\section[WwLib]{A library for the ``worker/wrapper'' back-end to the strictness analyser}
\begin{code}
-module WwLib ( mkWwBodies ) where
+module WwLib ( mkWwBodies, mkWWstr, mkWorkerArgs ) where
#include "HsVersions.h"
import CoreSyn
import CoreUtils ( exprType )
import Id ( Id, idType, mkSysLocal, idNewDemandInfo, setIdNewDemandInfo,
- isOneShotLambda, setOneShotLambda,
+ isOneShotLambda, setOneShotLambda, setIdUnfolding,
setIdInfo
)
import IdInfo ( vanillaIdInfo )
import DataCon ( splitProductType_maybe, splitProductType )
-import NewDemand ( Demand(..), Keepity(..), DmdResult(..) )
-import PrelInfo ( realWorldPrimId, aBSENT_ERROR_ID )
-import TysPrim ( realWorldStatePrimTy )
+import NewDemand ( Demand(..), DmdResult(..), Demands(..) )
+import MkId ( realWorldPrimId, voidArgId, mkRuntimeErrorApp, rUNTIME_ERROR_ID )
import TysWiredIn ( tupleCon )
import Type ( Type, isUnLiftedType, mkFunTys,
- splitForAllTys, splitFunTys, splitNewType_maybe, isAlgType
+ splitForAllTys, splitFunTys, splitRecNewType_maybe, isAlgType
)
-import BasicTypes ( 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}
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) ->
- mkWWcpr res_ty res_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)
+ 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 = ...
%************************************************************************
%* *
+\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}
%* *
%************************************************************************
Type) -- Type of wrapper body
mkWWargs fun_ty demands one_shots
- | Just rep_ty <- splitNewType_maybe fun_ty
+ | 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
work_fn_args . Note (Coerce rep_ty fun_ty),
res_ty)
- | not (null demands)
+ | notNull demands
= getUniquesUs `thenUs` \ wrap_uniqs ->
let
- (tyvars, tau) = splitForAllTys fun_ty
- (arg_tys, body_ty) = splitFunTys tau
+ (tyvars, tau) = splitForAllTys fun_ty
+ (arg_tys, body_ty) = splitFunTys tau
n_demands = length demands
n_arg_tys = length arg_tys
val_args = zipWith4 mk_wrap_arg wrap_uniqs arg_tys demands one_shots
wrap_args = tyvars ++ val_args
in
- ASSERT( not (null tyvars) || not (null arg_tys) )
+{- 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) ->
applyToVars vars fn = mkVarApps fn vars
mk_wrap_arg uniq ty dmd one_shot
- = set_one_shot one_shot (setIdNewDemandInfo (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 = [idNewDemandInfo 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 . applyToVars 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 ([Lazy],
- take_apart . applyToVars [realWorldPrimId] . apply_to work_args,
- mkLams work_args . Lam void_arg . put_together)
+----------------------
+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)
- -- Empty case
-mk_ww_str []
- = 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_str (arg : ds)
+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 idNewDemandInfo arg of
-- 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)) ->
- mk_ww_str ds `thenUs` \ (worker_args, wrap_fn, work_fn) ->
- returnUs (worker_args, wrap_fn, mk_absent_let arg . work_fn)
-
- -- Seq and keep
- Seq Keep _ [] -> mk_ww_str ds `thenUs` \ (worker_args, wrap_fn, work_fn) ->
- returnUs (arg : worker_args, mk_seq_case arg . wrap_fn, work_fn)
- -- Pass the arg, no need to rebox
-
- -- Seq and discard
- Seq Drop _ [] -> mk_ww_str ds `thenUs` \ (worker_args, wrap_fn, work_fn) ->
- returnUs (worker_args, mk_seq_case arg . wrap_fn, mk_absent_let arg . work_fn)
- -- Don't pass the arg, build absent arg
+ returnUs ([], nop_fn, mk_absent_let arg)
-- Unpack case
- Seq keep _ cs
+ 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 "mk_ww_str" set_worker_arg_info unpk_args cs
+ 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 = mk_pk_let arg data_con tycon_arg_tys unpk_args
+ rebox_fn = Let (NonRec arg con_app)
+ con_app = mkConApp data_con (map Type tycon_arg_tys ++ map Var unpk_args)
in
- mk_ww_str (unpk_args_w_ds ++ ds) `thenUs` \ (worker_args, wrap_fn, work_fn) ->
- case keep of
- Keep -> returnUs (arg : worker_args, unbox_fn . wrap_fn, work_fn)
- -- Pass the arg, no need to rebox
- Drop -> returnUs (worker_args, unbox_fn . wrap_fn, work_fn . rebox_fn)
+ 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
- | otherwise ->
- WARN( True, ppr arg )
- mk_ww_str ds `thenUs` \ (worker_args, wrap_fn, work_fn) ->
- returnUs (arg : worker_args, wrap_fn, work_fn)
-
+ -- `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
| 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 [(DEFAULT, [], mkConApp data_con (map Type tycon_arg_tys ++ [Var arg]))],
- \ body -> workerCase 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
+ -- 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)
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 -> workerCase 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
-- This transform doesn't move work or allocation
-- from one cost centre to another
-workerCase (Note (SCC cc) e) arg alts = Note (SCC cc) (Case e arg alts)
-workerCase e arg alts = Case e arg alts
+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 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) [(DEFAULT, [], 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 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