\section[WwLib]{A library for the ``worker/wrapper'' back-end to the strictness analyser}
\begin{code}
-module WwLib (
- mkWwBodies,
- worthSplitting, setUnpackStrategy
- ) where
+module WwLib ( mkWwBodies, mkWWstr, mkWorkerArgs ) where
#include "HsVersions.h"
import CoreSyn
import CoreUtils ( exprType )
-import Id ( Id, idType, mkSysLocal, idDemandInfo, setIdDemandInfo,
- isOneShotLambda, setOneShotLambda,
+import Id ( Id, idType, mkSysLocal, idNewDemandInfo, setIdNewDemandInfo,
+ isOneShotLambda, setOneShotLambda, setIdUnfolding,
setIdInfo
)
-import IdInfo ( CprInfo(..), vanillaIdInfo )
-import DataCon ( splitProductType )
-import Demand ( Demand(..), wwLazy, wwPrim )
-import PrelInfo ( realWorldPrimId, aBSENT_ERROR_ID )
-import TysPrim ( realWorldStatePrimTy )
+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,
- splitForAllTys, splitFunTys, isAlgType,
- splitNewType_maybe, mkFunTys
+import Type ( Type, isUnLiftedType, mkFunTys,
+ splitForAllTys, splitFunTys, splitRecNewType_maybe, isAlgType
)
-import BasicTypes ( NewOrData(..), Arity, Boxity(..) )
+import BasicTypes ( Boxity(..) )
import Var ( Var, isId )
-import UniqSupply ( returnUs, thenUs, getUniqueUs, getUniquesUs, UniqSM )
-import Util ( zipWithEqual )
+import UniqSupply ( returnUs, thenUs, getUniquesUs, UniqSM )
+import Util ( zipWithEqual, notNull )
import Outputable
import List ( zipWith4 )
\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- these comments are rather out of date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-@mkWrapperAndWorker@ produces (A BIT OUT-OF-DATE...):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}
-%* *
-%************************************************************************
-
-\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 = any worth_it ds
- -- 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.
-
- 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
-
-allAbsent :: [Demand] -> Bool
-allAbsent ds = all absent ds
- where
- absent (WwLazy is_absent) = is_absent
- absent (WwUnpack _ True cs) = allAbsent cs
- absent other = False
-\end{code}
-
-
-%************************************************************************
-%* *
\subsection{The worker wrapper core}
%* *
%************************************************************************
\begin{code}
mkWwBodies :: Type -- Type of original function
- -> Arity -- Arity of original function
-> [Demand] -- Strictness of original function
- -> Bool -- True <=> function returns bottom
+ -> DmdResult -- Info about function result
-> [Bool] -- One-shot-ness of the function
- -> CprInfo -- Result of CPR analysis
-> 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
-- let x = (a,b) in
-- E
-mkWwBodies fun_ty arity demands res_bot one_shots cpr_info
- = mkWWargs fun_ty arity demands' res_bot one_shots' `thenUs` \ (wrap_args, wrap_fn_args, work_fn_args, res_ty) ->
- mkWWcpr res_ty cpr_info `thenUs` \ (wrap_fn_cpr, work_fn_cpr, cpr_res_ty) ->
- mkWWstr cpr_res_ty wrap_args `thenUs` \ (work_dmds, wrap_fn_str, work_fn_str) ->
-
- returnUs (work_dmds,
- Note InlineMe . wrap_fn_args . wrap_fn_cpr . wrap_fn_str . Var,
- work_fn_str . work_fn_cpr . work_fn_args)
+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's RHS is now trivial (size 1) we still want the __inline__ to prevent
-- fw from being inlined into f's RHS
where
- demands' = demands ++ repeat wwLazy
one_shots' = one_shots ++ repeat False
\end{code}
%************************************************************************
%* *
+\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}
+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}
%* *
%************************************************************************
-- It chomps bites off foralls, arrows, newtypes
-- and keeps repeating that until it's satisfied the supplied arity
-mkWWargs :: Type -> Arity
- -> [Demand] -> Bool -> [Bool] -- Both these will in due course be derived
- -- from the type. The [Bool] is True for a one-shot arg.
