\section[SimplCore]{Driver for simplifying @Core@ programs}
\begin{code}
-module SimplCore ( core2core ) where
+module SimplCore ( core2core, simplifyExpr ) where
#include "HsVersions.h"
import CmdLineOpts ( CoreToDo(..), SimplifierSwitch(..),
- SwitchResult(..), switchIsOn, intSwitchSet,
- opt_D_dump_occur_anal, opt_D_dump_rules,
- opt_D_dump_simpl_iterations,
- opt_D_dump_simpl_stats,
- opt_D_dump_simpl, opt_D_dump_rules,
- opt_D_verbose_core2core,
- opt_D_dump_occur_anal,
- opt_UsageSPOn,
+ SwitchResult(..), intSwitchSet,
+ DynFlags, DynFlag(..), dopt, dopt_CoreToDo
)
-import CoreLint ( beginPass, endPass )
-import CoreTidy ( tidyCorePgm )
+import CoreLint ( showPass, endPass )
import CoreSyn
-import Rules ( RuleBase, ProtoCoreRule(..), pprProtoCoreRule, prepareRuleBase, orphanRule )
+import CoreFVs ( ruleRhsFreeVars )
+import HscTypes ( PersistentCompilerState(..),
+ PackageRuleBase, HomeSymbolTable, IsExported, ModDetails(..)
+ )
+import CSE ( cseProgram )
+import Rules ( RuleBase, emptyRuleBase, ruleBaseFVs, ruleBaseIds,
+ extendRuleBaseList, addRuleBaseFVs )
+import Module ( moduleEnvElts )
import CoreUnfold
-import PprCore ( pprCoreBindings )
+import PprCore ( pprCoreBindings, pprIdCoreRule, pprCoreExpr )
import OccurAnal ( occurAnalyseBinds )
-import CoreUtils ( exprIsTrivial, coreExprType )
+import CoreUtils ( etaReduceExpr, coreBindsSize )
import Simplify ( simplTopBinds, simplExpr )
-import SimplUtils ( etaCoreExpr, findDefault, simplBinders )
+import SimplUtils ( simplBinders )
import SimplMonad
-import Const ( Con(..), Literal(..), literalType, mkMachInt )
-import ErrUtils ( dumpIfSet )
+import ErrUtils ( dumpIfSet, dumpIfSet_dyn )
import FloatIn ( floatInwards )
import FloatOut ( floatOutwards )
-import Id ( Id, mkSysLocal, mkVanillaId, isBottomingId,
- idType, setIdType, idName, idInfo, setIdNoDiscard
- )
-import IdInfo ( InlinePragInfo(..), specInfo, setSpecInfo,
- inlinePragInfo, setInlinePragInfo,
- setUnfoldingInfo, setDemandInfo
- )
-import Demand ( wwLazy )
-import VarEnv
+import Id ( idName, isDataConWrapId, setIdNoDiscard, isLocalId )
import VarSet
-import Module ( Module )
-import Name ( mkLocalName, tidyOccName, tidyTopName,
- NamedThing(..), OccName
- )
-import TyCon ( TyCon, isDataTyCon )
-import PrimOp ( PrimOp(..) )
-import PrelInfo ( unpackCStringId, unpackCString2Id, addr2IntegerId )
-import Type ( Type, splitAlgTyConApp_maybe,
- isUnLiftedType,
- tidyType, tidyTypes, tidyTopType, tidyTyVar, tidyTyVars,
- Type
- )
-import TysWiredIn ( smallIntegerDataCon, isIntegerTy )
import LiberateCase ( liberateCase )
import SAT ( doStaticArgs )
import Specialise ( specProgram)
import WorkWrap ( wwTopBinds )
import CprAnalyse ( cprAnalyse )
-import Unique ( Unique, Uniquable(..),
- ratioTyConKey
- )
-import UniqSupply ( UniqSupply, mkSplitUniqSupply, splitUniqSupply, uniqFromSupply )
-import Constants ( tARGET_MIN_INT, tARGET_MAX_INT )
-import Util ( mapAccumL )
-import SrcLoc ( noSrcLoc )
-import Bag
-import Maybes
+import UniqSupply ( UniqSupply, mkSplitUniqSupply, splitUniqSupply )
import IO ( hPutStr, stderr )
import Outputable
-import Ratio ( numerator, denominator )
+import Maybes ( orElse )
+import List ( partition )
\end{code}
%************************************************************************
%************************************************************************
\begin{code}
-core2core :: [CoreToDo] -- Spec of what core-to-core passes to do
+core2core :: DynFlags -- includes spec of what core-to-core passes to do
+ -> PersistentCompilerState
+ -> HomeSymbolTable
+ -> IsExported
-> [CoreBind] -- Binds in
