X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FcoreSyn%2FCoreUnfold.lhs;h=42db228ab8355896592bbc3e3dbb24c6b161d31e;hb=861e836ed0cc1aa45932ecb3470967964440a0ef;hp=f27289ec0e92901d72b931252ec1e7c23f4aa760;hpb=9d38678ea60ff32f756390a30c659daa22c98c93;p=ghc-hetmet.git diff --git a/ghc/compiler/coreSyn/CoreUnfold.lhs b/ghc/compiler/coreSyn/CoreUnfold.lhs index f27289e..42db228 100644 --- a/ghc/compiler/coreSyn/CoreUnfold.lhs +++ b/ghc/compiler/coreSyn/CoreUnfold.lhs @@ -14,20 +14,18 @@ find, unsurprisingly, a Core expression. \begin{code} module CoreUnfold ( - Unfolding, UnfoldingGuidance, -- types + Unfolding, UnfoldingGuidance, -- Abstract types - noUnfolding, mkUnfolding, + noUnfolding, mkTopUnfolding, mkUnfolding, mkCompulsoryUnfolding, seqUnfolding, mkOtherCon, otherCons, unfoldingTemplate, maybeUnfoldingTemplate, - isEvaldUnfolding, isCheapUnfolding, + isEvaldUnfolding, isValueUnfolding, isCheapUnfolding, isCompulsoryUnfolding, hasUnfolding, hasSomeUnfolding, couldBeSmallEnoughToInline, - certainlySmallEnoughToInline, + certainlyWillInline, okToUnfoldInHiFile, - calcUnfoldingGuidance, - callSiteInline, blackListed ) where @@ -35,187 +33,146 @@ module CoreUnfold ( import CmdLineOpts ( opt_UF_CreationThreshold, opt_UF_UseThreshold, - opt_UF_ScrutConDiscount, opt_UF_FunAppDiscount, - opt_UF_PrimArgDiscount, - opt_UF_KeenessFactor, - opt_UF_CheapOp, opt_UF_DearOp, opt_UF_NoRepLit, + opt_UF_KeenessFactor, + opt_UF_CheapOp, opt_UF_DearOp, opt_UnfoldCasms, opt_PprStyle_Debug, opt_D_dump_inlinings ) import CoreSyn import PprCore ( pprCoreExpr ) import OccurAnal ( occurAnalyseGlobalExpr ) -import BinderInfo ( ) -import CoreUtils ( coreExprType, exprIsTrivial, exprIsValue, exprIsCheap ) -import Id ( Id, idType, idUnique, isId, - getIdSpecialisation, getInlinePragma, getIdUnfolding +import CoreUtils ( exprIsValue, exprIsCheap, exprIsBottom, exprIsTrivial ) +import Id ( Id, idType, idFlavour, isId, idWorkerInfo, + idSpecialisation, idInlinePragma, idUnfolding, + isPrimOpId_maybe ) import VarSet -import Name ( isLocallyDefined ) -import Const ( Con(..), isLitLitLit, isWHNFCon ) -import PrimOp ( PrimOp(..), primOpIsDupable ) -import IdInfo ( ArityInfo(..), InlinePragInfo(..), OccInfo(..) ) -import TyCon ( tyConFamilySize ) -import Type ( splitAlgTyConApp_maybe, splitFunTy_maybe, isUnLiftedType ) -import Const ( isNoRepLit ) -import Unique ( Unique, buildIdKey, augmentIdKey, runSTRepIdKey ) -import Maybes ( maybeToBool ) +import Literal ( isLitLitLit, litIsDupable ) +import PrimOp ( PrimOp(..), primOpIsDupable, primOpOutOfLine, ccallIsCasm ) +import IdInfo ( ArityInfo(..), InlinePragInfo(..), OccInfo(..), IdFlavour(..), CprInfo(..), + insideLam, workerExists, isNeverInlinePrag + ) +import Type ( splitFunTy_maybe, isUnLiftedType ) +import PrelNames ( hasKey, buildIdKey, augmentIdKey ) import Bag -import Util ( isIn, lengthExceeds ) import Outputable + +#if __GLASGOW_HASKELL__ >= 404 +import GlaExts ( fromInt ) +#endif \end{code} + %************************************************************************ %* * -\subsection{@Unfolding@ and @UnfoldingGuidance@ types} +\subsection{Making unfoldings} %* * %************************************************************************ \begin{code} -data Unfolding - = NoUnfolding - - | OtherCon [Con] -- It ain't one of these - -- (OtherCon xs) also indicates that something has been evaluated - -- and hence there's no point in re-evaluating it. - -- OtherCon [] is used even for non-data-type values - -- to indicated evaluated-ness. Notably: - -- data C = C !