\begin{code}
module SimplMonad (
InId, InBind, InExpr, InAlt, InArg, InType, InBinder,
- OutId, OutBind, OutExpr, OutAlt, OutArg, OutType, OutBinder,
- OutExprStuff, OutStuff, returnOutStuff,
+ OutId, OutTyVar, OutBind, OutExpr, OutAlt, OutArg, OutType, OutBinder,
+ FloatsWith, FloatsWithExpr,
-- The monad
SimplM,
mapSmpl, mapAndUnzipSmpl, mapAccumLSmpl,
getDOptsSmpl,
- -- The inlining black-list
- setBlackList, getBlackList, noInlineBlackList,
+ -- The simplifier mode
+ setMode, getMode,
-- Unique supply
getUniqueSmpl, getUniquesSmpl, getUniqSupplySmpl,
- newId, newIds,
-- 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,
- -- Adding bindings
- addLetBind, addLetBinds, addAuxiliaryBind, addAuxiliaryBinds,
- addCaseBind, needsCaseBinding, addNonRecBind, wrapFloats, addFloats
+ -- 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, idType, idUnfolding, isDataConWrapId,
- isGlobalId )
+import Id ( Id, idType, isDataConWrapId,
+ idOccInfo, idInlinePragma
+ )
import CoreSyn
-import CoreUnfold ( isCompulsoryUnfolding )
-import CoreUtils ( exprOkForSpeculation )
+import CoreUtils ( needsCaseBinding, exprIsTrivial )
import PprCore () -- Instances
import CostCentre ( CostCentreStack, subsumedCCS )
-import OccName ( UserFS )
+import Var
import VarEnv
import VarSet
import OrdList
UniqSupply
)
import FiniteMap
-import CmdLineOpts ( SimplifierSwitch(..), SwitchResult(..),
- DynFlags, DynFlag(..), dopt,
- opt_PprStyle_Debug, opt_HistorySize,
- intSwitchSet
+import BasicTypes ( TopLevelFlag, isTopLevel,
+ Activation, isActive, isAlwaysActive,
+ OccInfo(..)
+ )
+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__ < 301
+import ArrBase ( Array(..) )
+#else
+import PrelArr ( 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 OutExpr
-type OutStuff a = (OrdList OutBind, (InScopeSet, 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}
-wrapFloats :: OrdList CoreBind -> CoreExpr -> CoreExpr
-wrapFloats binds body = foldOL Let body binds
-
-returnOutStuff :: a -> SimplM (OutStuff a)
-returnOutStuff x = getInScope `thenSmpl` \ in_scope ->
- returnSmpl (nilOL, (in_scope, x))
-
-addFloats :: OrdList CoreBind -> InScopeSet -> SimplM (OutStuff a) -> SimplM (OutStuff a)
-addFloats floats in_scope thing_inside
- = setInScope in_scope thing_inside `thenSmpl` \ (binds, res) ->
- returnSmpl (floats `appOL` binds, res)
-
-addLetBind :: CoreBind -> SimplM (OutStuff a) -> SimplM (OutStuff a)
-addLetBind bind thing_inside
- = thing_inside `thenSmpl` \ (binds, res) ->
- returnSmpl (bind `consOL` binds, res)
-
-addLetBinds :: [CoreBind] -> SimplM (OutStuff a) -> SimplM (OutStuff a)
-addLetBinds binds1 thing_inside
- = thing_inside `thenSmpl` \ (binds2, res) ->
- returnSmpl (toOL binds1 `appOL` binds2, res)
-
-addAuxiliaryBinds :: [CoreBind] -> SimplM (OutStuff a) -> SimplM (OutStuff a)
- -- Extends the in-scope environment as well as wrapping the bindings
-addAuxiliaryBinds binds1 thing_inside
- = addNewInScopeIds (bindersOfBinds binds1) $
- addLetBinds binds1 thing_inside
-
-addAuxiliaryBind :: CoreBind -> SimplM (OutStuff a) -> SimplM (OutStuff a)
+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 bind thing_inside
- = addNewInScopeIds (bindersOf bind) $
- addLetBind bind thing_inside
-
-needsCaseBinding ty rhs = isUnLiftedType ty && not (exprOkForSpeculation rhs)
- -- Make a case expression instead of a let
- -- These can arise either from the desugarer,
- -- or from beta reductions: (\x.e) (x +# y)
-
-addCaseBind bndr rhs thing_inside
- = thing_inside `thenSmpl` \ (floats, (_, body)) ->
