dopt_CoreToDo, buildCoreToDo
)
import CoreSyn
-import CoreFVs ( ruleRhsFreeVars )
-import HscTypes ( HscEnv(..), GhciMode(..),
- ModGuts(..), ModGuts, Avails, availsToNameSet,
- ModDetails(..),
- HomeModInfo(..), ExternalPackageState(..), hscEPS
- )
+import TcIface ( loadImportedRules )
+import HscTypes ( HscEnv(..), ModGuts(..), ExternalPackageState(..),
+ Dependencies( dep_mods ),
+ hscEPS, hptRules )
import CSE ( cseProgram )
-import Rules ( RuleBase, emptyRuleBase, ruleBaseIds,
- extendRuleBaseList, pprRuleBase,
- ruleCheckProgram )
-import Module ( moduleEnvElts )
-import Name ( Name, isExternalName )
-import NameSet ( elemNameSet )
-import PprCore ( pprCoreBindings, pprCoreExpr )
-import OccurAnal ( occurAnalyseBinds, occurAnalyseGlobalExpr )
+import Rules ( RuleBase, ruleBaseIds, emptyRuleBase,
+ extendRuleBaseList, pprRuleBase, ruleCheckProgram )
+import PprCore ( pprCoreBindings, pprCoreExpr, pprIdRules )
+import OccurAnal ( occurAnalysePgm, occurAnalyseGlobalExpr )
+import IdInfo ( setNewStrictnessInfo, newStrictnessInfo,
+ setWorkerInfo, workerInfo,
+ setSpecInfo, specInfo )
import CoreUtils ( coreBindsSize )
import Simplify ( simplTopBinds, simplExpr )
-import SimplUtils ( simplBinders )
+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 ( idName, setIdLocalExported )
+import Id ( Id, modifyIdInfo, idInfo, idIsFrom, isExportedId, isLocalId,
+ idSpecialisation, setIdSpecialisation )
+import Rules ( addRules )
import VarSet
+import VarEnv
import LiberateCase ( liberateCase )
import SAT ( doStaticArgs )
import Specialise ( specProgram)
import UniqSupply ( UniqSupply, mkSplitUniqSupply, splitUniqSupply )
import IO ( hPutStr, stderr )
import Outputable
-
+import List ( partition )
import Maybes ( orElse )
-import List ( partition )
\end{code}
%************************************************************************
-> ModGuts
-> IO ModGuts
-core2core hsc_env
- mod_impl@(ModGuts { mg_exports = exports,
- mg_binds = binds_in,
- mg_rules = rules_in })
+core2core hsc_env guts
= do
- let dflags = hsc_dflags hsc_env
- ghci_mode = hsc_mode hsc_env
+ let dflags = hsc_dflags hsc_env
core_todos
| Just todo <- dopt_CoreToDo dflags = todo
| otherwise = buildCoreToDo dflags
- us <- mkSplitUniqSupply 's'
+ us <- mkSplitUniqSupply 's'
let (cp_us, ru_us) = splitUniqSupply us
-- COMPUTE THE RULE BASE TO USE
- (rule_base, local_rule_ids, orphan_rules)
- <- prepareRules hsc_env ru_us binds_in rules_in
-
- -- PREPARE THE BINDINGS
- let binds1 = updateBinders ghci_mode local_rule_ids
- orphan_rules exports binds_in
+ (imp_rule_base, guts') <- prepareRules hsc_env guts ru_us
-- DO THE BUSINESS
- (stats, processed_binds)
- <- doCorePasses dflags rule_base (zeroSimplCount dflags) cp_us binds1 core_todos
+ (stats, guts'') <- doCorePasses hsc_env cp_us
+ (zeroSimplCount dflags)
+ imp_rule_base guts' core_todos
dumpIfSet_dyn dflags Opt_D_dump_simpl_stats
"Grand total simplifier statistics"
(pprSimplCount stats)
- -- Return results
- -- We only return local orphan rules, i.e., local rules not attached to an Id
- -- The bindings cotain more rules, embedded in the Ids
- return (mod_impl { mg_binds = processed_binds, mg_rules = orphan_rules})
+ return guts''
simplifyExpr :: DynFlags -- includes spec of what core-to-core passes to do
; us <- mkSplitUniqSupply 's'
- ; let env = emptySimplEnv SimplGently [] emptyVarSet
- (expr', _counts) = initSmpl dflags us (simplExprGently env expr)
+ ; let (expr', _counts) = initSmpl dflags us $
+ simplExprGently gentleSimplEnv expr
