%
-% (c) The AQUA Project, Glasgow University, 1993-1995
+% (c) The AQUA Project, Glasgow University, 1993-1998
%
\section[SimplMonad]{The simplifier Monad}
\begin{code}
-#include "HsVersions.h"
-
module SimplMonad (
- SmplM(..),
+ InId, InBind, InExpr, InAlt, InArg, InType, InBinder,
+ OutId, OutBind, OutExpr, OutAlt, OutArg, OutType, OutBinder,
+
+ -- The continuation type
+ SimplCont(..), DupFlag(..), contIsDupable,
+
+ -- The monad
+ SimplM,
initSmpl, returnSmpl, thenSmpl, thenSmpl_,
- mapSmpl, mapAndUnzipSmpl,
-
+ mapSmpl, mapAndUnzipSmpl, mapAccumLSmpl,
+
+ -- Unique supply
+ getUniqueSmpl, getUniquesSmpl,
+ newId, newIds,
+
-- Counting
- SimplCount{-abstract-}, TickType(..), tick, tickN,
- simplCount, detailedSimplCount,
- zeroSimplCount, showSimplCount, combineSimplCounts,
+ SimplCount, TickType(..), TickCounts,
+ tick, tickUnfold,
+ getSimplCount, zeroSimplCount, pprSimplCount,
+ plusSimplCount, isZeroSimplCount,
+
+ -- Switch checker
+ SwitchChecker, getSwitchChecker, getSimplIntSwitch,
+
+ -- Cost centres
+ getEnclosingCC, setEnclosingCC,
+
+ -- Environments
+ InScopeEnv, SubstEnv,
+ getInScope, setInScope, extendInScope, extendInScopes, modifyInScope,
+ emptySubstEnv, getSubstEnv, setSubstEnv, zapSubstEnv,
+ extendIdSubst, extendTySubst,
+ getTyEnv, getValEnv,
+ getSimplBinderStuff, setSimplBinderStuff,
+ switchOffInlining
+ ) where
- -- Cloning
- cloneId, cloneIds, cloneTyVarSmpl, newIds, newId,
+#include "HsVersions.h"
- -- and to make the interface self-sufficient...
- BinderInfo, CoreExpr, Id, PrimOp, TyVar, UniType,
- SplitUniqSupply
+import Id ( Id, mkSysLocal, idMustBeINLINEd )
+import IdInfo ( InlinePragInfo(..) )
+import CoreSyn
+import CoreUtils ( IdSubst, SubstCoreExpr )
+import CostCentre ( CostCentreStack, subsumedCCS )
+import Var ( TyVar )
+import VarEnv
+import VarSet
+import Type ( Type, TyVarSubst )
+import UniqSupply ( uniqsFromSupply, uniqFromSupply, splitUniqSupply,
+ UniqSupply
+ )
+import CmdLineOpts ( SimplifierSwitch(..), SwitchResult(..), intSwitchSet )
+import Unique ( Unique )
+import Maybes ( expectJust )
+import Util ( zipWithEqual )
+import Outputable
- IF_ATTACK_PRAGMAS(COMMA splitUniqSupply)
- ) where
+infixr 9 `thenSmpl`, `thenSmpl_`
+\end{code}
+
+%************************************************************************
+%* *
+\subsection[Simplify-types]{Type declarations}
+%* *
+%************************************************************************
-IMPORT_Trace -- ToDo: rm (debugging)
+\begin{code}
+type InBinder = CoreBndr
+type InId = Id -- Not yet cloned
+type InType = Type -- Ditto
+type InBind = CoreBind
+type InExpr = CoreExpr
+type InAlt = CoreAlt
+type InArg = CoreArg
+
+type OutBinder = CoreBndr
+type OutId = Id -- Cloned
