%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[CoreUtils]{Utility functions on @Core@ syntax}
\begin{code}
module CoreUtils (
- coreExprType, coreAltsType, coreExprCc,
-
- mkCoreIfThenElse,
- argToExpr,
- unTagBinders, unTagBindersAlts,
-
- maybeErrorApp,
- nonErrorRHSs,
- squashableDictishCcExpr,
- idSpecVars
+ IdSubst, SubstCoreExpr(..),
+
+ coreExprType, exprFreeVars, exprSomeFreeVars,
+
+ exprIsBottom, exprIsDupable, exprIsTrivial, exprIsWHNF, exprIsCheap,
+ FormSummary(..), mkFormSummary, whnfOrBottom,
+ cheapEqExpr,
+
+ substExpr, substId, substIds,
+ idSpecVars, idFreeVars,
+
+ squashableDictishCcExpr
) where
#include "HsVersions.h"
-import CoreSyn
+import {-# SOURCE #-} CoreUnfold ( noUnfolding, hasUnfolding )
-import CostCentre ( isDictCC, CostCentre, noCostCentre )
-import MkId ( mkSysLocal )
-import Id ( idType, isBottomingId, getIdSpecialisation,
- dataConRepType,
- Id
- )
-import Literal ( literalType, Literal(..) )
-import Maybes ( catMaybes, maybeToBool )
-import PprCore
-import PrimOp ( primOpType, PrimOp(..) )
-import SpecEnv ( specEnvValues )
-import SrcLoc ( noSrcLoc )
-import Type ( mkFunTy, mkForAllTy, mkTyVarTy,
- splitFunTy_maybe, applyTys, isUnpointedType,
- splitSigmaTy, splitFunTys,
- Type
- )
-import TysWiredIn ( trueDataCon, falseDataCon )
-import BasicTypes ( Unused )
-import UniqSupply ( returnUs, thenUs,
- mapAndUnzipUs, getUnique,
- UniqSM
+import CoreSyn
+import PprCore () -- Instances only
+import Var ( IdOrTyVar, isId, isTyVar )
+import VarSet
+import VarEnv
+import Name ( isLocallyDefined )
+import Const ( Con(..), isWHNFCon, conIsTrivial, conIsCheap )
+import Id ( Id, idType, setIdType, idUnique, isBottomingId,
+ getIdArity, idFreeTyVars,
+ getIdSpecialisation, setIdSpecialisation,
+ getInlinePragma, setInlinePragma,
+ getIdUnfolding, setIdUnfolding
)
-import Outputable ( assertPanic, pprPanic, ppr, vcat, panic )
+import IdInfo ( arityLowerBound, InlinePragInfo(..) )
+import SpecEnv ( emptySpecEnv, specEnvToList, isEmptySpecEnv )
+import CostCentre ( isDictCC, CostCentre )
+import Const ( Con, conType )
+import Type ( Type, TyVarSubst, mkFunTy, mkForAllTy,
+ splitFunTy_maybe, applyTys, tyVarsOfType, tyVarsOfTypes,
+ fullSubstTy, substTyVar )
+import Unique ( buildIdKey, augmentIdKey )
+import Util ( zipWithEqual, mapAccumL )
+import Outputable
+import TysPrim ( alphaTy ) -- Debgging only
+\end{code}
+
+%************************************************************************
+%* *
+\subsection{Substitutions}
+%* *
+%************************************************************************
+
+\begin{code}
+type IdSubst = IdEnv SubstCoreExpr -- Maps Ids to SubstCoreExpr
+
+data SubstCoreExpr
+ = Done CoreExpr -- No more substitution needed
+ | SubstMe CoreExpr TyVarSubst IdSubst -- A suspended substitution
\end{code}
%************************************************************************
\begin{code}
coreExprType :: CoreExpr -> Type
-coreExprType (Var var) = idType var
-coreExprType (Lit lit) = literalType lit
-
-coreExprType (Let _ body) = coreExprType body
-coreExprType (Case _ alts) = coreAltsType alts
+coreExprType (Var var) = idType var
+coreExprType (Let _ body) = coreExprType body
+coreExprType (Case _ _ ((_,_,rhs):_)) = coreExprType rhs
coreExprType (Note (Coerce ty _) e) = ty
coreExprType (Note other_note e) = coreExprType e
--- a Con is a fully-saturated application of a data constructor
--- a Prim is <ditto> of a PrimOp
+coreExprType e@(Con con args) = applyTypeToArgs e (conType con) args
-coreExprType (Con con args) =
--- pprTrace "appTyArgs" (hsep [ppr con, semi,
--- ppr con_ty, semi,
--- ppr args]) $