- -> [ProtoCoreRule] -- Rules
- -> IO ([CoreBind], [ProtoCoreRule])
+ -> [IdCoreRule] -- Rules in
+ -> IO ([CoreBind], [IdCoreRule]) -- binds, local orphan rules out
-core2core core_todos binds rules
+core2core dflags pcs hst is_exported binds rules
= do
+ let core_todos = dopt_CoreToDo dflags
+ let pkg_rule_base = pcs_rules pcs -- Rule-base accumulated from imported packages
+
us <- mkSplitUniqSupply 's'
- let (cp_us, us1) = splitUniqSupply us
- (ru_us, ps_us) = splitUniqSupply us1
+ let (cp_us, ru_us) = splitUniqSupply us
- better_rules <- simplRules ru_us rules binds
+ -- COMPUTE THE RULE BASE TO USE
+ (rule_base, local_rule_stuff, orphan_rules)
+ <- prepareRules dflags pkg_rule_base hst ru_us binds rules
- let (binds1, rule_base) = prepareRuleBase binds better_rules
+ -- PREPARE THE BINDINGS
+ let binds1 = updateBinders local_rule_stuff is_exported binds
- -- Do the main business
- (stats, processed_binds) <- doCorePasses zeroSimplCount cp_us binds1
- rule_base core_todos
+ -- DO THE BUSINESS
+ (stats, processed_binds)
+ <- doCorePasses dflags rule_base (zeroSimplCount dflags) cp_us binds1 core_todos
- dumpIfSet opt_D_dump_simpl_stats
+ dumpIfSet_dyn dflags Opt_D_dump_simpl_stats
"Grand total simplifier statistics"
(pprSimplCount stats)
- -- Do the post-simplification business
- post_simpl_binds <- doPostSimplification ps_us processed_binds
-
-- Return results
- return (post_simpl_binds, filter orphanRule better_rules)
-
+ -- 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 (processed_binds, orphan_rules)
+
+
+simplifyExpr :: DynFlags -- includes spec of what core-to-core passes to do
+ -> PersistentCompilerState
+ -> HomeSymbolTable
+ -> CoreExpr
+ -> IO CoreExpr
+simplifyExpr dflags pcs hst expr
+ = do {
+ ; us <- mkSplitUniqSupply 's'
+
+ ; let (expr', counts) = initSmpl dflags sw_chkr us emptyVarSet black_list_all
+ (simplExpr expr)
+
+ ; dumpIfSet_dyn dflags Opt_D_dump_simpl "Simplfied expression"
+ (pprCoreExpr expr')
+
+ ; return expr'
+ }
+ where
+ sw_chkr any = SwBool False -- A bit bogus
+ black_list_all v = True -- Black list everything
+
+
+doCorePasses :: DynFlags
+ -> RuleBase -- the main rule base
+ -> SimplCount -- simplifier stats
+ -> UniqSupply -- uniques
+ -> [CoreBind] -- local binds in (with rules attached)
+ -> [CoreToDo] -- which passes to do
+ -> IO (SimplCount, [CoreBind]) -- stats, binds, local orphan rules
-doCorePasses stats us binds irs []
+doCorePasses dflags rb stats us binds []
= return (stats, binds)
-doCorePasses stats us binds irs (to_do : to_dos)
+doCorePasses dflags rb stats us binds (to_do : to_dos)
= do
- let (us1, us2) = splitUniqSupply us
- (stats1, binds1) <- doCorePass us1 binds irs to_do
- doCorePasses (stats `plusSimplCount` stats1) us2 binds1 irs to_dos
-
-doCorePass us binds rb (CoreDoSimplify sw_chkr) = _scc_ "Simplify" simplifyPgm rb sw_chkr us binds
-doCorePass us binds rb CoreLiberateCase = _scc_ "LiberateCase" noStats (liberateCase binds)
-doCorePass us binds rb CoreDoFloatInwards = _scc_ "FloatInwards" noStats (floatInwards binds)
-doCorePass us binds rb CoreDoFullLaziness = _scc_ "FloatOutwards" noStats (floatOutwards us binds)
-doCorePass us binds rb CoreDoStaticArgs = _scc_ "StaticArgs" noStats (doStaticArgs us binds)
-doCorePass us binds rb CoreDoStrictness = _scc_ "Stranal" noStats (saBinds binds)
-doCorePass us binds rb CoreDoWorkerWrapper = _scc_ "WorkWrap" noStats (wwTopBinds us binds)
-doCorePass us binds rb CoreDoSpecialising = _scc_ "Specialise" noStats (specProgram us binds)
-doCorePass us binds rb CoreDoCPResult = _scc_ "CPResult" noStats (cprAnalyse binds)