+type OutType = Type -- Cloned
+type OutBind = CoreBind
+type OutExpr = CoreExpr
+type OutAlt = CoreAlt
+type OutArg = CoreArg
+
+type SwitchChecker = SimplifierSwitch -> SwitchResult
+\end{code}
-import TaggedCore
-import PlainCore
-import AbsUniType ( cloneTyVar )
-import CmdLineOpts
-import Id ( mkIdWithNewUniq, mkSysLocal )
-import IdInfo
-import SimplEnv
-import SrcLoc ( mkUnknownSrcLoc, SrcLoc )
-import SplitUniq
-import Unique
-import Util
+%************************************************************************
+%* *
+\subsection{The continuation data type}
+%* *
+%************************************************************************
-infixr 9 `thenSmpl`, `thenSmpl_`
+\begin{code}
+data SimplCont
+ = Stop
+
+ | CoerceIt DupFlag
+ InType SubstEnv
+ SimplCont
+
+ | ApplyTo DupFlag
+ InExpr SubstEnv -- The argument, as yet unsimplified,
+ SimplCont -- and its subst-env
+
+ | Select DupFlag
+ InId [InAlt] SubstEnv -- The case binder, alts, and subst-env
+ SimplCont
+
+instance Outputable SimplCont where
+ ppr Stop = ptext SLIT("Stop")
+ ppr (ApplyTo dup arg se cont) = (ptext SLIT("ApplyTo") <+> ppr dup <+> ppr arg) $$ ppr cont
+ ppr (Select dup bndr alts se cont) = (ptext SLIT("Select") <+> ppr dup <+> ppr bndr) $$
+ (nest 4 (ppr alts)) $$ ppr cont
+ ppr (CoerceIt dup ty se cont) = (ptext SLIT("CoerceIt") <+> ppr dup <+> ppr ty) $$ ppr cont
+
+data DupFlag = OkToDup | NoDup
+
+instance Outputable DupFlag where
+ ppr OkToDup = ptext SLIT("ok")
+ ppr NoDup = ptext SLIT("nodup")
+
+contIsDupable :: SimplCont -> Bool
+contIsDupable Stop = True
+contIsDupable (ApplyTo OkToDup _ _ _) = True
+contIsDupable (Select OkToDup _ _ _ _) = True
+contIsDupable (CoerceIt OkToDup _ _ _) = True
+contIsDupable other = False
\end{code}
+
%************************************************************************
%* *
-\subsection[Monad]{Monad plumbing}
+\subsection{Monad plumbing}
%* *
%************************************************************************
(Command-line switches move around through the explicitly-passed SimplEnv.)
\begin{code}
-type SmplM result
- = SplitUniqSupply
- -> SimplCount -- things being threaded
- -> (result, SimplCount)
+type SimplM result -- We thread the unique supply because
+ = SimplEnv -- constantly splitting it is rather expensive
+ -> UniqSupply
+ -> SimplCount
+ -> (result, UniqSupply, SimplCount)
+
+data SimplEnv
+ = SimplEnv {
+ seChkr :: SwitchChecker,
+ seCC :: CostCentreStack, -- The enclosing CCS (when profiling)
+ seSubst :: SubstEnv, -- The current substitution
+ seInScope :: InScopeEnv -- Says what's in scope and gives info about it
+ }
\end{code}
\begin{code}
-initSmpl :: SplitUniqSupply -- no init count; set to 0
- -> SmplM a
- -> (a, SimplCount)
