X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FcoreSyn%2FCoreUnfold.lhs;h=b6706c14cd71318682b3e8dfaee2bdb0a3b300f4;hb=66579ff945831c5fc9a17c58c722ff01f2268d76;hp=d8e0cb054de73d97650316063bba8fa0e3c46940;hpb=d8c0a66c1e5d357eae882963ee6834f485868d22;p=ghc-hetmet.git diff --git a/compiler/coreSyn/CoreUnfold.lhs b/compiler/coreSyn/CoreUnfold.lhs index d8e0cb0..b6706c1 100644 --- a/compiler/coreSyn/CoreUnfold.lhs +++ b/compiler/coreSyn/CoreUnfold.lhs @@ -15,17 +15,11 @@ literal''). In the corner of a @CoreUnfolding@ unfolding, you will find, unsurprisingly, a Core expression. \begin{code} -{-# OPTIONS -w #-} --- The above warning supression flag is a temporary kludge. --- While working on this module you are encouraged to remove it and fix --- any warnings in the module. See --- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings --- for details - module CoreUnfold ( Unfolding, UnfoldingGuidance, -- Abstract types - noUnfolding, mkTopUnfolding, mkUnfolding, mkCompulsoryUnfolding, seqUnfolding, + noUnfolding, mkTopUnfolding, mkImplicitUnfolding, mkUnfolding, + mkCompulsoryUnfolding, seqUnfolding, evaldUnfolding, mkOtherCon, otherCons, unfoldingTemplate, maybeUnfoldingTemplate, isEvaldUnfolding, isValueUnfolding, isCheapUnfolding, isCompulsoryUnfolding, @@ -34,27 +28,28 @@ module CoreUnfold ( couldBeSmallEnoughToInline, certainlyWillInline, smallEnoughToInline, - callSiteInline, CallContInfo(..) + callSiteInline, CallCtxt(..) ) where -#include "HsVersions.h" - import StaticFlags import DynFlags import CoreSyn import PprCore () -- Instances import OccurAnal +import CoreSubst ( Subst, emptySubst, substTy, extendIdSubst, extendTvSubst + , lookupIdSubst, substBndr, substBndrs, substRecBndrs ) import CoreUtils import Id import DataCon import Literal import PrimOp import IdInfo -import Type +import Type hiding( substTy, extendTvSubst ) import PrelNames import Bag import FastTypes +import FastString import Outputable \end{code} @@ -67,8 +62,19 @@ import Outputable %************************************************************************ \begin{code} +mkTopUnfolding :: CoreExpr -> Unfolding mkTopUnfolding expr = mkUnfolding True {- Top level -} expr +mkImplicitUnfolding :: CoreExpr -> Unfolding +-- For implicit Ids, do a tiny bit of optimising first +mkImplicitUnfolding expr + = CoreUnfolding (simpleOptExpr emptySubst expr) + True + (exprIsHNF expr) + (exprIsCheap expr) + (calcUnfoldingGuidance opt_UF_CreationThreshold expr) + +mkUnfolding :: Bool -> CoreExpr -> Unfolding mkUnfolding top_lvl expr = CoreUnfolding (occurAnalyseExpr expr) top_lvl @@ -90,13 +96,14 @@ mkUnfolding top_lvl expr -- it gets fixed up next round instance Outputable Unfolding where - ppr NoUnfolding = ptext SLIT("No unfolding") - ppr (OtherCon cs) = ptext SLIT("OtherCon") <+> ppr cs - ppr (CompulsoryUnfolding e) = ptext SLIT("Compulsory") <+> ppr e + ppr NoUnfolding = ptext (sLit "No unfolding") + ppr (OtherCon cs) = ptext (sLit "OtherCon") <+> ppr cs + ppr (CompulsoryUnfolding e) = ptext (sLit "Compulsory") <+> ppr e ppr (CoreUnfolding e top hnf cheap g) - = ptext SLIT("Unf") <+> sep [ppr top <+> ppr hnf <+> ppr cheap <+> ppr g, + = ptext (sLit "Unf") <+> sep [ppr top <+> ppr hnf <+> ppr cheap <+> ppr g, ppr e] +mkCompulsoryUnfolding :: CoreExpr -> Unfolding mkCompulsoryUnfolding expr -- Used for things that absolutely must be unfolded = CompulsoryUnfolding (occurAnalyseExpr expr) \end{code} @@ -110,9 +117,9 @@ mkCompulsoryUnfolding expr -- Used for things that absolutely must be unfolded \begin{code} instance Outputable UnfoldingGuidance where - ppr UnfoldNever = ptext SLIT("NEVER") + ppr UnfoldNever = ptext (sLit "NEVER") ppr (UnfoldIfGoodArgs v cs size discount) - = hsep [ ptext SLIT("IF_ARGS"), int v, + = hsep [ ptext (sLit "IF_ARGS"), int v, brackets (hsep (map int cs)), int size, int discount ] @@ -174,7 +181,7 @@ calcUnfoldingGuidance bOMB_OUT_SIZE expr -- We want to say "2 value binders". Why? So that -- we take account of information given for the arguments - go inline rev_vbs (Note InlineMe e) = go True rev_vbs e + go _ rev_vbs (Note InlineMe e) = go True rev_vbs e go inline rev_vbs (Lam b e) | isId b = go inline (b:rev_vbs) e | otherwise = go inline rev_vbs e go inline rev_vbs e = (inline, reverse rev_vbs, e) @@ -190,10 +197,10 @@ sizeExpr :: FastInt -- Bomb out if it gets bigger than this sizeExpr bOMB_OUT_SIZE top_args expr = size_up expr where - size_up (Type t) = sizeZero -- Types cost nothing - size_up (Var v) = sizeOne + size_up (Type _) = sizeZero -- Types cost nothing + size_up (Var _) = sizeOne - size_up (Note InlineMe body) = sizeOne -- Inline notes make it look very small + size_up (Note InlineMe _) = sizeOne -- Inline notes make it look very small -- This can be important. If you have an instance decl like this: -- instance Foo a => Foo [a] where -- {-# INLINE op1, op2 #-} @@ -201,11 +208,11 @@ sizeExpr bOMB_OUT_SIZE top_args expr -- op2 = ... -- then we'll get a dfun which is a pair of two INLINE lambdas - size_up (Note _ body) = size_up body -- Other notes cost nothing + size_up (Note _ body) = size_up body -- Other notes cost nothing - size_up (Cast e _) = size_up e + size_up (Cast e _) = size_up e - size_up (App fun (Type t)) = size_up fun + size_up (App fun (Type _)) = size_up fun size_up (App fun arg) = size_up_app fun [arg] size_up (Lit lit) = sizeN (litSize lit) @@ -267,8 +274,8 @@ sizeExpr bOMB_OUT_SIZE top_args expr -- alts_size tries to compute a good discount for -- the case when we are scrutinising an argument variable - alts_size (SizeIs tot tot_disc tot_scrut) -- Size of all alternatives - (SizeIs max max_disc max_scrut) -- Size of biggest alternative + alts_size (SizeIs tot _tot_disc _tot_scrut) -- Size of all alternatives + (SizeIs max max_disc max_scrut) -- Size of biggest alternative = SizeIs tot (unitBag (v, iBox (_ILIT(1) +# tot -# max)) `unionBags` max_disc) max_scrut -- If the variable is known, we produce a discount that -- will take us back to 'max', the size of rh largest alternative @@ -305,7 +312,7 @@ sizeExpr bOMB_OUT_SIZE top_args expr = case globalIdDetails fun of DataConWorkId dc -> conSizeN dc (valArgCount args) - FCallId fc -> sizeN opt_UF_DearOp + FCallId _ -> sizeN opt_UF_DearOp PrimOpId op -> primOpSize op (valArgCount args) -- foldr addSize (primOpSize op) (map arg_discount args) -- At one time I tried giving an arg-discount if a primop @@ -315,7 +322,7 @@ sizeExpr bOMB_OUT_SIZE top_args expr -- if we know nothing about it. And just having it in a primop -- doesn't help at all if we don't know something more. - other -> fun_discount fun `addSizeN` + _ -> fun_discount fun `addSizeN` (1 + length (filter (not . exprIsTrivial) args)) -- The 1+ is for the function itself -- Add 1 for each non-trivial arg; @@ -325,17 +332,17 @@ sizeExpr bOMB_OUT_SIZE top_args expr -- We should really only count for non-prim-typed args in the -- general case, but that seems too much like hard work - size_up_fun other args = size_up other + size_up_fun other _ = size_up other ------------ - size_up_alt (con, bndrs, rhs) = size_up rhs + size_up_alt (_con, _bndrs, rhs) = size_up rhs -- Don't charge for args, so that wrappers look cheap -- (See comments about wrappers with Case) ------------ -- We want to record if we're case'ing, or applying, an argument fun_discount v | v `elem` top_args = SizeIs (_ILIT(0)) (unitBag (v, opt_UF_FunAppDiscount)) (_ILIT(0)) - fun_discount other = sizeZero + fun_discount _ = sizeZero ------------ -- These addSize things have to be here because @@ -364,14 +371,20 @@ data ExprSize = TooBig -- tup = (a_1, ..., a_99) -- x = case tup of ... -- +mkSizeIs :: FastInt -> FastInt -> Bag (Id, Int) -> FastInt -> ExprSize mkSizeIs max n xs d | (n -# d) ># max = TooBig | otherwise = SizeIs n xs d +maxSize :: ExprSize -> ExprSize -> ExprSize maxSize TooBig _ = TooBig maxSize _ TooBig = TooBig maxSize s1@(SizeIs n1 _ _) s2@(SizeIs n2 _ _) | n1 ># n2 = s1 | otherwise = s2 +sizeZero, sizeOne :: ExprSize +sizeN :: Int -> ExprSize +conSizeN :: DataCon ->Int -> ExprSize + sizeZero = SizeIs (_ILIT(0)) emptyBag (_ILIT(0)) sizeOne = SizeIs (_ILIT(1)) emptyBag (_ILIT(0)) sizeN n = SizeIs (iUnbox n) emptyBag (_ILIT(0)) @@ -389,6 +402,7 @@ conSizeN dc n -- f x y z = case op# x y z of { s -> (# s, () #) } -- and f wasn't getting inlined +primOpSize :: PrimOp -> Int -> ExprSize primOpSize op n_args | not (primOpIsDupable op) = sizeN opt_UF_DearOp | not (primOpOutOfLine op) = sizeN (2 - n_args) @@ -403,6 +417,7 @@ primOpSize op n_args -- and there's a good chance it'll get inlined back into C's RHS. Urgh! | otherwise = sizeOne +buildSize :: ExprSize buildSize = SizeIs (_ILIT(-2)) emptyBag (_ILIT(4)) -- We really want to inline applications of build -- build t (\cn -> e) should cost only the cost of e (because build will be inlined later) @@ -411,16 +426,19 @@ buildSize = SizeIs (_ILIT(-2)) emptyBag (_ILIT(4)) -- build is saturated (it usually is). The "-2" discounts for the \c n, -- The "4" is rather arbitrary. +augmentSize :: ExprSize augmentSize = SizeIs (_ILIT(-2)) emptyBag (_ILIT(4)) -- Ditto (augment t (\cn -> e) ys) should cost only the cost of -- e plus ys. The -2 accounts for the \cn - -nukeScrutDiscount (SizeIs n vs d) = SizeIs n vs (_ILIT(0)) -nukeScrutDiscount TooBig = TooBig + +nukeScrutDiscount :: ExprSize -> ExprSize +nukeScrutDiscount (SizeIs n vs _) = SizeIs n vs (_ILIT(0)) +nukeScrutDiscount TooBig = TooBig -- When we return a lambda, give a discount if it's used (applied) -lamScrutDiscount (SizeIs n vs d) = case opt_UF_FunAppDiscount of { d -> SizeIs n vs (iUnbox d) } -lamScrutDiscount TooBig = TooBig +lamScrutDiscount :: ExprSize -> ExprSize +lamScrutDiscount (SizeIs n vs _) = case opt_UF_FunAppDiscount of { d -> SizeIs n vs (iUnbox d) } +lamScrutDiscount TooBig = TooBig \end{code} @@ -461,20 +479,20 @@ Just the same as smallEnoughToInline, except that it has no actual arguments. \begin{code} couldBeSmallEnoughToInline :: Int -> CoreExpr -> Bool couldBeSmallEnoughToInline threshold rhs = case calcUnfoldingGuidance threshold rhs of - UnfoldNever -> False - other -> True + UnfoldNever -> False + _ -> True certainlyWillInline :: Unfolding -> Bool -- Sees if the unfolding is pretty certain to inline certainlyWillInline (CoreUnfolding _ _ _ is_cheap (UnfoldIfGoodArgs n_vals _ size _)) = is_cheap && size - (n_vals +1) <= opt_UF_UseThreshold -certainlyWillInline other +certainlyWillInline _ = False smallEnoughToInline :: Unfolding -> Bool smallEnoughToInline (CoreUnfolding _ _ _ _ (UnfoldIfGoodArgs _ _ size _)) = size <= opt_UF_UseThreshold -smallEnoughToInline other +smallEnoughToInline _ = False \end{code} @@ -496,7 +514,7 @@ If the thing is in WHNF, there's no danger of duplicating work, so we can inline if it occurs once, or is small NOTE: we don't want to inline top-level functions that always diverge. -It just makes the code bigger. It turns out that the convenient way to prevent +It just makes the code bigger. Tt turns out that the convenient way to prevent them inlining is to give them a NOINLINE pragma, which we do in StrictAnal.addStrictnessInfoToTopId @@ -506,24 +524,30 @@ callSiteInline :: DynFlags -> Id -- The