import CoreSyn
import CoreUnfold ( certainlyWillInline )
import CoreLint ( showPass, endPass )
-import CoreUtils ( exprType )
-import Id ( Id, idType, idNewStrictness, idArity, isOneShotLambda,
- setIdNewStrictness, zapIdNewStrictness, idInlinePragma, mkWorkerId,
- setIdWorkerInfo, setInlinePragma )
+import CoreUtils ( exprType, exprIsValue )
+import Id ( Id, idType, isOneShotLambda,
+ setIdNewStrictness, mkWorkerId,
+ setIdWorkerInfo, setInlinePragma,
+ idInfo )
+import MkId ( lazyIdKey, lazyIdUnfolding )
import Type ( Type )
-import IdInfo ( InlinePragInfo(..), isNeverInlinePrag, WorkerInfo(..) )
+import IdInfo ( WorkerInfo(..), arityInfo,
+ newDemandInfo, newStrictnessInfo, unfoldingInfo, inlinePragInfo
+ )
import NewDemand ( Demand(..), StrictSig(..), DmdType(..), DmdResult(..),
- mkTopDmdType, isBotRes, returnsCPR
+ Demands(..), mkTopDmdType, isBotRes, returnsCPR, topSig, isAbsent
)
import UniqSupply ( UniqSupply, initUs_, returnUs, thenUs, mapUs, getUniqueUs, UniqSM )
-import BasicTypes ( RecFlag(..), isNonRec )
+import Unique ( hasKey )
+import BasicTypes ( RecFlag(..), isNonRec, Activation(..) )
+import VarEnv ( isEmptyVarEnv )
+import Maybes ( orElse )
import CmdLineOpts
import WwLib
+import Util ( lengthIs, notNull )
import Outputable
\end{code}
\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 ->
-- if two, then a worker and a
-- wrapper.
tryWW is_rec fn_id rhs
- | isNeverInlinePrag inline_prag
- -- Don't split NOINLINE things, because they will never be inlined
- -- Furthermore, zap the strictess info in the Id. Why? Because
- -- the NOINLINE says "don't expose any of the inner workings at the call
- -- site" and the strictness is certainly an inner working.
- --
- -- More concretely, the demand analyser discovers the following strictness
- -- for unsafePerformIO: C(U(AV))
- -- But then consider
- -- unsafePerformIO (\s -> let r = f x in
- -- case writeIORef v r s of (# s1, _ #) ->
- -- (# s1, r #)
- -- The strictness analyser will find that the binding for r is strict,
- -- (becuase of uPIO's strictness sig), and so it'll evaluate it before
- -- doing the writeIORef. This actually makes tests/lib/should_run/memo002
- -- get a deadlock!
- --
- -- Solution: don't expose the strictness of unsafePerformIO.
- = returnUs [ (zapIdNewStrictness fn_id, rhs) ]
-
- | arity == 0
- -- Don't worker-wrapper thunks
- || isNonRec is_rec && certainlyWillInline fn_id
+ | 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)
-- fw = \ab -> (__inline (\x -> E)) (a,b)
-- and the original __inline now vanishes, so E is no longer
-- inside its __inline wrapper. Death! Disaster!
- || not (worthSplitting strict_sig)
- -- Strictness info suggests not to w/w
- = returnUs [ (fn_id, rhs) ]
+ = 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
- | otherwise -- Do w/w split!
- = WARN( arity /= length wrap_dmds, ppr fn_id <+> (ppr arity $$ ppr strict_sig) )
+ | is_fun && worthSplittingFun wrap_dmds res_info
+ = splitFun new_fn_id fn_info wrap_dmds res_info inline_prag rhs
+
+ | otherwise
+ = returnUs [ (new_fn_id, rhs) ]
+
+ where
+ fn_info = idInfo fn_id
+ maybe_fn_dmd = newDemandInfo fn_info
+ unfolding = unfoldingInfo fn_info
+ inline_prag = inlinePragInfo fn_info
+ maybe_sig = newStrictnessInfo fn_info
+
+ -- In practice it always will have a strictness
+ -- signature, even if it's a uninformative one
+ strict_sig = newStrictnessInfo fn_info `orElse` topSig
+ StrictSig (DmdType env wrap_dmds res_info) = strict_sig
+
+ -- new_fn_id has the DmdEnv zapped.
+ -- (a) it is never used again
+ -- (b) it wastes space
+ -- (c) it becomes incorrect as things are cloned, because
+ -- we don't push the substitution into it
+ new_fn_id | isEmptyVarEnv env = fn_id
+ | otherwise = fn_id `setIdNewStrictness`
+ StrictSig (mkTopDmdType wrap_dmds res_info)
+
+ is_fun = notNull wrap_dmds
+ is_thunk = not is_fun && not (exprIsValue rhs)
+
+---------------------
+splitFun fn_id fn_info wrap_dmds res_info inline_prag rhs
+ = WARN( not (wrap_dmds `lengthIs` arity), ppr fn_id <+> (ppr arity $$ 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 ->
-- it's ok to give it an empty DmdEnv
wrap_rhs = wrap_fn work_id
- wrap_id = fn_id `setIdWorkerInfo` HasWorker work_id arity
- `setInlinePragma` NoInlinePragInfo -- Zap any inline pragma;
- -- Put it on the worker instead
+ 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
- -- So it may be more than the number of top-level-visible lambdas
- inline_prag = idInlinePragma fn_id
- strict_sig = idNewStrictness fn_id
+ 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
- StrictSig (DmdType _ wrap_dmds res_info) = strict_sig
work_res_info | isBotRes res_info = BotRes -- Cpr stuff done by wrapper
| otherwise = TopRes
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}
+
%************************************************************************
%* *
%************************************************************************
\begin{code}
-worthSplitting :: StrictSig -> Bool
+worthSplittingFun :: [Demand] -> DmdResult -> Bool
-- True <=> the wrapper would not be an identity function
-worthSplitting (StrictSig (DmdType _ ds res))
+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 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.]
-- [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 (Seq _ ds) = True -- Arg to evaluate
- worth_it other = False
+ 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}
projects / ghc-hetmet.git / blobdiff