#include "HsVersions.h"
import CoreSyn
-import CoreUnfold ( Unfolding, certainlyWillInline )
-import CmdLineOpts ( opt_D_verbose_core2core, opt_D_dump_worker_wrapper )
-import CoreLint ( beginPass, endPass )
-import CoreUtils ( exprType, exprEtaExpandArity )
-import MkId ( mkWorkerId )
-import Id ( Id, idType, idStrictness, idArity, isOneShotLambda,
- setIdStrictness, idInlinePragma,
- setIdWorkerInfo, idCprInfo, setInlinePragma )
-import Type ( Type, isNewType, splitForAllTys, splitFunTys )
-import IdInfo ( mkStrictnessInfo, noStrictnessInfo, StrictnessInfo(..),
- CprInfo(..), exactArity, InlinePragInfo(..), isNeverInlinePrag,
- WorkerInfo(..)
+import CoreUnfold ( certainlyWillInline )
+import CoreLint ( showPass, endPass )
+import CoreUtils ( exprType, exprIsHNF )
+import Id ( Id, idType, isOneShotLambda,
+ setIdNewStrictness, mkWorkerId,
+ setIdWorkerInfo, setInlinePragma,
+ idInfo )
+import MkId ( lazyIdKey, lazyIdUnfolding )
+import Type ( Type )
+import IdInfo ( WorkerInfo(..), arityInfo,
+ newDemandInfo, newStrictnessInfo, unfoldingInfo, inlinePragInfo
+ )
+import NewDemand ( Demand(..), StrictSig(..), DmdType(..), DmdResult(..),
+ Demands(..), mkTopDmdType, isBotRes, returnsCPR, topSig, isAbsent
)
-import Demand ( Demand, wwLazy )
import UniqSupply ( UniqSupply, initUs_, returnUs, thenUs, mapUs, getUniqueUs, UniqSM )
+import Unique ( hasKey )
+import BasicTypes ( RecFlag(..), isNonRec, Activation(..) )
+import VarEnv ( isEmptyVarEnv )
+import Maybes ( orElse )
+import DynFlags
import WwLib
+import Util ( lengthIs, notNull )
import Outputable
\end{code}
\begin{code}
-wwTopBinds :: UniqSupply
- -> [CoreBind]
- -> IO [CoreBind]
+wwTopBinds :: DynFlags
+ -> UniqSupply
+ -> [CoreBind]
+ -> IO [CoreBind]
-wwTopBinds us binds
+wwTopBinds dflags us binds
= do {
- beginPass "Worker Wrapper binds";
+ showPass dflags "Worker Wrapper binds";
-- Create worker/wrappers, and mark binders with their
-- "strictness info" [which encodes their worker/wrapper-ness]
let { binds' = workersAndWrappers us binds };
- endPass "Worker Wrapper binds" (opt_D_dump_worker_wrapper ||
- opt_D_verbose_core2core) binds'
+ endPass dflags "Worker Wrapper binds"
+ Opt_D_dump_worker_wrapper binds'
}
\end{code}
-- as appropriate.
wwBind (NonRec binder rhs)
- = wwExpr rhs `thenUs` \ new_rhs ->
- tryWW True {- non-recursive -} binder new_rhs `thenUs` \ new_pairs ->
+ = wwExpr rhs `thenUs` \ new_rhs ->
+ tryWW NonRecursive binder new_rhs `thenUs` \ new_pairs ->
returnUs [NonRec b e | (b,e) <- new_pairs]
-- Generated bindings must be non-recursive
-- because the original binding was.
-------------------------------
-
wwBind (Rec pairs)
= mapUs do_one pairs `thenUs` \ new_pairs ->
returnUs [Rec (concat new_pairs)]
where
do_one (binder, rhs) = wwExpr rhs `thenUs` \ new_rhs ->
- tryWW False {- recursive -} binder new_rhs
+ tryWW Recursive binder new_rhs
\end{code}
@wwExpr@ basically just walks the tree, looking for appropriate
\begin{code}
wwExpr :: CoreExpr -> UniqSM CoreExpr
-wwExpr e@(Type _) = returnUs e
-wwExpr e@(Var _) = returnUs e
-wwExpr e@(Lit _) = returnUs e
+wwExpr e@(Type _) = returnUs e
+wwExpr e@(Lit _) = returnUs e
+wwExpr e@(Note InlineMe expr) = returnUs e
+ -- Don't w/w inside InlineMe's
+
+wwExpr e@(Var v)
+ | v `hasKey` lazyIdKey = returnUs lazyIdUnfolding
+ | otherwise = returnUs e
+ -- Inline 'lazy' after strictness analysis
+ -- (but not inside InlineMe's)
wwExpr (Lam binder expr)
= wwExpr expr `thenUs` \ new_expr ->
wwExpr expr `thenUs` \ new_expr ->
returnUs (mkLets intermediate_bind new_expr)
-wwExpr (Case expr binder alts)
+wwExpr (Case expr binder ty alts)
= wwExpr expr `thenUs` \ new_expr ->
mapUs ww_alt alts `thenUs` \ new_alts ->
- returnUs (Case new_expr binder new_alts)
+ returnUs (Case new_expr binder ty new_alts)
where
ww_alt (con, binders, rhs)
= wwExpr rhs `thenUs` \ new_rhs ->
The only reason this is monadised is for the unique supply.