- applyTypeToArgs con_ty args
- where
- con_ty = dataConRepType con
+coreExprType (Lam binder expr)
+ | isId binder = idType binder `mkFunTy` coreExprType expr
+ | isTyVar binder = mkForAllTy binder (coreExprType expr)
-coreExprType (Prim op args) = applyTypeToArgs (primOpType op) args
+coreExprType e@(App _ _)
+ = case collectArgs e of
+ (fun, args) -> applyTypeToArgs e (coreExprType fun) args
-coreExprType (Lam (ValBinder binder) expr)
- = idType binder `mkFunTy` coreExprType expr
-
-coreExprType (Lam (TyBinder tyvar) expr)
- = mkForAllTy tyvar (coreExprType expr)
-
-coreExprType (App expr (TyArg ty))
- = -- Gather type args; more efficient to instantiate the type all at once
- go expr [ty]
- where
- go (App expr (TyArg ty)) tys = go expr (ty:tys)
- go expr tys = applyTys (coreExprType expr) tys
-
-coreExprType (App expr val_arg)
- = ASSERT(isValArg val_arg)
- let
- fun_ty = coreExprType expr
- in
- case (splitFunTy_maybe fun_ty) of
- Just (_, result_ty) -> result_ty
-#ifdef DEBUG
- Nothing -> pprPanic "coreExprType:\n"
- (vcat [ppr fun_ty, ppr (App expr val_arg)])
-#endif
+coreExprType other = pprTrace "coreExprType" (ppr other) alphaTy
\end{code}
\begin{code}
-coreAltsType :: CoreCaseAlts -> Type
+-- The "e" argument is just for debugging
-coreAltsType (AlgAlts [] deflt) = default_ty deflt
-coreAltsType (AlgAlts ((_,_,rhs1):_) _) = coreExprType rhs1
+applyTypeToArgs e op_ty [] = op_ty
-coreAltsType (PrimAlts [] deflt) = default_ty deflt
-coreAltsType (PrimAlts ((_,rhs1):_) _) = coreExprType rhs1
-
-default_ty NoDefault = panic "coreExprType:Case:default_ty"
-default_ty (BindDefault _ rhs) = coreExprType rhs
-\end{code}
-
-\begin{code}
-applyTypeToArgs op_ty (TyArg ty : args)
+applyTypeToArgs e op_ty (Type ty : args)
= -- Accumulate type arguments so we can instantiate all at once
- applyTypeToArgs (applyTys op_ty tys) rest_args
+ applyTypeToArgs e (applyTys op_ty tys) rest_args
where
- (tys, rest_args) = go [ty] args
- go tys (TyArg ty : args) = go (ty:tys) args
- go tys rest_args = (reverse tys, rest_args)
+ (tys, rest_args) = go [ty] args
+ go tys (Type ty : args) = go (ty:tys) args
+ go tys rest_args = (reverse tys, rest_args)
-applyTypeToArgs op_ty (val_or_lit_arg:args)
+applyTypeToArgs e op_ty (other_arg : args)
= case (splitFunTy_maybe op_ty) of
- Just (_, res_ty) -> applyTypeToArgs res_ty args
-
-applyTypeToArgs op_ty [] = op_ty
+ Just (_, res_ty) -> applyTypeToArgs e res_ty args
+ Nothing -> pprPanic "applyTypeToArgs" (ppr e)
\end{code}
-coreExprCc gets the cost centre enclosing an expression, if any.
-It looks inside lambdas because (scc "foo" \x.e) = \x.scc "foo" e
-
-\begin{code}
-coreExprCc :: GenCoreExpr val_bdr val_occ flexi -> CostCentre
-coreExprCc (Note (SCC cc) e) = cc
-coreExprCc (Note other_note e) = coreExprCc e
-coreExprCc (Lam _ e) = coreExprCc e
-coreExprCc other = noCostCentre
-\end{code}
%************************************************************************
%* *
-\subsection{Routines to manufacture bits of @CoreExpr@}
+\subsection{Figuring out things about expressions}
%* *
%************************************************************************
\begin{code}
-mkCoreIfThenElse (Var bool) then_expr else_expr
- | bool == trueDataCon = then_expr
- | bool == falseDataCon = else_expr
-
-mkCoreIfThenElse guard then_expr else_expr
- = Case guard
- (AlgAlts [ (trueDataCon, [], then_expr),
- (falseDataCon, [], else_expr) ]
- NoDefault )
+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
\end{code}
-For making @Apps@ and @Lets@, we must take appropriate evasive
-action if the thing being bound has unboxed type. @mkCoApp@ requires
-a name supply to do its work.
