2 % (c) The GRASP/AQUA Project, Glasgow University, 1993-1996
4 \section[WorkWrap]{Worker/wrapper-generating back-end of strictness analyser}
7 #include "HsVersions.h"
9 module WorkWrap ( workersAndWrappers ) where
15 import CoreUnfold ( Unfolding, certainlySmallEnoughToInline, calcUnfoldingGuidance )
16 import CmdLineOpts ( opt_UnfoldingCreationThreshold )
18 import CoreUtils ( coreExprType )
19 import Id ( getInlinePragma, getIdStrictness, mkWorkerId,
20 addIdStrictness, addInlinePragma,
23 import IdInfo ( noIdInfo, addUnfoldInfo,
24 mkStrictnessInfo, addStrictnessInfo, StrictnessInfo(..)
27 import UniqSupply ( returnUs, thenUs, mapUs, getUnique, SYN_IE(UniqSM) )
31 We take Core bindings whose binders have their strictness attached (by
32 the front-end of the strictness analyser), and we return some
33 ``plain'' bindings which have been worker/wrapper-ified, meaning:
36 Functions have been split into workers and wrappers where appropriate;
38 Binders' @IdInfos@ have been updated to reflect the existence
39 of these workers/wrappers (this is where we get STRICTNESS pragma
40 info for exported values).
44 workersAndWrappers :: [CoreBinding] -> UniqSM [CoreBinding]
46 workersAndWrappers top_binds
47 = mapUs (wwBind True{-top-level-}) top_binds `thenUs` \ top_binds2 ->
49 top_binds3 = map make_top_binding top_binds2
51 returnUs (concat top_binds3)
53 make_top_binding :: WwBinding -> [CoreBinding]
55 make_top_binding (WwLet binds) = binds
58 %************************************************************************
60 \subsection[wwBind-wwExpr]{@wwBind@ and @wwExpr@}
62 %************************************************************************
64 @wwBind@ works on a binding, trying each \tr{(binder, expr)} pair in
65 turn. Non-recursive case first, then recursive...
68 wwBind :: Bool -- True <=> top-level binding
70 -> UniqSM WwBinding -- returns a WwBinding intermediate form;
71 -- the caller will convert to Expr/Binding,
74 wwBind top_level (NonRec binder rhs)
75 = wwExpr rhs `thenUs` \ new_rhs ->
76 tryWW binder new_rhs `thenUs` \ new_pairs ->
77 returnUs (WwLet [NonRec b e | (b,e) <- new_pairs])
78 -- Generated bindings must be non-recursive
79 -- because the original binding was.
81 ------------------------------
83 wwBind top_level (Rec pairs)
84 = mapUs do_one pairs `thenUs` \ new_pairs ->
85 returnUs (WwLet [Rec (concat new_pairs)])
87 do_one (binder, rhs) = wwExpr rhs `thenUs` \ new_rhs ->
91 @wwExpr@ basically just walks the tree, looking for appropriate
92 annotations that can be used. Remember it is @wwBind@ that does the
93 matching by looking for strict arguments of the correct type.
94 @wwExpr@ is a version that just returns the ``Plain'' Tree.
98 wwExpr :: CoreExpr -> UniqSM CoreExpr
100 wwExpr e@(Var _) = returnUs e
101 wwExpr e@(Lit _) = returnUs e
102 wwExpr e@(Con _ _) = returnUs e
103 wwExpr e@(Prim _ _) = returnUs e
105 wwExpr (Lam binder expr)
106 = wwExpr expr `thenUs` \ new_expr ->
107 returnUs (Lam binder new_expr)
110 = wwExpr f `thenUs` \ new_f ->
111 returnUs (App new_f a)
114 = wwExpr expr `thenUs` \ new_expr ->
115 returnUs (SCC cc new_expr)
117 wwExpr (Coerce c ty expr)
118 = wwExpr expr `thenUs` \ new_expr ->
119 returnUs (Coerce c ty new_expr)
121 wwExpr (Let bind expr)
122 = wwBind False{-not top-level-} bind `thenUs` \ intermediate_bind ->
123 wwExpr expr `thenUs` \ new_expr ->
124 returnUs (mash_ww_bind intermediate_bind new_expr)
126 mash_ww_bind (WwLet binds) body = mkCoLetsNoUnboxed binds body
127 mash_ww_bind (WwCase case_fn) body = case_fn body
129 wwExpr (Case expr alts)
130 = wwExpr expr `thenUs` \ new_expr ->
131 ww_alts alts `thenUs` \ new_alts ->
132 returnUs (Case new_expr new_alts)
134 ww_alts (AlgAlts alts deflt)
