\section[WwLib]{A library for the ``worker/wrapper'' back-end to the strictness analyser}
\begin{code}
-module WwLib (
- WwBinding(..),
-
- worthSplitting, setUnpackStrategy,
- mkWwBodies, mkWrapper
- ) where
+module WwLib ( mkWwBodies, mkWWstr, mkWorkerArgs ) where
#include "HsVersions.h"
import CoreSyn
-import Id ( Id, idType, mkSysLocal, getIdDemandInfo, setIdDemandInfo,
- mkWildId, setIdInfo
+import CoreUtils ( exprType )
+import Id ( Id, idType, mkSysLocal, idNewDemandInfo, setIdNewDemandInfo,
+ isOneShotLambda, setOneShotLambda, setIdUnfolding,
+ setIdInfo
)
-import IdInfo ( CprInfo(..), noCprInfo, vanillaIdInfo )
-import Const ( Con(..), DataCon )
-import DataCon ( dataConArgTys )
-import Demand ( Demand(..) )
-import PrelInfo ( realWorldPrimId, aBSENT_ERROR_ID )
-import TysPrim ( realWorldStatePrimTy )
-import TysWiredIn ( unboxedTupleCon, unboxedTupleTyCon )
-import Type ( isUnLiftedType, mkTyVarTys, mkTyVarTy, mkFunTys,
- splitForAllTys, splitFunTys, splitFunTysN,
- splitAlgTyConApp_maybe, splitAlgTyConApp,
- mkTyConApp, newTypeRep, isNewType,
- Type
+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 TyCon ( isNewTyCon,
- TyCon )
-import BasicTypes ( NewOrData(..) )
-import Var ( TyVar )
-import UniqSupply ( returnUs, thenUs, getUniqueUs, getUniquesUs,
- mapUs, UniqSM )
-import Util ( zipWithEqual, zipEqual )
+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 [CoreBind]
- | WwCase (CoreExpr -> CoreExpr)
- -- 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.
%************************************************************************
%* *
-\subsection{Functions over Demands}
+\subsection{The worker wrapper core}
%* *
%************************************************************************
-\begin{code}
-mAX_WORKER_ARGS :: Int -- ToDo: set via flag
-mAX_WORKER_ARGS = 6
-
-setUnpackStrategy :: [Demand] -> [Demand]
-setUnpackStrategy ds
- = snd (go (mAX_WORKER_ARGS - nonAbsentArgs ds) ds)
- where
- go :: Int -- Max number of args available for sub-components of [Demand]
- -> [Demand]
- -> (Int, [Demand]) -- Args remaining after subcomponents of [Demand] are unpacked
-
- go n (WwUnpack nd _ cs : ds) | n' >= 0
- = WwUnpack nd True cs' `cons` go n'' ds
- | otherwise
- = WwUnpack nd False cs `cons` go n ds
- where
- n' = n + 1 - nonAbsentArgs cs
- -- Add one because we don't pass the top-level arg any more
- -- Delete # of non-absent args to which we'll now be committed
- (n'',cs') = go n' cs
-
- go n (d:ds) = d `cons` go n ds
- go n [] = (n,[])
-
- cons d (n,ds) = (n, d:ds)
-
-nonAbsentArgs :: [Demand] -> Int
-nonAbsentArgs [] = 0
-nonAbsentArgs (WwLazy True : ds) = nonAbsentArgs ds
-nonAbsentArgs (d : ds) = 1 + nonAbsentArgs ds
-
-worthSplitting :: [Demand]
- -> Bool -- Result is bottom
- -> Bool -- True <=> the wrapper would not be an identity function
-worthSplitting ds result_bot = not result_bot && any worth_it ds
- -- Don't split if the result is bottom; there's no efficiency to
- -- be gained, and (worse) the wrapper body may not look like a wrapper
- -- body to getWorkerIdAndCons
- where
- worth_it (WwLazy True) = True -- Absent arg
- worth_it (WwUnpack _ True _) = True -- Arg to unpack
- worth_it WwStrict = False -- Don't w/w just because of strictness
- worth_it other = False
+@mkWwBodies@ is called when doing the worker/wrapper split inside a module.
-allAbsent :: [Demand] -> Bool
-allAbsent ds = all absent ds
+\begin{code}
+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
+ -- 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
- absent (WwLazy is_absent) = is_absent
- absent (WwUnpack _ True cs) = allAbsent cs
- absent other = False
+ one_shots' = one_shots ++ repeat False
\end{code}
%************************************************************************
%* *
-\subsection{The worker wrapper core}
+\subsection{Making wrapper args}
%* *
%************************************************************************
-@mkWrapper@ is called when importing a function. We have the type of
-the function and the name of its worker, and we want to make its body (the wrapper).
