\begin{code}
module CoreUtils (
- coreExprType, coreAltsType,
+ exprType, coreAltsType,
+
+ mkNote, mkInlineMe, mkSCC, mkCoerce,
+
+ exprIsBottom, exprIsDupable, exprIsTrivial, exprIsCheap,
+ exprIsValue,exprOkForSpeculation, exprIsBig,
+ exprArity,
+
+ idAppIsBottom, idAppIsCheap,
+
+ etaReduceExpr, exprEtaExpandArity,
+
+ hashExpr,
- exprIsBottom, exprIsDupable, exprIsTrivial, exprIsWHNF, exprIsCheap,
- exprOkForSpeculation,
- FormSummary(..), mkFormSummary, whnfOrBottom, exprArity,
cheapEqExpr, eqExpr, applyTypeToArgs
) where
#include "HsVersions.h"
+import {-# SOURCE #-} CoreUnfold ( isEvaldUnfolding )
+
+import GlaExts -- For `xori`
+
import CoreSyn
+import CoreFVs ( exprFreeVars )
import PprCore ( pprCoreExpr )
-import Var ( IdOrTyVar, isId, isTyVar )
+import Var ( isId, isTyVar )
import VarSet
import VarEnv
-import Name ( isLocallyDefined )
-import Const ( Con, isWHNFCon, conIsTrivial, conIsCheap, conIsDupable,
- conType, conOkForSpeculation, conStrictness
+import Name ( isLocallyDefined, hashName )
+import Literal ( Literal, hashLiteral, literalType )
+import PrimOp ( primOpOkForSpeculation, primOpIsCheap )
+import Id ( Id, idType, idFlavour, idStrictness, idLBVarInfo,
+ idArity, idName, idUnfolding, idInfo
)
-import Id ( Id, idType, setIdType, idUnique, idAppIsBottom,
- getIdArity,
- getIdSpecialisation, setIdSpecialisation,
- getInlinePragma, setInlinePragma,
- getIdUnfolding, setIdUnfolding, idInfo
+import IdInfo ( arityLowerBound, InlinePragInfo(..),
+ LBVarInfo(..),
+ IdFlavour(..),
+ appIsBottom
)
-import IdInfo ( arityLowerBound, InlinePragInfo(..), lbvarInfo, LBVarInfo(..) )
import Type ( Type, mkFunTy, mkForAllTy,
splitFunTy_maybe, tyVarsOfType, tyVarsOfTypes,
isNotUsgTy, mkUsgTy, unUsgTy, UsageAnn(..),
- tidyTyVar, applyTys, isUnLiftedType
+ applyTys, isUnLiftedType
)
-import Demand ( isPrim, isLazy )
+import CostCentre ( CostCentre )
import Unique ( buildIdKey, augmentIdKey )
import Util ( zipWithEqual, mapAccumL )
import Outputable
%************************************************************************
\begin{code}
-coreExprType :: CoreExpr -> Type
-
-coreExprType (Var var) = idType var
-coreExprType (Let _ body) = coreExprType body
-coreExprType (Case _ _ alts) = coreAltsType alts
-coreExprType (Note (Coerce ty _) e) = ty
-coreExprType (Note (TermUsg u) e) = mkUsgTy u (unUsgTy (coreExprType e))
-coreExprType (Note other_note e) = coreExprType e
-coreExprType e@(Con con args) = applyTypeToArgs e (conType con) args
-
-coreExprType (Lam binder expr)
- | isId binder = (case (lbvarInfo . idInfo) binder of
+exprType :: CoreExpr -> Type
+
+exprType (Var var) = idType var
+exprType (Lit lit) = literalType lit
+exprType (Let _ body) = exprType body
+exprType (Case _ _ alts) = coreAltsType alts
+exprType (Note (Coerce ty _) e) = ty -- **! should take usage from e
+exprType (Note (TermUsg u) e) = mkUsgTy u (unUsgTy (exprType e))
+exprType (Note other_note e) = exprType e
+exprType (Lam binder expr)
+ | isId binder = (case idLBVarInfo binder of
IsOneShotLambda -> mkUsgTy UsOnce
otherwise -> id) $
- idType binder `mkFunTy` coreExprType expr
- | isTyVar binder = mkForAllTy binder (coreExprType expr)
+ idType binder `mkFunTy` exprType expr
+ | isTyVar binder = mkForAllTy binder (exprType expr)
-coreExprType e@(App _ _)
+exprType e@(App _ _)
= case collectArgs e of
- (fun, args) -> applyTypeToArgs e (coreExprType fun) args
