%
-% (c) The AQUA Project, Glasgow University, 1994-1996
+% (c) The AQUA Project, Glasgow University, 1994-1998
%
\section[CoreUnfold]{Core-syntax unfoldings}
The type @Unfolding@ sits ``above'' simply-Core-expressions
unfoldings, capturing ``higher-level'' things we know about a binding,
usually things that the simplifier found out (e.g., ``it's a
-literal''). In the corner of a @SimpleUnfolding@ unfolding, you will
+literal''). In the corner of a @CoreUnfolding@ unfolding, you will
find, unsurprisingly, a Core expression.
\begin{code}
-#include "HsVersions.h"
-
module CoreUnfold (
- SimpleUnfolding(..), Unfolding(..), UnfoldingGuidance(..), -- types
- UfExpr, RdrName, -- For closure (delete in 1.3)
+ Unfolding, UnfoldingGuidance, -- Abstract types
- FormSummary(..), mkFormSummary, whnfOrBottom, exprSmallEnoughToDup,
+ noUnfolding, mkTopUnfolding, mkUnfolding, mkCompulsoryUnfolding, seqUnfolding,
+ mkOtherCon, otherCons,
+ unfoldingTemplate, maybeUnfoldingTemplate,
+ isEvaldUnfolding, isValueUnfolding, isCheapUnfolding, isCompulsoryUnfolding,
+ hasUnfolding, hasSomeUnfolding, neverUnfold,
- noUnfolding, mkMagicUnfolding, mkUnfolding, getUnfoldingTemplate,
+ couldBeSmallEnoughToInline,
+ certainlyWillInline,
+ okToUnfoldInHiFile,
- smallEnoughToInline, couldBeSmallEnoughToInline, certainlySmallEnoughToInline,
- okToInline,
-
- calcUnfoldingGuidance
+ callSiteInline, blackListed
) where
-IMP_Ubiq()
-IMPORT_DELOOPER(IdLoop) -- for paranoia checking;
- -- and also to get mkMagicUnfoldingFun
-IMPORT_DELOOPER(PrelLoop) -- for paranoia checking
-
-import Bag ( emptyBag, unitBag, unionBags, Bag )
+#include "HsVersions.h"
-import CmdLineOpts ( opt_UnfoldingCreationThreshold,
- opt_UnfoldingUseThreshold,
- opt_UnfoldingConDiscount
- )
-import Constants ( uNFOLDING_CHEAP_OP_COST,
- uNFOLDING_DEAR_OP_COST,
- uNFOLDING_NOREP_LIT_COST
+import CmdLineOpts ( opt_UF_CreationThreshold,
+ opt_UF_UseThreshold,
+ opt_UF_FunAppDiscount,
+ opt_UF_KeenessFactor,
+ opt_UF_DearOp, opt_UnfoldCasms,
+ DynFlags, DynFlag(..), dopt
)
-import BinderInfo ( BinderInfo(..), FunOrArg, DuplicationDanger, InsideSCC, isDupDanger )
import CoreSyn
-import CoreUtils ( unTagBinders )
-import HsCore ( UfExpr )
-import RdrHsSyn ( RdrName )
+import PprCore ( pprCoreExpr )
import OccurAnal ( occurAnalyseGlobalExpr )
-import CoreUtils ( coreExprType )
-import CostCentre ( ccMentionsId )
-import Id ( idType, getIdArity, isBottomingId,
- SYN_IE(IdSet), GenId{-instances-} )
-import PrimOp ( primOpCanTriggerGC, fragilePrimOp, PrimOp(..) )
-import IdInfo ( ArityInfo(..), bottomIsGuaranteed )
-import Literal ( isNoRepLit, isLitLitLit )
-import Pretty
-import TyCon ( tyConFamilySize )
-import Type ( maybeAppDataTyConExpandingDicts )
-import UniqSet ( emptyUniqSet, unitUniqSet, mkUniqSet,
- addOneToUniqSet, unionUniqSets
+import CoreUtils ( exprIsValue, exprIsCheap, exprIsTrivial )
+import Id ( Id, idType, idFlavour, isId,
+ idSpecialisation, idInlinePragma, idUnfolding,
+ isPrimOpId_maybe
)
-import Usage ( SYN_IE(UVar) )
-import Util ( isIn, panic, assertPanic )
-
+import VarSet
+import Literal ( isLitLitLit, litIsDupable )
+import PrimOp ( PrimOp(..), primOpIsDupable, primOpOutOfLine, ccallIsCasm )
+import IdInfo ( InlinePragInfo(..), OccInfo(..), IdFlavour(..),
+ isNeverInlinePrag
+ )
+import Type ( isUnLiftedType )
+import PrelNames ( hasKey, buildIdKey, augmentIdKey )
+import Bag
+import FastTypes
+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
-
- | CoreUnfolding SimpleUnfolding
-
- | MagicUnfolding
- Unique -- Unique of the Id whose magic unfolding this is
- MagicUnfoldingFun
-
-
-data SimpleUnfolding
- = SimpleUnfolding -- An unfolding with redundant cached information
- FormSummary -- Tells whether the template is a WHNF or bottom
- UnfoldingGuidance -- Tells about the *size* of the template.
