X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FcoreSyn%2FCoreUnfold.lhs;h=5797cba2bf336f6d1e3c762c94e2f5346ce27d94;hb=8604da0136707cc14845d14a88c2272fe576b6d0;hp=d57f1886fc0377e7b7d91397a2c169374a9915a2;hpb=0065d5ab628975892cea1ec7303f968c3338cbe1;p=ghc-hetmet.git diff --git a/compiler/coreSyn/CoreUnfold.lhs b/compiler/coreSyn/CoreUnfold.lhs index d57f188..5797cba 100644 --- a/compiler/coreSyn/CoreUnfold.lhs +++ b/compiler/coreSyn/CoreUnfold.lhs @@ -1,7 +1,9 @@ % +% (c) The University of Glasgow 2006 % (c) The AQUA Project, Glasgow University, 1994-1998 % -\section[CoreUnfold]{Core-syntax unfoldings} + +Core-syntax unfoldings Unfoldings (which can travel across module boundaries) are in Core syntax (namely @CoreExpr@s). @@ -25,36 +27,28 @@ module CoreUnfold ( couldBeSmallEnoughToInline, certainlyWillInline, smallEnoughToInline, - callSiteInline - ) where + callSiteInline, CallCtxt(..) -#include "HsVersions.h" + ) where -import StaticFlags ( opt_UF_CreationThreshold, opt_UF_UseThreshold, - opt_UF_FunAppDiscount, opt_UF_KeenessFactor, - opt_UF_DearOp, - ) -import DynFlags ( DynFlags, DynFlag(..), dopt ) +import StaticFlags +import DynFlags import CoreSyn -import PprCore ( pprCoreExpr ) -import OccurAnal ( occurAnalyseExpr ) -import CoreUtils ( exprIsHNF, exprIsCheap, exprIsTrivial ) -import Id ( Id, idType, isId, - idUnfolding, globalIdDetails - ) -import DataCon ( isUnboxedTupleCon ) -import Literal ( litSize ) -import PrimOp ( primOpIsDupable, primOpOutOfLine ) -import IdInfo ( OccInfo(..), GlobalIdDetails(..) ) -import Type ( isUnLiftedType ) -import PrelNames ( hasKey, buildIdKey, augmentIdKey ) +import PprCore () -- Instances +import OccurAnal +import CoreUtils +import Id +import DataCon +import Literal +import PrimOp +import IdInfo +import Type +import PrelNames import Bag import FastTypes +import FastString import Outputable -#if __GLASGOW_HASKELL__ >= 404 -import GLAEXTS ( Int# ) -#endif \end{code} @@ -65,8 +59,10 @@ import GLAEXTS ( Int# ) %************************************************************************ \begin{code} +mkTopUnfolding :: CoreExpr -> Unfolding mkTopUnfolding expr = mkUnfolding True {- Top level -} expr +mkUnfolding :: Bool -> CoreExpr -> Unfolding mkUnfolding top_lvl expr = CoreUnfolding (occurAnalyseExpr expr) top_lvl @@ -87,6 +83,15 @@ mkUnfolding top_lvl expr -- This can occasionally mean that the guidance is very pessimistic; -- 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 (CoreUnfolding e top hnf cheap 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} @@ -100,9 +105,9 @@ 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 ] @@ -164,14 +169,14 @@ 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) \end{code} \begin{code} -sizeExpr :: Int# -- Bomb out if it gets bigger than this +sizeExpr :: FastInt -- Bomb out if it gets bigger than this -> [Id] -- Arguments; we're interested in which of these -- get case'd -> CoreExpr @@ -180,10 +185,10 @@ sizeExpr :: Int# -- 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 #-} @@ -191,9 +196,11 @@ 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 (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) @@ -229,7 +236,7 @@ sizeExpr bOMB_OUT_SIZE top_args expr case alts of - [alt] -> size_up_alt alt `addSize` SizeIs 0# (unitBag (v, 1)) 0# + [alt] -> size_up_alt alt `addSize` SizeIs (_ILIT(0)) (unitBag (v, 1)) (_ILIT(0)) -- We want to make wrapper-style evaluation look cheap, so that -- when we inline a wrapper it doesn't make call site (much) bigger -- Otherwise we get nasty phase ordering stuff: @@ -255,15 +262,14 @@ 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 - = SizeIs tot (unitBag (v, iBox (_ILIT 1 +# tot -# max)) `unionBags` max_disc) max_scrut + 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 -- The 1+ is a little discount for reduced allocation in the caller alts_size tot_size _ = tot_size --- gaw 2004 size_up (Case e _ _ alts) = nukeScrutDiscount (size_up e) `addSize` foldr (addSize . size_up_alt) sizeZero alts -- We don't charge for the case itself @@ -294,7 +300,7 @@ 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 @@ -304,7 +310,7 @@ 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; @@ -314,17 +320,17 @@ 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 0# (unitBag (v, opt_UF_FunAppDiscount)) 0# - fun_discount other = sizeZero + fun_discount v | v `elem` top_args = SizeIs (_ILIT(0)) (unitBag (v, opt_UF_FunAppDiscount)) (_ILIT(0)) + fun_discount _ = sizeZero ------------ -- These addSize things have to be here because @@ -353,20 +359,26 @@ 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 = SizeIs (_ILIT 0) emptyBag (_ILIT 0) -sizeOne = SizeIs (_ILIT 1) emptyBag (_ILIT 0) -sizeN n = SizeIs (iUnbox n) emptyBag (_ILIT 0) +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)) conSizeN dc n - | isUnboxedTupleCon dc = SizeIs (_ILIT 0) emptyBag (iUnbox n +# _ILIT 1) - | otherwise = SizeIs (_ILIT 1) emptyBag (iUnbox n +# _ILIT 1) + | isUnboxedTupleCon dc = SizeIs (_ILIT(0)) emptyBag (iUnbox n +# _ILIT(1)) + | otherwise = SizeIs (_ILIT(1)) emptyBag (iUnbox n +# _ILIT(1)) -- Treat constructors as size 1; we are keen to expose them -- (and we charge separately for their args). We can't treat -- them as size zero, else we find that (iBox x) has size 1, @@ -378,6 +390,7 @@ 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) @@ -392,7 +405,8 @@ primOpSize op n_args -- and there's a good chance it'll get inlined back into C's RHS. Urgh! | otherwise = sizeOne -buildSize = SizeIs (-2#) emptyBag 4# +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) -- Indeed, we should add a result_discount becuause build is @@ -400,16 +414,19 @@ buildSize = SizeIs (-2#) emptyBag 4# -- build is saturated (it usually is). The "-2" discounts for the \c n, -- The "4" is rather arbitrary. -augmentSize = SizeIs (-2#) emptyBag 4# +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 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} @@ -450,20 +467,20 @@ 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} @@ -492,18 +509,33 @@ StrictAnal.addStrictnessInfoToTopId \begin{code} callSiteInline :: DynFlags -> Bool -- True <=> the Id can be inlined - -> Bool -- 'inline' note at call site - -> OccInfo -> 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 - -> Bool -- True <=> continuation is interesting + -> CallCtxt -- True <=> continuation is interesting -> Maybe CoreExpr -- Unfolding, if any -callSiteInline dflags active_inline inline_call occ id arg_infos interesting_cont +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 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 @@ -520,14 +552,8 @@ callSiteInline dflags active_inline inline_call occ id arg_infos interesting_con n_val_args = length arg_infos - yes_or_no - | not active_inline = False - | otherwise = case occ of - IAmDead -> pprTrace "callSiteInline: dead" (ppr id) False - IAmALoopBreaker -> False - --OneOcc in_lam _ _ -> (not in_lam || is_cheap) && consider_safe True - other -> is_cheap && consider_safe False - -- we consider even the once-in-one-branch + yes_or_no = active_inline && is_cheap && consider_safe + -- We consider even the once-in-one-branch -- occurrences, because they won't all have been -- caught by preInlineUnconditionally. In particular, -- if the occurrence is once inside a lambda, and the @@ -535,17 +561,13 @@ callSiteInline dflags active_inline inline_call occ id arg_infos interesting_con -- pre-inline will not have inlined it for fear of -- invalidating the occurrence info in the rhs. - consider_safe once + consider_safe -- consider_safe decides whether it's a good idea to -- inline something, given that there's no -- work-duplication issue (the caller checks that). - | inline_call = True - - | otherwise = case guidance of UnfoldNever -> False UnfoldIfGoodArgs n_vals_wanted arg_discounts size res_discount - | enough_args && size <= (n_vals_wanted + 1) -- Inline unconditionally if there no size increase -- Size of call is n_vals_wanted (+1 for the function) @@ -555,44 +577,47 @@ callSiteInline dflags active_inline inline_call occ id arg_infos interesting_con -> some_benefit && small_enough where - some_benefit = or arg_infos || really_interesting_cont || - (not is_top && ({- once || -} (n_vals_wanted > 0 && enough_args))) - -- [was (once && not in_lam)] - -- If it occurs more than once, there must be - -- something interesting about some argument, or the - -- result context, to make it worth inlining - -- - -- If a function has a nested defn we also record - -- some-benefit, on the grounds that we are often able - -- to eliminate the binding, and hence the allocation, - -- for the function altogether; this is good for join - -- points. But this only makes sense for *functions*; - -- inlining a constructor doesn't help allocation - -- unless the result is scrutinised. UNLESS the - -- constructor occurs just once, albeit possibly in - -- multiple case 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. - - enough_args = n_val_args >= n_vals_wanted - really_interesting_cont | n_val_args < n_vals_wanted = False -- Too few args - | n_val_args == n_vals_wanted = interesting_cont - | otherwise = True -- Extra args + enough_args = n_val_args >= n_vals_wanted + + some_benefit = or arg_infos || really_interesting_cont + -- There must be something interesting + -- about some argument, or the result + -- context, to make it worth inlining + + really_interesting_cont + | n_val_args < n_vals_wanted = False -- Too