+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.
-\begin{code}
-mkWrapper :: Type -- Wrapper type
- -> Int -- Arity
- -> [Demand] -- Wrapper strictness info
- -> CprInfo -- Wrapper cpr info
- -> UniqSM (Id -> CoreExpr) -- Wrapper body, missing worker Id
-
-mkWrapper fun_ty arity demands cpr_info
- = getUniquesUs arity `thenUs` \ wrap_uniqs ->
- let
- (tyvars, tau_ty) = splitForAllTys fun_ty
- (arg_tys, body_ty) = splitFunTysN "mkWrapper" arity tau_ty
- -- The "expanding dicts" part here is important, even for the splitForAll
- -- The imported thing might be a dictionary, such as Functor Foo
- -- But Functor Foo = forall a b. (a->b) -> Foo a -> Foo b
- -- and as such might have some strictness info attached.
- -- Then we need to have enough args to zip to the strictness info
-
- wrap_args = zipWith mk_ww_local wrap_uniqs arg_tys
- in
- mkWwBodies tyvars wrap_args body_ty demands cpr_info `thenUs` \ (wrap_fn, _, _) ->
- returnUs wrap_fn
-\end{code}
+ 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
-@mkWwBodies@ is called when doing the worker/wrapper split inside a module.
+We use the state-token type which generates no code.
\begin{code}
-mkWwBodies :: [TyVar] -> [Id] -> Type -- Original fn args and body type
- -> [Demand] -- Strictness info for original fn; corresp 1-1 with args
- -> CprInfo -- Result of CPR analysis
- -> UniqSM (Id -> CoreExpr, -- Wrapper body, lacking only the worker Id
- CoreExpr -> CoreExpr, -- Worker body, lacking the original function body
- [Demand]) -- Strictness info for worker
-
-mkWwBodies tyvars wrap_args body_ty demands cpr_info
- = let
- -- demands may be longer than number of args. If we aren't doing w/w
- -- for strictness then demands is an infinite list of 'lazy' args.
- wrap_args_w_demands = zipWith setIdDemandInfo wrap_args demands
- (wrap_fn_coerce, work_fn_coerce) = mkWWcoerce body_ty
- in
- mkWWstr body_ty wrap_args_w_demands `thenUs` \ (work_args_w_demands, wrap_fn_str, work_fn_str) ->
-
- mkWWcpr body_ty cpr_info `thenUs` \ (wrap_fn_cpr, work_fn_cpr) ->
-
- returnUs (\ work_id -> Note InlineMe $
- mkLams tyvars $ mkLams wrap_args_w_demands $
- (wrap_fn_coerce . wrap_fn_str . wrap_fn_cpr) $
- mkVarApps (Var work_id) (tyvars ++ work_args_w_demands),
-
- \ work_body -> mkLams tyvars $ mkLams work_args_w_demands $
- (work_fn_coerce . work_fn_str . work_fn_cpr)
- work_body,
-
- map getIdDemandInfo work_args_w_demands)
+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}
%* *
%************************************************************************
-The "coerce" transformation is
- f :: T1 -> T2 -> R
- f = \xy -> e
-===>
- f = \xy -> coerce R R' (fw x y)
- fw = \xy -> coerce R' R e
-where R' is the representation type for R.
+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}
-mkWWcoerce body_ty
- | not (isNewType body_ty)
- = (id, id)
+-- 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
+ (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
+{- 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
- = (wrap_fn . mkNote (Coerce body_ty rep_ty),
- mkNote (Coerce rep_ty body_ty) . work_fn)
- where
- (tycon, args, _) = splitAlgTyConApp body_ty
- rep_ty = newTypeRep tycon args
- (wrap_fn, work_fn) = mkWWcoerce rep_ty
-\end{code}
+ = 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
+ set_one_shot True id = setOneShotLambda id
+ set_one_shot False id = id
+\end{code}
+
%************************************************************************
%* *
%* *
%************************************************************************
-
\begin{code}
-mkWWstr :: Type -- Body type
- -> [Id] -- Wrapper args; have their demand info on them
- -> UniqSM ([Id], -- Worker args; have their demand info on them
-
- CoreExpr -> CoreExpr, -- Wrapper body, lacking the inner call to the worker
+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
- -- At the call site, the worker args are bound
+ -- This fn adds the unboxing
CoreExpr -> CoreExpr) -- Worker body, lacking the original body of the function,
- -- and without its lambdas
+ -- and lacking its lambdas.