- SimplifiableCoreExpr -- Template
-
-
-noUnfolding = NoUnfolding
-
-mkUnfolding inline_me expr
- = CoreUnfolding (SimpleUnfolding
- (mkFormSummary expr)
- (calcUnfoldingGuidance inline_me opt_UnfoldingCreationThreshold expr)
- (occurAnalyseGlobalExpr expr))
-
-mkMagicUnfolding :: Unique -> Unfolding
-mkMagicUnfolding tag = MagicUnfolding tag (mkMagicUnfoldingFun tag)
-
-getUnfoldingTemplate :: Unfolding -> CoreExpr
-getUnfoldingTemplate (CoreUnfolding (SimpleUnfolding _ _ expr))
- = unTagBinders expr
-getUnfoldingTemplate other = panic "getUnfoldingTemplate"
-
-
-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 -- if "m" type args
- Int -- and "n" value args
- [Int] -- Discount if the argument is evaluated.
- -- (i.e., a simplification will definitely
- -- be possible). One elt of the list per *value* arg.
- Int -- The "size" of the unfolding; to be elaborated
- -- later. ToDo
-\end{code}
-
-\begin{code}
-instance Outputable UnfoldingGuidance where
- ppr sty UnfoldAlways = ppStr "_ALWAYS_"
--- ppr sty EssentialUnfolding = ppStr "_ESSENTIAL_" -- shouldn't appear in an iface
- ppr sty (UnfoldIfGoodArgs t v cs size)
- = ppCat [ppStr "_IF_ARGS_", ppInt t, ppInt v,
- if null cs -- always print *something*
- then ppChar 'X'
- else ppBesides (map (ppStr . show) cs),
- ppInt size ]
+mkTopUnfolding expr = mkUnfolding True {- Top level -} expr
+
+mkUnfolding top_lvl expr
+ = CoreUnfolding (occurAnalyseGlobalExpr expr)
+ top_lvl
+ (exprIsValue expr)
+ -- Already evaluated
+
+ (exprIsCheap expr)
+ -- OK to inline inside a lambda
+
+ (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}
%************************************************************************
%* *
-\subsection{Figuring out things about expressions}
+\subsection{The UnfoldingGuidance type}
%* *
%************************************************************************
\begin{code}
-data FormSummary
- = VarForm -- Expression is a variable (or scc var, etc)
- | ValueForm -- Expression is a value: i.e. a value-lambda,constructor, or literal
- | BottomForm -- Expression is guaranteed to be bottom. We're more gung
- -- ho about inlining such things, because it can't waste work
- | OtherForm -- Anything else
-
-instance Outputable FormSummary where
- ppr sty VarForm = ppStr "Var"
- ppr sty ValueForm = ppStr "Value"
- ppr sty BottomForm = ppStr "Bot"
- ppr sty OtherForm = ppStr "Other"
-
-mkFormSummary ::GenCoreExpr bndr Id tyvar uvar -> FormSummary
-
-mkFormSummary expr
- = go (0::Int) expr -- The "n" is the number of (value) arguments so far
- where
- go n (Lit _) = ASSERT(n==0) ValueForm
- go n (Con _ _) = ASSERT(n==0) ValueForm
- go n (Prim _ _) = OtherForm
- go n (SCC _ e) = go n e
- go n (Coerce _ _ e) = go n e
- go n (Let _ e) = OtherForm
- go n (Case _ _) = OtherForm
-
- go 0 (Lam (ValBinder x) e) = ValueForm -- NB: \x.bottom /= bottom!
