%
-% (c) The GRASP/AQUA Project, Glasgow University, 1993-1995
+% (c) The GRASP/AQUA Project, Glasgow University, 1993-1998
%
\section[WwLib]{A library for the ``worker/wrapper'' back-end to the strictness analyser}
\begin{code}
-#include "HsVersions.h"
-
-module WwLib (
- WwBinding(..),
-
- mkWwBodies, mAX_WORKER_ARGS,
-
- -- our friendly worker/wrapper monad:
- WwM(..),
- returnWw, thenWw, mapWw,
- getUniqueWw, uniqSMtoWwM,
-
- -- and to make the interface self-sufficient...
- GlobalSwitch, CoreBinding, CoreExpr, PlainCoreBinding(..),
- PlainCoreExpr(..), Id, Demand, MaybeErr,
- TyVar, UniType, Unique, SplitUniqSupply, SUniqSM(..)
-
- IF_ATTACK_PRAGMAS(COMMA splitUniqSupply COMMA getSUnique)
- IF_ATTACK_PRAGMAS(COMMA mkUniqueGrimily)
- ) where
+module WwLib ( mkWwBodies, mkWWstr, mkWorkerArgs ) where
-IMPORT_Trace
-import Outputable -- ToDo: rm (debugging)
-import Pretty
+#include "HsVersions.h"
-import AbsPrel ( aBSENT_ERROR_ID, mkFunTy )
-import AbsUniType ( mkTyVarTy, isPrimType, getUniDataTyCon_maybe,
- quantifyTy, TyVarTemplate
+import CoreSyn
+import CoreUtils ( exprType )
+import Id ( Id, idType, mkSysLocal, idNewDemandInfo, setIdNewDemandInfo,
+ isOneShotLambda, setOneShotLambda, setIdUnfolding,
+ setIdInfo
)
-import CmdLineOpts ( GlobalSwitch(..) )
-import Id ( mkWorkerId, mkSysLocal, getIdUniType,
- getInstantiatedDataConSig, getIdInfo,
- replaceIdInfo, addIdStrictness, DataCon(..)
+import IdInfo ( vanillaIdInfo )
+import DataCon ( splitProductType_maybe, splitProductType )
+import NewDemand ( Demand(..), DmdResult(..), Demands(..) )
+import MkId ( realWorldPrimId, voidArgId, mkRuntimeErrorApp, rUNTIME_ERROR_ID )
+import TysWiredIn ( tupleCon )
+import Type ( Type, isUnLiftedType, mkFunTys,
+ splitForAllTys, splitFunTys, splitRecNewType_maybe, isAlgType
)
-import IdInfo -- lots of things
-import Maybes ( maybeToBool, Maybe(..), MaybeErr )
-import PlainCore
-import SaLib
-import SrcLoc ( mkUnknownSrcLoc )
-import SplitUniq
-import Unique
-import Util
-
-infixr 9 `thenWw`
+import BasicTypes ( Boxity(..) )
+import Var ( Var, isId )
+import UniqSupply ( returnUs, thenUs, getUniquesUs, UniqSM )
+import Util ( zipWithEqual, notNull )
+import Outputable
+import List ( zipWith4 )
\end{code}
-%************************************************************************
-%* *
-\subsection[datatype-WwLib]{@WwBinding@: a datatype for worker/wrapper-ing}
-%* *
-%************************************************************************
-
-In the worker/wrapper stuff, we want to carry around @CoreBindings@ in
-an ``intermediate form'' that can later be turned into a \tr{let} or
-\tr{case} (depending on strictness info).
-
-\begin{code}
-data WwBinding
- = WwLet [PlainCoreBinding]
- | WwCase (PlainCoreExpr -> PlainCoreExpr)
- -- the "case" will be a "strict let" of the form:
- --
- -- case rhs of
- -- <blah> -> body
- --
- -- (instead of "let <blah> = rhs in body")
- --
- -- The expr you pass to the function is "body" (the
- -- expression that goes "in the corner").
-\end{code}
%************************************************************************
%* *
%* *
%************************************************************************
- ************ WARNING ******************
- these comments are rather out of date
- *****************************************
-
-@mkWrapperAndWorker@ is given:
-\begin{enumerate}
-\item
-The {\em original function} \tr{f}, of the form:
-\begin{verbatim}
-f = /\ tyvars -> \ args -> body
-\end{verbatim}
-The original-binder \tr{f}, the \tr{tyvars}, \tr{args}, and \tr{body}
-are given separately.
