X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FsimplCore%2FSimplCore.lhs;h=f345c08325d42cc14ca176eda00eb36314fcd5e3;hb=19a86f31f2e5623d0f9ca25838fd6e2aa52456eb;hp=80d9bb3c48760cb8c7ad22ab1b35f09df340cad7;hpb=7a3bd641457666e10d0a47be9f22762e03defbf0;p=ghc-hetmet.git diff --git a/ghc/compiler/simplCore/SimplCore.lhs b/ghc/compiler/simplCore/SimplCore.lhs index 80d9bb3..f345c08 100644 --- a/ghc/compiler/simplCore/SimplCore.lhs +++ b/ghc/compiler/simplCore/SimplCore.lhs @@ -1,543 +1,602 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[SimplCore]{Driver for simplifying @Core@ programs} \begin{code} -#include "HsVersions.h" - module SimplCore ( core2core ) where -IMP_Ubiq(){-uitous-} -IMPORT_1_3(IO(hPutStr,stderr)) +#include "HsVersions.h" -import AnalFBWW ( analFBWW ) -import Bag ( isEmptyBag, foldBag ) -import BinderInfo ( BinderInfo{-instance Outputable-} ) -import CmdLineOpts ( CoreToDo(..), SimplifierSwitch(..), switchIsOn, - opt_D_show_passes, +import CmdLineOpts ( CoreToDo(..), SimplifierSwitch(..), + SwitchResult, switchIsOn, + opt_D_dump_occur_anal, + opt_D_dump_simpl_iterations, opt_D_simplifier_stats, + opt_D_dump_simpl, opt_D_verbose_core2core, - opt_DoCoreLinting, - opt_FoldrBuildOn, - opt_ReportWhyUnfoldingsDisallowed, - opt_ShowImportSpecs, - opt_LiberateCaseThreshold + opt_D_dump_occur_anal ) -import CoreLint ( lintCoreBindings ) +import CoreLint ( beginPass, endPass ) import CoreSyn -import CoreUtils ( coreExprType ) +import PprCore ( pprCoreBindings ) +import OccurAnal ( occurAnalyseBinds ) +import CoreUtils ( exprIsTrivial, coreExprType ) +import Simplify ( simplBind ) +import SimplUtils ( etaCoreExpr, findDefault ) +import SimplMonad import CoreUnfold -import Literal ( Literal(..), literalType, mkMachInt ) -import ErrUtils ( ghcExit ) -import FiniteMap ( FiniteMap ) +import Const ( Con(..), Literal(..), literalType, mkMachInt ) +import ErrUtils ( dumpIfSet ) import FloatIn ( floatInwards ) import FloatOut ( floatOutwards ) -import FoldrBuildWW ( mkFoldrBuildWW ) -import Id ( mkSysLocal, setIdVisibility, - nullIdEnv, addOneToIdEnv, delOneFromIdEnv, - lookupIdEnv, SYN_IE(IdEnv), - GenId{-instance Outputable-} +import Id ( Id, mkSysLocal, mkUserId, isBottomingId, + idType, setIdType, idName, idInfo, idDetails + ) +import IdInfo ( InlinePragInfo(..), specInfo, setSpecInfo, + inlinePragInfo, setInlinePragInfo, + setUnfoldingInfo ) -import Name ( isExported, isLocallyDefined ) -import TyCon ( TyCon ) +import VarEnv +import VarSet +import Name ( mkLocalName, tidyOccName, tidyTopName, initTidyOccEnv, isExported, + Module, NamedThing(..), OccName + ) +import TyCon ( TyCon, isDataTyCon ) import PrimOp ( PrimOp(..) ) -import PrelVals ( unpackCStringId, unpackCString2Id, +import PrelInfo ( unpackCStringId, unpackCString2Id, integerZeroId, integerPlusOneId, - integerPlusTwoId, integerMinusOneId + integerPlusTwoId, integerMinusOneId, + int2IntegerId, addr2IntegerId + ) +import Type ( Type, splitAlgTyConApp_maybe, + isUnLiftedType, mkTyVarTy, + tidyType, tidyTypes, tidyTopType, tidyTyVar, tidyTyVars, + Type ) -import Type ( maybeAppDataTyCon, getAppDataTyConExpandingDicts, maybeAppSpecDataTyConExpandingDicts ) -import TysWiredIn ( stringTy ) +import Class ( Class, classSelIds ) +import TysWiredIn ( isIntegerTy ) import LiberateCase ( liberateCase ) -import MagicUFs ( MagicUnfoldingFun ) -import Outputable ( Outputable(..){-instance * (,) -} ) -import PprCore -import PprStyle ( PprStyle(..) ) -import PprType ( GenType{-instance Outputable-}, GenTyVar{-ditto-} ) -import Pretty ( ppShow, ppAboves, ppAbove, ppCat, ppStr ) import SAT ( doStaticArgs ) -import SimplMonad ( zeroSimplCount, showSimplCount, SimplCount ) -import SimplPgm ( simplifyPgm ) -import Specialise -import SpecUtils ( pprSpecErrs ) +import Specialise ( specProgram) +import SpecEnv ( specEnvToList, specEnvFromList ) import StrictAnal ( saWwTopBinds ) -import TyVar ( nullTyVarEnv, GenTyVar{-instance Eq-} ) -import Unique ( integerTyConKey, ratioTyConKey, Unique{-instance Eq-} ) -import UniqSupply ( splitUniqSupply, getUnique ) -import Util ( mapAccumL, assertPanic, panic{-ToDo:rm-}, pprTrace, pprPanic ) -import SrcLoc ( noSrcLoc ) +import Var ( TyVar, mkId ) +import Unique ( Unique, Uniquable(..), + ratioTyConKey, mkUnique, incrUnique, initTidyUniques + ) +import UniqSupply ( UniqSupply, splitUniqSupply, uniqFromSupply ) import Constants ( tARGET_MIN_INT, tARGET_MAX_INT ) +import Util ( mapAccumL ) import Bag import Maybes - - -#ifndef OMIT_DEFORESTER -import Deforest ( deforestProgram ) -import DefUtils ( deforestable ) -#endif - +import IO ( hPutStr, stderr ) +import Outputable \end{code} \begin{code} -core2core :: [CoreToDo] -- spec of what core-to-core passes to do - -> FAST_STRING -- module name (profiling only) - -> PprStyle -- printing style (for debugging only) - -> UniqSupply -- a name supply - -> [TyCon] -- local data tycons and tycon specialisations - -> FiniteMap TyCon [(Bool, [Maybe Type])] - -> [CoreBinding] -- input... - -> IO - ([CoreBinding], -- results: program, plus... - SpecialiseData) -- specialisation data - -core2core core_todos module_name ppr_style us local_tycons tycon_specs binds - = -- Print heading - (if opt_D_verbose_core2core then - hPutStr stderr "VERBOSE CORE-TO-CORE:\n" - else return ()) >> +core2core :: [CoreToDo] -- Spec of what core-to-core passes to do + -> Module -- Module name (profiling only) + -> [Class] -- Local classes + -> UniqSupply -- A name supply + -> [CoreBind] -- Input + -> IO [CoreBind] -- Result + +core2core core_todos module_name classes us binds + = do + let (us1, us2) = splitUniqSupply us -- Do the main business - foldl_mn do_core_pass - (binds, us1, init_specdata, zeroSimplCount) - core_todos - >>= \ (processed_binds, _, spec_data, simpl_stats) -> + processed_binds <- doCorePasses us1 binds core_todos + + -- Do the post-simplification business + post_simpl_binds <- doPostSimplification us2 processed_binds -- Do the final tidy-up - let - final_binds = tidyCorePgm module_name us2 processed_binds - in - - -- Report statistics - (if opt_D_simplifier_stats then - hPutStr stderr ("\nSimplifier Stats:\n") >> - hPutStr stderr (showSimplCount simpl_stats) >> - hPutStr stderr "\n" - else return ()) >> - - -- - return (final_binds, spec_data) - where - (us1, us2) = splitUniqSupply us - init_specdata = initSpecData local_tycons tycon_specs - - ------------- - core_linter = if opt_DoCoreLinting - then lintCoreBindings ppr_style - else ( \ whodunnit spec_done binds -> binds ) - - -------------- - do_core_pass info@(binds, us, spec_data, simpl_stats) to_do - = let - (us1, us2) = splitUniqSupply us - in - case to_do of - CoreDoSimplify simpl_sw_chkr - -> _scc_ "CoreSimplify" - begin_pass ("Simplify" ++ if switchIsOn simpl_sw_chkr SimplDoFoldrBuild - then " (foldr/build)" else "") >> - case (simplifyPgm binds simpl_sw_chkr simpl_stats us1) of - (p, it_cnt, simpl_stats2) - -> end_pass False us2 p spec_data simpl_stats2 - ("Simplify (" ++ show it_cnt ++ ")" - ++ if switchIsOn simpl_sw_chkr SimplDoFoldrBuild - then " foldr/build" else "") - - CoreDoFoldrBuildWorkerWrapper - -> _scc_ "CoreDoFoldrBuildWorkerWrapper" - begin_pass "FBWW" >> - case (mkFoldrBuildWW us1 binds) of { binds2 -> - end_pass False us2 binds2 spec_data simpl_stats "FBWW" } - - CoreDoFoldrBuildWWAnal - -> _scc_ "CoreDoFoldrBuildWWAnal" - begin_pass "AnalFBWW" >> - case (analFBWW binds) of { binds2 -> - end_pass False us2 binds2 spec_data simpl_stats "AnalFBWW" } - - CoreLiberateCase - -> _scc_ "LiberateCase" - begin_pass "LiberateCase" >> - case (liberateCase opt_LiberateCaseThreshold binds) of { binds2 -> - end_pass False us2 binds2 spec_data simpl_stats "LiberateCase" } - - CoreDoFloatInwards - -> _scc_ "FloatInwards" - begin_pass "FloatIn" >> - case (floatInwards binds) of { binds2 -> - end_pass False us2 binds2 spec_data simpl_stats "FloatIn" } - - CoreDoFullLaziness - -> _scc_ "CoreFloating" - begin_pass "FloatOut" >> - case (floatOutwards us1 binds) of { binds2 -> - end_pass False us2 binds2 spec_data simpl_stats "FloatOut" } - - CoreDoStaticArgs - -> _scc_ "CoreStaticArgs" - begin_pass "StaticArgs" >> - case (doStaticArgs binds us1) of { binds2 -> - end_pass False us2 binds2 spec_data simpl_stats "StaticArgs" } - -- Binds really should be dependency-analysed for static- - -- arg transformation... Not to worry, they probably are. - -- (I don't think it *dies* if they aren't [WDP 94/04/15]) - - CoreDoStrictness - -> _scc_ "CoreStranal" - begin_pass "StrAnal" >> - case (saWwTopBinds us1 binds) of { binds2 -> - end_pass False us2 binds2 spec_data simpl_stats "StrAnal" } - - CoreDoSpecialising - -> _scc_ "Specialise" - begin_pass "Specialise" >> - case (specProgram us1 binds spec_data) of { - (p, spec_data2@(SpecData _ spec_noerrs _ _ _ - spec_errs spec_warn spec_tyerrs)) -> - - -- if we got errors, we die straight away - (if not spec_noerrs || - (opt_ShowImportSpecs && not (isEmptyBag spec_warn)) then - hPutStr stderr (ppShow 1000 {-pprCols-} - (pprSpecErrs module_name spec_errs spec_warn spec_tyerrs)) - >> hPutStr stderr "\n" - else - return ()) >> - - (if not spec_noerrs then -- Stop here if specialisation errors occured - ghcExit 1 - else - return ()) >> - - end_pass False us2 p spec_data2 simpl_stats "Specialise" - } - - CoreDoDeforest -#if OMIT_DEFORESTER - -> error "ERROR: CoreDoDeforest: not built into compiler\n" -#else - -> _scc_ "Deforestation" - begin_pass "Deforestation" >> - case (deforestProgram binds us1) of { binds2 -> - end_pass False us2 binds2 spec_data simpl_stats "Deforestation" } -#endif - - CoreDoPrintCore -- print result of last pass - -> end_pass True us2 binds spec_data simpl_stats "Print" - - ------------------------------------------------- - - begin_pass - = if opt_D_show_passes - then \ what -> hPutStr stderr ("*** Core2Core: "++what++"\n") - else \ what -> return () - - end_pass print us2 binds2 - spec_data2@(SpecData spec_done _ _ _ _ _ _ _) - simpl_stats2 what - = -- report