- returnOutStuff (Case rhs bndr [(DEFAULT, [], wrapFloats floats body)])
-
-addNonRecBind bndr rhs thing_inside
- -- Checks for needing a case binding
- | needsCaseBinding (idType bndr) rhs = addCaseBind bndr rhs thing_inside
- | otherwise = addLetBind (NonRec bndr rhs) thing_inside
+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}
\begin{code}
type SimplM result
- = DynFlags
- -> SimplEnv -- We thread the unique supply because
+ = 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 :: DynFlags
- -> SwitchChecker
-> 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 dflags chkr us in_scope black_list m
- = case m dflags (emptySimplEnv chkr in_scope black_list) us
- (zeroSimplCount dflags) of
+initSmpl dflags us m
+ = case m dflags us (zeroSimplCount dflags) of
(result, _, count) -> (result, count)
{-# INLINE returnSmpl #-}
returnSmpl :: a -> SimplM a
-returnSmpl e dflags 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 dflags env us0 sc0
- = case (m dflags env us0 sc0) of
- (m_result, us1, sc1) -> k m_result dflags 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 dflags env us0 sc0
- = case (m dflags env us0 sc0) of
- (_, us1, sc1) -> k dflags 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}
getUniqSupplySmpl :: SimplM UniqSupply
-getUniqSupplySmpl dflags env us sc
+getUniqSupplySmpl dflags us sc
= case splitUniqSupply us of
(us1, us2) -> (us1, us2, sc)
getUniqueSmpl :: SimplM Unique
-getUniqueSmpl dflags env us sc
+getUniqueSmpl dflags us sc
= case splitUniqSupply us of
(us1, us2) -> (uniqFromSupply us1, us2, sc)
getUniquesSmpl :: SimplM [Unique]
-getUniquesSmpl dflags env us sc
+getUniquesSmpl dflags us sc
= case splitUniqSupply us of
(us1, us2) -> (uniqsFromSupply us1, us2, sc)
getDOptsSmpl :: SimplM DynFlags
-getDOptsSmpl dflags env us sc
+getDOptsSmpl dflags us sc
= (dflags, us, sc)
\end{code}
\begin{code}
getSimplCount :: SimplM SimplCount
-getSimplCount dflags env us sc = (sc, us, sc)
+getSimplCount dflags us sc = (sc, us, sc)
tick :: Tick -> SimplM ()
-tick t dflags env us 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 dflags env us sc
+freeTick t dflags us sc
= sc' `seq` ((), us, sc')
where
sc' = doFreeTick t sc
| 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 (FillInCaseDefault _) = 13
tickToTag BottomFound = 14
tickToTag SimplifierDone = 16
+tickToTag (AltMerge _) = 17
tickString :: Tick -> String
tickString (PreInlineUnconditionally _) = "PreInlineUnconditionally"
tickString (CaseOfCase _) = "CaseOfCase"
tickString (KnownBranch _) = "KnownBranch"
tickString (CaseMerge _) = "CaseMerge"
+tickString (AltMerge _) = "AltMerge"
tickString (CaseElim _) = "CaseElim"
tickString (CaseIdentity _) = "CaseIdentity"
tickString (FillInCaseDefault _) = "FillInCaseDefault"
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 (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 dflags 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".
-@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!
+---------------------
+getSwitchChecker :: SimplEnv -> SwitchChecker
+getSwitchChecker env = seChkr 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...
+---------------------
+getMode :: SimplEnv -> SimplifierMode
+getMode env = seMode env
- Now, if that's the ONLY occurrence of f, it will be inlined inside g,
- and thence copied multiple times when g is inlined.
+setMode :: SimplifierMode -> SimplEnv -> SimplEnv
+setMode mode env = env { seMode = mode }
- 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.