- go n (Lam (ValBinder x) e) = go (n-1) e -- Applied lambda
- go n (Lam other_binder e) = go n e
-
- go n (App fun arg) | isValArg arg = go (n+1) fun
- go n (App fun other_arg) = go n fun
-
- go n (Var f) | isBottomingId f = BottomForm
- go 0 (Var f) = VarForm
- go n (Var f) = case getIdArity f of
- ArityExactly a | n < a -> ValueForm
- ArityAtLeast a | n < a -> ValueForm
- other -> OtherForm
-
-whnfOrBottom :: GenCoreExpr bndr Id tyvar uvar -> Bool
-whnfOrBottom e = case mkFormSummary e of
- VarForm -> True
- ValueForm -> True
- BottomForm -> True
- OtherForm -> False
-\end{code}
-
-
-\begin{code}
-exprSmallEnoughToDup (Con _ _) = True -- Could check # of args
-exprSmallEnoughToDup (Prim op _) = not (fragilePrimOp op) -- Could check # of args
-exprSmallEnoughToDup (Lit lit) = not (isNoRepLit lit)
-exprSmallEnoughToDup expr
- = case (collectArgs expr) of { (fun, _, _, vargs) ->
- case fun of
- Var v | length vargs == 0 -> True
- _ -> False
- }
-
-{- LATER:
-WAS: MORE CLEVER:
-exprSmallEnoughToDup expr -- for now, just: <var> applied to <args>
- = case (collectArgs expr) of { (fun, _, _, vargs) ->
- case fun of
- Var v -> v /= buildId
- && v /= augmentId
- && length vargs <= 6 -- or 10 or 1 or 4 or anything smallish.
- _ -> False
- }
--}
+instance Outputable UnfoldingGuidance where
+ ppr UnfoldNever = ptext SLIT("NEVER")
+ ppr (UnfoldIfGoodArgs v cs size discount)
+ = hsep [ ptext SLIT("IF_ARGS"), int v,
+ brackets (hsep (map int cs)),
+ int size,
+ int discount ]
\end{code}
-Question (ADR): What is the above used for? Is a _ccall_ really small
-enough?
-%************************************************************************
-%* *
-\subsection[calcUnfoldingGuidance]{Calculate ``unfolding guidance'' for an expression}
-%* *
-%************************************************************************
\begin{code}
calcUnfoldingGuidance
- :: Bool -- True <=> there's an INLINE pragma on this thing
- -> Int -- bomb out if size gets bigger than this
+ :: Int -- bomb out if size gets bigger than this
-> CoreExpr -- expression to look at
-> UnfoldingGuidance
+calcUnfoldingGuidance bOMB_OUT_SIZE expr
+ = case collect_val_bndrs expr of { (inline, val_binders, body) ->
+ let
+ 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.
-calcUnfoldingGuidance True bOMB_OUT_SIZE expr = UnfoldAlways -- Always inline if the INLINE pragma says so
-
-calcUnfoldingGuidance False bOMB_OUT_SIZE expr
- = let
- (use_binders, ty_binders, val_binders, body) = collectBinders expr
in
case (sizeExpr bOMB_OUT_SIZE val_binders body) of
- Nothing -> UnfoldNever
-
- Just (size, cased_args)
- -> let
- uf = UnfoldIfGoodArgs
- (length ty_binders)
- (length val_binders)
+ 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
+ n_val_binders
(map discount_for val_binders)
- size
-
- discount_for b
- | is_data && b `is_elem` cased_args = tyConFamilySize tycon
- | otherwise = 0
- where
- (is_data, tycon)
- = --trace "CoreUnfold.getAppDataTyConExpandingDicts:1" $
- case (maybeAppDataTyConExpandingDicts (idType b)) of
- Nothing -> (False, panic "discount")
- Just (tc,_,_) -> (True, tc)
- in
- -- pprTrace "calcUnfold:" (ppAbove (ppr PprDebug uf) (ppr PprDebug expr))
- uf
+ final_size
+ (iBox scrut_discount)
+ where
+ 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
- is_elem = isIn "calcUnfoldingGuidance"
+ 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}
-> [Id] -- Arguments; we're interested in which of these
-- get case'd
-> CoreExpr
- -> Maybe (Int, -- Size
- [Id] -- Subset of args which are cased
- )
+ -> ExprSize