(Int -> Int) - -- case x of { C f -> ... } - -- Here, f gets an OtherCon [] unfolding. - - | CoreUnfolding -- An unfolding with redundant cached information - CoreExpr -- Template; binder-info is correct - Bool -- exprIsCheap template (cached); it won't duplicate (much) work - -- if you inline this in more than one place - Bool -- exprIsValue template (cached); it is ok to discard a `seq` on - -- this variable - UnfoldingGuidance -- Tells about the *size* of the template. -\end{code} - -\begin{code} -noUnfolding = NoUnfolding -mkOtherCon = OtherCon +mkTopUnfolding expr = mkUnfolding True {- Top level -} expr -mkUnfolding expr +mkUnfolding top_lvl expr = CoreUnfolding (occurAnalyseGlobalExpr expr) - (exprIsCheap expr) + top_lvl (exprIsValue expr) - (calcUnfoldingGuidance opt_UF_CreationThreshold expr) - -unfoldingTemplate :: Unfolding -> CoreExpr -unfoldingTemplate (CoreUnfolding expr _ _ _) = expr -unfoldingTemplate other = panic "getUnfoldingTemplate" - -maybeUnfoldingTemplate :: Unfolding -> Maybe CoreExpr -maybeUnfoldingTemplate (CoreUnfolding expr _ _ _) = Just expr -maybeUnfoldingTemplate other = Nothing - -otherCons (OtherCon cons) = cons -otherCons other = [] - -isEvaldUnfolding :: Unfolding -> Bool -isEvaldUnfolding (OtherCon _) = True -isEvaldUnfolding (CoreUnfolding _ _ is_evald _) = is_evald -isEvaldUnfolding other = False - -isCheapUnfolding :: Unfolding -> Bool -isCheapUnfolding (CoreUnfolding _ is_cheap _ _) = is_cheap -isCheapUnfolding other = False - -hasUnfolding :: Unfolding -> Bool -hasUnfolding (CoreUnfolding _ _ _ _) = True -hasUnfolding other = False + -- Already evaluated -hasSomeUnfolding :: Unfolding -> Bool -hasSomeUnfolding NoUnfolding = False -hasSomeUnfolding other = True - -data UnfoldingGuidance - = UnfoldNever - | UnfoldAlways -- There is no "original" definition, - -- so you'd better unfold. Or: something - -- so cheap to unfold (e.g., 1#) that - -- you should do it absolutely always. - - | UnfoldIfGoodArgs Int -- and "n" value args + (exprIsCheap expr) + -- OK to inline inside a lambda - [Int] -- Discount if the argument is evaluated. - -- (i.e., a simplification will definitely - -- be possible). One elt of the list per *value* arg. + (calcUnfoldingGuidance 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 + -- two copies of the thing while the occurrence-analysed expression doesn't + -- Nevertheless, we don't occ-analyse before computing the size because the + -- size computation bales out after a while, whereas occurrence analysis does not. + -- + -- This can occasionally mean that the guidance is very pessimistic; + -- it gets fixed up next round + +mkCompulsoryUnfolding expr -- Used for things that absolutely must be unfolded + = CompulsoryUnfolding (occurAnalyseGlobalExpr expr) +\end{code} - Int -- The "size" of the unfolding; to be elaborated - -- later. ToDo - Int -- Scrutinee discount: the discount to substract if the thing is in - -- a context (case (thing args) of ...), - -- (where there are the right number of arguments.) -\end{code} +%************************************************************************ +%* * +\subsection{The UnfoldingGuidance type} +%* * +%************************************************************************ \begin{code} instance Outputable UnfoldingGuidance where - ppr UnfoldAlways = ptext SLIT("ALWAYS") ppr UnfoldNever = ptext SLIT("NEVER") ppr (UnfoldIfGoodArgs v cs size discount) - = hsep [ptext SLIT("IF_ARGS"), int v, - if null cs -- always print *something* - then char 'X' - else hcat (map (text . show) cs), + = hsep [ ptext SLIT("IF_ARGS"), int v, + brackets (hsep (map int cs)), int size, int discount ] \end{code} -%************************************************************************ -%* * -\subsection[calcUnfoldingGuidance]{Calculate ``unfolding guidance'' for an expression} -%* * -%************************************************************************ - \begin{code} calcUnfoldingGuidance :: Int -- bomb out if size gets bigger than this -> CoreExpr -- expression to look at -> UnfoldingGuidance calcUnfoldingGuidance bOMB_OUT_SIZE expr - | exprIsTrivial expr -- Often trivial expressions are never bound - -- to an expression, but it can happen. For - -- example, the Id for a nullary constructor has - -- a trivial expression as its unfolding, and - -- we want to make sure that we always unfold it. - = UnfoldAlways - - | otherwise - = case collectBinders expr of { (binders, body) -> + = case collect_val_bndrs expr of { (inline, val_binders, body) -> let - val_binders = filter isId binders + n_val_binders = length val_binders + + max_inline_size = n_val_binders+2 + -- The idea is that if there is an INLINE pragma (inline is True) + -- and there's a big body, we give a size of n_val_binders+2. This + -- This is just enough to fail the no-size-increase test in callSiteInline, + -- so that INLINE things don't get inlined into entirely boring contexts, + -- but no more. + in case (sizeExpr bOMB_OUT_SIZE val_binders body) of - TooBig -> UnfoldNever + TooBig + | not inline -> UnfoldNever + -- A big function with an INLINE pragma must + -- have an UnfoldIfGoodArgs guidance + | inline -> UnfoldIfGoodArgs n_val_binders + (map (const 0) val_binders) + max_inline_size 0 SizeIs size cased_args scrut_discount -> UnfoldIfGoodArgs - (length val_binders) + n_val_binders (map discount_for val_binders) - (I# size) + final_size (I# scrut_discount) where - discount_for b - | num_cases == 0 = 0 - | is_fun_ty = num_cases * opt_UF_FunAppDiscount - | is_data_ty = num_cases * tyConFamilySize tycon * opt_UF_ScrutConDiscount - | otherwise = num_cases * opt_UF_PrimArgDiscount - where - num_cases = foldlBag (\n b' -> if b==b' then n+1 else n) 0 cased_args - -- Count occurrences of b in cased_args - arg_ty = idType b - is_fun_ty = maybeToBool (splitFunTy_maybe arg_ty) - (is_data_ty, tycon) = case (splitAlgTyConApp_maybe (idType b)) of - Nothing -> (False, panic "discount") - Just (tc,_,_) -> (True, tc) + boxed_size = I# size + + final_size | inline = boxed_size `min` max_inline_size + | otherwise = boxed_size + + -- Sometimes an INLINE thing is smaller than n_val_binders+2. + -- A particular case in point is a constructor, which has size 1. + -- We want to inline this regardless, hence the `min` + + discount_for b = foldlBag (\acc (b',n) -> if b==b' then acc+n else acc) + 0 cased_args } + where + collect_val_bndrs e = go False [] e + -- We need to be a bit careful about how we collect the + -- value binders. In ptic, if we see + -- __inline_me (\x y -> e) + -- 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 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} @@ -225,28 +182,21 @@ sizeExpr :: Int -- Bomb out if it gets bigger than this -> CoreExpr -> ExprSize -sizeExpr (I# bOMB_OUT_SIZE) args expr +sizeExpr (I# 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 (Note InlineMe _) = sizeTwo -- The idea is that this is one more - -- than the size of the "call" (i.e. 1) - -- We want to reply "no" to noSizeIncrease - -- for a bare reference (i.e. applied to no args) - -- to an INLINE thing - size_up (Note _ body) = size_up body -- Notes cost nothing size_up (App fun (Type t)) = size_up fun - size_up (App fun arg) = size_up_app fun [arg] + size_up (App fun arg) = size_up_app fun [arg] - size_up (Con con args) = foldr (addSize . size_up) - (size_up_con con args) - args + size_up (Lit lit) | litIsDupable lit = sizeOne + | otherwise = sizeN opt_UF_DearOp -- For lack of anything better - size_up (Lam b e) | isId b = size_up e `addSizeN` 1 + size_up (Lam b e) | isId b = lamScrutDiscount (size_up e `addSizeN` 1) | otherwise = size_up