-
-We use the Id \tr{f} mostly to get its type.
-
-\item
-Strictness information about \tr{f}, in the form of a list of
-@Demands@.
-
-\item
-A @UniqueSupply@.
-\end{enumerate}
-
-@mkWrapperAndWorker@ produces (A BIT OUT-OF-DATE...):
-\begin{enumerate}
-\item
-Maybe @Nothing@: no worker/wrappering going on in this case. This can
-happen (a)~if the strictness info says that there is nothing
-interesting to do or (b)~if *any* of the argument types corresponding
-to ``active'' arg postitions is abstract or will be to the outside
-world (i.e., {\em this} module can see the constructors, but nobody
-else will be able to). An ``active'' arg position is one which the
-wrapper has to unpack. An importing module can't do this unpacking,
-so it simply has to give up and call the wrapper only.
-
-\item
-Maybe \tr{Just (wrapper_Id, wrapper_body, worker_Id, worker_body)}.
-
-The @wrapper_Id@ is just the one that was passed in, with its
-strictness IdInfo updated.
-\end{enumerate}
-
-The \tr{body} of the original function may not be given (i.e., it's
-BOTTOM), in which case you'd jolly well better not tug on the
-worker-body output!
-
Here's an example. The original function is:
+
\begin{verbatim}
g :: forall a . Int -> [a] -> a
g = /\ a -> \ x ys ->
case x of
- I# x# -> g.wrk a x# ys
+ I# x# -> $wg a x# ys
-- call the worker; don't forget the type args!
-- worker
-g.wrk :: forall a . Int# -> [a] -> a
+$wg :: forall a . Int# -> [a] -> a
-g.wrk = /\ a -> \ x# ys ->
+$wg = /\ a -> \ x# ys ->
let
x = I# x#
in
\end{verbatim}
Something we have to be careful about: Here's an example:
+
\begin{verbatim}
-- "f" strictness: U(P)U(P)
f (I# a) (I# b) = a +# b
g = f -- "g" strictness same as "f"
\end{verbatim}
+
\tr{f} will get a worker all nice and friendly-like; that's good.
{\em But we don't want a worker for \tr{g}}, even though it has the
same strictness as \tr{f}. Doing so could break laziness, at best.
same, we ``revise'' the strictness info, so that we won't propagate
the unusable strictness-info into the interfaces.
-==========================
-
-Here's the real fun... The wrapper's ``deconstructing'' of arguments
-and the worker's putting them back together again are ``duals'' in
-some sense.
-What we do is walk along the @Demand@ list, producing two
-expressions (one for wrapper, one for worker...), each with a ``hole''
-in it, where we will later plug in more information. For our previous
-example, the expressions-with-HOLES are:
-\begin{verbatim}
-\ x ys -> -- wrapper
- case x of
- I# x# -> <<HOLE>> x# ys
+%************************************************************************
+%* *
+\subsection{The worker wrapper core}
+%* *
+%************************************************************************
-\ x# ys -> -- worker
- let
- x = I# x#
- in
- <<HOLE>>
-\end{verbatim}
-(Actually, we add the lambda-bound arguments at the end...) (The big
-Lambdas are added on the front later.)
+@mkWwBodies@ is called when doing the worker/wrapper split inside a module.
\begin{code}
-mkWwBodies
- :: UniType -- Type of the *body* of the orig
- -- function; i.e. /\ tyvars -> \ vars -> body
- -> [TyVar] -- Type lambda vars of original function
- -> [Id] -- Args of original function
- -> [Demand] -- Strictness info for those args
-
- -> SUniqSM (Maybe -- Nothing iff (a) no interesting split possible
- -- (b) any unpack on abstract type
- (Id -> PlainCoreExpr, -- Wrapper expr w/
- -- hole for worker id
- PlainCoreExpr -> PlainCoreExpr, -- Worker expr w/ hole
- -- for original fn body
- StrictnessInfo, -- Worker strictness info
- UniType -> UniType) -- Worker type w/ hole
- ) -- for type of original fn body
-
-
-mkWwBodies body_ty tyvars args arg_infos
- = ASSERT(length args == length arg_infos)
- -- or you can get disastrous user/definer-module mismatches
- if (all_absent_args_and_unboxed_value body_ty arg_infos)
- then returnSUs Nothing
-
- else -- the rest...