verbosely, if required - (if (opt_D_verbose_core2core && not print) || - (print && not opt_D_verbose_core2core) - then - hPutStr stderr ("\n*** "++what++":\n") - >> - hPutStr stderr (ppShow 1000 - (ppAboves (map (pprCoreBinding ppr_style) binds2))) - >> - hPutStr stderr "\n" - else - return ()) >> - let - linted_binds = core_linter what spec_done binds2 - in - return - (linted_binds, -- processed binds, possibly run thru CoreLint - us2, -- UniqueSupply for the next guy - spec_data2, -- possibly-updated specialisation info - simpl_stats2 -- accumulated simplifier stats - ) - --- here so it can be inlined... -foldl_mn f z [] = return z -foldl_mn f z (x:xs) = f z x >>= \ zz -> - foldl_mn f zz xs + final_binds <- tidyCorePgm module_name classes post_simpl_binds + + -- Return results + return final_binds + +doCorePasses us binds [] + = return binds + +doCorePasses us binds (to_do : to_dos) + = do + let (us1, us2) = splitUniqSupply us + binds1 <- doCorePass us1 binds to_do + doCorePasses us2 binds1 to_dos + +doCorePass us binds (CoreDoSimplify sw_chkr) = _scc_ "Simplify" simplifyPgm sw_chkr us binds +doCorePass us binds CoreLiberateCase = _scc_ "LiberateCase" liberateCase binds +doCorePass us binds CoreDoFloatInwards = _scc_ "FloatInwards" floatInwards binds +doCorePass us binds CoreDoFullLaziness = _scc_ "CoreFloating" floatOutwards us binds +doCorePass us binds CoreDoStaticArgs = _scc_ "CoreStaticArgs" doStaticArgs us binds +doCorePass us binds CoreDoStrictness = _scc_ "CoreStranal" saWwTopBinds us binds +doCorePass us binds CoreDoSpecialising = _scc_ "Specialise" specProgram us binds \end{code} +%************************************************************************ +%* * +\subsection{The driver for the simplifier} +%* * +%************************************************************************ + +\begin{code} +simplifyPgm :: (SimplifierSwitch -> SwitchResult) + -> UniqSupply + -> [CoreBind] -- Input + -> IO [CoreBind] -- New bindings + +simplifyPgm sw_chkr us binds + = do { + beginPass "Simplify"; + + (termination_msg, it_count, counts, binds') <- iteration us 1 zeroSimplCount binds; + + dumpIfSet opt_D_simplifier_stats "Simplifier statistics" + (vcat [text termination_msg <+> text "after" <+> ppr it_count <+> text "iterations", + text "", + pprSimplCount counts]); + + endPass "Simplify" + (opt_D_verbose_core2core && not opt_D_dump_simpl_iterations) + binds' + } + where + max_iterations = getSimplIntSwitch sw_chkr MaxSimplifierIterations + simpl_switch_is_on = switchIsOn sw_chkr + + core_iter_dump binds | opt_D_verbose_core2core = pprCoreBindings binds + | otherwise = empty + + iteration us iteration_no counts binds + = do { + -- Occurrence analysis + let { tagged_binds = _scc_ "OccAnal" occurAnalyseBinds simpl_switch_is_on binds }; + dumpIfSet opt_D_dump_occur_anal "Occurrence analysis" + (pprCoreBindings tagged_binds); + + -- Simplify + let { (binds', counts') = initSmpl sw_chkr us1 (simplTopBinds tagged_binds); + all_counts = counts `plusSimplCount` counts' + } ; + + -- Stop if nothing happened; don't dump output + if isZeroSimplCount counts' then + return ("Simplifier reached fixed point", iteration_no, all_counts, binds') + else do { + + -- Dump the result of this iteration + dumpIfSet opt_D_dump_simpl_iterations + ("Simplifier iteration " ++ show iteration_no + ++ " out of " ++ show max_iterations) + (vcat[pprSimplCount counts', + text "", + core_iter_dump binds']) ; + + -- Stop if we've run out of iterations + if iteration_no == max_iterations then + do { + if max_iterations > 1 then + hPutStr stderr ("NOTE: Simplifier still going after " ++ + show max_iterations ++ + " iterations; bailing out.\n") + else return (); + + return ("Simplifier baled out", iteration_no, all_counts, binds') + } + + -- Else loop + else iteration us2 (iteration_no + 1) all_counts binds' + } } + where + (us1, us2) = splitUniqSupply us + + +simplTopBinds binds = go binds `thenSmpl` \ (binds', _) -> + returnSmpl binds' + where + go [] = returnSmpl ([], ()) + go (bind1 : binds) = simplBind bind1 (go binds) +\end{code} + %************************************************************************ %* * -\subsection[SimplCore-indirections]{Eliminating indirections in Core code, and globalising} +\subsection{Tidying core} %* * %************************************************************************ Several tasks are done by @tidyCorePgm@ -1. Eliminate indirections. The point here is to transform - x_local = E - x_exported = x_local - ==> - x_exported = E - -2. Make certain top-level bindings into Globals. The point is that +1. Make certain top-level bindings into Globals. The point is that Global things get externally-visible labels at code generation time -3. Make the representation of NoRep literals explicit, and - float their bindings to the top level -4. Convert - case x of {...; x' -> ...x'...