%
+% (c) The University of Glasgow 2006
% (c) The AQUA Project, Glasgow University, 1994-1998
%
-\section[CoreUnfold]{Core-syntax unfoldings}
+
+Core-syntax unfoldings
Unfoldings (which can travel across module boundaries) are in Core
syntax (namely @CoreExpr@s).
module CoreUnfold (
Unfolding, UnfoldingGuidance, -- Abstract types
- noUnfolding, mkTopUnfolding, mkUnfolding, mkCompulsoryUnfolding, seqUnfolding,
- evaldUnfolding, mkOtherCon, otherCons,
- unfoldingTemplate, maybeUnfoldingTemplate,
- isEvaldUnfolding, isValueUnfolding, isCheapUnfolding, isCompulsoryUnfolding,
- hasUnfolding, hasSomeUnfolding, neverUnfold,
+ noUnfolding, mkImplicitUnfolding,
+ mkTopUnfolding, mkUnfolding,
+ mkInlineRule, mkWwInlineRule,
+ mkCompulsoryUnfolding,
couldBeSmallEnoughToInline,
certainlyWillInline, smallEnoughToInline,
- callSiteInline
- ) where
+ callSiteInline, CallCtxt(..)
-#include "HsVersions.h"
+ ) where
-import StaticFlags ( opt_UF_CreationThreshold, opt_UF_UseThreshold,
- opt_UF_FunAppDiscount, opt_UF_KeenessFactor,
- opt_UF_DearOp,
- )
-import DynFlags ( DynFlags, DynFlag(..), dopt )
+import StaticFlags
+import DynFlags
import CoreSyn
import PprCore () -- Instances
-import OccurAnal ( occurAnalyseExpr )
-import CoreUtils ( exprIsHNF, exprIsCheap, exprIsTrivial )
-import Id ( Id, idType, isId,
- idUnfolding, globalIdDetails
- )
-import DataCon ( isUnboxedTupleCon )
-import Literal ( litSize )
-import PrimOp ( primOpIsDupable, primOpOutOfLine )
-import IdInfo ( GlobalIdDetails(..) )
-import Type ( isUnLiftedType )
-import PrelNames ( hasKey, buildIdKey, augmentIdKey )
+import OccurAnal
+import CoreSubst ( emptySubst, substTy, extendIdSubst, extendTvSubst
+ , lookupIdSubst, substBndr, substBndrs, substRecBndrs )
+import CoreUtils
+import Id
+import DataCon
+import Literal
+import PrimOp
+import IdInfo
+import BasicTypes ( Arity )
+import Type hiding( substTy, extendTvSubst )
+import Maybes
+import PrelNames
import Bag
import FastTypes
+import FastString
import Outputable
-#if __GLASGOW_HASKELL__ >= 404
-import GLAEXTS ( Int# )
-#endif
\end{code}
%************************************************************************
\begin{code}
+mkTopUnfolding :: CoreExpr -> Unfolding
mkTopUnfolding expr = mkUnfolding True {- Top level -} expr
-mkUnfolding top_lvl expr
- = CoreUnfolding (occurAnalyseExpr expr)
- top_lvl
-
+mkImplicitUnfolding :: CoreExpr -> Unfolding
+-- For implicit Ids, do a tiny bit of optimising first
+mkImplicitUnfolding expr
+ = CoreUnfolding (simpleOptExpr expr)
+ True
(exprIsHNF expr)
- -- Already evaluated
-
(exprIsCheap expr)
- -- OK to inline inside a lambda
-
(calcUnfoldingGuidance opt_UF_CreationThreshold expr)
+
+mkInlineRule :: CoreExpr -> Arity -> Unfolding
+mkInlineRule expr arity
+ = InlineRule { uf_tmpl = simpleOptExpr expr,
+ uf_is_top = True, -- Conservative; this gets set more
+ -- accuately by the simplifier (slight hack)
+ -- in SimplEnv.substUnfolding
+ uf_arity = arity,
+ uf_is_value = exprIsHNF expr,
+ uf_worker = Nothing }
+
+mkWwInlineRule :: CoreExpr -> Arity -> Id -> Unfolding
+mkWwInlineRule expr arity wkr
+ = InlineRule { uf_tmpl = simpleOptExpr expr,
+ uf_is_top = True, -- Conservative; see mkInlineRule
+ uf_arity = arity,
+ uf_is_value = exprIsHNF expr,
+ uf_worker = Just wkr }
+
+mkUnfolding :: Bool -> CoreExpr -> Unfolding
+mkUnfolding top_lvl expr
+ = CoreUnfolding { uf_tmpl = occurAnalyseExpr expr,
+ uf_is_top = top_lvl,
+ uf_is_value = exprIsHNF expr,
+ uf_is_cheap = exprIsCheap expr,
+ uf_guidance = 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
-- This can occasionally mean that the guidance is very pessimistic;
-- it gets fixed up next round
-instance Outputable Unfolding where