+ (fun, args) -> applyTypeToArgs e (exprType fun) args
-coreExprType other = pprTrace "coreExprType" (pprCoreExpr other) alphaTy
+exprType other = pprTrace "exprType" (pprCoreExpr other) alphaTy
coreAltsType :: [CoreAlt] -> Type
-coreAltsType ((_,_,rhs) : _) = coreExprType rhs
+coreAltsType ((_,_,rhs) : _) = exprType rhs
\end{code}
\begin{code}
applyTypeToArgs e op_ty (Type ty : args)
= -- Accumulate type arguments so we can instantiate all at once
- ASSERT2( all isNotUsgTy tys, ppr e <+> text "of" <+> ppr op_ty <+> text "to" <+> ppr (Type ty : args) <+> text "i.e." <+> ppr tys )
+ ASSERT2( all isNotUsgTy tys,
+ ppr e <+> text "of" <+> ppr op_ty <+> text "to" <+>
+ ppr (Type ty : args) <+> text "i.e." <+> ppr tys )
applyTypeToArgs e (applyTys op_ty tys) rest_args
where
(tys, rest_args) = go [ty] args
\end{code}
+
%************************************************************************
%* *
-\subsection{Figuring out things about expressions}
+\subsection{Attaching notes
%* *
%************************************************************************
+mkNote removes redundant coercions, and SCCs where possible
+
\begin{code}
-data FormSummary
- = VarForm -- Expression is a variable (or scc var, etc)
- | ValueForm -- Expression is a value: i.e. a value-lambda,constructor, or literal
- | BottomForm -- Expression is guaranteed to be bottom. We're more gung
- -- ho about inlining such things, because it can't waste work
- | OtherForm -- Anything else
-
-instance Outputable FormSummary where
- ppr VarForm = ptext SLIT("Var")
- ppr ValueForm = ptext SLIT("Value")
- ppr BottomForm = ptext SLIT("Bot")
- ppr OtherForm = ptext SLIT("Other")
-
-whnfOrBottom :: FormSummary -> Bool
-whnfOrBottom VarForm = True
-whnfOrBottom ValueForm = True
-whnfOrBottom BottomForm = True
-whnfOrBottom OtherForm = False
+mkNote :: Note -> CoreExpr -> CoreExpr
+mkNote (Coerce to_ty from_ty) expr = mkCoerce to_ty from_ty expr
+mkNote (SCC cc) expr = mkSCC cc expr
+mkNote InlineMe expr = mkInlineMe expr
+mkNote note expr = Note note expr
+
+-- Slide InlineCall in around the function
+-- No longer necessary I think (SLPJ Apr 99)
+-- mkNote InlineCall (App f a) = App (mkNote InlineCall f) a
+-- mkNote InlineCall (Var v) = Note InlineCall (Var v)
+-- mkNote InlineCall expr = expr
\end{code}
+Drop trivial InlineMe's. This is somewhat important, because if we have an unfolding
+that looks like (Note InlineMe (Var v)), the InlineMe doesn't go away because it may
+not be *applied* to anything.
+
\begin{code}
-mkFormSummary :: CoreExpr -> FormSummary
-mkFormSummary expr
- = go (0::Int) expr -- The "n" is the number of *value* arguments so far
- where
- go n (Con con _) | isWHNFCon con = ValueForm
- | otherwise = OtherForm
+mkInlineMe e | exprIsTrivial e = e
+ | otherwise = Note InlineMe e
+\end{code}
+
+
- go n (Note _ e) = go n e
+\begin{code}
+mkCoerce :: Type -> Type -> Expr b -> Expr b
+-- In (mkCoerce to_ty from_ty e), we require that from_ty = exprType e
+-- But exprType is defined in CoreUtils, so we don't check the assertion
- go n (Let (NonRec b r) e) | exprIsTrivial r = go n e -- let f = f' alpha in (f,g)
- -- should be treated as a value
- go n (Let _ e) = OtherForm
- go n (Case _ _ _) = OtherForm
+mkCoerce to_ty from_ty (Note (Coerce to_ty2 from_ty2) expr)
+ = ASSERT( from_ty == to_ty2 )
+ mkCoerce to_ty from_ty2 expr
- go 0 (Lam x e) | isId x = ValueForm -- NB: \x.bottom /= bottom!