; dumpIfSet_dyn dflags Opt_D_dump_simpl "Simplified expression"
(pprCoreExpr expr')
; return expr'
}
+gentleSimplEnv :: SimplEnv
+gentleSimplEnv = mkSimplEnv SimplGently
+ (isAmongSimpl [])
+ emptyRuleBase
-doCorePasses :: DynFlags
- -> RuleBase -- the main rule base
- -> SimplCount -- simplifier stats
+doCorePasses :: HscEnv
-> UniqSupply -- uniques
- -> [CoreBind] -- local binds in (with rules attached)
+ -> SimplCount -- simplifier stats
+ -> RuleBase -- the main rule base
+ -> ModGuts -- local binds in (with rules attached)
-> [CoreToDo] -- which passes to do
- -> IO (SimplCount, [CoreBind]) -- stats, binds, local orphan rules
+ -> IO (SimplCount, ModGuts)
-doCorePasses dflags rb stats us binds []
- = return (stats, binds)
+doCorePasses hsc_env us stats rb guts []
+ = return (stats, guts)
-doCorePasses dflags rb stats us binds (to_do : to_dos)
+doCorePasses hsc_env us stats rb guts (to_do : to_dos)
= do
let (us1, us2) = splitUniqSupply us
-
- (stats1, binds1) <- doCorePass dflags rb us1 binds to_do
-
- doCorePasses dflags rb (stats `plusSimplCount` stats1) us2 binds1 to_dos
-
-doCorePass dfs rb us binds (CoreDoSimplify mode switches)
- = _scc_ "Simplify" simplifyPgm dfs rb mode switches us binds
-doCorePass dfs rb us binds CoreCSE
- = _scc_ "CommonSubExpr" noStats dfs (cseProgram dfs binds)
-doCorePass dfs rb us binds CoreLiberateCase
- = _scc_ "LiberateCase" noStats dfs (liberateCase dfs binds)
-doCorePass dfs rb us binds CoreDoFloatInwards
- = _scc_ "FloatInwards" noStats dfs (floatInwards dfs binds)
-doCorePass dfs rb us binds (CoreDoFloatOutwards f)
- = _scc_ "FloatOutwards" noStats dfs (floatOutwards dfs f us binds)
-doCorePass dfs rb us binds CoreDoStaticArgs
- = _scc_ "StaticArgs" noStats dfs (doStaticArgs us binds)
-doCorePass dfs rb us binds CoreDoStrictness
- = _scc_ "Stranal" noStats dfs (dmdAnalPgm dfs binds)
-doCorePass dfs rb us binds CoreDoWorkerWrapper
- = _scc_ "WorkWrap" noStats dfs (wwTopBinds dfs us binds)
-doCorePass dfs rb us binds CoreDoSpecialising
- = _scc_ "Specialise" noStats dfs (specProgram dfs us binds)
-doCorePass dfs rb us binds CoreDoSpecConstr
- = _scc_ "SpecConstr" noStats dfs (specConstrProgram dfs us binds)
-#ifdef OLD_STRICTNESS
-doCorePass dfs rb us binds CoreDoOldStrictness
- = _scc_ "OldStrictness" noStats dfs (doOldStrictness dfs binds)
+ (stats1, rb1, guts1) <- doCorePass to_do hsc_env us1 rb guts
+ doCorePasses hsc_env us2 (stats `plusSimplCount` stats1) rb1 guts1 to_dos
+
+doCorePass (CoreDoSimplify mode sws) = _scc_ "Simplify" simplifyPgm mode sws
+doCorePass CoreCSE = _scc_ "CommonSubExpr" trBinds cseProgram
+doCorePass CoreLiberateCase = _scc_ "LiberateCase" trBinds liberateCase
+doCorePass CoreDoFloatInwards = _scc_ "FloatInwards" trBinds floatInwards
+doCorePass (CoreDoFloatOutwards f) = _scc_ "FloatOutwards" trBindsU (floatOutwards f)
+doCorePass CoreDoStaticArgs = _scc_ "StaticArgs" trBinds doStaticArgs
+doCorePass CoreDoStrictness = _scc_ "Stranal" trBinds dmdAnalPgm
+doCorePass CoreDoWorkerWrapper = _scc_ "WorkWrap" trBindsU wwTopBinds
+doCorePass CoreDoSpecialising = _scc_ "Specialise" trBindsU specProgram
+doCorePass CoreDoSpecConstr = _scc_ "SpecConstr" trBindsU specConstrProgram
+doCorePass CoreDoGlomBinds = trBinds glomBinds
+doCorePass CoreDoPrintCore = observe printCore
+doCorePass (CoreDoRuleCheck phase pat) = observe (ruleCheck phase pat)
+doCorePass CoreDoNothing = observe (\ _ _ -> return ())
+#ifdef OLD_STRICTNESS
+doCorePass CoreDoOldStrictness = _scc_ "OldStrictness" trBinds doOldStrictness
#endif
-doCorePass dfs rb us binds CoreDoPrintCore