- mk_ww_arg_processing args arg_infos (mAX_WORKER_ARGS - nonAbsentArgs arg_infos)
- `thenUsMaybe` \ (wrap_frag, work_args_info, work_frag) ->
- let
- (work_args, wrkr_demands) = unzip work_args_info
-
- wrkr_strictness = mkStrictnessInfo wrkr_demands Nothing -- no worker-of-worker...
-
- wrapper_w_hole = \ worker_id ->
- mkCoTyLam tyvars (
- mkCoLam args (
- wrap_frag (
- mkCoTyApps (CoVar worker_id) (map mkTyVarTy tyvars)
- )))
-
- worker_w_hole = \ orig_body ->
- mkCoTyLam tyvars (
- mkCoLam work_args (
- work_frag orig_body
- ))
-
- worker_ty_w_hole = \ body_ty ->
- snd (quantifyTy tyvars (
- foldr mkFunTy body_ty (map getIdUniType work_args)
- ))
+mkWwBodies :: Type -- Type of original function
+ -> [Demand] -- Strictness of original function
+ -> DmdResult -- Info about function result
+ -> [Bool] -- One-shot-ness of the function
+ -> UniqSM ([Demand], -- Demands for worker (value) args
+ Id -> CoreExpr, -- Wrapper body, lacking only the worker Id
+ CoreExpr -> CoreExpr) -- Worker body, lacking the original function rhs
+
+-- wrap_fn_args E = \x y -> E
+-- work_fn_args E = E x y
+
+-- wrap_fn_str E = case x of { (a,b) ->
+-- case a of { (a1,a2) ->
+-- E a1 a2 b y }}
+-- work_fn_str E = \a2 a2 b y ->
+-- let a = (a1,a2) in
+-- let x = (a,b) in
+-- E
+
+mkWwBodies fun_ty demands res_info one_shots
+ = mkWWargs fun_ty demands one_shots' `thenUs` \ (wrap_args, wrap_fn_args, work_fn_args, res_ty) ->
+ mkWWstr wrap_args `thenUs` \ (work_args, wrap_fn_str, work_fn_str) ->
+ let
+ (work_lam_args, work_call_args) = mkWorkerArgs work_args res_ty
in
- returnSUs (Just (wrapper_w_hole, worker_w_hole, wrkr_strictness, worker_ty_w_hole))
+ -- Don't do CPR if the worker doesn't have any value arguments
+ -- Then the worker is just a constant, so we don't want to unbox it.
+ (if any isId work_args then
+ mkWWcpr res_ty res_info
+ else
+ returnUs (id, id, res_ty)
+ ) `thenUs` \ (wrap_fn_cpr, work_fn_cpr, cpr_res_ty) ->
+
+ returnUs ([idNewDemandInfo v | v <- work_args, isId v],
+ Note InlineMe . wrap_fn_args . wrap_fn_cpr . wrap_fn_str . applyToVars work_call_args . Var,
+ mkLams work_lam_args. work_fn_str . work_fn_cpr . work_fn_args)
+ -- We use an INLINE unconditionally, even if the wrapper turns out to be
+ -- something trivial like
+ -- fw = ...
+ -- f = __inline__ (coerce T fw)
+ -- The point is to propagate the coerce to f's call sites, so even though
+ -- f's RHS is now trivial (size 1) we still want the __inline__ to prevent
+ -- fw from being inlined into f's RHS
where
- -- "all_absent_args_and_unboxed_value":
- -- check for the obscure case of "\ x y z ... -> body" where
- -- (a) *all* of the args x, y, z,... are absent, and
- -- (b) the type of body is unboxed
- -- If these conditions are true, we must *not* play worker/wrapper games!
-
- all_absent_args_and_unboxed_value body_ty arg_infos
- = not (null arg_infos)
- && all is_absent_arg arg_infos
- && isPrimType body_ty
-
- is_absent_arg (WwLazy True) = True
- is_absent_arg _ = False
+ one_shots' = one_shots ++ repeat False
\end{code}
-Important: mk_ww_arg_processing doesn't check
-for an "interesting" split. It just races ahead and makes the
-split, even if there's no unpacking at all. This is important for
-when it calls itself recursively.
-It returns Nothing only if it encounters an abstract type in mid-flight.
+%************************************************************************
+%* *
+\subsection{Making wrapper args}
+%* *
+%************************************************************************
+
+During worker-wrapper stuff we may end up with an unlifted thing
+which we want to let-bind without losing laziness. So we
+add a void argument. E.g.
