#include "HsVersions.h"
-import DynFlags ( DynFlags, DynFlag(..) )
-import Id ( Id, idName, idType, mkUserLocal,
- idInlinePragma, setInlinePragma )
-import TcType ( Type, mkTyVarTy, tcSplitSigmaTy,
- tyVarsOfTypes, tyVarsOfTheta, isClassPred,
- tcCmpType, isUnLiftedType
- )
-import CoreSubst ( Subst, mkEmptySubst, extendTvSubstList, lookupIdSubst,
- substBndr, substBndrs, substTy, substInScope,
- cloneIdBndr, cloneIdBndrs, cloneRecIdBndrs
- )
+import Id
+import TcType
+import CoreSubst
+import CoreUnfold ( mkUnfolding, mkInlineRule )
import VarSet
import VarEnv
import CoreSyn
-import CoreUtils ( applyTypeToArgs, mkPiTypes )
+import Rules
+import CoreUtils ( exprIsTrivial, applyTypeToArgs, mkPiTypes )
import CoreFVs ( exprFreeVars, exprsFreeVars, idFreeVars )
-import CoreTidy ( tidyRules )
-import CoreLint ( showPass, endPass )
-import Rules ( addIdSpecialisations, mkLocalRule, lookupRule, emptyRuleBase, rulesOfBinds )
-import PprCore ( pprRules )
-import UniqSupply ( UniqSupply,
- UniqSM, initUs_, thenUs, returnUs, getUniqueUs,
- getUs, mapUs
- )
+import UniqSupply ( UniqSupply, UniqSM, initUs_, MonadUnique(..) )
import Name
import MkId ( voidArgId, realWorldPrimId )
-import FiniteMap
-import Maybes ( catMaybes, maybeToBool )
-import ErrUtils ( dumpIfSet_dyn )
-import BasicTypes ( Activation( AlwaysActive ) )
+import Maybes ( catMaybes, isJust )
+import BasicTypes ( isNeverActive, inlinePragmaActivation )
import Bag
-import List ( partition )
-import Util ( zipEqual, zipWithEqual, cmpList, lengthIs,
- equalLength, lengthAtLeast, notNull )
+import Util
import Outputable
import FastString
-infixr 9 `thenSM`
+import Data.Map (Map)
+import qualified Data.Map as Map
+import qualified FiniteMap as Map
\end{code}
%************************************************************************
Still, this is no great hardship, because we intend to eliminate
overloading altogether anyway!
-
-
A note about non-tyvar dictionaries
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Some Ids have types like
But it is simpler and more uniform to specialise wrt these dicts too;
and in future GHC is likely to support full fledged type signatures
like
- f ;: Eq [(a,b)] => ...
+ f :: Eq [(a,b)] => ...
%************************************************************************
%************************************************************************
\begin{code}
-specProgram :: DynFlags -> UniqSupply -> [CoreBind] -> IO [CoreBind]
-specProgram dflags us binds
- = do
- showPass dflags "Specialise"
-
- let binds' = initSM us (go binds `thenSM` \ (binds', uds') ->
- returnSM (dumpAllDictBinds uds' binds'))
-
- endPass dflags "Specialise" Opt_D_dump_spec binds'
-
- dumpIfSet_dyn dflags Opt_D_dump_rules "Top-level specialisations"
- (pprRules (tidyRules emptyTidyEnv (rulesOfBinds binds')))
-
- return binds'
+specProgram :: UniqSupply -> [CoreBind] -> [CoreBind]
+specProgram us binds = initSM us $
+ do { (binds', uds') <- go binds
+ ; return (wrapDictBinds (ud_binds uds') binds') }
where
-- We need to start with a Subst that knows all the things
-- that are in scope, so that the substitution engine doesn't
-- accidentally re-use a unique that's already in use
-- Easiest thing is to do it all at once, as if all the top-level
-- decls were mutually recursive
- top_subst = mkEmptySubst (mkInScopeSet (mkVarSet (bindersOfBinds binds)))
+ top_subst = mkEmptySubst (mkInScopeSet (mkVarSet (bindersOfBinds binds)))
- go [] = returnSM ([], emptyUDs)
- go (bind:binds) = go binds `thenSM` \ (binds', uds) ->
- specBind top_subst bind uds `thenSM` \ (bind', uds') ->
- returnSM (bind' ++ binds', uds')
+ go [] = return ([], emptyUDs)
+ go (bind:binds) = do (binds', uds) <- go binds
+ (bind', uds') <- specBind top_subst bind uds
+ return (bind' ++ binds', uds')
\end{code}
%************************************************************************
\begin{code}
specVar :: Subst -> Id -> CoreExpr
-specVar subst v = lookupIdSubst subst v
+specVar subst v = lookupIdSubst (text "specVar") subst v
specExpr :: Subst -> CoreExpr -> SpecM (CoreExpr, UsageDetails)
-- We carry a substitution down:
--- a) we must clone any binding that might flaot outwards,
+-- a) we must clone any binding that might float outwards,
-- to avoid name clashes
-- b) we carry a type substitution to use when analysing
-- the RHS of specialised bindings (no type-let!)
---------------- First the easy cases --------------------
-specExpr subst (Type ty) = returnSM (Type (substTy subst ty), emptyUDs)
-specExpr subst (Var v) = returnSM (specVar subst v, emptyUDs)
-specExpr subst (Lit lit) = returnSM (Lit lit, emptyUDs)
-specExpr subst (Cast e co) =
- specExpr subst e `thenSM` \ (e', uds) ->
- returnSM ((Cast e' (substTy subst co)), uds)
-specExpr subst (Note note body)
- = specExpr subst body `thenSM` \ (body', uds) ->
- returnSM (Note (specNote subst note) body', uds)
+specExpr subst (Type ty) = return (Type (CoreSubst.substTy subst ty), emptyUDs)
+specExpr subst (Var v) = return (specVar subst v, emptyUDs)
+specExpr _ (Lit lit) = return (Lit lit, emptyUDs)
+specExpr subst (Cast e co) = do
+ (e', uds) <- specExpr subst e
+ return ((Cast e' (CoreSubst.substTy subst co)), uds)
+specExpr subst (Note note body) = do
+ (body', uds) <- specExpr subst body
+ return (Note (specNote subst note) body', uds)
---------------- Applications might generate a call instance --------------------
-specExpr subst expr@(App fun arg)
+specExpr subst expr@(App {})
= go expr []
where
- go (App fun arg) args = specExpr subst arg `thenSM` \ (arg', uds_arg) ->
- go fun (arg':args) `thenSM` \ (fun', uds_app) ->
- returnSM (App fun' arg', uds_arg `plusUDs` uds_app)
+ go (App fun arg) args = do (arg', uds_arg) <- specExpr subst arg
+ (fun', uds_app) <- go fun (arg':args)
+ return (App fun' arg', uds_arg `plusUDs` uds_app)
go (Var f) args = case specVar subst f of
- Var f' -> returnSM (Var f', mkCallUDs subst f' args)
- e' -> returnSM (e', emptyUDs) -- I don't expect this!
- go other args = specExpr subst other
+ Var f' -> return (Var f', mkCallUDs f' args)
+ e' -> return (e', emptyUDs) -- I don't expect this!