- = _scc_ "PrintCore" noStats dfs (printCore binds)
-doCorePass dfs rb us binds CoreDoGlomBinds
- = noStats dfs (glomBinds dfs binds)
-doCorePass dfs rb us binds (CoreDoRuleCheck phase pat)
- = noStats dfs (ruleCheck dfs phase pat binds)
-doCorePass dfs rb us binds CoreDoNothing
- = noStats dfs (return binds)
#ifdef OLD_STRICTNESS
-doOldStrictness dfs binds
+doOldStrictness dfs binds
= do binds1 <- saBinds dfs binds
binds2 <- cprAnalyse dfs binds1
return binds2
#endif
-printCore binds = do dumpIfSet True "Print Core"
- (pprCoreBindings binds)
- return binds
+printCore _ binds = dumpIfSet True "Print Core" (pprCoreBindings binds)
-ruleCheck dflags phase pat binds = do showPass dflags "RuleCheck"
+ruleCheck phase pat dflags binds = do showPass dflags "RuleCheck"
printDump (ruleCheckProgram phase pat binds)
- return binds
-
--- most passes return no stats and don't change rules
-noStats dfs thing = do { binds <- thing; return (zeroSimplCount dfs, binds) }
+-- Most passes return no stats and don't change rules
+trBinds :: (DynFlags -> [CoreBind] -> IO [CoreBind])
+ -> HscEnv -> UniqSupply -> RuleBase -> ModGuts
+ -> IO (SimplCount, RuleBase, 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' }) }
+ where
+ dflags = hsc_dflags hsc_env
+
+trBindsU :: (DynFlags -> UniqSupply -> [CoreBind] -> IO [CoreBind])
+ -> HscEnv -> UniqSupply -> RuleBase -> ModGuts
+ -> IO (SimplCount, RuleBase, 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' }) }
+ 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)
+observe do_pass hsc_env us rb guts
+ = do { binds <- do_pass dflags (mg_binds guts)
+ ; return (zeroSimplCount dflags, rb, guts) }
+ where
+ dflags = hsc_dflags hsc_env
\end{code}
-- prepareLocalRuleBase takes the CoreBinds and rules defined in this module.
-- It attaches those rules that are for local Ids to their binders, and
--- returns the remainder attached to Ids in an IdSet. It also returns
--- Ids mentioned on LHS of some rule; these should be blacklisted.
-
--- The rule Ids and LHS Ids are black-listed; that is, they aren't inlined
--- so that the opportunity to apply the rule isn't lost too soon
+-- returns the remainder attached to Ids in an IdSet.
\begin{code}
prepareRules :: HscEnv
+ -> ModGuts
-> UniqSupply
- -> [CoreBind]
- -> [IdCoreRule] -- Local rules
- -> IO (RuleBase, -- Full rule base
- IdSet, -- Local rule Ids
- [IdCoreRule]) -- Orphan rules defined in this module
+ -> 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
+ 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 })
- us binds local_rules
+ guts@(ModGuts { mg_binds = binds, mg_deps = deps, mg_rules = local_rules })
+ us
= do { eps <- hscEPS hsc_env
- ; let env = emptySimplEnv SimplGently [] local_ids
+ ; 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)
- ; let (local_rules, orphan_rules) = partition ((`elemVarSet` local_ids) . fst) better_rules
- -- We use (`elemVarSet` local_ids) rather than isLocalId because
- -- isLocalId isn't true of class methods.
+ (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 the
- -- same as the rule-id set), and now the binding for the class method
+ -- 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 #-}
- local_rule_base = extendRuleBaseList emptyRuleBase local_rules
- local_rule_ids = ruleBaseIds local_rule_base -- Local Ids with rules attached
- imp_rule_base = foldl add_rules (eps_rule_base eps) (moduleEnvElts hpt)
- final_rule_base = extendRuleBaseList imp_rule_base orphan_rules
+ -- 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.
