\section[WorkWrap]{Worker/wrapper-generating back-end of strictness analyser}
\begin{code}
-module WorkWrap ( wwTopBinds, getWorkerId ) where
+module WorkWrap ( wwTopBinds, mkWrapper ) where
#include "HsVersions.h"
opt_D_dump_worker_wrapper
)
import CoreLint ( beginPass, endPass )
-import CoreUtils ( coreExprType )
+import CoreUtils ( coreExprType, exprArity )
import Const ( Con(..) )
import DataCon ( DataCon )
import MkId ( mkWorkerId )
-import Id ( Id, getIdStrictness, setIdArity,
- setIdStrictness,
+import Id ( Id, idType, getIdStrictness, setIdArity,
+ setIdStrictness, getIdDemandInfo,
setIdWorkerInfo, getIdCprInfo )
import VarSet
-import Type ( splitAlgTyConApp_maybe )
+import Type ( Type, isNewType, splitForAllTys, splitFunTys )
import IdInfo ( mkStrictnessInfo, noStrictnessInfo, StrictnessInfo(..),
CprInfo(..), exactArity
)
-import Demand ( wwLazy )
+import Demand ( Demand, wwLazy )
import SaLib
import UniqSupply ( UniqSupply, initUs_, returnUs, thenUs, mapUs, getUniqueUs, UniqSM )
import UniqSet
workersAndWrappers us top_binds
= initUs_ us $
- mapUs (wwBind True{-top-level-}) top_binds `thenUs` \ top_binds2 ->
- let
- top_binds3 = map make_top_binding top_binds2
- in
- returnUs (concat top_binds3)
- where
- make_top_binding :: WwBinding -> [CoreBind]
-
- make_top_binding (WwLet binds) = binds
+ mapUs wwBind top_binds `thenUs` \ top_binds' ->
+ returnUs (concat top_binds')
\end{code}
%************************************************************************
turn. Non-recursive case first, then recursive...
\begin{code}
-wwBind :: Bool -- True <=> top-level binding
- -> CoreBind
- -> UniqSM WwBinding -- returns a WwBinding intermediate form;
+wwBind :: CoreBind
+ -> UniqSM [CoreBind] -- returns a WwBinding intermediate form;
-- the caller will convert to Expr/Binding,
-- as appropriate.
-wwBind top_level (NonRec binder rhs)
+wwBind (NonRec binder rhs)
= wwExpr rhs `thenUs` \ new_rhs ->
tryWW True {- non-recursive -} binder new_rhs `thenUs` \ new_pairs ->
- returnUs (WwLet [NonRec b e | (b,e) <- new_pairs])
+ returnUs [NonRec b e | (b,e) <- new_pairs]
-- Generated bindings must be non-recursive
-- because the original binding was.
------------------------------
-wwBind top_level (Rec pairs)
+wwBind (Rec pairs)
= mapUs do_one pairs `thenUs` \ new_pairs ->
- returnUs (WwLet [Rec (concat new_pairs)])
+ returnUs [Rec (concat new_pairs)]
where
do_one (binder, rhs) = wwExpr rhs `thenUs` \ new_rhs ->
tryWW False {- recursive -} binder new_rhs
returnUs (Note note new_expr)
wwExpr (Let bind expr)
- = wwBind False{-not top-level-} bind `thenUs` \ intermediate_bind ->
- wwExpr expr `thenUs` \ new_expr ->
- returnUs (mash_ww_bind intermediate_bind new_expr)
- where
- mash_ww_bind (WwLet binds) body = mkLets binds body
- mash_ww_bind (WwCase case_fn) body = case_fn body
+ = wwBind bind `thenUs` \ intermediate_bind ->
+ wwExpr expr `thenUs` \ new_expr ->
+ returnUs (mkLets intermediate_bind new_expr)
wwExpr (Case expr binder alts)
= wwExpr expr `thenUs` \ new_expr ->
-- if two, then a worker and a
-- wrapper.
tryWW non_rec fn_id rhs
- | (non_rec && -- Don't split if its non-recursive and small
- certainlySmallEnoughToInline unfold_guidance
- )
- -- No point in worker/wrappering something that is going to be
- -- INLINEd wholesale anyway. If the strictness analyser is run
- -- twice, this test also prevents wrappers (which are INLINEd)
- -- from being re-done.