+ -- This fn does the reboxing
-mkWWstr body_ty wrap_args
- = mk_ww wrap_args `thenUs` \ (work_args, wrap_fn, work_fn) ->
+----------------------
+nop_fn body = body
- if null work_args && isUnLiftedType body_ty then
- -- Horrid special case. If the worker would have no arguments, and the
- -- function returns a primitive type value, that would make the worker into
- -- an unboxed value. We box it by passing a dummy void argument, thus:
- --
- -- f = /\abc. \xyz. fw abc void
- -- fw = /\abc. \v. body
- --
- -- We use the state-token type which generates no code
- getUniqueUs `thenUs` \ void_arg_uniq ->
- let
- void_arg = mk_ww_local void_arg_uniq realWorldStatePrimTy
- in
- returnUs ([void_arg],
- wrap_fn . Let (NonRec void_arg (Var realWorldPrimId)),
- work_fn)
- else
- returnUs (work_args, wrap_fn, work_fn)
-
+----------------------
+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)
- -- Empty case
-mk_ww []
- = returnUs ([],
- \ wrapper_body -> wrapper_body,
- \ worker_body -> worker_body)
+----------------------
+-- 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)
-mk_ww (arg : ds)
- = case getIdDemandInfo arg of
+mkWWstr_one arg
+ | isTyVar arg
+ = returnUs ([arg], nop_fn, nop_fn)
- -- Absent case
- WwLazy True ->
- mk_ww ds `thenUs` \ (worker_args, wrap_fn, work_fn) ->
- returnUs (worker_args, wrap_fn, mk_absent_let arg . work_fn)
+ | otherwise
+ = case idNewDemandInfo arg of
- -- Unpack case
- WwUnpack new_or_data True cs ->
- getUniquesUs (length inst_con_arg_tys) `thenUs` \ uniqs ->
- let
- unpk_args = zipWith mk_ww_local uniqs inst_con_arg_tys
- unpk_args_w_ds = zipWithEqual "mk_ww" setIdDemandInfo unpk_args cs
- in
- mk_ww (unpk_args_w_ds ++ ds) `thenUs` \ (worker_args, wrap_fn, work_fn) ->
- returnUs (worker_args,
- mk_unpk_case new_or_data arg unpk_args data_con arg_tycon . wrap_fn,
- work_fn . mk_pk_let new_or_data arg data_con tycon_arg_tys unpk_args)
- where
- inst_con_arg_tys = dataConArgTys data_con tycon_arg_tys
- (arg_tycon, tycon_arg_tys, data_con)
- = case (splitAlgTyConApp_maybe (idType arg)) of
-
- Just (arg_tycon, tycon_arg_tys, [data_con]) ->
- -- The main event: a single-constructor data type
- (arg_tycon, tycon_arg_tys, data_con)
-
- Just (_, _, data_cons) ->
- pprPanic "mk_ww_arg_processing:"
- (text "not one constr (interface files not consistent/up to date?)"
- $$ (ppr arg <+> ppr (idType arg)))
-
- Nothing ->
- panic "mk_ww_arg_processing: not datatype"
+ -- 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 ->
- mk_ww ds `thenUs` \ (worker_args, wrap_fn, work_fn) ->
- returnUs (arg : worker_args, wrap_fn, work_fn)
+ 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}
\begin{code}
mkWWcpr :: Type -- function body type
- -> CprInfo -- CPR analysis results
+ -> DmdResult -- CPR analysis results
-> UniqSM (CoreExpr -> CoreExpr, -- New wrapper
- CoreExpr -> CoreExpr) -- New worker
+ CoreExpr -> CoreExpr, -- New worker
+ Type) -- Type of worker's body
-mkWWcpr body_ty NoCPRInfo
- = returnUs (id, id) -- Must be just the strictness transf.
-mkWWcpr body_ty (CPRInfo cpr_args)
- = getUniqueUs `thenUs` \ body_arg_uniq ->
- let
- body_var = mk_ww_local body_arg_uniq body_ty
- in
- cpr_reconstruct body_ty cpr_info' `thenUs` \reconst_fn ->
- cpr_flatten body_ty cpr_info' `thenUs` \flatten_fn ->
- returnUs (reconst_fn, flatten_fn)
- where
- -- We only make use of the outer level of CprInfo, otherwise we
- -- may lose laziness. :-( Hopefully, we will find a use for the
- -- extra info some day (e.g. creating versions specialized to
- -- the use made of the components of the result by the callee)
- cpr_info' = CPRInfo (map (const NoCPRInfo) cpr_args)
-\end{code}
-
-
-@cpr_flatten@ takes the result type produced by the body and the info
-from the CPR analysis and flattens the constructed product components.