e size_up (Let (NonRec binder rhs) body) @@ -263,70 +213,132 @@ sizeExpr (I# bOMB_OUT_SIZE) args expr where rhs_size = foldr (addSize . size_up . snd) sizeZero pairs - size_up (Case scrut _ alts) - = nukeScrutDiscount (size_up scrut) `addSize` - arg_discount scrut `addSize` - foldr (addSize . size_up_alt) sizeZero alts - --- Just charge for the alts that exist, not the ones that might exist --- `addSizeN` --- case (splitAlgTyConApp_maybe (coreExprType scrut)) of --- Nothing -> 1 --- Just (tc,_,_) -> tyConFamilySize tc + size_up (Case (Var v) _ alts) + | v `elem` top_args -- We are scrutinising an argument variable + = +{- I'm nuking this special case; BUT see the comment with case alternatives. + + (a) It's too eager. We don't want to inline a wrapper into a + context with no benefit. + E.g. \ x. f (x+x) o point in inlining (+) here! + + (b) It's ineffective. Once g's wrapper is inlined, its case-expressions + aren't scrutinising arguments any more + + case alts of + + [alt] -> size_up_alt alt `addSize` SizeIs 0# (unitBag (v, 1)) 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: + -- f x = g x x + -- h y = ...(f e)... + -- If we inline g's wrapper, f looks big, and doesn't get inlined + -- into h; if we inline f first, while it looks small, then g's + -- wrapper will get inlined later anyway. To avoid this nasty + -- ordering difference, we make (case a of (x,y) -> ...), + -- *where a is one of the arguments* look free. + + other -> +-} + alts_size (foldr addSize sizeOne alt_sizes) -- The 1 is for the scrutinee + (foldr1 maxSize alt_sizes) + + -- Good to inline if an arg is scrutinised, because + -- that may eliminate allocation in the caller + -- And it eliminates the case itself + + where + alt_sizes = map size_up_alt alts + + -- 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, I# (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 + + + 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 + -- It's a strict thing, and the price of the call + -- is paid by scrut. Also consider + -- case f x of DEFAULT -> e + -- This is just ';'! Don't charge for it. ------------ - size_up_app (App fun arg) args = size_up_app fun (arg:args) - size_up_app fun args = foldr (addSize . size_up) (fun_discount fun) args + size_up_app (App fun arg) args + | isTypeArg arg = size_up_app fun args + | otherwise = size_up_app fun (arg:args) + size_up_app fun args = foldr (addSize . nukeScrutDiscount . size_up) + (size_up_fun fun args) + args -- A function application with at least one value argument -- so if the function is an argument give it an arg-discount + -- -- Also behave specially if the function is a build - fun_discount (Var fun) | idUnique fun == buildIdKey = buildSize - | idUnique fun == augmentIdKey = augmentSize - | fun `is_elem` args = scrutArg fun - fun_discount other = sizeZero + -- + -- Also if the function is a constant Id (constr or primop) + -- compute discounts specially + size_up_fun (Var fun) args + | fun `hasKey` buildIdKey = buildSize + | fun `hasKey` augmentIdKey = augmentSize + | otherwise + = case idFlavour fun of + DataConId dc -> conSizeN (valArgCount args) + + 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 + -- is applied to one of the function's arguments, but it's + -- not good. At the moment, any unlifted-type arg gets a + -- 'True' for 'yes I'm evald', so we collect the discount even + -- 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` + (1 + length (filter (not . exprIsTrivial) args)) + -- The 1+ is for the function itself + -- Add 1 for each non-trivial arg; + -- the allocation cost, as in let(rec) + -- Slight hack here: for constructors the args are almost always + -- trivial; and for primops they are almost always