-sizeExpr bOMB_OUT_SIZE args expr
+sizeExpr bOMB_OUT_SIZE top_args expr
= size_up expr
where
- size_up (Var v) = sizeOne
- size_up (App fun arg) = size_up fun `addSize` size_up_arg arg
- size_up (Lit lit) = if isNoRepLit lit
- then sizeN uNFOLDING_NOREP_LIT_COST
- else sizeOne
+ size_up (Type t) = sizeZero -- Types cost nothing
+ size_up (Var v) = sizeOne
--- I don't understand this hack so I'm removing it! SLPJ Nov 96
--- size_up (SCC _ (Con _ _)) = Nothing -- **** HACK *****
+ size_up (Note _ body) = size_up body -- Notes cost nothing
- size_up (SCC lbl body) = size_up body -- SCCs cost nothing
- size_up (Coerce _ _ body) = size_up body -- Coercions cost nothing
+ size_up (App fun (Type t)) = size_up fun
+ size_up (App fun arg) = size_up_app fun [arg]
- size_up (Con con args) = -- 1 + # of val args
- sizeN (1 + numValArgs args)
- size_up (Prim op args) = sizeN op_cost -- NB: no charge for PrimOp args
- where
- op_cost = if primOpCanTriggerGC op
- then uNFOLDING_DEAR_OP_COST
- -- these *tend* to be more expensive;
- -- number chosen to avoid unfolding (HACK)
- else uNFOLDING_CHEAP_OP_COST
-
- size_up expr@(Lam _ _)
- = let
- (uvars, tyvars, args, body) = collectBinders expr
- in
- size_up body `addSizeN` length 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 = lamScrutDiscount (size_up e `addSizeN` 1)
+ | otherwise = size_up e
size_up (Let (NonRec binder rhs) body)
- = size_up rhs
- `addSize`
- size_up body
- `addSizeN`
- 1
+ = nukeScrutDiscount (size_up rhs) `addSize`
+ size_up body `addSizeN`
+ (if isUnLiftedType (idType binder) then 0 else 1)
+ -- For the allocation
+ -- If the binder has an unlifted type there is no allocation
size_up (Let (Rec pairs) body)
- = foldr addSize sizeZero [size_up rhs | (_,rhs) <- pairs]
- `addSize`
- size_up body
- `addSizeN`
- length pairs
-
- size_up (Case scrut alts)
- = size_up_scrut scrut
- `addSize`
- size_up_alts (coreExprType scrut) alts
- -- We charge for the "case" itself in "size_up_alts"
+ = nukeScrutDiscount rhs_size `addSize`
+ size_up body `addSizeN`
+ length pairs -- For the allocation
+ where
+ rhs_size = foldr (addSize . size_up . snd) sizeZero pairs
+
+ 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
+
+
+ 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
+ | 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
+ --
+ -- 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
+ -- (See comments about wrappers with Case)
------------
- size_up_arg arg = if isValArg arg then sizeOne else sizeZero{-it's free-}
+ -- 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
------------
- size_up_alts scrut_ty (AlgAlts alts deflt)
- = foldr (addSize . size_alg_alt) (size_up_deflt deflt) alts
- `addSizeN` (if is_data then tyConFamilySize tycon else 1{-??-})
- -- NB: we charge N for an alg. "case", where N is
- -- the number of constructors in the thing being eval'd.
- -- (You'll eventually get a "discount" of N if you
- -- think the "case" is likely to go away.)
+ -- 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) m
+ | n_tot ># (iUnbox bOMB_OUT_SIZE) = TooBig
+ | otherwise = SizeIs n_tot xs d
where
- size_alg_alt (con,args,rhs) = size_up rhs
- -- Don't charge for args, so that wrappers look cheap
-
- (is_data,tycon)
- = --trace "CoreUnfold.getAppDataTyConExpandingDicts:2" $
- case (maybeAppDataTyConExpandingDicts scrut_ty) of
- Nothing -> (False, panic "size_up_alts")
- Just (tc,_,_) -> (True, tc)
-
- size_up_alts _ (PrimAlts alts deflt)
- = foldr (addSize . size_prim_alt) (size_up_deflt deflt) alts
- -- *no charge* for a primitive "case"!