\begin{code}
-tryWW :: Bool -- True <=> a non-recursive binding
+tryWW :: RecFlag
-> Id -- The fn binder
-> CoreExpr -- The bound rhs; its innards
-- are already ww'd
-- the orig "wrapper" lives on);
-- if two, then a worker and a
-- wrapper.
-tryWW non_rec fn_id rhs
- | isNeverInlinePrag inline_prag || arity == 0
- = -- Don't split things that will never be inlined
- returnUs [ (fn_id, rhs) ]
-
- | non_rec && not do_coerce_ww && certainlyWillInline fn_id
+tryWW is_rec fn_id rhs
+ | isNonRec is_rec && certainlyWillInline unfolding
-- No point in worker/wrappering a function that is going to be
-- INLINEd wholesale anyway. If the strictness analyser is run
-- twice, this test also prevents wrappers (which are INLINEd)
-- from being re-done.
- --
- -- The do_coerce_ww test is so that
- -- a function with a coerce should w/w to get rid
- -- of the coerces, which can significantly improve its arity.
- -- Example: f [] = return [] :: IO [Int]
- -- f (x:xs) = return (x:xs)
- -- If we aren't careful we end up with
- -- f = \ x -> case x of {
- -- x:xs -> __coerce (IO [Int]) (\ s -> (# s, x:xs #)
- -- [] -> lvl_sJ8
- --
- --
- -- OUT OF DATE NOTE, kept for info:
- -- It's out of date because now wrappers look very cheap
- -- even when they are inlined.
- -- In this case we add an INLINE pragma to the RHS. Why?
- -- Because consider
- -- f = \x -> g x x
- -- g = \yz -> ... -- And g is strict
- -- Then f is small, so we don't w/w it. But g is big, and we do, so
- -- g's wrapper will get inlined in f's RHS, which makes f look big now.
- -- So f doesn't get inlined, but it is strict and we have failed to w/w it.
- = returnUs [ (fn_id, rhs) ]
-
- | not (do_strict_ww || do_cpr_ww || do_coerce_ww)
- = returnUs [ (fn_id, rhs) ]
-
- | otherwise -- Do w/w split
- = mkWwBodies fun_ty arity wrap_dmds result_bot one_shots cpr_info `thenUs` \ (work_demands, wrap_fn, work_fn) ->
- getUniqueUs `thenUs` \ work_uniq ->
+ --
+ -- It's very important to refrain from w/w-ing an INLINE function
+ -- If we do so by mistake we transform
+ -- f = __inline (\x -> E)
+ -- into
+ -- f = __inline (\x -> case x of (a,b) -> fw E)
+ -- fw = \ab -> (__inline (\x -> E)) (a,b)
+ -- and the original __inline now vanishes, so E is no longer
+ -- inside its __inline wrapper. Death! Disaster!
+ = returnUs [ (new_fn_id, rhs) ]
+
+ | is_thunk && worthSplittingThunk maybe_fn_dmd res_info
+ = ASSERT2( isNonRec is_rec, ppr new_fn_id ) -- The thunk must be non-recursive
+ splitThunk new_fn_id rhs
+
+ | is_fun && worthSplittingFun wrap_dmds res_info
+ = splitFun new_fn_id fn_info wrap_dmds res_info inline_prag rhs
+
+ | otherwise
+ = returnUs [ (new_fn_id, rhs) ]
+
+ where
+ fn_info = idInfo fn_id
+ maybe_fn_dmd = newDemandInfo fn_info
+ unfolding = unfoldingInfo fn_info
+ inline_prag = inlinePragInfo fn_info
+
+ -- In practice it always will have a strictness
+ -- signature, even if it's a uninformative one
+ strict_sig = newStrictnessInfo fn_info `orElse` topSig
+ StrictSig (DmdType env wrap_dmds res_info) = strict_sig
+
+ -- new_fn_id has the DmdEnv zapped.