+ go other _ = specExpr subst other
---------------- Lambda/case require dumping of usage details --------------------
-specExpr subst e@(Lam _ _)
- = specExpr subst' body `thenSM` \ (body', uds) ->
- let
- (filtered_uds, body'') = dumpUDs bndrs' uds body'
- in
- returnSM (mkLams bndrs' body'', filtered_uds)
+specExpr subst e@(Lam _ _) = do
+ (body', uds) <- specExpr subst' body
+ let (free_uds, dumped_dbs) = dumpUDs bndrs' uds
+ return (mkLams bndrs' (wrapDictBindsE dumped_dbs body'), free_uds)
where
(bndrs, body) = collectBinders e
(subst', bndrs') = substBndrs subst bndrs
-- More efficient to collect a group of binders together all at once
-- and we don't want to split a lambda group with dumped bindings
-specExpr subst (Case scrut case_bndr ty alts)
- = specExpr subst scrut `thenSM` \ (scrut', uds_scrut) ->
- mapAndCombineSM spec_alt alts `thenSM` \ (alts', uds_alts) ->
- returnSM (Case scrut' case_bndr' (substTy subst ty) alts', uds_scrut `plusUDs` uds_alts)
- where
- (subst_alt, case_bndr') = substBndr subst case_bndr
- -- No need to clone case binder; it can't float like a let(rec)
-
- spec_alt (con, args, rhs)
- = specExpr subst_rhs rhs `thenSM` \ (rhs', uds) ->
- let
- (uds', rhs'') = dumpUDs args uds rhs'
- in
- returnSM ((con, args', rhs''), uds')
- where
- (subst_rhs, args') = substBndrs subst_alt args
+specExpr subst (Case scrut case_bndr ty alts)
+ = do { (scrut', scrut_uds) <- specExpr subst scrut
+ ; (scrut'', case_bndr', alts', alts_uds)
+ <- specCase subst scrut' case_bndr alts
+ ; return (Case scrut'' case_bndr' (CoreSubst.substTy subst ty) alts'
+ , scrut_uds `plusUDs` alts_uds) }
---------------- Finally, let is the interesting case --------------------
-specExpr subst (Let bind body)
- = -- Clone binders
- cloneBindSM subst bind `thenSM` \ (rhs_subst, body_subst, bind') ->
-
- -- Deal with the body
- specExpr body_subst body `thenSM` \ (body', body_uds) ->
+specExpr subst (Let bind body) = do
+ -- Clone binders
+ (rhs_subst, body_subst, bind') <- cloneBindSM subst bind
+
+ -- Deal with the body
+ (body', body_uds) <- specExpr body_subst body
- -- Deal with the bindings
- specBind rhs_subst bind' body_uds `thenSM` \ (binds', uds) ->
+ -- Deal with the bindings
+ (binds', uds) <- specBind rhs_subst bind' body_uds
- -- All done
- returnSM (foldr Let body' binds', uds)
+ -- All done
+ return (foldr Let body' binds', uds)
-- Must apply the type substitution to coerceions
-specNote subst note = note
+specNote :: Subst -> Note -> Note
+specNote _ note = note
+
+
+specCase :: Subst
+ -> CoreExpr -- Scrutinee, already done
+ -> Id -> [CoreAlt]
+ -> SpecM ( CoreExpr -- New scrutinee
+ , Id
+ , [CoreAlt]
+ , UsageDetails)
+specCase subst scrut' case_bndr [(con, args, rhs)]
+ | isDictId case_bndr -- See Note [Floating dictionaries out of cases]
+ , interestingDict scrut'
+ , not (isDeadBinder case_bndr && null sc_args')
+ = do { (case_bndr_flt : sc_args_flt) <- mapM clone_me (case_bndr' : sc_args')
+
+ ; let sc_rhss = [ Case (Var case_bndr_flt) case_bndr' (idType sc_arg')
+ [(con, args', Var sc_arg')]
+ | sc_arg' <- sc_args' ]
+
+ -- Extend the substitution for RHS to map the *original* binders
+ -- to their floated verions. Attach an unfolding to these floated
+ -- binders so they look interesting to interestingDict
+ mb_sc_flts :: [Maybe DictId]
+ mb_sc_flts = map (lookupVarEnv clone_env) args'
+ clone_env = zipVarEnv sc_args' (zipWith add_unf sc_args_flt sc_rhss)
+ subst_prs = (case_bndr, Var (add_unf case_bndr_flt scrut'))
+ : [ (arg, Var sc_flt)
+ | (arg, Just sc_flt) <- args `zip` mb_sc_flts ]
+ subst_rhs' = extendIdSubstList subst_rhs subst_prs
+
+ ; (rhs', rhs_uds) <- specExpr subst_rhs' rhs
+ ; let scrut_bind = mkDB (NonRec case_bndr_flt scrut')
+ case_bndr_set = unitVarSet case_bndr_flt
+ sc_binds = [(NonRec sc_arg_flt sc_rhs, case_bndr_set)
+ | (sc_arg_flt, sc_rhs) <- sc_args_flt `zip` sc_rhss ]
+ flt_binds = scrut_bind : sc_binds
+ (free_uds, dumped_dbs) = dumpUDs (case_bndr':args') rhs_uds
+ all_uds = flt_binds `addDictBinds` free_uds
+ alt' = (con, args', wrapDictBindsE dumped_dbs rhs')
+ ; return (Var case_bndr_flt, case_bndr', [alt'], all_uds) }
+ where
+ (subst_rhs, (case_bndr':args')) = substBndrs subst (case_bndr:args)
+ sc_args' = filter is_flt_sc_arg args'
+
+ clone_me bndr = do { uniq <- getUniqueM
+ ; return (mkUserLocal occ uniq ty loc) }
+ where
+ name = idName bndr
+ ty = idType bndr
+ occ = nameOccName name
+ loc = getSrcSpan name
+
+ add_unf sc_flt sc_rhs -- Sole purpose: make sc_flt respond True to interestingDictId
+ = setIdUnfolding sc_flt (mkUnfolding False False sc_rhs)
+
+ arg_set = mkVarSet args'
+ is_flt_sc_arg var = isId var
+ && not (isDeadBinder var)
+ && isDictTy var_ty
+ && not (tyVarsOfType var_ty `intersectsVarSet` arg_set)
+ where
+ var_ty = idType var
+
+
+specCase subst scrut case_bndr alts
+ = do { (alts', uds_alts) <- mapAndCombineSM spec_alt alts
+ ; return (scrut, case_bndr', alts', uds_alts) }
+ where
+ (subst_alt, case_bndr') = substBndr subst case_bndr
+ spec_alt (con, args, rhs) = do
+ (rhs', uds) <- specExpr subst_rhs rhs
+ let (free_uds, dumped_dbs) = dumpUDs (case_bndr' : args') uds
+ return ((con, args', wrapDictBindsE dumped_dbs rhs'), free_uds)
+ where
+ (subst_rhs, args') = substBndrs subst_alt args
\end{code}
+Note [Floating dictionaries out of cases]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider
+ g = \d. case d of { MkD sc ... -> ...(f sc)... }
+Naively we can't float d2's binding out of the case expression,
+because 'sc' is bound by the case, and that in turn means we can't
+specialise f, which seems a pity.
+
+So we invert the case, by floating out a binding
+for 'sc_flt' thus:
+ sc_flt = case d of { MkD sc ... -> sc }
+Now we can float the call instance for 'f'. Indeed this is just
+what'll happen if 'sc' was originally bound with a let binding,
+but case is more efficient, and necessary with equalities. So it's
+good to work with both.
+
+You might think that this won't make any difference, because the
+call instance will only get nuked by the \d. BUT if 'g' itself is
+specialised, then transitively we should be able to specialise f.
+
+In general, given
+ case e of cb { MkD sc ... -> ...(f sc)... }
+we transform to
+ let cb_flt = e
+ sc_flt = case cb_flt of { MkD sc ... -> sc }
+ in
+ case cb_flt of bg { MkD sc ... -> ....(f sc_flt)... }
+
+The "_flt" things are the floated binds; we use the current substitution
+to substitute sc -> sc_flt in the RHS
+
%************************************************************************
%* *
\subsubsection{Dealing with a binding}
-> SpecM ([CoreBind], -- New bindings
UsageDetails) -- And info to pass upstream
-specBind rhs_subst bind body_uds
- = specBindItself rhs_subst bind (calls body_uds) `thenSM` \ (bind', bind_uds) ->
- let
- bndrs = bindersOf bind
- all_uds = zapCalls bndrs (body_uds `plusUDs` bind_uds)
- -- It's important that the `plusUDs` is this way round,
- -- because body_uds may bind dictionaries that are
- -- used in the calls passed to specDefn. So the
- -- dictionary bindings in bind_uds may mention
- -- dictionaries bound in body_uds.
