X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FcoreSyn%2FCoreUnfold.lhs;h=d57f1886fc0377e7b7d91397a2c169374a9915a2;hb=7f24ae51ed36c5c0308a2d0de23e243f32a0043c;hp=6fd0fd9b4db127dafed044a513f09f64197e1df8;hpb=edd06d674dd5ffa05c08b6d75dd3a6b63b016f58;p=ghc-hetmet.git diff --git a/ghc/compiler/coreSyn/CoreUnfold.lhs b/ghc/compiler/coreSyn/CoreUnfold.lhs index 6fd0fd9..d57f188 100644 --- a/ghc/compiler/coreSyn/CoreUnfold.lhs +++ b/ghc/compiler/coreSyn/CoreUnfold.lhs @@ -14,239 +14,191 @@ find, unsurprisingly, a Core expression. \begin{code} module CoreUnfold ( - Unfolding, UnfoldingGuidance, -- types + Unfolding, UnfoldingGuidance, -- Abstract types - noUnfolding, mkUnfolding, - mkOtherCon, otherCons, + noUnfolding, mkTopUnfolding, mkUnfolding, mkCompulsoryUnfolding, seqUnfolding, + evaldUnfolding, mkOtherCon, otherCons, unfoldingTemplate, maybeUnfoldingTemplate, - isEvaldUnfolding, isCheapUnfolding, - hasUnfolding, + isEvaldUnfolding, isValueUnfolding, isCheapUnfolding, isCompulsoryUnfolding, + hasUnfolding, hasSomeUnfolding, neverUnfold, couldBeSmallEnoughToInline, - certainlySmallEnoughToInline, - okToUnfoldInHiFile, + certainlyWillInline, smallEnoughToInline, - calcUnfoldingGuidance, - - callSiteInline, blackListed + callSiteInline ) where #include "HsVersions.h" -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_UnfoldCasms, opt_PprStyle_Debug, - opt_D_dump_inlinings +import StaticFlags ( opt_UF_CreationThreshold, opt_UF_UseThreshold, + opt_UF_FunAppDiscount, opt_UF_KeenessFactor, + opt_UF_DearOp, ) +import DynFlags ( DynFlags, DynFlag(..), dopt ) 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 OccurAnal ( occurAnalyseExpr ) +import CoreUtils ( exprIsHNF, exprIsCheap, exprIsTrivial ) +import Id ( Id, idType, isId, + idUnfolding, globalIdDetails ) -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 DataCon ( isUnboxedTupleCon ) +import Literal ( litSize ) +import PrimOp ( primOpIsDupable, primOpOutOfLine ) +import IdInfo ( OccInfo(..), GlobalIdDetails(..) ) +import Type ( isUnLiftedType ) +import PrelNames ( hasKey, buildIdKey, augmentIdKey ) import Bag -import Util ( isIn, lengthExceeds ) +import FastTypes import Outputable + +#if __GLASGOW_HASKELL__ >= 404 +import GLAEXTS ( Int# ) +#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 - -mkUnfolding expr - = CoreUnfolding (occurAnalyseGlobalExpr expr) - (exprIsCheap expr) - (exprIsValue expr) - (calcUnfoldingGuidance opt_UF_CreationThreshold expr) +mkTopUnfolding expr = mkUnfolding True {- Top level -} expr -unfoldingTemplate :: Unfolding -> CoreExpr -unfoldingTemplate (CoreUnfolding expr _ _ _) = expr -unfoldingTemplate other = panic "getUnfoldingTemplate" +mkUnfolding top_lvl expr + = CoreUnfolding (occurAnalyseExpr expr) + top_lvl -maybeUnfoldingTemplate :: Unfolding -> Maybe CoreExpr -maybeUnfoldingTemplate (CoreUnfolding expr _ _ _) = Just expr -maybeUnfoldingTemplate other = Nothing + (exprIsHNF expr) + -- Already evaluated -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 - -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 (occurAnalyseExpr 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 + case (sizeExpr (iUnbox 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 + | otherwise -> 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) - (I# scrut_discount) + final_size + (iBox 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 = iBox 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} -sizeExpr :: Int -- Bomb out if it gets bigger than this +sizeExpr :: Int# -- Bomb out if it gets bigger than this -> [Id] -- Arguments; we're interested in which of these -- get case'd -> CoreExpr -> ExprSize -sizeExpr (I# bOMB_OUT_SIZE) args expr +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 (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 InlineMe body) = 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 #-} + -- op1 = ... + -- op2 = ... + -- then we'll get a dfun which is a pair of two INLINE lambdas - size_up (Note _ body) = size_up body -- Notes cost nothing + size_up (Note _ body) = size_up body -- Other 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 (Type t)) = size_up fun + 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) = sizeN (litSize lit) - 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) @@ -263,95 +215,182 @@ 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) no 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, 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 + -- 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 globalIdDetails fun of + DataConWorkId dc -> conSizeN dc (valArgCount args) + + FCallId fc -> 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 + -- 