#include "HsVersions.h"
-import CmdLineOpts ( CoreToDo(..), SimplifierSwitch(..),
+import DynFlags ( CoreToDo(..), SimplifierSwitch(..),
SimplifierMode(..), DynFlags, DynFlag(..), dopt,
- dopt_CoreToDo, buildCoreToDo
- )
+ getCoreToDo )
import CoreSyn
-import TcIface ( loadImportedRules )
import HscTypes ( HscEnv(..), ModGuts(..), ExternalPackageState(..),
- ModDetails(..), HomeModInfo(..), HomePackageTable, Dependencies( dep_mods ),
+ Dependencies( dep_mods ),
hscEPS, hptRules )
import CSE ( cseProgram )
-import Rules ( RuleBase, ruleBaseIds, emptyRuleBase,
- extendRuleBaseList, pprRuleBase, ruleCheckProgram )
-import Module ( elemModuleEnv, lookupModuleEnv )
-import PprCore ( pprCoreBindings, pprCoreExpr, pprIdRules )
-import OccurAnal ( occurAnalyseBinds, occurAnalyseGlobalExpr )
+import Rules ( RuleBase, emptyRuleBase, mkRuleBase, unionRuleBase,
+ extendRuleBaseList, pprRuleBase, ruleCheckProgram,
+ addSpecInfo, addIdSpecialisations )
+import PprCore ( pprCoreBindings, pprCoreExpr, pprRules )
+import OccurAnal ( occurAnalysePgm, occurAnalyseExpr )
+import IdInfo ( setNewStrictnessInfo, newStrictnessInfo,
+ setWorkerInfo, workerInfo,
+ setSpecInfo, specInfo, specInfoRules )
import CoreUtils ( coreBindsSize )
import Simplify ( simplTopBinds, simplExpr )
import SimplEnv ( SimplEnv, simplBinders, mkSimplEnv, setInScopeSet )
import SimplMonad
import ErrUtils ( dumpIfSet, dumpIfSet_dyn, showPass )
import CoreLint ( endPass )
-import VarEnv ( mkInScopeSet )
import FloatIn ( floatInwards )
import FloatOut ( floatOutwards )
-import Id ( idIsFrom, idSpecialisation, setIdSpecialisation )
+import Id ( Id, modifyIdInfo, idInfo, isExportedId, isLocalId,
+ idSpecialisation, idName )
import VarSet
+import VarEnv
+import NameEnv ( lookupNameEnv )
import LiberateCase ( liberateCase )
import SAT ( doStaticArgs )
import Specialise ( specProgram)
import IO ( hPutStr, stderr )
import Outputable
import List ( partition )
-import Maybes ( orElse, fromJust )
+import Maybes ( orElse )
\end{code}
%************************************************************************
core2core hsc_env guts
= do
let dflags = hsc_dflags hsc_env
- core_todos
- | Just todo <- dopt_CoreToDo dflags = todo
- | otherwise = buildCoreToDo dflags
+ core_todos = getCoreToDo dflags
us <- mkSplitUniqSupply 's'
let (cp_us, ru_us) = splitUniqSupply us
(imp_rule_base, guts') <- prepareRules hsc_env guts ru_us
-- DO THE BUSINESS
- (stats, guts'') <- doCorePasses hsc_env cp_us
+ (stats, guts'') <- doCorePasses hsc_env imp_rule_base cp_us
(zeroSimplCount dflags)
- imp_rule_base guts' core_todos
+ guts' core_todos
dumpIfSet_dyn dflags Opt_D_dump_simpl_stats
"Grand total simplifier statistics"
emptyRuleBase
doCorePasses :: HscEnv
+ -> RuleBase -- the imported main rule base
-> UniqSupply -- uniques
-> SimplCount -- simplifier stats
- -> RuleBase -- the main rule base
-> ModGuts -- local binds in (with rules attached)
-> [CoreToDo] -- which passes to do
-> IO (SimplCount, ModGuts)
-doCorePasses hsc_env us stats rb guts []
+doCorePasses hsc_env rb us stats guts []
= return (stats, guts)
-doCorePasses hsc_env us stats rb guts (to_do : to_dos)
+doCorePasses hsc_env rb us stats guts (to_do : to_dos)
= do
let (us1, us2) = splitUniqSupply us
- (stats1, rb1, guts1) <- doCorePass to_do hsc_env us1 rb guts
- doCorePasses hsc_env us2 (stats `plusSimplCount` stats1) rb1 guts1 to_dos
+ (stats1, guts1) <- doCorePass to_do hsc_env us1 rb guts
+ doCorePasses hsc_env rb us2 (stats `plusSimplCount` stats1) guts1 to_dos
doCorePass (CoreDoSimplify mode sws) = _scc_ "Simplify" simplifyPgm mode sws