+
+ f = /\a -> \x y z -> E::Int# -- E does not mention x,y,z
+==>
+ fw = /\ a -> \void -> E
+ f = /\ a -> \x y z -> fw realworld
+
+We use the state-token type which generates no code.
\begin{code}
-mAX_WORKER_ARGS :: Int -- ToDo: set via flag
-mAX_WORKER_ARGS = 6 -- Hmm... but this is an everything-must-
- -- be-compiled-with-the-same-val thing...
-
-mk_ww_arg_processing
- :: [Id] -- Args of original function
- -> [Demand] -- Strictness info for those args
- -- must be at least as long as args
-
- -> Int -- Number of extra args we are prepared to add.
- -- This prevents over-eager unpacking, leading
- -- to huge-arity functions.
-
- -> SUniqSM (Maybe -- Nothing iff any unpack on abstract type
- (PlainCoreExpr -> PlainCoreExpr, -- Wrapper expr w/
- -- hole for worker id
- -- applied to types
- [(Id,Demand)], -- Worker's args
- -- and their strictness info
- PlainCoreExpr -> PlainCoreExpr) -- Worker body expr w/ hole
- ) -- for original fn body
-
-mk_ww_arg_processing [] _ _ = returnSUs (Just (id, [], id))
-
-mk_ww_arg_processing (arg : args) (WwLazy True : infos) max_extra_args
- = -- Absent argument
- -- So, finish args to the right...
- --pprTrace "Absent; num_wrkr_args=" (ppInt num_wrkr_args) (
+mkWorkerArgs :: [Var]
+ -> Type -- Type of body
+ -> ([Var], -- Lambda bound args
+ [Var]) -- Args at call site
+mkWorkerArgs args res_ty
+ | any isId args || not (isUnLiftedType res_ty)
+ = (args, args)
+ | otherwise
+ = (args ++ [voidArgId], args ++ [realWorldPrimId])
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsection{Coercion stuff}
+%* *
+%************************************************************************
+
+
+We really want to "look through" coerces.
+Reason: I've seen this situation:
+
+ let f = coerce T (\s -> E)
+ in \x -> case x of
+ p -> coerce T' f
+ q -> \s -> E2
+ r -> coerce T' f
+
+If only we w/w'd f, we'd get
+ let f = coerce T (\s -> fw s)
+ fw = \s -> E
+ in ...
+
+Now we'll inline f to get
+
+ let fw = \s -> E
+ in \x -> case x of
+ p -> fw
+ q -> \s -> E2
+ r -> fw
+
+Now we'll see that fw has arity 1, and will arity expand
+the \x to get what we want.
+
+\begin{code}
+-- mkWWargs is driven off the function type and arity.
+-- It chomps bites off foralls, arrows, newtypes
+-- and keeps repeating that until it's satisfied the supplied arity
+
+mkWWargs :: Type
+ -> [Demand]
+ -> [Bool] -- True for a one-shot arg; ** may be infinite **
+ -> UniqSM ([Var], -- Wrapper args
+ CoreExpr -> CoreExpr, -- Wrapper fn
+ CoreExpr -> CoreExpr, -- Worker fn
+ Type) -- Type of wrapper body
+
+mkWWargs fun_ty demands one_shots
+ | Just rep_ty <- splitRecNewType_maybe fun_ty
+ -- The newtype case is for when the function has
+ -- a recursive newtype after the arrow (rare)
+ -- We check for arity >= 0 to avoid looping in the case
+ -- of a function whose type is, in effect, infinite
+ -- [Arity is driven by looking at the term, not just the type.]
+ --
+ -- It's also important when we have a function returning (say) a pair
+ -- wrapped in a recursive newtype, at least if CPR analysis can look
+ -- through such newtypes, which it probably can since they are
+ -- simply coerces.
