X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FsimplCore%2FSimplCore.lhs;h=8b2118a443439b3e467f52118c23429fe897d813;hb=36d22a1cb608e8572776ab6d402fd0c1a9287dc5;hp=af78fb7f4fa838a1b9c66b062cb6ed15956cac04;hpb=98688c6e8fd33f31c51218cf93cbf03fe3a5e73d;p=ghc-hetmet.git diff --git a/ghc/compiler/simplCore/SimplCore.lhs b/ghc/compiler/simplCore/SimplCore.lhs index af78fb7..8b2118a 100644 --- a/ghc/compiler/simplCore/SimplCore.lhs +++ b/ghc/compiler/simplCore/SimplCore.lhs @@ -13,31 +13,32 @@ import CmdLineOpts ( CoreToDo(..), SimplifierSwitch(..), dopt_CoreToDo, buildCoreToDo ) import CoreSyn -import CoreFVs ( ruleRhsFreeVars ) -import HscTypes ( HscEnv(..), GhciMode(..), - ModGuts(..), ModGuts, Avails, availsToNameSet, - ModDetails(..), - HomeModInfo(..), ExternalPackageState(..), hscEPS - ) +import TcIface ( loadImportedRules ) +import HscTypes ( HscEnv(..), ModGuts(..), ExternalPackageState(..), + Dependencies( dep_mods ), + hscEPS, hptRules ) import CSE ( cseProgram ) -import Rules ( RuleBase, emptyRuleBase, ruleBaseIds, - extendRuleBaseList, pprRuleBase, - ruleCheckProgram ) -import Module ( moduleEnvElts ) -import Name ( Name, isExternalName ) -import NameSet ( elemNameSet ) -import PprCore ( pprCoreBindings, pprCoreExpr ) -import OccurAnal ( occurAnalyseBinds, occurAnalyseGlobalExpr ) +import Rules ( RuleBase, ruleBaseIds, emptyRuleBase, + extendRuleBaseList, pprRuleBase, ruleCheckProgram ) +import PprCore ( pprCoreBindings, pprCoreExpr, pprIdRules ) +import OccurAnal ( occurAnalysePgm, occurAnalyseGlobalExpr ) +import IdInfo ( setNewStrictnessInfo, newStrictnessInfo, + setWorkerInfo, workerInfo, + setSpecInfo, specInfo ) import CoreUtils ( coreBindsSize ) import Simplify ( simplTopBinds, simplExpr ) -import SimplUtils ( simplBinders ) +import SimplEnv ( SimplEnv, simplBinders, mkSimplEnv, setInScopeSet ) import SimplMonad import ErrUtils ( dumpIfSet, dumpIfSet_dyn, showPass ) import CoreLint ( endPass ) +import VarEnv ( mkInScopeSet ) import FloatIn ( floatInwards ) import FloatOut ( floatOutwards ) -import Id ( idName, setIdLocalExported ) +import Id ( Id, modifyIdInfo, idInfo, idIsFrom, isExportedId, isLocalId, + idSpecialisation, setIdSpecialisation ) +import Rules ( addRules ) import VarSet +import VarEnv import LiberateCase ( liberateCase ) import SAT ( doStaticArgs ) import Specialise ( specProgram) @@ -52,9 +53,8 @@ import CprAnalyse ( cprAnalyse ) import UniqSupply ( UniqSupply, mkSplitUniqSupply, splitUniqSupply ) import IO ( hPutStr, stderr ) import Outputable - +import List ( partition ) import Maybes ( orElse ) -import List ( partition ) \end{code} %************************************************************************ @@ -68,40 +68,29 @@ core2core :: HscEnv -> ModGuts -> IO ModGuts -core2core hsc_env - mod_impl@(ModGuts { mg_exports = exports, - mg_binds = binds_in, - mg_rules = rules_in }) +core2core hsc_env guts = do - let dflags = hsc_dflags hsc_env - ghci_mode = hsc_mode hsc_env + let dflags = hsc_dflags hsc_env core_todos | Just todo <- dopt_CoreToDo dflags = todo | otherwise = buildCoreToDo dflags - us <- mkSplitUniqSupply 's' + us <- mkSplitUniqSupply 's' let (cp_us, ru_us) = splitUniqSupply us -- COMPUTE THE RULE BASE TO USE - (rule_base, local_rule_ids, orphan_rules) - <- prepareRules hsc_env ru_us binds_in rules_in - - -- PREPARE THE BINDINGS - let binds1 = updateBinders ghci_mode local_rule_ids - orphan_rules exports binds_in + (imp_rule_base, guts') <- prepareRules hsc_env