+initSmpl :: SwitchChecker
+ -> UniqSupply -- No init count; set to 0
+ -> SimplM a
+ -> (a, SimplCount)
+
+initSmpl chkr us m = case m (emptySimplEnv chkr) us zeroSimplCount of
+ (result, _, count) -> (result, count)
-initSmpl us m = m us zeroSimplCount
-#ifdef __GLASGOW_HASKELL__
{-# INLINE thenSmpl #-}
{-# INLINE thenSmpl_ #-}
{-# INLINE returnSmpl #-}
-#endif
-returnSmpl :: a -> SmplM a
-returnSmpl e us sc = (e, sc)
+returnSmpl :: a -> SimplM a
+returnSmpl e env us sc = (e, us, sc)
-thenSmpl :: SmplM a -> (a -> SmplM b) -> SmplM b
-thenSmpl_ :: SmplM a -> SmplM b -> SmplM b
+thenSmpl :: SimplM a -> (a -> SimplM b) -> SimplM b
+thenSmpl_ :: SimplM a -> SimplM b -> SimplM b
-thenSmpl m k us sc0
- = case splitUniqSupply us of { (s1, s2) ->
- case (m s1 sc0) of { (m_result, sc1) ->
- k m_result s2 sc1 }}
+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 env us0 sc0
+ = case (m env us0 sc0) of
+ (_, us1, sc1) -> k env us1 sc1
+\end{code}
-thenSmpl_ m k us sc0
- = case splitUniqSupply us of { (s1, s2) ->
- case (m s1 sc0) of { (_, sc1) ->
- k s2 sc1 }}
-mapSmpl :: (a -> SmplM b) -> [a] -> SmplM [b]
-mapAndUnzipSmpl :: (a -> SmplM (b, c)) -> [a] -> SmplM ([b],[c])
+\begin{code}
+mapSmpl :: (a -> SimplM b) -> [a] -> SimplM [b]
+mapAndUnzipSmpl :: (a -> SimplM (b, c)) -> [a] -> SimplM ([b],[c])
mapSmpl f [] = returnSmpl []
mapSmpl f (x:xs)
= f x `thenSmpl` \ (r1, r2) ->
mapAndUnzipSmpl f xs `thenSmpl` \ (rs1, rs2) ->
returnSmpl (r1:rs1, r2:rs2)
+
+mapAccumLSmpl f acc [] = returnSmpl (acc, [])
+mapAccumLSmpl f acc (x:xs) = f acc x `thenSmpl` \ (acc', x') ->
+ mapAccumLSmpl f acc' xs `thenSmpl` \ (acc'', xs') ->
+ returnSmpl (acc'', x':xs')
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsection{The unique supply}
+%* *
+%************************************************************************
+
+\begin{code}
+getUniqueSmpl :: SimplM Unique
+getUniqueSmpl env us sc = case splitUniqSupply us of
+ (us1, us2) -> (uniqFromSupply us1, us2, sc)
+
+getUniquesSmpl :: Int -> SimplM [Unique]
+getUniquesSmpl n env us sc = case splitUniqSupply us of
+ (us1, us2) -> (uniqsFromSupply n us1, us2, sc)
\end{code}
%************************************************************************
%* *
-\subsection[SimplCount]{Counting up what we've done}
+\subsection{Counting up what we've done}
%* *
%************************************************************************
+\begin{code}
+doTickSmpl :: (SimplCount -> SimplCount) -> SimplM ()
+doTickSmpl f env us sc = sc' `seq` ((), us, sc')
+ where
+ sc' = f sc
+
+getSimplCount :: SimplM SimplCount
+getSimplCount env us sc = (sc, us, sc)
+\end{code}
+
+
The assoc list isn't particularly costly, because we only use
the number of ticks in ``real life.''