+ = mkWWargs rep_ty demands one_shots `thenUs` \ (wrap_args, wrap_fn_args, work_fn_args, res_ty) ->
+ returnUs (wrap_args,
+ Note (Coerce fun_ty rep_ty) . wrap_fn_args,
+ work_fn_args . Note (Coerce rep_ty fun_ty),
+ res_ty)
+
+ | notNull demands
+ = getUniquesUs `thenUs` \ wrap_uniqs ->
let
- arg_ty = getIdUniType arg
+ (tyvars, tau) = splitForAllTys fun_ty
+ (arg_tys, body_ty) = splitFunTys tau
+
+ n_demands = length demands
+ n_arg_tys = length arg_tys
+ n_args = n_demands `min` n_arg_tys
+
+ new_fun_ty = mkFunTys (drop n_demands arg_tys) body_ty
+ new_demands = drop n_arg_tys demands
+ new_one_shots = drop n_args one_shots
+
+ val_args = zipWith4 mk_wrap_arg wrap_uniqs arg_tys demands one_shots
+ wrap_args = tyvars ++ val_args
in
- mk_ww_arg_processing args infos max_extra_args
- -- we've already discounted for absent args,
- -- so we don't change max_extra_args
- `thenUsMaybe` \ (wrap_rest, work_args_info, work_rest) ->
-
- -- wrapper doesn't pass this arg to worker:
- returnSUs (Just (
- -- wrapper:
- \ hole -> wrap_rest hole,
-
- -- worker:
- work_args_info, -- NB: no argument added
- \ hole -> mk_absent_let arg arg_ty (work_rest hole)
- ))
- --)
- where
- mk_absent_let arg arg_ty body
- = if not (isPrimType arg_ty) then
- CoLet (CoNonRec arg (mkCoTyApp (CoVar aBSENT_ERROR_ID) arg_ty))
- body
- else -- quite horrible
- panic "WwLib: haven't done mk_absent_let for primitives yet"
-
-
-mk_ww_arg_processing (arg : args) (WwUnpack cmpnt_infos : infos) max_extra_args
- | new_max_extra_args > 0 -- Check that we are prepared to add arguments
- = -- this is the complicated one.
- --pprTrace "Unpack; num_wrkr_args=" (ppCat [ppInt num_wrkr_args, ppStr "; new_max=", ppInt new_num_wrkr_args, ppStr "; arg=", ppr PprDebug arg, ppr PprDebug (WwUnpack cmpnt_infos)]) (
- case getUniDataTyCon_maybe arg_ty of
-
- Nothing -> -- Not a data type
- panic "mk_ww_arg_processing: not datatype"
-
- Just (_, _, []) -> -- An abstract type
- -- We have to give up on the whole idea
- returnSUs Nothing
- Just (_, _, (_:_:_)) -> -- Two or more constructors; that's odd
- panic "mk_ww_arg_processing: multi-constr"
-
- Just (arg_tycon, tycon_arg_tys, [data_con]) ->
- -- The main event: a single-constructor data type
-
- let
- (_,inst_con_arg_tys,_)
- = getInstantiatedDataConSig data_con tycon_arg_tys
- in
- getSUniques (length inst_con_arg_tys) `thenSUs` \ uniqs ->
-
- let unpk_args = zipWith (\ u t -> mkSysLocal SLIT("upk") u t mkUnknownSrcLoc)
- uniqs inst_con_arg_tys
- in
- -- In processing the rest, push the sub-component args
- -- and infos on the front of the current bunch
- mk_ww_arg_processing (unpk_args ++ args) (cmpnt_infos ++ infos) new_max_extra_args
- `thenUsMaybe` \ (wrap_rest, work_args_info, work_rest) ->
-
- returnSUs (Just (
- -- wrapper: unpack the value
- \ hole -> mk_unpk_case arg unpk_args
- data_con arg_tycon
- (wrap_rest hole),
-
- -- worker: expect the unpacked value;
- -- reconstruct the orig value with a "let"
- work_args_info,
- \ hole -> work_rest (mk_pk_let arg data_con tycon_arg_tys unpk_args hole)
- ))
- --)
+{- ASSERT( notNull tyvars || notNull arg_tys ) -}
+ if (null tyvars) && (null arg_tys) then
+ pprTrace "mkWWargs" (ppr fun_ty $$ ppr demands)
+ returnUs ([], id, id, fun_ty)
+ else
+
+ mkWWargs new_fun_ty
+ new_demands
+ new_one_shots `thenUs` \ (more_wrap_args, wrap_fn_args, work_fn_args, res_ty) ->
+
+ returnUs (wrap_args ++ more_wrap_args,
+ mkLams wrap_args . wrap_fn_args,
+ work_fn_args . applyToVars wrap_args,
+ res_ty)
+
+ | otherwise
+ = returnUs ([], id, id, fun_ty)
+
+
+applyToVars :: [Var] -> CoreExpr -> CoreExpr
+applyToVars vars fn = mkVarApps fn vars
+
+mk_wrap_arg uniq ty dmd one_shot
+ = set_one_shot one_shot (setIdNewDemandInfo (mkSysLocal FSLIT("w") uniq ty) dmd)
where
- arg_ty = getIdUniType arg
+ set_one_shot True id = setOneShotLambda id
+ set_one_shot False id = id
+\end{code}
- new_max_extra_args
- = max_extra_args
- + 1 -- We won't pass the original arg now
- - nonAbsentArgs cmpnt_infos -- But we will pass an arg for each cmpt
- mk_unpk_case arg unpk_args boxing_con boxing_tycon body
- = CoCase (CoVar arg) (
- CoAlgAlts [(boxing_con, unpk_args, body)]
- CoNoDefault
- )
+%************************************************************************
+%* *
+\subsection{Strictness stuff}
+%* *
+%************************************************************************
- mk_pk_let arg boxing_con con_tys unpk_args body
- = CoLet (CoNonRec arg (CoCon boxing_con con_tys [CoVarAtom a | a <- unpk_args]))
- body
+\begin{code}
+mkWWstr :: [Var] -- Wrapper args; have their demand info on them
+ -- *Includes type variables*
+ -> UniqSM ([Var], -- Worker args
+ CoreExpr -> CoreExpr, -- Wrapper body, lacking the worker call
+ -- and without its lambdas
+ -- This fn adds the unboxing
+
+ CoreExpr -> CoreExpr) -- Worker body, lacking the original body of the function,
+ -- and lacking its lambdas.
