\begin{code}
module CoreUnfold (
- Unfolding(..), UnfoldingGuidance(..), -- types
+ Unfolding, UnfoldingGuidance, -- Abstract types
- noUnfolding, mkMagicUnfolding, mkUnfolding, getUnfoldingTemplate,
- isEvaldUnfolding, hasUnfolding,
+ noUnfolding, mkTopUnfolding, mkUnfolding, mkCompulsoryUnfolding, seqUnfolding,
+ evaldUnfolding, mkOtherCon, otherCons,
+ unfoldingTemplate, maybeUnfoldingTemplate,
+ isEvaldUnfolding, isValueUnfolding, isCheapUnfolding, isCompulsoryUnfolding,
+ hasUnfolding, hasSomeUnfolding, neverUnfold,
- smallEnoughToInline, unfoldAlways, couldBeSmallEnoughToInline,
- certainlySmallEnoughToInline,
- okToUnfoldInHiFile,
+ couldBeSmallEnoughToInline,
+ certainlyWillInline,
- calcUnfoldingGuidance
+ callSiteInline
) where
#include "HsVersions.h"
-import {-# SOURCE #-} MagicUFs ( MagicUnfoldingFun, mkMagicUnfoldingFun )
-
-import CmdLineOpts ( opt_UnfoldingCreationThreshold,
- opt_UnfoldingUseThreshold,
- opt_UnfoldingConDiscount,
- opt_UnfoldingKeenessFactor,
- opt_UnfoldCasms, opt_PprStyle_Debug
- )
-import Constants ( uNFOLDING_CHEAP_OP_COST,
- uNFOLDING_DEAR_OP_COST,
- uNFOLDING_NOREP_LIT_COST
+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 OccurAnal ( occurAnalyseGlobalExpr )
-import CoreUtils ( coreExprType, exprIsTrivial, mkFormSummary,
- FormSummary(..) )
-import Id ( Id, idType, isId )
-import Const ( Con(..), isLitLitLit )
-import PrimOp ( PrimOp(..), primOpOutOfLine )
-import IdInfo ( ArityInfo(..), InlinePragInfo(..) )
-import TyCon ( tyConFamilySize )
-import Type ( splitAlgTyConApp_maybe )
-import Const ( isNoRepLit )
-import Unique ( Unique )
-import Util ( isIn )
+import PprCore ( pprCoreExpr )
+import OccurAnal ( occurAnalyseExpr )
+import CoreUtils ( exprIsValue, exprIsCheap, exprIsTrivial )
+import Id ( Id, idType, isId,
+ idUnfolding, globalIdDetails
+ )
+import DataCon ( isUnboxedTupleCon )
+import Literal ( litSize )
+import PrimOp ( primOpIsDupable, primOpOutOfLine )
+import IdInfo ( OccInfo(..), GlobalIdDetails(..) )
+import Type ( isUnLiftedType )
+import PrelNames ( hasKey, buildIdKey, augmentIdKey )
+import Bag
+import FastTypes
import Outputable
+import Util
+
+#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
- FormSummary -- Tells whether the template is a WHNF or bottom
- UnfoldingGuidance -- Tells about the *size* of the template.
- CoreExpr -- Template; binder-info is correct
-
- | MagicUnfolding
- Unique -- Unique of the Id whose magic unfolding this is
- MagicUnfoldingFun
+mkTopUnfolding expr = mkUnfolding True {- Top level -} expr
+
+mkUnfolding top_lvl expr
+ = CoreUnfolding (occurAnalyseExpr 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 (occurAnalyseExpr expr)
\end{code}
-\begin{code}
-noUnfolding = NoUnfolding
-
-mkUnfolding expr
- = let
- -- strictness mangling (depends on there being no CSE)
- ufg = calcUnfoldingGuidance opt_UnfoldingCreationThreshold expr
- occ = occurAnalyseGlobalExpr expr
- in
- CoreUnfolding (mkFormSummary expr) ufg occ
-
-mkMagicUnfolding :: Unique -> Unfolding
-mkMagicUnfolding tag = MagicUnfolding tag (mkMagicUnfoldingFun tag)
-
-getUnfoldingTemplate :: Unfolding -> CoreExpr
-getUnfoldingTemplate (CoreUnfolding _ _ expr) = expr
-getUnfoldingTemplate other = panic "getUnfoldingTemplate"
-
-isEvaldUnfolding :: Unfolding -> Bool
-isEvaldUnfolding (OtherCon _) = True
-isEvaldUnfolding (CoreUnfolding ValueForm _ expr) = True
-isEvaldUnfolding other = False
-hasUnfolding :: Unfolding -> Bool
-hasUnfolding NoUnfolding = False
-hasUnfolding 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 -- 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
-
- 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.)