- | otherwise = go 0 e
- go n (Lam x e) | isId x = go (n-1) e -- Applied lambda
- | otherwise = go n e
+mkCoerce to_ty from_ty expr
+ | to_ty == from_ty = expr
+ | otherwise = Note (Coerce to_ty from_ty) expr
+\end{code}
- go n (App fun (Type _)) = go n fun -- Ignore type args
- go n (App fun arg) = go (n+1) fun
+\begin{code}
+mkSCC :: CostCentre -> Expr b -> Expr b
+ -- Note: Nested SCC's *are* preserved for the benefit of
+ -- cost centre stack profiling (Durham)
- go n (Var f) | idAppIsBottom f n = BottomForm
- go 0 (Var f) = VarForm
- go n (Var f) | n < arityLowerBound (getIdArity f) = ValueForm
- | otherwise = OtherForm
+mkSCC cc (Lit lit) = Lit lit
+mkSCC cc (Lam x e) = Lam x (mkSCC cc e) -- Move _scc_ inside lambda
+mkSCC cc expr = Note (SCC cc) expr
\end{code}
+
+%************************************************************************
+%* *
+\subsection{Figuring out things about expressions}
+%* *
+%************************************************************************
+
@exprIsTrivial@ is true of expressions we are unconditionally
happy to duplicate; simple variables and constants,
and type applications.
\begin{code}
exprIsTrivial (Type _) = True
+exprIsTrivial (Lit lit) = True
exprIsTrivial (Var v) = True
exprIsTrivial (App e arg) = isTypeArg arg && exprIsTrivial e
exprIsTrivial (Note _ e) = exprIsTrivial e
-exprIsTrivial (Con con args) = conIsTrivial con && all isTypeArg args
exprIsTrivial (Lam b body) | isTyVar b = exprIsTrivial body
exprIsTrivial other = False
\end{code}
@exprIsDupable@ is true of expressions that can be duplicated at a modest
- cost in space. This will only happen in different case
+ cost in code size. This will only happen in different case
branches, so there's no issue about duplicating work.
+
+ That is, exprIsDupable returns True of (f x) even if
+ f is very very expensive to call.
+
Its only purpose is to avoid fruitless let-binding
and then inlining of case join points
\begin{code}
exprIsDupable (Type _) = True
-exprIsDupable (Con con args) = conIsDupable con &&
- all exprIsDupable args &&
- valArgCount args <= dupAppSize
-
+exprIsDupable (Var v) = True
+exprIsDupable (Lit lit) = True
exprIsDupable (Note _ e) = exprIsDupable e
-exprIsDupable expr = case collectArgs expr of
- (Var f, args) -> valArgCount args <= dupAppSize
- other -> False
+exprIsDupable expr
+ = go expr 0
+ where
+ go (Var v) n_args = True
+ go (App f a) n_args = n_args < dupAppSize
+ && exprIsDupable a
+ && go f (n_args+1)
+ go other n_args = False
dupAppSize :: Int
dupAppSize = 4 -- Size of application we are prepared to duplicate
it is obviously in weak head normal form, or is cheap to get to WHNF.
[Note that that's not the same as exprIsDupable; an expression might be
big, and hence not dupable, but still cheap.]