prim typed + -- 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_alt (con, bndrs, rhs) = size_up rhs - -- Don't charge for args, so that wrappers look cheap + -- Don't charge for args, so that wrappers look cheap + -- (See comments about wrappers with Case) ------------ - size_up_con (Literal lit) args | isNoRepLit lit = sizeN opt_UF_NoRepLit - | otherwise = sizeOne - - size_up_con (DataCon dc) args = conSizeN (valArgCount args) - - size_up_con (PrimOp op) args = foldr addSize (sizeN op_cost) (map arg_discount args) - -- Give an arg-discount if a primop is applies to - -- one of the function's arguments - where - op_cost | primOpIsDupable op = opt_UF_CheapOp - | otherwise = opt_UF_DearOp - -- We want to record if we're case'ing, or applying, an argument - arg_discount (Var v) | v `is_elem` args = scrutArg v - arg_discount other = sizeZero - - ------------ - is_elem :: Id -> [Id] -> Bool - is_elem = isIn "size_up_scrut" + fun_discount v | v `elem` top_args = SizeIs 0# (unitBag (v, opt_UF_FunAppDiscount)) 0# + fun_discount other = sizeZero ------------ -- These addSize things have to be here because -- I don't want to give them bOMB_OUT_SIZE as an argument - addSizeN TooBig _ = TooBig + addSizeN TooBig _ = TooBig addSizeN (SizeIs n xs d) (I# m) - | n_tot -# d <# bOMB_OUT_SIZE = SizeIs n_tot xs d - | otherwise = TooBig + | n_tot ># bOMB_OUT_SIZE = TooBig + | otherwise = SizeIs n_tot xs d where n_tot = n +# m addSize TooBig _ = TooBig addSize _ TooBig = TooBig addSize (SizeIs n1 xs d1) (SizeIs n2 ys d2) - | (n_tot -# d_tot) <# bOMB_OUT_SIZE = SizeIs n_tot xys d_tot - | otherwise = TooBig + | n_tot ># bOMB_OUT_SIZE = TooBig + | otherwise = SizeIs n_tot xys d_tot where n_tot = n1 +# n2 d_tot = d1 +# d2 @@ -338,20 +350,34 @@ Code for manipulating sizes \begin{code} data ExprSize = TooBig - | SizeIs Int# -- Size found - (Bag Id) -- Arguments cased herein - Int# -- Size to subtract if result is scrutinised - -- by a case expression + | SizeIs Int# -- Size found + (Bag (Id,Int)) -- Arguments cased herein, and discount for each such + Int# -- Size to subtract if result is scrutinised + -- by a case expression + +isTooBig TooBig = True +isTooBig _ = False + +maxSize TooBig _ = TooBig +maxSize _ TooBig = TooBig +maxSize s1@(SizeIs n1 _ _) s2@(SizeIs n2 _ _) | n1 ># n2 = s1 + | otherwise = s2 sizeZero = SizeIs 0# emptyBag 0# sizeOne = SizeIs 1# emptyBag 0# sizeTwo = SizeIs 2# emptyBag 0# sizeN (I# n) = SizeIs n emptyBag 0# conSizeN (I# n) = SizeIs 1# emptyBag (n +# 1#) - -- Treat constructors as size 1, that unfoldAlways responsds 'False' - -- when asked about 'x' when x is bound to (C 3#). - -- This avoids gratuitous 'ticks' when x itself appears as an - -- atomic constructor argument. + -- 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 (I# x) has size 1, + -- which is the same as a lone variable; and hence 'v' will + -- always be replaced by (I# x), where v is bound to I# x. + +primOpSize op n_args + | not (primOpIsDupable op) = sizeN opt_UF_DearOp + | not (primOpOutOfLine op) = sizeZero -- These are good to inline + | otherwise = sizeOne buildSize = SizeIs (-2#) emptyBag 4# -- We really want to inline applications of build @@ -365,10 +391,12 @@ augmentSize = SizeIs (-2#) emptyBag 4# -- Ditto (augment t (\cn -> e) ys) should cost only the cost of -- e plus ys. The -2 accounts for the \cn -scrutArg v = SizeIs 0# (unitBag v) 0# - nukeScrutDiscount (SizeIs n vs d) = SizeIs n vs 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 { I# d -> SizeIs n vs d } +lamScrutDiscount TooBig = TooBig \end{code} @@ -407,14 +435,21 @@ use'' on the other side. Can be overridden w/ flaggery. Just the same as smallEnoughToInline, except that it has no actual