diff options
| -rw-r--r-- | ghc/compiler/coreSyn/CorePrep.lhs | 140 |
1 files changed, 88 insertions, 52 deletions
diff --git a/ghc/compiler/coreSyn/CorePrep.lhs b/ghc/compiler/coreSyn/CorePrep.lhs index d2515c9cb5..18444b6892 100644 --- a/ghc/compiler/coreSyn/CorePrep.lhs +++ b/ghc/compiler/coreSyn/CorePrep.lhs @@ -109,7 +109,7 @@ corePrepPgm dflags binds types binds_out = initUs_ us ( corePrepTopBinds binds `thenUs` \ floats1 -> corePrepTopBinds implicit_binds `thenUs` \ floats2 -> - returnUs (deFloatTop (floats1 `appOL` floats2)) + returnUs (deFloatTop (floats1 `appendFloats` floats2)) ) endPass dflags "CorePrep" Opt_D_dump_prep binds_out @@ -179,45 +179,81 @@ data FloatingBind = FloatLet CoreBind | FloatCase Id CoreExpr Bool -- The bool indicates "ok-for-speculation" +data Floats = Floats OkToSpec (OrdList FloatingBind) + +-- Can we float these binds out of the rhs of a let? We cache this decision +-- to avoid having to recompute it in a non-linear way when there are +-- deeply nested lets. +data OkToSpec + = NotOkToSpec -- definitely not + | OkToSpec -- yes + | IfUnboxedOk -- only if floating an unboxed binding is ok + +emptyFloats :: Floats +emptyFloats = Floats OkToSpec nilOL + +addFloat :: Floats -> FloatingBind -> Floats +addFloat (Floats ok_to_spec floats) new_float + = Floats (combine ok_to_spec (check new_float)) (floats `snocOL` new_float) + where + check (FloatLet _) = OkToSpec + check (FloatCase _ _ ok_for_spec) + | ok_for_spec = IfUnboxedOk + | otherwise = NotOkToSpec + -- The ok-for-speculation flag says that it's safe to + -- float this Case out of a let, and thereby do it more eagerly + -- We need the top-level flag because it's never ok to float + -- an unboxed binding to the top level + +unitFloat :: FloatingBind -> Floats +unitFloat = addFloat emptyFloats + +appendFloats :: Floats -> Floats -> Floats +appendFloats (Floats spec1 floats1) (Floats spec2 floats2) + = Floats (combine spec1 spec2) (floats1 `appOL` floats2) + +concatFloats :: [Floats] -> Floats +concatFloats = foldr appendFloats emptyFloats + +combine NotOkToSpec _ = NotOkToSpec +combine _ NotOkToSpec = NotOkToSpec +combine IfUnboxedOk _ = IfUnboxedOk +combine _ IfUnboxedOk = IfUnboxedOk +combine _ _ = OkToSpec + instance Outputable FloatingBind where ppr (FloatLet bind) = text "FloatLet" <+> ppr bind ppr (FloatCase b rhs spec) = text "FloatCase" <+> ppr b <+> ppr spec <+> equals <+> ppr rhs type CloneEnv = IdEnv Id -- Clone local Ids -deFloatTop :: OrdList FloatingBind -> [CoreBind] +deFloatTop :: Floats -> [CoreBind] -- For top level only; we don't expect any FloatCases -deFloatTop floats +deFloatTop (Floats _ floats) = foldrOL get [] floats where get (FloatLet b) bs = b:bs get b bs = pprPanic "corePrepPgm" (ppr b) -allLazy :: TopLevelFlag -> RecFlag -> OrdList FloatingBind -> Bool -allLazy top_lvl is_rec floats - = foldrOL check True floats - where - unboxed_ok = isNotTopLevel top_lvl && isNonRec is_rec - - check (FloatLet _) y = y - check (FloatCase _ _ ok_for_spec) y = unboxed_ok && ok_for_spec && y - -- The ok-for-speculation flag says that it's safe to - -- float this Case out of