- ppr NoUnfolding = ptext SLIT("No unfolding")
- ppr (OtherCon cs) = ptext SLIT("OtherCon") <+> ppr cs
- ppr (CompulsoryUnfolding e) = ptext SLIT("Compulsory") <+> ppr e
- ppr (CoreUnfolding e top hnf cheap g)
- = ptext SLIT("Unf") <+> sep [ppr top <+> ppr hnf <+> ppr cheap <+> ppr g,
- ppr e]
-
+mkCompulsoryUnfolding :: CoreExpr -> Unfolding
mkCompulsoryUnfolding expr -- Used for things that absolutely must be unfolded
= CompulsoryUnfolding (occurAnalyseExpr expr)
\end{code}
%************************************************************************
\begin{code}
-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}
-
-
-\begin{code}
calcUnfoldingGuidance
:: 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) ->
+ = case collectBinders expr of { (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 (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
-
+ TooBig -> UnfoldNever
SizeIs size cased_args scrut_discount
- -> UnfoldIfGoodArgs
- n_val_binders
- (map discount_for val_binders)
- final_size
- (iBox scrut_discount)
+ -> UnfoldIfGoodArgs { ug_arity = n_val_binders
+ , ug_args = map discount_for val_binders
+ , ug_size = iBox size
+ , ug_res = 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
- 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 :: FastInt -- Bomb out if it gets bigger than this
-> [Id] -- Arguments; we're interested in which of these
-- get case'd
-> CoreExpr
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 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 -- Other notes cost nothing
-
- size_up (Cast e _) = size_up e
-
- size_up (App fun (Type t)) = size_up fun
+ size_up (Type _) = sizeZero -- Types cost nothing
+ size_up (Var _) = sizeOne
+ size_up (Note _ body) = size_up body -- Notes cost nothing
+ size_up (Cast e _) = size_up e
+ size_up (App fun (Type _)) = size_up fun
size_up (App fun arg) = size_up_app fun [arg]
size_up (Lit lit) = sizeN (litSize lit)
case alts of
- [alt] -> size_up_alt alt `addSize` SizeIs 0# (unitBag (v, 1)) 0#
+ [alt] -> size_up_alt alt `addSize` SizeIs (_ILIT(0)) (unitBag (v, 1)) (_ILIT(0))
-- We want to make wrapper-style evaluation look cheap, so that
-- when we inline a wrapper it doesn't make call site (much) bigger
-- Otherwise we get nasty phase ordering stuff:
-- alts_size tries to compute a good discount for
-- the case when we are scrutinising an argument variable
- alts_size (SizeIs tot tot_disc tot_scrut) -- Size of all alternatives
- (SizeIs max max_disc max_scrut) -- Size of biggest alternative
- = SizeIs tot (unitBag (v, iBox (_ILIT 1 +# tot -# max)) `unionBags` max_disc) max_scrut
+ alts_size (SizeIs tot _tot_disc _tot_scrut) -- Size of all alternatives
+ (SizeIs max max_disc max_scrut) -- Size of biggest alternative
+ = SizeIs tot (unitBag (v, iBox (_ILIT(1) +# tot -# max)) `unionBags` max_disc) max_scrut
-- If the variable is known, we produce a discount that
-- will take us back to 'max', the size of rh largest alternative
-- The 1+ is a little discount for reduced allocation in the caller
alts_size tot_size _ = tot_size
--- gaw 2004
size_up (Case e _ _ alts) = nukeScrutDiscount (size_up e) `addSize`
foldr (addSize . size_up_alt) sizeZero alts
-- We don't charge for the case itself
= case globalIdDetails fun of
DataConWorkId dc -> conSizeN dc (valArgCount args)
- FCallId fc -> sizeN opt_UF_DearOp
+ FCallId _ -> sizeN opt_UF_DearOp
PrimOpId op -> primOpSize op (valArgCount args)
-- foldr addSize (primOpSize op) (map arg_discount args)
-- At one time I tried giving an arg-discount if a primop
-- if we know nothing about it. And just having it in a primop
-- doesn't help at all if we don't know something more.