} - ==> - case x of {...; _ -> ...x... } - See notes in SimplCase.lhs, near simplDefault for the reasoning here. +2. Give all binders a nice print-name. Their uniques aren't changed; + rather we give them lexically unique occ-names, so that we can + safely print the OccNae only in the interface file. [Bad idea to + change the uniques, because the code generator makes global labels + from the uniques for local thunks etc.] + + +\begin{code} +tidyCorePgm :: Module -> [Class] -> [CoreBind] -> IO [CoreBind] +tidyCorePgm mod local_classes binds_in + = do + beginPass "Tidy Core" + let (_, binds_out) = mapAccumL (tidyBind (Just mod)) init_tidy_env binds_in + endPass "Tidy Core" (opt_D_dump_simpl || opt_D_verbose_core2core) binds_out + where + -- Make sure to avoid the names of class operations + -- They don't have top-level bindings, so we won't see them + -- in binds_in; so we must initialise the tidy_env appropriately + -- + -- We also make sure to avoid any exported binders. Consider + -- f{-u1-} = 1 -- Local decl + -- ... + -- f{-u2-} = 2 -- Exported decl + -- + -- The second exported decl must 'get' the name 'f', so we + -- have to put 'f' in the avoids list before we get to the first + -- decl. Name.tidyName then does a no-op on exported binders. + init_tidy_env = (initTidyOccEnv avoids, emptyVarEnv) + avoids = [getOccName sel_id | cls <- local_classes, + sel_id <- classSelIds cls] + ++ + [getOccName bndr | bind <- binds_in, + bndr <- bindersOf bind, + isExported bndr] + +tidyBind :: Maybe Module -- (Just m) for top level, Nothing for nested + -> TidyEnv + -> CoreBind + -> (TidyEnv, CoreBind) +tidyBind maybe_mod env (NonRec bndr rhs) + = let + (env', bndr') = tidyBndr maybe_mod env bndr + rhs' = tidyExpr env rhs + in + (env', NonRec bndr' rhs') + +tidyBind maybe_mod env (Rec pairs) + = let + -- We use env' when tidying the rhss + -- When tidying the binder itself we may tidy it's + -- specialisations; if any of these mention other binders + -- in the group we should really feed env' to them too; + -- but that seems (a) unlikely and (b) a bit tiresome. + -- So I left it out for now + + (bndrs, rhss) = unzip pairs + (env', bndrs') = mapAccumL (tidyBndr maybe_mod) env bndrs + rhss' = map (tidyExpr env') rhss + in + (env', Rec (zip bndrs' rhss')) + +tidyExpr env (Type ty) = Type (tidyType env ty) +tidyExpr env (Con con args) = Con con (map (tidyExpr env) args) +tidyExpr env (App f a) = App (tidyExpr env f) (tidyExpr env a) +tidyExpr env (Note n e) = Note (tidyNote env n) (tidyExpr env e) + +tidyExpr env (Let b e) = Let b' (tidyExpr env' e) + where + (env', b') = tidyBind Nothing env b + +tidyExpr env (Case e b alts) = Case (tidyExpr env e) b' (map (tidyAlt env') alts) + where + (env', b') = tidyNestedBndr env b + +tidyExpr env (Var v) = case lookupVarEnv var_env v of + Just v' -> Var v' + Nothing -> Var v + where + (_, var_env) = env + +tidyExpr env (Lam b e) = Lam b' (tidyExpr env' e) + where + (env', b') = tidyNestedBndr env b + +tidyAlt env (con, vs, rhs) = (con, vs', tidyExpr env' rhs) + where + (env', vs') = mapAccumL tidyNestedBndr env vs + +tidyNote env (Coerce t1 t2) = Coerce (tidyType env t1) (tidyType env t2) + +tidyNote env note = note +\end{code} -5. *Mangle* cases involving fork# and par# in the discriminant. The - original templates for these primops (see @PrelVals.lhs@) constructed - case expressions with boolean results solely to fool the strictness - analyzer, the simplifier, and anyone else who might want to fool with - the evaluation order. At this point in the compiler our evaluation - order is safe. Therefore, we convert expressions of the form: +\begin{code} +tidyBndr (Just mod) env id = tidyTopBndr mod env id +tidyBndr Nothing env var = tidyNestedBndr env var + +tidyNestedBndr env tyvar + | isTyVar tyvar + = tidyTyVar env tyvar + +tidyNestedBndr env@(tidy_env, var_env) id + = -- Non-top-level variables + let + -- Give the Id a fresh print-name, *and* rename its type + name' = mkLocalName (getUnique id) occ' + (tidy_env', occ') = tidyOccName tidy_env (getOccName id) + ty' = tidyType env (idType id) + id' = mkUserId name' ty' + -- NB: This throws away the IdInfo of the Id, which we + -- no longer need. That means we don't need to + -- run over it with env, nor renumber it. + var_env' = extendVarEnv var_env id id' + in + ((tidy_env', var_env'), id') + +tidyTopBndr mod env@(tidy_env, var_env) id + = -- Top level variables + let + (tidy_env', name') = tidyTopName mod tidy_env (idName id) + ty' = tidyTopType (idType id) + idinfo' = tidyIdInfo env (idInfo id) + id' = mkId name' ty' (idDetails id) idinfo' + var_env' = extendVarEnv var_env id id' + in + ((tidy_env', var_env'), id') + +-- tidyIdInfo does these things: +-- a) tidy the specialisation info (if any) +-- b) zap a complicated ICanSafelyBeINLINEd pragma, +-- c) zap the unfolding +-- The latter two are to avoid space leaks + +tidyIdInfo env info + = info3 + where + spec_items = specEnvToList (specInfo info) + spec_env' = specEnvFromList (map tidy_item spec_items) + info1 | null spec_items = info + | otherwise = spec_env' `setSpecInfo` info + + info2 = case inlinePragInfo