\begin{code}
data SimplCount
- = SimplCount FAST_INT -- number of ticks
- [(TickType, Int)] -- assoc list of all diff kinds of ticks
+ = SimplCount !TickCounts
+ !UnfoldingHistory
+
+type TickCounts = [(TickType, Int)] -- Assoc list of all diff kinds of ticks
+ -- Kept in increasing order of TickType
+ -- Zeros not present
+
+type UnfoldingHistory = (Int, -- N
+ [Id], -- Last N unfoldings
+ [Id]) -- The MaxUnfoldHistory unfoldings before that
data TickType
- = UnfoldingDone {-UNUSED: | Unused -}
- | FoldrBuild | MagicUnfold | ConReused
- | CaseFloatFromLet | CaseOfCase {-UNUSED: | CaseFloatFromApp -}
- | LetFloatFromLet | LetFloatFromCase {-UNUSED: | LetFloatFromApp -}
- | KnownBranch | Let2Case {-UNUSED: | UnboxingLet2Case -}
- | CaseMerge {-UNUSED: | CaseToLet-} | CaseElim
+ = PreInlineUnconditionally
+ | PostInlineUnconditionally
+ | UnfoldingDone
+ | MagicUnfold
+ | CaseOfCase
+ | LetFloatFromLet
+ | KnownBranch
+ | Let2Case
+ | Case2Let
+ | CaseMerge
+ | CaseElim
| CaseIdentity
- | AtomicRhs -- Rhs of a let-expression was an atom
- | EtaExpansion {-UNUSED: | ArityExpand-}
- {-UNUSED: | ConstantFolding-} | CaseOfError {-UNUSED: | InlineRemoved -}
- | FoldrConsNil
- | Foldr_Nil
- | FoldrFoldr
- | Foldr_List
- | FoldrCons
- | FoldrInline
- | TyBetaReduction
+ | EtaExpansion
+ | CaseOfError
| BetaReduction
- deriving (Eq, Ord, Ix)
-
-instance Text TickType where
- showsPrec p UnfoldingDone = showString "UnfoldingDone "
---UNUSED: showsPrec p Unused = showString "Unused "
- showsPrec p FoldrBuild = showString "FoldrBuild "
- showsPrec p MagicUnfold = showString "MagicUnfold "
- showsPrec p ConReused = showString "ConReused "
- showsPrec p CaseFloatFromLet= showString "CaseFloatFromLet "
- showsPrec p CaseOfCase = showString "CaseOfCase "
---UNUSED: showsPrec p CaseFloatFromApp= showString "CaseFloatFromApp "
- showsPrec p LetFloatFromLet = showString "LetFloatFromLet "
- showsPrec p LetFloatFromCase= showString "LetFloatFromCase "
---UNUSED: showsPrec p LetFloatFromApp = showString "LetFloatFromApp "
- showsPrec p KnownBranch = showString "KnownBranch "
- showsPrec p Let2Case = showString "Let2Case "
---UNUSED: showsPrec p UnboxingLet2Case= showString "UnboxingLet2Case "
- showsPrec p CaseMerge = showString "CaseMerge "
---UNUSED: showsPrec p CaseToLet = showString "CaseToLet "
- showsPrec p CaseElim = showString "CaseElim "
- showsPrec p CaseIdentity = showString "CaseIdentity "
- showsPrec p AtomicRhs = showString "AtomicRhs "
- showsPrec p EtaExpansion = showString "EtaExpansion "
---UNUSED: showsPrec p ArityExpand = showString "ArityExpand "
---UNUSED: showsPrec p ConstantFolding = showString "ConstantFolding "
- showsPrec p CaseOfError = showString "CaseOfError "
---UNUSED: showsPrec p InlineRemoved = showString "InlineRemoved "
- showsPrec p FoldrConsNil = showString "FoldrConsNil "
- showsPrec p Foldr_Nil = showString "Foldr_Nil "
- showsPrec p FoldrFoldr = showString "FoldrFoldr "
- showsPrec p Foldr_List = showString "Foldr_List "
- showsPrec p FoldrCons = showString "FoldrCons "
- showsPrec p FoldrInline = showString "FoldrInline "
- showsPrec p TyBetaReduction = showString "TyBetaReduction "
- showsPrec p BetaReduction = showString "BetaReduction "
-
-showSimplCount :: SimplCount -> String
-
-showSimplCount (SimplCount _ stuff)