- other -> fun_discount fun `addSizeN`
+ _ -> fun_discount fun `addSizeN`
(1 + length (filter (not . exprIsTrivial) args))
-- The 1+ is for the function itself
-- Add 1 for each non-trivial arg;
-- We should really only count for non-prim-typed args in the
-- general case, but that seems too much like hard work
- size_up_fun other args = size_up other
+ size_up_fun other _ = size_up other
------------
- size_up_alt (con, bndrs, rhs) = size_up rhs
+ size_up_alt (_con, _bndrs, rhs) = size_up rhs
-- Don't charge for args, so that wrappers look cheap
-- (See comments about wrappers with Case)
------------
-- We want to record if we're case'ing, or applying, an argument
- fun_discount v | v `elem` top_args = SizeIs 0# (unitBag (v, opt_UF_FunAppDiscount)) 0#
- fun_discount other = sizeZero
+ fun_discount v | v `elem` top_args = SizeIs (_ILIT(0)) (unitBag (v, opt_UF_FunAppDiscount)) (_ILIT(0))
+ fun_discount _ = sizeZero
------------
-- These addSize things have to be here because
-- tup = (a_1, ..., a_99)
-- x = case tup of ...
--
+mkSizeIs :: FastInt -> FastInt -> Bag (Id, Int) -> FastInt -> ExprSize
mkSizeIs max n xs d | (n -# d) ># max = TooBig
| otherwise = SizeIs n xs d
+maxSize :: ExprSize -> ExprSize -> ExprSize
maxSize TooBig _ = TooBig
maxSize _ TooBig = TooBig
maxSize s1@(SizeIs n1 _ _) s2@(SizeIs n2 _ _) | n1 ># n2 = s1
| otherwise = s2
-sizeZero = SizeIs (_ILIT 0) emptyBag (_ILIT 0)
-sizeOne = SizeIs (_ILIT 1) emptyBag (_ILIT 0)
-sizeN n = SizeIs (iUnbox n) emptyBag (_ILIT 0)
+sizeZero, sizeOne :: ExprSize
+sizeN :: Int -> ExprSize
+conSizeN :: DataCon ->Int -> ExprSize
+
+sizeZero = SizeIs (_ILIT(0)) emptyBag (_ILIT(0))
+sizeOne = SizeIs (_ILIT(1)) emptyBag (_ILIT(0))
+sizeN n = SizeIs (iUnbox n) emptyBag (_ILIT(0))
conSizeN dc n
- | isUnboxedTupleCon dc = SizeIs (_ILIT 0) emptyBag (iUnbox n +# _ILIT 1)
- | otherwise = SizeIs (_ILIT 1) emptyBag (iUnbox n +# _ILIT 1)
+ | isUnboxedTupleCon dc = SizeIs (_ILIT(0)) emptyBag (iUnbox n +# _ILIT(1))
+ | otherwise = SizeIs (_ILIT(1)) emptyBag (iUnbox n +# _ILIT(1))
-- Treat constructors as size 1; we are keen to expose them
-- (and we charge separately for their args). We can't treat
-- them as size zero, else we find that (iBox x) has size 1,
-- f x y z = case op# x y z of { s -> (# s, () #) }
-- and f wasn't getting inlined
+primOpSize :: PrimOp -> Int -> ExprSize
primOpSize op n_args
| not (primOpIsDupable op) = sizeN opt_UF_DearOp
| not (primOpOutOfLine op) = sizeN (2 - n_args)
-- and there's a good chance it'll get inlined back into C's RHS. Urgh!