info of + ICanSafelyBeINLINEd _ _ -> NoInlinePragInfo `setInlinePragInfo` info1 + other -> info1 + + info3 = noUnfolding `setUnfoldingInfo` info2 + + tidy_item (tyvars, tys, rhs) + = (tyvars', tidyTypes env' tys, tidyExpr env rhs) + where + (env', tyvars') = tidyTyVars env tyvars +\end{code} + + + +%************************************************************************ +%* * +\subsection{PostSimplification} +%* * +%************************************************************************ + +Several tasks are performed by the post-simplification pass + +1. Make the representation of NoRep literals explicit, and + float their bindings to the top level. We only do the floating + part for NoRep lits inside a lambda (else no gain). We need to + take care with let x = "foo" in e + that we don't end up with a silly binding + let x = y in e + with a floated "foo". What a bore. + +2. *Mangle* cases involving par# in the discriminant. The unfolding + for par in PrelConc.lhs include case expressions with integer + results solely to fool the strictness analyzer, the simplifier, + and anyone else who might want to fool with the evaluation order. + At this point in the compiler our evaluation order is safe. + Therefore, we convert expressions of the form: case par# e of - True -> rhs - False -> parError# + 0# -> rhs + _ -> parError# ==> case par# e of _ -> rhs -6. Eliminate polymorphic case expressions. We can't generate code for them yet. + fork# isn't handled like this - it's an explicit IO operation now. + The reason is that fork# returns a ThreadId#, which gets in the + way of the above scheme. And anyway, IO is the only guaranteed + way to enforce ordering --SDM. -Eliminate indirections -~~~~~~~~~~~~~~~~~~~~~~ -In @elimIndirections@, we look for things at the top-level of the form... -\begin{verbatim} - x_local = .... - x_exported = x_local -\end{verbatim} -In cases we find like this, we go {\em backwards} and replace -\tr{x_local} with \tr{x_exported}. This save a gratuitous jump -(from \tr{x_exported} to \tr{x_local}), and makes strictness -information propagate better. - -We rely on prior eta reduction to simplify things like -\begin{verbatim} - x_exported = /\ tyvars -> x_local tyvars -==> +3. Mangle cases involving seq# in the discriminant. Up to this + point, seq# will appear like this: + + case seq# e of + 0# -> seqError# + _ -> ... + + where the 0# branch is purely to bamboozle the strictness analyser + (see case 4 above). This code comes from an unfolding for 'seq' + in Prelude.hs. We translate this into + + case e of + _ -> ... + + Now that the evaluation order is safe. + +4. Do eta reduction for lambda abstractions appearing in: + - the RHS of case alternatives + - the body of a let + + These will otherwise turn into local bindings during Core->STG; + better to nuke them if possible. (In general the simplifier does + eta expansion not eta reduction, up to this point. It does eta + on the RHSs of bindings but not the RHSs of case alternatives and + let bodies) + + +------------------- NOT DONE ANY MORE ------------------------ +[March 98] Indirections are now elimianted by the occurrence analyser +1. Eliminate indirections. The point here is to transform + x_local = E x_exported = x_local -\end{verbatim} + ==> + x_exported = E + +[Dec 98] [Not now done because there is no penalty in the code + generator for using the former form] +2. Convert + case x of {...; x' -> ...x'...} + ==> + case x of {...; _ -> ...x... } + See notes in SimplCase.lhs, near simplDefault for the reasoning here. +-------------------------------------------------------------- -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 = .... +Special case +~~~~~~~~~~~~ - x_exported2 = x_exported1 -\end{verbatim} +NOT ENABLED AT THE MOMENT (because the floated Ids are global-ish +things, and we need local Ids for non-floated stuff): -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. + Don't float stuff out of a binder that's marked as a bottoming Id. + Reason: it doesn't do any good, and creates more CAFs that increase + the size of SRTs. -General Strategy: first collect the info; then make a \tr{Id -> Id} mapping. -Then blast the whole program (LHSs as well as RHSs) with it. +eg. + f = error "string" +is translated to -\begin{code} -tidyCorePgm :: Module -> UniqSupply -> [CoreBinding] -> [CoreBinding] + f' = unpackCString# "string" + f = error f' -tidyCorePgm mod us binds_in - = initTM mod indirection_env us $ - tidyTopBindings (catMaybes reduced_binds) `thenTM` \ binds -> - returnTM (bagToList binds) - where - (indirection_env, reduced_binds) = mapAccumL try_bind nullIdEnv binds_in - - try_bind :: IdEnv Id -> CoreBinding -> (IdEnv Id, Maybe CoreBinding) - try_bind env_so_far - (NonRec exported_binder (Var local_id)) - | isExported exported_binder && -- Only if this is exported - isLocallyDefined local_id && -- Only if this one is defined in this - not (isExported local_id) && -- module, so that we *can* change its - -- binding