- = shw stuff
+ | SpecialisationDone
+ | FillInCaseDefault
+ | LeavesExamined
+ deriving (Eq, Ord, Show)
+
+pprSimplCount :: SimplCount -> SDoc
+pprSimplCount (SimplCount stuff (_, unf1, unf2))
+ = vcat (map ppr_item stuff)
+ $$ (text "Most recent unfoldings (most recent at top):"
+ $$ nest 4 (vcat (map ppr (unf1 ++ unf2))))
where
- shw [] = ""
- shw ((t,n):tns) | n /= 0 = show t ++ ('\t' : show n) ++ ('\n' : shw tns)
- | otherwise = shw tns
+ ppr_item (t,n) = text (show t) <+> char '\t' <+> ppr n
zeroSimplCount :: SimplCount
-zeroSimplCount
- = SimplCount ILIT(0)
- [(UnfoldingDone, 0),
---UNUSED: (Unused, 0),
- (FoldrBuild, 0),
- (MagicUnfold, 0),
- (ConReused, 0),
- (CaseFloatFromLet, 0),
- (CaseOfCase, 0),
---UNUSED: (CaseFloatFromApp, 0),
- (LetFloatFromLet, 0),
- (LetFloatFromCase, 0),
---UNUSED: (LetFloatFromApp, 0),
- (KnownBranch, 0),
- (Let2Case, 0),
---UNUSED: (UnboxingLet2Case, 0),
- (CaseMerge, 0),
---UNUSED: (CaseToLet, 0),
- (CaseElim, 0),
- (CaseIdentity, 0),
- (AtomicRhs, 0),
- (EtaExpansion, 0),
---UNUSED: (ArityExpand,0),
---UNUSED: (ConstantFolding, 0),
- (CaseOfError, 0),
---UNUSED: (InlineRemoved,0),
- (FoldrConsNil,0),
- (Foldr_Nil,0),
- (FoldrFoldr,0),
- (Foldr_List,0),
- (FoldrCons,0),
- (FoldrInline,0),
- (TyBetaReduction,0),
- (BetaReduction,0) ]
---
---= array (con2tag_TickType UnfoldingDone, con2tag_TickType FoldrInline)
--- [ i := 0 | i <- indices zeroSimplCount ]
+zeroSimplCount = SimplCount [] (0, [], [])
+
+isZeroSimplCount :: SimplCount -> Bool
+isZeroSimplCount (SimplCount [] _) = True
+isZeroSimplCount (SimplCount [(LeavesExamined,_)] _) = True
+isZeroSimplCount other = False
+
+-- incTick is careful to be pretty strict, so we don't
+-- get a huge buildup of thunks
+incTick :: TickType -> FAST_INT -> TickCounts -> TickCounts
+incTick tick_type n []
+ = [(tick_type, IBOX(n))]
+
+incTick tick_type n (x@(ttype, I# cnt#) : xs)
+ = case tick_type `compare` ttype of
+ LT -> -- Insert here
+ (tick_type, IBOX(n)) : x : xs
+
+ EQ -> -- Increment
+ case cnt# +# n of
+ incd -> (ttype, IBOX(incd)) : xs
+
+ GT -> -- Move on
+ rest `seq` x : rest
+ where
+ rest = incTick tick_type n xs
+
+-- Second argument is more recent stuff
+plusSimplCount :: SimplCount -> SimplCount -> SimplCount
+plusSimplCount (SimplCount tc1 uh1) (SimplCount tc2 uh2)
+ = SimplCount (plusTickCounts tc1 tc2) (plusUnfolds uh1 uh2)
+
+plusTickCounts :: TickCounts -> TickCounts -> TickCounts
+plusTickCounts ts1 [] = ts1
+plusTickCounts [] ts2 = ts2
+plusTickCounts ((tt1,n1) : ts1) ((tt2,n2) : ts2)
+ = case tt1 `compare` tt2 of
+ LT -> (tt1,n1) : plusTickCounts ts1 ((tt2,n2) : ts2)
+ EQ -> (tt1,n1+n2) : plusTickCounts ts1 ts2
+ GT -> (tt2,n2) : plusTickCounts ((tt1,n1) : ts1) ts2
+
+-- Second argument is the more recent stuff
+plusUnfolds uh1 (0, h2, t2) = uh1 -- Nothing recent
+plusUnfolds (n1, h1, t1) (n2, h2, []) = (n2, h2, (h1++t1)) -- Small amount recent
+plusUnfolds (n1, h1, t1) uh2 = uh2 -- Decent batch recent
\end{code}
+
Counting-related monad functions:
+
\begin{code}
-tick :: TickType -> SmplM ()
-
-tick tick_type us (SimplCount n stuff)
- = ((), SimplCount (n _ADD_ ILIT(1))
-#ifdef OMIT_SIMPL_COUNTS
- stuff -- don't change anything
-#else
- (inc_tick stuff)
-#endif
- )
- where
- inc_tick [] = panic "couldn't inc_tick!"