| otherwise = sizeOne
-buildSize = SizeIs (-2#) emptyBag 4#
+buildSize :: ExprSize
+buildSize = SizeIs (_ILIT(-2)) emptyBag (_ILIT(4))
-- We really want to inline applications of build
-- build t (\cn -> e) should cost only the cost of e (because build will be inlined later)
-- Indeed, we should add a result_discount becuause build is
-- build is saturated (it usually is). The "-2" discounts for the \c n,
-- The "4" is rather arbitrary.
-augmentSize = SizeIs (-2#) emptyBag 4#
+augmentSize :: ExprSize
+augmentSize = SizeIs (_ILIT(-2)) emptyBag (_ILIT(4))
-- Ditto (augment t (\cn -> e) ys) should cost only the cost of
-- e plus ys. The -2 accounts for the \cn
-
-nukeScrutDiscount (SizeIs n vs d) = SizeIs n vs 0#
-nukeScrutDiscount TooBig = TooBig
+
+nukeScrutDiscount :: ExprSize -> ExprSize
+nukeScrutDiscount (SizeIs n vs _) = SizeIs n vs (_ILIT(0))
+nukeScrutDiscount TooBig = TooBig
-- When we return a lambda, give a discount if it's used (applied)
-lamScrutDiscount (SizeIs n vs d) = case opt_UF_FunAppDiscount of { d -> SizeIs n vs (iUnbox d) }
-lamScrutDiscount TooBig = TooBig
+lamScrutDiscount :: ExprSize -> ExprSize
+lamScrutDiscount (SizeIs n vs _) = case opt_UF_FunAppDiscount of { d -> SizeIs n vs (iUnbox d) }
+lamScrutDiscount TooBig = TooBig
\end{code}
\begin{code}
couldBeSmallEnoughToInline :: Int -> CoreExpr -> Bool
couldBeSmallEnoughToInline threshold rhs = case calcUnfoldingGuidance threshold rhs of
- UnfoldNever -> False
- other -> True
+ UnfoldNever -> False
+ _ -> True
certainlyWillInline :: Unfolding -> Bool
-- Sees if the unfolding is pretty certain to inline
-certainlyWillInline (CoreUnfolding _ _ _ is_cheap (UnfoldIfGoodArgs n_vals _ size _))
+certainlyWillInline (CompulsoryUnfolding {}) = True
+certainlyWillInline (InlineRule {}) = True
+certainlyWillInline (CoreUnfolding
+ { uf_is_cheap = is_cheap
+ , uf_guidance = UnfoldIfGoodArgs {ug_arity = n_vals, ug_size = size}})
= is_cheap && size - (n_vals +1) <= opt_UF_UseThreshold
-certainlyWillInline other
+certainlyWillInline _
= False
smallEnoughToInline :: Unfolding -> Bool
-smallEnoughToInline (CoreUnfolding _ _ _ _ (UnfoldIfGoodArgs _ _ size _))
+smallEnoughToInline (CoreUnfolding {uf_guidance = UnfoldIfGoodArgs {ug_size = size}})
= size <= opt_UF_UseThreshold
-smallEnoughToInline other
+smallEnoughToInline _
= False
\end{code}
callSiteInline :: DynFlags
-> Bool -- True <=> the Id can be inlined
-> Id -- The Id
+ -> Bool -- True if there are are no arguments at all (incl type args)
-> [Bool] -- One for each value arg; True if it is interesting
- -> Bool -- True <=> continuation is interesting
+ -> CallCtxt -- True <=> continuation is interesting
-> Maybe CoreExpr -- Unfolding, if any
-callSiteInline dflags active_inline id arg_infos interesting_cont
- = case idUnfolding id of {
+data CallCtxt = BoringCtxt
+
+ | ArgCtxt Bool -- We're somewhere in the RHS of function with rules