-
-@mkCoApps@, @mkCoCon@ and @mkCoPrim@ also handle the
-arguments-must-be-atoms constraint.
-
\begin{code}
-data CoreArgOrExpr
- = AnArg CoreArg
- | AnExpr CoreExpr
+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
-mkCoApps :: CoreExpr -> [CoreArgOrExpr] -> UniqSM CoreExpr
-mkCoCon :: Id -> [CoreArgOrExpr] -> UniqSM CoreExpr
-mkCoPrim :: PrimOp -> [CoreArgOrExpr] -> UniqSM CoreExpr
+ go n (Note _ e) = go n e
-mkCoApps fun args = co_thing (mkGenApp fun) args
-mkCoCon con args = co_thing (Con con) args
-mkCoPrim op args = co_thing (Prim op) args
+ 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
-co_thing :: ([CoreArg] -> CoreExpr)
- -> [CoreArgOrExpr]
- -> UniqSM CoreExpr
+ 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
-co_thing thing arg_exprs
- = mapAndUnzipUs expr_to_arg arg_exprs `thenUs` \ (args, maybe_binds) ->
- returnUs (mkCoLetsUnboxedToCase (catMaybes maybe_binds) (thing args))
- where
- expr_to_arg :: CoreArgOrExpr
- -> UniqSM (CoreArg, Maybe CoreBinding)
-
- expr_to_arg (AnArg arg) = returnUs (arg, Nothing)
- expr_to_arg (AnExpr (Var v)) = returnUs (VarArg v, Nothing)
- expr_to_arg (AnExpr (Lit l)) = returnUs (LitArg l, Nothing)
- expr_to_arg (AnExpr other_expr)
- = let
- e_ty = coreExprType other_expr
- in
- getUnique `thenUs` \ uniq ->
- let
- new_var = mkSysLocal SLIT("a") uniq e_ty noSrcLoc
- in
- returnUs (VarArg new_var, Just (NonRec new_var other_expr))
+ go n (App fun (Type _)) = go n fun -- Ignore type args
+ go n (App fun arg) = go (n+1) fun
+
+ go n (Var f) | isBottomingId f = BottomForm
+ go 0 (Var f) = VarForm
+ go n (Var f) | n < arityLowerBound (getIdArity f) = ValueForm
+ | otherwise = OtherForm
\end{code}
-\begin{code}
-argToExpr ::
- GenCoreArg val_occ flexi -> GenCoreExpr val_bdr val_occ flexi
+@exprIsTrivial@ is true of expressions we are unconditionally
+ happy to duplicate; simple variables and constants,
+ and type applications.
+
+@exprIsDupable@ is true of expressions that can be duplicated at a modest
+ cost in space, but without duplicating any work.
+
+
+@exprIsBottom@ is true of expressions that are guaranteed to diverge
-argToExpr (VarArg v) = Var v
-argToExpr (LitArg lit) = Lit lit
+
+\begin{code}
+exprIsTrivial (Type _) = 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}
-All the following functions operate on binders, perform a uniform
-transformation on them; ie. the function @(\ x -> (x,False))@
-annotates all binders with False.
