X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FcoreSyn%2FCoreUnfold.lhs;h=d1b9fa04129de2a724ef9eb90f68a4f01a907a05;hb=b6264a6b8a8e22e24464da39ca0a3a0176d91f4e;hp=7ab0e230e39da56e700a277bde0f581108b6e4e2;hpb=4c9154facefe185dcbb99e2bb1cfe118f02f8bd3;p=ghc-hetmet.git diff --git a/compiler/coreSyn/CoreUnfold.lhs b/compiler/coreSyn/CoreUnfold.lhs index 7ab0e23..d1b9fa0 100644 --- a/compiler/coreSyn/CoreUnfold.lhs +++ b/compiler/coreSyn/CoreUnfold.lhs @@ -26,7 +26,7 @@ module CoreUnfold ( interestingArg, ArgSummary(..), - couldBeSmallEnoughToInline, + couldBeSmallEnoughToInline, inlineBoringOk, certainlyWillInline, smallEnoughToInline, callSiteInline, CallCtxt(..), @@ -41,8 +41,8 @@ import StaticFlags import DynFlags import CoreSyn import PprCore () -- Instances -import TcType ( tcSplitSigmaTy, tcSplitDFunHead ) -import OccurAnal +import TcType ( tcSplitDFunTy ) +import OccurAnal ( occurAnalyseExpr ) import CoreSubst hiding( substTy ) import CoreFVs ( exprFreeVars ) import CoreArity ( manifestArity, exprBotStrictness_maybe ) @@ -54,8 +54,7 @@ import Literal import PrimOp import IdInfo import BasicTypes ( Arity ) -import TcType ( tcSplitDFunTy ) -import Type +import Type import Coercion import PrelNames import VarEnv ( mkInScopeSet ) @@ -91,15 +90,12 @@ mkImplicitUnfolding expr = mkTopUnfolding False (simpleOptExpr expr) mkSimpleUnfolding :: CoreExpr -> Unfolding mkSimpleUnfolding = mkUnfolding InlineRhs False False -mkDFunUnfolding :: Type -> [CoreExpr] -> Unfolding +mkDFunUnfolding :: Type -> [DFunArg CoreExpr] -> Unfolding mkDFunUnfolding dfun_ty ops = DFunUnfolding dfun_nargs data_con ops where - (tvs, theta, head_ty) = tcSplitSigmaTy dfun_ty - -- NB: tcSplitSigmaTy: do not look through a newtype - -- when the dictionary type is a newtype - (cls, _) = tcSplitDFunHead head_ty - dfun_nargs = length tvs + length theta + (tvs, n_theta, cls, _) = tcSplitDFunTy dfun_ty + dfun_nargs = length tvs + n_theta data_con = classDataCon cls mkWwInlineRule :: Id -> CoreExpr -> Arity -> Unfolding @@ -126,12 +122,7 @@ mkInlineUnfolding mb_arity expr Nothing -> (unSaturatedOk, manifestArity expr') Just ar -> (needSaturated, ar) - boring_ok = case calcUnfoldingGuidance True -- Treat as cheap - False -- But not bottoming - (arity+1) expr' of - (_, UnfWhen _ boring_ok) -> boring_ok - _other -> boringCxtNotOk - -- See Note [INLINE for small functions] + boring_ok = inlineBoringOk expr' mkInlinableUnfolding :: CoreExpr -> Unfolding mkInlinableUnfolding expr @@ -162,6 +153,10 @@ mkUnfolding :: UnfoldingSource -> Bool -> Bool -> CoreExpr -> Unfolding -- Calculates unfolding guidance -- Occurrence-analyses the expression before capturing it mkUnfolding src top_lvl is_bottoming expr + | top_lvl && is_bottoming + , not (exprIsTrivial expr) + = NoUnfolding -- See Note [Do not inline top-level bottoming functions] + | otherwise = CoreUnfolding { uf_tmpl = occurAnalyseExpr expr, uf_src = src, uf_arity = arity, @@ -173,7 +168,7 @@ mkUnfolding src top_lvl is_bottoming expr uf_guidance = guidance } where is_cheap = exprIsCheap expr - (arity, guidance) = calcUnfoldingGuidance is_cheap (top_lvl && is_bottoming) + (arity, guidance) = calcUnfoldingGuidance is_cheap opt_UF_CreationThreshold expr -- Sometimes during simplification, there's a large let-bound thing -- which has been substituted, and so is now dead; so 'expr' contains @@ -193,15 +188,35 @@ mkUnfolding src top_lvl