+ -- => be keener to inline
+ Int -- We *are* the argument of a function with this arg discount
+ -- => be keener to inline
+ -- INVARIANT: ArgCtxt False 0 ==> BoringCtxt
+
+ | ValAppCtxt -- We're applied to at least one value arg
+ -- This arises when we have ((f x |> co) y)
+ -- Then the (f x) has argument 'x' but in a ValAppCtxt
+
+ | CaseCtxt -- We're the scrutinee of a case
+ -- that decomposes its scrutinee
+
+instance Outputable CallCtxt where
+ ppr BoringCtxt = ptext (sLit "BoringCtxt")
+ ppr (ArgCtxt _ _) = ptext (sLit "ArgCtxt")
+ ppr CaseCtxt = ptext (sLit "CaseCtxt")
+ ppr ValAppCtxt = ptext (sLit "ValAppCtxt")
+
+callSiteInline dflags active_inline id lone_variable arg_infos cont_info
+ = let
+ n_val_args = length arg_infos
+ in
+ case idUnfolding id of {
NoUnfolding -> Nothing ;
- OtherCon cs -> Nothing ;
+ OtherCon _ -> Nothing ;
CompulsoryUnfolding unf_template -> Just unf_template ;
-- CompulsoryUnfolding => there is no top-level binding
-- compulsory unfoldings (see MkId.lhs).
-- We don't allow them to be inactive
- CoreUnfolding unf_template is_top is_value is_cheap guidance ->
+ InlineRule { uf_tmpl = unf_template, uf_arity = arity, uf_is_top = is_top
+ , uf_is_value = is_value, uf_worker = mb_worker }
+ -> let yes_or_no | not active_inline = False
+ | n_val_args < arity = yes_unsat -- Not enough value args
+ | n_val_args == arity = yes_exact -- Exactly saturated
+ | otherwise = True -- Over-saturated
+ result | yes_or_no = Just unf_template
+ | otherwise = Nothing
+
+ -- See Note [Inlining an InlineRule]
+ is_wrapper = isJust mb_worker
+ yes_unsat | is_wrapper = or arg_infos
+ | otherwise = False
+
+ yes_exact = or arg_infos || interesting_saturated_call
+ interesting_saturated_call
+ = case cont_info of
+ BoringCtxt -> not is_top -- Note [Nested functions]
+ CaseCtxt -> not lone_variable || not is_value -- Note [Lone variables]
+ ArgCtxt {} -> arity > 0 -- Note [Inlining in ArgCtxt]
+ ValAppCtxt -> True -- Note [Cast then apply]
+ in
+ if dopt Opt_D_dump_inlinings dflags then
+ pprTrace ("Considering InlineRule for: " ++ showSDoc (ppr id))
+ (vcat [text "active:" <+> ppr active_inline,
+ text "arg infos" <+> ppr arg_infos,
+ text "interesting call" <+> ppr interesting_saturated_call,
+ text "is value:" <+> ppr is_value,
+ text "ANSWER =" <+> if yes_or_no then text "YES" else text "NO"])
+ result
+ else result ;
+
+ CoreUnfolding { uf_tmpl = unf_template, uf_is_top = is_top, uf_is_value = is_value,
+ uf_is_cheap = is_cheap, uf_guidance = 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 = is_cheap && consider_safe False
+ yes_or_no = active_inline && is_cheap && consider_safe
-- We consider even the once-in-one-branch
-- occurrences, because they won't all have been
-- caught by preInlineUnconditionally. In particular,
-- pre-inline will not have inlined it for fear of
-- invalidating the occurrence info in the rhs.