-
- || not (do_strict_ww || do_cpr_ww)
+ | (non_rec && -- Don't split if its non-recursive and small
+ certainlySmallEnoughToInline (calcUnfoldingGuidance opt_UF_CreationThreshold rhs)
+ -- No point in worker/wrappering something that is going to be
+ -- INLINEd wholesale anyway. If the strictness analyser is run
+ -- twice, this test also prevents wrappers (which are INLINEd)
+ -- from being re-done.
+ )
+
+ || arity == 0 -- Don't split if it's not a function
+
+ || not (do_strict_ww || do_cpr_ww || do_coerce_ww)
= returnUs [ (fn_id, rhs) ]
| otherwise -- Do w/w split
- = let
- (tyvars, wrap_args, body) = collectTyAndValBinders rhs
- in
- mkWwBodies tyvars wrap_args
- (coreExprType body)
- revised_wrap_args_info
- cpr_info
- `thenUs` \ (wrap_fn, work_fn, work_demands) ->
+ = mkWwBodies fun_ty arity wrap_dmds cpr_info `thenUs` \ (work_args, wrap_fn, work_fn) ->
getUniqueUs `thenUs` \ work_uniq ->
let
- work_rhs = work_fn body
- work_id = mkWorkerId work_uniq fn_id (coreExprType work_rhs) `setIdStrictness`
- (if has_strictness_info then mkStrictnessInfo (work_demands, result_bot)
- else noStrictnessInfo)
+ work_rhs = work_fn rhs
+ work_demands = [getIdDemandInfo v | v <- work_args, isId v]
+ proto_work_id = mkWorkerId work_uniq fn_id (coreExprType work_rhs)
+ work_id | has_strictness = proto_work_id `setIdStrictness` mkStrictnessInfo (work_demands, result_bot)
+ | otherwise = proto_work_id
wrap_rhs = wrap_fn work_id
- wrap_id = fn_id `setIdStrictness`
- (if has_strictness_info then mkStrictnessInfo (revised_wrap_args_info, result_bot)
- else noStrictnessInfo)
+ wrap_id = fn_id `setIdStrictness` wrapper_strictness
`setIdWorkerInfo` Just work_id
- `setIdArity` exactArity (length wrap_args)
+ `setIdArity` exactArity arity
-- Add info to the wrapper:
- -- (a) we want to inline it everywhere
+ -- (a) we want to set its arity
-- (b) we want to pin on its revised strictness info
-- (c) we pin on its worker id
in
returnUs ([(work_id, work_rhs), (wrap_id, wrap_rhs)])
-- Worker first, because wrapper mentions it
where
- strictness_info = getIdStrictness fn_id
- has_strictness_info = case strictness_info of
- StrictnessInfo _ _ -> True
- other -> False
-
- StrictnessInfo wrap_args_info result_bot = strictness_info
+ fun_ty = idType fn_id
+ arity = exprArity rhs
+
+ strictness_info = getIdStrictness fn_id
+ StrictnessInfo arg_demands result_bot = strictness_info
+ has_strictness = case strictness_info of
+ StrictnessInfo _ _ -> True
+ other -> False
- revised_wrap_args_info = if has_strictness_info
- then setUnpackStrategy wrap_args_info
- else repeat wwLazy
+ do_strict_ww = has_strictness && worthSplitting wrap_dmds result_bot
- do_strict_ww = has_strictness_info && worthSplitting revised_wrap_args_info result_bot
+ -- NB: There maybe be more items in arg_demands than arity, because
+ -- the strictness info is semantic and looks through InlineMe and Scc Notes,
+ -- whereas arity does not
+ demands_for_visible_args = take arity arg_demands
+ remaining_arg_demands = drop arity arg_demands
+ wrap_dmds | has_strictness = setUnpackStrategy demands_for_visible_args
+ | otherwise = take arity (repeat wwLazy)
+
+ wrapper_strictness | has_strictness = mkStrictnessInfo (wrap_dmds ++ remaining_arg_demands, result_bot)
+ | otherwise = noStrictnessInfo
+
+ -------------------------------------------------------------
cpr_info = getIdCprInfo fn_id
has_cpr_info = case cpr_info of
CPRInfo _ -> True
other -> False
do_cpr_ww = has_cpr_info
- unfold_guidance = calcUnfoldingGuidance opt_UF_CreationThreshold rhs
-
--- This rather (nay! extremely!) crude function looks at a wrapper function, and
--- snaffles out the worker Id from the wrapper.