a let, and thereby do it more eagerly - -- We need the top-level flag because it's never ok to float - -- an unboxed binding to the top level +allLazy :: TopLevelFlag -> RecFlag -> Floats -> Bool +allLazy top_lvl is_rec (Floats ok_to_spec _) + = case ok_to_spec of + OkToSpec -> True + NotOkToSpec -> False + IfUnboxedOk -> isNotTopLevel top_lvl && isNonRec is_rec -- --------------------------------------------------------------------------- -- Bindings -- --------------------------------------------------------------------------- -corePrepTopBinds :: [CoreBind] -> UniqSM (OrdList FloatingBind) +corePrepTopBinds :: [CoreBind] -> UniqSM Floats corePrepTopBinds binds = go emptyVarEnv binds where - go env [] = returnUs nilOL + go env [] = returnUs emptyFloats go env (bind : binds) = corePrepTopBind env bind `thenUs` \ (env', bind') -> go env' binds `thenUs` \ binds' -> - returnUs (bind' `appOL` binds') + returnUs (bind' `appendFloats` binds') -- NB: we do need to float out of top-level bindings -- Consider x = length [True,False] @@ -247,16 +283,16 @@ corePrepTopBinds binds -- it looks difficult. -------------------------------- -corePrepTopBind :: CloneEnv -> CoreBind -> UniqSM (CloneEnv, OrdList FloatingBind) +corePrepTopBind :: CloneEnv -> CoreBind -> UniqSM (CloneEnv, Floats) corePrepTopBind env (NonRec bndr rhs) = cloneBndr env bndr `thenUs` \ (env', bndr') -> corePrepRhs TopLevel NonRecursive env (bndr, rhs) `thenUs` \ (floats, rhs') -> - returnUs (env', floats `snocOL` FloatLet (NonRec bndr' rhs')) + returnUs (env', addFloat floats (FloatLet (NonRec bndr' rhs'))) corePrepTopBind env (Rec pairs) = corePrepRecPairs TopLevel env pairs -------------------------------- -corePrepBind :: CloneEnv -> CoreBind -> UniqSM (CloneEnv, OrdList FloatingBind) +corePrepBind :: CloneEnv -> CoreBind -> UniqSM (CloneEnv, Floats) -- This one is used for *local* bindings corePrepBind env (NonRec bndr rhs) = etaExpandRhs bndr rhs `thenUs` \ rhs1 -> @@ -270,16 +306,16 @@ corePrepBind env (Rec pairs) = corePrepRecPairs NotTopLevel env pairs -------------------------------- corePrepRecPairs :: TopLevelFlag -> CloneEnv -> [(Id,CoreExpr)] -- Recursive bindings - -> UniqSM (CloneEnv, OrdList FloatingBind) + -> UniqSM (CloneEnv, Floats) -- Used for all recursive bindings, top level and otherwise corePrepRecPairs lvl env pairs = cloneBndrs env (map fst pairs) `thenUs` \ (env', bndrs') -> mapAndUnzipUs (corePrepRhs lvl Recursive env') pairs `thenUs` \ (floats_s, rhss') -> - returnUs (env', unitOL (FloatLet (Rec (flatten (concatOL floats_s) bndrs' rhss')))) + returnUs (env', unitFloat (FloatLet (Rec (flatten (concatFloats floats_s) bndrs' rhss')))) where -- Flatten all the floats, and the currrent -- group into a single giant Rec - flatten floats bndrs rhss = foldrOL get (bndrs `zip` rhss) floats + flatten (Floats _ floats) bndrs rhss = foldrOL get (bndrs `zip` rhss) floats get (FloatLet (NonRec b r)) prs2 = (b,r) : prs2 get (FloatLet (Rec prs1)) prs2 = prs1 ++ prs2 @@ -287,7 +323,7 @@ corePrepRecPairs lvl env pairs -------------------------------- corePrepRhs :: TopLevelFlag -> RecFlag -> CloneEnv -> (Id, CoreExpr) - -> UniqSM (OrdList FloatingBind, CoreExpr) + -> UniqSM (Floats, CoreExpr) -- Used for top-level bindings, and local recursive bindings corePrepRhs top_lvl is_rec env (bndr, rhs) = etaExpandRhs bndr rhs `thenUs` \ rhs' -> @@ -301,7 +337,7 @@ corePrepRhs top_lvl is_rec env (bndr, rhs) -- This is where we arrange that a non-trivial argument is let-bound corePrepArg :: CloneEnv -> CoreArg -> RhsDemand - -> UniqSM (OrdList FloatingBind, CoreArg) + -> UniqSM (Floats, CoreArg) corePrepArg env arg dem = corePrepExprFloat env arg `thenUs` \ (floats, arg') -> if exprIsTrivial arg' @@ -330,7 +366,7 @@ corePrepAnExpr env expr mkBinds floats expr -corePrepExprFloat :: CloneEnv -> CoreExpr -> UniqSM (OrdList FloatingBind, CoreExpr) +corePrepExprFloat :: CloneEnv -> CoreExpr -> UniqSM (Floats, CoreExpr) -- If -- e ===> (bs, e') -- then @@ -343,18 +379,18 @@ corePrepExprFloat env (Var v) = fiddleCCall v `thenUs` \ v1 -> let v2 = lookupVarEnv env v1 `orElse` v1 in maybeSaturate v2 (Var v2) 0 (idType v2) `thenUs` \ app -> - returnUs (nilOL, app) + returnUs (emptyFloats, app) corePrepExprFloat env expr@(Type _) - = returnUs (nilOL, expr) + = returnUs (emptyFloats, expr) corePrepExprFloat env expr@(Lit lit) - = returnUs (nilOL, expr) + = returnUs (emptyFloats, expr) corePrepExprFloat env (Let bind body) = corePrepBind env bind `thenUs` \ (env', new_binds) -> corePrepExprFloat env' body `thenUs` \ (floats, new_body) -> - returnUs (new_binds `appOL` floats, new_body) + returnUs (new_binds `appendFloats` floats, new_body) corePrepExprFloat env (Note n@(SCC _) expr) = corePrepAnExpr env expr `thenUs` \ expr1 -> @@ -368,7 +404,7 @@ corePrepExprFloat env (Note other_note expr) corePrepExprFloat env expr@(Lam _ _) = cloneBndrs env bndrs `thenUs` \ (env', bndrs') -> corePrepAnExpr env' body `thenUs` \ body' -> - returnUs (nilOL, mkLams bndrs' body') + returnUs (emptyFloats, mkLams bndrs' body') where (bndrs,body) = collectBinders expr @@ -377,7 +413,7 @@ corePrepExprFloat env (Case scrut bndr alts) deLamFloat scrut1 `thenUs` \ (floats2, scrut2) -> cloneBndr env bndr `thenUs` \ (env', bndr') -> mapUs (sat_alt env') alts `thenUs` \ alts' -> - returnUs (floats1 `appOL` floats2 , Case scrut2 bndr' alts') + returnUs (floats1 `appendFloats` floats2 , Case scrut2 bndr' alts') where sat_alt env (con, bs, rhs) = cloneBndrs env bs `thenUs` \ (env', bs') -> @@ -411,7 +447,7 @@ corePrepExprFloat env expr@(App _ _) (CoreExpr,Int), -- the head of the application, -- and no. of args it was applied to Type, -- type of the whole expr - OrdList FloatingBind, -- any floats we pulled out + Floats, -- any floats we pulled out [Demand]) -- remaining argument demands collect_args (App fun arg@(Type arg_ty)) depth @@ -428,12 +464,12 @@ corePrepExprFloat env expr@(App _ _) splitFunTy_maybe fun_ty in corePrepArg env arg (mkDemTy ss1 arg_ty) `thenUs` \ (fs, arg') -> - returnUs (App fun' arg', hd, res_ty, fs `appOL` floats, ss_rest) + returnUs (App fun' arg', hd, res_ty, fs `appendFloats` floats, ss_rest) collect_args (Var v) depth = fiddleCCall v `thenUs` \ v1 -> let v2 = lookupVarEnv env v1 `orElse` v1 