\begin{code}
-unTagBinders :: GenCoreExpr (Id,tag) bdee flexi -> GenCoreExpr Id bdee flexi
-unTagBinders expr = bop_expr fst expr
+exprIsDupable (Type _) = True
+exprIsDupable (Con con args) = conIsCheap con &&
+ all exprIsDupable args &&
+ valArgCount args <= dupAppSize
+
+exprIsDupable (Note _ e) = exprIsDupable e
+exprIsDupable expr = case collectArgs expr of
+ (Var v, args) -> n_val_args == 0 ||
+ (n_val_args < fun_arity &&
+ all exprIsDupable args &&
+ n_val_args <= dupAppSize)
+ where
+ n_val_args = valArgCount args
+ fun_arity = arityLowerBound (getIdArity v)
+
+ _ -> False
+
+dupAppSize :: Int
+dupAppSize = 4 -- Size of application we are prepared to duplicate
+\end{code}
-unTagBindersAlts :: GenCoreCaseAlts (Id,tag) bdee flexi -> GenCoreCaseAlts Id bdee flexi
-unTagBindersAlts alts = bop_alts fst alts
+@exprIsCheap@ looks at a Core expression and returns \tr{True} if
+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:
+
+ * case e of
+ pi -> ei
+
+ where e, and all the ei are cheap; and
+
+ * let x = e
+ in b
+
+ where e and b are cheap; and
+
+ * op x1 ... xn
+
+ 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
+
+ (Var f, _) | isBottomingId f -> True -- Application of a function which
+ -- always gives bottom; we treat this as
+ -- a WHNF, because it certainly doesn't
+ -- need to be shared!
+
+ (Var f, args) ->
+ let
+ num_val_args = valArgCount args
+ in
+ num_val_args == 0 || -- Just a type application of
+ -- a variable (f t1 t2 t3)
+ -- counts as WHNF
+ num_val_args < arityLowerBound (getIdArity f)
+
+ _ -> False
\end{code}
+
\begin{code}
-bop_expr :: (a -> b) -> GenCoreExpr a bdee flexi -> GenCoreExpr b bdee flexi
-
-bop_expr f (Var b) = Var b
-bop_expr f (Lit lit) = Lit lit
-bop_expr f (Con con args) = Con con args
-bop_expr f (Prim op args) = Prim op args
-bop_expr f (Lam binder expr) = Lam (bop_binder f binder) (bop_expr f expr)
-bop_expr f (App expr arg) = App (bop_expr f expr) arg
-bop_expr f (Note note expr) = Note note (bop_expr f expr)
-bop_expr f (Let bind expr) = Let (bop_bind f bind) (bop_expr f expr)
-bop_expr f (Case expr alts) = Case (bop_expr f expr) (bop_alts f alts)
-
-bop_binder f (ValBinder v) = ValBinder (f v)
-bop_binder f (TyBinder t) = TyBinder t
-
-bop_bind f (NonRec b e) = NonRec (f b) (bop_expr f e)
-bop_bind f (Rec pairs) = Rec [(f b, bop_expr f e) | (b, e) <- pairs]
-
-bop_alts f (AlgAlts alts deflt)
- = AlgAlts [ (con, [f b | b <- binders], bop_expr f e)
- | (con, binders, e) <- alts ]
- (bop_deflt f deflt)
-
-bop_alts f (PrimAlts alts deflt)
- = PrimAlts [ (lit, bop_expr f e) | (lit, e) <- alts ]
- (bop_deflt f deflt)
-
-bop_deflt f (NoDefault) = NoDefault
-bop_deflt f (BindDefault b expr) = BindDefault (f b) (bop_expr f expr)
+exprIsBottom :: CoreExpr -> Bool -- True => definitely bottom
+exprIsBottom (Note _ e) = exprIsBottom e
+exprIsBottom (Let _ e) = exprIsBottom e
+exprIsBottom (Case e _ _) = exprIsBottom e -- Just chek the scrut
+exprIsBottom (Con _ _) = False
+exprIsBottom (App e _) = exprIsBottom e
+exprIsBottom (Var v) = isBottomingId v
+exprIsBottom (Lam _ _) = False
\end{code}
-OLD (but left here because of the nice example): @singleAlt@ checks
-whether a bunch of case alternatives is actually just one alternative.
-It specifically {\em ignores} alternatives which consist of just a
-call to @error@, because they won't result in any code duplication.
+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.
+
+We treat applications of buildId and augmentId as honorary WHNFs, because we
+want them to get exposed
-Example:
-\begin{verbatim}
- case (case <something> of
- True -> <rhs>
- False -> error "Foo") of
- <alts>
+\begin{code}
+exprIsWHNF :: CoreExpr -> Bool -- True => Variable, value-lambda, constructor, PAP
+exprIsWHNF (Type ty) = True -- Types are honorary WHNFs; 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
+\end{code}
-===>
+I don't like this function but I'n not confidnt enough to change it.
- case <something> of
- True -> case <rhs> of
- <alts>
- False -> case error "Foo" of
- <alts>
+\begin{code}
+squashableDictishCcExpr :: CostCentre -> Expr b f -> Bool
+squashableDictishCcExpr cc expr
+ | isDictCC cc = False -- that was easy...
