\begin{code}
module SimplMonad (
InId, InBind, InExpr, InAlt, InArg, InType, InBinder,
- OutId, OutBind, OutExpr, OutAlt, OutArg, OutType, OutBinder,
- OutExprStuff, OutStuff,
+ OutId, OutTyVar, OutBind, OutExpr, OutAlt, OutArg, OutType, OutBinder,
+ FloatsWith, FloatsWithExpr,
-- The monad
SimplM,
initSmpl, returnSmpl, thenSmpl, thenSmpl_,
mapSmpl, mapAndUnzipSmpl, mapAccumLSmpl,
+ getDOptsSmpl,
- -- The inlining black-list
- setBlackList, getBlackList, noInlineBlackList,
+ -- The simplifier mode
+ setMode, getMode,
-- Unique supply
- getUniqueSmpl, getUniquesSmpl,
- newId, newIds,
+ getUniqueSmpl, getUniquesSmpl, getUniqSupplySmpl,
-- Counting
SimplCount, Tick(..),
plusSimplCount, isZeroSimplCount,
-- Switch checker
- SwitchChecker, getSwitchChecker, getSimplIntSwitch,
+ SwitchChecker, SwitchResult(..), getSwitchChecker, getSimplIntSwitch,
+ isAmongSimpl, intSwitchSet, switchIsOn,
-- Cost centres
getEnclosingCC, setEnclosingCC,
-- Environments
- getEnv, setAllExceptInScope,
- getSubst, setSubst,
+ SimplEnv, emptySimplEnv, getSubst, setSubst,
getSubstEnv, extendSubst, extendSubstList,
getInScope, setInScope, modifyInScope, addNewInScopeIds,
setSubstEnv, zapSubstEnv,
- getSimplBinderStuff, setSimplBinderStuff
+
+ -- Floats
+ Floats, emptyFloats, isEmptyFloats, unitFloat, addFloats, flattenFloats,
+ allLifted, wrapFloats, floatBinds,
+ addAuxiliaryBind,
+
+ -- Inlining,
+ preInlineUnconditionally, postInlineUnconditionally, activeInline, activeRule,
+ inlineMode
) where
#include "HsVersions.h"
-import Id ( Id, mkSysLocal, idUnfolding, isDataConWrapId )
+import Id ( Id, idType, idOccInfo, idInlinePragma )
import CoreSyn
-import CoreUnfold ( isCompulsoryUnfolding )
+import CoreUtils ( needsCaseBinding, exprIsTrivial )
import PprCore () -- Instances
import CostCentre ( CostCentreStack, subsumedCCS )
-import Name ( isLocallyDefined )
-import OccName ( UserFS )
+import Var
import VarEnv
import VarSet
+import OrdList
import qualified Subst
import Subst ( Subst, mkSubst, substEnv,
- InScopeSet, mkInScopeSet, substInScope, isInScope
+ InScopeSet, mkInScopeSet, substInScope,
+ isInScope
)
-import Type ( Type )
+import Type ( Type, isUnLiftedType )
import UniqSupply ( uniqsFromSupply, uniqFromSupply, splitUniqSupply,
UniqSupply
)
import FiniteMap
-import CmdLineOpts ( SimplifierSwitch(..), SwitchResult(..),
- opt_PprStyle_Debug, opt_HistorySize, opt_D_dump_simpl_stats,
- intSwitchSet
+import BasicTypes ( TopLevelFlag, isTopLevel,
+ Activation, isActive, isAlwaysActive,
+ OccInfo(..), isOneOcc
+ )
+import CmdLineOpts ( SimplifierSwitch(..), SimplifierMode(..),
+ DynFlags, DynFlag(..), dopt,
+ opt_PprStyle_Debug, opt_HistorySize, opt_SimplNoPreInlining,
)
import Unique ( Unique )
import Maybes ( expectJust )
-import Util ( zipWithEqual )
import Outputable
+import Array ( array, (//) )
+import FastTypes
+import GlaExts ( indexArray# )
+
+#if __GLASGOW_HASKELL__ < 503
+import PrelArr ( Array(..) )
+#else
+import GHC.Arr ( Array(..) )
+#endif
infixr 0 `thenSmpl`, `thenSmpl_`
\end{code}
type OutBinder = CoreBndr
type OutId = Id -- Cloned
+type OutTyVar = TyVar -- Cloned
type OutType = Type -- Cloned
type OutBind = CoreBind
type OutExpr = CoreExpr
type OutAlt = CoreAlt
type OutArg = CoreArg
+\end{code}
-type SwitchChecker = SimplifierSwitch -> SwitchResult
+%************************************************************************
+%* *
+\subsection{Floats}
+%* *
+%************************************************************************
-type OutExprStuff = OutStuff (InScopeSet, OutExpr)
-type OutStuff a = ([OutBind], a)
+\begin{code}
+type FloatsWithExpr = FloatsWith OutExpr
+type FloatsWith a = (Floats, a)
-- We return something equivalent to (let b in e), but
-- in pieces to avoid the quadratic blowup when floating
-- incrementally. Comments just before simplExprB in Simplify.lhs
+
+data Floats = Floats (OrdList OutBind)
+ InScopeSet -- Environment "inside" all the floats
+ Bool -- True <=> All bindings are lifted
+
+allLifted :: Floats -> Bool
+allLifted (Floats _ _ is_lifted) = is_lifted
+
+wrapFloats :: Floats -> OutExpr -> OutExpr
+wrapFloats (Floats bs _ _) body = foldrOL Let body bs
+
+isEmptyFloats :: Floats -> Bool
+isEmptyFloats (Floats bs _ _) = isNilOL bs
+
+floatBinds :: Floats -> [OutBind]
+floatBinds (Floats bs _ _) = fromOL bs
+
+flattenFloats :: Floats -> Floats
+-- Flattens into a single Rec group
+flattenFloats (Floats bs is is_lifted)
+ = ASSERT2( is_lifted, ppr (fromOL bs) )