doCorePass CoreCSE = _scc_ "CommonSubExpr" trBinds cseProgram
-- Most passes return no stats and don't change rules
trBinds :: (DynFlags -> [CoreBind] -> IO [CoreBind])
-> HscEnv -> UniqSupply -> RuleBase -> ModGuts
- -> IO (SimplCount, RuleBase, ModGuts)
+ -> IO (SimplCount, ModGuts)
trBinds do_pass hsc_env us rb guts
= do { binds' <- do_pass dflags (mg_binds guts)
- ; return (zeroSimplCount dflags, rb, guts { mg_binds = binds' }) }
+ ; return (zeroSimplCount dflags, guts { mg_binds = binds' }) }
where
dflags = hsc_dflags hsc_env
trBindsU :: (DynFlags -> UniqSupply -> [CoreBind] -> IO [CoreBind])
-> HscEnv -> UniqSupply -> RuleBase -> ModGuts
- -> IO (SimplCount, RuleBase, ModGuts)
+ -> IO (SimplCount, ModGuts)
trBindsU do_pass hsc_env us rb guts
= do { binds' <- do_pass dflags us (mg_binds guts)
- ; return (zeroSimplCount dflags, rb, guts { mg_binds = binds' }) }
+ ; return (zeroSimplCount dflags, guts { mg_binds = binds' }) }
where
dflags = hsc_dflags hsc_env
-- Observer passes just peek; don't modify the bindings at all
observe :: (DynFlags -> [CoreBind] -> IO a)
-> HscEnv -> UniqSupply -> RuleBase -> ModGuts
- -> IO (SimplCount, RuleBase, ModGuts)
+ -> IO (SimplCount, ModGuts)
observe do_pass hsc_env us rb guts
= do { binds <- do_pass dflags (mg_binds guts)
- ; return (zeroSimplCount dflags, rb, guts) }
+ ; return (zeroSimplCount dflags, guts) }
where
dflags = hsc_dflags hsc_env
\end{code}
-> UniqSupply
-> IO (RuleBase, -- Rule base for imported things, incl
-- (a) rules defined in this module (orphans)
- -- (b) rules from other packages
- -- (c) rules from other modules in home package
+ -- (b) rules from other modules in home package
+ -- but not things from other packages
+
ModGuts) -- Modified fields are
-- (a) Bindings have rules attached,
-- (b) Rules are now just orphan rules
prepareRules hsc_env@(HscEnv { hsc_dflags = dflags, hsc_HPT = hpt })
guts@(ModGuts { mg_binds = binds, mg_deps = deps, mg_rules = local_rules })
us
- = do { eps <- hscEPS hsc_env
-
- ; let -- Simplify the local rules; boringly, we need to make an in-scope set
+ = do { let -- Simplify the local rules; boringly, we need to make an in-scope set
-- from the local binders, to avoid warnings from Simplify.simplVar
local_ids = mkInScopeSet (mkVarSet (bindersOfBinds binds))
env = setInScopeSet gentleSimplEnv local_ids
(better_rules,_) = initSmpl dflags us (mapSmpl (simplRule env) local_rules)
home_pkg_rules = hptRules hsc_env (dep_mods deps)
- (orphan_rules, rules_for_locals) = partition isOrphanRule better_rules
- -- Get the rules for locally-defined Ids out of the RuleBase
- -- If we miss any rules for Ids defined here, then we end up
- -- giving the local decl a new Unique (because the in-scope-set is (hackily) the
- -- same as the non-local-rule-id set, so the Id looks as if it's in scope
- -- and hence should be cloned), and now the binding for the class method
- -- doesn't have the same Unique as the one in the Class and the tc-env
- -- Example: class Foo a where
- -- op :: a -> a
- -- {-# RULES "op" op x = x #-}
-
- -- NB: we assume that the imported rules dont include
- -- rules for Ids in this module; if there is, the above bad things may happen
-
- pkg_rule_base = eps_rule_base eps
- hpt_rule_base = extendRuleBaseList pkg_rule_base home_pkg_rules
- imp_rule_base = extendRuleBaseList hpt_rule_base orphan_rules
-
- -- Update the binders in the local bindings with the lcoal rules
- -- Update the binders of top-level bindings by
- -- attaching the rules for each locally-defined Id to that Id.