- in
- case splitUDs bndrs all_uds of
-
- (_, ([],[])) -- This binding doesn't bind anything needed
- -- in the UDs, so put the binding here
- -- This is the case for most non-dict bindings, except
- -- for the few that are mentioned in a dict binding
- -- that is floating upwards in body_uds
- -> returnSM ([bind'], all_uds)
-
- (float_uds, (dict_binds, calls)) -- This binding is needed in the UDs, so float it out
- -> returnSM ([], float_uds `plusUDs` mkBigUD bind' dict_binds calls)
-
-
--- A truly gruesome function
-mkBigUD bind@(NonRec _ _) dbs calls
- = -- Common case: non-recursive and no specialisations
- -- (if there were any specialistions it would have been made recursive)
- MkUD { dict_binds = listToBag (mkDB bind : dbs),
- calls = listToCallDetails calls }
-
-mkBigUD bind dbs calls
- = -- General case
- MkUD { dict_binds = unitBag (mkDB (Rec (bind_prs bind ++ dbsToPairs dbs))),
- -- Make a huge Rec
- calls = listToCallDetails calls }
- where
- bind_prs (NonRec b r) = [(b,r)]
- bind_prs (Rec prs) = prs
-
- dbsToPairs [] = []
- dbsToPairs ((bind,_):dbs) = bind_prs bind ++ dbsToPairs dbs
-
--- specBindItself deals with the RHS, specialising it according
--- to the calls found in the body (if any)
-specBindItself rhs_subst (NonRec bndr rhs) call_info
- = specDefn rhs_subst call_info (bndr,rhs) `thenSM` \ ((bndr',rhs'), spec_defns, spec_uds) ->
- let
- new_bind | null spec_defns = NonRec bndr' rhs'
- | otherwise = Rec ((bndr',rhs'):spec_defns)
- -- bndr' mentions the spec_defns in its SpecEnv
- -- Not sure why we couln't just put the spec_defns first
- in
- returnSM (new_bind, spec_uds)
-
-specBindItself rhs_subst (Rec pairs) call_info
- = mapSM (specDefn rhs_subst call_info) pairs `thenSM` \ stuff ->
- let
- (pairs', spec_defns_s, spec_uds_s) = unzip3 stuff
- spec_defns = concat spec_defns_s
- spec_uds = plusUDList spec_uds_s
- new_bind = Rec (spec_defns ++ pairs')
- in
- returnSM (new_bind, spec_uds)
-
-
-specDefn :: Subst -- Subst to use for RHS
- -> CallDetails -- Info on how it is used in its scope
- -> (Id, CoreExpr) -- The thing being bound and its un-processed RHS
- -> SpecM ((Id, CoreExpr), -- The thing and its processed RHS
- -- the Id may now have specialisations attached
+-- Returned UsageDetails:
+-- No calls for binders of this bind
+specBind rhs_subst (NonRec fn rhs) body_uds
+ = do { (rhs', rhs_uds) <- specExpr rhs_subst rhs
+ ; (fn', spec_defns, body_uds1) <- specDefn rhs_subst body_uds fn rhs
+
+ ; let pairs = spec_defns ++ [(fn', rhs')]
+ -- fn' mentions the spec_defns in its rules,
+ -- so put the latter first
+
+ combined_uds = body_uds1 `plusUDs` rhs_uds
+ -- This way round a call in rhs_uds of a function f
+ -- at type T will override a call of f at T in body_uds1; and
+ -- that is good because it'll tend to keep "earlier" calls
+ -- See Note [Specialisation of dictionary functions]
+
+ (free_uds, dump_dbs, float_all) = dumpBindUDs [fn] combined_uds
+ -- See Note [From non-recursive to recursive]
+
+ final_binds | isEmptyBag dump_dbs = [NonRec b r | (b,r) <- pairs]
+ | otherwise = [Rec (flattenDictBinds dump_dbs pairs)]
+
+ ; if float_all then
+ -- Rather than discard the calls mentioning the bound variables
+ -- we float this binding along with the others
+ return ([], free_uds `snocDictBinds` final_binds)
+ else
+ -- No call in final_uds mentions bound variables,
+ -- so we can just leave the binding here
+ return (final_binds, free_uds) }
+
+
+specBind rhs_subst (Rec pairs) body_uds
+ -- Note [Specialising a recursive group]
+ = do { let (bndrs,rhss) = unzip pairs
+ ; (rhss', rhs_uds) <- mapAndCombineSM (specExpr rhs_subst) rhss
+ ; let scope_uds = body_uds `plusUDs` rhs_uds
+ -- Includes binds and calls arising from rhss
+
+ ; (bndrs1, spec_defns1, uds1) <- specDefns rhs_subst scope_uds pairs
+
+ ; (bndrs3, spec_defns3, uds3)
+ <- if null spec_defns1 -- Common case: no specialisation
+ then return (bndrs1, [], uds1)
+ else do { -- Specialisation occurred; do it again
+ (bndrs2, spec_defns2, uds2)
+ <- specDefns rhs_subst uds1 (bndrs1 `zip` rhss)
+ ; return (bndrs2, spec_defns2 ++ spec_defns1, uds2) }
+
+ ; let (final_uds, dumped_dbs, float_all) = dumpBindUDs bndrs uds3
+ bind = Rec (flattenDictBinds dumped_dbs $
+ spec_defns3 ++ zip bndrs3 rhss')
+
+ ; if float_all then
+ return ([], final_uds `snocDictBind` bind)
+ else
+ return ([bind], final_uds) }
+
+
+---------------------------
+specDefns :: Subst
+ -> UsageDetails -- Info on how it is used in its scope
+ -> [(Id,CoreExpr)] -- The things being bound and their un-processed RHS
+ -> SpecM ([Id], -- Original Ids with RULES added
+ [(Id,CoreExpr)], -- Extra, specialised bindings
+ UsageDetails) -- Stuff to fling upwards from the specialised versions
+
+-- Specialise a list of bindings (the contents of a Rec), but flowing usages
+-- upwards binding by binding. Example: { f = ...g ...; g = ...f .... }
+-- Then if the input CallDetails has a specialised call for 'g', whose specialisation
+-- in turn generates a specialised call for 'f', we catch that in this one sweep.
+-- But not vice versa (it's a fixpoint problem).
+
+specDefns _subst uds []
+ = return ([], [], uds)
+specDefns subst uds ((bndr,rhs):pairs)
+ = do { (bndrs1, spec_defns1, uds1) <- specDefns subst uds pairs
+ ; (bndr1, spec_defns2, uds2) <- specDefn subst uds1 bndr rhs
+ ; return (bndr1 : bndrs1, spec_defns1 ++ spec_defns2, uds2) }
+
+---------------------------
+specDefn :: Subst
+ -> UsageDetails -- Info on how it is used in its scope
+ -> Id -> CoreExpr -- The thing being bound and its un-processed RHS
+ -> SpecM (Id, -- Original Id with added RULES
[(Id,CoreExpr)], -- Extra, specialised bindings
- UsageDetails -- Stuff to fling upwards from the RHS and its
- ) -- specialised versions
+ UsageDetails) -- Stuff to fling upwards from the specialised versions
-specDefn subst calls (fn, rhs)
+specDefn subst body_uds fn rhs
-- The first case is the interesting one
| rhs_tyvars `lengthIs` n_tyvars -- Rhs of fn's defn has right number of big lambdas
&& rhs_ids `lengthAtLeast` n_dicts -- and enough dict args
&& notNull calls_for_me -- And there are some calls to specialise
+ && not (isNeverActive (idInlineActivation fn))
+ -- Don't specialise NOINLINE things
+ -- See Note [Auto-specialisation and RULES]
-- && not (certainlyWillInline (idUnfolding fn)) -- And it's not small
-- See Note [Inline specialisation] for why we do not
-- switch off specialisation for inline functions
- = -- Specialise the body of the function
- specExpr subst rhs `thenSM` \ (rhs', rhs_uds) ->
-
- -- Make a specialised version for each call in calls_for_me
- mapSM spec_call calls_for_me `thenSM` \ stuff ->
- let
- (spec_defns, spec_uds, spec_rules) = unzip3 stuff
-
- fn' = addIdSpecialisations fn spec_rules
- in
- returnSM ((fn',rhs'),
- spec_defns,
- rhs_uds `plusUDs` plusUDList spec_uds)
+ = -- pprTrace "specDefn: some" (ppr fn $$ ppr calls_for_me) $
+ do { -- Make a specialised version for each call in calls_for_me
+ stuff <- mapM spec_call calls_for_me
+ ; let (spec_defns, spec_uds, spec_rules) = unzip3 (catMaybes stuff)
+ fn' = addIdSpecialisations fn spec_rules
+ final_uds = body_uds_without_me `plusUDs` plusUDList spec_uds
+ -- It's important that the `plusUDs` is this way
+ -- round, because body_uds_without_me may bind
+ -- dictionaries that are used in calls_for_me passed
+ -- to specDefn. So the dictionary bindings in
+ -- spec_uds may mention dictionaries bound in
+ -- body_uds_without_me
+