- consider_safe once
+ consider_safe
-- consider_safe decides whether it's a good idea to
-- inline something, given that there's no
-- work-duplication issue (the caller checks that).
= case guidance of
UnfoldNever -> False
- UnfoldIfGoodArgs n_vals_wanted arg_discounts size res_discount
-
+ UnfoldIfGoodArgs { ug_arity = n_vals_wanted, ug_args = arg_discounts
+ , ug_res = res_discount, ug_size = size }
| 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
+ -> some_benefit && small_enough && inline_enough_args
where
- some_benefit = or arg_infos || really_interesting_cont ||
- (not is_top && ({- once || -} (n_vals_wanted > 0 && enough_args)))
- -- [was (once && not in_lam)]
- -- If it occurs more than once, there must be
- -- something interesting about some argument, or the
- -- result context, to make it worth inlining
- --
- -- If a function has a nested defn we also record
- -- some-benefit, on the grounds that we are often able
- -- to eliminate the binding, and hence the allocation,
- -- for the function altogether; this is good for join
- -- points. But this only makes sense for *functions*;
- -- inlining a constructor doesn't help allocation
- -- unless the result is scrutinised. UNLESS the
- -- constructor occurs just once, albeit possibly in
- -- multiple case branches. Then inlining it doesn't
- -- increase allocation, but it does increase the
- -- chance that the constructor won't be allocated at
- -- all in the branches that don't use it.
-
- enough_args = n_val_args >= n_vals_wanted
- really_interesting_cont | n_val_args < n_vals_wanted = False -- Too few args
- | n_val_args == n_vals_wanted = interesting_cont
- | otherwise = True -- Extra args
+ enough_args = n_val_args >= n_vals_wanted
+ inline_enough_args =
+ not (dopt Opt_InlineIfEnoughArgs dflags) || enough_args
+
+
+ some_benefit = or arg_infos || really_interesting_cont
+ -- There must be something interesting
+ -- about some argument, or the result
+ -- context, to make it worth inlining
+
+ really_interesting_cont
+ | n_val_args < n_vals_wanted = False -- Too few args
+ | n_val_args == n_vals_wanted = interesting_saturated_call
+ | otherwise = True -- Extra args
-- really_interesting_cont tells if the result of the
-- call is in an interesting context.
+ interesting_saturated_call
+ = case cont_info of
+ BoringCtxt -> not is_top && n_vals_wanted > 0 -- Note [Nested functions]
+ CaseCtxt -> not lone_variable || not is_value -- Note [Lone variables]
+ ArgCtxt {} -> n_vals_wanted > 0 -- Note [Inlining in ArgCtxt]
+ ValAppCtxt -> True -- Note [Cast then apply]
+
small_enough = (size - discount) <= opt_UF_UseThreshold
- discount = computeDiscount n_vals_wanted arg_discounts res_discount
- arg_infos really_interesting_cont
+ discount = computeDiscount n_vals_wanted arg_discounts
+ res_discount' arg_infos
+ res_discount' = case cont_info of
+ BoringCtxt -> 0
+ CaseCtxt -> res_discount
+ _other -> 4 `min` res_discount
+ -- res_discount can be very large when a function returns
+ -- construtors; but we only want to invoke that large discount
+ -- when there's a case continuation.
+ -- Otherwise we, rather arbitrarily, threshold it. Yuk.