+ -- This fn does the reboxing
+
+----------------------
+nop_fn body = body
+
+----------------------
+mkWWstr []
+ = returnUs ([], nop_fn, nop_fn)
+
+mkWWstr (arg : args)
+ = mkWWstr_one arg `thenUs` \ (args1, wrap_fn1, work_fn1) ->
+ mkWWstr args `thenUs` \ (args2, wrap_fn2, work_fn2) ->
+ returnUs (args1 ++ args2, wrap_fn1 . wrap_fn2, work_fn1 . work_fn2)
+
+
+----------------------
+-- mkWWstr_one wrap_arg = (work_args, wrap_fn, work_fn)
+-- * wrap_fn assumes wrap_arg is in scope,
+-- brings into scope work_args (via cases)
+-- * work_fn assumes work_args are in scope, a
+-- brings into scope wrap_arg (via lets)
+
+mkWWstr_one arg
+ | isTyVar arg
+ = returnUs ([arg], nop_fn, nop_fn)
-mk_ww_arg_processing (arg : args) (arg_demand : infos) max_extra_args
| otherwise
- = -- For all others at the moment, we just
- -- pass them to the worker unchanged.
- --pprTrace "Other; num_wrkr_args=" (ppCat [ppInt num_wrkr_args, ppStr ";arg=", ppr PprDebug arg, ppr PprDebug arg_demand]) (
-
- -- Finish args to the right...
- mk_ww_arg_processing args infos max_extra_args
- `thenUsMaybe` \ (wrap_rest, work_args_info, work_rest) ->
-
- returnSUs (Just (
- -- wrapper:
- \ hole -> wrap_rest (CoApp hole (CoVarAtom arg)),
-
- -- worker:
- (arg, arg_demand) : work_args_info,
- \ hole -> work_rest hole
- ))
- --)
+ = case idNewDemandInfo arg of
+
+ -- Absent case. We don't deal with absence for unlifted types,
+ -- though, because it's not so easy to manufacture a placeholder
+ -- We'll see if this turns out to be a problem
+ Abs | not (isUnLiftedType (idType arg)) ->
+ returnUs ([], nop_fn, mk_absent_let arg)
+
+ -- Unpack case
+ Eval (Prod cs)
+ | Just (arg_tycon, tycon_arg_tys, data_con, inst_con_arg_tys)
+ <- splitProductType_maybe (idType arg)
+ -> getUniquesUs `thenUs` \ uniqs ->
+ let
+ unpk_args = zipWith mk_ww_local uniqs inst_con_arg_tys
+ unpk_args_w_ds = zipWithEqual "mkWWstr" set_worker_arg_info unpk_args cs
+ unbox_fn = mk_unpk_case arg unpk_args data_con arg_tycon
+ rebox_fn = Let (NonRec arg con_app)
+ con_app = mkConApp data_con (map Type tycon_arg_tys ++ map Var unpk_args)
+ in
+ mkWWstr unpk_args_w_ds `thenUs` \ (worker_args, wrap_fn, work_fn) ->
+ returnUs (worker_args, unbox_fn . wrap_fn, work_fn . rebox_fn)
+ -- Don't pass the arg, rebox instead
+
+ -- `seq` demand; evaluate in wrapper in the hope
+ -- of dropping seqs in the worker
+ Eval (Poly Abs)
+ -> let
+ arg_w_unf = arg `setIdUnfolding` evaldUnfolding
+ -- Tell the worker arg that it's sure to be evaluated
+ -- so that internal seqs can be dropped
+ in
+ returnUs ([arg_w_unf], mk_seq_case arg, nop_fn)
+ -- Pass the arg, anyway, even if it is in theory discarded
+ -- Consider
+ -- f x y = x `seq` y
+ -- x gets a (Eval (Poly Abs)) demand, but if we fail to pass it to the worker
+ -- we ABSOLUTELY MUST record that x is evaluated in the wrapper.