+ ; return (fn', spec_defns, final_uds) }
| otherwise -- No calls or RHS doesn't fit our preconceptions
- = WARN( notNull calls_for_me, ptext SLIT("Missed specialisation opportunity for") <+> ppr fn )
+ = WARN( notNull calls_for_me, ptext (sLit "Missed specialisation opportunity for") <+> ppr fn )
-- Note [Specialisation shape]
- specExpr subst rhs `thenSM` \ (rhs', rhs_uds) ->
- returnSM ((fn, rhs'), [], rhs_uds)
+ -- pprTrace "specDefn: none" (ppr fn $$ ppr calls_for_me) $
+ return (fn, [], body_uds_without_me)
where
fn_type = idType fn
+ fn_arity = idArity fn
+ fn_unf = realIdUnfolding fn -- Ignore loop-breaker-ness here
(tyvars, theta, _) = tcSplitSigmaTy fn_type
n_tyvars = length tyvars
n_dicts = length theta
- inline_prag = idInlinePragma fn
+ inl_act = inlinePragmaActivation (idInlinePragma fn)
+
+ -- Figure out whether the function has an INLINE pragma
+ -- See Note [Inline specialisations]
+ fn_has_inline_rule :: Maybe Bool -- Derive sat-flag from existing thing
+ fn_has_inline_rule = case isInlineRule_maybe fn_unf of
+ Just (_,sat) -> Just sat
+ Nothing -> Nothing
+
+ spec_arity = unfoldingArity fn_unf - n_dicts -- Arity of the *specialised* inline rule
- -- It's important that we "see past" any INLINE pragma
- -- else we'll fail to specialise an INLINE thing
- (inline_rhs, rhs_inside) = dropInline rhs
- (rhs_tyvars, rhs_ids, rhs_body) = collectTyAndValBinders rhs_inside
+ (rhs_tyvars, rhs_ids, rhs_body) = collectTyAndValBinders rhs
- rhs_dicts = take n_dicts rhs_ids
- rhs_bndrs = rhs_tyvars ++ rhs_dicts
- body = mkLams (drop n_dicts rhs_ids) rhs_body
+ (body_uds_without_me, calls_for_me) = callsForMe fn body_uds
+
+ rhs_dict_ids = take n_dicts rhs_ids
+ body = mkLams (drop n_dicts rhs_ids) rhs_body
-- Glue back on the non-dict lambdas
- calls_for_me = case lookupFM calls fn of
- Nothing -> []
- Just cs -> fmToList cs
+ already_covered :: [CoreExpr] -> Bool
+ already_covered args -- Note [Specialisations already covered]
+ = isJust (lookupRule (const True) realIdUnfolding
+ (substInScope subst)
+ fn args (idCoreRules fn))
+
+ mk_ty_args :: [Maybe Type] -> [CoreExpr]
+ mk_ty_args call_ts = zipWithEqual "spec_call" mk_ty_arg rhs_tyvars call_ts
+ where
+ mk_ty_arg rhs_tyvar Nothing = Type (mkTyVarTy rhs_tyvar)
+ mk_ty_arg _ (Just ty) = Type ty
----------------------------------------------------------
-- Specialise to one particular call pattern
- spec_call :: (CallKey, ([DictExpr], VarSet)) -- Call instance
- -> SpecM ((Id,CoreExpr), -- Specialised definition
- UsageDetails, -- Usage details from specialised body
- CoreRule) -- Info for the Id's SpecEnv
- spec_call (CallKey call_ts, (call_ds, call_fvs))
+ spec_call :: CallInfo -- Call instance
+ -> SpecM (Maybe ((Id,CoreExpr), -- Specialised definition
+ UsageDetails, -- Usage details from specialised body
+ CoreRule)) -- Info for the Id's SpecEnv
+ spec_call (CallKey call_ts, (call_ds, _))
= ASSERT( call_ts `lengthIs` n_tyvars && call_ds `lengthIs` n_dicts )
- -- Calls are only recorded for properly-saturated applications
- -- Suppose f's defn is f = /\ a b c d -> \ d1 d2 -> rhs
- -- Supppose the call is for f [Just t1, Nothing, Just t3, Nothing] [dx1, dx2]
+ -- Suppose f's defn is f = /\ a b c -> \ d1 d2 -> rhs
+ -- Supppose the call is for f [Just t1, Nothing, Just t3] [dx1, dx2]
-- Construct the new binding
- -- f1 = SUBST[a->t1,c->t3, d1->d1', d2->d2'] (/\ b d -> rhs)
+ -- f1 = SUBST[a->t1,c->t3, d1->d1', d2->d2'] (/\ b -> rhs)
-- PLUS the usage-details
-- { d1' = dx1; d2' = dx2 }
- -- where d1', d2' are cloned versions of d1,d2, with the type substitution applied.
+ -- where d1', d2' are cloned versions of d1,d2, with the type substitution
+ -- applied. These auxiliary bindings just avoid duplication of dx1, dx2
--
-- Note that the substitution is applied to the whole thing.
-- This is convenient, but just slightly fragile. Notably:
- -- * There had better be no name clashes in a/b/c/d
- --
- let
- -- poly_tyvars = [b,d] in the example above
+ -- * There had better be no name clashes in a/b/c
+ do { let
+ -- poly_tyvars = [b] in the example above
-- spec_tyvars = [a,c]
- -- ty_args = [t1,b,t3,d]
- poly_tyvars = [tv | (tv, Nothing) <- rhs_tyvars `zip` call_ts]
- spec_tyvars = [tv | (tv, Just _) <- rhs_tyvars `zip` call_ts]
- ty_args = zipWithEqual "spec_call" mk_ty_arg rhs_tyvars call_ts
- where
- mk_ty_arg rhs_tyvar Nothing = Type (mkTyVarTy rhs_tyvar)
- mk_ty_arg rhs_tyvar (Just ty) = Type ty
- rhs_subst = extendTvSubstList subst (spec_tyvars `zip` [ty | Just ty <- call_ts])
- in
- cloneBinders rhs_subst rhs_dicts `thenSM` \ (rhs_subst', rhs_dicts') ->
- let
- inst_args = ty_args ++ map Var rhs_dicts'
-
- -- Figure out the type of the specialised function
- body_ty = applyTypeToArgs rhs fn_type inst_args
- (lam_args, app_args) -- Add a dummy argument if body_ty is unlifted
- | isUnLiftedType body_ty -- C.f. WwLib.mkWorkerArgs
- = (poly_tyvars ++ [voidArgId], poly_tyvars ++ [realWorldPrimId])
- | otherwise = (poly_tyvars, poly_tyvars)
- spec_id_ty = mkPiTypes lam_args body_ty
- in
- newIdSM fn spec_id_ty `thenSM` \ spec_f ->
- specExpr rhs_subst' (mkLams lam_args body) `thenSM` \ (spec_rhs, rhs_uds) ->
- let
+ -- ty_args = [t1,b,t3]
+ poly_tyvars = [tv | (tv, Nothing) <- rhs_tyvars `zip` call_ts]
+ spec_tv_binds = [(tv,ty) | (tv, Just ty) <- rhs_tyvars `zip` call_ts]
+ spec_ty_args = map snd spec_tv_binds
+ ty_args = mk_ty_args call_ts
+ rhs_subst = CoreSubst.extendTvSubstList subst spec_tv_binds
+
+ ; (rhs_subst1, inst_dict_ids) <- newDictBndrs rhs_subst rhs_dict_ids
+ -- Clone rhs_dicts, including instantiating their types
+
+ ; let (rhs_subst2, dx_binds) = bindAuxiliaryDicts rhs_subst1 $
+ (my_zipEqual rhs_dict_ids inst_dict_ids call_ds)
+ inst_args = ty_args ++ map Var inst_dict_ids
+
+ ; if already_covered inst_args then
+ return Nothing
+ else do
+ { -- Figure out the type of the specialised function
+ let body_ty = applyTypeToArgs rhs fn_type inst_args
+ (lam_args, app_args) -- Add a dummy argument if body_ty is unlifted
+ | isUnLiftedType body_ty -- C.f. WwLib.mkWorkerArgs
+ = (poly_tyvars ++ [voidArgId], poly_tyvars ++ [realWorldPrimId])
+ | otherwise = (poly_tyvars, poly_tyvars)
+ spec_id_ty = mkPiTypes lam_args body_ty
+
+ ; spec_f <- newSpecIdSM fn spec_id_ty
+ ; (spec_rhs, rhs_uds) <- specExpr rhs_subst2 (mkLams lam_args body)
+ ; let
-- The rule to put in the function's specialisation is:
- -- forall b,d, d1',d2'. f t1 b t3 d d1' d2' = f1 b d
- spec_env_rule = mkLocalRule (mkFastString ("SPEC " ++ showSDoc (ppr fn)))
- AlwaysActive (idName fn)
- (poly_tyvars ++ rhs_dicts')
- inst_args
- (mkVarApps (Var spec_f) app_args)
+ -- forall b, d1',d2'. f t1 b t3 d1' d2' = f1 b
+ rule_name = mkFastString ("SPEC " ++ showSDoc (ppr fn <+> ppr spec_ty_args))
+ spec_env_rule = mkLocalRule
+ rule_name
+ inl_act -- Note [Auto-specialisation and RULES]
+ (idName fn)
+ (poly_tyvars ++ inst_dict_ids)
+ inst_args
+ (mkVarApps (Var spec_f) app_args)
-- Add the { d1' = dx1; d2' = dx2 } usage stuff
- final_uds = foldr addDictBind rhs_uds (my_zipEqual "spec_call" rhs_dicts' call_ds)
-
- spec_pr | inline_rhs = (spec_f `setInlinePragma` inline_prag, Note InlineMe spec_rhs)
- | otherwise = (spec_f, spec_rhs)
- in
- returnSM (spec_pr, final_uds, spec_env_rule)
-
+ final_uds = foldr consDictBind rhs_uds dx_binds
+
+ -- Adding arity information just propagates it a bit faster
+ -- See Note [Arity decrease] in Simplify
+ -- Copy InlinePragma information from the parent Id.