+ Floats (unitOL (Rec (flattenBinds (fromOL bs)))) is is_lifted
+\end{code}
+
+\begin{code}
+emptyFloats :: SimplEnv -> Floats
+emptyFloats env = Floats nilOL (getInScope env) True
+
+unitFloat :: SimplEnv -> OutId -> OutExpr -> Floats
+-- A single non-rec float; extend the in-scope set
+unitFloat env var rhs = Floats (unitOL (NonRec var rhs))
+ (Subst.extendInScopeSet (getInScope env) var)
+ (not (isUnLiftedType (idType var)))
+
+addFloats :: SimplEnv -> Floats
+ -> (SimplEnv -> SimplM (FloatsWith a))
+ -> SimplM (FloatsWith a)
+addFloats env (Floats b1 is1 l1) thing_inside
+ | isNilOL b1
+ = thing_inside env
+ | otherwise
+ = thing_inside (setInScopeSet env is1) `thenSmpl` \ (Floats b2 is2 l2, res) ->
+ returnSmpl (Floats (b1 `appOL` b2) is2 (l1 && l2), res)
+
+addLetBind :: OutBind -> Floats -> Floats
+addLetBind bind (Floats binds in_scope lifted)
+ = Floats (bind `consOL` binds) in_scope (lifted && is_lifted_bind bind)
+
+is_lifted_bind (Rec _) = True
+is_lifted_bind (NonRec b r) = not (isUnLiftedType (idType b))
+
+-- addAuxiliaryBind * takes already-simplified things (bndr and rhs)
+-- * extends the in-scope env
+-- * assumes it's a let-bindable thing
+addAuxiliaryBind :: SimplEnv -> OutBind
+ -> (SimplEnv -> SimplM (FloatsWith a))
+ -> SimplM (FloatsWith a)
+ -- Extends the in-scope environment as well as wrapping the bindings
+addAuxiliaryBind env bind thing_inside
+ = ASSERT( case bind of { NonRec b r -> not (needsCaseBinding (idType b) r) ; Rec _ -> True } )
+ thing_inside (addNewInScopeIds env (bindersOf bind)) `thenSmpl` \ (floats, x) ->
+ returnSmpl (addLetBind bind floats, x)
\end{code}
(Command-line switches move around through the explicitly-passed SimplEnv.)
\begin{code}
-type SimplM result -- We thread the unique supply because
- = SimplEnv -- constantly splitting it is rather expensive
- -> UniqSupply
+type SimplM result
+ = DynFlags -- We thread the unique supply because
+ -> UniqSupply -- constantly splitting it is rather expensive
-> SimplCount
-> (result, UniqSupply, SimplCount)
-
-type BlackList = Id -> Bool -- True => don't inline this Id
-
-data SimplEnv
- = SimplEnv {
- seChkr :: SwitchChecker,
- seCC :: CostCentreStack, -- The enclosing CCS (when profiling)
- seBlackList :: BlackList,
- seSubst :: Subst -- The current substitution
- }
- -- The range of the substitution is OutType and OutExpr resp
- --
- -- The substitution is idempotent
- -- It *must* be applied; things in its domain simply aren't
- -- bound in the result.
- --
- -- The substitution usually maps an Id to its clone,
- -- but if the orig defn is a let-binding, and
- -- the RHS of the let simplifies to an atom,
- -- we just add the binding to the substitution and elide the let.
-
- -- The in-scope part of Subst includes *all* in-scope TyVars and Ids
- -- The elements of the set may have better IdInfo than the
- -- occurrences of in-scope Ids, and (more important) they will
- -- have a correctly-substituted type. So we use a lookup in this
- -- set to replace occurrences
\end{code}
\begin{code}
-initSmpl :: SwitchChecker
+initSmpl :: DynFlags
-> UniqSupply -- No init count; set to 0
- -> VarSet -- In scope (usually empty, but useful for nested calls)
- -> BlackList -- Black-list function
-> SimplM a
-> (a, SimplCount)
-initSmpl chkr us in_scope black_list m
- = case m (emptySimplEnv chkr in_scope black_list) us zeroSimplCount of
+initSmpl dflags us m
+ = case m dflags us (zeroSimplCount dflags) of
(result, _, count) -> (result, count)
{-# INLINE returnSmpl #-}
returnSmpl :: a -> SimplM a
-returnSmpl e env us sc = (e, us, sc)
+returnSmpl e dflags us sc = (e, us, sc)
thenSmpl :: SimplM a -> (a -> SimplM b) -> SimplM b
thenSmpl_ :: SimplM a -> SimplM b -> SimplM b
-thenSmpl m k env us0 sc0
- = case (m env us0 sc0) of
- (m_result, us1, sc1) -> k m_result env us1 sc1
+thenSmpl m k dflags us0 sc0
+ = case (m dflags us0 sc0) of
+ (m_result, us1, sc1) -> k m_result dflags us1 sc1
-thenSmpl_ m k env us0 sc0
- = case (m env us0 sc0) of
- (_, us1, sc1) -> k env us1 sc1
+thenSmpl_ m k dflags us0 sc0
+ = case (m dflags us0 sc0) of
+ (_, us1, sc1) -> k dflags us1 sc1
\end{code}
%************************************************************************
\begin{code}
-getUniqueSmpl :: SimplM Unique
-getUniqueSmpl env us sc = case splitUniqSupply us of
- (us1, us2) -> (uniqFromSupply us1, us2, sc)
+getUniqSupplySmpl :: SimplM UniqSupply
+getUniqSupplySmpl dflags us sc
