no + 1) all_counts binds'' + } } } } where (us1, us2) = splitUniqSupply us \end{code} + + +%************************************************************************ +%* * + Shorting out indirections +%* * +%************************************************************************ + +If we have this: + + x_local = + ...bindings... + x_exported = x_local + +where x_exported is exported, and x_local is not, then we replace it with this: + + x_exported = + x_local = x_exported + ...bindings... + +Without this we never get rid of the x_exported = x_local thing. This +save a gratuitous jump (from \tr{x_exported} to \tr{x_local}), and +makes strictness information propagate better. This used to happen in +the final phase, but it's tidier to do it here. + +STRICTNESS: if we have done strictness analysis, we want the strictness info on +x_local to transfer to x_exported. Hence the copyIdInfo call. + +RULES: we want to *add* any RULES for x_local to x_exported. + +Note [Rules and indirection-zapping] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Problem: what if x_exported has a RULE that mentions something in ...bindings...? +Then the things mentioned can be out of scope! Solution + a) Make sure that in this pass the usage-info from x_exported is + available for ...bindings... + b) If there are any such RULES, rec-ify the entire top-level. + It'll get sorted out next time round + +Messing up the rules +~~~~~~~~~~~~~~~~~~~~ +The example that went bad on me at one stage was this one: + + iterate :: (a -> a) -> a -> [a] + [Exported] + iterate = iterateList + + iterateFB c f x = x `c` iterateFB c f (f x) + iterateList f x = x : iterateList f (f x) + [Not exported] + + {-# RULES + "iterate" forall f x. iterate f x = build (\c _n -> iterateFB c f x) + "iterateFB" iterateFB (:) = iterateList + #-} + +This got shorted out to: + + iterateList :: (a -> a) -> a -> [a] + iterateList = iterate + + iterateFB c f x = x `c` iterateFB c f (f x) + iterate f x = x : iterate f (f x) + + {-# RULES + "iterate" forall f x. iterate f x = build (\c _n -> iterateFB c f x) + "iterateFB" iterateFB (:) = iterate + #-} + +And now we get an infinite loop in the rule system + iterate f x -> build (\cn -> iterateFB c f x) + -> iterateFB (:) f x + -> iterate f x + +Tiresome old solution: + don't do shorting out if f has rewrite rules (see shortableIdInfo) + +New solution (I think): + use rule switching-off pragmas to get rid + of iterateList in the first place + + +Other remarks +~~~~~~~~~~~~~ +If more than one exported thing is equal to a local thing (i.e., the +local thing really is shared), then we do one only: +\begin{verbatim} + x_local = .... + x_exported1 = x_local + x_exported2 = x_local +==> + x_exported1 = .... + + x_exported2 = x_exported1 +\end{verbatim} + +We rely on prior eta reduction to simplify things like +\begin{verbatim} + x_exported = /\ tyvars -> x_local tyvars +==> + x_exported = x_local +\end{verbatim} +Hence,there's a possibility of leaving unchanged something like this: +\begin{verbatim} + x_local = .... + x_exported1 = x_local Int +\end{verbatim} +By the time we've thrown away the types in STG land this +could be eliminated. But I don't think it's very common +and it's dangerous to do this fiddling in STG land +because we might elminate a binding that's mentioned in the +unfolding for something. + +\begin{code} +type IndEnv = IdEnv Id -- Maps local_id -> exported_id + +shortOutIndirections :: [CoreBind] -> [CoreBind] +shortOutIndirections binds + | isEmptyVarEnv ind_env = binds + | no_need_to_flatten = binds' + | otherwise = [Rec (flattenBinds binds')] -- See Note [Rules and indirect-zapping] + where + ind_env = makeIndEnv binds + exp_ids = varSetElems ind_env -- These exported Ids are the subjects + exp_id_set = mkVarSet exp_ids -- of the indirection-elimination + no_need_to_flatten = all (null . specInfoRules . idSpecialisation) exp_ids + binds' = concatMap zap binds + + zap (NonRec bndr rhs) = [NonRec b r | (b,r) <- zapPair (bndr,rhs)] + zap (Rec pairs) = [Rec (concatMap zapPair pairs)] + + zapPair (bndr, rhs) + | bndr `elemVarSet` exp_id_set = [] + | Just exp_id <- lookupVarEnv ind_env bndr = [(transferIdInfo exp_id bndr, rhs), + (bndr, Var exp_id)] + | otherwise = [(bndr,rhs)] + +makeIndEnv :: [CoreBind] -> IndEnv +makeIndEnv binds + = foldr add_bind emptyVarEnv binds + where + add_bind :: CoreBind -> IndEnv -> IndEnv + add_bind (NonRec exported_id rhs) env = add_pair (exported_id, rhs) env + add_bind (Rec pairs) env = foldr add_pair env pairs + + add_pair :: (Id,CoreExpr) -> IndEnv -> IndEnv + add_pair (exported_id, Var local_id) env + | shortMeOut env exported_id local_id = extendVarEnv env local_id exported_id + add_pair (exported_id, rhs) env + = env + +shortMeOut ind_env exported_id local_id +-- The if-then-else stuff is just so I can get a pprTrace to see +-- how often I don't get shorting out becuase of IdInfo stuff + = if isExportedId exported_id && -- Only if this is exported + + isLocalId local_id && -- Only if this one is defined in this + -- module, so that we *can* change its + -- binding to be the exported thing! + + not (isExportedId local_id) && -- Only if this one is not itself exported, + -- since the transformation will nuke it + + not (local_id `elemVarEnv` ind_env) -- Only if not already substituted for + then + True + +{- No longer needed + if isEmptySpecInfo (specInfo (idInfo exported_id)) -- Only if no rules + then True -- See note on "Messing up rules" + else +#ifdef DEBUG + pprTrace "shortMeOut:" (ppr exported_id) +#endif + False +-} + else + False + + +----------------- +transferIdInfo :: Id -> Id -> Id +transferIdInfo exported_id local_id + = modifyIdInfo transfer exported_id + where + local_info = idInfo local_id + transfer exp_info = exp_info `setNewStrictnessInfo` newStrictnessInfo local_info + `setWorkerInfo` workerInfo local_info + `setSpecInfo` addSpecInfo (specInfo exp_info) + (specInfo local_info) +\end{code}