+ -- So if f has INLINE[1] so does spec_f
+ spec_f_w_arity = spec_f `setIdArity` max 0 (fn_arity - n_dicts)
+ `setInlineActivation` inl_act
+
+ -- Add an InlineRule if the parent has one
+ -- See Note [Inline specialisations]
+ final_spec_f
+ | Just sat <- fn_has_inline_rule
+ = let
+ mb_spec_arity = if sat then Just spec_arity else Nothing
+ in
+ spec_f_w_arity `setIdUnfolding` mkInlineRule spec_rhs mb_spec_arity
+ | otherwise
+ = spec_f_w_arity
+
+ ; return (Just ((final_spec_f, spec_rhs), final_uds, spec_env_rule)) } }
where
- my_zipEqual doc xs ys
-#ifdef DEBUG
- | not (equalLength xs ys) = pprPanic "my_zipEqual" (vcat
- [ ppr xs, ppr ys
- , ppr fn <+> ppr call_ts
- , ppr (idType fn), ppr theta
- , ppr n_dicts, ppr rhs_dicts
- , ppr rhs])
-#endif
- | otherwise = zipEqual doc xs ys
+ my_zipEqual xs ys zs
+ | debugIsOn && not (equalLength xs ys && equalLength ys zs)
+ = pprPanic "my_zipEqual" (vcat [ ppr xs, ppr ys
+ , ppr fn <+> ppr call_ts
+ , ppr (idType fn), ppr theta
+ , ppr n_dicts, ppr rhs_dict_ids
+ , ppr rhs])
+ | otherwise = zip3 xs ys zs
+
+bindAuxiliaryDicts
+ :: Subst
+ -> [(DictId,DictId,CoreExpr)] -- (orig_dict, inst_dict, dx)
+ -> (Subst, -- Substitute for all orig_dicts
+ [CoreBind]) -- Auxiliary bindings
+-- Bind any dictionary arguments to fresh names, to preserve sharing
+-- Substitution already substitutes orig_dict -> inst_dict
+bindAuxiliaryDicts subst triples = go subst [] triples
+ where
+ go subst binds [] = (subst, binds)
+ go subst binds ((d, dx_id, dx) : pairs)
+ | exprIsTrivial dx = go (extendIdSubst subst d dx) binds pairs
+ -- No auxiliary binding necessary
+ -- Note that we bind the *original* dict in the substitution,
+ -- overriding any d->dx_id binding put there by substBndrs
+
+ | otherwise = go subst_w_unf (NonRec dx_id dx : binds) pairs
+ where
+ dx_id1 = dx_id `setIdUnfolding` mkUnfolding False False dx
+ subst_w_unf = extendIdSubst subst d (Var dx_id1)
+ -- Important! We're going to substitute dx_id1 for d
+ -- and we want it to look "interesting", else we won't gather *any*
+ -- consequential calls. E.g.
+ -- f d = ...g d....
+ -- If we specialise f for a call (f (dfun dNumInt)), we'll get
+ -- a consequent call (g d') with an auxiliary definition
+ -- d' = df dNumInt
+ -- We want that consequent call to look interesting
+ --
+ -- Again, note that we bind the *original* dict in the substitution,
+ -- overriding any d->dx_id binding put there by substBndrs
\end{code}
+Note [From non-recursive to recursive]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Even in the non-recursive case, if any dict-binds depend on 'fn' we might
+have built a recursive knot
+
+ f a d x = <blah>
+ MkUD { ud_binds = d7 = MkD ..f..
+ , ud_calls = ...(f T d7)... }
+
+The we generate
+
+ Rec { fs x = <blah>[T/a, d7/d]
+ f a d x = <blah>
+ RULE f T _ = fs
+ d7 = ...f... }
+
+Here the recursion is only through the RULE.
+
+
+Note [Specialisation of dictionary functions]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Here is a nasty example that bit us badly: see Trac #3591
+
+ dfun a d = MkD a d (meth d)
+ d4 = <blah>
+ d2 = dfun T d4
+ d1 = $p1 d2
+ d3 = dfun T d1
+
+None of these definitions is recursive. What happened was that we
+generated a specialisation:
+
+ RULE forall d. dfun T d = dT
+ dT = (MkD a d (meth d)) [T/a, d1/d]
+ = MkD T d1 (meth d1)
+
+But now we use the RULE on the RHS of d2, to get
+
+ d2 = dT = MkD d1 (meth d1)
+ d1 = $p1 d2
+
+and now d1 is bottom! The problem is that when specialising 'dfun' we
+should first dump "below" the binding all floated dictionary bindings
+that mention 'dfun' itself. So d2 and d3 (and hence d1) must be
+placed below 'dfun', and thus unavailable to it when specialising
+'dfun'. That in turn means that the call (dfun T d1) must be
+discarded. On the other hand, the call (dfun T d4) is fine, assuming
+d4 doesn't mention dfun.
+
+But look at this:
+
+ class C a where { foo,bar :: [a] -> [a] }
+
+ instance C Int where
+ foo x = r_bar x
+ bar xs = reverse xs
+
+ r_bar :: C a => [a] -> [a]
+ r_bar xs = bar (xs ++ xs)
+
+That translates to:
+
+ r_bar a (c::C a) (xs::[a]) = bar a d (xs ++ xs)
+
+ Rec { $fCInt :: C Int = MkC foo_help reverse
+ foo_help (xs::[Int]) = r_bar Int $fCInt xs }
+
+The call (r_bar $fCInt) mentions $fCInt,
+ which mentions foo_help,
+ which mentions r_bar
+But we DO want to specialise r_bar at Int:
+
+ Rec { $fCInt :: C Int = MkC foo_help reverse
+ foo_help (xs::[Int]) = r_bar Int $fCInt xs
+
+ r_bar a (c::C a) (xs::[a]) = bar a d (xs ++ xs)
+ RULE r_bar Int _ = r_bar_Int
+
+ r_bar_Int xs = bar Int $fCInt (xs ++ xs)
+ }
+
+Note that, because of its RULE, r_bar joins the recursive
+group. (In this case it'll unravel a short moment later.)
+
+
+Conclusion: we catch the nasty case using filter_dfuns in
+callsForMe To be honest I'm not 100% certain that this is 100%
+right, but it works. Sigh.
+
+
+Note [Specialising a recursive group]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider
+ let rec { f x = ...g x'...
+ ; g y = ...f y'.... }
+ in f 'a'
+Here we specialise 'f' at Char; but that is very likely to lead to
+a specialisation of 'g' at Char. We must do the latter, else the
+whole point of specialisation is lost.
+
+But we do not want to keep iterating to a fixpoint, because in the
+presence of polymorphic recursion we might generate an infinite number
+of specialisations.
+
+So we use the following heuristic:
+ * Arrange the rec block in dependency order, so far as possible
+ (the occurrence analyser already does this)
+
+ * Specialise it much like a sequence of lets
+
+ * Then go through the block a second time, feeding call-info from
+ the RHSs back in the bottom, as it were
+
+In effect, the ordering maxmimises the effectiveness of each sweep,
+and we do just two sweeps. This should catch almost every case of
+monomorphic recursion -- the exception could be a very knotted-up
+recursion with multiple cycles tied up together.