guts ru_us -- DO THE BUSINESS - (stats, processed_binds) - <- doCorePasses dflags rule_base (zeroSimplCount dflags) cp_us binds1 core_todos + (stats, guts'') <- doCorePasses hsc_env cp_us + (zeroSimplCount dflags) + imp_rule_base guts' core_todos dumpIfSet_dyn dflags Opt_D_dump_simpl_stats "Grand total simplifier statistics" (pprSimplCount stats) - -- Return results - -- We only return local orphan rules, i.e., local rules not attached to an Id - -- The bindings cotain more rules, embedded in the Ids - return (mod_impl { mg_binds = processed_binds, mg_rules = orphan_rules}) + return guts'' simplifyExpr :: DynFlags -- includes spec of what core-to-core passes to do @@ -115,8 +104,8 @@ simplifyExpr dflags expr ; us <- mkSplitUniqSupply 's' - ; let env = emptySimplEnv SimplGently [] emptyVarSet - (expr', _counts) = initSmpl dflags us (simplExprGently env expr) + ; let (expr', _counts) = initSmpl dflags us $ + simplExprGently gentleSimplEnv expr ; dumpIfSet_dyn dflags Opt_D_dump_simpl "Simplified expression" (pprCoreExpr expr') @@ -124,77 +113,86 @@ simplifyExpr dflags expr ; return expr' } +gentleSimplEnv :: SimplEnv +gentleSimplEnv = mkSimplEnv SimplGently + (isAmongSimpl []) + emptyRuleBase -doCorePasses :: DynFlags - -> RuleBase -- the main rule base - -> SimplCount -- simplifier stats +doCorePasses :: HscEnv -> UniqSupply -- uniques - -> [CoreBind] -- local binds in (with rules attached) + -> SimplCount -- simplifier stats + -> RuleBase -- the main rule base + -> ModGuts -- local binds in (with rules attached) -> [CoreToDo] -- which passes to do - -> IO (SimplCount, [CoreBind]) -- stats, binds, local orphan rules + -> IO (SimplCount, ModGuts) -doCorePasses dflags rb stats us binds [] - = return (stats, binds) +doCorePasses hsc_env us stats rb guts [] + = return (stats, guts) -doCorePasses dflags rb stats us binds (to_do : to_dos) +doCorePasses hsc_env us stats rb guts (to_do : to_dos) = do let (us1, us2) = splitUniqSupply us - - (stats1, binds1) <- doCorePass dflags rb us1 binds to_do - - doCorePasses dflags rb (stats `plusSimplCount` stats1) us2 binds1 to_dos - -doCorePass dfs rb us binds (CoreDoSimplify mode switches) - = _scc_ "Simplify" simplifyPgm dfs rb mode switches us binds -doCorePass dfs rb us binds CoreCSE - = _scc_ "CommonSubExpr" noStats dfs (cseProgram dfs binds) -doCorePass dfs rb us binds CoreLiberateCase - = _scc_ "LiberateCase" noStats dfs (liberateCase dfs binds) -doCorePass dfs rb us binds CoreDoFloatInwards - = _scc_ "FloatInwards" noStats dfs (floatInwards dfs binds) -doCorePass dfs rb us binds (CoreDoFloatOutwards f) - = _scc_ "FloatOutwards" noStats dfs (floatOutwards dfs f us binds) -doCorePass dfs rb us binds CoreDoStaticArgs - = _scc_ "StaticArgs" noStats dfs (doStaticArgs us binds) -doCorePass dfs rb us binds CoreDoStrictness - = _scc_ "Stranal" noStats dfs (dmdAnalPgm dfs binds) -doCorePass dfs rb us binds CoreDoWorkerWrapper - = _scc_ "WorkWrap" noStats dfs (wwTopBinds dfs us binds) -doCorePass dfs rb us binds CoreDoSpecialising - = _scc_ "Specialise" noStats dfs (specProgram dfs us binds) -doCorePass dfs rb us binds CoreDoSpecConstr - = _scc_ "SpecConstr" noStats dfs (specConstrProgram dfs us binds) -#ifdef OLD_STRICTNESS -doCorePass dfs rb us binds CoreDoOldStrictness - = _scc_ "OldStrictness" noStats dfs (doOldStrictness dfs binds) + (stats1, rb1, guts1) <- doCorePass to_do hsc_env us1 rb guts + doCorePasses hsc_env us2 (stats `plusSimplCount` stats1) rb1 