is_bottoming expr %************************************************************************ \begin{code} +inlineBoringOk :: CoreExpr -> Bool +-- See Note [INLINE for small functions] +-- True => the result of inlining the expression is +-- no bigger than the expression itself +-- eg (\x y -> f y x) +-- This is a quick and dirty version. It doesn't attempt +-- to deal with (\x y z -> x (y z)) +-- The really important one is (x `cast` c) +inlineBoringOk e + = go 0 e + where + go :: Int -> CoreExpr -> Bool + go credit (Lam x e) | isId x = go (credit+1) e + | otherwise = go credit e + go credit (App f (Type {})) = go credit f + go credit (App f a) | credit > 0 + , exprIsTrivial a = go (credit-1) f + go credit (Note _ e) = go credit e + go credit (Cast e _) = go credit e + go _ (Var {}) = boringCxtOk + go _ _ = boringCxtNotOk + calcUnfoldingGuidance :: Bool -- True <=> the rhs is cheap, or we want to treat it -- as cheap (INLINE things) - -> Bool -- True <=> this is a top-level unfolding for a - -- diverging function; don't inline this -> Int -- Bomb out if size gets bigger than this -> CoreExpr -- Expression to look at -> (Arity, UnfoldingGuidance) -calcUnfoldingGuidance expr_is_cheap top_bot bOMB_OUT_SIZE expr +calcUnfoldingGuidance expr_is_cheap bOMB_OUT_SIZE expr = case collectBinders expr of { (bndrs, body) -> let val_bndrs = filter isId bndrs @@ -214,9 +229,6 @@ calcUnfoldingGuidance expr_is_cheap top_bot bOMB_OUT_SIZE expr | uncondInline n_val_bndrs (iBox size) , expr_is_cheap -> UnfWhen unSaturatedOk boringCxtOk -- Note [INLINE for small functions] - | top_bot -- See Note [Do not inline top-level bottoming functions] - -> UnfNever - | otherwise -> UnfIfGoodArgs { ug_args = map (discount cased_bndrs) val_bndrs , ug_size = iBox size @@ -730,13 +742,12 @@ StrictAnal.addStrictnessInfoToTopId \begin{code} callSiteInline :: DynFlags -> Id -- The Id - -> Unfolding -- Its unfolding (if active) + -> Bool -- True <=> unfolding is active -> Bool -- True if there are are no arguments at all (incl type args) -> [ArgSummary] -- One for each value arg; True if it is interesting -> CallCtxt -- True <=> continuation is interesting -> Maybe CoreExpr -- Unfolding, if any - instance Outputable ArgSummary where ppr TrivArg = ptext (sLit "TrivArg") ppr NonTrivArg = ptext (sLit "NonTrivArg") @@ -765,79 +776,92 @@ instance Outputable CallCtxt where ppr CaseCtxt = ptext (sLit "CaseCtxt") ppr ValAppCtxt = ptext (sLit "ValAppCtxt") -callSiteInline dflags id unfolding lone_variable arg_infos cont_info - = case unfolding of { - NoUnfolding -> Nothing ; - OtherCon _ -> Nothing ; - DFunUnfolding {} -> Nothing ; -- Never unfold a DFun - CoreUnfolding { uf_tmpl = unf_template, uf_is_top = is_top, - uf_is_cheap = is_cheap, uf_arity = uf_arity, uf_guidance = guidance } -> +callSiteInline dflags id active_unfolding lone_variable arg_infos cont_info + = case idUnfolding id of + -- idUnfolding checks for loop-breakers, returning NoUnfolding + -- Things with an INLINE pragma may have an unfolding *and* + -- be a loop breaker (maybe the knot is not yet untied) + CoreUnfolding { uf_tmpl = unf_template, uf_is_top = is_top + , uf_is_cheap = is_cheap, uf_arity = uf_arity + , uf_guidance = guidance, uf_expandable = is_exp } + | active_unfolding -> tryUnfolding dflags id lone_variable + arg_infos cont_info unf_template is_top + is_cheap is_exp uf_arity guidance + | otherwise -> Nothing + NoUnfolding -> Nothing + OtherCon {} -> Nothing + DFunUnfolding {} -> Nothing -- Never unfold a DFun + +tryUnfolding :: DynFlags -> Id -> Bool -> [ArgSummary] -> CallCtxt + -> CoreExpr -> Bool -> Bool -> Bool -> Arity -> UnfoldingGuidance + -> Maybe CoreExpr +tryUnfolding dflags id lone_variable + arg_infos cont_info unf_template is_top + is_cheap is_exp uf_arity guidance -- uf_arity will typically be equal to (idArity id), -- but may be less for InlineRules - let - n_val_args = length arg_infos - saturated = n_val_args >= uf_arity - - result | yes_or_no = Just unf_template - | otherwise = Nothing - - interesting_args = any nonTriv arg_infos - -- NB: (any nonTriv arg_infos) looks at the - -- over-saturated args too which is "wrong"; - -- but if over-saturated we inline anyway. - - -- some_benefit is used when the RHS is small enough - -- and the call has enough (or too many) value - -- arguments (ie n_val_args >= arity). But there must - -- be *something* interesting about some argument, or the - -- result context, to make it worth inlining - some_benefit - | not saturated = interesting_args -- Under-saturated - -- Note [Unsaturated applications] - | n_val_args > uf_arity = True -- Over-saturated - | otherwise = interesting_args -- Saturated - || interesting_saturated_call - - interesting_saturated_call - = case cont_info of - BoringCtxt -> not is_top && uf_arity > 0 -- Note [Nested functions] - CaseCtxt -> not (lone_variable && is_cheap) -- Note [Lone variables] - ArgCtxt {} -> uf_arity > 0 -- Note [Inlining in ArgCtxt] - ValAppCtxt -> True -- Note [Cast then apply] - - (yes_or_no, extra_doc) - = case guidance of - UnfNever -> (False, empty) - - UnfWhen unsat_ok boring_ok - -> (enough_args && (boring_ok || some_benefit), empty ) - where -- See Note [INLINE for small functions] - enough_args = saturated || (unsat_ok && n_val_args > 0) - - UnfIfGoodArgs { ug_args = arg_discounts, ug_res = res_discount, ug_size = size } - -> ( is_cheap && some_benefit && small_enough - , (text "discounted size =" <+> int discounted_size) ) - where - discounted_size = size - discount - small_enough = discounted_size <= opt_UF_UseThreshold - discount = computeDiscount uf_arity arg_discounts - res_discount arg_infos cont_info - - in - if (dopt Opt_D_dump_inlinings dflags && dopt Opt_D_verbose_core2core dflags) then - pprTrace ("Considering inlining: " ++ showSDoc (ppr id)) + | dopt Opt_D_dump_inlinings dflags && dopt Opt_D_verbose_core2core dflags + = pprTrace ("Considering inlining: " ++ showSDoc (ppr id)) (vcat [text "arg infos" <+> ppr arg_infos, text "uf arity" <+> ppr uf_arity, text "interesting continuation" <+> ppr cont_info, text "some_benefit" <+> ppr some_benefit, + text "is exp:" <+> ppr is_exp, text "is cheap:" <+> ppr is_cheap, text "guidance" <+> ppr guidance, extra_doc, text "ANSWER =" <+> if yes_or_no then text "YES" else text "NO"]) - result - else - result - } + result + | otherwise = result + + where + n_val_args = length arg_infos + saturated = n_val_args >= uf_arity + + result | yes_or_no = Just unf_template + | otherwise = Nothing + + interesting_args = any nonTriv arg_infos + -- NB: (any nonTriv arg_infos) looks at the + -- over-saturated args too which is "wrong"; + -- but if over-saturated we inline anyway. + + -- some_benefit is used when the RHS is small enough + -- and the call has enough (or too many) value + -- arguments (ie n_val_args >= arity). But there must + -- be *something* interesting about some argument, or the + -- result context, to make it worth inlining + some_benefit + | not saturated = interesting_args -- Under-saturated + -- Note [Unsaturated applications] + | n_val_args > uf_arity = True -- Over-saturated + | otherwise = interesting_args -- Saturated + || interesting_saturated_call + + interesting_saturated_call + = case cont_info of + BoringCtxt -> not is_top && uf_arity > 0 -- Note [Nested functions] + CaseCtxt -> not (lone_variable && is_cheap) -- Note [Lone variables] + ArgCtxt {} -> uf_arity > 0 -- Note [Inlining in ArgCtxt] + ValAppCtxt -> True -- Note [Cast then apply] + + (yes_or_no, extra_doc) + = case guidance of + UnfNever -> (False, empty) + + UnfWhen unsat_ok boring_ok + -> (enough_args && (boring_ok || some_benefit), empty ) + where -- See Note [INLINE for small functions] + enough_args = saturated || (unsat_ok && n_val_args > 0) + + UnfIfGoodArgs { ug_args = arg_discounts, ug_res = res_discount, ug_size = size } + -> ( is_cheap && some_benefit && small_enough + , (text "discounted size =" <+> int discounted_size) ) + where + discounted_size = size - discount + small_enough = discounted_size <= opt_UF_UseThreshold + discount = computeDiscount uf_arity arg_discounts + res_discount arg_infos cont_info \end{code} Note [RHS of lets] @@ -871,7 +895,7 @@ But the defn of GHC.Classes.$dmmin is: {- Arity: 3, HasNoCafRefs, Strictness: SLL, Unfolding: (\ @ a $dOrd :: GHC.Classes.Ord a x :: a y :: a -> case @ a GHC.Classes.<= @ a $dOrd x y of wild { - GHC.Bool.False -> y GHC.Bool.True -> x }) -} + GHC.Types.False -> y GHC.Types.True -> x }) -} We *really* want to inline $dmmin, even though it has arity 3, in order to unravel the recursion. @@ -1163,13 +1187,14 @@ However e might not *look* as if -- where t1..tk are the *universally-qantified* type args of 'dc' exprIsConApp_maybe :: IdUnfoldingFun -> CoreExpr -> Maybe (DataCon, [Type], [CoreExpr]) -exprIsConApp_maybe id_unf (Note _ expr) +exprIsConApp_maybe id_unf (Note note expr) + | notSccNote note = exprIsConApp_maybe id_unf expr - -- We ignore all notes. For example, + -- We ignore all notes except SCCs. For example, -- case _scc_ "foo" (C a b) of -- C a b -> e - -- should be optimised away, but it will be only if we look - -- through the SCC note. + -- should not be optimised away, because we'll lose the + -- entry count on 'foo'; see Trac #4414 exprIsConApp_maybe id_unf (Cast expr co) = -- Here we do the KPush reduction rule as described in the FC paper @@ -1257,10 +1282,12 @@ exprIsConApp_maybe id_unf expr , let sat = length args == dfun_nargs -- See Note [DFun arity check] in if sat then True else pprTrace "Unsaturated dfun" (ppr fun <+> int dfun_nargs $$ ppr args) False - , let (dfun_tvs, _cls, dfun_res_tys) = tcSplitDFunTy (idType fun) - subst = zipOpenTvSubst dfun_tvs (stripTypeArgs (takeList dfun_tvs args)) - = Just (con, substTys subst dfun_res_tys, - [mkApps op args | op <- ops]) + , let (dfun_tvs, _n_theta, _cls, dfun_res_tys) = tcSplitDFunTy (idType fun) + subst = zipOpenTvSubst dfun_tvs (stripTypeArgs (takeList dfun_tvs args)) + mk_arg (DFunConstArg e) = e + mk_arg (DFunLamArg i) = args !! i + mk_arg (DFunPolyArg e) = mkApps e args + = Just (con, substTys subst dfun_res_tys, map mk_arg ops) -- Look through unfoldings, but only cheap ones, because -- we are effectively duplicating the unfolding