+
+This plan is implemented in the Rec case of specBindItself.
+
+Note [Specialisations already covered]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+We obviously don't want to generate two specialisations for the same
+argument pattern. There are two wrinkles
+
+1. We do the already-covered test in specDefn, not when we generate
+the CallInfo in mkCallUDs. We used to test in the latter place, but
+we now iterate the specialiser somewhat, and the Id at the call site
+might therefore not have all the RULES that we can see in specDefn
+
+2. What about two specialisations where the second is an *instance*
+of the first? If the more specific one shows up first, we'll generate
+specialisations for both. If the *less* specific one shows up first,
+we *don't* currently generate a specialisation for the more specific
+one. (See the call to lookupRule in already_covered.) Reasons:
+ (a) lookupRule doesn't say which matches are exact (bad reason)
+ (b) if the earlier specialisation is user-provided, it's
+ far from clear that we should auto-specialise further
+
+Note [Auto-specialisation and RULES]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider:
+ g :: Num a => a -> a
+ g = ...
+
+ f :: (Int -> Int) -> Int
+ f w = ...
+ {-# RULE f g = 0 #-}
+
+Suppose that auto-specialisation makes a specialised version of
+g::Int->Int That version won't appear in the LHS of the RULE for f.
+So if the specialisation rule fires too early, the rule for f may
+never fire.
+
+It might be possible to add new rules, to "complete" the rewrite system.
+Thus when adding
+ RULE forall d. g Int d = g_spec
+also add
+ RULE f g_spec = 0
+
+But that's a bit complicated. For now we ask the programmer's help,
+by *copying the INLINE activation pragma* to the auto-specialised
+rule. So if g says {-# NOINLINE[2] g #-}, then the auto-spec rule
+will also not be active until phase 2. And that's what programmers
+should jolly well do anyway, even aside from specialisation, to ensure
+that g doesn't inline too early.
+
+This in turn means that the RULE would never fire for a NOINLINE
+thing so not much point in generating a specialisation at all.
+
Note [Specialisation shape]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
We only specialise a function if it has visible top-level lambdas
Reason: when specialising the body for a call (f ty dexp), we want to
substitute dexp for d, and pick up specialised calls in the body of f.
-This doesn't always work. One example I came across was htis:
+This doesn't always work. One example I came across was this:
newtype Gen a = MkGen{ unGen :: Int -> a }
choose :: Eq a => a -> Gen a
where choose doesn't have any dict arguments. Thus far I have not
tried to fix this (wait till there's a real example).
-
Note [Inline specialisations]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We transfer to the specialised function any INLINE stuff from the
-original. This means (a) the Activation in the IdInfo, and (b) any
-InlineMe on the RHS.
+original. This means
+ (a) the Activation for its inlining (from its InlinePragma)
+ (b) any InlineRule
This is a change (Jun06). Previously the idea is that the point of
inlining was precisely to specialise the function at its call site,
boring to trigger inlining), and it's certainly better to call the
specialised version.
-A case in point is dictionary functions, which are current marked
-INLINE, but which are worth specialising.
-
-\begin{code}
-dropInline :: CoreExpr -> (Bool, CoreExpr)
-dropInline (Note InlineMe rhs) = (True, rhs)
-dropInline rhs = (False, rhs)
-\end{code}
%************************************************************************
%* *
\begin{code}
data UsageDetails
= MkUD {
- dict_binds :: !(Bag DictBind),
+ ud_binds :: !(Bag DictBind),
-- Floated dictionary bindings
-- The order is important;
-- in ds1 `union` ds2, bindings in ds2 can depend on those in ds1
-- (Remember, Bags preserve order in GHC.)
- calls :: !CallDetails
+ ud_calls :: !CallDetails
+
+ -- INVARIANT: suppose bs = bindersOf ud_binds
+ -- Then 'calls' may *mention* 'bs',
+ -- but there should be no calls *for* bs
}
+instance Outputable UsageDetails where
+ ppr (MkUD { ud_binds = dbs, ud_calls = calls })
+ = ptext (sLit "MkUD") <+> braces (sep (punctuate comma
+ [ptext (sLit "binds") <+> equals <+> ppr dbs,
+ ptext (sLit "calls") <+> equals <+> ppr calls]))
+
type DictBind = (CoreBind, VarSet)
-- The set is the free vars of the binding
-- both tyvars and dicts
type DictExpr = CoreExpr
-emptyUDs = MkUD { dict_binds = emptyBag, calls = emptyFM }
-
-type ProtoUsageDetails = ([DictBind],
- [(Id, CallKey, ([DictExpr], VarSet))]
- )
+emptyUDs :: UsageDetails
+emptyUDs = MkUD { ud_binds = emptyBag, ud_calls = emptyVarEnv }
------------------------------------------------------------
-type CallDetails = FiniteMap Id CallInfo
+type CallDetails = IdEnv CallInfoSet
newtype CallKey = CallKey [Maybe Type] -- Nothing => unconstrained type argument
-type CallInfo = FiniteMap CallKey
- ([DictExpr], VarSet) -- Dict args and the vars of the whole
- -- call (including tyvars)
- -- [*not* include the main id itself, of course]
- -- The finite maps eliminate duplicates
- -- The list of types and dictionaries is guaranteed to
- -- match the type of f
+
+-- CallInfo uses a Map, thereby ensuring that
+-- we record only one call instance for any key
+--
+-- The list of types and dictionaries is guaranteed to
+-- match the type of f
+type CallInfoSet = Map CallKey ([DictExpr], VarSet)
+ -- Range is dict args and the vars of the whole
+ -- call (including tyvars)
+ -- [*not* include the main id itself, of course]
+
+type CallInfo = (CallKey, ([DictExpr], VarSet))
+
+instance Outputable CallKey where
+ ppr (CallKey ts) = ppr ts
-- Type isn't an instance of Ord, so that we can control which
-- instance we use. That's tiresome here. Oh well
instance Eq CallKey where
- k1 == k2 = case k1 `compare` k2 of { EQ -> True; other -> False }
+ k1 == k2 = case k1 `compare` k2 of { EQ -> True; _ -> False }
instance Ord CallKey where
compare (CallKey k1) (CallKey k2) = cmpList cmp k1 k2
where
- cmp Nothing Nothing = EQ
- cmp Nothing (Just t2) = LT
- cmp (Just t1) Nothing = GT
+ cmp Nothing Nothing = EQ
+ cmp Nothing (Just _) = LT
+ cmp (Just _) Nothing = GT
cmp (Just t1) (Just t2) = tcCmpType t1 t2
unionCalls :: CallDetails -> CallDetails -> CallDetails
-unionCalls c1 c2 = plusFM_C plusFM c1 c2
+unionCalls c1 c2 = plusVarEnv_C Map.union c1 c2
+
+-- plusCalls :: UsageDetails -> CallDetails -> UsageDetails
+-- plusCalls uds call_ds = uds { ud_calls = ud_calls uds `unionCalls` call_ds }
-singleCall :: Id -> [Maybe Type] -> [DictExpr] -> CallDetails
+callDetailsFVs :: CallDetails -> VarSet
+callDetailsFVs calls = foldVarEnv (unionVarSet . callInfoFVs) emptyVarSet calls
+
+callInfoFVs :: CallInfoSet -> VarSet
+callInfoFVs call_info = Map.foldRightWithKey (\_ (_,fv) vs -> unionVarSet fv vs) emptyVarSet call_info
+
+------------------------------------------------------------
+singleCall :: Id -> [Maybe Type] -> [DictExpr] -> UsageDetails
singleCall id tys dicts
- = unitFM id (unitFM (CallKey tys) (dicts, call_fvs))
+ = MkUD {ud_binds = emptyBag,
+ ud_calls = unitVarEnv id (Map.singleton (CallKey tys) (dicts, call_fvs)) }
where
call_fvs = exprsFreeVars dicts `unionVarSet` tys_fvs
tys_fvs = tyVarsOfTypes (catMaybes tys)
--
-- We don't include the 'id' itself.