+ -- Find the rules for locally-defined Ids; then we can attach them
+ -- to the binders in the top-level bindings
--
-- Reason
-- - It makes the rules easier to look up
-- which is extended on each iteration by the new wave of
-- local binders; any rules which aren't on the binding will
-- thereby get dropped
+ (rules_for_locals, rules_for_imps) = partition isLocalRule better_rules
local_rule_base = extendRuleBaseList emptyRuleBase rules_for_locals
binds_w_rules = updateBinders local_rule_base binds
+ hpt_rule_base = mkRuleBase home_pkg_rules
+ imp_rule_base = extendRuleBaseList hpt_rule_base rules_for_imps
+
; dumpIfSet_dyn dflags Opt_D_dump_rules "Transformation rules"
- (vcat [text "Local rules", pprIdRules better_rules,
+ (vcat [text "Local rules", pprRules better_rules,
text "",
text "Imported rules", pprRuleBase imp_rule_base])
-#ifdef DEBUG
- ; let bad_rules = filter (idIsFrom (mg_module guts))
- (varSetElems (ruleBaseIds imp_rule_base))
- ; WARN( not (null bad_rules), ppr bad_rules ) return ()
-#endif
- ; return (imp_rule_base, guts { mg_binds = binds_w_rules, mg_rules = orphan_rules })
+ ; return (imp_rule_base, guts { mg_binds = binds_w_rules,
+ mg_rules = rules_for_imps })
}
updateBinders :: RuleBase -> [CoreBind] -> [CoreBind]
-updateBinders rule_base binds
+updateBinders local_rules binds
= map update_bndrs binds
where
- rule_ids = ruleBaseIds rule_base
-
update_bndrs (NonRec b r) = NonRec (update_bndr b) r
update_bndrs (Rec prs) = Rec [(update_bndr b, r) | (b,r) <- prs]
- update_bndr bndr = case lookupVarSet rule_ids bndr of
- Nothing -> bndr
- Just id -> bndr `setIdSpecialisation` idSpecialisation id
+ update_bndr bndr = case lookupNameEnv local_rules (idName bndr) of
+ Nothing -> bndr
+ Just rules -> bndr `addIdSpecialisations` rules
+ -- The binder might have some existing rules,
+ -- arising from specialisation pragmas
\end{code}
This doesn't match unless you do eta reduction on the build argument.
\begin{code}
-simplRule env rule@(IdCoreRule id _ (BuiltinRule _ _))
+simplRule env rule@(BuiltinRule {})
= returnSmpl rule
-simplRule env (IdCoreRule id is_orph (Rule act name bndrs args rhs))
+simplRule env rule@(Rule { ru_bndrs = bndrs, ru_args = args, ru_rhs = rhs })
= simplBinders env bndrs `thenSmpl` \ (env, bndrs') ->
mapSmpl (simplExprGently env) args `thenSmpl` \ args' ->
simplExprGently env rhs `thenSmpl` \ rhs' ->
- returnSmpl (IdCoreRule id is_orph (Rule act name bndrs' args' rhs'))
+ returnSmpl (rule { ru_bndrs = bndrs', ru_args = args', ru_rhs = rhs' })
-- It's important that simplExprGently does eta reduction.