+ = case splitUniqSupply us of
+ (us1, us2) -> (us1, us2, sc)
-getUniquesSmpl :: Int -> SimplM [Unique]
-getUniquesSmpl n env us sc = case splitUniqSupply us of
- (us1, us2) -> (uniqsFromSupply n us1, us2, sc)
+getUniqueSmpl :: SimplM Unique
+getUniqueSmpl dflags us sc
+ = case splitUniqSupply us of
+ (us1, us2) -> (uniqFromSupply us1, us2, sc)
+
+getUniquesSmpl :: SimplM [Unique]
+getUniquesSmpl dflags us sc
+ = case splitUniqSupply us of
+ (us1, us2) -> (uniqsFromSupply us1, us2, sc)
+
+getDOptsSmpl :: SimplM DynFlags
+getDOptsSmpl dflags us sc
+ = (dflags, us, sc)
\end{code}
\begin{code}
getSimplCount :: SimplM SimplCount
-getSimplCount env us sc = (sc, us, sc)
+getSimplCount dflags us sc = (sc, us, sc)
tick :: Tick -> SimplM ()
-tick t env us sc = sc' `seq` ((), us, sc')
- where
- sc' = doTick t sc
+tick t dflags us sc
+ = sc' `seq` ((), us, sc')
+ where
+ sc' = doTick t sc
freeTick :: Tick -> SimplM ()
-- Record a tick, but don't add to the total tick count, which is
-- used to decide when nothing further has happened
-freeTick t env us sc = sc' `seq` ((), us, sc')
- where
- sc' = doFreeTick t sc
+freeTick t dflags us sc
+ = sc' `seq` ((), us, sc')
+ where
+ sc' = doFreeTick t sc
\end{code}
\begin{code}
verboseSimplStats = opt_PprStyle_Debug -- For now, anyway
-zeroSimplCount :: SimplCount
+zeroSimplCount :: DynFlags -> SimplCount
isZeroSimplCount :: SimplCount -> Bool
pprSimplCount :: SimplCount -> SDoc
doTick, doFreeTick :: Tick -> SimplCount -> SimplCount
type TickCounts = FiniteMap Tick Int
-zeroSimplCount -- This is where we decide whether to do
+zeroSimplCount dflags
+ -- This is where we decide whether to do
-- the VerySimpl version or the full-stats version
- | opt_D_dump_simpl_stats = SimplCount {ticks = 0, details = emptyFM,
- n_log = 0, log1 = [], log2 = []}
- | otherwise = VerySimplZero
+ | dopt Opt_D_dump_simpl_stats dflags
+ = SimplCount {ticks = 0, details = emptyFM,
+ n_log = 0, log1 = [], log2 = []}
+ | otherwise
+ = VerySimplZero
isZeroSimplCount VerySimplZero = True
isZeroSimplCount (SimplCount { ticks = 0 }) = True
| UnfoldingDone Id
| RuleFired FAST_STRING -- Rule name
- | LetFloatFromLet Id -- Thing floated out
+ | LetFloatFromLet
| EtaExpansion Id -- LHS binder
| EtaReduction Id -- Binder on outer lambda
| BetaReduction Id -- Lambda binder
| CaseOfCase Id -- Bndr on *inner* case
| KnownBranch Id -- Case binder
| CaseMerge Id -- Binder on outer case
+ | AltMerge Id -- Case binder
| CaseElim Id -- Case binder
| CaseIdentity Id -- Case binder
| FillInCaseDefault Id -- Case binder
tickToTag (PostInlineUnconditionally _) = 1
tickToTag (UnfoldingDone _) = 2
tickToTag (RuleFired _) = 3
-tickToTag (LetFloatFromLet _) = 4
+tickToTag LetFloatFromLet = 4
tickToTag (EtaExpansion _) = 5
tickToTag (EtaReduction _) = 6
tickToTag (BetaReduction _) = 7
tickToTag (FillInCaseDefault _) = 13
tickToTag BottomFound = 14
tickToTag SimplifierDone = 16
+tickToTag (AltMerge _) = 17
tickString :: Tick -> String
tickString (PreInlineUnconditionally _) = "PreInlineUnconditionally"
tickString (PostInlineUnconditionally _)= "PostInlineUnconditionally"
tickString (UnfoldingDone _) = "UnfoldingDone"
tickString (RuleFired _) = "RuleFired"
-tickString (LetFloatFromLet _) = "LetFloatFromLet"
+tickString LetFloatFromLet = "LetFloatFromLet"
tickString (EtaExpansion _) = "EtaExpansion"
tickString (EtaReduction _) = "EtaReduction"
tickString (BetaReduction _) = "BetaReduction"
tickString (CaseOfCase _) = "CaseOfCase"
tickString (KnownBranch _) = "KnownBranch"
tickString (CaseMerge _) = "CaseMerge"
+tickString (AltMerge _) = "AltMerge"
tickString (CaseElim _) = "CaseElim"
tickString (CaseIdentity _) = "CaseIdentity"
tickString (FillInCaseDefault _) = "FillInCaseDefault"
pprTickCts (PostInlineUnconditionally v)= ppr v
pprTickCts (UnfoldingDone v) = ppr v
pprTickCts (RuleFired v) = ppr v
-pprTickCts (LetFloatFromLet v) = ppr v
+pprTickCts LetFloatFromLet = empty
pprTickCts (EtaExpansion v) = ppr v
pprTickCts (EtaReduction v) = ppr v
pprTickCts (BetaReduction v) = ppr v
pprTickCts (CaseOfCase v) = ppr v
pprTickCts (KnownBranch v) = ppr v
pprTickCts (CaseMerge v) = ppr v
+pprTickCts (AltMerge v) = ppr v
pprTickCts (CaseElim v) = ppr v
pprTickCts (CaseIdentity v) = ppr v
pprTickCts (FillInCaseDefault v) = ppr v
cmpEqTick (PostInlineUnconditionally a) (PostInlineUnconditionally b) = a `compare` b
cmpEqTick (UnfoldingDone a) (UnfoldingDone b) = a `compare` b
cmpEqTick (RuleFired a) (RuleFired b) = a `compare` b