+ | otherwise = squashable expr
+ where
+ squashable (Var _) = True
+ squashable (Con _ _) = True -- I think so... WDP 94/09
+ squashable (App f a)
+ | isTypeArg a = squashable f
+ squashable other = False
+\end{code}
-===>
- case <something> of
- True -> case <rhs> of
- <alts>
- False -> error "Foo"
-\end{verbatim}
-Notice that the \tr{<alts>} don't get duplicated.
+@cheapEqExpr@ is a cheap equality test which bales out fast!
+ True => definitely equal
+ False => may or may not be equal
\begin{code}
-nonErrorRHSs :: GenCoreCaseAlts a Id Unused -> [GenCoreExpr a Id Unused]
+cheapEqExpr :: Expr b f -> Expr b f -> Bool
-nonErrorRHSs alts
- = filter not_error_app (find_rhss alts)
- where
- find_rhss (AlgAlts as deflt) = [rhs | (_,_,rhs) <- as] ++ deflt_rhs deflt
- find_rhss (PrimAlts as deflt) = [rhs | (_,rhs) <- as] ++ deflt_rhs deflt
+cheapEqExpr (Var v1) (Var v2) = v1==v2
+cheapEqExpr (Con con1 args1) (Con con2 args2)
+ = con1 == con2 &&
+ and (zipWithEqual "cheapEqExpr" cheapEqExpr args1 args2)
+
+cheapEqExpr (App f1 a1) (App f2 a2)
+ = f1 `cheapEqExpr` f2 && a1 `cheapEqExpr` a2
- deflt_rhs NoDefault = []
- deflt_rhs (BindDefault _ rhs) = [rhs]
+cheapEqExpr (Type t1) (Type t2) = t1 == t2
- not_error_app rhs
- = case (maybeErrorApp rhs Nothing) of
- Just _ -> False
- Nothing -> True
+cheapEqExpr _ _ = False
\end{code}
-maybeErrorApp checks whether an expression is of the form
- error ty args
+%************************************************************************
+%* *
+\section{Finding the free variables of an expression}
+%* *
+%************************************************************************
-If so, it returns
+This function simply finds the free variables of an expression.
+So far as type variables are concerned, it only finds tyvars that are
- Just (error ty' args)
+ * free in type arguments,
+ * free in the type of a binder,
-where ty' is supplied as an argument to maybeErrorApp.
+but not those that are free in the type of variable occurrence.
-Here's where it is useful:
+\begin{code}
+exprFreeVars :: CoreExpr -> IdOrTyVarSet -- Find all locally-defined free Ids or tyvars
+exprFreeVars = exprSomeFreeVars isLocallyDefined
- case (error ty "Foo" e1 e2) of <alts>
- ===>
- error ty' "Foo"
+exprSomeFreeVars :: InterestingVarFun -- Says which Vars are interesting
+ -> CoreExpr
+ -> IdOrTyVarSet
+exprSomeFreeVars fv_cand e = expr_fvs e fv_cand emptyVarSet
+
+type InterestingVarFun = IdOrTyVar -> Bool -- True <=> interesting
+\end{code}
-where ty' is the type of any of the alternatives. You might think
-this never occurs, but see the comments on the definition of
-@singleAlt@.
-Note: we *avoid* the case where ty' might end up as a primitive type:
-this is very uncool (totally wrong).
+\begin{code}
+type FV = InterestingVarFun
+ -> IdOrTyVarSet -- In scope
+ -> IdOrTyVarSet -- Free vars
-NOTICE: in the example above we threw away e1 and e2, but not the
-string "Foo". How did we know to do that?
+union :: FV -> FV -> FV
+union fv1 fv2 fv_cand in_scope = fv1 fv_cand in_scope `unionVarSet` fv2 fv_cand in_scope
-Answer: for now anyway, we only handle the case of a function whose
-type is of form
+noVars :: FV
+noVars fv_cand in_scope = emptyVarSet
- bottomingFn :: forall a. t1 -> ... -> tn -> a
- ^---------------------^ NB!