-
-unfoldAlways :: UnfoldingGuidance -> Bool
-unfoldAlways UnfoldAlways = True
-unfoldAlways other = False
-\end{code}
+%************************************************************************
+%* *
+\subsection{The UnfoldingGuidance type}
+%* *
+%************************************************************************
\begin{code}
instance Outputable UnfoldingGuidance where
- ppr UnfoldAlways = ptext SLIT("_ALWAYS_")
- ppr (UnfoldIfGoodArgs t v cs size discount)
- = hsep [ptext SLIT("_IF_ARGS_"), int t, int v,
- if null cs -- always print *something*
- then char 'X'
- else hcat (map (text . show) cs),
+ 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}
-%************************************************************************
-%* *
-\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 collectTyAndValBinders expr of { (ty_binders, val_binders, body) ->
- case (sizeExpr bOMB_OUT_SIZE val_binders body) of
+ = case collect_val_bndrs expr of { (inline, val_binders, body) ->
+ let
+ n_val_binders = length val_binders
- TooBig -> UnfoldNever
+ 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 (iUnbox bOMB_OUT_SIZE) val_binders body) of
+
+ 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 ty_binders)
- (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
- | otherwise
- = if is_data
- then tyConFamilySize tycon * num_cases
- else num_cases -- prim cases are pretty cheap
-
- where
- (is_data, tycon)
- = case (splitAlgTyConApp_maybe (idType b)) of
- Nothing -> (False, panic "discount")
- Just (tc,_,_) -> (True, tc)
- num_cases = length (filter (==b) cased_args)
+ 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 (Note _ body) = size_up body -- Notes cost nothing
- size_up (Var v) = sizeOne
- size_up (App fun arg) = size_up fun `addSize` size_up arg
+ size_up (Type t) = sizeZero -- Types cost nothing
+ size_up (Var v) = sizeOne
+
+ 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 (Con con args) = foldr (addSize . size_up)
- (size_up_con con (valArgCount args))
- args
+ size_up (Note _ body) = size_up body -- Other notes cost nothing
- size_up (Lam b e) | isId b = size_up e `addSizeN` 1
+ size_up (App fun (Type t)) = size_up fun
+ size_up (App fun arg) = size_up_app fun [arg]
+
+ size_up (Lit lit) = sizeN (litSize lit)
+
+ size_up (Lam b e) | isId b = lamScrutDiscount (size_up e `addSizeN` 1)
| otherwise = size_up e
size_up (Let (NonRec binder rhs) body)
= nukeScrutDiscount (size_up rhs) `addSize`
size_up body `addSizeN`
- 1 -- For the allocation
+ (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)
= nukeScrutDiscount rhs_size `addSize`
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 `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
+ | 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 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) nv | isNoRepLit lit = sizeN uNFOLDING_NOREP_LIT_COST
- | otherwise = sizeOne
-
- size_up_con (DataCon dc) n_val_args = conSizeN n_val_args
-
- size_up_con (PrimOp op) nv = sizeN op_cost
- where
- op_cost = if primOpOutOfLine op
- then uNFOLDING_DEAR_OP_COST
- -- these *tend* to be more expensive;
- -- number chosen to avoid unfolding (HACK)
- else uNFOLDING_CHEAP_OP_COST
-
- ------------
- -- We want to record if we're case'ing 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"
+ -- 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
------------
-- 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 ++ 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
- [Id] -- Arguments cased herein
- Int# -- Size to subtract if result is scrutinised
- -- by a case expression
-
-sizeZero = SizeIs 0# [] 0#
-sizeOne = SizeIs 1# [] 0#
-sizeN (I# n) = SizeIs n [] 0#
-conSizeN (I# n) = SizeIs 0# [] n -- We don't count 1 for the constructor because we're
- -- quite keen to get constructors into the open
-scrutArg v = SizeIs 0# [v] 0#
-
+ | 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
+ -- 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}
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}
-smallEnoughToInline :: Id -- The function (trace msg only)
- -> [Bool] -- Evaluated-ness of value arguments
- -- ** May be infinite in don't care cases **
- -- see couldBeSmallEnoughToInline etc
- -> Bool -- Result is scrutinised
- -> UnfoldingGuidance
- -> Bool -- True => unfold it
-
-smallEnoughToInline _ _ _ UnfoldAlways = True
-smallEnoughToInline _ _ _ UnfoldNever = False
-smallEnoughToInline id arg_evals result_is_scruted
- (UnfoldIfGoodArgs m_tys_wanted n_vals_wanted discount_vec size scrut_discount)
- | fun_with_no_args
+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
-
- | (size - discount) > opt_UnfoldingUseThreshold
- = if opt_PprStyle_Debug then
- pprTrace " too big:" stuff False
- else
- False
+\end{code}
- | otherwise -- All right!