-doCorePass us binds rb CoreDoPrintCore = _scc_ "PrintCore" noStats (printCore binds)
-doCorePass us binds rb CoreDoUSPInf
- = _scc_ "CoreUsageSPInf"
- if opt_UsageSPOn then
- noStats (doUsageSPInf us binds)
- else
- trace "WARNING: ignoring requested -fusagesp pass; requires -fusagesp-on" $
- noStats (return binds)
+ 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 sw_chkr)
+ = _scc_ "Simplify" simplifyPgm dfs rb sw_chkr 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 (saBinds 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 CoreDoCPResult
+ = _scc_ "CPResult" noStats dfs (cprAnalyse dfs binds)
+doCorePass dfs rb us binds CoreDoPrintCore
+ = _scc_ "PrintCore" noStats dfs (printCore binds)
+doCorePass dfs rb us binds CoreDoUSPInf
+ = _scc_ "CoreUsageSPInf" noStats dfs (doUsageSPInf dfs us binds)
+doCorePass dfs rb us binds CoreDoGlomBinds
+ = noStats dfs (glomBinds dfs binds)
+doCorePass dfs rb us binds CoreDoNothing
+ = noStats dfs (return binds)
printCore binds = do dumpIfSet True "Print Core"
(pprCoreBindings binds)
return binds
-noStats thing = do { result <- thing; return (zeroSimplCount, result) }
+-- most passes return no stats and don't change rules
+noStats dfs thing = do { binds <- thing; return (zeroSimplCount dfs, binds) }
\end{code}
+
%************************************************************************
%* *
\subsection{Dealing with rules}
%* *
%************************************************************************
-We must do some gentle simplifiation on the template (but not the RHS)
-of each rule. The case that forced me to add this was the fold/build rule,
-which without simplification looked like:
- fold k z (build (/\a. g a)) ==> ...
-This doesn't match unless you do eta reduction on the build argument.
+-- 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
\begin{code}
-simplRules :: UniqSupply -> [ProtoCoreRule] -> [CoreBind] -> IO [ProtoCoreRule]
-simplRules us rules binds
- = do let (better_rules,_) = initSmpl sw_chkr us bind_vars black_list_all (mapSmpl simplRule rules)
-
- dumpIfSet opt_D_dump_rules
- "Transformation rules"
- (vcat (map pprProtoCoreRule better_rules))
-
- return better_rules
+prepareRules :: DynFlags -> PackageRuleBase -> HomeSymbolTable
+ -> UniqSupply
+ -> [CoreBind]
+ -> [IdCoreRule] -- Local rules
+ -> IO (RuleBase, -- Full rule base
+ (IdSet,IdSet), -- Local rule Ids, and RHS fvs
+ [IdCoreRule]) -- Orphan rules
+
+prepareRules dflags pkg_rule_base hst us binds rules
+ = do { let (better_rules,_) = initSmpl dflags sw_chkr us local_ids black_list_all
+ (mapSmpl simplRule rules)
+
+ ; dumpIfSet_dyn dflags Opt_D_dump_rules "Transformation rules"
+ (vcat (map pprIdCoreRule better_rules))
+
+ ; let (local_rules, orphan_rules) = partition (isLocalId . fst) better_rules
+ local_rule_rhs_fvs = unionVarSets (map (ruleRhsFreeVars . snd) local_rules)
+ 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 pkg_rule_base (moduleEnvElts hst)
+ rule_base = extendRuleBaseList imp_rule_base orphan_rules
+ final_rule_base = addRuleBaseFVs rule_base (ruleBaseFVs local_rule_base)
+ -- The last step black-lists the free vars of local rules too
+
+ ; return (final_rule_base, (local_rule_ids, local_rule_rhs_fvs), orphan_rules)
+ }
where
- black_list_all v = True -- This stops all inlining
- sw_chkr any = SwBool False -- A bit bogus
+ sw_chkr any = SwBool False -- A bit bogus
+ black_list_all v = not (isDataConWrapId v)
+ -- This stops all inlining except the
+ -- wrappers for data constructors
+
+ add_rules rule_base mds = extendRuleBaseList rule_base (md_rules mds)
-- Boringly, we need to gather the in-scope set.