- -- ** Both are infinite, extended with neutral values if necy **
+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 arity demands res_bot one_shots
- | (res_bot || arity > 0) && (not (null tyvars) || n_arg_tys > 0)
- -- If the function returns bottom, we feel free to
- -- build lots of wrapper args:
- -- \x. let v=E in \y. bottom
- -- = \xy. let v=E in bottom
- = getUniquesUs n_args `thenUs` \ wrap_uniqs ->
+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
- (arity - n_args)
- (drop n_args demands)
- res_bot
- (drop n_args one_shots) `thenUs` \ (more_wrap_args, wrap_fn_args, work_fn_args, res_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)
- where
- (tyvars, tau) = splitForAllTys fun_ty
- (arg_tys, body_ty) = splitFunTys tau
- n_arg_tys = length arg_tys
- n_args | res_bot = n_arg_tys
- | otherwise = arity `min` n_arg_tys
- new_fun_ty | n_args == n_arg_tys = body_ty
- | otherwise = mkFunTys (drop n_args arg_tys) body_ty
-
-mkWWargs fun_ty arity demands res_bot one_shots
- = case splitNewType_maybe fun_ty of
- Nothing -> returnUs ([], id, id, fun_ty)
- Just rep_ty -> mkWWargs rep_ty arity demands res_bot 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)
+
+ | 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 (setIdDemandInfo (mkSysLocal SLIT("w") uniq ty) dmd)
+ = 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
%************************************************************************
\begin{code}
-mkWWstr :: Type -- Result type
- -> [Var] -- Wrapper args; have their demand info on them
+mkWWstr :: [Var] -- Wrapper args; have their demand info on them
-- *Includes type variables*
- -> UniqSM ([Demand], -- Demand on worker (value) args
+ -> UniqSM ([Var], -- Worker args
CoreExpr -> CoreExpr, -- Wrapper body, lacking the worker call
-- and without its lambdas
- -- This fn adds the unboxing, and makes the
- -- call passing the unboxed things
+ -- This fn adds the unboxing
CoreExpr -> CoreExpr) -- Worker body, lacking the original body of the function,
- -- but *with* lambdas
+ -- and lacking its lambdas.
+ -- This fn does the reboxing
-mkWWstr res_ty wrap_args
- = mk_ww_str wrap_args `thenUs` \ (work_args, take_apart, put_together) ->
- let
- work_dmds = [idDemandInfo v | v <- work_args, isId v]
- apply_to args fn = mkVarApps fn args
- in
- if not (null work_dmds && isUnLiftedType res_ty) then
- returnUs ( work_dmds,
- take_apart . apply_to work_args,
- mkLams work_args . put_together)
- else
- -- 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 ([wwPrim],
- take_apart . apply_to [realWorldPrimId] . apply_to work_args,
- mkLams work_args . Lam void_arg . put_together)
+----------------------
+nop_fn body = body
- -- Empty case
-mk_ww_str []
- = returnUs ([],
- \ wrapper_body -> wrapper_body,
- \ worker_body -> worker_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)
-mk_ww_str (arg : ds)
+
+----------------------
+-- 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
- = mk_ww_str ds `thenUs` \ (worker_args, wrap_fn, work_fn) ->
- returnUs (arg : worker_args, wrap_fn, work_fn)
+ = returnUs ([arg], nop_fn, nop_fn)
| otherwise
- = case idDemandInfo arg of
+ = case idNewDemandInfo arg of
- -- Absent case
- WwLazy True ->
- mk_ww_str ds `thenUs` \ (worker_args, wrap_fn, work_fn) ->
- returnUs (worker_args, wrap_fn, mk_absent_let arg . work_fn)
+ -- 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
- 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_str" set_worker_arg_info unpk_args cs
- in
- mk_ww_str (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
- (arg_tycon, tycon_arg_tys, data_con, inst_con_arg_tys) = splitProductType "mk_ww_str" (idType arg)
-
+ 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_str 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 (setIdDemandInfo worker_arg demand)
+ set_worker_arg_info worker_arg demand = set_one_shot (setIdNewDemandInfo worker_arg demand)
set_one_shot | isOneShotLambda arg = setOneShotLambda
| otherwise = \x -> x
\begin{code}
mkWWcpr :: Type -- function body type
- -> CprInfo -- CPR analysis results
+ -> DmdResult -- CPR analysis results
-> UniqSM (CoreExpr -> CoreExpr, -- New wrapper
CoreExpr -> CoreExpr, -- New worker
Type) -- Type of worker's body
-mkWWcpr body_ty NoCPRInfo
- = returnUs (id, id, body_ty) -- Must be just the strictness transf.
-
-mkWWcpr body_ty ReturnsCPR
+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
- = getUniquesUs 2 `thenUs` \ [work_uniq, arg_uniq] ->
+ --
+ -- 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 [(DEFAULT, [], mkConApp data_con (map Type tycon_arg_tys ++ [Var arg]))],
- \ body -> Case body work_wild [(DataAlt data_con, [arg], Var arg)],
+ 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
- = getUniquesUs (n_con_args + 2) `thenUs` \ uniqs ->
+ -- 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_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 [(DataAlt ubx_tup_con, args, con_app)],
- \ body -> Case body work_wild [(DataAlt data_con, args, ubx_tup_app)],
+ 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}
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)
+ (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.
-- 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 (mkConApp 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_ww_local uniq ty = mkSysLocal FSLIT("ww") uniq ty
\end{code}
projects / ghc-hetmet.git / blobdiff