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 (SizeIs n xs d) (I# m) - | n_tot -# d <# bOMB_OUT_SIZE = SizeIs n_tot xs d - | otherwise = TooBig - where - n_tot = n +# m + addSizeN TooBig _ = TooBig + addSizeN (SizeIs n xs d) m = mkSizeIs bOMB_OUT_SIZE (n +# iUnbox m) xs d - 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 - where - n_tot = n1 +# n2 - d_tot = d1 +# d2 - xys = xs `unionBags` ys + addSize TooBig _ = TooBig + addSize _ TooBig = TooBig + addSize (SizeIs n1 xs d1) (SizeIs n2 ys d2) + = mkSizeIs bOMB_OUT_SIZE (n1 +# n2) (xs `unionBags` ys) (d1 +# d2) \end{code} 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 - -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. + | SizeIs FastInt -- Size found + (Bag (Id,Int)) -- Arguments cased herein, and discount for each such + FastInt -- Size to subtract if result is scrutinised + -- by a case expression + +-- subtract the discount before deciding whether to bale out. eg. we +-- want to inline a large constructor application into a selector: +-- tup = (a_1, ..., a_99) +-- x = case tup of ... +-- +mkSizeIs max n xs d | (n -# d) ># max = TooBig + | otherwise = SizeIs n xs d + +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) +conSizeN dc n + | 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, + -- which is the same as a lone variable; and hence 'v' will + -- always be replaced by (iBox x), where v is bound to iBox x. + -- + -- However, unboxed tuples count as size zero + -- I found occasions where we had + -- f x y z = case op# x y z of { s -> (# s, () #) } + -- and f wasn't getting inlined + +primOpSize op n_args + | not (primOpIsDupable op) = sizeN opt_UF_DearOp + | not (primOpOutOfLine op) = sizeN (2 - n_args) + -- Be very keen to inline simple primops. + -- We give a discount of 1 for each arg so that (op# x y z) costs 2. + -- We can't make it cost 1, else we'll inline let v = (op# x y z) + -- at every use of v, which is excessive. + -- + -- A good example is: + -- let x = +# p q in C {x} + -- Even though x get's an occurrence of 'many', its RHS looks cheap, + -- and there's a good chance it'll get inlined back into C's RHS. Urgh! + | otherwise = sizeOne buildSize = SizeIs (-2#) emptyBag 4# -- We really want to inline applications of build @@ -365,10 +404,12 @@ 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 { d -> SizeIs n vs (iUnbox d) } +lamScrutDiscount TooBig = TooBig \end{code} @@ -407,49 +448,25 @@ 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 -\end{code} - -@okToUnfoldInHifile@ is used when emitting unfolding info into an interface -file to determine whether an unfolding candidate really should be unfolded. -The predicate is needed to prevent @_casm_@s (+ lit-lits) from being emitted -into interface files. - -The reason for inlining expressions containing _casm_s into interface files -is that these fragments of C are likely to mention functions/#defines that -will be out-of-scope when inlined into another module. This is not an -unfixable problem for the user (just need to -#include the approp. header -file), but turning it off seems to the simplest thing to do. - -\begin{code} -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 (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 (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 +couldBeSmallEnoughToInline :: Int -> CoreExpr -> Bool +couldBeSmallEnoughToInline threshold rhs = case calcUnfoldingGuidance threshold rhs of + UnfoldNever -> False + other -> 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 + = False + +smallEnoughToInline :: Unfolding -> Bool +smallEnoughToInline (CoreUnfolding _ _ _ _ (UnfoldIfGoodArgs _ _ size _)) + = size <= opt_UF_UseThreshold +smallEnoughToInline other + = False \end{code} - %************************************************************************ %* * \subsection{callSiteInline} @@ -467,141 +484,142 @@ 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 +callSiteInline :: DynFlags + -> Bool -- True <=> the Id can be inlined -> Bool -- 'inline' note at call site + -> OccInfo -> Id -- The Id - -> [CoreExpr] -- Arguments + -> [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 args interesting_cont - = case getIdUnfolding id of { +callSiteInline dflags active_inline 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 -> Just unf_template ; + -- CompulsoryUnfolding => there is no top-level binding + -- for these things, so we must inline it. + -- Only a couple of primop-like things have + -- compulsory unfoldings (see MkId.lhs). + -- We don't allow them to be inactive + + CoreUnfolding unf_template is_top is_value is_cheap guidance -> let result | yes_or_no = Just unf_template | otherwise = Nothing - inline_prag = getInlinePragma id - arg_infos = map interestingArg val_args - val_args = filter isValArg args - - 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 - | black_listed = False + 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 + -- occurrences, because they won't all have been + -- caught by preInlineUnconditionally. In particular, + -- if the occurrence is once inside a lambda, and the + -- rhs is cheap but not a manifest lambda, then + -- pre-inline will not have inlined it for fear of + -- invalidating the occurrence info in the rhs. + + consider_safe once + -- 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 - | 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 args) || interesting_cont) - - | otherwise -- Occurs (textually) more than once, so look at its size + + | otherwise = case guidance of - UnfoldAlways -> True UnfoldNever -> False UnfoldIfGoodArgs n_vals_wanted arg_discounts size res_discount - | enough_args && size <= (n_vals_wanted + 1) - -- No size increase + + | 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) - -> 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 - n_args = length arg_infos - enough_args = n_args >= n_vals_wanted - really_interesting_cont | n_args < n_vals_wanted = False -- Too few args - | n_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))) + -- [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 + -- 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 + if dopt Opt_D_dump_inlinings dflags then pprTrace "Considering inlining" - (ppr id <+> vcat [text "black listed" <+> ppr black_listed, - text "inline prag:" <+> ppr inline_prag, + (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 "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 - text "Unfolding =" <+> pprCoreExpr unf_template - else empty]) + text "ANSWER =" <+> if yes_or_no then text "YES" else text "NO"]) result else -#endif result } --- An argument is interesting if it has *some* structure --- We are here trying to avoid unfolding a function that --- is applied only to variables that have no unfolding --- (i.e. they are probably lambda bound): f x y z --- There is little point in inlining f here. -interestingArg (Type _) = False -interestingArg (App fn (Type _)) = interestingArg fn -interestingArg (Var v) = hasSomeUnfolding (getIdUnfolding v) -interestingArg other = True - - computeDiscount :: Int -> [Int] -> Int -> [Bool] -> Bool -> Int computeDiscount n_vals_wanted arg_discounts res_discount arg_infos result_used -- 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 - -- *efficiency* to be gained (e.g. beta reductions, case reductions) + -- *size* whereas the discounts imply that there's some extra + -- *efficiency* to be gained (e.g. beta reductions, case reductions) -- by inlining. -- 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 * - fromInt (arg_discount + result_discount)) + fromIntegral (arg_discount + result_discount)) where arg_discount = sum (zipWith mk_arg_discount arg_discounts arg_infos) @@ -612,84 +630,3 @@ computeDiscount n_vals_wanted arg_discounts res_discount arg_infos result_used result_discount | result_used = res_discount -- Over-applied, or case scrut | otherwise = 0 \end{code} - - -%************************************************************************ -%* * -\subsection{Black-listing} -%* * -%************************************************************************ - -Inlining is controlled by the "Inline phase" number, which is set -by the per-simplification-pass '-finline-phase' flag. - -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. - -\begin{code} -blackListed :: IdSet -- Used in transformation rules - -> Maybe Int -- Inline phase - -> Id -> Bool -- True <=> blacklisted - --- The blackListed function sees whether a variable should *not* be --- 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 -\end{code} - - -SLPJ 95/04: Why @runST@ must be inlined very late: -\begin{verbatim} -f x = - runST ( \ s -> let - (a, s') = newArray# 100 [] s - (_, s'') = fill_in_array_or_something a x s' - in - freezeArray# a s'' ) -\end{verbatim} -If we inline @runST@, we'll get: -\begin{verbatim} -f x = let - (a, s') = newArray# 100 [] realWorld#{-NB-} - (_, s'') = fill_in_array_or_something a x s' - in - freezeArray# a s'' -\end{verbatim} -And now the @newArray#@ binding can be floated to become a CAF, which -is totally and utterly wrong: -\begin{verbatim} -f = let - (a, s') = newArray# 100 [] realWorld#{-NB-} -- YIKES!!! - in - \ x -> - let (_, s'') = fill_in_array_or_something a x s' in - freezeArray# a s'' -\end{verbatim} -All calls to @f@ will share a {\em single} array! - -Yet we do want to inline runST sometime, so we can avoid -needless code. Solution: black list it until the last moment. -