- -- Typically this thunk won't even be force, but the test in
- -- simpVar fails if it isn't right, and it might conceivably matter
- bind_vars = foldr (unionVarSet . mkVarSet . bindersOf) emptyVarSet binds
+ -- Typically this thunk won't even be forced, but the test in
+ -- simpVar fails if it isn't right, and it might conceiveably matter
+ local_ids = foldr (unionVarSet . mkVarSet . bindersOf) emptyVarSet binds
+
+
+updateBinders :: (IdSet, -- Locally defined ids with their Rules attached
+ IdSet) -- Ids free in the RHS of local rules
+ -> IsExported
+ -> [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 mentoined in the RHS of a rule
+--
+-- 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 (rule_ids, rule_rhs_fvs) is_exported binds
+ = map update_bndrs binds
+ where
+ 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
+ | is_exported (idName bndr)
+ || bndr `elemVarSet` rule_rhs_fvs = setIdNoDiscard bndr'
+ | otherwise = bndr'
+ where
+ bndr' = lookupVarSet rule_ids bndr `orElse` bndr
+\end{code}
-simplRule rule@(ProtoCoreRule is_local id (Rule name bndrs args rhs))
- | not is_local
- = returnSmpl rule -- No need to fiddle with imported rules
- | otherwise
+We must do some gentle simplification on the template (but not the RHS)
+of each rule. The case that forced me to add this was the fold/build rule,
+which without simplification looked like:
+ fold k z (build (/\a. g a)) ==> ...
+This doesn't match unless you do eta reduction on the build argument.
+
+\begin{code}
+simplRule rule@(id, BuiltinRule _)
+ = returnSmpl rule
+simplRule rule@(id, Rule name bndrs args rhs)
= simplBinders bndrs $ \ bndrs' ->
- mapSmpl simplExpr args `thenSmpl` \ args' ->
+ mapSmpl simpl_arg args `thenSmpl` \ args' ->
simplExpr rhs `thenSmpl` \ rhs' ->
- returnSmpl (ProtoCoreRule is_local id (Rule name bndrs' args' rhs'))
+ returnSmpl (id, Rule name bndrs' args' rhs')
+
+simpl_arg e
+-- I've seen rules in which a LHS like
+-- augment g (build h)
+-- turns into
+-- augment (\a. g a) (build h)
+-- So it's a help to eta-reduce the args as we simplify them.
+-- Otherwise we don't match when given an argument like
+-- (\a. h a a)
+ = simplExpr e `thenSmpl` \ e' ->
+ returnSmpl (etaReduceExpr e')
\end{code}
+
+%************************************************************************
+%* *
+\subsection{Glomming}
+%* *
+%************************************************************************
+
+\begin{code}
+glomBinds :: DynFlags -> [CoreBind] -> IO [CoreBind]
+-- Glom all binds together in one Rec, in case any
+-- transformations have introduced any new dependencies
+--
+-- NB: the global invariant is this:
+-- *** the top level bindings are never cloned, and are always unique ***
+--
+-- We sort them into dependency order, but applying transformation rules may
+-- make something at the top refer to something at the bottom:
+-- f = \x -> p (q x)
+-- h = \y -> 3
+--
+-- RULE: p (q x) = h x
+--
+-- Applying this rule makes f refer to h,
+-- although it doesn't appear to in the source program.
+-- This pass lets us control where it happens.