+ -- (a) it is never used again
+ -- (b) it wastes space
+ -- (c) it becomes incorrect as things are cloned, because
+ -- we don't push the substitution into it
+ new_fn_id | isEmptyVarEnv env = fn_id
+ | otherwise = fn_id `setIdNewStrictness`
+ StrictSig (mkTopDmdType wrap_dmds res_info)
+
+ is_fun = notNull wrap_dmds
+ is_thunk = not is_fun && not (exprIsHNF rhs)
+
+---------------------
+splitFun fn_id fn_info wrap_dmds res_info inline_prag rhs
+ = WARN( not (wrap_dmds `lengthIs` arity), ppr fn_id <+> (ppr arity $$ ppr wrap_dmds $$ ppr res_info) )
+ -- The arity should match the signature
+ mkWwBodies fun_ty wrap_dmds res_info one_shots `thenUs` \ (work_demands, wrap_fn, work_fn) ->
+ getUniqueUs `thenUs` \ work_uniq ->
let
- work_rhs = work_fn rhs
- proto_work_id = mkWorkerId work_uniq fn_id (exprType work_rhs)
+ work_rhs = work_fn rhs
+ work_id = mkWorkerId work_uniq fn_id (exprType work_rhs)
`setInlinePragma` inline_prag
-
- work_id | has_strictness = proto_work_id `setIdStrictness` mkStrictnessInfo (work_demands, result_bot)
- | otherwise = proto_work_id
+ `setIdNewStrictness` StrictSig (mkTopDmdType work_demands work_res_info)
+ -- Even though we may not be at top level,
+ -- it's ok to give it an empty DmdEnv
wrap_rhs = wrap_fn work_id
- wrap_id = fn_id `setIdStrictness` wrapper_strictness
- `setIdWorkerInfo` HasWorker work_id arity
- `setInlinePragma` NoInlinePragInfo -- Put it on the worker instead
- -- Add info to the wrapper:
- -- (a) we want to set its arity
- -- (b) we want to pin on its revised strictness info
- -- (c) we pin on its worker id
+ wrap_id = fn_id `setIdWorkerInfo` HasWorker work_id arity
+ `setInlinePragma` AlwaysActive -- Zap any inline pragma;
+ -- Put it on the worker instead
in
returnUs ([(work_id, work_rhs), (wrap_id, wrap_rhs)])
-- Worker first, because wrapper mentions it
-- mkWwBodies has already built a wrap_rhs with an INLINE pragma wrapped around it
where
fun_ty = idType fn_id
- arity = idArity fn_id -- The arity is set by the simplifier using exprEtaExpandArity
+
+ arity = arityInfo fn_info -- The arity is set by the simplifier using exprEtaExpandArity
-- So it may be more than the number of top-level-visible lambdas
- inline_prag = idInlinePragma fn_id
-
- strictness_info = idStrictness fn_id
- has_strictness = case strictness_info of
- StrictnessInfo _ _ -> True
- NoStrictnessInfo -> False
- (arg_demands, result_bot) = case strictness_info of
- StrictnessInfo d r -> (d, r)
- NoStrictnessInfo -> ([], False)
-
- wrap_dmds = setUnpackStrategy arg_demands
- do_strict_ww = WARN( has_strictness && not result_bot && arity < length arg_demands && worthSplitting wrap_dmds result_bot,
- text "Insufficient arity" <+> ppr fn_id <+> ppr arity <+> ppr arg_demands )
- (result_bot || arity >= length arg_demands) -- Only if there's enough visible arity
- && -- (else strictness info isn't valid)
- --
- worthSplitting wrap_dmds result_bot -- And it's useful
- -- worthSplitting returns False for an empty list of demands,
- -- and hence do_strict_ww is False if arity is zero
- -- Also it's false if there is no strictness (arg_demands is [])
-
- wrapper_strictness | has_strictness = mkStrictnessInfo (wrap_dmds, result_bot)
- | otherwise = noStrictnessInfo
-
- -------------------------------------------------------------
- cpr_info = idCprInfo fn_id
- do_cpr_ww = arity > 0 &&
- case cpr_info of
- ReturnsCPR -> True
- other -> False
-
- -------------------------------------------------------------
- do_coerce_ww = check_for_coerce arity fun_ty
- -- We are willing to do a w/w even if the arity is zero.
- -- x = coerce t E
- -- ==>
- -- x' = E
- -- x = coerce t x'
-
- -------------------------------------------------------------
- one_shots = get_one_shots rhs
+ work_res_info | isBotRes res_info = BotRes -- Cpr stuff done by wrapper
+ | otherwise = TopRes
--- See if there's a Coerce before we run out of arity;
--- if so, it's worth trying a w/w split. Reason: we find
--- functions like f = coerce (\s -> e)
--- and g = \x -> coerce (\s -> e)
--- and they may have no useful strictness or cpr info, but if we
--- do the w/w thing we get rid of the coerces.