-cmpEqTick (LetFloatFromLet a) (LetFloatFromLet b) = a `compare` b
cmpEqTick (EtaExpansion a) (EtaExpansion b) = a `compare` b
cmpEqTick (EtaReduction a) (EtaReduction b) = a `compare` b
cmpEqTick (BetaReduction a) (BetaReduction b) = a `compare` b
cmpEqTick (CaseOfCase a) (CaseOfCase b) = a `compare` b
cmpEqTick (KnownBranch a) (KnownBranch b) = a `compare` b
cmpEqTick (CaseMerge a) (CaseMerge b) = a `compare` b
+cmpEqTick (AltMerge a) (AltMerge b) = a `compare` b
cmpEqTick (CaseElim a) (CaseElim b) = a `compare` b
cmpEqTick (CaseIdentity a) (CaseIdentity b) = a `compare` b
cmpEqTick (FillInCaseDefault a) (FillInCaseDefault b) = a `compare` b
\end{code}
+
%************************************************************************
%* *
-\subsubsection{Command-line switches}
+\subsubsection{The @SimplEnv@ type}
%* *
%************************************************************************
+
\begin{code}
-getSwitchChecker :: SimplM SwitchChecker
-getSwitchChecker env us sc = (seChkr env, us, sc)
+data SimplEnv
+ = SimplEnv {
+ seMode :: SimplifierMode,
+ seChkr :: SwitchChecker,
+ seCC :: CostCentreStack, -- The enclosing CCS (when profiling)
+ seSubst :: Subst -- The current substitution
+ }
+ -- The range of the substitution is OutType and OutExpr resp
+ --
+ -- The substitution is idempotent
+ -- It *must* be applied; things in its domain simply aren't
+ -- bound in the result.
+ --
+ -- The substitution usually maps an Id to its clone,
+ -- but if the orig defn is a let-binding, and
+ -- the RHS of the let simplifies to an atom,
+ -- we just add the binding to the substitution and elide the let.
-getSimplIntSwitch :: SwitchChecker -> (Int-> SimplifierSwitch) -> Int
-getSimplIntSwitch chkr switch
- = expectJust "getSimplIntSwitch" (intSwitchSet chkr switch)
-\end{code}
+ -- The in-scope part of Subst includes *all* in-scope TyVars and Ids
+ -- The elements of the set may have better IdInfo than the
+ -- occurrences of in-scope Ids, and (more important) they will
+ -- have a correctly-substituted type. So we use a lookup in this
+ -- set to replace occurrences
+
+emptySimplEnv :: SimplifierMode -> [SimplifierSwitch] -> VarSet -> SimplEnv
+emptySimplEnv mode switches in_scope
+ = SimplEnv { seChkr = isAmongSimpl switches, seCC = subsumedCCS, seMode = mode,
+ seSubst = mkSubst (mkInScopeSet in_scope) emptySubstEnv }
+ -- The top level "enclosing CC" is "SUBSUMED".
+---------------------
+getSwitchChecker :: SimplEnv -> SwitchChecker
+getSwitchChecker env = seChkr env
-@setBlackList@ is used to prepare the environment for simplifying
-the RHS of an Id that's marked with an INLINE pragma. It is going to
-be inlined wherever they are used, and then all the inlining will take
-effect. Meanwhile, there isn't much point in doing anything to the
-as-yet-un-INLINEd rhs. Furthremore, it's very important to switch off
-inlining! because
- (a) not doing so will inline a worker straight back into its wrapper!
+---------------------
+getMode :: SimplEnv -> SimplifierMode
+getMode env = seMode env
-and (b) Consider the following example
- let f = \pq -> BIG
- in
- let g = \y -> f y y
- {-# INLINE g #-}
- in ...g...g...g...g...g...
+setMode :: SimplifierMode -> SimplEnv -> SimplEnv
+setMode mode env = env { seMode = mode }
- Now, if that's the ONLY occurrence of f, it will be inlined inside g,
- and thence copied multiple times when g is inlined.
+---------------------
+getEnclosingCC :: SimplEnv -> CostCentreStack
+getEnclosingCC env = seCC env
- Andy disagrees! Example:
- all xs = foldr (&&) True xs
- any p = all . map p {-# INLINE any #-}
-
- Problem: any won't get deforested, and so if it's exported and
- the importer doesn't use the inlining, (eg passes it as an arg)
- then we won't get deforestation at all.
- We havn't solved this problem yet!
-
-We prepare the envt by simply modifying the black list.
-
-6/98 update:
-
-We *don't* prevent inlining from happening for identifiers
-that are marked as IMustBeINLINEd. An example of where
-doing this is crucial is:
-
- class Bar a => Foo a where
- ...g....
- {-# INLINE f #-}
- f :: Foo a => a -> b
- f x = ....Foo_sc1...
-
-If `f' needs to peer inside Foo's superclass, Bar, it refers
-to the appropriate super class selector, which is marked as
-must-inlineable. We don't generate any code for a superclass
-selector, so failing to inline it in the RHS of `f' will
-leave a reference to a non-existent id, with bad consequences.