+--
+-- NOTICE that this cannot happen for rules whose head is a locally-defined
+-- function. It only happens for rules whose head is an imported function
+-- (p in the example above). So, for example, the rule had been
+-- RULE: f (p x) = h x
+-- then the rule for f would be attached to f itself (in its IdInfo)
+-- by prepareLocalRuleBase and h would be regarded by the occurrency
+-- analyser as free in f.
+
+glomBinds dflags binds
+ = do { showPass dflags "GlomBinds" ;
+ let { recd_binds = [Rec (flattenBinds binds)] } ;
+ return recd_binds }
+ -- Not much point in printing the result...
+ -- just consumes output bandwidth
+\end{code}
+
+
%************************************************************************
%* *
\subsection{The driver for the simplifier}
%************************************************************************
\begin{code}
-simplifyPgm :: RuleBase
+simplifyPgm :: DynFlags
+ -> RuleBase
-> (SimplifierSwitch -> SwitchResult)
-> UniqSupply
- -> [CoreBind] -- Input
- -> IO (SimplCount, [CoreBind]) -- New bindings
+ -> [CoreBind] -- Input
+ -> IO (SimplCount, [CoreBind]) -- New bindings
-simplifyPgm (imported_rule_ids, rule_lhs_fvs)
+simplifyPgm dflags rule_base
sw_chkr us binds
= do {
- beginPass "Simplify";
-
- -- Glom all binds together in one Rec, in case any
- -- transformations have introduced any new dependencies
- let { recd_binds = [Rec (flattenBinds binds)] };
+ showPass dflags "Simplify";
- (termination_msg, it_count, counts_out, binds') <- iteration us 1 zeroSimplCount recd_binds;
+ (termination_msg, it_count, counts_out, binds')
+ <- iteration us 1 (zeroSimplCount dflags) binds;
- dumpIfSet (opt_D_verbose_core2core && opt_D_dump_simpl_stats)
+ dumpIfSet (dopt Opt_D_verbose_core2core dflags
+ && dopt Opt_D_dump_simpl_stats dflags)
"Simplifier statistics"
(vcat [text termination_msg <+> text "after" <+> ppr it_count <+> text "iterations",
text "",
pprSimplCount counts_out]);
- endPass "Simplify"
- (opt_D_verbose_core2core && not opt_D_dump_simpl_iterations)
+ endPass dflags "Simplify"
+ (dopt Opt_D_verbose_core2core dflags
+ && not (dopt Opt_D_dump_simpl_iterations dflags))
binds' ;
return (counts_out, binds')
}
where
- max_iterations = getSimplIntSwitch sw_chkr MaxSimplifierIterations
- black_list_fn = blackListed rule_lhs_fvs (intSwitchSet sw_chkr SimplInlinePhase)
-
- core_iter_dump binds | opt_D_verbose_core2core = pprCoreBindings binds
- | otherwise = empty
-
+ max_iterations = getSimplIntSwitch sw_chkr MaxSimplifierIterations
+ black_list_fn = blackListed rule_lhs_fvs (intSwitchSet sw_chkr SimplInlinePhase)
+ imported_rule_ids = ruleBaseIds rule_base
+ rule_lhs_fvs = ruleBaseFVs rule_base
+
iteration us iteration_no counts binds
+ -- Try and force thunks off the binds; significantly reduces
+ -- space usage, especially with -O. JRS, 000620.
+ | let sz = coreBindsSize binds in sz == sz
= do {
-- Occurrence analysis
let { tagged_binds = _scc_ "OccAnal" occurAnalyseBinds binds } ;
- dumpIfSet opt_D_dump_occur_anal "Occurrence analysis"
+ dumpIfSet_dyn dflags Opt_D_dump_occur_anal "Occurrence analysis"
(pprCoreBindings tagged_binds);
- -- Simplify
- let { (binds', counts') = initSmpl sw_chkr us1 imported_rule_ids
- black_list_fn
- (simplTopBinds tagged_binds);
- all_counts = counts `plusSimplCount` counts'
- } ;
+ -- SIMPLIFY
+ -- 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
+ -- let
+ -- t = initSmpl ...
+ -- counts' = snd t
+ -- in
+ -- case t of {(_,counts') -> if counts'=0 then ...
+ -- So the conditional didn't force counts', because the
+ -- selection got duplicated. Sigh!
