X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FsimplCore%2FFloatOut.lhs;h=7fed6f8ae13c82cc397c2e9062b413ddddef4a44;hb=6858f7c15fcf9efe9e6fdf22de34d0791b0f0c08;hp=c1de417350665c0d64d1526835ca902805143dfa;hpb=f01a8e8c9c53bfb5ab3393ed3457ebf25390efa1;p=ghc-hetmet.git diff --git a/ghc/compiler/simplCore/FloatOut.lhs b/ghc/compiler/simplCore/FloatOut.lhs index c1de417..7fed6f8 100644 --- a/ghc/compiler/simplCore/FloatOut.lhs +++ b/ghc/compiler/simplCore/FloatOut.lhs @@ -1,34 +1,30 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[FloatOut]{Float bindings outwards (towards the top level)} ``Long-distance'' floating of bindings towards the top level. \begin{code} -#include "HsVersions.h" - module FloatOut ( floatOutwards ) where -import Ubiq{-uitous-} +#include "HsVersions.h" import CoreSyn - -import CmdLineOpts ( opt_D_verbose_core2core, opt_D_simplifier_stats ) -import CostCentre ( dupifyCC ) -import Id ( nullIdEnv, addOneToIdEnv, growIdEnvList, IdEnv(..), - GenId{-instance Outputable-} +import CoreUtils ( mkSCC ) + +import CmdLineOpts ( DynFlags, DynFlag(..) ) +import ErrUtils ( dumpIfSet_dyn ) +import CostCentre ( dupifyCC, CostCentre ) +import Id ( Id ) +import VarEnv +import CoreLint ( showPass, endPass ) +import SetLevels ( setLevels, + Level(..), tOP_LEVEL, ltMajLvl, ltLvl, isTopLvl ) -import Outputable ( Outputable(..){-instance (,)-} ) -import PprCore ( GenCoreBinding{-instance-} ) -import PprStyle ( PprStyle(..) ) -import PprType -- too lazy to type in all the instances -import Pretty ( ppInt, ppStr, ppBesides, ppAboves ) -import SetLevels -- all of it -import TyVar ( GenTyVar{-instance Eq-} ) -import Unique ( Unique{-instance Eq-} ) -import Usage ( UVar(..) ) -import Util ( pprTrace, panic ) +import UniqSupply ( UniqSupply ) +import List ( partition ) +import Outputable \end{code} Random comments @@ -57,25 +53,17 @@ It turns out that this generates a subexpression of the form @ \deq x ys -> let eq = eqFromEqDict deq in ... @ -which might usefully be separated to +vwhich might usefully be separated to @ \deq -> let eq = eqFromEqDict deq in \xy -> ... @ Well, maybe. We don't do this at the moment. \begin{code} -type LevelledExpr = GenCoreExpr (Id, Level) Id TyVar UVar -type LevelledBind = GenCoreBinding (Id, Level) Id TyVar UVar -type FloatingBind = (Level, Floater) -type FloatingBinds = [FloatingBind] - -data Floater - = LetFloater CoreBinding - | CaseFloater (CoreExpr -> CoreExpr) - -- A CoreExpr with a hole in it: - -- "Give me a right-hand side of the - -- (usually single) alternative, and - -- I'll build the case..." +type LevelledExpr = TaggedExpr Level +type LevelledBind = TaggedBind Level +type FloatBind = (Level, CoreBind) +type FloatBinds = [FloatBind] \end{code} %************************************************************************ @@ -85,40 +73,43 @@ data Floater %************************************************************************ \begin{code} -floatOutwards :: UniqSupply -> [CoreBinding] -> [CoreBinding] - -floatOutwards us pgm - = case (setLevels pgm us) of { annotated_w_levels -> - - case (unzip (map floatTopBind annotated_w_levels)) - of { (fss, final_toplev_binds_s) -> - - (if opt_D_verbose_core2core - then pprTrace "Levels added:\n" - (ppAboves (map (ppr PprDebug) annotated_w_levels)) - else id - ) - ( if not (opt_D_simplifier_stats) then - id - else - let - (tlets, ntlets, lams) = get_stats (sum_stats fss) - in - pprTrace "FloatOut stats: " (ppBesides [ - ppInt tlets, ppStr " Lets floated to top level; ", - ppInt ntlets, ppStr " Lets floated elsewhere; from ", - ppInt lams, ppStr " Lambda groups"]) - ) - concat