-
-ALSO NOTE that we do all this by modifing the black list
-not by zapping the unfolding. The latter may still be useful for
-knowing when something is evaluated.
+setEnclosingCC :: SimplEnv -> CostCentreStack -> SimplEnv
+setEnclosingCC env cc = env {seCC = cc}
-\begin{code}
-setBlackList :: BlackList -> SimplM a -> SimplM a
-setBlackList black_list m env us sc = m (env { seBlackList = black_list }) us sc
-
-getBlackList :: SimplM BlackList
-getBlackList env us sc = (seBlackList env, us, sc)
-
-noInlineBlackList :: BlackList
- -- Inside inlinings, black list anything that is in scope or imported.
- -- except for things that must be unfolded (Compulsory)
- -- and data con wrappers. The latter is a hack, like the one in
- -- SimplCore.simplRules, to make wrappers inline in rule LHSs.
- -- We may as well do the same here.
-noInlineBlackList v = not (isCompulsoryUnfolding (idUnfolding v)) &&
- not (isDataConWrapId v)
- -- ((v `isInScope` subst) || not (isLocallyDefined v))
- -- I don't see why we have these conditions
+---------------------
+getSubst :: SimplEnv -> Subst
+getSubst env = seSubst env
+
+setSubst :: SimplEnv -> Subst -> SimplEnv
+setSubst env subst = env {seSubst = subst}
+
+extendSubst :: SimplEnv -> CoreBndr -> SubstResult -> SimplEnv
+extendSubst env@(SimplEnv {seSubst = subst}) var res
+ = env {seSubst = Subst.extendSubst subst var res}
+
+extendSubstList :: SimplEnv -> [CoreBndr] -> [SubstResult] -> SimplEnv
+extendSubstList env@(SimplEnv {seSubst = subst}) vars ress
+ = env {seSubst = Subst.extendSubstList subst vars ress}
+
+---------------------
+getInScope :: SimplEnv -> InScopeSet
+getInScope env = substInScope (seSubst env)
+
+setInScope :: SimplEnv -> SimplEnv -> SimplEnv
+setInScope env env_with_in_scope = setInScopeSet env (getInScope env_with_in_scope)
+
+setInScopeSet :: SimplEnv -> InScopeSet -> SimplEnv
+setInScopeSet env@(SimplEnv {seSubst = subst}) in_scope
+ = env {seSubst = Subst.setInScope subst in_scope}
+
+addNewInScopeIds :: SimplEnv -> [CoreBndr] -> SimplEnv
+ -- The new Ids are guaranteed to be freshly allocated
+addNewInScopeIds env@(SimplEnv {seSubst = subst}) vs
+ = env {seSubst = Subst.extendNewInScopeList subst vs}
+
+modifyInScope :: SimplEnv -> CoreBndr -> CoreBndr -> SimplEnv
+modifyInScope env@(SimplEnv {seSubst = subst}) v v'
+ = env {seSubst = Subst.modifyInScope subst v v'}
+
+---------------------
+getSubstEnv :: SimplEnv -> SubstEnv
+getSubstEnv env = substEnv (seSubst env)
+
+setSubstEnv :: SimplEnv -> SubstEnv -> SimplEnv
+setSubstEnv env@(SimplEnv {seSubst = subst}) senv
+ = env {seSubst = Subst.setSubstEnv subst senv}
+
+zapSubstEnv :: SimplEnv -> SimplEnv
+zapSubstEnv env@(SimplEnv {seSubst = subst})
+ = env {seSubst = Subst.zapSubstEnv subst}
\end{code}
%************************************************************************
%* *
-\subsubsection{The ``enclosing cost-centre''}
+\subsection{Decisions about inlining}
%* *
%************************************************************************
+Inlining is controlled partly by the SimplifierMode switch. This has two
+settings:
+
+ SimplGently (a) Simplifying before specialiser/full laziness
+ (b) Simplifiying inside INLINE pragma
+ (c) Simplifying the LHS of a rule
+
+ SimplPhase n Used at all other times
+
+The key thing about SimplGently is that it does no call-site inlining.
+Before full laziness we must be careful not to inline wrappers,
+because doing so inhibits floating
+ e.g. ...(case f x of ...)...
+ ==> ...(case (case x of I# x# -> fw x#) of ...)...
+ ==> ...(case x of I# x# -> case fw x# of ...)...
+and now the redex (f x) isn't floatable any more.
+
+INLINE pragmas
+~~~~~~~~~~~~~~
+SimplGently is also used as the mode to simplify inside an InlineMe note.
+
\begin{code}
-getEnclosingCC :: SimplM CostCentreStack
-getEnclosingCC env us sc = (seCC env, us, sc)
+inlineMode :: SimplifierMode
+inlineMode = SimplGently
+\end{code}
-setEnclosingCC :: CostCentreStack -> SimplM a -> SimplM a
-setEnclosingCC cc m env us sc = m (env { seCC = cc }) us sc
+It really is important to switch off inlinings inside such
+expressions. Consider the following example
+
+ let f = \pq -> BIG
+ in
+ let g = \y -> f y y
+ {-# INLINE g #-}
+ in ...g...g...g...g...g...
+
+Now, if that's the ONLY occurrence of f, it will be inlined inside g,
+and thence copied multiple times when g is inlined.
+
+
+This function may be inlinined in other modules, so we
+don't want to remove (by inlining) calls to functions that have
+specialisations, or that may have transformation rules in an importing
+scope.
+
+E.g. {-# INLINE f #-}
+ f x = ...g...