in - returnUs (Var v2, (Var v2, depth), idType v2, nilOL, stricts) + returnUs (Var v2, (Var v2, depth), idType v2, emptyFloats, stricts) where stricts = case idNewStrictness v of StrictSig (DmdType _ demands _) @@ -495,9 +531,9 @@ maybeSaturate fn expr n_args ty floatRhs :: TopLevelFlag -> RecFlag -> Id - -> (OrdList FloatingBind, CoreExpr) -- Rhs: let binds in body - -> UniqSM (OrdList FloatingBind, -- Floats out of this bind - CoreExpr) -- Final Rhs + -> (Floats, CoreExpr) -- Rhs: let binds in body + -> UniqSM (Floats, -- Floats out of this bind + CoreExpr) -- Final Rhs floatRhs top_lvl is_rec bndr (floats, rhs) | isTopLevel top_lvl || exprIsValue rhs, -- Float to expose value or @@ -513,12 +549,12 @@ floatRhs top_lvl is_rec bndr (floats, rhs) | otherwise -- Don't float; the RHS isn't a value = mkBinds floats rhs `thenUs` \ rhs' -> - returnUs (nilOL, rhs') + returnUs (emptyFloats, rhs') -- mkLocalNonRec is used only for *nested*, *non-recursive* bindings -mkLocalNonRec :: Id -> RhsDemand -- Lhs: id with demand - -> OrdList FloatingBind -> CoreExpr -- Rhs: let binds in body - -> UniqSM (OrdList FloatingBind) +mkLocalNonRec :: Id -> RhsDemand -- Lhs: id with demand + -> Floats -> CoreExpr -- Rhs: let binds in body + -> UniqSM Floats mkLocalNonRec bndr dem floats rhs | isUnLiftedType (idType bndr) @@ -527,7 +563,7 @@ mkLocalNonRec bndr dem floats rhs let float = FloatCase bndr rhs (exprOkForSpeculation rhs) in - returnUs (floats `snocOL` float) + returnUs (addFloat floats float) | isStrict dem -- It's a strict let so we definitely float all the bindings @@ -537,18 +573,18 @@ mkLocalNonRec bndr dem floats rhs float | exprIsValue rhs = FloatLet (NonRec bndr rhs) | otherwise = FloatCase bndr rhs (exprOkForSpeculation rhs) in - returnUs (floats `snocOL` float) + returnUs (addFloat floats float) | otherwise = floatRhs NotTopLevel NonRecursive bndr (floats, rhs) `thenUs` \ (floats', rhs') -> - returnUs (floats' `snocOL` FloatLet (NonRec bndr rhs')) + returnUs (addFloat floats' (FloatLet (NonRec bndr rhs'))) where bndr_ty = idType bndr -mkBinds :: OrdList FloatingBind -> CoreExpr -> UniqSM CoreExpr -mkBinds binds body +mkBinds :: Floats -> CoreExpr -> UniqSM CoreExpr +mkBinds (Floats _ binds) body | isNilOL binds = returnUs body | otherwise = deLam body `thenUs` \ body' -> returnUs (foldrOL mk_bind body' binds) @@ -606,7 +642,7 @@ deLam expr = mkBinds floats expr -deLamFloat :: CoreExpr -> UniqSM (OrdList FloatingBind, CoreExpr) +deLamFloat :: CoreExpr -> UniqSM (Floats, CoreExpr) -- Remove top level lambdas by let-bindinig deLamFloat (Note n expr) @@ -616,12 +652,12 @@ deLamFloat (Note n expr) returnUs (floats, Note n expr') deLamFloat expr - | null bndrs = returnUs (nilOL, expr) + | null bndrs = returnUs (emptyFloats, expr) | otherwise = case tryEta bndrs body of - Just no_lam_result -> returnUs (nilOL, no_lam_result) + Just no_lam_result -> returnUs (emptyFloats, no_lam_result) Nothing -> newVar (exprType expr) `thenUs` \ fn -> - returnUs (unitOL (FloatLet (NonRec fn expr)), + returnUs (unitFloat (FloatLet (NonRec fn expr)), Var fn) where (bndrs,body) = collectBinders expr |