+oneVar :: IdOrTyVar -> FV
+oneVar var fv_cand in_scope
+ | keep_it fv_cand in_scope var = unitVarSet var
+ | otherwise = emptyVarSet
-Furthermore, we only count a bottomingApp if the function is applied
-to more than n args. If so, we transform:
+someVars :: IdOrTyVarSet -> FV
+someVars vars fv_cand in_scope
+ = filterVarSet (keep_it fv_cand in_scope) vars
- bottomingFn ty e1 ... en en+1 ... em
-to
- bottomingFn ty' e1 ... en
+keep_it fv_cand in_scope var
+ | var `elemVarSet` in_scope = False
+ | fv_cand var = True
+ | otherwise = False
-That is, we discard en+1 .. em
-\begin{code}
-maybeErrorApp
- :: GenCoreExpr a Id Unused -- Expr to look at
- -> Maybe Type -- Just ty => a result type *already cloned*;
- -- Nothing => don't know result ty; we
- -- *pretend* that the result ty won't be
- -- primitive -- somebody later must
- -- ensure this.
- -> Maybe (GenCoreExpr b Id Unused)
-
-maybeErrorApp expr result_ty_maybe
- = case (collectArgs expr) of
- (Var fun, [ty], other_args)
- | isBottomingId fun
- && maybeToBool result_ty_maybe -- we *know* the result type
- -- (otherwise: live a fairy-tale existence...)
- && not (isUnpointedType result_ty) ->
-
- case (splitSigmaTy (idType fun)) of
- ([tyvar], [], tau_ty) ->
- case (splitFunTys tau_ty) of { (arg_tys, res_ty) ->
- let
- n_args_to_keep = length arg_tys
- args_to_keep = take n_args_to_keep other_args
- in
- if (res_ty == mkTyVarTy tyvar)
- && n_args_to_keep <= length other_args
- then
- -- Phew! We're in business
- Just (mkGenApp (Var fun) (TyArg result_ty : args_to_keep))
- else
- Nothing
- }
-
- other -> Nothing -- Function type wrong shape
- other -> Nothing
+addBndr :: CoreBndr -> FV -> FV
+addBndr bndr fv fv_cand in_scope
+ | isId bndr = inside_fvs `unionVarSet` someVars (idFreeVars bndr) fv_cand in_scope
+ | otherwise = inside_fvs
where
- Just result_ty = result_ty_maybe
+ inside_fvs = fv fv_cand (in_scope `extendVarSet` bndr)
+
+addBndrs :: [CoreBndr] -> FV -> FV
+addBndrs bndrs fv = foldr addBndr fv bndrs
\end{code}
+
\begin{code}
-squashableDictishCcExpr :: CostCentre -> GenCoreExpr a b c -> Bool
+expr_fvs :: CoreExpr -> FV
-squashableDictishCcExpr cc expr
- = if not (isDictCC cc) then
- False -- that was easy...
- else
- squashable expr -- note: quite like the "atomic_rhs" stuff in simplifier
+expr_fvs (Type ty) = someVars (tyVarsOfType ty)
+expr_fvs (Var var) = oneVar var
+expr_fvs (Con con args) = foldr (union . expr_fvs) noVars args
+expr_fvs (Note _ expr) = expr_fvs expr
+expr_fvs (App fun arg) = expr_fvs fun `union` expr_fvs arg
+expr_fvs (Lam bndr body) = addBndr bndr (expr_fvs body)
+
+expr_fvs (Case scrut bndr alts)
+ = expr_fvs scrut `union` addBndr bndr (foldr (union. alt_fvs) noVars alts)
where
- squashable (Var _) = True
- squashable (Con _ _) = True -- I think so... WDP 94/09
- squashable (Prim _ _) = True -- ditto
- squashable (App f a)
- | notValArg a = squashable f
- squashable other = False
+ alt_fvs (con, bndrs, rhs) = addBndrs bndrs (expr_fvs rhs)
+
+expr_fvs (Let (NonRec bndr rhs) body)
+ = expr_fvs rhs `union` addBndr bndr (expr_fvs body)
+
+expr_fvs (Let (Rec pairs) body)
+ = addBndrs bndrs (foldr (union . expr_fvs) (expr_fvs body) rhss)
+ where
+ (bndrs,rhss) = unzip pairs
\end{code}
we regard an Id's specialisations as free in the Id's definition.