+
+and suppose that g is strict *and* has specialisations. If we inline
+g's wrapper, we deny f the chance of getting the specialised version
+of g when f is inlined at some call site (perhaps in some other
+module).
+
+It's also important not to inline a worker back into a wrapper.
+A wrapper looks like
+ wraper = inline_me (\x -> ...worker... )
+Normally, the inline_me prevents the worker getting inlined into
+the wrapper (initially, the worker's only call site!). But,
+if the wrapper is sure to be called, the strictness analyser will
+mark it 'demanded', so when the RHS is simplified, it'll get an ArgOf
+continuation. That's why the keep_inline predicate returns True for
+ArgOf continuations. It shouldn't do any harm not to dissolve the
+inline-me note under these circumstances.
+
+Note that the result is that we do very little simplification
+inside an InlineMe.
+
+ all xs = foldr (&&) True xs
+ any p = all . map p {-# INLINE any #-}
+
+Problem: any won't get deforested, and so if it's exported and the
+importer doesn't use the inlining, (eg passes it as an arg) then we
+won't get deforestation at all. We havn't solved this problem yet!
+
+
+preInlineUnconditionally
+~~~~~~~~~~~~~~~~~~~~~~~~
+@preInlineUnconditionally@ examines a bndr to see if it is used just
+once in a completely safe way, so that it is safe to discard the
+binding inline its RHS at the (unique) usage site, REGARDLESS of how
+big the RHS might be. If this is the case we don't simplify the RHS
+first, but just inline it un-simplified.
+
+This is much better than first simplifying a perhaps-huge RHS and then
+inlining and re-simplifying it. Indeed, it can be at least quadratically
+better. Consider
+
+ x1 = e1
+ x2 = e2[x1]
+ x3 = e3[x2]
+ ...etc...
+ xN = eN[xN-1]
+
+We may end up simplifying e1 N times, e2 N-1 times, e3 N-3 times etc.
+
+NB: we don't even look at the RHS to see if it's trivial
+We might have
+ x = y
+where x is used many times, but this is the unique occurrence of y.
+We should NOT inline x at all its uses, because then we'd do the same
+for y -- aargh! So we must base this pre-rhs-simplification decision
+solely on x's occurrences, not on its rhs.
+
+Evne RHSs labelled InlineMe aren't caught here, because there might be
+no benefit from inlining at the call site.
+
+[Sept 01] Don't unconditionally inline a top-level thing, because that
+can simply make a static thing into something built dynamically. E.g.
+ x = (a,b)
+ main = \s -> h x
+
+[Remember that we treat \s as a one-shot lambda.] No point in
+inlining x unless there is something interesting about the call site.
+
+But watch out: if you aren't careful, some useful foldr/build fusion
+can be lost (most notably in spectral/hartel/parstof) because the
+foldr didn't see the build. Doing the dynamic allocation isn't a big
+deal, in fact, but losing the fusion can be. But the right thing here
+seems to be to do a callSiteInline based on the fact that there is
+something interesting about the call site (it's strict). Hmm. That
+seems a bit fragile.
+
+Conclusion: inline top level things gaily until Phase 0 (the last
+phase), at which point don't.
+
+\begin{code}
+preInlineUnconditionally :: SimplEnv -> TopLevelFlag -> InId -> Bool
+preInlineUnconditionally env top_lvl bndr
+ | isTopLevel top_lvl, SimplPhase 0 <- phase = False
+-- If we don't have this test, consider
+-- x = length [1,2,3]
+-- The full laziness pass carefully floats all the cons cells to
+-- top level, and preInlineUnconditionally floats them all back in.
+-- Result is (a) static allocation replaced by dynamic allocation
+-- (b) many simplifier iterations because this tickles
+-- a related problem; only one inlining per pass
+--
+-- On the other hand, I have seen cases where top-level fusion is
+-- lost if we don't inline top level thing (e.g. string constants)
+-- Hence the test for phase zero (which is the phase for all the final
+-- simplifications). Until phase zero we take no special notice of
+-- top level things, but then we become more leery about inlining
+-- them.
+
+ | not active = False
+ | opt_SimplNoPreInlining = False
+ | otherwise = case idOccInfo bndr of
+ IAmDead -> True -- Happens in ((\x.1) v)
+ OneOcc in_lam once -> not in_lam && once
+ -- Not inside a lambda, one occurrence ==> safe!
+ other -> False
+ where
+ phase = getMode env
+ active = case phase of
+ SimplGently -> isAlwaysActive prag
+ SimplPhase n -> isActive n prag
+ prag = idInlinePragma bndr
\end{code}
+postInlineUnconditionally
+~~~~~~~~~~~~~~~~~~~~~~~~~
+@postInlineUnconditionally@ decides whether to unconditionally inline
+a thing based on the form of its RHS; in particular if it has a
+trivial RHS. If so, we can inline and discard the binding altogether.
-%************************************************************************
-%* *
-\subsubsection{The @SimplEnv@ type}
-%* *
-%************************************************************************
+NB: a loop breaker has must_keep_binding = True and non-loop-breakers
+only have *forward* references Hence, it's safe to discard the binding
+
+NOTE: This isn't our last opportunity to inline. We're at the binding
+site right now, and we'll get another opportunity when we get to the
+ocurrence(s)
+Note that we do this unconditional inlining only for trival RHSs.
+Don't inline even WHNFs inside lambdas; doing so may simply increase
+allocation when the function is called. This isn't the last chance; see
+NOTE above.
-\begin{code}
-emptySimplEnv :: SwitchChecker -> VarSet -> (Id -> Bool) -> SimplEnv
+NB: Even inline pragmas (e.g. IMustBeINLINEd) are ignored here Why?