-- For example, in a rule like:
-- enforce that; it just simplifies the expression twice
simplExprGently env expr
- = simplExpr env (occurAnalyseGlobalExpr expr) `thenSmpl` \ expr1 ->
- simplExpr env (occurAnalyseGlobalExpr expr1)
+ = simplExpr env (occurAnalyseExpr expr) `thenSmpl` \ expr1 ->
+ simplExpr env (occurAnalyseExpr expr1)
\end{code}
-> UniqSupply
-> RuleBase
-> ModGuts
- -> IO (SimplCount, RuleBase, ModGuts) -- New bindings
+ -> IO (SimplCount, ModGuts) -- New bindings
-simplifyPgm mode switches hsc_env us rule_base guts
+simplifyPgm mode switches hsc_env us imp_rule_base guts
= do {
showPass dflags "Simplify";
- (termination_msg, it_count, counts_out, rule_base', guts')
- <- do_iteration us rule_base 1 (zeroSimplCount dflags) guts;
+ (termination_msg, it_count, counts_out, binds')
+ <- do_iteration us 1 (zeroSimplCount dflags) (mg_binds guts) ;
dumpIfSet (dopt Opt_D_verbose_core2core dflags
&& dopt Opt_D_dump_simpl_stats dflags)
text "",
pprSimplCount counts_out]);
- endPass dflags "Simplify" Opt_D_verbose_core2core (mg_binds guts');
+ endPass dflags "Simplify" Opt_D_verbose_core2core binds';
- return (counts_out, rule_base', guts')
+ return (counts_out, guts { mg_binds = binds' })
}
where
- dflags = hsc_dflags hsc_env
- phase_info = case mode of
- SimplGently -> "gentle"
- SimplPhase n -> show n
-
- sw_chkr = isAmongSimpl switches
- max_iterations = intSwitchSet sw_chkr MaxSimplifierIterations `orElse` 2
+ dflags = hsc_dflags hsc_env
+ phase_info = case mode of
+ SimplGently -> "gentle"
+ SimplPhase n -> show n
+
+ sw_chkr = isAmongSimpl switches
+ max_iterations = intSwitchSet sw_chkr MaxSimplifierIterations `orElse` 2
- do_iteration us rule_base iteration_no counts guts
+ do_iteration us iteration_no counts binds
-- iteration_no is the number of the iteration we are
-- about to begin, with '1' for the first
| iteration_no > max_iterations -- Stop if we've run out of iterations
#endif
-- Subtract 1 from iteration_no to get the
-- number of iterations we actually completed
- return ("Simplifier baled out", iteration_no - 1, counts, rule_base, guts)
+ return ("Simplifier baled out", iteration_no - 1, counts, binds)
}
-- Try and force thunks off the binds; significantly reduces
-- space usage, especially with -O. JRS, 000620.
- | let sz = coreBindsSize (mg_binds guts) in sz == sz
+ | let sz = coreBindsSize binds in sz == sz
= do {
-- Occurrence analysis
- let { tagged_binds = _scc_ "OccAnal" occurAnalyseBinds (mg_binds guts) } ;
-
+ let { tagged_binds = _scc_ "OccAnal" occurAnalysePgm binds } ;
dumpIfSet_dyn dflags Opt_D_dump_occur_anal "Occurrence analysis"
(pprCoreBindings tagged_binds);
-- Get any new rules, and extend the rule base
- -- (on the side this extends the package rule base in the
- -- ExternalPackageTable, ready for the next complation
- -- in --make mode)
-- We need to do this regularly, because simplification can
-- poke on IdInfo thunks, which in turn brings in new rules
-- behind the scenes. Otherwise there's a danger we'll simply
-- miss the rules for Ids hidden inside imported inlinings
- new_rules <- loadImportedRules hsc_env guts ;
- let { rule_base' = extendRuleBaseList rule_base new_rules
+ eps <- hscEPS hsc_env ;
+ let { rule_base' = unionRuleBase imp_rule_base (eps_rule_base eps)
; simpl_env = mkSimplEnv mode sw_chkr rule_base' } ;
- -- The new rule base Ids are used to initialise
- -- the in-scope set. That way, the simplifier will change any
- -- occurrences of the imported id to the one in the imported_rule_ids
- -- set, which are decorated with their rules.