\begin{code}
-idSpecVars :: Id -> [Id]
+idSpecVars :: Id -> IdOrTyVarSet
idSpecVars id
- = map get_spec (specEnvValues (getIdSpecialisation id))
+ = foldr (unionVarSet . spec_item_fvs)
+ emptyVarSet
+ (specEnvToList (getIdSpecialisation id))
where
- -- get_spec is another cheapo function like dictRhsFVs
- -- It knows what these specialisation temlates look like,
- -- and just goes for the jugular
- get_spec (App f _) = get_spec f
- get_spec (Lam _ b) = get_spec b
- get_spec (Var v) = v
+ spec_item_fvs (tyvars, tys, rhs) = foldl delVarSet
+ (tyVarsOfTypes tys `unionVarSet` exprFreeVars rhs)
+ tyvars
+
+idFreeVars :: Id -> IdOrTyVarSet
+idFreeVars id = idSpecVars id `unionVarSet` idFreeTyVars id
\end{code}
+
+
+%************************************************************************
+%* *
+\section{Substitution}
+%* *
+%************************************************************************
+
+This expression substituter deals correctly with name capture, much
+like Type.substTy.
+
+BUT NOTE that substExpr silently discards the
+ unfolding, and
+ spec env
+IdInfo attached to any binders in the expression. It's quite
+tricky to do them 'right' in the case of mutually recursive bindings,
+and so far has proved unnecessary.
+
+\begin{code}
+substExpr :: TyVarSubst -> IdSubst -- Substitution
+ -> IdOrTyVarSet -- Superset of in-scope
+ -> CoreExpr
+ -> CoreExpr
+
+substExpr te ve in_scope expr = subst_expr (te, ve, in_scope) expr
+
+subst_expr env@(te, ve, in_scope) expr
+ = go expr
+ where
+ go (Var v) = case lookupVarEnv ve v of
+ Just (Done e')
+ -> e'
+
+ Just (SubstMe e' te' ve')
+ -> subst_expr (te', ve', in_scope) e'
+
+ Nothing -> case lookupVarSet in_scope v of
+ Just v' -> Var v'
+ Nothing -> Var v
+ -- NB: we look up in the in_scope set because the variable
+ -- there may have more info. In particular, when substExpr
+ -- is called from the simplifier, the type inside the *occurrences*
+ -- of a variable may not be right; we should replace it with the
+ -- binder, from the in_scope set.
+
+ go (Type ty) = Type (go_ty ty)
+ go (Con con args) = Con con (map go args)
+ go (App fun arg) = App (go fun) (go arg)
+ go (Note note e) = Note (go_note note) (go e)
+
+ go (Lam bndr body) = Lam bndr' (subst_expr env' body)
+ where
+ (env', bndr') = go_bndr env bndr
+
+ go (Let (NonRec bndr rhs) body) = Let (NonRec bndr' (go rhs)) (subst_expr env' body)
+ where
+ (env', bndr') = go_bndr env bndr
+
+ go (Let (Rec pairs) body) = Let (Rec pairs') (subst_expr env' body)
+ where
+ (ve', in_scope', _, bndrs')
+ = substIds clone_fn te ve in_scope undefined (map fst pairs)
+ env' = (te, ve', in_scope')
+ pairs' = bndrs' `zip` rhss'
+ rhss' = map (subst_expr env' . snd) pairs
+
+ go (Case scrut bndr alts) = Case (go scrut) bndr' (map (go_alt env') alts)
+ where
+ (env', bndr') = go_bndr env bndr
+
+ go_alt env (con, bndrs, rhs) = (con, bndrs', subst_expr env' rhs)
+ where
+ (env', bndrs') = mapAccumL go_bndr env bndrs
+
+ go_note (Coerce ty1 ty2) = Coerce (go_ty ty1) (go_ty ty2)
+ go_note note = note
+
+ go_ty ty = fullSubstTy te in_scope ty
+
+ go_bndr (te, ve, in_scope) bndr
+ | isTyVar bndr
+ = case substTyVar te in_scope bndr of
+ (te', in_scope', bndr') -> ((te', ve, in_scope'), bndr')
+
+ | otherwise
+ = case substId clone_fn te ve in_scope undefined bndr of
+ (ve', in_scope', _, bndr') -> ((te, ve', in_scope'), bndr')
+
+
+ clone_fn in_scope _ bndr
+ | bndr `elemVarSet` in_scope = Just (uniqAway in_scope bndr, undefined)
+ | otherwise = Nothing
+
+\end{code}
+
+Substituting in binders is a rather tricky part of the whole compiler.