- inc_tick (x@(ttype, cnt) : xs)
- = if ttype == tick_type then
- let
- incd = cnt + 1
- in
- (ttype, incd) : xs
- else
- x : inc_tick xs
-
-tickN :: TickType -> Int -> SmplM ()
-
-tickN tick_type IBOX(increment) us (SimplCount n stuff)
- = ((), SimplCount (n _ADD_ increment)
-#ifdef OMIT_SIMPL_COUNTS
- stuff -- don't change anything
-#else
- (inc_tick stuff)
-#endif
- )
+tick :: TickType -> SimplM ()
+
+tick tick_type
+ = doTickSmpl f
where
- inc_tick [] = panic "couldn't inc_tick!"
- inc_tick (x@(ttype, cnt) : xs)
- = if ttype == tick_type then
- let
- incd = cnt + IBOX(increment)
- in
- (ttype, incd) : xs
- else
- x : inc_tick xs
-
-simplCount :: SmplM Int
-simplCount us sc@(SimplCount n _) = (IBOX(n), sc)
-
-detailedSimplCount :: SmplM SimplCount
-detailedSimplCount us sc = (sc, sc)
-
-combineSimplCounts :: SimplCount -> SimplCount -> SimplCount
-
-#ifdef OMIT_SIMPL_COUNTS
-combineSimplCounts (SimplCount n1 stuff1) (SimplCount n2 stuff2)
- = SimplCount (n1 _ADD_ n2)
- stuff1 -- just pick one
-#else
-combineSimplCounts (SimplCount n1 stuff1) (SimplCount n2 stuff2)
- = SimplCount (n1 _ADD_ n2)
- (zipWith (\ (t1,c1) (t2,c2) -> (t1,c1+c2)) stuff1 stuff2)
-#endif
+ f (SimplCount stuff unf) = SimplCount (incTick tick_type ILIT(1) stuff) unf
+
+maxUnfoldHistory :: Int
+maxUnfoldHistory = 20
+
+tickUnfold :: Id -> SimplM ()
+tickUnfold id
+ = doTickSmpl f
+ where
+ f (SimplCount stuff (n_unf, unf1, unf2))
+ | n_unf >= maxUnfoldHistory = SimplCount new_stuff (1, [id], unf1)
+ | otherwise = SimplCount new_stuff (n_unf+1, id:unf1, unf2)
+ where
+ new_stuff = incTick UnfoldingDone ILIT(1) stuff
\end{code}
+
%************************************************************************
%* *
-\subsection{Monad primitives}
+\subsubsection{Command-line switches}
%* *
%************************************************************************
\begin{code}
-newId :: UniType -> SmplM Id
-newId ty us sc
- = (mkSysLocal SLIT("s") uniq ty mkUnknownSrcLoc, sc)
- where
- uniq = getSUnique us
+getSwitchChecker :: SimplM SwitchChecker
+getSwitchChecker env us sc = (seChkr env, us, sc)
-newIds :: [UniType] -> SmplM [Id]
-newIds tys us sc
- = (zipWith mk_id tys uniqs, sc)
- where
- uniqs = getSUniques (length tys) us
- mk_id ty uniq = mkSysLocal SLIT("s") uniq ty mkUnknownSrcLoc
+getSimplIntSwitch :: SwitchChecker -> (Int-> SimplifierSwitch) -> Int
+getSimplIntSwitch chkr switch
+ = expectJust "getSimplIntSwitch" (intSwitchSet chkr switch)
+\end{code}
-cloneTyVarSmpl :: TyVar -> SmplM TyVar
-cloneTyVarSmpl tyvar us sc
- = (new_tyvar, sc)
- where
- uniq = getSUnique us
- new_tyvar = cloneTyVar tyvar uniq
+@switchOffInlining@ 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!