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 -doCorePass dfs rb us binds CoreDoPrintCore - = _scc_ "PrintCore" noStats dfs (printCore binds) -doCorePass dfs rb us binds CoreDoGlomBinds - = noStats dfs (glomBinds dfs binds) -doCorePass dfs rb us binds (CoreDoRuleCheck phase pat) - = noStats dfs (ruleCheck dfs phase pat binds) -doCorePass dfs rb us binds CoreDoNothing - = noStats dfs (return binds) #ifdef OLD_STRICTNESS -doOldStrictness dfs binds +doOldStrictness dfs binds = do binds1 <- saBinds dfs binds binds2 <- cprAnalyse dfs binds1 return binds2 #endif -printCore binds = do dumpIfSet True "Print Core" - (pprCoreBindings binds) - return binds +printCore _ binds = dumpIfSet True "Print Core" (pprCoreBindings binds) -ruleCheck dflags phase pat binds = do showPass dflags "RuleCheck" +ruleCheck phase pat dflags binds = do showPass dflags "RuleCheck" printDump (ruleCheckProgram phase pat binds) - return binds - --- most passes return no stats and don't change rules -noStats dfs thing = do { binds <- thing; return (zeroSimplCount dfs, binds) } +-- Most passes return no stats and don't change rules +trBinds :: (DynFlags -> [CoreBind] -> IO [CoreBind]) + -> HscEnv -> UniqSupply -> RuleBase -> ModGuts + -> IO (SimplCount, RuleBase, ModGuts) +trBinds do_pass hsc_env us rb guts + = do { binds' <- do_pass dflags (mg_binds guts) + ; return (zeroSimplCount dflags, rb, guts { mg_binds = binds' }) } + where + dflags = hsc_dflags hsc_env + +trBindsU :: (DynFlags -> UniqSupply -> [CoreBind] -> IO [CoreBind]) + -> HscEnv -> UniqSupply -> RuleBase -> ModGuts + -> IO (SimplCount, RuleBase, ModGuts) +trBindsU do_pass hsc_env us rb guts + = do { binds' <- do_pass dflags us (mg_binds guts) + ; return (zeroSimplCount dflags, rb, 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, RuleBase, ModGuts) +observe do_pass hsc_env us rb guts + = do { binds <- do_pass dflags (mg_binds guts) + ; return (zeroSimplCount dflags, rb, guts) } + where + dflags = hsc_dflags hsc_env \end{code} @@ -207,123 +205,94 @@ noStats dfs thing = do { binds <- thing; return (zeroSimplCount dfs, binds) } -- 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. It also returns --- Ids mentioned on LHS of some rule; these should be blacklisted. - --- The rule Ids and LHS Ids are black-listed; that is, they aren't inlined --- so that the opportunity to apply the rule isn't lost too soon +-- returns the remainder attached to Ids in an IdSet. \begin{code} prepareRules :: HscEnv + -> ModGuts -> UniqSupply - -> [CoreBind] - -> [IdCoreRule] -- Local rules - -> IO (RuleBase, -- Full rule base - IdSet, -- Local rule Ids - [IdCoreRule]) -- Orphan rules defined in this module + -> IO (RuleBase, -- Rule base for imported things, incl + -- (a) rules defined in this module (orphans) + -- (b) rules from other packages + -- (c) rules from other modules in home package + 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 }) - us binds local_rules + guts@(ModGuts { mg_binds = binds, mg_deps = deps, mg_rules = local_rules }) + us = do { eps <- hscEPS hsc_env - ; let env = emptySimplEnv SimplGently [] local_ids + ; 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) - ; let (local_rules, orphan_rules) = partition ((`elemVarSet` local_ids) . fst) better_rules - -- We use (`elemVarSet` local_ids) rather than isLocalId because - -- isLocalId isn't true of class methods. + (orphan_rules, rules_for_locals) = partition isOrphanRule better_rules + -- Get the rules for locally-defined Ids out of