-listToCallDetails calls
- = foldr (unionCalls . mk_call) emptyFM calls
- where
- mk_call (id, tys, dicts_w_fvs) = unitFM id (unitFM tys dicts_w_fvs)
- -- NB: the free vars of the call are provided
-
-callDetailsToList calls = [ (id,tys,dicts)
- | (id,fm) <- fmToList calls,
- (tys, dicts) <- fmToList fm
- ]
-
-mkCallUDs subst f args
- | null theta
+mkCallUDs :: Id -> [CoreExpr] -> UsageDetails
+mkCallUDs f args
+ | not (isLocalId f) -- Imported from elsewhere
+ || null theta -- Not overloaded
|| not (all isClassPred theta)
-- Only specialise if all overloading is on class params.
-- In ptic, with implicit params, the type args
-- *don't* say what the value of the implicit param is!
|| not (spec_tys `lengthIs` n_tyvars)
|| not ( dicts `lengthIs` n_dicts)
- || maybeToBool (lookupRule (\act -> True) (substInScope subst) emptyRuleBase f args)
- -- There's already a rule covering this call. A typical case
- -- is where there's an explicit user-provided rule. Then
- -- we don't want to create a specialised version
- -- of the function that overlaps.
- = emptyUDs -- Not overloaded, or no specialisation wanted
+ || not (any interestingDict dicts) -- Note [Interesting dictionary arguments]
+ -- See also Note [Specialisations already covered]
+ = -- pprTrace "mkCallUDs: discarding" (vcat [ppr f, ppr args, ppr n_tyvars, ppr n_dicts, ppr (map interestingDict dicts)])
+ emptyUDs -- Not overloaded, or no specialisation wanted
| otherwise
- = MkUD {dict_binds = emptyBag,
- calls = singleCall f spec_tys dicts
- }
+ = -- pprTrace "mkCallUDs: keeping" (vcat [ppr f, ppr args, ppr n_tyvars, ppr n_dicts, ppr (map interestingDict dicts)])
+ singleCall f spec_tys dicts
where
(tyvars, theta, _) = tcSplitSigmaTy (idType f)
constrained_tyvars = tyVarsOfTheta theta
mk_spec_ty tyvar ty
| tyvar `elemVarSet` constrained_tyvars = Just ty
| otherwise = Nothing
+\end{code}
-------------------------------------------------------------
+Note [Interesting dictionary arguments]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider this
+ \a.\d:Eq a. let f = ... in ...(f d)...
+There really is not much point in specialising f wrt the dictionary d,
+because the code for the specialised f is not improved at all, because
+d is lambda-bound. We simply get junk specialisations.
+
+What is "interesting"? Just that it has *some* structure.
+
+\begin{code}
+interestingDict :: CoreExpr -> Bool
+-- A dictionary argument is interesting if it has *some* structure
+interestingDict (Var v) = hasSomeUnfolding (idUnfolding v)
+ || isDataConWorkId v
+interestingDict (Type _) = False
+interestingDict (App fn (Type _)) = interestingDict fn
+interestingDict (Note _ a) = interestingDict a
+interestingDict (Cast e _) = interestingDict e
+interestingDict _ = True
+\end{code}
+
+\begin{code}
plusUDs :: UsageDetails -> UsageDetails -> UsageDetails
-plusUDs (MkUD {dict_binds = db1, calls = calls1})
- (MkUD {dict_binds = db2, calls = calls2})
- = MkUD {dict_binds = d, calls = c}
- where
- d = db1 `unionBags` db2
- c = calls1 `unionCalls` calls2
+plusUDs (MkUD {ud_binds = db1, ud_calls = calls1})
+ (MkUD {ud_binds = db2, ud_calls = calls2})
+ = MkUD { ud_binds = db1 `unionBags` db2
+ , ud_calls = calls1 `unionCalls` calls2 }
+plusUDList :: [UsageDetails] -> UsageDetails
plusUDList = foldr plusUDs emptyUDs
--- zapCalls deletes calls to ids from uds
-zapCalls ids uds = uds {calls = delListFromFM (calls uds) ids}
+-----------------------------
+_dictBindBndrs :: Bag DictBind -> [Id]
+_dictBindBndrs dbs = foldrBag ((++) . bindersOf . fst) [] dbs
+mkDB :: CoreBind -> DictBind
mkDB bind = (bind, bind_fvs bind)
+bind_fvs :: CoreBind -> VarSet
bind_fvs (NonRec bndr rhs) = pair_fvs (bndr,rhs)
bind_fvs (Rec prs) = foldl delVarSet rhs_fvs bndrs
where
bndrs = map fst prs
rhs_fvs = unionVarSets (map pair_fvs prs)
+pair_fvs :: (Id, CoreExpr) -> VarSet
pair_fvs (bndr, rhs) = exprFreeVars rhs `unionVarSet` idFreeVars bndr
-- Don't forget variables mentioned in the
-- rules of the bndr. C.f. OccAnal.addRuleUsage
-- type T a = Int
-- x :: T a = 3
-addDictBind (dict,rhs) uds = uds { dict_binds = mkDB (NonRec dict rhs) `consBag` dict_binds uds }
+flattenDictBinds :: Bag DictBind -> [(Id,CoreExpr)] -> [(Id,CoreExpr)]
+flattenDictBinds dbs pairs
+ = foldrBag add pairs dbs
+ where
+ add (NonRec b r,_) pairs = (b,r) : pairs
+ add (Rec prs1, _) pairs = prs1 ++ pairs
+
+snocDictBinds :: UsageDetails -> [CoreBind] -> UsageDetails
+-- Add ud_binds to the tail end of the bindings in uds
+snocDictBinds uds dbs
+ = uds { ud_binds = ud_binds uds `unionBags`
+ foldr (consBag . mkDB) emptyBag dbs }
+
+consDictBind :: CoreBind -> UsageDetails -> UsageDetails
+consDictBind bind uds = uds { ud_binds = mkDB bind `consBag` ud_binds uds }
-dumpAllDictBinds (MkUD {dict_binds = dbs}) binds
+addDictBinds :: [DictBind] -> UsageDetails -> UsageDetails
+addDictBinds binds uds = uds { ud_binds = listToBag binds `unionBags` ud_binds uds }
+
+snocDictBind :: UsageDetails -> CoreBind -> UsageDetails
+snocDictBind uds bind = uds { ud_binds = ud_binds uds `snocBag` mkDB bind }
+
+wrapDictBinds :: Bag DictBind -> [CoreBind] -> [CoreBind]
+wrapDictBinds dbs binds
= foldrBag add binds dbs
where
add (bind,_) binds = bind : binds
-dumpUDs :: [CoreBndr]
- -> UsageDetails -> CoreExpr
- -> (UsageDetails, CoreExpr)
-dumpUDs bndrs uds body
- = (free_uds, foldr add_let body dict_binds)
+wrapDictBindsE :: Bag DictBind -> CoreExpr -> CoreExpr
+wrapDictBindsE dbs expr
+ = foldrBag add expr dbs
where
- (free_uds, (dict_binds, _)) = splitUDs bndrs uds
- add_let (bind,_) body = Let bind body
-
-splitUDs :: [CoreBndr]
- -> UsageDetails
- -> (UsageDetails, -- These don't mention the binders
- ProtoUsageDetails) -- These do
-
-splitUDs bndrs uds@(MkUD {dict_binds = orig_dbs,
- calls = orig_calls})
-
- = if isEmptyBag dump_dbs && null dump_calls then
- -- Common case: binder doesn't affect floats
- (uds, ([],[]))
-
- else
- -- Binders bind some of the fvs of the floats
- (MkUD {dict_binds = free_dbs,
- calls = listToCallDetails free_calls},
- (bagToList dump_dbs, dump_calls)
- )
-
+ add (bind,_) expr = Let bind expr
+
+----------------------
+dumpUDs :: [CoreBndr] -> UsageDetails -> (UsageDetails, Bag DictBind)
+-- Used at a lambda or case binder; just dump anything mentioning the binder
+dumpUDs bndrs uds@(MkUD { ud_binds = orig_dbs, ud_calls = orig_calls })
+ | null bndrs = (uds, emptyBag) -- Common in case alternatives