-
-check_for_coerce arity ty
- = length arg_tys <= arity && isNewType res_ty
- -- Don't look further than arity args,
- -- but if there are arity or fewer, see if there's
- -- a newtype in the corner
- where
- (_, tau) = splitForAllTys ty
- (arg_tys, res_ty) = splitFunTys tau
+ one_shots = get_one_shots rhs
-- If the original function has one-shot arguments, it is important to
-- make the wrapper and worker have corresponding one-shot arguments too.
get_one_shots other = noOneShotInfo
\end{code}
+Thunk splitting
+~~~~~~~~~~~~~~~
+Suppose x is used strictly (never mind whether it has the CPR
+property).
+
+ let
+ x* = x-rhs
+ in body
+
+splitThunk transforms like this:
+
+ let
+ x* = case x-rhs of { I# a -> I# a }
+ in body
+
+Now simplifier will transform to
+
+ case x-rhs of
+ I# a -> let x* = I# b
+ in body
+
+which is what we want. Now suppose x-rhs is itself a case:
+
+ x-rhs = case e of { T -> I# a; F -> I# b }
+
+The join point will abstract over a, rather than over (which is
+what would have happened before) which is fine.
+
+Notice that x certainly has the CPR property now!
+
+In fact, splitThunk uses the function argument w/w splitting
+function, so that if x's demand is deeper (say U(U(L,L),L))
+then the splitting will go deeper too.
+
+\begin{code}
+-- splitThunk converts the *non-recursive* binding
+-- x = e
+-- into
+-- x = let x = e
+-- in case x of
+-- I# y -> let x = I# y in x }
+-- See comments above. Is it not beautifully short?
+
+splitThunk fn_id rhs
+ = mkWWstr [fn_id] `thenUs` \ (_, wrap_fn, work_fn) ->
+ returnUs [ (fn_id, Let (NonRec fn_id rhs) (wrap_fn (work_fn (Var fn_id)))) ]
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsection{Functions over Demands}
+%* *
+%************************************************************************
+
+\begin{code}
+worthSplittingFun :: [Demand] -> DmdResult -> Bool
+ -- True <=> the wrapper would not be an identity function
+worthSplittingFun ds res
+ = any worth_it ds || returnsCPR res
+ -- worthSplitting returns False for an empty list of demands,
+ -- and hence do_strict_ww is False if arity is zero and there is no CPR
+
+ -- We used not to split if the result is bottom.
+ -- [Justification: there's no efficiency to be gained.]
+ -- But it's sometimes bad not to make a wrapper. Consider
+ -- fw = \x# -> let x = I# x# in case e of
+ -- p1 -> error_fn x
+ -- p2 -> error_fn x
+ -- p3 -> the real stuff
+ -- The re-boxing code won't go away unless error_fn gets a wrapper too.
+ -- [We don't do reboxing now, but in general it's better to pass
+ -- an unboxed thing to f, and have it reboxed in the error cases....]
+ where
+ worth_it Abs = True -- Absent arg
+ worth_it (Eval (Prod ds)) = True -- Product arg to evaluate
+ worth_it other = False
+
+worthSplittingThunk :: Maybe Demand -- Demand on the thunk
+ -> DmdResult -- CPR info for the thunk
+ -> Bool
+worthSplittingThunk maybe_dmd res
+ = worth_it maybe_dmd || returnsCPR res
+ where
+ -- Split if the thing is unpacked
+ worth_it (Just (Eval (Prod ds))) = not (all isAbsent ds)
+ worth_it other = False
+\end{code}
+
%************************************************************************
\begin{code}
mkWrapper :: Type -- Wrapper type
- -> Int -- Arity
- -> [Demand] -- Wrapper strictness info
- -> Bool -- Function returns bottom
- -> CprInfo -- Wrapper cpr info
+ -> StrictSig -- Wrapper strictness info
-> UniqSM (Id -> CoreExpr) -- Wrapper body, missing worker Id
-mkWrapper fun_ty arity demands res_bot cpr_info
- = mkWwBodies fun_ty arity demands res_bot noOneShotInfo cpr_info `thenUs` \ (_, wrap_fn, _) ->
+mkWrapper fun_ty (StrictSig (DmdType _ demands res_info))
+ = mkWwBodies fun_ty demands res_info noOneShotInfo `thenUs` \ (_, wrap_fn, _) ->
returnUs wrap_fn
noOneShotInfo = repeat False
\end{code}
-
-
projects / ghc-hetmet.git / blobdiff