- = if opt_PprStyle_Debug then
- pprTrace " small enough:" stuff True
- else
- True
+%************************************************************************
+%* *
+\subsection{callSiteInline}
+%* *
+%************************************************************************
- where
- stuff = braces (ppr id <+> ppr (take 10 arg_evals) <+> ppr result_is_scruted <+>
- ppr size <+> ppr discount)
+This is the key function. It decides whether to inline a variable at a call site
- fun_with_no_args = n_vals_wanted > 0 && null arg_evals
- -- A *function* with *no* value args => don't unfold
- -- Otherwise it's ok to try
+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
- -- We multiple the raw discounts (args_discount and result_discount)
+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 can be inlined
+ -> 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 active_inline inline_call occ id arg_infos interesting_cont
+ = case idUnfolding id of {
+ NoUnfolding -> Nothing ;
+ 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
+
+ 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
+
+ -- Occurs once in one branch. These are deal with by
+ -- preInlineUnconditionally, so we ignore them here:
+ OneOcc _ True _ -> False
+
+ OneOcc in_lam False _ -> (not in_lam || is_cheap) && consider_safe True
+ other -> is_cheap && consider_safe False
+
+ 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
+
+ | otherwise
+ = case guidance of
+ UnfoldNever -> False
+ UnfoldIfGoodArgs n_vals_wanted arg_discounts size res_discount
+
+ | enough_args && size <= (n_vals_wanted + 1)
+ -- Inline unconditionally if there no size increase
+ -- Size of call is n_vals_wanted (+1 for the function)
+ -> 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
+ if dopt Opt_D_dump_inlinings dflags then
+ pprTrace "Considering inlining"
+ (ppr id <+> vcat [text "active:" <+> ppr active_inline,
+ text "occ info:" <+> ppr occ,
+ text "arg infos" <+> ppr arg_infos,
+ text "interesting continuation" <+> ppr interesting_cont,
+ text "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"])
+ result
+ else
+ 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)
+ -- *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 *
+ fromIntegral (arg_discount + result_discount))
+ where
+ arg_discount = sum (zipWith mk_arg_discount arg_discounts arg_infos)
- -- NB: we never take the length of arg_evals because it might be infinite
- discount :: Int
- discount = length (take n_vals_wanted arg_evals) +
- round (opt_UnfoldingKeenessFactor *
- fromInt (arg_discount + result_discount))
-
- arg_discount = sum (zipWith mk_arg_discount discount_vec arg_evals)
- result_discount = mk_result_discount (drop n_vals_wanted arg_evals)
-
- mk_arg_discount no_of_constrs is_evald
- | is_evald = no_of_constrs * opt_UnfoldingConDiscount
- | otherwise = 0
-
- mk_result_discount extra_args
- | not (null extra_args) || result_is_scruted = scrut_discount -- Over-applied, or case scrut
- | otherwise = 0
-\end{code}
-
-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 :: Id -> UnfoldingGuidance -> Bool
-couldBeSmallEnoughToInline id guidance = smallEnoughToInline id (repeat True) True guidance
-
-certainlySmallEnoughToInline :: Id -> UnfoldingGuidance -> Bool
-certainlySmallEnoughToInline id guidance = smallEnoughToInline id (repeat False) False guidance
-\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.
+ mk_arg_discount discount is_evald | is_evald = discount
+ | otherwise = 0
-\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
+ -- 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}
projects / ghc-hetmet.git / blobdiff