final_toplev_binds_s - }} +floatOutwards :: DynFlags + -> Bool -- True <=> float lambdas to top level + -> UniqSupply + -> [CoreBind] -> IO [CoreBind] + +floatOutwards dflags float_lams us pgm + = do { + showPass dflags float_msg ; + + let { annotated_w_levels = setLevels float_lams pgm us ; + (fss, binds_s') = unzip (map floatTopBind annotated_w_levels) + } ; + + dumpIfSet_dyn dflags Opt_D_verbose_core2core "Levels added:" + (vcat (map ppr annotated_w_levels)); + + let { (tlets, ntlets, lams) = get_stats (sum_stats fss) }; + + dumpIfSet_dyn dflags Opt_D_dump_simpl_stats "FloatOut stats:" + (hcat [ int tlets, ptext SLIT(" Lets floated to top level; "), + int ntlets, ptext SLIT(" Lets floated elsewhere; from "), + int lams, ptext SLIT(" Lambda groups")]); + + endPass dflags float_msg Opt_D_verbose_core2core (concat binds_s') + {- no specific flag for dumping float-out -} + } + where + float_msg | float_lams = "Float out (floating lambdas too)" + | otherwise = "Float out (not floating lambdas)" floatTopBind bind@(NonRec _ _) - = case (floatBind nullIdEnv tOP_LEVEL bind) of { (fs, floats, bind', _) -> + = case (floatBind emptyVarEnv tOP_LEVEL bind) of { (fs, floats, bind', _) -> (fs, floatsToBinds floats ++ [bind']) } floatTopBind bind@(Rec _) - = case (floatBind nullIdEnv tOP_LEVEL bind) of { (fs, floats, Rec pairs', _) -> + = case (floatBind emptyVarEnv tOP_LEVEL bind) of { (fs, floats, Rec pairs', _) -> -- Actually floats will be empty --false:ASSERT(null floats) (fs, [Rec (floatsToBindPairs floats ++ pairs')]) @@ -136,18 +127,14 @@ floatTopBind bind@(Rec _) floatBind :: IdEnv Level -> Level -> LevelledBind - -> (FloatStats, FloatingBinds, CoreBinding, IdEnv Level) + -> (FloatStats, FloatBinds, CoreBind, IdEnv Level) floatBind env lvl (NonRec (name,level) rhs) - = case (floatExpr env level rhs) of { (fs, rhs_floats, rhs') -> - - -- A good dumping point - case (partitionByMajorLevel level rhs_floats) of { (rhs_floats', heres) -> - - (fs, rhs_floats', - NonRec name (install heres rhs'), - addOneToIdEnv env name level) - }} + = case (floatRhs env level rhs) of { (fs, rhs_floats, rhs') -> + (fs, rhs_floats, + NonRec name rhs', + extendVarEnv env name level) + } floatBind env lvl bind@(Rec pairs) = case (unzip3 (map do_pair pairs)) of { (fss, rhss_floats, new_pairs) -> @@ -178,18 +165,14 @@ floatBind env lvl bind@(Rec pairs) } where - new_env = growIdEnvList env (map fst pairs) + new_env = extendVarEnvList env (map fst pairs) bind_level = getBindLevel bind do_pair ((name, level), rhs) - = case (floatExpr new_env level rhs) of { (fs, rhs_floats, rhs') -> - - -- A good dumping point - case (partitionByMajorLevel level rhs_floats) of { (rhs_floats', heres) -> - - (fs, rhs_floats', (name, install heres rhs')) - }} + = case (floatRhs new_env level rhs) of { (fs, rhs_floats, rhs') -> + (fs, rhs_floats, (name, rhs')) + } \end{code} %************************************************************************ @@ -199,38 +182,46 @@ floatBind env lvl bind@(Rec pairs) %************************************************************************ \begin{code} -floatExpr :: IdEnv Level - -> Level - -> LevelledExpr - -> (FloatStats, FloatingBinds, CoreExpr) - -floatExpr env _ (Var v) = (zero_stats, [], Var v) -floatExpr env _ (Lit l) = (zero_stats, [], Lit l) -floatExpr env _ (Prim op as) = (zero_stats, [], Prim op as) -floatExpr env _ (Con con as) = (zero_stats, [], Con con as) +floatExpr, floatRhs + :: IdEnv Level + -> Level + -> LevelledExpr + -> (FloatStats, FloatBinds, CoreExpr) + +floatRhs env lvl arg + = case (floatExpr env lvl arg) of { (fsa, floats, arg') -> + case (partitionByMajorLevel lvl floats) of { (floats', heres) -> + -- Dump bindings that aren't going to escape from a lambda + -- This is to avoid floating the x binding out of + -- f (let x = e in b) + -- unnecessarily. It even causes a bug to do so if we have + -- y = writeArr# a n (let x = e in b) + -- because the y binding is an expr-ok-for-speculation one. + (fsa, floats', install heres arg') }} + +floatExpr env _ (Var v) = (zeroStats, [], Var v) +floatExpr env _ (Type ty) = (zeroStats, [], Type ty) +floatExpr env _ (Lit lit) = (zeroStats, [], Lit lit) floatExpr env lvl (App e a) - = case (floatExpr env lvl e) of { (fs, floating_defns, e') -> - (fs, floating_defns, App e' a) } + = case (floatExpr env lvl e) of { (fse, floats_e, e') -> + case (floatRhs env lvl a) of { (fsa, floats_a, a') -> + (fse `add_stats` fsa, floats_e ++ floats_a, App e' a') }} -floatExpr env lvl (Lam (UsageBinder _) e) - = panic "FloatOut.floatExpr: Lam UsageBinder" - -floatExpr env lvl (Lam (TyBinder tv) e) - = let - incd_lvl = incMinorLvl lvl - in - case (floatExpr env incd_lvl e) of { (fs, floats, e') -> +floatExpr env lvl (Lam (tv,incd_lvl) e) + | isTyVar tv + = case (floatExpr env incd_lvl e) of { (fs, floats, e') -> -- Dump any bindings which absolutely cannot go any further case (partitionByLevel incd_lvl floats) of { (floats', heres) -> - (fs, floats', Lam (TyBinder tv) (install heres e')) + (fs, floats', Lam tv (install heres e')) }} -floatExpr env lvl (Lam (ValBinder (arg,incd_lvl)) rhs) - = let - new_env = addOneToIdEnv env arg incd_lvl +floatExpr env lvl (Lam (arg,incd_lvl) rhs) + = ASSERT( isId arg ) + let + new_env = extendVarEnv env arg incd_lvl in case (floatExpr new_env incd_lvl rhs) of { (fs, floats, rhs') -> @@ -239,141 +230,79 @@ floatExpr env lvl (Lam (ValBinder (arg,incd_lvl)) rhs) (add_to_stats fs floats', floats', - Lam (ValBinder arg) (install heres rhs')) + Lam arg (install heres rhs')) }} -floatExpr env lvl (SCC cc expr) +floatExpr env lvl (Note note@(SCC cc) expr) = case (floatExpr env lvl expr) of { (fs, floating_defns, expr') -> let - -- annotate bindings floated outwards past an scc expression + -- Annotate bindings floated outwards past an scc expression -- with the cc. We mark that cc as "duplicated", though. annotated_defns = annotate (dupifyCC cc) floating_defns in - (fs, annotated_defns, SCC cc expr') } + (fs, annotated_defns, Note note expr') } where - annotate :: CostCentre -> FloatingBinds -> FloatingBinds + annotate :: CostCentre -> FloatBinds -> FloatBinds annotate dupd_cc defn_groups = [ (level, ann_bind floater) | (level, floater) <- defn_groups ] where - ann_bind (LetFloater (NonRec binder rhs)) - = LetFloater (NonRec binder (ann_rhs rhs)) - - ann_bind (LetFloater (Rec pairs)) - = LetFloater (Rec [(binder, ann_rhs rhs) | (binder, rhs) <- pairs]) - - ann_bind (CaseFloater fn) = CaseFloater ( \ rhs -> SCC dupd_cc (fn rhs) ) - - ann_rhs (Lam arg e) = Lam arg (ann_rhs e) - ann_rhs rhs@(Con _ _) = rhs -- no point in scc'ing WHNF data - ann_rhs rhs = SCC dupd_cc rhs - - -- Note: Nested SCC's are preserved for the benefit of - -- cost centre stack profiling (Durham) - -floatExpr env lvl (Coerce c ty expr) + ann_bind (NonRec binder rhs) + = NonRec binder (mkSCC dupd_cc rhs) + + ann_bind (Rec pairs) + = Rec [(binder, mkSCC dupd_cc rhs) | (binder, rhs) <- pairs] + +-- At one time I tried the effect of not float anything out of an InlineMe, +-- but it sometimes works badly. For example, consider PrelArr.done. It +-- has the form __inline (\d. e) +-- where e doesn't mention d. If we float this to +-- __inline (let x = e in \d. x) +-- things are bad. The inliner