-- Simplify the program
-- We do this with a *case* not a *let* because lazy pattern
case initSmpl dflags us1 (_scc_ "SimplTopBinds" simplTopBinds simpl_env tagged_binds) of {
(binds', counts') -> do {
- let { guts' = guts { mg_binds = binds' }
- ; all_counts = counts `plusSimplCount` counts'
+ let { all_counts = counts `plusSimplCount` counts'
; herald = "Simplifier phase " ++ phase_info ++
", iteration " ++ show iteration_no ++
" out of " ++ show max_iterations
-- Stop if nothing happened; don't dump output
if isZeroSimplCount counts' then
return ("Simplifier reached fixed point", iteration_no,
- all_counts, rule_base', guts')
+ all_counts, binds')
else do {
+ -- Short out indirections
+ -- We do this *after* at least one run of the simplifier
+ -- because indirection-shorting uses the export flag on *occurrences*
+ -- and that isn't guaranteed to be ok until after the first run propagates
+ -- stuff from the binding site to its occurrences
+ let { binds'' = _scc_ "ZapInd" shortOutIndirections binds' } ;
-- Dump the result of this iteration
dumpIfSet_dyn dflags Opt_D_dump_simpl_iterations herald
(pprSimplCount counts') ;
-
- endPass dflags herald Opt_D_dump_simpl_iterations binds' ;
+ endPass dflags herald Opt_D_dump_simpl_iterations binds'' ;
-- Loop
- do_iteration us2 rule_base' (iteration_no + 1) all_counts guts'
+ do_iteration us2 (iteration_no + 1) all_counts binds''
} } } }
where
(us1, us2) = splitUniqSupply us
\end{code}
+
+
+%************************************************************************
+%* *
+ Shorting out indirections
+%* *
+%************************************************************************
+
+If we have this:
+
+ x_local = <expression>
+ ...bindings...
+ x_exported = x_local
+
+where x_exported is exported, and x_local is not, then we replace it with this:
+
+ x_exported = <expression>
+ x_local = x_exported
+ ...bindings...
+
+Without this we never get rid of the x_exported = x_local thing. This
+save a gratuitous jump (from \tr{x_exported} to \tr{x_local}), and
+makes strictness information propagate better. This used to happen in
+the final phase, but it's tidier to do it here.
+
+STRICTNESS: if we have done strictness analysis, we want the strictness info on
+x_local to transfer to x_exported. Hence the copyIdInfo call.
+
+RULES: we want to *add* any RULES for x_local to x_exported.
+
+Note [Rules and indirection-zapping]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Problem: what if x_exported has a RULE that mentions something in ...bindings...?
+Then the things mentioned can be out of scope! Solution
+ a) Make sure that in this pass the usage-info from x_exported is
+ available for ...bindings...
+ b) If there are any such RULES, rec-ify the entire top-level.
+ It'll get sorted out next time round
+
+Messing up the rules
+~~~~~~~~~~~~~~~~~~~~
+The example that went bad on me at one stage was this one:
+
+ iterate :: (a -> a) -> a -> [a]
+ [Exported]
+ iterate = iterateList
+
+ iterateFB c f x = x `c` iterateFB c f (f x)
+ iterateList f x = x : iterateList f (f x)
+ [Not exported]
+
+ {-# RULES
+ "iterate" forall f x. iterate f x = build (\c _n -> iterateFB c f x)
+ "iterateFB" iterateFB (:) = iterateList
+ #-}
+
+This got shorted out to:
+
+ iterateList :: (a -> a) -> a -> [a]
+ iterateList = iterate
+
+ iterateFB c f x = x `c` iterateFB c f (f x)
+ iterate f x = x : iterate f (f x)
+
+ {-# RULES
+ "iterate" forall f x. iterate f x = build (\c _n -> iterateFB c f x)
+ "iterateFB" iterateFB (:) = iterate
+ #-}
+
+And now we get an infinite loop in the rule system
+ iterate f x -> build (\cn -> iterateFB c f x)
+ -> iterateFB (:) f x
+ -> iterate f x
+
+Tiresome old solution:
+ don't do shorting out if f has rewrite rules (see shortableIdInfo)
+
+New solution (I think):
+ use rule switching-off pragmas to get rid
+ of iterateList in the first place
+
+
+Other remarks
+~~~~~~~~~~~~~
+If more than one exported thing is equal to a local thing (i.e., the
+local thing really is shared), then we do one only:
+\begin{verbatim}
+ x_local = ....