arguments. \begin{code} -couldBeSmallEnoughToInline :: UnfoldingGuidance -> Bool -couldBeSmallEnoughToInline UnfoldNever = False -couldBeSmallEnoughToInline other = True - -certainlySmallEnoughToInline :: UnfoldingGuidance -> Bool -certainlySmallEnoughToInline UnfoldNever = False -certainlySmallEnoughToInline UnfoldAlways = True -certainlySmallEnoughToInline (UnfoldIfGoodArgs _ _ size _) = size <= opt_UF_UseThreshold +couldBeSmallEnoughToInline :: Int -> CoreExpr -> Bool +couldBeSmallEnoughToInline threshold rhs = case calcUnfoldingGuidance threshold rhs of + UnfoldNever -> False + other -> True + +certainlyWillInline :: Id -> Bool + -- Sees if the Id is pretty certain to inline +certainlyWillInline v + = case idUnfolding v of + + CoreUnfolding _ _ is_value _ g@(UnfoldIfGoodArgs n_vals _ size _) + -> is_value + && size - (n_vals +1) <= opt_UF_UseThreshold + + other -> False \end{code} @okToUnfoldInHifile@ is used when emitting unfolding info into an interface @@ -433,20 +468,21 @@ okToUnfoldInHiFile :: CoreExpr -> Bool okToUnfoldInHiFile e = opt_UnfoldCasms || go e where -- Race over an expression looking for CCalls.. - go (Var _) = True - go (Con (Literal lit) _) = not (isLitLitLit lit) - go (Con (PrimOp op) args) = okToUnfoldPrimOp op && all go args - go (Con con args) = True -- con args are always atomic + go (Var v) = case isPrimOpId_maybe v of + Just op -> okToUnfoldPrimOp op + Nothing -> True + go (Lit lit) = not (isLitLitLit lit) go (App fun arg) = go fun && go arg go (Lam _ body) = go body go (Let binds body) = and (map go (body :rhssOfBind binds)) - go (Case scrut bndr alts) = and (map go (scrut:rhssOfAlts alts)) + go (Case scrut bndr alts) = and (map go (scrut:rhssOfAlts alts)) && + not (any isLitLitLit [ lit | (LitAlt lit, _, _) <- alts ]) go (Note _ body) = go body go (Type _) = True -- ok to unfold a PrimOp as long as it's not a _casm_ - okToUnfoldPrimOp (CCallOp _ is_casm _ _) = not is_casm - okToUnfoldPrimOp _ = True + okToUnfoldPrimOp (CCallOp ccall) = not (ccallIsCasm ccall) + okToUnfoldPrimOp _ = True \end{code} @@ -467,101 +503,123 @@ and occurs exactly once or 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. Tt turns out that the convenient way to prevent +them inlining is to give them a NOINLINE pragma, which we do in +StrictAnal.addStrictnessInfoToTopId + \begin{code} callSiteInline :: Bool -- True <=> the Id is black listed -> Bool -- 'inline' note at call site + -> OccInfo -> Id -- The Id -> [Bool] -- One for each value arg; True if it is interesting -> Bool -- True <=> continuation is interesting -> Maybe CoreExpr -- Unfolding, if any -callSiteInline black_listed inline_call id arg_infos interesting_cont - = case getIdUnfolding id of { +callSiteInline black_listed inline_call occ id arg_infos interesting_cont + = case idUnfolding id of { NoUnfolding -> Nothing ; - OtherCon _ -> Nothing ; - CoreUnfolding unf_template is_cheap _ guidance -> + OtherCon cs -> Nothing ; + CompulsoryUnfolding unf_template | black_listed -> Nothing + | otherwise -> Just unf_template ; + -- Constructors have compulsory unfoldings, but + -- may have rules, in which case they are + -- black listed till later + CoreUnfolding unf_template is_top is_value is_cheap guidance -> let result | yes_or_no = Just unf_template | otherwise = Nothing - inline_prag = getInlinePragma id n_val_args = length arg_infos - yes_or_no = - case inline_prag of - IAmDead -> pprTrace "callSiteInline: dead" (ppr id) False - IMustNotBeINLINEd -> False - IAmALoopBreaker -> False - IMustBeINLINEd -> True -- Overrides absolutely everything, including the black list - ICanSafelyBeINLINEd in_lam one_br -> consider in_lam True one_br - NoInlinePragInfo -> consider InsideLam False False - - consider in_lam