+ case initSmpl dflags sw_chkr us1 imported_rule_ids black_list_fn
+ (simplTopBinds 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' } ;
-- Stop if nothing happened; don't dump output
if isZeroSimplCount counts' then
else do {
-- Dump the result of this iteration
- dumpIfSet opt_D_dump_simpl_iterations
+ dumpIfSet_dyn dflags Opt_D_dump_simpl_iterations
("Simplifier iteration " ++ show iteration_no
++ " out of " ++ show max_iterations)
(pprSimplCount counts') ;
- if opt_D_dump_simpl_iterations then
- endPass ("Simplifier iteration " ++ show iteration_no ++ " result")
- opt_D_verbose_core2core
+ if dopt Opt_D_dump_simpl_iterations dflags then
+ endPass dflags
+ ("Simplifier iteration " ++ show iteration_no ++ " result")
+ (dopt Opt_D_verbose_core2core dflags)
binds'
else
return [] ;
-- Stop if we've run out of iterations
if iteration_no == max_iterations then
do {
+#ifdef DEBUG
if max_iterations > 2 then
hPutStr stderr ("NOTE: Simplifier still going after " ++
show max_iterations ++
" iterations; bailing out.\n")
- else return ();
+ else
+#endif
+ return ();
return ("Simplifier baled out", iteration_no, all_counts, binds')
}
-- Else loop
else iteration us2 (iteration_no + 1) all_counts binds'
- } }
+ } } } }
where
(us1, us2) = splitUniqSupply us
\end{code}
-
-
-%************************************************************************
-%* *
-\subsection{PostSimplification}
-%* *
-%************************************************************************
-
-Several tasks are performed by the post-simplification pass
-
-1. Make the representation of NoRep literals explicit, and
- float their bindings to the top level. We only do the floating
- part for NoRep lits inside a lambda (else no gain). We need to
- take care with let x = "foo" in e
- that we don't end up with a silly binding
- let x = y in e
- with a floated "foo". What a bore.
-
-2. *Mangle* cases involving par# in the discriminant. The unfolding
- for par in PrelConc.lhs include case expressions with integer
- results solely to fool the strictness analyzer, the simplifier,
- and anyone else who might want to fool with the evaluation order.
- At this point in the compiler our evaluation order is safe.
- Therefore, we convert expressions of the form:
-
- case par# e of
- 0# -> rhs
- _ -> parError#
- ==>
- case par# e of
- _ -> rhs
-
- fork# isn't handled like this - it's an explicit IO operation now.
- The reason is that fork# returns a ThreadId#, which gets in the
- way of the above scheme. And anyway, IO is the only guaranteed
- way to enforce ordering --SDM.
-
-4. Do eta reduction for lambda abstractions appearing in:
- - the RHS of case alternatives
- - the body of a let
-
- These will otherwise turn into local bindings during Core->STG;
- better to nuke them if possible. (In general the simplifier does
- eta expansion not eta reduction, up to this point. It does eta
- on the RHSs of bindings but not the RHSs of case alternatives and
- let bodies)
-
-
-------------------- NOT DONE ANY MORE ------------------------
-[March 98] Indirections are now elimianted by the occurrence analyser
-1. Eliminate indirections. The point here is to transform
- x_local = E
- x_exported = x_local
- ==>
- x_exported = E
-
-[Dec 98] [Not now done because there is no penalty in the code
- generator for using the former form]
-2. Convert
- case x of {...; x' -> ...x'...}
- ==>
- case x of {...; _ -> ...x... }
- See notes in SimplCase.lhs, near simplDefault for the reasoning here.
---------------------------------------------------------------
-
-Special case
-~~~~~~~~~~~~
-
-NOT ENABLED AT THE MOMENT (because the floated Ids are global-ish
-things, and we need local Ids for non-floated stuff):
-
- Don't float stuff out of a binder that's marked as a bottoming Id.
- Reason: it doesn't do any good, and creates more CAFs that increase
- the size of SRTs.
-
-eg.
-
- f = error "string"
-
-is translated to
-
- f' = unpackCString# "string"
- f = error f'
-
-hence f' and f become CAFs. Instead, the special case for
-tidyTopBinding below makes sure this comes out as
-
- f = let f' = unpackCString# "string" in error f'
-
-and we can safely ignore f as a CAF, since it can only ever be entered once.