+ x_exported1 = x_local
+ x_exported2 = x_local
+==>
+ x_exported1 = ....
+
+ x_exported2 = x_exported1
+\end{verbatim}
+
+We rely on prior eta reduction to simplify things like
+\begin{verbatim}
+ x_exported = /\ tyvars -> x_local tyvars
+==>
+ x_exported = x_local
+\end{verbatim}
+Hence,there's a possibility of leaving unchanged something like this:
+\begin{verbatim}
+ x_local = ....
+ x_exported1 = x_local Int
+\end{verbatim}
+By the time we've thrown away the types in STG land this
+could be eliminated. But I don't think it's very common
+and it's dangerous to do this fiddling in STG land
+because we might elminate a binding that's mentioned in the
+unfolding for something.
+
+\begin{code}
+type IndEnv = IdEnv Id -- Maps local_id -> exported_id
+
+shortOutIndirections :: [CoreBind] -> [CoreBind]
+shortOutIndirections binds
+ | isEmptyVarEnv ind_env = binds
+ | no_need_to_flatten = binds'
+ | otherwise = [Rec (flattenBinds binds')] -- See Note [Rules and indirect-zapping]
+ where
+ ind_env = makeIndEnv binds
+ exp_ids = varSetElems ind_env -- These exported Ids are the subjects
+ exp_id_set = mkVarSet exp_ids -- of the indirection-elimination
+ no_need_to_flatten = all (null . specInfoRules . idSpecialisation) exp_ids
+ binds' = concatMap zap binds
+
+ zap (NonRec bndr rhs) = [NonRec b r | (b,r) <- zapPair (bndr,rhs)]
+ zap (Rec pairs) = [Rec (concatMap zapPair pairs)]
+
+ zapPair (bndr, rhs)
+ | bndr `elemVarSet` exp_id_set = []
+ | Just exp_id <- lookupVarEnv ind_env bndr = [(transferIdInfo exp_id bndr, rhs),
+ (bndr, Var exp_id)]
+ | otherwise = [(bndr,rhs)]
+
+makeIndEnv :: [CoreBind] -> IndEnv
+makeIndEnv binds
+ = foldr add_bind emptyVarEnv binds
+ where
+ add_bind :: CoreBind -> IndEnv -> IndEnv
+ add_bind (NonRec exported_id rhs) env = add_pair (exported_id, rhs) env
+ add_bind (Rec pairs) env = foldr add_pair env pairs
+
+ add_pair :: (Id,CoreExpr) -> IndEnv -> IndEnv
+ add_pair (exported_id, Var local_id) env
+ | shortMeOut env exported_id local_id = extendVarEnv env local_id exported_id
+ add_pair (exported_id, rhs) env
+ = env
+
+shortMeOut ind_env exported_id local_id
+-- The if-then-else stuff is just so I can get a pprTrace to see
+-- how often I don't get shorting out becuase of IdInfo stuff
+ = if isExportedId exported_id && -- Only if this is exported
+
+ isLocalId local_id && -- Only if this one is defined in this
+ -- module, so that we *can* change its
+ -- binding to be the exported thing!
+
+ not (isExportedId local_id) && -- Only if this one is not itself exported,
+ -- since the transformation will nuke it
+
+ not (local_id `elemVarEnv` ind_env) -- Only if not already substituted for
+ then
+ True
+
+{- No longer needed
+ if isEmptySpecInfo (specInfo (idInfo exported_id)) -- Only if no rules
+ then True -- See note on "Messing up rules"
+ else
+#ifdef DEBUG
+ pprTrace "shortMeOut:" (ppr exported_id)
+#endif
+ False
+-}
+ else
+ False
+
+
+-----------------
+transferIdInfo :: Id -> Id -> Id
+transferIdInfo exported_id local_id
+ = modifyIdInfo transfer exported_id
+ where
+ local_info = idInfo local_id
+ transfer exp_info = exp_info `setNewStrictnessInfo` newStrictnessInfo local_info
+ `setWorkerInfo` workerInfo local_info
+ `setSpecInfo` addSpecInfo (specInfo exp_info)
+ (specInfo local_info)
+\end{code}
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