+ --
+ -- Reason
+ -- - It makes the rules easier to look up
+ -- - It means that transformation rules and specialisations for
+ -- locally defined Ids are handled uniformly
+ -- - It keeps alive things that are referred to only from a rule
+ -- (the occurrence analyser knows about rules attached to Ids)
+ -- - It makes sure that, when we apply a rule, the free vars
+ -- of the RHS are more likely to be in scope
+ -- - The imported rules are carried in the in-scope set
+ -- 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
+ local_rule_base = extendRuleBaseList emptyRuleBase rules_for_locals
+ binds_w_rules = updateBinders local_rule_base binds
; dumpIfSet_dyn dflags Opt_D_dump_rules "Transformation rules"
- (vcat [text "Local rules", pprRuleBase local_rule_base,
+ (vcat [text "Local rules", pprIdRules better_rules,
text "",
- text "Imported rules", pprRuleBase final_rule_base])
+ text "Imported rules", pprRuleBase imp_rule_base])
- ; return (final_rule_base, local_rule_ids, orphan_rules)
+#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 })
}
- where
- add_rules rule_base mod_info = extendRuleBaseList rule_base (md_rules (hm_details mod_info))
-
- -- Boringly, we need to gather the in-scope set.
- local_ids = foldr (unionVarSet . mkVarSet . bindersOf) emptyVarSet binds
-
-updateBinders :: GhciMode
- -> IdSet -- Locally defined ids with their Rules attached
- -> [IdCoreRule] -- Orphan rules
- -> Avails -- What is exported
- -> [CoreBind] -> [CoreBind]
- -- A horrible function
-
--- Update the binders of top-level bindings as follows
--- a) Attach the rules for each locally-defined Id to that Id.
--- b) Set the no-discard flag if either the Id is exported,
--- or it's mentioned in the RHS of a rule
---
--- You might wonder why exported Ids aren't already marked as such;
--- it's just because the type checker is rather busy already and
--- I didn't want to pass in yet another mapping.
---
--- Reason for (a)
--- - It makes the rules easier to look up
--- - It means that transformation rules and specialisations for
--- locally defined Ids are handled uniformly
--- - It keeps alive things that are referred to only from a rule
--- (the occurrence analyser knows about rules attached to Ids)
--- - It makes sure that, when we apply a rule, the free vars
--- of the RHS are more likely to be in scope
---
--- Reason for (b)
--- It means that the binding won't be discarded EVEN if the binding
--- ends up being trivial (v = w) -- the simplifier would usually just
--- substitute w for v throughout, but we don't apply the substitution to
--- the rules (maybe we should?), so this substitution would make the rule
--- bogus.
-
-updateBinders ghci_mode rule_ids orphan_rules exports binds
+updateBinders :: RuleBase -> [CoreBind] -> [CoreBind]
+updateBinders rule_base 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
- | dont_discard bndr = setIdLocalExported bndr_with_rules
- | otherwise = bndr_with_rules
- where
- bndr_with_rules = lookupVarSet rule_ids bndr `orElse` bndr
-
- orph_rhs_fvs = unionVarSets (map (ruleRhsFreeVars . snd) orphan_rules)
- -- An orphan rule must keep alive the free vars
- -- of its right-hand side.
- -- Non-orphan rules are attached to the Id (bndr_with_rules above)
- -- and that keeps the rhs free vars alive
-
- dont_discard bndr = is_exported (idName bndr)
- || bndr `elemVarSet` orph_rhs_fvs
-
- -- In interactive mode, we don't want to discard any top-level
- -- entities at all (eg. do not inline them away during
- -- simplification), and retain them all in the TypeEnv so they are
- -- available from the command line.
- --
- -- isExternalName separates the user-defined top-level names from those
- -- introduced by the type checker.
- is_exported :: Name -> Bool
- is_exported | ghci_mode == Interactive = isExternalName
- | otherwise = (`elemNameSet` export_fvs)
-
- export_fvs = availsToNameSet exports
+ update_bndr bndr = case lookupVarSet rule_ids bndr of
+ Nothing -> bndr
+ Just id -> bndr `setIdSpecialisation` idSpecialisation id
\end{code}
This doesn't match unless you do eta reduction on the build argument.
\begin{code}
-simplRule env rule@(id, BuiltinRule _ _)
+simplRule env rule@(IdCoreRule id _ (BuiltinRule _ _))
= returnSmpl rule
-simplRule env rule@(id, Rule act name bndrs args rhs)
+simplRule env (IdCoreRule id is_orph (Rule act name bndrs args rhs))
= simplBinders env bndrs `thenSmpl` \ (env, bndrs') ->
mapSmpl (simplExprGently env) args `thenSmpl` \ args' ->
simplExprGently env rhs `thenSmpl` \ rhs' ->
- returnSmpl (id, Rule act name bndrs' args' rhs')
+ returnSmpl (IdCoreRule id is_orph (Rule act name bndrs' args' rhs'))
-- It's important that simplExprGently does eta reduction.