-These are returned in an unboxed tuple.
+mkWWcpr body_ty RetCPR
+ | not (isAlgType body_ty)
+ = WARN( True, text "mkWWcpr: non-algebraic body type" <+> ppr body_ty )
+ returnUs (id, id, body_ty)
-\begin{code}
-cpr_flatten :: Type -> CprInfo -> UniqSM (CoreExpr -> CoreExpr)
-cpr_flatten ty cpr_info
- = mk_cpr_case (ty, cpr_info) `thenUs` \(res_id, tup_ids, flatten_exp) ->
- returnUs (\body -> Case body res_id
- [(DEFAULT, [], flatten_exp (fst $ mk_unboxed_tuple tup_ids))])
-
-
-
-mk_cpr_case :: (Type, CprInfo) ->
- UniqSM (CoreBndr, -- Name of binder for this part of result
- [(CoreExpr, Type)], -- expressions for flattened result
- CoreExpr -> CoreExpr) -- add in code to flatten result
-
-mk_cpr_case (ty, NoCPRInfo)
- -- this component must be returned as a component of the unboxed tuple result
- = getUniqueUs `thenUs` \id_uniq ->
- let id_id = mk_ww_local id_uniq ty in
- returnUs (id_id, [(Var id_id, ty)], id)
-mk_cpr_case (ty, cpr_info@(CPRInfo ci_args))
- | isNewTyCon tycon -- a new type: under the coercions must be a
- -- constructed product
- = ASSERT ( null $ tail inst_con_arg_tys )
- mk_cpr_case (target_of_from_type, cpr_info)
- `thenUs` \(arg, tup, exp) ->
- getUniqueUs `thenUs` \id_uniq ->
- let id_id = mk_ww_local id_uniq ty
- new_exp_case = \var -> Case (Note (Coerce (idType arg) ty) (Var id_id))
- arg
- [(DEFAULT,[], exp var)]
- in
- returnUs (id_id, tup, new_exp_case)
-
- | otherwise -- a data type
- -- flatten components
- = mapUs mk_cpr_case (zip inst_con_arg_tys ci_args)
- `thenUs` \sub_builds ->
- getUniqueUs `thenUs` \id_uniq ->
- let id_id = mk_ww_local id_uniq ty
- (args, tup, exp) = unzip3 sub_builds
- con_app = mkConApp data_con (map Var args)
- new_tup = concat tup
- new_exp_case = \var -> Case (Var id_id) (mkWildId ty)
- [(DataCon data_con, args,
- foldl (\e f -> f e) var exp)]
- in
- returnUs (id_id, new_tup, new_exp_case)
- where
- (data_con, tycon, tycon_arg_tys, inst_con_arg_tys) = splitType "mk_cpr_case" ty
- from_type = head inst_con_arg_tys
- -- if coerced from a function 'look through' to find result type
- target_of_from_type = (snd.splitFunTys.snd.splitForAllTys) from_type
-
-\end{code}
-
-@cpr_reconstruct@ does the opposite of @cpr_flatten@. It takes the unboxed
-tuple produced by the worker and reconstructs the structured result.
-
-\begin{code}
-cpr_reconstruct :: Type -> CprInfo -> UniqSM (CoreExpr -> CoreExpr)
-cpr_reconstruct ty cpr_info
- = mk_cpr_let (ty,cpr_info) `thenUs` \(res_id, tup_ids, reconstruct_exp) ->
- returnUs (\worker -> Case worker (mkWildId $ worker_type tup_ids)
- [(DataCon $ unboxedTupleCon $ length tup_ids,
- tup_ids, reconstruct_exp $ Var res_id)])
-
- where
- worker_type ids = mkTyConApp (unboxedTupleTyCon (length ids)) (map idType ids)
-
-
-mk_cpr_let :: (Type, CprInfo) ->
- UniqSM (CoreBndr, -- Binder for this component of result
- [CoreBndr], -- Binders which will appear in worker's result
- CoreExpr -> CoreExpr) -- Code to produce structured result.
-mk_cpr_let (ty, NoCPRInfo)
- -- this component will appear explicitly in the unboxed tuple.