-By ``cheap'' we mean a computation we're willing to push inside a lambda
-in order to bring a couple of lambdas together. That might mean it gets
-evaluated more than once, instead of being shared. The main examples of things
-which aren't WHNF but are ``cheap'' are:
+
+By ``cheap'' we mean a computation we're willing to:
+ push inside a lambda, or
+ inline at more than one place
+That might mean it gets evaluated more than once, instead of being
+shared. The main examples of things which aren't WHNF but are
+``cheap'' are:
* case e of
pi -> ei
where op is a cheap primitive operator
-\begin{code}
-exprIsCheap :: CoreExpr -> Bool
-exprIsCheap (Type _) = True
-exprIsCheap (Var _) = True
-exprIsCheap (Con con args) = conIsCheap con && all exprIsCheap args
-exprIsCheap (Note _ e) = exprIsCheap e
-exprIsCheap (Lam x e) = if isId x then True else exprIsCheap e
-exprIsCheap (Let bind body) = all exprIsCheap (rhssOfBind bind) && exprIsCheap body
-exprIsCheap (Case scrut _ alts) = exprIsCheap scrut &&
- all (\(_,_,rhs) -> exprIsCheap rhs) alts
-
-exprIsCheap other_expr -- look for manifest partial application
- = case collectArgs other_expr of
- (f, args) -> isPap f (valArgCount args) && all exprIsCheap args
-\end{code}
+ * error "foo"
+
+Notice that a variable is considered 'cheap': we can push it inside a lambda,
+because sharing will make sure it is only evaluated once.
\begin{code}
-isPap :: CoreExpr -- Function
- -> Int -- Number of value args
- -> Bool
-isPap (Var f) n_val_args
- = idAppIsBottom f n_val_args
- -- Application of a function which
- -- always gives bottom; we treat this as
- -- a WHNF, because it certainly doesn't
- -- need to be shared!
-
- || n_val_args == 0 -- Just a type application of
+exprIsCheap :: CoreExpr -> Bool
+exprIsCheap (Lit lit) = True
+exprIsCheap (Type _) = True
+exprIsCheap (Var _) = True
+exprIsCheap (Note _ e) = exprIsCheap e
+exprIsCheap (Lam x e) = if isId x then True else exprIsCheap e
+exprIsCheap (Case (Var v) _ alts) = and [exprIsCheap rhs | (_,_,rhs) <- alts]
+ -- Experimentally, treat (case x of ...) as cheap
+ -- This improves arities of overloaded functions where
+ -- there is only dictionary selection (no construction) involved
+exprIsCheap other_expr
+ = go other_expr 0 True
+ where
+ go (Var f) n_args args_cheap
+ = (idAppIsCheap f n_args && args_cheap)
+ -- A constructor, cheap primop, or partial application
+
+ || idAppIsBottom f n_args
+ -- Application of a function which
+ -- always gives bottom; we treat this as
+ -- a WHNF, because it certainly doesn't
+ -- need to be shared!
+
+ go (App f a) n_args args_cheap
+ | isTypeArg a = go f n_args args_cheap
+ | otherwise = go f (n_args + 1) (exprIsCheap a && args_cheap)
+
+ go other n_args args_cheap = False
+
+idAppIsCheap :: Id -> Int -> Bool
+idAppIsCheap id n_val_args
+ | n_val_args == 0 = True -- Just a type application of
-- a variable (f t1 t2 t3)
-- counts as WHNF
-
- || n_val_args < arityLowerBound (getIdArity f)
-
-isPap fun n_val_args = False
+ | otherwise = case idFlavour id of
+ DataConId _ -> True
+ RecordSelId _ -> True -- I'm experimenting with making record selection
+ -- look cheap, so we will substitute it inside a
+ -- lambda. Particularly for dictionary field selection
+
+ PrimOpId op -> primOpIsCheap op -- In principle we should worry about primops
+ -- that return a type variable, since the result
+ -- might be applied to something, but I'm not going
+ -- to bother to check the number of args
+ other -> n_val_args < idArity id
\end{code}
-exprOkForSpeculation returns True of an UNLIFTED-TYPE expression that it is safe
-to evaluate even if normal order eval might not evaluate the expression
-at all. E.G.