+ | otherwise = -- pprTrace "dumpUDs" (ppr bndrs $$ ppr free_uds $$ ppr dump_dbs) $
+ (free_uds, dump_dbs)
where
+ free_uds = MkUD { ud_binds = free_dbs, ud_calls = free_calls }
bndr_set = mkVarSet bndrs
+ (free_dbs, dump_dbs, dump_set) = splitDictBinds orig_dbs bndr_set
+ free_calls = deleteCallsMentioning dump_set $ -- Drop calls mentioning bndr_set on the floor
+ deleteCallsFor bndrs orig_calls -- Discard calls for bndr_set; there should be
+ -- no calls for any of the dicts in dump_dbs
+
+dumpBindUDs :: [CoreBndr] -> UsageDetails -> (UsageDetails, Bag DictBind, Bool)
+-- Used at a lambda or case binder; just dump anything mentioning the binder
+dumpBindUDs bndrs (MkUD { ud_binds = orig_dbs, ud_calls = orig_calls })
+ = -- pprTrace "dumpBindUDs" (ppr bndrs $$ ppr free_uds $$ ppr dump_dbs) $
+ (free_uds, dump_dbs, float_all)
+ where
+ free_uds = MkUD { ud_binds = free_dbs, ud_calls = free_calls }
+ bndr_set = mkVarSet bndrs
+ (free_dbs, dump_dbs, dump_set) = splitDictBinds orig_dbs bndr_set
+ free_calls = deleteCallsFor bndrs orig_calls
+ float_all = dump_set `intersectsVarSet` callDetailsFVs free_calls
+
+callsForMe :: Id -> UsageDetails -> (UsageDetails, [CallInfo])
+callsForMe fn (MkUD { ud_binds = orig_dbs, ud_calls = orig_calls })
+ = -- pprTrace ("callsForMe")
+ -- (vcat [ppr fn,
+ -- text "Orig dbs =" <+> ppr (_dictBindBndrs orig_dbs),
+ -- text "Orig calls =" <+> ppr orig_calls,
+ -- text "Dep set =" <+> ppr dep_set,
+ -- text "Calls for me =" <+> ppr calls_for_me]) $
+ (uds_without_me, calls_for_me)
+ where
+ uds_without_me = MkUD { ud_binds = orig_dbs, ud_calls = delVarEnv orig_calls fn }
+ calls_for_me = case lookupVarEnv orig_calls fn of
+ Nothing -> []
+ Just cs -> filter_dfuns (Map.toList cs)
- (free_dbs, dump_dbs, dump_idset)
- = foldlBag dump_db (emptyBag, emptyBag, bndr_set) orig_dbs
- -- Important that it's foldl not foldr;
- -- we're accumulating the set of dumped ids in dump_set
+ dep_set = foldlBag go (unitVarSet fn) orig_dbs
+ go dep_set (db,fvs) | fvs `intersectsVarSet` dep_set
+ = extendVarSetList dep_set (bindersOf db)
+ | otherwise = dep_set
+
+ -- Note [Specialisation of dictionary functions]
+ filter_dfuns | isDFunId fn = filter ok_call
+ | otherwise = \cs -> cs
- -- Filter out any calls that mention things that are being dumped
- orig_call_list = callDetailsToList orig_calls
- (dump_calls, free_calls) = partition captured orig_call_list
- captured (id,tys,(dicts, fvs)) = fvs `intersectsVarSet` dump_idset
- || id `elemVarSet` dump_idset
+ ok_call (_, (_,fvs)) = not (fvs `intersectsVarSet` dep_set)
- dump_db (free_dbs, dump_dbs, dump_idset) db@(bind, fvs)
+----------------------
+splitDictBinds :: Bag DictBind -> IdSet -> (Bag DictBind, Bag DictBind, IdSet)
+-- Returns (free_dbs, dump_dbs, dump_set)
+splitDictBinds dbs bndr_set
+ = foldlBag split_db (emptyBag, emptyBag, bndr_set) dbs
+ -- Important that it's foldl not foldr;
+ -- we're accumulating the set of dumped ids in dump_set
+ where
+ split_db (free_dbs, dump_dbs, dump_idset) db@(bind, fvs)
| dump_idset `intersectsVarSet` fvs -- Dump it
= (free_dbs, dump_dbs `snocBag` db,
extendVarSetList dump_idset (bindersOf bind))
| otherwise -- Don't dump it
= (free_dbs `snocBag` db, dump_dbs, dump_idset)
+
+
+----------------------
+deleteCallsMentioning :: VarSet -> CallDetails -> CallDetails
+-- Remove calls *mentioning* bs
+deleteCallsMentioning bs calls
+ = mapVarEnv filter_calls calls
+ where
+ filter_calls :: CallInfoSet -> CallInfoSet
+ filter_calls = Map.filterWithKey (\_ (_, fvs) -> not (fvs `intersectsVarSet` bs))
+
+deleteCallsFor :: [Id] -> CallDetails -> CallDetails
+-- Remove calls *for* bs
+deleteCallsFor bs calls = delVarEnvList calls bs
\end{code}
\begin{code}
type SpecM a = UniqSM a
-thenSM = thenUs
-returnSM = returnUs
-getUniqSM = getUniqueUs
-mapSM = mapUs
+initSM :: UniqSupply -> SpecM a -> a
initSM = initUs_
-mapAndCombineSM f [] = returnSM ([], emptyUDs)
-mapAndCombineSM f (x:xs) = f x `thenSM` \ (y, uds1) ->
- mapAndCombineSM f xs `thenSM` \ (ys, uds2) ->
- returnSM (y:ys, uds1 `plusUDs` uds2)
+mapAndCombineSM :: (a -> SpecM (b, UsageDetails)) -> [a] -> SpecM ([b], UsageDetails)
+mapAndCombineSM _ [] = return ([], emptyUDs)
+mapAndCombineSM f (x:xs) = do (y, uds1) <- f x
+ (ys, uds2) <- mapAndCombineSM f xs
+ return (y:ys, uds1 `plusUDs` uds2)
cloneBindSM :: Subst -> CoreBind -> SpecM (Subst, Subst, CoreBind)
-- Clone the binders of the bind; return new bind with the cloned binders
-- Return the substitution to use for RHSs, and the one to use for the body
-cloneBindSM subst (NonRec bndr rhs)
- = getUs `thenUs` \ us ->
- let
- (subst', bndr') = cloneIdBndr subst us bndr
- in
- returnUs (subst, subst', NonRec bndr' rhs)
-
-cloneBindSM subst (Rec pairs)
- = getUs `thenUs` \ us ->
- let
- (subst', bndrs') = cloneRecIdBndrs subst us (map fst pairs)
- in
- returnUs (subst', subst', Rec (bndrs' `zip` map snd pairs))
-
-cloneBinders subst bndrs
- = getUs `thenUs` \ us ->
- returnUs (cloneIdBndrs subst us bndrs)
-
-newIdSM old_id new_ty
- = getUniqSM `thenSM` \ uniq ->
- let
- -- Give the new Id a similar occurrence name to the old one
- name = idName old_id
- new_id = mkUserLocal (mkSpecOcc (nameOccName name)) uniq new_ty (getSrcSpan name)
- in
- returnSM new_id
+cloneBindSM subst (NonRec bndr rhs) = do
+ us <- getUniqueSupplyM
+ let (subst', bndr') = cloneIdBndr subst us bndr
+ return (subst, subst', NonRec bndr' rhs)
+
+cloneBindSM subst (Rec pairs) = do
+ us <- getUniqueSupplyM
+ let (subst', bndrs') = cloneRecIdBndrs subst us (map fst pairs)
+ return (subst', subst', Rec (bndrs' `zip` map snd pairs))
+
+newDictBndrs :: Subst -> [CoreBndr] -> SpecM (Subst, [CoreBndr])
+-- Make up completely fresh binders for the dictionaries
+-- Their bindings are going to float outwards
+newDictBndrs subst bndrs
+ = do { bndrs' <- mapM new bndrs
+ ; let subst' = extendIdSubstList subst
+ [(d, Var d') | (d,d') <- bndrs `zip` bndrs']
+ ; return (subst', bndrs' ) }
+ where
+ new b = do { uniq <- getUniqueM
+ ; let n = idName b
+ ty' = CoreSubst.substTy subst (idType b)
+ ; return (mkUserLocal (nameOccName n) uniq ty' (getSrcSpan n)) }
+
+newSpecIdSM :: Id -> Type -> SpecM Id
+ -- Give the new Id a similar occurrence name to the old one
+newSpecIdSM old_id new_ty
+ = do { uniq <- getUniqueM
+ ; let name = idName old_id
+ new_occ = mkSpecOcc (nameOccName name)
+ new_id = mkUserLocal new_occ uniq new_ty (getSrcSpan name)
+ ; return new_id }
\end{code}
projects / ghc-hetmet.git / blobdiff