135 = mapUs ww_alg_alt alts `thenUs` \ new_alts ->
136 ww_deflt deflt `thenUs` \ new_deflt ->
137 returnUs (AlgAlts new_alts new_deflt)
139 ww_alts (PrimAlts alts deflt)
140 = mapUs ww_prim_alt alts `thenUs` \ new_alts ->
141 ww_deflt deflt `thenUs` \ new_deflt ->
142 returnUs (PrimAlts new_alts new_deflt)
144 ww_alg_alt (con, binders, rhs)
145 = wwExpr rhs `thenUs` \ new_rhs ->
146 returnUs (con, binders, new_rhs)
148 ww_prim_alt (lit, rhs)
149 = wwExpr rhs `thenUs` \ new_rhs ->
150 returnUs (lit, new_rhs)
155 ww_deflt (BindDefault binder rhs)
156 = wwExpr rhs `thenUs` \ new_rhs ->
157 returnUs (BindDefault binder new_rhs)
160 %************************************************************************
162 \subsection[tryWW]{@tryWW@: attempt a worker/wrapper pair}
164 %************************************************************************
166 @tryWW@ just accumulates arguments, converts strictness info from the
167 front-end into the proper form, then calls @mkWwBodies@ to do
170 We have to BE CAREFUL that we don't worker-wrapperize an Id that has
171 already been w-w'd! (You can end up with several liked-named Ids
172 bouncing around at the same time---absolute mischief.) So the
173 criterion we use is: if an Id already has an unfolding (for whatever
174 reason), then we don't w-w it.
176 The only reason this is monadised is for the unique supply.
179 tryWW :: Id -- The fn binder
180 -> CoreExpr -- The bound rhs; its innards
182 -> UniqSM [(Id, CoreExpr)] -- either *one* or *two* pairs;
183 -- if one, then no worker (only
184 -- the orig "wrapper" lives on);
185 -- if two, then a worker and a
188 | (certainlySmallEnoughToInline $
189 calcUnfoldingGuidance (getInlinePragma fn_id)
190 opt_UnfoldingCreationThreshold
193 -- No point in worker/wrappering something that is going to be
194 -- INLINEd wholesale anyway. If the strictness analyser is run
195 -- twice, this test also prevents wrappers (which are INLINEd)
196 -- from being re-done.
198 || not has_strictness_info
199 || not (worthSplitting revised_wrap_args_info)
200 = returnUs [ (fn_id, rhs) ]
202 | otherwise -- Do w/w split
204 (uvars, tyvars, wrap_args, body) = collectBinders rhs
206 mkWwBodies tyvars wrap_args
208 revised_wrap_args_info `thenUs` \ (wrap_fn, work_fn, work_demands) ->
209 getUnique `thenUs` \ work_uniq ->
211 work_rhs = work_fn body
212 work_id = mkWorkerId work_uniq fn_id (coreExprType work_rhs) work_info
213 work_info = noIdInfo `addStrictnessInfo` mkStrictnessInfo work_demands Nothing
215 wrap_rhs = wrap_fn work_id
216 ww_cons = nub (get_ww_cons wrap_rhs)
217 wrap_id = addInlinePragma (fn_id `addIdStrictness`
218 mkStrictnessInfo revised_wrap_args_info (Just (work_id, ww_cons)))
219 -- Add info to the wrapper:
220 -- (a) we want to inline it everywhere
221 -- (b) we want to pin on its revised stricteness info
222 -- (c) we pin on its worker id and the list of constructors mentioned in the wrapper
224 returnUs ([(work_id, work_rhs), (wrap_id, wrap_rhs)])
225 -- Worker first, because wrapper mentions it
227 strictness_info = getIdStrictness fn_id
228 has_strictness_info = case strictness_info of
229 StrictnessInfo _ _ -> True
232 wrap_args_info = case strictness_info of
233 StrictnessInfo args_info _ -> args_info
234 revised_wrap_args_info = setUnpackStrategy wrap_args_info
236 -- This rather crude function snaffles out the constructors needed to
237 -- make the wrapper, so that we can stick them in the strictness info.
238 -- They're only needed if this thing gets exported.
239 get_ww_cons (Lam _ body) = get_ww_cons body
240 get_ww_cons (App fn _) = get_ww_cons fn
241 get_ww_cons (Case _ (AlgAlts [(con,_,rhs)] _)) = con : get_ww_cons rhs
242 get_ww_cons other = []