-
-
-
-\begin{code}
-doPostSimplification :: UniqSupply -> [CoreBind] -> IO [CoreBind]
-doPostSimplification us binds_in
- = do
- beginPass "Post-simplification pass"
- let binds_out = initPM us (postSimplTopBinds binds_in)
- endPass "Post-simplification pass" opt_D_verbose_core2core binds_out
-
-postSimplTopBinds :: [CoreBind] -> PostM [CoreBind]
-postSimplTopBinds binds
- = mapPM postSimplTopBind binds `thenPM` \ binds' ->
- returnPM (bagToList (unionManyBags binds'))
-
-postSimplTopBind :: CoreBind -> PostM (Bag CoreBind)
-postSimplTopBind (NonRec bndr rhs)
- | isBottomingId bndr -- Don't lift out floats for bottoming Ids
- -- See notes above
- = getFloatsPM (postSimplExpr rhs) `thenPM` \ (rhs', floats) ->
- returnPM (unitBag (NonRec bndr (foldrBag Let rhs' floats)))
-
-postSimplTopBind bind
- = getFloatsPM (postSimplBind bind) `thenPM` \ (bind', floats) ->
- returnPM (floats `snocBag` bind')
-
-postSimplBind (NonRec bndr rhs)
- = postSimplExpr rhs `thenPM` \ rhs' ->
- returnPM (NonRec bndr rhs')
-
-postSimplBind (Rec pairs)
- = mapPM postSimplExpr rhss `thenPM` \ rhss' ->
- returnPM (Rec (bndrs `zip` rhss'))
- where
- (bndrs, rhss) = unzip pairs
-\end{code}
-
-
-Expressions
-~~~~~~~~~~~
-\begin{code}
-postSimplExpr (Var v) = returnPM (Var v)
-postSimplExpr (Type ty) = returnPM (Type ty)
-
-postSimplExpr (App fun arg)
- = postSimplExpr fun `thenPM` \ fun' ->
- postSimplExpr arg `thenPM` \ arg' ->
- returnPM (App fun' arg')
-
-postSimplExpr (Con (Literal lit) args)
- = ASSERT( null args )
- litToRep lit `thenPM` \ (lit_ty, lit_expr) ->
- getInsideLambda `thenPM` \ in_lam ->
- if in_lam && not (exprIsTrivial lit_expr) then
- -- It must have been a no-rep literal with a
- -- non-trivial representation; and we're inside a lambda;
- -- so float it to the top
- addTopFloat lit_ty lit_expr `thenPM` \ v ->
- returnPM (Var v)
- else
- returnPM lit_expr
-
-postSimplExpr (Con con args)
- = mapPM postSimplExpr args `thenPM` \ args' ->
- returnPM (Con con args')
-
-postSimplExpr (Lam bndr body)
- = insideLambda bndr $
- postSimplExpr body `thenPM` \ body' ->
- returnPM (Lam bndr body')
-
-postSimplExpr (Let bind body)
- = postSimplBind bind `thenPM` \ bind' ->
- postSimplExprEta body `thenPM` \ body' ->
- returnPM (Let bind' body')
-
-postSimplExpr (Note note body)
- = postSimplExprEta body `thenPM` \ body' ->
- returnPM (Note note body')
-
--- par#: see notes above.
-postSimplExpr (Case scrut@(Con (PrimOp op) args) bndr alts)
- | funnyParallelOp op && maybeToBool maybe_default
- = postSimplExpr scrut `thenPM` \ scrut' ->
- postSimplExprEta default_rhs `thenPM` \ rhs' ->
- returnPM (Case scrut' bndr [(DEFAULT,[],rhs')])
- where
- (other_alts, maybe_default) = findDefault alts
- Just default_rhs = maybe_default
-
-postSimplExpr (Case scrut case_bndr alts)
- = postSimplExpr scrut `thenPM` \ scrut' ->
- mapPM ps_alt alts `thenPM` \ alts' ->
- returnPM (Case scrut' case_bndr alts')
- where
- ps_alt (con,bndrs,rhs) = postSimplExprEta rhs `thenPM` \ rhs' ->
- returnPM (con, bndrs, rhs')
-
-postSimplExprEta e = postSimplExpr e `thenPM` \ e' ->
- returnPM (etaCoreExpr e')
-\end{code}
-
-\begin{code}
-funnyParallelOp ParOp = True
-funnyParallelOp _ = False
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection[coreToStg-lits]{Converting literals}
-%* *
-%************************************************************************
-
-Literals: the NoRep kind need to be de-no-rep'd.