+ n_tot = n +# iUnbox m
+
+ addSize TooBig _ = TooBig
+ addSize _ TooBig = TooBig
+ addSize (SizeIs n1 xs d1) (SizeIs n2 ys d2)
+ | n_tot ># (iUnbox bOMB_OUT_SIZE) = TooBig
+ | otherwise = SizeIs n_tot xys d_tot
where
- size_prim_alt (lit,rhs) = size_up rhs
-
- ------------
- size_up_deflt NoDefault = sizeZero
- size_up_deflt (BindDefault binder rhs) = size_up rhs
-
- ------------
- -- Scrutinees. There are two things going on here.
- -- First, we want to record if we're case'ing an argument
- -- Second, we want to charge nothing for the srutinee if it's just
- -- a variable. That way wrapper-like things look cheap.
- size_up_scrut (Var v) | v `is_elem` args = Just (0, [v])
- | otherwise = Just (0, [])
- size_up_scrut other = size_up other
+ n_tot = n1 +# n2
+ d_tot = d1 +# d2
+ xys = xs `unionBags` ys
+\end{code}
- is_elem :: Id -> [Id] -> Bool
- is_elem = isIn "size_up_scrut"
+Code for manipulating sizes
- ------------
- sizeZero = Just (0, [])
- sizeOne = Just (1, [])
- sizeN n = Just (n, [])
-
- addSizeN Nothing _ = Nothing
- addSizeN (Just (n, xs)) m
- | tot < bOMB_OUT_SIZE = Just (tot, xs)
- | otherwise = Nothing
- where
- tot = n+m
+\begin{code}
- addSize Nothing _ = Nothing
- addSize _ Nothing = Nothing
- addSize (Just (n, xs)) (Just (m, ys))
- | tot < bOMB_OUT_SIZE = Just (tot, xys)
- | otherwise = Nothing
- where
- tot = n+m
- xys = xs ++ ys
+data ExprSize = TooBig
+ | 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
+
+
+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)
+sizeTwo = SizeIs (_ILIT 2) emptyBag (_ILIT 0)
+sizeN n = SizeIs (iUnbox n) emptyBag (_ILIT 0)
+conSizeN n = 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.
+
+primOpSize op n_args
+ | not (primOpIsDupable op) = sizeN opt_UF_DearOp
+ | not (primOpOutOfLine op) = sizeN (1 - 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 1.
+ -- I found occasions where we had
+ -- f x y z = case op# x y z of { s -> (# s, () #) }
+ -- and f wasn't getting inlined
+ | otherwise = sizeOne
+
+buildSize = SizeIs (-2#) emptyBag 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
+ -- very like a constructor. We don't bother to check that the
+ -- build is saturated (it usually is). The "-2" discounts for the \c n,
+ -- The "4" is rather arbitrary.
+
+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
+
+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}
+
%************************************************************************
%* *
\subsection[considerUnfolding]{Given all the info, do (not) do the unfolding}
a single integer. (3)~An ``argument info'' vector. For this, what we
have at the moment is a Boolean per argument position that says, ``I
will look with great favour on an explicit constructor in this
-position.''
+position.'' (4)~The ``discount'' to subtract if the expression
+is being scrutinised.
Assuming we have enough type- and value arguments (if not, we give up
immediately), then we see if the ``discounted size'' is below some
hands, we get a (again, semi-arbitrary) discount [proportion to the
number of constructors in the type being scrutinized].
-\begin{code}
-smallEnoughToInline :: [Bool] -- Evaluated-ness of value arguments
- -> UnfoldingGuidance
- -> Bool -- True => unfold it
-
-smallEnoughToInline _ UnfoldAlways = True
-smallEnoughToInline _ UnfoldNever = False
-smallEnoughToInline arg_is_evald_s
- (UnfoldIfGoodArgs m_tys_wanted n_vals_wanted discount_vec size)
- = enough_args n_vals_wanted arg_is_evald_s &&
- discounted_size <= opt_UnfoldingUseThreshold
- where
- enough_args 0 evals = True
- enough_args n [] = False
- enough_args n (e:es) = enough_args (n-1) es
- -- NB: don't take the length of arg_is_evald_s because when
- -- called from couldBeSmallEnoughToInline it is infinite!