the RuleBase -- If we miss any rules for Ids defined here, then we end up - -- giving the local decl a new Unique (because the in-scope-set is the - -- same as the rule-id set), and now the binding for the class method + -- giving the local decl a new Unique (because the in-scope-set is (hackily) the + -- same as the non-local-rule-id set, so the Id looks as if it's in scope + -- and hence should be cloned), and now the binding for the class method -- doesn't have the same Unique as the one in the Class and the tc-env -- Example: class Foo a where -- op :: a -> a -- {-# RULES "op" op x = x #-} - local_rule_base = extendRuleBaseList emptyRuleBase local_rules - local_rule_ids = ruleBaseIds local_rule_base -- Local Ids with rules attached - imp_rule_base = foldl add_rules (eps_rule_base eps) (moduleEnvElts hpt) - final_rule_base = extendRuleBaseList imp_rule_base orphan_rules + -- NB: we assume that the imported rules dont include + -- rules for Ids in this module; if there is, the above bad things may happen + + pkg_rule_base = eps_rule_base eps + hpt_rule_base = extendRuleBaseList pkg_rule_base home_pkg_rules + imp_rule_base = extendRuleBaseList hpt_rule_base orphan_rules + + -- Update the binders in the local bindings with the lcoal rules + -- Update the binders of top-level bindings by + -- attaching the rules for each locally-defined Id to that Id. + -- + -- 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 + local_rule_base = extendRuleBaseList emptyRuleBase rules_for_locals + binds_w_rules = updateBinders local_rule_base binds ; dumpIfSet_dyn dflags Opt_D_dump_rules "Transformation rules" - (vcat [text "Local rules", pprRuleBase local_rule_base, + (vcat [text "Local rules", pprIdRules better_rules, text "", - text "Imported rules", pprRuleBase final_rule_base]) + text "Imported rules", pprRuleBase imp_rule_base]) - ; return (final_rule_base, local_rule_ids, orphan_rules) +#ifdef DEBUG + ; let bad_rules = filter (idIsFrom (mg_module guts)) + (varSetElems (ruleBaseIds imp_rule_base)) + ; WARN( not (null bad_rules), ppr bad_rules ) return () +#endif + ; return (imp_rule_base, guts { mg_binds = binds_w_rules, mg_rules = orphan_rules }) } - where - add_rules rule_base mod_info = extendRuleBaseList rule_base (md_rules (hm_details mod_info)) - - -- Boringly, we need to gather the in-scope set. - local_ids = foldr (unionVarSet . mkVarSet . bindersOf) emptyVarSet binds - -updateBinders :: GhciMode - -> IdSet -- Locally defined ids with their Rules attached - -> [IdCoreRule] -- Orphan rules - -> Avails -- What is exported - -> [CoreBind] -> [CoreBind] - -- A horrible function - --- Update the binders of top-level bindings as follows --- a) Attach the rules for each locally-defined Id to that Id. --- b) Set the no-discard flag if either the Id is exported, --- or it's mentioned in the RHS of a rule --- --- You might wonder why exported Ids aren't already marked as such; --- it's just because the type checker is rather busy already and --- I didn't want to pass in yet another mapping. --- --- Reason for (a) --- - 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 --- --- Reason for (b) --- It means that the binding won't be discarded EVEN if the binding --- ends up being trivial (v = w) -- the simplifier would usually just --- substitute w for v throughout, but we don't apply the substitution to --- the rules (maybe we should?), so this substitution would make the rule --- bogus. - -updateBinders ghci_mode rule_ids