doesn't even inline it because it doesn't look +-- like a head-normal form. So it seems a lesser evil to let things float. +-- In SetLevels we do set the context to (Level 0 0) when we get to an InlineMe +-- which discourages floating out. + +floatExpr env lvl (Note note expr) -- Other than SCCs = case (floatExpr env lvl expr) of { (fs, floating_defns, expr') -> - (fs, floating_defns, Coerce c ty expr') } + (fs, floating_defns, Note note expr') } floatExpr env lvl (Let bind body) = case (floatBind env lvl bind) of { (fsb, rhs_floats, bind', new_env) -> case (floatExpr new_env lvl body) of { (fse, body_floats, body') -> (add_stats fsb fse, - rhs_floats ++ [(bind_lvl, LetFloater bind')] ++ body_floats, + rhs_floats ++ [(bind_lvl, bind')] ++ body_floats, body') }} where bind_lvl = getBindLevel bind -floatExpr env lvl (Case scrut alts) - = case (floatExpr env lvl scrut) of { (fse, fde, scrut') -> - - case (scrut', float_alts alts) of - (_, (fsa, fda, alts')) -> - (add_stats fse fsa, fda ++ fde, Case scrut' alts') - } - {- OLD CASE-FLOATING CODE: DROPPED FOR NOW. (SLPJ 7/2/94) - - (Var scrut_var, (fda, AlgAlts [(con,bs,rhs')] NoDefault)) - | scrut_var_lvl `ltMajLvl` lvl -> - - -- Candidate for case floater; scrutinising a variable; it can - -- escape outside a lambda; there's only one alternative. - (fda ++ fde ++ [case_floater], rhs') - - where - case_floater = (scrut_var_lvl, CaseFloater fn) - fn body = Case scrut' (AlgAlts [(con,bs,body)] NoDefault) - scrut_var_lvl = case lookupIdEnv env scrut_var of - Nothing -> Level 0 0 - Just lvl -> unTopify lvl - - END OF CASE FLOATING DROPPED -} +floatExpr env lvl (Case scrut (case_bndr, case_lvl) alts) + = case floatExpr env lvl scrut of { (fse, fde, scrut') -> + case floatList float_alt alts of { (fsa, fda, alts') -> + (add_stats fse fsa, fda ++ fde, Case scrut' case_bndr alts') + }} where - incd_lvl = incMinorLvl lvl + alts_env = extendVarEnv env case_bndr case_lvl partition_fn = partitionByMajorLevel -{- OMITTED - We don't want to be too keen about floating lets out of case alternatives - because they may benefit from seeing the evaluation done by the case. - - The main reason for doing this is to allocate in fewer larger blocks - but that's really an STG-level issue. - - case alts of - -- Just one alternative, then dump only - -- what *has* to be dumped - AlgAlts [_] NoDefault -> partitionByLevel - AlgAlts [] (BindDefault _ _) -> partitionByLevel - PrimAlts [_] NoDefault -> partitionByLevel - PrimAlts [] (BindDefault _ _) -> partitionByLevel - - -- If there's more than one alternative, then - -- this is a dumping point - other -> partitionByMajorLevel --} - - float_alts (AlgAlts alts deflt) - = case (float_deflt deflt) of { (fsd, fdd, deflt') -> - case (unzip3 (map float_alg_alt alts)) of { (fsas, fdas, alts') -> - (foldr add_stats fsd fsas, - concat fdas ++ fdd, - AlgAlts alts' deflt') }} - - float_alts (PrimAlts alts deflt) - = case (float_deflt deflt) of { (fsd, fdd, deflt') -> - case (unzip3 (map float_prim_alt alts)) of { (fsas, fdas, alts') -> - (foldr add_stats fsd fsas, - concat fdas ++ fdd, - PrimAlts alts' deflt') }} - - ------------- - float_alg_alt (con, bs, rhs) + float_alt (con, bs, rhs) = let bs' = map fst bs - new_env = growIdEnvList env bs + new_env = extendVarEnvList alts_env bs in - case (floatExpr new_env incd_lvl rhs) of { (fs, rhs_floats, rhs') -> - case (partition_fn incd_lvl rhs_floats) of { (rhs_floats', heres) -> + case (floatExpr new_env case_lvl rhs) of { (fs, rhs_floats, rhs') -> + case (partition_fn case_lvl rhs_floats) of { (rhs_floats', heres) -> (fs, rhs_floats', (con, bs', install