+exprOkForSpeculation returns True of an expression that it is
+
+ * safe to evaluate even if normal order eval might not
+ evaluate the expression at all, or
+
+ * safe *not* to evaluate even if normal order would do so
+
+It returns True iff
+
+ the expression guarantees to terminate,
+ soon,
+ without raising an exception,
+ without causing a side effect (e.g. writing a mutable variable)
+
+E.G.
let x = case y# +# 1# of { r# -> I# r# }
in E
==>
\begin{code}
exprOkForSpeculation :: CoreExpr -> Bool
-exprOkForSpeculation (Var v) = True -- Unlifted type => already evaluated
-
-exprOkForSpeculation (Note _ e) = exprOkForSpeculation e
-exprOkForSpeculation (Let (NonRec b r) e) = isUnLiftedType (idType b) &&
- exprOkForSpeculation r &&
- exprOkForSpeculation e
-exprOkForSpeculation (Let (Rec _) _) = False
-exprOkForSpeculation (Case _ _ _) = False -- Conservative
-exprOkForSpeculation (App _ _) = False
-
-exprOkForSpeculation (Con con args)
- = conOkForSpeculation con &&
- and (zipWith ok (filter isValArg args) (fst (conStrictness con)))
+exprOkForSpeculation (Lit _) = True
+exprOkForSpeculation (Var v) = isUnLiftedType (idType v)
+exprOkForSpeculation (Note _ e) = exprOkForSpeculation e
+exprOkForSpeculation other_expr
+ = go other_expr 0 True
where
- ok arg demand | isLazy demand = True
- | isPrim demand = exprOkForSpeculation arg
- | otherwise = False
-
-exprOkForSpeculation other = panic "exprOkForSpeculation"
- -- Lam, Type
+ go (Var f) n_args args_ok
+ = case idFlavour f of
+ DataConId _ -> True -- The strictness of the constructor has already
+ -- been expressed by its "wrapper", so we don't need
+ -- to take the arguments into account
+
+ PrimOpId op -> primOpOkForSpeculation op && args_ok
+ -- A bit conservative: we don't really need
+ -- to care about lazy arguments, but this is easy
+
+ other -> False
+
+ go (App f a) n_args args_ok
+ | isTypeArg a = go f n_args args_ok
+ | otherwise = go f (n_args + 1) (exprOkForSpeculation a && args_ok)
+
+ go other n_args args_ok = False
\end{code}
go n (Case e _ _) = go 0 e -- Just check the scrut
go n (App e _) = go (n+1) e
go n (Var v) = idAppIsBottom v n
- go n (Con _ _) = False
+ go n (Lit _) = False
go n (Lam _ _) = False
+
+idAppIsBottom :: Id -> Int -> Bool
+idAppIsBottom id n_val_args = appIsBottom (idStrictness id) n_val_args
\end{code}
-exprIsWHNF reports True for head normal forms. Note that does not necessarily
-mean *normal* forms; constructors might have non-trivial argument expressions, for
-example. We use a let binding for WHNFs, rather than a case binding, even if it's
-used strictly. We try to expose WHNFs by floating lets out of the RHS of lets.
+@exprIsValue@ returns true for expressions that are certainly *already*
+evaluated to WHNF. This is used to decide wether it's ok to change
+ case x of _ -> e ===> e
+
+and to decide whether it's safe to discard a `seq`
-We treat applications of buildId and augmentId as honorary WHNFs, because we
-want them to get exposed
+So, it does *not* treat variables as evaluated, unless they say they are
\begin{code}
-exprIsWHNF :: CoreExpr -> Bool -- True => Variable, value-lambda, constructor, PAP
-exprIsWHNF (Type ty) = True -- Types are honorary WHNFs; we don't mind
+exprIsValue :: CoreExpr -> Bool -- True => Value-lambda, constructor, PAP
+exprIsValue (Type ty) = True -- Types are honorary Values; we don't mind
-- copying them
-exprIsWHNF (Var v) = True
-exprIsWHNF (Lam b e) = isId b || exprIsWHNF e
-exprIsWHNF (Note _ e) = exprIsWHNF e
-exprIsWHNF (Let _ e) = False
-exprIsWHNF (Case _ _ _) = False
-exprIsWHNF (Con con _) = isWHNFCon con
-exprIsWHNF e@(App _ _) = case collectArgs e of
- (Var v, args) -> n_val_args == 0 ||
- fun_arity > n_val_args ||
- v_uniq == buildIdKey ||
- v_uniq == augmentIdKey
- where
- n_val_args = valArgCount args
- fun_arity = arityLowerBound (getIdArity v)
- v_uniq = idUnique v
-
- _ -> False
+exprIsValue (Lit l) = True
+exprIsValue (Lam b e) = isId b || exprIsValue e
+exprIsValue (Note _ e) = exprIsValue e
+exprIsValue other_expr
+ = go other_expr 0
+ where
+ go (Var f) n_args = idAppIsValue f n_args
+
+ go (App f a) n_args
+ | isTypeArg a = go f n_args
+ | otherwise = go f (n_args + 1)
+
+ go (Note _ f) n_args = go f n_args
+
+ go other n_args = False
+
+idAppIsValue :: Id -> Int -> Bool
+idAppIsValue id n_val_args
+ = case idFlavour id of
+ DataConId _ -> True
+ PrimOpId _ -> n_val_args < idArity id
+ other | n_val_args == 0 -> isEvaldUnfolding (idUnfolding id)
+ | otherwise -> n_val_args < idArity id
+ -- A worry: what if an Id's unfolding is just itself:
+ -- then we could get an infinite loop...