Id -> Bool -- True if there are are no arguments at all (incl type args) -> [Bool] -- One for each value arg; True if it is interesting - -> CallContInfo -- True <=> continuation is interesting + -> CallCtxt -- True <=> continuation is interesting -> Maybe CoreExpr -- Unfolding, if any -data CallContInfo = BoringCont - | InterestingCont -- Somewhat interesting - | CaseCont -- Very interesting; the argument of a case - -- that decomposes its scrutinee +data CallCtxt = BoringCtxt + + | ArgCtxt Bool -- We're somewhere in the RHS of function with rules + -- => be keener to inline + Int -- We *are* the argument of a function with this arg discount + -- => be keener to inline + -- INVARIANT: ArgCtxt False 0 ==> BoringCtxt + + | CaseCtxt -- We're the scrutinee of a case + -- that decomposes its scrutinee -instance Outputable CallContInfo where - ppr BoringCont = ptext SLIT("BoringCont") - ppr InterestingCont = ptext SLIT("InterestingCont") - ppr CaseCont = ptext SLIT("CaseCont") +instance Outputable CallCtxt where + ppr BoringCtxt = ptext (sLit "BoringCtxt") + ppr (ArgCtxt _ _) = ptext (sLit "ArgCtxt") + ppr CaseCtxt = ptext (sLit "CaseCtxt") callSiteInline dflags active_inline id lone_variable arg_infos cont_info = case idUnfolding id of { NoUnfolding -> Nothing ; - OtherCon cs -> Nothing ; + OtherCon _ -> Nothing ; CompulsoryUnfolding unf_template -> Just unf_template ; -- CompulsoryUnfolding => there is no top-level binding @@ -562,10 +586,13 @@ callSiteInline dflags active_inline id lone_variable arg_infos cont_info -> True | otherwise - -> some_benefit && small_enough + -> some_benefit && small_enough && inline_enough_args + where enough_args = n_val_args >= n_vals_wanted - -- Note [Enough args] + inline_enough_args = + not (dopt Opt_InlineIfEnoughArgs dflags) || enough_args + some_benefit = or arg_infos || really_interesting_cont -- There must be something interesting @@ -581,17 +608,18 @@ callSiteInline dflags active_inline id lone_variable arg_infos cont_info interesting_saturated_call = case cont_info of - BoringCont -> not is_top && n_vals_wanted > 0 -- Note [Nested functions] - CaseCont -> not lone_variable || not is_value -- Note [Lone variables] - InterestingCont -> True -- Something else interesting about continuation + BoringCtxt -> not is_top && n_vals_wanted > 0 -- Note [Nested functions] + CaseCtxt -> not lone_variable || not is_value -- Note [Lone variables] + ArgCtxt {} -> n_vals_wanted > 0 + -- See Note [Inlining in ArgCtxt] small_enough = (size - discount) <= opt_UF_UseThreshold discount = computeDiscount n_vals_wanted arg_discounts res_discount' arg_infos res_discount' = case cont_info of - BoringCont -> 0 - CaseCont -> res_discount - InterestingCont -> 4 `min` res_discount + BoringCtxt -> 0 + CaseCtxt -> res_discount + ArgCtxt _ _ -> 4 `min` res_discount -- res_discount can be very large when a function returns -- construtors; but we only want to invoke that large discount -- when there's a case continuation. @@ -604,8 +632,7 @@ callSiteInline dflags active_inline id lone_variable arg_infos cont_info pprTrace "Considering inlining" (ppr id <+> vcat [text "active:" <+> ppr active_inline, text "arg infos" <+> ppr arg_infos, - text "interesting continuation" <+> ppr cont_info <+> - ppr n_val_args, + text "interesting continuation" <+> ppr cont_info, text "is value:" <+> ppr is_value, text "is cheap:" <+> ppr is_cheap, text "guidance" <+> ppr guidance, @@ -616,16 +643,6 @@ callSiteInline dflags active_inline id lone_variable arg_infos cont_info } \end{code} -Note [Enough args] -~~~~~~~~~~~~~~~~~~ -At one stage we considered only inlining a function that has enough -arguments to saturate its arity. But we can lose from this. For -example (f . g) might not be a saturated application of (.), but -nevertheless f and g might usefully optimise with each other if we -inlined (.) and f and g. - -Current story (Jan08): inline even if not saturated. - Note [Nested functions] ~~~~~~~~~~~~~~~~~~~~~~~ If a function has a nested defn we also record some-benefit, on the @@ -638,8 +655,21 @@ branches. Then inlining it doesn't increase allocation, but it does increase the chance that the constructor won't be allocated at all in the branches that don't use it. +Note [Inlining in ArgCtxt] +~~~~~~~~~~~~~~~~~~~~~~~~~~ +The condition (n_vals_wanted > 0) here is very important, because otherwise +we end up inlining top-level stuff into useless places; eg + x = I# 3# + f = \y. g x +This can make a very big difference: it adds 16% to nofib 'integer' allocs, +and 20% to 'power'. + +At one stage I replaced this condition by 'True' (leading to the above +slow-down). The motivation was test eyeball/inline1.hs; but that seems +to work ok now. + Note [Lone variables] -~~~~~~~~~~~~~~~~~~~~~ +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The "lone-variable" case is important. I spent ages messing about with unsatisfactory varaints, but this is nice. The idea is that if a variable appears all alone @@ -718,3 +748,75 @@ computeDiscount n_vals_wanted arg_discounts result_discount arg_infos mk_arg_discount discount is_evald | is_evald = discount | otherwise = 0 \end{code} + +%************************************************************************ +%* * + The Very Simple Optimiser +%* * +%************************************************************************ + + +\begin{code} +simpleOptExpr :: Subst -> CoreExpr -> CoreExpr +-- Return an occur-analysed and slightly optimised expression +-- The optimisation is very straightforward: just +-- inline non-recursive bindings that are used only once, +-- or wheere the RHS is trivial + +simpleOptExpr subst expr + = go subst (occurAnalyseExpr expr) + where + go subst (Var v) = lookupIdSubst subst v + go subst (App e1 e2) = App (go subst e1) (go subst e2) + go subst (Type ty) = Type (substTy subst ty) + go _ (Lit lit) = Lit lit + go subst (Note note e) = Note note (go subst e) + go subst (Cast e co) = Cast (go subst e) (substTy subst co) + go subst (Let bind body) = go_bind subst bind body + go subst (Lam bndr body) = Lam bndr' (go subst' body) + where + (subst', bndr') = substBndr subst bndr + + go subst (Case e b ty as) = Case (go subst e) b' + (substTy subst ty) + (map (go_alt subst') as) + where + (subst', b') = substBndr subst b + + + ---------------------- + go_alt subst (con, bndrs, rhs) = (con, bndrs', go subst' rhs) + where + (subst', bndrs') = substBndrs subst bndrs + + ---------------------- + go_bind subst (Rec prs) body = Let (Rec (bndrs' `zip` rhss')) + (go subst' body) + where + (bndrs, rhss) = unzip prs + (subst', bndrs') = substRecBndrs subst bndrs + rhss' = map (go subst') rhss + + go_bind subst (NonRec b r) body = go_nonrec subst b (go subst r) body + + ---------------------- + go_nonrec subst b (Type ty') body + | isTyVar b = go (extendTvSubst subst b ty') body + -- let a::* = TYPE ty in + go_nonrec subst b r' body + | isId b -- let x = e in + , exprIsTrivial r' || safe_to_inline (idOccInfo b) + = go (extendIdSubst subst b r') body + go_nonrec subst b r' body + = Let (NonRec b' r') (go subst' body) + where + (subst', b') = substBndr subst b + + ---------------------- + -- Unconditionally safe to inline + safe_to_inline :: OccInfo -> Bool + safe_to_inline IAmDead = True + safe_to_inline (OneOcc in_lam one_br _) = not in_lam && one_br + safe_to_inline (IAmALoopBreaker {}) = False + safe_to_inline NoOccInfo = False +\end{code} \ No newline at end of file