+Because we don't even want to inline them into the RHS of constructor
+arguments. See NOTE above
-emptySimplEnv sw_chkr in_scope black_list
- = SimplEnv { seChkr = sw_chkr, seCC = subsumedCCS,
- seBlackList = black_list,
- seSubst = mkSubst (mkInScopeSet in_scope) emptySubstEnv }
- -- The top level "enclosing CC" is "SUBSUMED".
+NB: At one time even NOINLINE was ignored here: if the rhs is trivial
+it's best to inline it anyway. We often get a=E; b=a from desugaring,
+with both a and b marked NOINLINE. But that seems incompatible with
+our new view that inlining is like a RULE, so I'm sticking to the 'active'
+story for now.
-getEnv :: SimplM SimplEnv
-getEnv env us sc = (env, us, sc)
+\begin{code}
+postInlineUnconditionally :: SimplEnv -> OutId -> OccInfo -> OutExpr -> Bool
+postInlineUnconditionally env bndr occ_info rhs
+ = exprIsTrivial rhs && active && isOneOcc occ_info
+ -- We used to have (not loop_breaker && not (isExportedId bndr))
+ -- instead of (isOneOcc occ_info). Indeed, you might suppose that
+ -- there is nothing wrong with substituting for a trivial RHS, even
+ -- if it occurs many times. But consider
+ -- x = y
+ -- h = _inline_me_ (...x...)
+ -- Here we do *not* want to have x inlined, even though the RHS is
+ -- trivial, becuase the contract for an INLINE pragma is "no inlining".
+ -- This is important in the rules for the Prelude (e.g. PrelEnum.eftInt).
+ where
+ active = case getMode env of
+ SimplGently -> isAlwaysActive prag
+ SimplPhase n -> isActive n prag
+ prag = idInlinePragma bndr
+\end{code}
-setAllExceptInScope :: SimplEnv -> SimplM a -> SimplM a
-setAllExceptInScope new_env@(SimplEnv {seSubst = new_subst}) m
- (SimplEnv {seSubst = old_subst}) us sc
- = m (new_env {seSubst = Subst.setInScope new_subst (substInScope old_subst)}) us sc
+blackListInline tells if we must not inline at a call site because the
+Id's inline pragma says not to do so.
-getSubst :: SimplM Subst
-getSubst env us sc = (seSubst env, us, sc)
+However, blackListInline is ignored for things with with Compulsory inlinings,
+because they don't have bindings, so we must inline them no matter how
+gentle we are being.
-setSubst :: Subst -> SimplM a -> SimplM a
-setSubst subst m env us sc = m (env {seSubst = subst}) us sc
+\begin{code}
+activeInline :: SimplEnv -> OutId -> OccInfo -> Bool
+activeInline env id occ
+ = case getMode env of
+ SimplGently -> isAlwaysActive prag && isOneOcc occ
+ -- No inlining at all when doing gentle stuff,
+ -- except for things that occur once
+ -- The reason is that too little clean-up happens if you
+ -- don't inline use-once things. Also a bit of inlining is *good* for
+ -- full laziness; it can expose constant sub-expressions.
+ -- Example in spectral/mandel/Mandel.hs, where the mandelset
+ -- function gets a useful let-float if you inline windowToViewport
+
+ -- NB: we used to have a second exception, for data con wrappers.
+ -- On the grounds that we use gentle mode for rule LHSs, and
+ -- they match better when data con wrappers are inlined.
+ -- But that only really applies to the trivial wrappers (like (:)),
+ -- and they are now constructed as Compulsory unfoldings (in MkId)
+ -- so they'll happen anyway.
+
+ SimplPhase n -> isActive n prag
+ where
+ prag = idInlinePragma id
-getSubstEnv :: SimplM SubstEnv
-getSubstEnv env us sc = (substEnv (seSubst env), us, sc)
+activeRule :: SimplEnv -> Maybe (Activation -> Bool)
+-- Nothing => No rules at all
+activeRule env
+ = case getMode env of
+ SimplGently -> Nothing -- No rules in gentle mode
+ SimplPhase n -> Just (isActive n)
+\end{code}
-addNewInScopeIds :: [CoreBndr] -> SimplM a -> SimplM a
- -- The new Ids are guaranteed to be freshly allocated
-addNewInScopeIds vs m env@(SimplEnv {seSubst = subst}) us sc
- = m (env {seSubst = Subst.extendNewInScopeList subst vs}) us sc
-getInScope :: SimplM InScopeSet
-getInScope env us sc = (substInScope (seSubst env), us, sc)
+%************************************************************************
+%* *
+\subsubsection{Command-line switches}
+%* *
+%************************************************************************
-setInScope :: InScopeSet -> SimplM a -> SimplM a
-setInScope in_scope m env@(SimplEnv {seSubst = subst}) us sc
- = m (env {seSubst = Subst.setInScope subst in_scope}) us sc
+\begin{code}
+getSimplIntSwitch :: SwitchChecker -> (Int-> SimplifierSwitch) -> Int
+getSimplIntSwitch chkr switch
+ = expectJust "getSimplIntSwitch" (intSwitchSet chkr switch)