orphan_rules exports binds +updateBinders :: RuleBase -> [CoreBind] -> [CoreBind] +updateBinders rule_base binds = map update_bndrs binds where + rule_ids = ruleBaseIds rule_base + 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 - | dont_discard bndr = setIdLocalExported bndr_with_rules - | otherwise = bndr_with_rules - where - bndr_with_rules = lookupVarSet rule_ids bndr `orElse` bndr - - orph_rhs_fvs = unionVarSets (map (ruleRhsFreeVars . snd) orphan_rules) - -- An orphan rule must keep alive the free vars - -- of its right-hand side. - -- Non-orphan rules are attached to the Id (bndr_with_rules above) - -- and that keeps the rhs free vars alive - - dont_discard bndr = is_exported (idName bndr) - || bndr `elemVarSet` orph_rhs_fvs - - -- In interactive mode, we don't want to discard any top-level - -- entities at all (eg. do not inline them away during - -- simplification), and retain them all in the TypeEnv so they are - -- available from the command line. - -- - -- isExternalName separates the user-defined top-level names from those - -- introduced by the type checker. - is_exported :: Name -> Bool - is_exported | ghci_mode == Interactive = isExternalName - | otherwise = (`elemNameSet` export_fvs) - - export_fvs = availsToNameSet exports + update_bndr bndr = case lookupVarSet rule_ids bndr of + Nothing -> bndr + Just id -> bndr `setIdSpecialisation` idSpecialisation id \end{code} @@ -334,13 +303,13 @@ which without simplification looked like: This doesn't match unless you do eta reduction on the build argument. \begin{code} -simplRule env rule@(id, BuiltinRule _ _) +simplRule env rule@(IdCoreRule id _ (BuiltinRule _ _)) = returnSmpl rule -simplRule env rule@(id, Rule act name bndrs args rhs) +simplRule env (IdCoreRule id is_orph (Rule act name bndrs args rhs)) = simplBinders env bndrs `thenSmpl` \ (env, bndrs') -> mapSmpl (simplExprGently env) args `thenSmpl` \ args' -> simplExprGently env rhs `thenSmpl` \ rhs' -> - returnSmpl (id, Rule act name bndrs' args' rhs') + returnSmpl (IdCoreRule id is_orph (Rule act name bndrs' args' rhs')) -- It's important that simplExprGently does eta reduction. -- For example, in a rule like: @@ -422,21 +391,20 @@ glomBinds dflags binds %************************************************************************ \begin{code} -simplifyPgm :: DynFlags - -> RuleBase - -> SimplifierMode +simplifyPgm :: SimplifierMode -> [SimplifierSwitch] + -> HscEnv -> UniqSupply - -> [CoreBind] -- Input - -> IO (SimplCount, [CoreBind]) -- New bindings + -> RuleBase + -> ModGuts + -> IO (SimplCount, RuleBase, ModGuts) -- New bindings -simplifyPgm dflags rule_base - mode switches us binds +simplifyPgm mode switches hsc_env us rule_base guts = do { showPass dflags "Simplify"; - (termination_msg, it_count, counts_out, binds') - <- iteration us 1 (zeroSimplCount dflags) binds; + (termination_msg, it_count, counts_out, rule_base', guts') + <- do_iteration us rule_base 1 (zeroSimplCount dflags) guts; dumpIfSet (dopt Opt_D_verbose_core2core dflags && dopt Opt_D_dump_simpl_stats dflags) @@ -445,21 +413,20 @@ simplifyPgm dflags rule_base text "", pprSimplCount counts_out]); - endPass dflags "Simplify" Opt_D_verbose_core2core binds'; + endPass dflags "Simplify" Opt_D_verbose_core2core (mg_binds guts'); - return (counts_out, binds') + return (counts_out, rule_base', guts') } where + dflags = hsc_dflags hsc_env phase_info = case mode of SimplGently -> "gentle" SimplPhase n -> show n - imported_rule_ids = ruleBaseIds rule_base - simpl_env = emptySimplEnv mode switches imported_rule_ids - sw_chkr = getSwitchChecker simpl_env + sw_chkr = isAmongSimpl switches max_iterations = intSwitchSet sw_chkr MaxSimplifierIterations `orElse` 2 - iteration us iteration_no counts binds + do_iteration us rule_base iteration_no counts guts -- 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 @@ -474,20 +441,40 @@ simplifyPgm dflags rule_base #endif -- Subtract 1 from iteration_no to get the -- number of iterations we actually completed - return ("Simplifier baled out", iteration_no - 1, counts, binds) + return ("Simplifier baled out", iteration_no - 1, counts, rule_base, guts) } -- Try and force thunks off the binds; significantly reduces -- space usage, especially with -O. JRS, 000620. - | let sz = coreBindsSize binds in sz == sz + | let sz = coreBindsSize (mg_binds guts) in sz == sz = do { -- Occurrence analysis - let { tagged_binds = _scc_ "OccAnal" occurAnalyseBinds binds } ; + let { short_inds = _scc_ "ZapInd" shortOutIndirections (mg_binds guts) ; + tagged_binds = _scc_ "OccAnal" occurAnalysePgm short_inds } ; + + dumpIfSet_dyn dflags Opt_D_dump_occur_anal "Short indirections" + (pprCoreBindings short_inds); dumpIfSet_dyn dflags Opt_D_dump_occur_anal "Occurrence analysis" (pprCoreBindings tagged_binds); - -- SIMPLIFY + -- Get any new rules, and extend the rule base + -- (on the side this extends the package rule base in the + -- ExternalPackageTable, ready for the next complation + -- in --make mode) + -- 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 + new_rules <- loadImportedRules hsc_env guts ; + let { rule_base' = extendRuleBaseList rule_base new_rules + ; simpl_env = mkSimplEnv mode sw_chkr rule_base' } ; + -- The new rule base Ids are used 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. + + -- 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 @@ -498,22 +485,20 @@ simplifyPgm dflags rule_base -- 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 (simplTopBinds simpl_env tagged_binds) of { + case initSmpl dflags us1 (_scc_ "SimplTopBinds" simplTopBinds simpl_env tagged_binds) of { (binds', counts') -> do { - -- 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. - let { all_counts = counts `plusSimplCount` counts' ; - herald = "Simplifier phase " ++ phase_info ++ + let { guts' = guts { mg_binds = binds' } + ; 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, rule_base', guts') else do { -- Dump the result of this iteration @@ -523,8 +508,201 @@ simplifyPgm dflags rule_base endPass dflags herald Opt_D_dump_simpl_iterations binds' ; -- Loop - iteration us2 (iteration_no + 1) all_counts binds' + do_iteration us2 rule_base' (iteration_no + 1) all_counts guts' } } } } where (us1, us2) = splitUniqSupply us \end{code} + + +%************************************************************************ +%* * + Top-level occurrence analysis + [In here, not OccurAnal, because it uses + Rules.lhs, which depends on OccurAnal] +%* * +%************************************************************************ + +In @occAnalPgm@ we do indirection-shorting. That is, 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 + exp_id_set = mkVarSet exp_ids + no_need_to_flatten = all (null . rulesRules . 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 isEmptyCoreRules (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` addRules exported_id (specInfo exp_info) + (rulesRules (specInfo local_info)) +\end{code}