-
- discounted_size = size - sum (zipWith arg_discount discount_vec arg_is_evald_s)
-
- arg_discount no_of_constrs is_evald
- | is_evald = 1 + no_of_constrs * opt_UnfoldingConDiscount
- | otherwise = 1
-\end{code}
+If we're in the context of a scrutinee ( \tr{(case <expr > of A .. -> ...;.. )})
+and the expression in question will evaluate to a constructor, we use
+the computed discount size *for the result only* rather than
+computing the argument discounts. Since we know the result of
+the expression is going to be taken apart, discounting its size
+is more accurate (see @sizeExpr@ above for how this discount size
+is computed).
We use this one to avoid exporting inlinings that we ``couldn't possibly
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 guidance = smallEnoughToInline (repeat True) guidance
+couldBeSmallEnoughToInline :: Int -> CoreExpr -> Bool
+couldBeSmallEnoughToInline threshold rhs = case calcUnfoldingGuidance threshold rhs of
+ UnfoldNever -> False
+ other -> True
-certainlySmallEnoughToInline :: UnfoldingGuidance -> Bool
-certainlySmallEnoughToInline guidance = smallEnoughToInline (repeat False) guidance
+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}
-Predicates
-~~~~~~~~~~
+@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}
-okToInline
- :: FormSummary -- What the thing to be inlined is like
- -> BinderInfo -- How the thing to be inlined occurs
- -> Bool -- True => it's small enough to inline
- -> Bool -- True => yes, inline it
-
--- Always inline bottoms
-okToInline BottomForm occ_info small_enough
- = True -- Unless one of the type args is unboxed??
- -- This used to be checked for, but I can't
- -- see why so I've left it out.
-
--- A WHNF can be inlined if it occurs once, or is small
-okToInline form occ_info small_enough
- | is_whnf_form form
- = small_enough || one_occ
+okToUnfoldInHiFile :: CoreExpr -> Bool
+okToUnfoldInHiFile e = opt_UnfoldCasms || go e
where
- one_occ = case occ_info of
- OneOcc _ _ _ n_alts _ -> n_alts <= 1
- other -> False
-
- is_whnf_form VarForm = True
- is_whnf_form ValueForm = True
- is_whnf_form other = False
-
--- A non-WHNF can be inlined if it doesn't occur inside a lambda,
--- and occurs exactly once or
--- occurs once in each branch of a case and is small
-okToInline OtherForm (OneOcc _ dup_danger _ n_alts _) small_enough
- = not (isDupDanger dup_danger) && (n_alts <= 1 || small_enough)
+ -- Race over an expression looking for CCalls..
+ 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)) &&
+ 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 ccall) = not (ccallIsCasm ccall)
+ okToUnfoldPrimOp _ = True
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsection{callSiteInline}
+%* *
+%************************************************************************
+
+This is the key function. It decides whether to inline a variable at a call site
+
+callSiteInline is used at call sites, so it is a bit more generous.
+It's a very important function that embodies lots of heuristics.
+A non-WHNF can be inlined if it doesn't occur inside a lambda,
+and occurs exactly once or
+ occurs once in each branch of a case and is small
-okToInline form any_occ small_enough = False
+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 :: DynFlags
+ -> 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 dflags black_listed inline_call occ id arg_infos interesting_cont
+ = case idUnfolding id of {
+ NoUnfolding -> Nothing ;
+ 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
+
+ n_val_args = length arg_infos
+
+ 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:
+ --
+ -- 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
+ UnfoldNever -> False ;
+ UnfoldIfGoodArgs n_vals_wanted arg_discounts size res_discount
+
+ | enough_args && size <= (n_vals_wanted + 1)
+ -- No size increase
+ -- Size of call is n_vals_wanted (+1 for the function)
+ -> 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 dopt Opt_D_dump_inlinings dflags then
+ pprTrace "Considering inlining"
+ (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 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])
+ result
+ else
+#endif
+ result
+ }
+
+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)
+ -- 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).
+ = 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))
+ where
+ arg_discount = sum (zipWith mk_arg_discount arg_discounts arg_infos)
+
+ 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}
+
+
+%************************************************************************
+%* *
+\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.
+
+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<n *and* foo appears on LHS of rule
+ INLINE foo phase is Just p *and* foo appears on LHS of rule
+ NOINLINE n foo phase is Just p *and* (p<n *or* foo appears on LHS of rule)
+ NOINLINE foo always
+(most black listing, least inlining)
+
+\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.
+
+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}
+
+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.
+
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