once once_in_one_branch + yes_or_no | black_listed = False + | otherwise = case occ of + IAmDead -> pprTrace "callSiteInline: dead" (ppr id) False + IAmALoopBreaker -> False + OneOcc in_lam one_br -> (not in_lam || is_cheap) && consider_safe in_lam True one_br + NoOccInfo -> is_cheap && consider_safe True False False + + consider_safe in_lam once once_in_one_branch + -- consider_safe decides whether it's a good idea to inline something, + -- given that there's no work-duplication issue (the caller checks that). + -- once_in_one_branch = True means there's a unique textual occurrence | inline_call = True - | once_in_one_branch -- Be very keen to inline something if this is its unique occurrence; that - -- gives a good chance of eliminating the original binding for the thing. - -- The only time we hold back is when substituting inside a lambda; - -- then if the context is totally uninteresting (not applied, not scrutinised) - -- there is no point in substituting because it might just increase allocation. - = WARN( case in_lam of { NotInsideLam -> True; other -> False }, - text "callSiteInline:oneOcc" <+> ppr id ) - -- If it has one occurrence, not inside a lambda, PreInlineUnconditionally - -- should have zapped it already - is_cheap && (not (null arg_infos) || interesting_cont) - - | otherwise -- Occurs (textually) more than once, so look at its size + + | once_in_one_branch + -- Be very keen to inline something if this is its unique occurrence: + -- + -- a) Inlining gives a good chance of eliminating the original + -- binding (and hence the allocation) for the thing. + -- (Provided it's not a top level binding, in which case the + -- allocation costs nothing.) + -- + -- b) Inlining a function that is called only once exposes the + -- body function to the call site. + -- + -- The only time we hold back is when substituting inside a lambda; + -- then if the context is totally uninteresting (not applied, not scrutinised) + -- there is no point in substituting because it might just increase allocation, + -- by allocating the function itself many times + -- + -- Note: there used to be a '&& not top_level' in the guard above, + -- but that stopped us inlining top-level functions used only once, + -- which is stupid + = not in_lam || not (null arg_infos) || interesting_cont + + | otherwise = case guidance of - UnfoldAlways -> True - UnfoldNever -> False + UnfoldNever -> False ; UnfoldIfGoodArgs n_vals_wanted arg_discounts size res_discount - | enough_args && size <= (n_vals_wanted + 1) + + | enough_args && size <= (n_vals_wanted + 1) -- No size increase -- Size of call is n_vals_wanted (+1 for the function) - -> case in_lam of - NotInsideLam -> True - InsideLam -> is_cheap - - | not (or arg_infos || really_interesting_cont || once) - -- If it occurs more than once, there must be something interesting - -- about some argument, or the result, to make it worth inlining - -- We also drop this case if the thing occurs once, although perhaps in - -- several branches. In this case we are keener about inlining in the hope - -- that we'll be able to drop the allocation for the function altogether. - -> False - - | otherwise - -> case in_lam of - NotInsideLam -> small_enough - InsideLam -> is_cheap && small_enough - - where - 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 - -- This rather elaborate defn for really_interesting_cont is important - -- Consider an I# = INLINE (\x -> I# {x}) - -- The unfolding guidance deems it to have size 2, and no arguments. - -- So in an application (I# y) we must take the extra arg 'y' as - -- evidence of an interesting context! - - small_enough = (size - discount) <= opt_UF_UseThreshold - discount = computeDiscount n_vals_wanted