--- This is needed when we write an interface file.
--- [May 1999: we used to get the constructors too, but that's no longer
--- necessary, because the renamer hauls in all type decls in
--- their fullness.]
-
--- <Mar 1999 (keving)> - Well, since the addition of the CPR transformation this function
--- got too crude!
--- Now the worker id is stored directly in the id's Info field. We still use this function to
--- snaffle the wrapper's constructors but I don't trust the code to find the worker id.
-getWorkerId :: Id -> CoreExpr -> Id
-getWorkerId wrap_id wrapper_fn
- = work_id wrapper_fn
+
+ -------------------------------------------------------------
+ do_coerce_ww = check_for_coerce arity fun_ty
+
+-- See if there's a Coerce before we run out of arity;
+-- if so, it's worth trying a w/w split. Reason: we find
+-- functions like f = coerce (\s -> e)
+-- and g = \x -> coerce (\s -> e)
+-- and they may have no useful strictness or cpr info, but if we
+-- do the w/w thing we get rid of the coerces.
+
+check_for_coerce arity ty
+ = length arg_tys <= arity && isNewType res_ty
+ -- Don't look further than arity args,
+ -- but if there are arity or fewer, see if there's
+ -- a newtype in the corner
where
+ (_, tau) = splitForAllTys ty
+ (arg_tys, res_ty) = splitFunTys tau
+\end{code}
+
+
+
+%************************************************************************
+%* *
+\subsection{The worker wrapper core}
+%* *
+%************************************************************************
+
+@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).
- work_id wrapper_fn
- = case get_work_id wrapper_fn of
- [] -> case work_id_try2 wrapper_fn of
- [] -> pprPanic "getWorkerId: can't find worker id" (ppr wrap_id)
- [id] -> id
- _ -> pprPanic "getWorkerId: found too many worker ids" (ppr wrap_id)
- [id] -> id
- _ -> pprPanic "getWorkerId: found too many worker ids" (ppr wrap_id)
-
- get_work_id (Lam _ body) = get_work_id body
- get_work_id (Case _ _ [(_,_,rhs@(Case _ _ _))]) = get_work_id rhs
- get_work_id (Case scrut _ [(_,_,rhs)]) = (get_work_id scrut) ++ (get_work_id rhs)
- get_work_id (Note _ body) = get_work_id body
- get_work_id (Let _ body) = get_work_id body
- get_work_id (App (Var work_id) _) = [work_id]
- get_work_id (App fn _) = get_work_id fn
- get_work_id (Var work_id) = []
- get_work_id other = []
-
- work_id_try2 (Lam _ body) = work_id_try2 body
- work_id_try2 (Note _ body) = work_id_try2 body
- work_id_try2 (Let _ body) = work_id_try2 body
- work_id_try2 (App fn _) = work_id_try2 fn
- work_id_try2 (Var work_id) = [work_id]
- work_id_try2 other = []
+\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
+ = mkWwBodies fun_ty arity demands cpr_info `thenUs` \ (_, wrap_fn, _) ->
+ returnUs wrap_fn
\end{code}
+
+
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