+
+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...
+
+ Now, if that's the ONLY occurrence of f, it will be inlined inside g,
+ and thence copied multiple times when g is inlined.
-cloneId :: SimplEnv -> InBinder -> SmplM OutId
-cloneId env (id,_) us sc
- = (mkIdWithNewUniq id_with_new_ty uniq, sc)
+ 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 in_scope_env, which has all the
+unfolding info. At one point we did it by modifying the chkr so that
+it said "EssentialUnfoldingsOnly", but that prevented legitmate, and
+important, simplifications happening in the body of the RHS.
+
+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 inline-pragma,
+not by zapping the unfolding. The latter may still be useful for
+knowing when something is evaluated.
+
+June 98 update: I've gone back to dealing with this by adding
+the EssentialUnfoldingsOnly switch. That doesn't stop essential
+unfoldings, nor inlineUnconditionally stuff; and the thing's going
+to be inlined at every call site anyway. Running over the whole
+environment seems like wild overkill.
+
+\begin{code}
+switchOffInlining :: SimplM a -> SimplM a
+switchOffInlining m env@(SimplEnv { seChkr = sw_chkr }) us sc
+ = m (env { seChkr = new_chkr }) us sc
where
- id_with_new_ty = simplTyInId env id
- uniq = getSUnique us
+ new_chkr EssentialUnfoldingsOnly = SwBool True
+ new_chkr other = sw_chkr other
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsubsection{The ``enclosing cost-centre''}
+%* *
+%************************************************************************
+
+\begin{code}
+getEnclosingCC :: SimplM CostCentreStack
+getEnclosingCC env us sc = (seCC env, us, sc)
+
+setEnclosingCC :: CostCentreStack -> SimplM a -> SimplM a
+setEnclosingCC cc m env us sc = m (env { seCC = cc }) us sc
+\end{code}
-cloneIds :: SimplEnv -> [InBinder] -> SmplM [OutId]
-cloneIds env binders = mapSmpl (cloneId env) binders
+
+%************************************************************************
+%* *
+\subsubsection{The @SimplEnv@ type}
+%* *
+%************************************************************************
+
+\begin{code}
+type SubstEnv = (TyVarSubst, IdSubst)
+ -- The range of these substitutions 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.
+
+type InScopeEnv = IdOrTyVarSet
+ -- Domain 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
+
+-- INVARIANT: If t is in the in-scope set, it certainly won't be
+-- in the domain of the SubstEnv, and vice versa
\end{code}
+
+
+\begin{code}
+emptySubstEnv :: SubstEnv
+emptySubstEnv = (emptyVarEnv, emptyVarEnv)
+
+emptySimplEnv :: SwitchChecker -> SimplEnv
+
+emptySimplEnv sw_chkr
+ = SimplEnv { seChkr = sw_chkr, seCC = subsumedCCS,
+ seSubst = emptySubstEnv,
+ seInScope = emptyVarSet }
+
+ -- The top level "enclosing CC" is "SUBSUMED".