-- For example, in a rule like:
%************************************************************************
\begin{code}
-simplifyPgm :: DynFlags
- -> RuleBase
- -> SimplifierMode
+simplifyPgm :: SimplifierMode
-> [SimplifierSwitch]
+ -> HscEnv
-> UniqSupply
- -> [CoreBind] -- Input
- -> IO (SimplCount, [CoreBind]) -- New bindings
+ -> RuleBase
+ -> ModGuts
+ -> IO (SimplCount, RuleBase, ModGuts) -- New bindings
-simplifyPgm dflags rule_base
- mode switches us binds
+simplifyPgm mode switches hsc_env us rule_base guts
= do {
showPass dflags "Simplify";
- (termination_msg, it_count, counts_out, binds')
- <- iteration us 1 (zeroSimplCount dflags) binds;
+ (termination_msg, it_count, counts_out, rule_base', guts')
+ <- do_iteration us rule_base 1 (zeroSimplCount dflags) 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 binds';
+ endPass dflags "Simplify" Opt_D_verbose_core2core (mg_binds guts');
- return (counts_out, binds')
+ return (counts_out, rule_base', guts')
}
where
+ dflags = hsc_dflags hsc_env
phase_info = case mode of
SimplGently -> "gentle"
SimplPhase n -> show n
- imported_rule_ids = ruleBaseIds rule_base
- simpl_env = emptySimplEnv mode switches imported_rule_ids
- sw_chkr = getSwitchChecker simpl_env
+ sw_chkr = isAmongSimpl switches
max_iterations = intSwitchSet sw_chkr MaxSimplifierIterations `orElse` 2
- iteration us iteration_no counts binds
+ do_iteration us rule_base iteration_no counts guts
-- 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, binds)
+ return ("Simplifier baled out", iteration_no - 1, counts, rule_base, guts)
}
-- Try and force thunks off the binds; significantly reduces
-- space usage, especially with -O. JRS, 000620.
- | let sz = coreBindsSize binds in sz == sz
+ | let sz = coreBindsSize (mg_binds guts) in sz == sz
= do {
-- Occurrence analysis
- let { tagged_binds = _scc_ "OccAnal" occurAnalyseBinds binds } ;
+ let { short_inds = _scc_ "ZapInd" shortOutIndirections (mg_binds guts) ;
+ tagged_binds = _scc_ "OccAnal" occurAnalysePgm short_inds } ;
+
+ dumpIfSet_dyn dflags Opt_D_dump_occur_anal "Short indirections"
+ (pprCoreBindings short_inds);
dumpIfSet_dyn dflags Opt_D_dump_occur_anal "Occurrence analysis"
(pprCoreBindings tagged_binds);
- -- SIMPLIFY
+ -- 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
+ ; 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
-- matching bit us with bad space leak!
-- With a let, we ended up with
-- case t of {(_,counts') -> if counts'=0 then ... }
-- So the conditional didn't force counts', because the
-- selection got duplicated. Sigh!
- case initSmpl dflags us1 (simplTopBinds simpl_env tagged_binds) of {
+ case initSmpl dflags us1 (_scc_ "SimplTopBinds" simplTopBinds simpl_env tagged_binds) of {
(binds', counts') -> do {
- -- The imported_rule_ids are used by initSmpl 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.
- let { all_counts = counts `plusSimplCount` counts' ;
- herald = "Simplifier phase " ++ phase_info ++
+ let { guts' = guts { mg_binds = binds' }
+ ; 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, binds')
+ return ("Simplifier reached fixed point", iteration_no,
+ all_counts, rule_base', guts')
else do {
-- Dump the result of this iteration
endPass dflags herald Opt_D_dump_simpl_iterations binds' ;
-- Loop
- iteration us2 (iteration_no + 1) all_counts binds'
+ do_iteration us2 rule_base' (iteration_no + 1) all_counts guts'
} } } }
where
(us1, us2) = splitUniqSupply us
\end{code}
+
+
+%************************************************************************
+%* *
+ Top-level occurrence analysis
+ [In here, not OccurAnal, because it uses
+ Rules.lhs, which depends on OccurAnal]
+%* *
+%************************************************************************
+
+In @occAnalPgm@ we do indirection-shorting. That is, 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
+ exp_id_set = mkVarSet exp_ids
+ no_need_to_flatten = all (null . rulesRules . 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 isEmptyCoreRules (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` addRules exported_id (specInfo exp_info)
+ (rulesRules (specInfo local_info))
+\end{code}
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