+
+\begin{code}
+substIds :: (IdOrTyVarSet -> us -> Id -> Maybe (us, Id)) -- Cloner
+ -> TyVarSubst -> IdSubst -> IdOrTyVarSet -- Usual stuff
+ -> us -- Unique supply
+ -> [Id]
+ -> (IdSubst, IdOrTyVarSet, -- New id_subst, in_scope
+ us, -- New unique supply
+ [Id])
+
+substIds clone_fn ty_subst id_subst in_scope us []
+ = (id_subst, in_scope, us, [])
+
+substIds clone_fn ty_subst id_subst in_scope us (id:ids)
+ = case (substId clone_fn ty_subst id_subst in_scope us id) of {
+ (id_subst', in_scope', us', id') ->
+
+ case (substIds clone_fn ty_subst id_subst' in_scope' us' ids) of {
+ (id_subst'', in_scope'', us'', ids') ->
+
+ (id_subst'', in_scope'', us'', id':ids')
+ }}
+
+
+substId :: (IdOrTyVarSet -> us -> Id -> Maybe (us, Id)) -- Cloner
+ -> TyVarSubst -> IdSubst -> IdOrTyVarSet -- Usual stuff
+ -> us -- Unique supply
+ -> Id
+ -> (IdSubst, IdOrTyVarSet, -- New id_subst, in_scope
+ us, -- New unique supply
+ Id)
+
+-- Returns an Id with empty unfolding and spec-env.
+-- It's up to the caller to sort these out.
+
+substId clone_fn
+ ty_subst id_subst in_scope
+ us id
+ | old_id_will_do
+ -- No need to clone, but we *must* zap any current substitution
+ -- for the variable. For example:
+ -- (\x.e) with id_subst = [x |-> e']
+ -- Here we must simply zap the substitution for x
+ = (delVarEnv id_subst id, extendVarSet in_scope id, us, id)
+
+ | otherwise
+ = (extendVarEnv id_subst id (Done (Var new_id)),
+ extendVarSet in_scope new_id,
+ new_us,
+ new_id)
+ where
+ id_ty = idType id
+ old_id_will_do = old1 && old2 && old3 && {-old4 && -}not cloned
+
+ -- id1 has its type zapped
+ (id1,old1) | isEmptyVarEnv ty_subst
+ || isEmptyVarSet (tyVarsOfType id_ty) = (id, True)
+ | otherwise = (setIdType id ty', False)
+
+ ty' = fullSubstTy ty_subst in_scope id_ty
+
+ -- id2 has its SpecEnv zapped
+ -- It's filled in later by
+ (id2,old2) | isEmptySpecEnv spec_env = (id1, True)
+ | otherwise = (setIdSpecialisation id1 emptySpecEnv, False)
+ spec_env = getIdSpecialisation id
+
+ -- id3 has its Unfolding zapped
+ -- This is very important; occasionally a let-bound binder is used
+ -- as a binder in some lambda, in which case its unfolding is utterly
+ -- bogus. Also the unfolding uses old binders so if we left it we'd
+ -- have to substitute it. Much better simply to give the Id a new
+ -- unfolding each time, which is what the simplifier does.
+ (id3,old3) | hasUnfolding (getIdUnfolding id) = (id2 `setIdUnfolding` noUnfolding, False)
+ | otherwise = (id2, True)
+
+ -- new_id is cloned if necessary
+ (new_us, new_id, cloned) = case clone_fn in_scope us id3 of
+ Nothing -> (us, id3, False)
+ Just (us', id') -> (us', id', True)
+
+ -- new_id_bndr has its Inline info neutered. We must forget about whether it
+ -- was marked safe-to-inline, because that isn't necessarily true in
+ -- the simplified expression. We do this for the *binder* which will
+ -- be used at the binding site, but we *dont* do it for new_id, which
+ -- is put into the in_scope env. Why not? Because the in_scope env
+ -- carries down the occurrence information to usage sites!
+ --
+ -- Net result: post-simplification, occurrences may have over-optimistic
+ -- occurrence info, but binders won't.
+{- (new_id_bndr, old4)
+ = case getInlinePragma id of
+ ICanSafelyBeINLINEd _ _ -> (setInlinePragma new_id NoInlinePragInfo, False)
+ other -> (new_id, True)
+-}
+\end{code}
+
+
+
+
+
projects / ghc-hetmet.git / blobdiff