+
+getTyEnv :: SimplM (TyVarSubst, InScopeEnv)
+getTyEnv (SimplEnv {seSubst = (ty_subst,_), seInScope = in_scope}) us sc
+ = ((ty_subst, in_scope), us, sc)
+
+getValEnv :: SimplM (IdSubst, InScopeEnv)
+getValEnv (SimplEnv {seSubst = (_, id_subst), seInScope = in_scope}) us sc
+ = ((id_subst, in_scope), us, sc)
+
+getInScope :: SimplM InScopeEnv
+getInScope env us sc = (seInScope env, us, sc)
+
+setInScope :: InScopeEnv -> SimplM a -> SimplM a
+setInScope in_scope m env us sc = m (env {seInScope = in_scope}) us sc
+
+extendInScope :: CoreBndr -> SimplM a -> SimplM a
+extendInScope v m env@(SimplEnv {seInScope = in_scope}) us sc
+ = m (env {seInScope = extendVarSet in_scope v}) us sc
+
+extendInScopes :: [CoreBndr] -> SimplM a -> SimplM a
+extendInScopes vs m env@(SimplEnv {seInScope = in_scope}) us sc
+ = m (env {seInScope = foldl extendVarSet in_scope vs}) us sc
+
+modifyInScope :: CoreBndr -> SimplM a -> SimplM a
+modifyInScope v m env us sc
+#ifdef DEBUG
+ | not (v `elemVarSet` seInScope env )
+ = pprTrace "modifyInScope: not in scope:" (ppr v)
+ m env us sc
+#endif
+ | otherwise
+ = extendInScope v m env us sc
+
+getSubstEnv :: SimplM SubstEnv
+getSubstEnv env us sc = (seSubst env, us, sc)
+
+setSubstEnv :: SubstEnv -> SimplM a -> SimplM a
+setSubstEnv subst_env m env us sc = m (env {seSubst = subst_env}) us sc
+
+extendIdSubst :: Id -> SubstCoreExpr -> SimplM a -> SimplM a
+extendIdSubst id expr m env@(SimplEnv {seSubst = (ty_subst, id_subst)}) us sc
+ = m (env { seSubst = (ty_subst, extendVarEnv id_subst id expr) }) us sc
+
+extendTySubst :: TyVar -> OutType -> SimplM a -> SimplM a
+extendTySubst tv ty m env@(SimplEnv {seSubst = (ty_subst, id_subst)}) us sc
+ = m (env { seSubst = (extendVarEnv ty_subst tv ty, id_subst) }) us sc
+
+zapSubstEnv :: SimplM a -> SimplM a
+zapSubstEnv m env us sc = m (env {seSubst = emptySubstEnv}) us sc
+
+getSimplBinderStuff :: SimplM (TyVarSubst, IdSubst, InScopeEnv, UniqSupply)
+getSimplBinderStuff (SimplEnv {seSubst = (ty_subst, id_subst), seInScope = in_scope}) us sc
+ = ((ty_subst, id_subst, in_scope, us), us, sc)
+
+setSimplBinderStuff :: (TyVarSubst, IdSubst, InScopeEnv, UniqSupply)
+ -> SimplM a -> SimplM a
+setSimplBinderStuff (ty_subst, id_subst, in_scope, us) m env _ sc
+ = m (env {seSubst = (ty_subst, id_subst), seInScope = in_scope}) us sc
+\end{code}
+
+
+\begin{code}
+newId :: Type -> (Id -> SimplM a) -> SimplM a
+ -- Extends the in-scope-env too
+newId ty m env@(SimplEnv {seInScope = in_scope}) us sc
+ = case splitUniqSupply us of
+ (us1, us2) -> m v (env {seInScope = extendVarSet in_scope v}) us2 sc
+ where
+ v = mkSysLocal (uniqFromSupply us1) ty
+
+newIds :: [Type] -> ([Id] -> SimplM a) -> SimplM a
+newIds tys m env@(SimplEnv {seInScope = in_scope}) us sc
+ = case splitUniqSupply us of
+ (us1, us2) -> m vs (env {seInScope = foldl extendVarSet in_scope vs}) us2 sc
+ where
+ vs = zipWithEqual "newIds" mkSysLocal (uniqsFromSupply (length tys) us1) tys
+\end{code}
+
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