+ -- But we want to aovid inlining large functions that return
+ -- constructors into contexts that are simply "interesting"
in
if dopt Opt_D_dump_inlinings dflags then
- pprTrace "Considering inlining"
- (ppr id <+> vcat [text "active:" <+> ppr active_inline,
- text "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"])
+ pprTrace ("Considering inlining: " ++ showSDoc (ppr id))
+ (vcat [text "active:" <+> ppr active_inline,
+ text "arg infos" <+> ppr arg_infos,
+ text "interesting continuation" <+> ppr cont_info,
+ 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
}
+\end{code}
-computeDiscount :: Int -> [Int] -> Int -> [Bool] -> Bool -> Int
-computeDiscount n_vals_wanted arg_discounts res_discount arg_infos result_used
+Note [Inlining an InlineRule]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+An InlineRules is used for
+ (a) pogrammer INLINE pragmas
+ (b) inlinings from worker/wrapper
+
+For (a) the RHS may be large, and our contract is that we *only* inline
+when the function is applied to all the arguments on the LHS of the
+source-code defn. (The uf_arity in the rule.)
+
+However for worker/wrapper it may be worth inlining even if the
+arity is not satisfied (as we do in the CoreUnfolding case) so we don't
+require saturation.
+
+
+Note [Nested functions]
+~~~~~~~~~~~~~~~~~~~~~~~
+If a function has a nested defn we also record some-benefit, on the
+grounds that we are often able to eliminate the binding, and hence the
+allocation, for the function altogether; this is good for join points.
+But this only makes sense for *functions*; inlining a constructor
+doesn't help allocation unless the result is scrutinised. UNLESS the
+constructor occurs just once, albeit possibly in multiple case
+branches. Then inlining it doesn't increase allocation, but it does
+increase the chance that the constructor won't be allocated at all in
+the branches that don't use it.
+
+Note [Cast then apply]
+~~~~~~~~~~~~~~~~~~~~~~
+Consider
+ myIndex = __inline_me ( (/\a. <blah>) |> co )
+ co :: (forall a. a -> a) ~ (forall a. T a)
+ ... /\a.\x. case ((myIndex a) |> sym co) x of { ... } ...
+
+We need to inline myIndex to unravel this; but the actual call (myIndex a) has
+no value arguments. The ValAppCtxt gives it enough incentive to inline.
+
+Note [Inlining in ArgCtxt]
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+The condition (n_vals_wanted > 0) here is very important, because otherwise
+we end up inlining top-level stuff into useless places; eg
+ x = I# 3#
+ f = \y. g x
+This can make a very big difference: it adds 16% to nofib 'integer' allocs,
+and 20% to 'power'.
+
+At one stage I replaced this condition by 'True' (leading to the above
+slow-down). The motivation was test eyeball/inline1.hs; but that seems
+to work ok now.
+
+Note [Lone variables]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The "lone-variable" case is important. I spent ages messing about
+with unsatisfactory varaints, but this is nice. The idea is that if a
+variable appears all alone
+ as an arg of lazy fn, or rhs Stop
+ as scrutinee of a case Select
+ as arg of a strict fn ArgOf
+AND
+ it is bound to a value
+then we should not inline it (unless there is some other reason,
+e.g. is is the sole occurrence). That is what is happening at
+the use of 'lone_variable' in 'interesting_saturated_call'.
+
+Why? At least in the case-scrutinee situation, turning
+ let x = (a,b) in case x of y -> ...
+into
+ let x = (a,b) in case (a,b) of y -> ...
+and thence to
+ let x = (a,b) in let y = (a,b) in ...
+is bad if the binding for x will remain.
+
+Another example: I discovered that strings
+were getting inlined straight back into applications of 'error'
+because the latter is strict.
+ s = "foo"
+ f = \x -> ...(error s)...
+
+Fundamentally such contexts should not encourage inlining because the
+context can ``see'' the unfolding of the variable (e.g. case or a
+RULE) so there's no gain. If the thing is bound to a value.
+
+However, watch out:
+
+ * Consider this:
+ foo = _inline_ (\n. [n])
+ bar = _inline_ (foo 20)
+ baz = \n. case bar of { (m:_) -> m + n }
+ Here we really want to inline 'bar' so that we can inline 'foo'
+ and the whole thing unravels as it should obviously do. This is
+ important: in the NDP project, 'bar' generates a closure data
+ structure rather than a list.