+ -- Something like:
+ -- f x y = x `seq` fw y
+ -- fw y = let x{Evald} = error "oops" in (x `seq` y)
+ -- If we don't pin on the "Evald" flag, the seq doesn't disappear, and
+ -- we end up evaluating the absent thunk.
+ -- But the Evald flag is pretty weird, and I worry that it might disappear
+ -- during simplification, so for now I've just nuked this whole case
+
+ -- Other cases
+ other_demand -> returnUs ([arg], nop_fn, nop_fn)
+
+ where
+ -- If the wrapper argument is a one-shot lambda, then
+ -- so should (all) the corresponding worker arguments be
+ -- This bites when we do w/w on a case join point
+ set_worker_arg_info worker_arg demand = set_one_shot (setIdNewDemandInfo worker_arg demand)
+
+ set_one_shot | isOneShotLambda arg = setOneShotLambda
+ | otherwise = \x -> x
\end{code}
+
%************************************************************************
%* *
-\subsection[monad-WwLib]{Simple monad for worker/wrapper}
+\subsection{CPR stuff}
%* *
%************************************************************************
-In this monad, we thread a @UniqueSupply@, and we carry a
-@GlobalSwitch@-lookup function downwards.
+
+@mkWWcpr@ takes the worker/wrapper pair produced from the strictness
+info and adds in the CPR transformation. The worker returns an
+unboxed tuple containing non-CPR components. The wrapper takes this
+tuple and re-produces the correct structured output.
+
+The non-CPR results appear ordered in the unboxed tuple as if by a
+left-to-right traversal of the result structure.
+
\begin{code}
-type WwM result
- = SplitUniqSupply
- -> (GlobalSwitch -> Bool)
- -> result
-
-#ifdef __GLASGOW_HASKELL__
-{-# INLINE thenWw #-}
-{-# INLINE returnWw #-}
-#endif
-
-returnWw :: a -> WwM a
-thenWw :: WwM a -> (a -> WwM b) -> WwM b
-mapWw :: (a -> WwM b) -> [a] -> WwM [b]
-
-returnWw expr ns sw = expr
-
-thenWw m k us sw_chk
- = case splitUniqSupply us of { (s1, s2) ->
- case (m s1 sw_chk) of { m_res ->
- k m_res s2 sw_chk }}
-
-mapWw f [] = returnWw []
-mapWw f (x:xs)
- = f x `thenWw` \ x' ->
- mapWw f xs `thenWw` \ xs' ->
- returnWw (x':xs')
+mkWWcpr :: Type -- function body type
+ -> DmdResult -- CPR analysis results
+ -> UniqSM (CoreExpr -> CoreExpr, -- New wrapper
+ CoreExpr -> CoreExpr, -- New worker
+ Type) -- Type of worker's body
+
+mkWWcpr body_ty RetCPR
+ | not (isAlgType body_ty)
+ = WARN( True, text "mkWWcpr: non-algebraic body type" <+> ppr body_ty )
+ returnUs (id, id, body_ty)
+
+ | n_con_args == 1 && isUnLiftedType con_arg_ty1
+ -- Special case when there is a single result of unlifted type
+ --
+ -- Wrapper: case (..call worker..) of x -> C x
+ -- Worker: case ( ..body.. ) of C x -> x
+ = getUniquesUs `thenUs` \ (work_uniq : arg_uniq : _) ->
+ let
+ work_wild = mk_ww_local work_uniq body_ty
+ arg = mk_ww_local arg_uniq con_arg_ty1
+ con_app = mkConApp data_con (map Type tycon_arg_tys ++ [Var arg])
+ in
+ returnUs (\ wkr_call -> Case wkr_call arg (exprType con_app) [(DEFAULT, [], con_app)],
+ \ body -> workerCase body work_wild con_arg_ty1 [(DataAlt data_con, [arg], Var arg)],
+ con_arg_ty1)
+
+ | otherwise -- The general case
+ -- Wrapper: case (..call worker..) of (# a, b #) -> C a b