to be the exported thing! - not (maybeToBool (lookupIdEnv env_so_far local_id)) - -- Only if not already substituted for - = (addOneToIdEnv env_so_far local_id exported_binder, Nothing) - - try_bind env_so_far bind - = (env_so_far, Just bind) -\end{code} +hence f' and f become CAFs. Instead, the special case for +tidyTopBinding below makes sure this comes out as -Top level bindings -~~~~~~~~~~~~~~~~~~ -\begin{code} -tidyTopBindings [] = returnTM emptyBag -tidyTopBindings (b:bs) - = tidyTopBinding b $ - tidyTopBindings bs - -tidyTopBinding :: CoreBinding - -> TidyM (Bag CoreBinding) - -> TidyM (Bag CoreBinding) - -tidyTopBinding (NonRec bndr rhs) thing_inside - = getFloats (tidyCoreExpr rhs) `thenTM` \ (rhs',floats) -> - mungeTopBinder bndr $ \ bndr' -> - thing_inside `thenTM` \ binds -> - returnTM ((floats `snocBag` NonRec bndr' rhs') `unionBags` binds) - -tidyTopBinding (Rec pairs) thing_inside - = mungeTopBinders binders $ \ binders' -> - getFloats (mapTM tidyCoreExpr rhss) `thenTM` \ (rhss', floats) -> - thing_inside `thenTM` \ binds_inside -> - returnTM ((floats `snocBag` Rec (binders' `zip` rhss')) `unionBags` binds_inside) - where - (binders, rhss) = unzip pairs -\end{code} + f = let f' = unpackCString# "string" in error f' +and we can safely ignore f as a CAF, since it can only ever be entered once. -Local Bindings -~~~~~~~~~~~~~~ -\begin{code} -tidyCoreBinding (NonRec bndr rhs) - = tidyCoreExpr rhs `thenTM` \ rhs' -> - returnTM (NonRec bndr rhs') -tidyCoreBinding (Rec pairs) - = mapTM do_one pairs `thenTM` \ pairs' -> - returnTM (Rec pairs') - where - do_one (bndr,rhs) = tidyCoreExpr rhs `thenTM` \ rhs' -> - returnTM (bndr, rhs') +\begin{code} +doPostSimplification :: UniqSupply -> [CoreBind] -> IO [CoreBind] +doPostSimplification us binds_in + = do + beginPass "Post-simplification pass" + let binds_out = initPM us (postSimplTopBinds binds_in) + endPass "Post-simplification pass" opt_D_verbose_core2core binds_out + +postSimplTopBinds :: [CoreBind] -> PostM [CoreBind] +postSimplTopBinds binds + = mapPM postSimplTopBind binds `thenPM` \ binds' -> + returnPM (bagToList (unionManyBags binds')) + +postSimplTopBind :: CoreBind -> PostM (Bag CoreBind) +postSimplTopBind (NonRec bndr rhs) + | isBottomingId bndr -- Don't lift out floats for bottoming Ids + -- See notes above + = getFloatsPM (postSimplExpr rhs) `thenPM` \ (rhs', floats) -> + returnPM (unitBag (NonRec bndr (foldrBag Let rhs' floats))) + +postSimplTopBind bind + = getFloatsPM (postSimplBind bind) `thenPM` \ (bind', floats) -> + returnPM (floats `snocBag` bind') + +postSimplBind (NonRec bndr rhs) + = postSimplExpr rhs `thenPM` \ rhs' -> + returnPM (NonRec bndr rhs') + +postSimplBind (Rec pairs) + = mapPM postSimplExpr rhss `thenPM` \ rhss' -> + returnPM (Rec (bndrs `zip` rhss')) + where + (bndrs, rhss) = unzip pairs \end{code} Expressions ~~~~~~~~~~~ \begin{code} -tidyCoreExpr (Var v) = lookupTM v `thenTM` \ v' -> - returnTM (Var v') - -tidyCoreExpr (Lit lit) - = litToRep lit `thenTM` \ (_, lit_expr) -> - returnTM lit_expr - -tidyCoreExpr (App fun arg) - = tidyCoreExpr fun `thenTM` \ fun' -> - tidyCoreArg arg `thenTM` \ arg' -> - returnTM (App fun' arg') - -tidyCoreExpr (Con con args) - = mapTM tidyCoreArg args `thenTM` \ args' -> - returnTM (Con con args') - -tidyCoreExpr (Prim prim args) - = mapTM tidyCoreArg args `thenTM` \ args' -> - returnTM (Prim prim args') - -tidyCoreExpr (Lam bndr body) - = tidyCoreExpr body `thenTM` \ body' -> - returnTM (Lam bndr body') - -tidyCoreExpr (Let bind body) - = tidyCoreBinding bind `thenTM` \ bind' -> - tidyCoreExpr body `thenTM` \ body' -> - returnTM (Let bind' body') - -tidyCoreExpr (SCC cc body) - = tidyCoreExpr body `thenTM` \ body' -> - returnTM (SCC cc body') - -tidyCoreExpr (Coerce coercion ty body) - = tidyCoreExpr body `thenTM` \ body' -> - returnTM (Coerce coercion ty body') - --- Wierd case for par, seq, fork etc. See notes above. -tidyCoreExpr (Case scrut@(Prim op args) (PrimAlts _ (BindDefault binder rhs))) - | funnyParallelOp op - = tidyCoreExpr scrut `thenTM` \ scrut' -> - tidyCoreExpr rhs `thenTM` \ rhs' -> - returnTM (Case scrut' (PrimAlts [] (BindDefault binder rhs'))) - --- Eliminate polymorphic case, for which we can't generate code just yet -tidyCoreExpr (Case scrut (AlgAlts [] (BindDefault deflt_bndr rhs))) - | not (maybeToBool (maybeAppSpecDataTyConExpandingDicts (coreExprType scrut))) - = pprTrace "Warning: discarding polymophic case:" (ppr PprDebug scrut) $ - case scrut of - Var v -> extendEnvTM deflt_bndr v (tidyCoreExpr rhs) - other -> tidyCoreExpr (Let (NonRec deflt_bndr scrut) rhs) - -tidyCoreExpr (Case scrut alts) - = tidyCoreExpr scrut `thenTM` \ scrut' -> - tidy_alts alts `thenTM` \ alts' -> - returnTM (Case scrut' alts') +postSimplExpr (Var v) = returnPM (Var v) +postSimplExpr (Type ty) = returnPM (Type ty) + +postSimplExpr (App fun arg) + = postSimplExpr fun `thenPM` \ fun' -> + postSimplExpr arg `thenPM` \ arg' -> + returnPM (App fun' arg') + +postSimplExpr (Con (Literal lit) args) + = ASSERT( null args ) + litToRep lit `thenPM` \ (lit_ty, lit_expr) -> + getInsideLambda `thenPM` \ in_lam -> + if in_lam && not (exprIsTrivial lit_expr) then + -- It must have been a no-rep literal with a + -- non-trivial representation; and we're inside a lambda; + -- so float it to the top + addTopFloat lit_ty lit_expr `thenPM` \ v -> + returnPM (Var v) + else + returnPM lit_expr + +postSimplExpr (Con con args) + = mapPM postSimplExpr args `thenPM` \ args' -> + returnPM (Con con args') + +postSimplExpr (Lam bndr body) + = insideLambda bndr $ + postSimplExpr body `thenPM` \ body' -> + returnPM (Lam bndr body') + +postSimplExpr (Let bind body) + = postSimplBind bind `thenPM` \ bind' -> + postSimplExprEta body `thenPM` \ body' -> + returnPM (Let bind' body') + +postSimplExpr (Note note body) + = postSimplExprEta body `thenPM` \ body' -> + returnPM (Note note body') + +-- seq#: see notes above. +-- NB: seq# :: forall a. a -> Int# +postSimplExpr (Case scrut@(Con (PrimOp SeqOp) [Type ty, e]) bndr alts) + = postSimplExpr e `thenPM` \ e' -> + let + -- The old binder can't have been used, so we + -- can gaily re-use it (yuk!) + new_bndr = setIdType bndr ty + in + postSimplExprEta default_rhs `thenPM` \ rhs' -> + returnPM (Case e' new_bndr [(DEFAULT,[],rhs')]) where - tidy_alts (AlgAlts alts deflt) - = mapTM tidy_alg_alt alts `thenTM` \ alts' -> - tidy_deflt deflt `thenTM` \ deflt' -> - returnTM (AlgAlts alts' deflt') - - tidy_alts (PrimAlts alts deflt) - = mapTM tidy_prim_alt alts `thenTM` \ alts' -> - tidy_deflt deflt `thenTM` \ deflt' -> - returnTM (PrimAlts alts' deflt') - - tidy_alg_alt (con,bndrs,rhs) = tidyCoreExpr rhs `thenTM` \ rhs' -> - returnTM (con,bndrs,rhs') + (other_alts, maybe_default) = findDefault alts + Just default_rhs = maybe_default + +-- par#: see notes above. +postSimplExpr (Case scrut@(Con (PrimOp op) args) bndr alts) + | funnyParallelOp op && maybeToBool maybe_default + = postSimplExpr scrut `thenPM` \ scrut' -> + postSimplExprEta default_rhs `thenPM` \ rhs' -> + returnPM (Case scrut' bndr [(DEFAULT,[],rhs')]) + where + (other_alts, maybe_default) = findDefault alts + Just default_rhs = maybe_default - tidy_prim_alt (lit,rhs) = tidyCoreExpr rhs `thenTM` \ rhs' -> - returnTM (lit,rhs') +postSimplExpr (Case scrut case_bndr alts) + = postSimplExpr scrut `thenPM` \ scrut' -> + mapPM ps_alt alts `thenPM` \ alts' -> + returnPM (Case scrut' case_bndr alts') + where + ps_alt (con,bndrs,rhs) = postSimplExprEta rhs `thenPM` \ rhs' -> + returnPM (con, bndrs, rhs') - -- We convert case x of {...; x' -> ...x'...} - -- to - -- case x of {...; _ -> ...x... } - -- - -- See notes in SimplCase.lhs, near simplDefault for the reasoning. - -- It's quite easily done: simply extend the environment to bind the - -- default binder to the scrutinee. - - tidy_deflt NoDefault = returnTM NoDefault - tidy_deflt (BindDefault bndr rhs) - = extend_env (tidyCoreExpr rhs) `thenTM` \ rhs' -> - returnTM (BindDefault bndr rhs') - where - extend_env = case scrut of - Var v -> extendEnvTM bndr v - other -> \x -> x +postSimplExprEta e = postSimplExpr e `thenPM` \ e' -> + returnPM (etaCoreExpr e') \end{code} -Arguments -~~~~~~~~~ \begin{code} -tidyCoreArg :: CoreArg -> TidyM CoreArg - -tidyCoreArg (VarArg v) - = lookupTM v `thenTM` \ v' -> - returnTM (VarArg v') - -tidyCoreArg (LitArg lit) - = litToRep lit `thenTM` \ (lit_ty, lit_expr) -> - case lit_expr of - Var v -> returnTM (VarArg v) - Lit l -> returnTM (LitArg l) - other -> addTopFloat lit_ty lit_expr `thenTM` \ v -> - returnTM (VarArg v) - -tidyCoreArg (TyArg ty) = returnTM (TyArg ty) -tidyCoreArg (UsageArg u) = returnTM (UsageArg u) -\end{code} +funnyParallelOp ParOp = True +funnyParallelOp _ = False +\end{code} %************************************************************************ @@ -551,21 +610,20 @@ We always replace them with a simple variable, and float a suitable binding out to the top level. \begin{code} - -litToRep :: Literal -> TidyM (Type, CoreExpr) +litToRep :: Literal -> PostM (Type, CoreExpr) -litToRep (NoRepStr s) - = returnTM (stringTy, rhs) +litToRep (NoRepStr s ty) + = returnPM (ty, rhs) where rhs = if (any is_NUL (_UNPK_ s)) then -- Must cater for NULs in literal string - mkGenApp (Var unpackCString2Id) - [LitArg (MachStr s), - LitArg (mkMachInt (toInteger (_LENGTH_ s)))] + mkApps (Var unpackCString2Id) + [mkLit (MachStr s), + mkLit (mkMachInt (toInteger (_LENGTH_ s)))] else -- No NULs in the string - App (Var unpackCStringId) (LitArg (MachStr s)) + App (Var unpackCStringId) (mkLit (MachStr s)) is_NUL c = c == '\0' \end{code} @@ -576,49 +634,37 @@ otherwise, wrap with @litString2Integer@. \begin{code} litToRep (NoRepInteger i integer_ty) - = returnTM (integer_ty, rhs) + = returnPM (integer_ty, rhs) where - rhs | i == 0 = Var integerZeroId -- Extremely convenient to look out for - | i == 1 = Var integerPlusOneId -- a few very common Integer literals! + rhs | i == 0 = Var integerZeroId -- Extremely convenient to look out