arg_discounts res_discount + -> True + + | otherwise + -> some_benefit && small_enough + + where + some_benefit = or arg_infos || really_interesting_cont || + (not is_top && (once || (n_vals_wanted > 0 && enough_args))) + -- 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 + -- really_interesting_cont tells if the result of the + -- call is in an interesting context. + + small_enough = (size - discount) <= opt_UF_UseThreshold + discount = computeDiscount n_vals_wanted arg_discounts res_discount arg_infos really_interesting_cont - - + in #ifdef DEBUG if opt_D_dump_inlinings then pprTrace "Considering inlining" - (ppr id <+> vcat [text "black listed" <+> ppr black_listed, - text "inline prag:" <+> ppr inline_prag, + (ppr id <+> vcat [text "black listed:" <+> ppr black_listed, + text "occ info:" <+> ppr occ, text "arg infos" <+> ppr arg_infos, text "interesting continuation" <+> ppr interesting_cont, - text "is cheap" <+> ppr is_cheap, + text "is value:" <+> ppr is_value, + text "is cheap:" <+> ppr is_cheap, text "guidance" <+> ppr guidance, text "ANSWER =" <+> if yes_or_no then text "YES" else text "NO", if yes_or_no then @@ -584,7 +642,9 @@ computeDiscount n_vals_wanted arg_discounts res_discount arg_infos result_used -- we also discount 1 for each argument passed, because these will -- reduce with the lambdas in the function (we count 1 for a lambda -- in size_up). - = length (take n_vals_wanted arg_infos) + + = 1 + -- Discount of 1 because the result replaces the call + -- so we count 1 for the function itself + length (take n_vals_wanted arg_infos) + -- Discount of 1 for each arg supplied, because the -- result replaces the call round (opt_UF_KeenessFactor * @@ -614,6 +674,19 @@ For optimisation we use phase 1,2 and nothing (i.e. no -finline-phase flag) in that order. The meanings of these are determined by the @blackListed@ function here. +The final simplification doesn't have a phase number. + +Pragmas +~~~~~~~ + Pragma Black list if + +(least black listing, most inlining) + INLINE n foo phase is Just p *and* p Maybe Int -- Inline phase @@ -623,28 +696,26 @@ blackListed :: IdSet -- Used in transformation rules -- inlined because of the inline phase we are in. This is the sole -- place that the inline phase number is looked at. --- Phase 0: used for 'no imported inlinings please' --- This prevents wrappers getting inlined which in turn is bad for full laziness -blackListed rule_vars (Just 0) - = \v -> not (isLocallyDefined v) - --- Phase 1: don't inline any rule-y things or things with specialisations -blackListed rule_vars (Just 1) - = \v -> let v_uniq = idUnique v - in v `elemVarSet` rule_vars - || not (isEmptyCoreRules (getIdSpecialisation v)) - || v_uniq == runSTRepIdKey - --- Phase 2: allow build/augment to inline, and specialisations -blackListed rule_vars (Just 2) - = \v -> let v_uniq = idUnique v - in (v `elemVarSet` rule_vars && not (v_uniq == buildIdKey || - v_uniq == augmentIdKey)) - || v_uniq == runSTRepIdKey - --- Otherwise just go for it -blackListed rule_vars phase - = \v -> False +blackListed rule_vars Nothing -- Last phase + = \v -> isNeverInlinePrag (idInlinePragma v) + +blackListed rule_vars (Just phase) + = \v -> normal_case rule_vars phase v + +normal_case rule_vars phase v + = case idInlinePragma v of + NoInlinePragInfo -> has_rules + + IMustNotBeINLINEd from_INLINE Nothing + | from_INLINE -> has_rules -- Black list until final phase + | otherwise -> True -- Always blacklisted + + IMustNotBeINLINEd from_INLINE (Just threshold) + | from_INLINE -> (phase < threshold && has_rules) + | otherwise -> (phase < threshold || has_rules) + where + has_rules = v `elemVarSet` rule_vars + || not (isEmptyCoreRules (idSpecialisation v)) \end{code}