-We always replace them with a simple variable, and float a suitable
-binding out to the top level.
-
-\begin{code}
-litToRep :: Literal -> PostM (Type, CoreExpr)
-
-litToRep (NoRepStr s ty)
- = returnPM (ty, rhs)
- where
- rhs = if (any is_NUL (_UNPK_ s))
-
- then -- Must cater for NULs in literal string
- mkApps (Var unpackCString2Id)
- [mkLit (MachStr s),
- mkLit (mkMachInt (toInteger (_LENGTH_ s)))]
-
- else -- No NULs in the string
- App (Var unpackCStringId) (mkLit (MachStr s))
-
- is_NUL c = c == '\0'
-\end{code}
-
-If an Integer is small enough (Haskell implementations must support
-Ints in the range $[-2^29+1, 2^29-1]$), wrap it up in @int2Integer@;
-otherwise, wrap with @addr2Integer@.
-
-\begin{code}
-litToRep (NoRepInteger i integer_ty)
- = returnPM (integer_ty, rhs)
- where
- rhs | i > tARGET_MIN_INT && -- Small enough, so start from an Int
- i < tARGET_MAX_INT
- = Con (DataCon smallIntegerDataCon) [Con (Literal (mkMachInt i)) []]
-
- | otherwise -- Big, so start from a string
- = App (Var addr2IntegerId) (Con (Literal (MachStr (_PK_ (show i)))) [])
-
-
-litToRep (NoRepRational r rational_ty)
- = postSimplExpr (mkLit (NoRepInteger (numerator r) integer_ty)) `thenPM` \ num_arg ->
- postSimplExpr (mkLit (NoRepInteger (denominator r) integer_ty)) `thenPM` \ denom_arg ->
- returnPM (rational_ty, mkConApp ratio_data_con [Type integer_ty, num_arg, denom_arg])
- where
- (ratio_data_con, integer_ty)
- = case (splitAlgTyConApp_maybe rational_ty) of
- Just (tycon, [i_ty], [con])
- -> ASSERT(isIntegerTy i_ty && getUnique tycon == ratioTyConKey)
- (con, i_ty)
-
- _ -> (panic "ratio_data_con", panic "integer_ty")
-
-litToRep other_lit = returnPM (literalType other_lit, mkLit other_lit)
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection{The monad}
-%* *
-%************************************************************************
-
-\begin{code}
-type PostM a = Bool -- True <=> inside a *value* lambda
- -> (UniqSupply, Bag CoreBind) -- Unique supply and Floats in
- -> (a, (UniqSupply, Bag CoreBind))
-
-initPM :: UniqSupply -> PostM a -> a
-initPM us m
- = case m False {- not inside lambda -} (us, emptyBag) of
- (result, _) -> result
-
-returnPM v in_lam usf = (v, usf)
-thenPM m k in_lam usf = case m in_lam usf of
- (r, usf') -> k r in_lam usf'
-
-mapPM f [] = returnPM []
-mapPM f (x:xs) = f x `thenPM` \ r ->
- mapPM f xs `thenPM` \ rs ->
- returnPM (r:rs)
-
-insideLambda :: CoreBndr -> PostM a -> PostM a
-insideLambda bndr m in_lam usf | isId bndr = m True usf
- | otherwise = m in_lam usf
-
-getInsideLambda :: PostM Bool
-getInsideLambda in_lam usf = (in_lam, usf)
-
-getFloatsPM :: PostM a -> PostM (a, Bag CoreBind)
-getFloatsPM m in_lam (us, floats)
- = let
- (a, (us', floats')) = m in_lam (us, emptyBag)
- in
- ((a, floats'), (us', floats))
-
-addTopFloat :: Type -> CoreExpr -> PostM Id
-addTopFloat lit_ty lit_rhs in_lam (us, floats)
- = let
- (us1, us2) = splitUniqSupply us
- uniq = uniqFromSupply us1
- lit_id = mkSysLocal SLIT("lf") uniq lit_ty
- in
- (lit_id, (us2, floats `snocBag` NonRec lit_id lit_rhs))
-\end{code}
-
-