\end{code}
\begin{code}
exprArity :: CoreExpr -> Int -- How many value lambdas are at the top
-exprArity (Lam b e) | isTyVar b = exprArity e
- | otherwise = 1 + exprArity e
-exprArity other = 0
+exprArity (Lam b e) | isTyVar b = exprArity e
+ | otherwise = 1 + exprArity e
+
+exprArity (Note note e) | ok_note note = exprArity e
+ where
+ ok_note (Coerce _ _) = True
+ -- We *do* look through coerces when getting arities.
+ -- Reason: arities are to do with *representation* and
+ -- work duplication.
+ ok_note InlineMe = True
+ ok_note InlineCall = True
+ ok_note other = False
+ -- SCC and TermUsg might be over-conservative?
+
+exprArity other = 0
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsection{Eta reduction and expansion}
+%* *
+%************************************************************************
+
+@etaReduceExpr@ trys an eta reduction at the top level of a Core Expr.
+
+e.g. \ x y -> f x y ===> f
+
+But we only do this if it gets rid of a whole lambda, not part.
+The idea is that lambdas are often quite helpful: they indicate
+head normal forms, so we don't want to chuck them away lightly.
+
+\begin{code}
+etaReduceExpr :: CoreExpr -> CoreExpr
+ -- ToDo: we should really check that we don't turn a non-bottom
+ -- lambda into a bottom variable. Sigh
+
+etaReduceExpr expr@(Lam bndr body)
+ = check (reverse binders) body
+ where
+ (binders, body) = collectBinders expr
+
+ check [] body
+ | not (any (`elemVarSet` body_fvs) binders)
+ = body -- Success!
+ where
+ body_fvs = exprFreeVars body
+
+ check (b : bs) (App fun arg)
+ | (varToCoreExpr b `cheapEqExpr` arg)
+ = check bs fun
+
+ check _ _ = expr -- Bale out
+
+etaReduceExpr expr = expr -- The common case
+\end{code}
+
+
+\begin{code}
+exprEtaExpandArity :: CoreExpr -> Int -- The number of args the thing can be applied to
+ -- without doing much work
+-- This is used when eta expanding
+-- e ==> \xy -> e x y
+--
+-- It returns 1 (or more) to:
+-- case x of p -> \s -> ...
+-- because for I/O ish things we really want to get that \s to the top.
+-- We are prepared to evaluate x each time round the loop in order to get that
+-- Hence "generous" arity
+
+exprEtaExpandArity e
+ = go e
+ where
+ go (Var v) = idArity v
+ go (App f (Type _)) = go f
+ go (App f a) | exprIsCheap a = (go f - 1) `max` 0 -- Never go -ve!