+ -- Worker: case ( ...body... ) of C a b -> (# a, b #)
+ = getUniquesUs `thenUs` \ uniqs ->
+ let
+ (wrap_wild : work_wild : args) = zipWith mk_ww_local uniqs (ubx_tup_ty : body_ty : con_arg_tys)
+ arg_vars = map Var args
+ ubx_tup_con = tupleCon Unboxed n_con_args
+ ubx_tup_ty = exprType ubx_tup_app
+ ubx_tup_app = mkConApp ubx_tup_con (map Type con_arg_tys ++ arg_vars)
+ con_app = mkConApp data_con (map Type tycon_arg_tys ++ arg_vars)
+ in
+ returnUs (\ wkr_call -> Case wkr_call wrap_wild (exprType con_app) [(DataAlt ubx_tup_con, args, con_app)],
+ \ body -> workerCase body work_wild ubx_tup_ty [(DataAlt data_con, args, ubx_tup_app)],
+ ubx_tup_ty)
+ where
+ (_, tycon_arg_tys, data_con, con_arg_tys) = splitProductType "mkWWcpr" body_ty
+ n_con_args = length con_arg_tys
+ con_arg_ty1 = head con_arg_tys
+
+mkWWcpr body_ty other -- No CPR info
+ = returnUs (id, id, body_ty)
+
+-- If the original function looked like
+-- f = \ x -> _scc_ "foo" E
+--
+-- then we want the CPR'd worker to look like
+-- \ x -> _scc_ "foo" (case E of I# x -> x)
+-- and definitely not
+-- \ x -> case (_scc_ "foo" E) of I# x -> x)
+--
+-- This transform doesn't move work or allocation
+-- from one cost centre to another
+
+workerCase (Note (SCC cc) e) arg ty alts = Note (SCC cc) (Case e arg ty alts)
+workerCase e arg ty alts = Case e arg ty alts
\end{code}
-\begin{code}
-getUniqueWw :: WwM Unique
-uniqSMtoWwM :: SUniqSM a -> WwM a
-getUniqueWw us sw_chk = getSUnique us
+%************************************************************************
+%* *
+\subsection{Utilities}
+%* *
+%************************************************************************
-uniqSMtoWwM u_obj us sw_chk = u_obj us
-thenUsMaybe :: SUniqSM (Maybe a) -> (a -> SUniqSM (Maybe b)) -> SUniqSM (Maybe b)
-thenUsMaybe m k
- = m `thenSUs` \ result ->
- case result of
- Nothing -> returnSUs Nothing
- Just x -> k x
+\begin{code}
+mk_absent_let arg body
+ | not (isUnLiftedType arg_ty)
+ = Let (NonRec arg abs_rhs) body
+ | otherwise
+ = panic "WwLib: haven't done mk_absent_let for primitives yet"
+ where
+ arg_ty = idType arg
+ abs_rhs = mkRuntimeErrorApp rUNTIME_ERROR_ID arg_ty msg
+ msg = "Oops! Entered absent arg " ++ showSDocDebug (ppr arg <+> ppr (idType arg))
+
+mk_unpk_case arg unpk_args boxing_con boxing_tycon body
+ -- A data type
+ = Case (Var arg)
+ (sanitiseCaseBndr arg)
+ (exprType body)
+ [(DataAlt boxing_con, unpk_args, body)]
+
+mk_seq_case arg body = Case (Var arg) (sanitiseCaseBndr arg) (exprType body) [(DEFAULT, [], body)]
+
+sanitiseCaseBndr :: Id -> Id
+-- The argument we are scrutinising has the right type to be
+-- a case binder, so it's convenient to re-use it for that purpose.
+-- But we *must* throw away all its IdInfo. In particular, the argument
+-- will have demand info on it, and that demand info may be incorrect for
+-- the case binder. e.g. case ww_arg of ww_arg { I# x -> ... }
+-- Quite likely ww_arg isn't used in '...'. The case may get discarded
+-- if the case binder says "I'm demanded". This happened in a situation
+-- like (x+y) `seq` ....
+sanitiseCaseBndr id = id `setIdInfo` vanillaIdInfo
+
+mk_ww_local uniq ty = mkSysLocal FSLIT("ww") uniq ty
\end{code}
projects / ghc-hetmet.git / blobdiff