few args + | n_val_args == n_vals_wanted = interesting_saturated_call + | otherwise = True -- Extra args -- really_interesting_cont tells if the result of the -- call is in an interesting context. + interesting_saturated_call + = case cont_info of + BoringCtxt -> not is_top && n_vals_wanted > 0 -- Note [Nested functions] + CaseCtxt -> not lone_variable || not is_value -- Note [Lone variables] + ArgCtxt {} -> True + -- Was: n_vals_wanted > 0; but see test eyeball/inline1.hs + small_enough = (size - discount) <= opt_UF_UseThreshold - discount = computeDiscount n_vals_wanted arg_discounts res_discount - arg_infos really_interesting_cont + discount = computeDiscount n_vals_wanted arg_discounts + res_discount' arg_infos + res_discount' = case cont_info of + 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. + -- Otherwise we, rather arbitrarily, threshold it. Yuk. + -- But we want to aovid inlining large functions that return + -- constructors into contexts that are simply "interesting" in if dopt Opt_D_dump_inlinings dflags then pprTrace "Considering inlining" (ppr id <+> vcat [text "active:" <+> ppr active_inline, - text "occ info:" <+> ppr occ, text "arg infos" <+> ppr arg_infos, - text "interesting continuation" <+> ppr interesting_cont, + text "interesting continuation" <+> ppr cont_info, text "is value:" <+> ppr is_value, text "is cheap:" <+> ppr is_cheap, text "guidance" <+> ppr guidance, @@ -601,9 +626,78 @@ callSiteInline dflags active_inline inline_call occ id arg_infos interesting_con else result } +\end{code} + +Note [Nested functions] +~~~~~~~~~~~~~~~~~~~~~~~ +If a function has a nested defn we also record some-benefit, on the +grounds that we are often able to eliminate the binding, and hence the +allocation, for the function altogether; this is good for join points. +But this only makes sense for *functions*; inlining a constructor +doesn't help allocation unless the result is scrutinised. UNLESS the +constructor occurs just once, albeit possibly in multiple case +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 [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 + as an arg of lazy fn, or rhs Stop + as scrutinee of a case Select + as arg of a strict fn ArgOf +AND + it is bound to a value +then we should not inline it (unless there is some other reason, +e.g. is is the sole occurrence). That is what is happening at +the use of 'lone_variable' in 'interesting_saturated_call'. + +Why? At least in the case-scrutinee situation, turning + let x = (a,b) in case x of y -> ... +into + let x = (a,b) in case (a,b) of y -> ... +and thence to + let x = (a,b) in let y = (a,b) in ... +is bad if the binding for x will remain. + +Another example: I discovered that strings +were getting inlined straight back into applications of 'error' +because the latter is strict. + s = "foo" + f = \x -> ...(error s)... + +Fundamentally such contexts should not encourage inlining because the +context can ``see'' the unfolding of the variable (e.g. case or a +RULE) so there's no gain. If the thing is bound to a value. + +However, watch out: + + * Consider this: + foo = _inline_ (\n. [n]) + bar = _inline_ (foo 20) + baz = \n. case bar of { (m:_) -> m + n } + Here we really want to inline 'bar' so that we can inline 'foo' + and the whole thing unravels as it should obviously do. This is + important: in the NDP project, 'bar' generates a closure data + structure rather than a list. + + * Even a type application or coercion isn't a lone variable. + Consider + case $fMonadST @ RealWorld of { :DMonad a b c -> c } + We had better inline that sucker! The case won't see through it. + + For now, I'm treating treating a variable applied to types + in a *lazy* context "lone". The motivating example was + f = /\a. \x. BIG + g = /\a. \y. h (f a) + There's no advantage in inlining f here, and perhaps + a significant disadvantage. Hence some_val_args in the Stop case -computeDiscount :: Int -> [Int] -> Int -> [Bool] -> Bool -> Int -computeDiscount n_vals_wanted arg_discounts res_discount arg_infos result_used +\begin{code} +computeDiscount :: Int -> [Int] -> Int -> [Bool] -> Int +computeDiscount n_vals_wanted arg_discounts result_discount arg_infos -- We multiple the raw discounts (args_discount and result_discount) -- ty opt_UnfoldingKeenessFactor because the former have to do with -- *size* whereas the discounts imply that there's some extra @@ -625,8 +719,4 @@ computeDiscount n_vals_wanted arg_discounts res_discount arg_infos result_used mk_arg_discount discount is_evald | is_evald = discount | otherwise = 0 - - -- Don't give a result discount unless there are enough args - result_discount | result_used = res_discount -- Over-applied, or case scrut - | otherwise = 0 \end{code}