+
+ * Even a type application or coercion isn't a lone variable.
+ Consider
+ case $fMonadST @ RealWorld of { :DMonad a b c -> c }
+ We had better inline that sucker! The case won't see through it.
+
+ For now, I'm treating treating a variable applied to types
+ in a *lazy* context "lone". The motivating example was
+ f = /\a. \x. BIG
+ g = /\a. \y. h (f a)
+ There's no advantage in inlining f here, and perhaps
+ a significant disadvantage. Hence some_val_args in the Stop case
+
+\begin{code}
+computeDiscount :: Int -> [Int] -> Int -> [Bool] -> Int
+computeDiscount n_vals_wanted arg_discounts result_discount arg_infos
-- We multiple the raw discounts (args_discount and result_discount)
-- ty opt_UnfoldingKeenessFactor because the former have to do with
-- *size* whereas the discounts imply that there's some extra
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}
+
+%************************************************************************
+%* *
+ The Very Simple Optimiser
+%* *
+%************************************************************************
+
+
+\begin{code}
+simpleOptExpr :: CoreExpr -> CoreExpr
+-- Return an occur-analysed and slightly optimised expression
+-- The optimisation is very straightforward: just
+-- inline non-recursive bindings that are used only once,
+-- or wheere the RHS is trivial
+
+simpleOptExpr expr
+ = go emptySubst (occurAnalyseExpr expr)
+ where
+ go subst (Var v) = lookupIdSubst subst v
+ go subst (App e1 e2) = App (go subst e1) (go subst e2)
+ go subst (Type ty) = Type (substTy subst ty)
+ go _ (Lit lit) = Lit lit
+ go subst (Note note e) = Note note (go subst e)
+ go subst (Cast e co) = Cast (go subst e) (substTy subst co)
+ go subst (Let bind body) = go_bind subst bind body
+ go subst (Lam bndr body) = Lam bndr' (go subst' body)
+ where
+ (subst', bndr') = substBndr subst bndr
+
+ go subst (Case e b ty as) = Case (go subst e) b'
+ (substTy subst ty)
+ (map (go_alt subst') as)
+ where
+ (subst', b') = substBndr subst b
+
+
+ ----------------------
+ go_alt subst (con, bndrs, rhs) = (con, bndrs', go subst' rhs)
+ where
+ (subst', bndrs') = substBndrs subst bndrs
+
+ ----------------------
+ go_bind subst (Rec prs) body = Let (Rec (bndrs' `zip` rhss'))
+ (go subst' body)
+ where
+ (bndrs, rhss) = unzip prs
+ (subst', bndrs') = substRecBndrs subst bndrs
+ rhss' = map (go subst') rhss
+
+ go_bind subst (NonRec b r) body = go_nonrec subst b (go subst r) body
+
+ ----------------------
+ go_nonrec subst b (Type ty') body
+ | isTyVar b = go (extendTvSubst subst b ty') body
+ -- let a::* = TYPE ty in <body>
+ go_nonrec subst b r' body
+ | isId b -- let x = e in <body>
+ , exprIsTrivial r' || safe_to_inline (idOccInfo b)
+ = go (extendIdSubst subst b r') body
+ go_nonrec subst b r' body
+ = Let (NonRec b' r') (go subst' body)
+ where
+ (subst', b') = substBndr subst b
+
+ ----------------------
+ -- Unconditionally safe to inline
+ safe_to_inline :: OccInfo -> Bool
+ safe_to_inline IAmDead = True
+ safe_to_inline (OneOcc in_lam one_br _) = not in_lam && one_br
+ safe_to_inline (IAmALoopBreaker {}) = False
+ safe_to_inline NoOccInfo = False
+\end{code}
\ No newline at end of file
projects / ghc-hetmet.git / blobdiff