-modifyInScope :: CoreBndr -> CoreBndr -> SimplM a -> SimplM a
-modifyInScope v v' m env@(SimplEnv {seSubst = subst}) us sc
- = m (env {seSubst = Subst.modifyInScope subst v v'}) us sc
+switchIsOn :: (switch -> SwitchResult) -> switch -> Bool
-extendSubst :: CoreBndr -> SubstResult -> SimplM a -> SimplM a
-extendSubst var res m env@(SimplEnv {seSubst = subst}) us sc
- = m (env { seSubst = Subst.extendSubst subst var res }) us sc
+switchIsOn lookup_fn switch
+ = case (lookup_fn switch) of
+ SwBool False -> False
+ _ -> True
-extendSubstList :: [CoreBndr] -> [SubstResult] -> SimplM a -> SimplM a
-extendSubstList vars ress m env@(SimplEnv {seSubst = subst}) us sc
- = m (env { seSubst = Subst.extendSubstList subst vars ress }) us sc
+intSwitchSet :: (switch -> SwitchResult)
+ -> (Int -> switch)
+ -> Maybe Int
-setSubstEnv :: SubstEnv -> SimplM a -> SimplM a
-setSubstEnv senv m env@(SimplEnv {seSubst = subst}) us sc
- = m (env {seSubst = Subst.setSubstEnv subst senv}) us sc
+intSwitchSet lookup_fn switch
+ = case (lookup_fn (switch (panic "intSwitchSet"))) of
+ SwInt int -> Just int
+ _ -> Nothing
+\end{code}
-zapSubstEnv :: SimplM a -> SimplM a
-zapSubstEnv m env@(SimplEnv {seSubst = subst}) us sc
- = m (env {seSubst = Subst.zapSubstEnv subst}) us sc
-getSimplBinderStuff :: SimplM (Subst, UniqSupply)
-getSimplBinderStuff (SimplEnv {seSubst = subst}) us sc
- = ((subst, us), us, sc)
+\begin{code}
+type SwitchChecker = SimplifierSwitch -> SwitchResult
-setSimplBinderStuff :: (Subst, UniqSupply) -> SimplM a -> SimplM a
-setSimplBinderStuff (subst, us) m env _ sc
- = m (env {seSubst = subst}) us sc
+data SwitchResult
+ = SwBool Bool -- on/off
+ | SwString FAST_STRING -- nothing or a String
+ | SwInt Int -- nothing or an Int
+
+isAmongSimpl :: [SimplifierSwitch] -> SimplifierSwitch -> SwitchResult
+isAmongSimpl on_switches -- Switches mentioned later occur *earlier*
+ -- in the list; defaults right at the end.
+ = let
+ tidied_on_switches = foldl rm_dups [] on_switches
+ -- The fold*l* ensures that we keep the latest switches;
+ -- ie the ones that occur earliest in the list.
+
+ sw_tbl :: Array Int SwitchResult
+ sw_tbl = (array (0, lAST_SIMPL_SWITCH_TAG) -- bounds...
+ all_undefined)
+ // defined_elems
+
+ all_undefined = [ (i, SwBool False) | i <- [0 .. lAST_SIMPL_SWITCH_TAG ] ]
+
+ defined_elems = map mk_assoc_elem tidied_on_switches
+ in
+ -- (avoid some unboxing, bounds checking, and other horrible things:)
+#if __GLASGOW_HASKELL__ < 405
+ case sw_tbl of { Array bounds_who_needs_'em stuff ->
+#else
+ case sw_tbl of { Array _ _ stuff ->
+#endif
+ \ switch ->
+ case (indexArray# stuff (tagOf_SimplSwitch switch)) of
+#if __GLASGOW_HASKELL__ < 400
+ Lift v -> v
+#elif __GLASGOW_HASKELL__ < 403
+ (# _, v #) -> v
+#else
+ (# v #) -> v
+#endif
+ }
+ where
+ mk_assoc_elem k@(MaxSimplifierIterations lvl)
+ = (iBox (tagOf_SimplSwitch k), SwInt lvl)
+ mk_assoc_elem k
+ = (iBox (tagOf_SimplSwitch k), SwBool True) -- I'm here, Mom!
+
+ -- cannot have duplicates if we are going to use the array thing
+ rm_dups switches_so_far switch
+ = if switch `is_elem` switches_so_far
+ then switches_so_far
+ else switch : switches_so_far
+ where
+ sw `is_elem` [] = False
+ sw `is_elem` (s:ss) = (tagOf_SimplSwitch sw) ==# (tagOf_SimplSwitch s)
+ || sw `is_elem` ss
\end{code}
+These things behave just like enumeration types.
\begin{code}
-newId :: UserFS -> Type -> (Id -> SimplM a) -> SimplM a
- -- Extends the in-scope-env too
-newId fs ty m env@(SimplEnv {seSubst = subst}) us sc
- = case splitUniqSupply us of
- (us1, us2) -> m v (env {seSubst = Subst.extendNewInScope subst v}) us2 sc
- where
- v = mkSysLocal fs (uniqFromSupply us1) ty
-
-newIds :: UserFS -> [Type] -> ([Id] -> SimplM a) -> SimplM a
-newIds fs tys m env@(SimplEnv {seSubst = subst}) us sc
- = case splitUniqSupply us of
- (us1, us2) -> m vs (env {seSubst = Subst.extendNewInScopeList subst vs}) us2 sc
- where
- vs = zipWithEqual "newIds" (mkSysLocal fs)
- (uniqsFromSupply (length tys) us1) tys
+instance Eq SimplifierSwitch where
+ a == b = tagOf_SimplSwitch a ==# tagOf_SimplSwitch b
+
+instance Ord SimplifierSwitch where
+ a < b = tagOf_SimplSwitch a <# tagOf_SimplSwitch b
+ a <= b = tagOf_SimplSwitch a <=# tagOf_SimplSwitch b
+
+
+tagOf_SimplSwitch (MaxSimplifierIterations _) = _ILIT(1)
+tagOf_SimplSwitch NoCaseOfCase = _ILIT(2)
+
+-- If you add anything here, be sure to change lAST_SIMPL_SWITCH_TAG, too!
+
+lAST_SIMPL_SWITCH_TAG = 2
\end{code}
+
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