- = getUniqueUs `thenUs` \id_uniq ->
+ | 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
- id_id = mk_ww_local id_uniq ty
+ 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 (id_id, [id_id], id)
-
-mk_cpr_let (ty, cpr_info@(CPRInfo ci_args))
- | isNewTyCon tycon -- a new type: must coerce the argument to this type
- = ASSERT ( null $ tail inst_con_arg_tys )
- mk_cpr_let (target_of_from_type, cpr_info)
- `thenUs` \(arg, tup, exp) ->
- getUniqueUs `thenUs` \id_uniq ->
- let id_id = mk_ww_local id_uniq ty
- new_exp = \var -> exp (Let (NonRec id_id (Note (Coerce ty (idType arg)) (Var arg))) var)
- in
- returnUs (id_id, tup, new_exp)
-
- | otherwise -- a data type
- -- reconstruct components then apply data con
- = mapUs mk_cpr_let (zip inst_con_arg_tys ci_args)
- `thenUs` \sub_builds ->
- getUniqueUs `thenUs` \id_uniq ->
- let id_id = mk_ww_local id_uniq ty
- (args, tup, exp) = unzip3 sub_builds
- con_app = mkConApp data_con $ (map Type tycon_arg_tys) ++ (map Var args)
- new_tup = concat tup
- new_exp = \var -> foldl (\e f -> f e) (Let (NonRec id_id con_app) var) exp
+ 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 (id_id, new_tup, new_exp)
+ 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
- (data_con, tycon, tycon_arg_tys, inst_con_arg_tys) = splitType "mk_cpr_let" ty
- from_type = head inst_con_arg_tys
- -- if coerced from a function 'look through' to find result type
- target_of_from_type = (snd.splitFunTys.snd.splitForAllTys) from_type
-
-
-splitType :: String -> Type -> (DataCon, TyCon, [Type], [Type])
-splitType fname ty = (data_con, tycon, tycon_arg_tys, dataConArgTys data_con tycon_arg_tys)
- where
- (data_con, tycon, tycon_arg_tys)
- = case (splitAlgTyConApp_maybe ty) of
- Just (arg_tycon, tycon_arg_tys, [data_con]) ->
- -- The main event: a single-constructor data type
- (data_con, arg_tycon, tycon_arg_tys)
-
- Just (_, _, data_cons) ->
- pprPanic (fname ++ ":")
- (text "not one constr (interface files not consistent/up to date?)"
- $$ ppr ty)
-
- Nothing ->
- pprPanic (fname ++ ":")
- (text "not a datatype" $$ ppr ty)
+ (_, 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}
mk_absent_let arg body
| not (isUnLiftedType arg_ty)
- = Let (NonRec arg (mkTyApps (Var aBSENT_ERROR_ID) [arg_ty])) body
+ = 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 NewType arg unpk_args boxing_con boxing_tycon body
- -- A newtype! Use a coercion not a case
- = ASSERT( null other_args )
- Case (Note (Coerce (idType unpk_arg) (idType arg)) (Var arg))
- (sanitiseCaseBndr unpk_arg)
- [(DEFAULT,[],body)]
- where
- (unpk_arg:other_args) = unpk_args
-
-mk_unpk_case DataType arg unpk_args boxing_con boxing_tycon body
+mk_unpk_case arg unpk_args boxing_con boxing_tycon body
-- A data type
= Case (Var arg)
(sanitiseCaseBndr arg)
- [(DataCon boxing_con, unpk_args, body)]
+ (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
-- like (x+y) `seq` ....
sanitiseCaseBndr id = id `setIdInfo` vanillaIdInfo
-mk_pk_let NewType arg boxing_con con_tys unpk_args body
- = ASSERT( null other_args )
- Let (NonRec arg (Note (Coerce (idType arg) (idType unpk_arg)) (Var unpk_arg))) body
- where
- (unpk_arg:other_args) = unpk_args
-
-mk_pk_let DataType arg boxing_con con_tys unpk_args body
- = Let (NonRec arg (Con (DataCon boxing_con) con_args)) body
- where
- con_args = map Type con_tys ++ map Var unpk_args
-
-
-mk_ww_local uniq ty = mkSysLocal SLIT("ww") uniq ty
-
-
-mk_unboxed_tuple :: [(CoreExpr, Type)] -> (CoreExpr, Type)
-mk_unboxed_tuple contents
- = (mkConApp (unboxedTupleCon (length contents))
- (map (Type . snd) contents ++
- map fst contents),
- mkTyConApp (unboxedTupleTyCon (length contents))
- (map snd contents))
+mk_ww_local uniq ty = mkSysLocal FSLIT("ww") uniq ty
\end{code}
projects / ghc-hetmet.git / blobdiff