heres rhs')) }} - -------------- - float_prim_alt (lit, rhs) - = case (floatExpr env incd_lvl rhs) of { (fs, rhs_floats, rhs') -> - case (partition_fn incd_lvl rhs_floats) of { (rhs_floats', heres) -> - (fs, rhs_floats', (lit, install heres rhs')) }} - - -------------- - float_deflt NoDefault = (zero_stats, [], NoDefault) - - float_deflt (BindDefault (b,lvl) rhs) - = case (floatExpr new_env lvl rhs) of { (fs, rhs_floats, rhs') -> - case (partition_fn incd_lvl rhs_floats) of { (rhs_floats', heres) -> - (fs, rhs_floats', BindDefault b (install heres rhs')) }} - where - new_env = addOneToIdEnv env b lvl + +floatList :: (a -> (FloatStats, FloatBinds, b)) -> [a] -> (FloatStats, FloatBinds, [b]) +floatList f [] = (zeroStats, [], []) +floatList f (a:as) = case f a of { (fs_a, binds_a, b) -> + case floatList f as of { (fs_as, binds_as, bs) -> + (fs_a `add_stats` fs_as, binds_a ++ binds_as, b:bs) }} \end{code} %************************************************************************ @@ -393,9 +322,9 @@ data FloatStats get_stats (FlS a b c) = (a, b, c) -zero_stats = FlS 0 0 0 +zeroStats = FlS 0 0 0 -sum_stats xs = foldr add_stats zero_stats xs +sum_stats xs = foldr add_stats zeroStats xs add_stats (FlS a1 b1 c1) (FlS a2 b2 c2) = FlS (a1 + a2) (b1 + b2) (c1 + c2) @@ -408,6 +337,7 @@ add_to_stats (FlS a b c) floats to_very_top (my_lvl, _) = isTopLvl my_lvl \end{code} + %************************************************************************ %* * \subsection{Utility bits for floating} @@ -423,17 +353,25 @@ getBindLevel (Rec (((_,lvl), _) : _)) = lvl partitionByMajorLevel, partitionByLevel :: Level -- Partitioning level - -> FloatingBinds -- Defns to be divided into 2 piles... + -> FloatBinds -- Defns to be divided into 2 piles... - -> (FloatingBinds, -- Defns with level strictly < partition level, - FloatingBinds) -- The rest + -> (FloatBinds, -- Defns with level strictly < partition level, + FloatBinds) -- The rest partitionByMajorLevel ctxt_lvl defns = partition float_further defns where - float_further (my_lvl, _) = my_lvl `ltMajLvl` ctxt_lvl || - isTopLvl my_lvl + -- Float it if we escape a value lambda, + -- or if we get to the top level + float_further (my_lvl, bind) = my_lvl `ltMajLvl` ctxt_lvl || isTopLvl my_lvl + -- The isTopLvl part says that if we can get to the top level, say "yes" anyway + -- This means that + -- x = f e + -- transforms to + -- lvl = e + -- x = f lvl + -- which is as it should be partitionByLevel ctxt_lvl defns = partition float_further defns @@ -442,25 +380,20 @@ partitionByLevel ctxt_lvl defns \end{code} \begin{code} -floatsToBinds :: FloatingBinds -> [CoreBinding] -floatsToBinds floats = map get_bind floats - where - get_bind (_, LetFloater bind) = bind - get_bind (_, CaseFloater _) = panic "floatsToBinds" +floatsToBinds :: FloatBinds -> [CoreBind] +floatsToBinds floats = map snd floats -floatsToBindPairs :: FloatingBinds -> [(Id,CoreExpr)] +floatsToBindPairs :: FloatBinds -> [(Id,CoreExpr)] floatsToBindPairs floats = concat (map mk_pairs floats) where - mk_pairs (_, LetFloater (Rec pairs)) = pairs - mk_pairs (_, LetFloater (NonRec binder rhs)) = [(binder,rhs)] - mk_pairs (_, CaseFloater _) = panic "floatsToBindPairs" + mk_pairs (_, Rec pairs) = pairs + mk_pairs (_, NonRec binder rhs) = [(binder,rhs)] -install :: FloatingBinds -> CoreExpr -> CoreExpr +install :: FloatBinds -> CoreExpr -> CoreExpr install defn_groups expr = foldr install_group expr defn_groups where - install_group (_, LetFloater defns) body = Let defns body - install_group (_, CaseFloater fn) body = fn body + install_group (_, defns) body = Let defns body \end{code}