+ go (Lam x e) | isId x = go e + 1
+ | otherwise = go e
+ go (Note n e) | ok_note n = go e
+ go (Case scrut _ alts)
+ | exprIsCheap scrut = min_zero [go rhs | (_,_,rhs) <- alts]
+ go (Let b e)
+ | all exprIsCheap (rhssOfBind b) = go e
+
+ go other = 0
+
+ ok_note (Coerce _ _) = True
+ ok_note InlineCall = True
+ ok_note other = False
+ -- Notice that we do not look through __inline_me__
+ -- This one is a bit more surprising, but consider
+ -- f = _inline_me (\x -> e)
+ -- We DO NOT want to eta expand this to
+ -- f = \x -> (_inline_me (\x -> e)) x
+ -- because the _inline_me gets dropped now it is applied,
+ -- giving just
+ -- f = \x -> e
+ -- A Bad Idea
+
+min_zero :: [Int] -> Int -- Find the minimum, but zero is the smallest
+min_zero (x:xs) = go x xs
+ where
+ go 0 xs = 0 -- Nothing beats zero
+ go min [] = min
+ go min (x:xs) | x < min = go x xs
+ | otherwise = go min xs
+
\end{code}
\begin{code}
cheapEqExpr :: Expr b -> Expr b -> Bool
-cheapEqExpr (Var v1) (Var v2) = v1==v2
-cheapEqExpr (Con con1 args1) (Con con2 args2)
- = con1 == con2 &&
- and (zipWithEqual "cheapEqExpr" cheapEqExpr args1 args2)
+cheapEqExpr (Var v1) (Var v2) = v1==v2
+cheapEqExpr (Lit lit1) (Lit lit2) = lit1 == lit2
+cheapEqExpr (Type t1) (Type t2) = t1 == t2
cheapEqExpr (App f1 a1) (App f2 a2)
= f1 `cheapEqExpr` f2 && a1 `cheapEqExpr` a2
-cheapEqExpr (Type t1) (Type t2) = t1 == t2
-
cheapEqExpr _ _ = False
+
+exprIsBig :: Expr b -> Bool
+-- Returns True of expressions that are too big to be compared by cheapEqExpr
+exprIsBig (Lit _) = False
+exprIsBig (Var v) = False
+exprIsBig (Type t) = False
+exprIsBig (App f a) = exprIsBig f || exprIsBig a
+exprIsBig other = True
\end{code}
Just v1' -> v1' == v2
Nothing -> v1 == v2
- eq env (Con c1 es1) (Con c2 es2) = c1 == c2 && eq_list env es1 es2
+ eq env (Lit lit1) (Lit lit2) = lit1 == lit2
eq env (App f1 a1) (App f2 a2) = eq env f1 f2 && eq env a1 a2
eq env (Lam v1 e1) (Lam v2 e2) = eq (extendVarEnv env v1 v2) e1 e2
eq env (Let (NonRec v1 r1) e1)
eq (extendVarEnvList env (vs1 `zip` vs2)) r1 r2
eq_note env (SCC cc1) (SCC cc2) = cc1 == cc2
- eq_note env (Coerce f1 t1) (Coerce f2 t2) = f1==f2 && t1==t2
+ eq_note env (Coerce t1 f1) (Coerce t2 f2) = t1==t2 && f1==f2
eq_note env InlineCall InlineCall = True
eq_note env other1 other2 = False
\end{code}
+%************************************************************************
+%* *
+\subsection{Hashing}
+%* *
+%************************************************************************
+
+\begin{code}
+hashExpr :: CoreExpr -> Int
+hashExpr e | hash < 0 = 77 -- Just in case we hit -maxInt
+ | otherwise = hash
+ where
+ hash = abs (hash_expr e) -- Negative numbers kill UniqFM
+
+hash_expr (Note _ e) = hash_expr e
+hash_expr (Let (NonRec b r) e) = hashId b
+hash_expr (Let (Rec ((b,r):_)) e) = hashId b
+hash_expr (Case _ b _) = hashId b
+hash_expr (App f e) = hash_expr f * fast_hash_expr e
+hash_expr (Var v) = hashId v
+hash_expr (Lit lit) = hashLiteral lit
+hash_expr (Lam b _) = hashId b
+hash_expr (Type t) = trace "hash_expr: type" 1 -- Shouldn't happen
+
+fast_hash_expr (Var v) = hashId v
+fast_hash_expr (Lit lit) = hashLiteral lit
+fast_hash_expr (App f (Type _)) = fast_hash_expr f
+fast_hash_expr (App f a) = fast_hash_expr a
+fast_hash_expr (Lam b _) = hashId b
+fast_hash_expr other = 1
+
+hashId :: Id -> Int
+hashId id = hashName (idName id)
+\end{code}