+---------------------
+getEnclosingCC :: SimplEnv -> CostCentreStack
+getEnclosingCC env = seCC env
-\begin{code}
-setBlackList :: BlackList -> SimplM a -> SimplM a
-setBlackList black_list m dflags env us sc
- = m dflags (env { seBlackList = black_list }) us sc
-
-getBlackList :: SimplM BlackList
-getBlackList dflags env us sc = (seBlackList env, us, sc)
-
-noInlineBlackList :: SimplM BlackList
- -- Inside inlinings, black list anything that is in scope or imported.
- -- except for data con wrappers. The exception 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 dflags env us sc = (blacklisted,us,sc)
- where blacklisted v =
- not (isDataConWrapId v) &&
- (v `isInScope` (seSubst env) || isGlobalId v)
- -- NB: An earlier version omitted the last clause; this meant
- -- that even inlinings *completely within* an INLINE didn't happen.
- -- This was cheaper, and probably adequate, but produced awful code
- -- for some dictionary constructions.
-\end{code}
+setEnclosingCC :: SimplEnv -> CostCentreStack -> SimplEnv
+setEnclosingCC env cc = env {seCC = cc}
+---------------------
+getSubst :: SimplEnv -> Subst
+getSubst env = seSubst env
-%************************************************************************
-%* *
-\subsubsection{The ``enclosing cost-centre''}
-%* *
-%************************************************************************
+setSubst :: SimplEnv -> Subst -> SimplEnv
+setSubst env subst = env {seSubst = subst}
-\begin{code}
-getEnclosingCC :: SimplM CostCentreStack
-getEnclosingCC dflags env us sc = (seCC env, us, sc)
+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}
-setEnclosingCC :: CostCentreStack -> SimplM a -> SimplM a
-setEnclosingCC cc m dflags env us sc = m dflags (env { seCC = cc }) us sc
+---------------------
+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 @SimplEnv@ type}
+\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}
-emptySimplEnv :: SwitchChecker -> VarSet -> (Id -> Bool) -> SimplEnv
+inlineMode :: SimplifierMode
+inlineMode = SimplGently
+\end{code}
-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".
+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.
+
+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.
-getEnv :: SimplM SimplEnv
-getEnv dflags env us sc = (env, us, sc)
+\begin{code}
+preInlineUnconditionally :: SimplEnv -> TopLevelFlag -> InId -> Bool
+preInlineUnconditionally env top_lvl bndr
+-- | isTopLevel top_lvl = False
+-- Top-level fusion lost if we do this for (e.g. string constants)
+ | 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
+ 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 dflags
- (SimplEnv {seSubst = old_subst}) us sc
- = m dflags (new_env {seSubst = Subst.setInScope new_subst (substInScope old_subst)})
- us sc
+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.
-getSubst :: SimplM Subst
-getSubst dflags env us sc = (seSubst env, us, sc)
+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)
-setSubst :: Subst -> SimplM a -> SimplM a
-setSubst subst m dflags env us sc = m dflags (env {seSubst = subst}) us sc
+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.
-getSubstEnv :: SimplM SubstEnv
-getSubstEnv dflags env us sc = (substEnv (seSubst env), us, sc)
+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
-addNewInScopeIds :: [CoreBndr] -> SimplM a -> SimplM a
- -- The new Ids are guaranteed to be freshly allocated
-addNewInScopeIds vs m dflags env@(SimplEnv {seSubst = subst}) us sc
- = m dflags (env {seSubst = Subst.extendNewInScopeList subst vs}) us sc
+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.
-getInScope :: SimplM InScopeSet
-getInScope dflags env us sc = (substInScope (seSubst env), us, sc)
+\begin{code}
+postInlineUnconditionally :: SimplEnv -> OutId -> Bool -> OutExpr -> Bool
+postInlineUnconditionally env bndr loop_breaker rhs
+ = exprIsTrivial rhs
+ && active
+ && not loop_breaker
+ && not (isExportedId bndr)
+ where
+ active = case getMode env of
+ SimplGently -> isAlwaysActive prag
+ SimplPhase n -> isActive n prag
+ prag = idInlinePragma bndr
+\end{code}
-setInScope :: InScopeSet -> SimplM a -> SimplM a
-setInScope in_scope m dflags env@(SimplEnv {seSubst = subst}) us sc
- = m dflags (env {seSubst = Subst.setInScope subst in_scope}) us sc
+blackListInline tells if we must not inline at a call site because the
+Id's inline pragma says not to do so.