for + | i == 1 = Var integerPlusOneId -- a few very common Integer literals! | i == 2 = Var integerPlusTwoId | i == (-1) = Var integerMinusOneId | i > tARGET_MIN_INT && -- Small enough, so start from an Int i < tARGET_MAX_INT - = Prim Int2IntegerOp [LitArg (mkMachInt i)] + = App (Var int2IntegerId) (Con (Literal (mkMachInt i)) []) | otherwise -- Big, so start from a string - = Prim Addr2IntegerOp [LitArg (MachStr (_PK_ (show i)))] + = App (Var addr2IntegerId) (Con (Literal (MachStr (_PK_ (show i)))) []) litToRep (NoRepRational r rational_ty) - = tidyCoreArg (LitArg (NoRepInteger (numerator r) integer_ty)) `thenTM` \ num_arg -> - tidyCoreArg (LitArg (NoRepInteger (denominator r) integer_ty)) `thenTM` \ denom_arg -> - returnTM (rational_ty, Con ratio_data_con [num_arg, denom_arg]) + = postSimplExpr (mkLit (NoRepInteger (numerator r) integer_ty)) `thenPM` \ num_arg -> + postSimplExpr (mkLit (NoRepInteger (denominator r) integer_ty)) `thenPM` \ denom_arg -> + returnPM (rational_ty, mkConApp ratio_data_con [Type integer_ty, num_arg, denom_arg]) where (ratio_data_con, integer_ty) - = case (maybeAppDataTyCon rational_ty) of + = case (splitAlgTyConApp_maybe rational_ty) of Just (tycon, [i_ty], [con]) - -> ASSERT(is_integer_ty i_ty && uniqueOf tycon == ratioTyConKey) + -> ASSERT(isIntegerTy i_ty && getUnique tycon == ratioTyConKey) (con, i_ty) _ -> (panic "ratio_data_con", panic "integer_ty") - is_integer_ty ty - = case (maybeAppDataTyCon ty) of - Just (tycon, [], _) -> uniqueOf tycon == integerTyConKey - _ -> False - -litToRep other_lit = returnTM (literalType other_lit, Lit other_lit) +litToRep other_lit = returnPM (literalType other_lit, mkLit other_lit) \end{code} -\begin{code} -funnyParallelOp SeqOp = True -funnyParallelOp ParOp = True -funnyParallelOp ForkOp = True -funnyParallelOp _ = False -\end{code} - %************************************************************************ %* * @@ -627,65 +673,46 @@ funnyParallelOp _ = False %************************************************************************ \begin{code} -type TidyM a = Module - -> IdEnv Id - -> (UniqSupply, Bag CoreBinding) - -> (a, (UniqSupply, Bag CoreBinding)) - -initTM mod env us m - = case m mod env (us,emptyBag) of - (result, (us',floats)) -> result - -returnTM v mod env usf = (v, usf) -thenTM m k mod env usf = case m mod env usf of - (r, usf') -> k r mod env usf' - -mapTM f [] = returnTM [] -mapTM f (x:xs) = f x `thenTM` \ r -> - mapTM f xs `thenTM` \ rs -> - returnTM (r:rs) -\end{code} - - -\begin{code} -getFloats :: TidyM a -> TidyM (a, Bag CoreBinding) -getFloats m mod env (us,floats) - = case m mod env (us,emptyBag) of - (r, (us',floats')) -> ((r, floats'), (us',floats)) - - --- Need to extend the environment when we munge a binder, so that occurrences --- of the binder will print the correct way (i.e. as a global not a local) -mungeTopBinder :: Id -> (Id -> TidyM a) -> TidyM a -mungeTopBinder id thing_inside mod env usf - = case lookupIdEnv env id of - Just global -> thing_inside global mod env usf - Nothing -> thing_inside new_global mod new_env usf - where - new_env = addOneToIdEnv env id new_global - new_global = setIdVisibility mod id - -mungeTopBinders [] k = k [] -mungeTopBinders (b:bs) k = mungeTopBinder b $ \ b' -> - mungeTopBinders bs $ \ bs' -> - k (b' : bs') - -addTopFloat :: Type -> CoreExpr -> TidyM Id -addTopFloat lit_ty lit_rhs mod env (us, floats) - = (lit_id, (us', floats `snocBag` NonRec lit_id lit_rhs)) - where - lit_local = mkSysLocal SLIT("nrlit") uniq lit_ty noSrcLoc - lit_id = setIdVisibility mod lit_local - (us', us1) = splitUniqSupply us - uniq = getUnique us1 - -lookupTM v mod env usf - = case lookupIdEnv env v of - Nothing -> (v, usf) - Just v' -> (v', usf) - -extendEnvTM v v' m mod env usf - = m mod (addOneToIdEnv env v v') usf +type PostM a = Bool -- True <=> inside a *value* lambda + -> (UniqSupply, Bag CoreBind) -- Unique supply and Floats in + -> (a, (UniqSupply, Bag CoreBind)) + +initPM :: UniqSupply -> PostM a -> a +initPM us m + = case m False {- not inside lambda -} (us, emptyBag) of + (result, _) -> result + +returnPM v in_lam usf = (v, usf) +thenPM m k in_lam usf = case m in_lam usf of + (r, usf') -> k r in_lam usf' + +mapPM f [] = returnPM [] +mapPM f (x:xs) = f x `thenPM` \ r -> + mapPM f xs `thenPM` \ rs -> + returnPM (r:rs) + +insideLambda :: CoreBndr -> PostM a -> PostM a +insideLambda bndr m in_lam usf | isId bndr = m True usf + | otherwise = m in_lam usf + +getInsideLambda :: PostM Bool +getInsideLambda in_lam usf = (in_lam, usf) + +getFloatsPM :: PostM a -> PostM (a, Bag CoreBind) +getFloatsPM m in_lam (us, floats) + = let + (a, (us', floats')) = m in_lam (us, emptyBag) + in + ((a, floats'), (us', floats)) + +addTopFloat :: Type -> CoreExpr -> PostM Id +addTopFloat lit_ty lit_rhs in_lam (us, floats) + = let + (us1, us2) = splitUniqSupply us + uniq = uniqFromSupply us1 + lit_id = mkSysLocal SLIT("lf") uniq lit_ty + in + (lit_id, (us2, floats `snocBag` NonRec lit_id lit_rhs)) \end{code}