-modifyInScope :: CoreBndr -> CoreBndr -> SimplM a -> SimplM a
-modifyInScope v v' m dflags env@(SimplEnv {seSubst = subst}) us sc
- = m dflags (env {seSubst = Subst.modifyInScope subst v v'}) 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.
-extendSubst :: CoreBndr -> SubstResult -> SimplM a -> SimplM a
-extendSubst var res m dflags env@(SimplEnv {seSubst = subst}) us sc
- = m dflags (env { seSubst = Subst.extendSubst subst var res }) us sc
+\begin{code}
+activeInline :: SimplEnv -> OutId -> Bool
+activeInline env id
+ = case getMode env of
+ SimplGently -> isDataConWrapId id
+ -- No inlining at all when doing gentle stuff,
+ -- except (hack alert) for data con wrappers
+ -- We want to inline data con wrappers even in gentle mode
+ -- because rule LHSs match better then
+ SimplPhase n -> isActive n (idInlinePragma id)
+
+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}
-extendSubstList :: [CoreBndr] -> [SubstResult] -> SimplM a -> SimplM a
-extendSubstList vars ress m dflags env@(SimplEnv {seSubst = subst}) us sc
- = m dflags (env { seSubst = Subst.extendSubstList subst vars ress }) us sc
-setSubstEnv :: SubstEnv -> SimplM a -> SimplM a
-setSubstEnv senv m dflags env@(SimplEnv {seSubst = subst}) us sc
- = m dflags (env {seSubst = Subst.setSubstEnv subst senv}) us sc
+%************************************************************************
+%* *
+\subsubsection{Command-line switches}
+%* *
+%************************************************************************
-zapSubstEnv :: SimplM a -> SimplM a
-zapSubstEnv m dflags env@(SimplEnv {seSubst = subst}) us sc
- = m dflags (env {seSubst = Subst.zapSubstEnv subst}) us sc
+\begin{code}
+getSimplIntSwitch :: SwitchChecker -> (Int-> SimplifierSwitch) -> Int
+getSimplIntSwitch chkr switch
+ = expectJust "getSimplIntSwitch" (intSwitchSet chkr switch)
-getSimplBinderStuff :: SimplM (Subst, UniqSupply)
-getSimplBinderStuff dflags (SimplEnv {seSubst = subst}) us sc
- = ((subst, us), us, sc)
+switchIsOn :: (switch -> SwitchResult) -> switch -> Bool
-setSimplBinderStuff :: (Subst, UniqSupply) -> SimplM a -> SimplM a
-setSimplBinderStuff (subst, us) m dflags env _ sc
- = m dflags (env {seSubst = subst}) us sc
+switchIsOn lookup_fn switch
+ = case (lookup_fn switch) of
+ SwBool False -> False
+ _ -> True
+
+intSwitchSet :: (switch -> SwitchResult)
+ -> (Int -> switch)
+ -> Maybe Int
+
+intSwitchSet lookup_fn switch
+ = case (lookup_fn (switch (panic "intSwitchSet"))) of
+ SwInt int -> Just int
+ _ -> Nothing
+\end{code}
+
+
+\begin{code}
+type SwitchChecker = SimplifierSwitch -> SwitchResult
+
+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 dflags env@(SimplEnv {seSubst = subst}) us sc
- = case splitUniqSupply us of
- (us1, us2) -> m v dflags (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 dflags env@(SimplEnv {seSubst = subst}) us sc
- = case splitUniqSupply us of
- (us1, us2) -> m vs dflags (env {seSubst = Subst.extendNewInScopeList subst vs})
- us2 sc
- where
- vs = zipWith (mkSysLocal fs) (uniqsFromSupply 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}
+
projects / ghc-hetmet.git / blobdiff