X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FcoreSyn%2FCoreSubst.lhs;h=acf17e3c124d29a4562df5ce734de2754dabed7f;hp=addda3ad2b6612f9bc956b5467c61ff9e24986cb;hb=a1fae73a83665d7b9134509e80d34ff69a009cc7;hpb=2c969eccaa815888434143c9084b8ab855586dc6 diff --git a/compiler/coreSyn/CoreSubst.lhs b/compiler/coreSyn/CoreSubst.lhs index addda3a..acf17e3 100644 --- a/compiler/coreSyn/CoreSubst.lhs +++ b/compiler/coreSyn/CoreSubst.lhs @@ -1,53 +1,72 @@ % +% (c) The University of Glasgow 2006 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % -\section[CoreUtils]{Utility functions on @Core@ syntax} + +Utility functions on @Core@ syntax \begin{code} module CoreSubst ( - -- Substitution stuff + -- * Main data types Subst, TvSubstEnv, IdSubstEnv, InScopeSet, - deShadowBinds, - substTy, substExpr, substSpec, substWorker, - lookupIdSubst, lookupTvSubst, + -- ** Substituting into expressions and related types + deShadowBinds, substSpec, substRulesForImportedIds, + substTy, substCo, substExpr, substExprSC, substBind, substBindSC, + substUnfolding, substUnfoldingSC, + substUnfoldingSource, lookupIdSubst, lookupTvSubst, lookupCvSubst, substIdOcc, - emptySubst, mkEmptySubst, mkSubst, substInScope, isEmptySubst, + -- ** Operations on substitutions + emptySubst, mkEmptySubst, mkSubst, mkOpenSubst, substInScope, isEmptySubst, extendIdSubst, extendIdSubstList, extendTvSubst, extendTvSubstList, - extendInScope, extendInScopeIds, - isInScope, + extendCvSubst, extendCvSubstList, + extendSubst, extendSubstList, extendSubstWithVar, zapSubstEnv, + addInScopeSet, extendInScope, extendInScopeList, extendInScopeIds, + isInScope, setInScope, + delBndr, delBndrs, - -- Binders + -- ** Substituting and cloning binders substBndr, substBndrs, substRecBndrs, - cloneIdBndr, cloneIdBndrs, cloneRecIdBndrs + cloneIdBndr, cloneIdBndrs, cloneRecIdBndrs, + + -- ** Simple expression optimiser + simpleOptPgm, simpleOptExpr, simpleOptExprWith ) where #include "HsVersions.h" -import CoreSyn ( Expr(..), Bind(..), Note(..), CoreExpr, CoreBind, - CoreRule(..), hasUnfolding, noUnfolding - ) -import CoreFVs ( exprFreeVars ) -import CoreUtils ( exprIsTrivial ) +import CoreSyn +import CoreFVs +import CoreUtils +import OccurAnal( occurAnalyseExpr, occurAnalysePgm ) + +import qualified Type +import qualified Coercion -import qualified Type ( substTy, substTyVarBndr ) -import Type ( Type, tyVarsOfType, TvSubstEnv, TvSubst(..), mkTyVarTy ) + -- We are defining local versions +import Type hiding ( substTy, extendTvSubst, extendTvSubstList + , isInScope, substTyVarBndr ) +import Coercion hiding ( substTy, substCo, extendTvSubst, substTyVarBndr, substCoVarBndr ) + +import OptCoercion ( optCoercion ) +import PprCore ( pprCoreBindings ) import VarSet import VarEnv -import Var ( setVarUnique, isId ) -import Id ( idType, setIdType, maybeModifyIdInfo, isLocalId ) -import IdInfo ( IdInfo, SpecInfo(..), specInfo, setSpecInfo, isEmptySpecInfo, - unfoldingInfo, setUnfoldingInfo, seqSpecInfo, - WorkerInfo(..), workerExists, workerInfo, setWorkerInfo - ) -import Unique ( Unique ) -import UniqSupply ( UniqSupply, uniqFromSupply, uniqsFromSupply ) -import Var ( Var, Id, TyVar, isTyVar ) -import Maybes ( orElse ) +import Id +import Name ( Name ) +import Var +import IdInfo +import Unique +import UniqSupply +import Maybes +import ErrUtils +import DynFlags ( DynFlags, DynFlag(..) ) +import BasicTypes ( isAlwaysActive ) import Outputable import PprCore () -- Instances -import Util ( mapAccumL ) -import FastTypes +import FastString + +import Data.List \end{code} @@ -58,110 +77,255 @@ import FastTypes %************************************************************************ \begin{code} +-- | A substitution environment, containing both 'Id' and 'TyVar' substitutions. +-- +-- Some invariants apply to how you use the substitution: +-- +-- 1. #in_scope_invariant# The in-scope set contains at least those 'Id's and 'TyVar's that will be in scope /after/ +-- applying the substitution to a term. Precisely, the in-scope set must be a superset of the free vars of the +-- substitution range that might possibly clash with locally-bound variables in the thing being substituted in. +-- +-- 2. #apply_once# You may apply the substitution only /once/ +-- +-- There are various ways of setting up the in-scope set such that the first of these invariants hold: +-- +-- * Arrange that the in-scope set really is all the things in scope +-- +-- * Arrange that it's the free vars of the range of the substitution +-- +-- * Make it empty, if you know that all the free vars of the substitution are fresh, and hence can't possibly clash data Subst - = Subst InScopeSet -- Variables in in scope (both Ids and TyVars) - IdSubstEnv -- Substitution for Ids - TvSubstEnv -- Substitution for TyVars - - -- INVARIANT 1: The (domain of the) in-scope set is a superset - -- of the free vars of the range of the substitution - -- that might possibly clash with locally-bound variables - -- in the thing being substituted in. + = Subst InScopeSet -- Variables in in scope (both Ids and TyVars) /after/ + -- applying the substitution + IdSubstEnv -- Substitution for Ids + TvSubstEnv -- Substitution from TyVars to Types + CvSubstEnv -- Substitution from TyCoVars to Coercions + + -- INVARIANT 1: See #in_scope_invariant# -- This is what lets us deal with name capture properly -- It's a hard invariant to check... - -- There are various ways of causing it to happen: - -- - arrange that the in-scope set really is all the things in scope - -- - arrange that it's the free vars of the range of the substitution - -- - make it empty because all the free vars of the subst are fresh, - -- and hence can't possibly clash.a -- - -- INVARIANT 2: The substitution is apply-once; see notes with + -- INVARIANT 2: The substitution is apply-once; see Note [Apply once] with -- Types.TvSubstEnv + -- + -- INVARIANT 3: See Note [Extending the Subst] +\end{code} + +Note [Extending the Subst] +~~~~~~~~~~~~~~~~~~~~~~~~~~ +For a core Subst, which binds Ids as well, we make a different choice for Ids +than we do for TyVars. + +For TyVars, see Note [Extending the TvSubst] with Type.TvSubstEnv + +For Ids, we have a different invariant + The IdSubstEnv is extended *only* when the Unique on an Id changes + Otherwise, we just extend the InScopeSet + +In consequence: + +* If the TvSubstEnv and IdSubstEnv are both empty, substExpr would be a + no-op, so substExprSC ("short cut") does nothing. + + However, substExpr still goes ahead and substitutes. Reason: we may + want to replace existing Ids with new ones from the in-scope set, to + avoid space leaks. + +* In substIdBndr, we extend the IdSubstEnv only when the unique changes + +* If the CvSubstEnv, TvSubstEnv and IdSubstEnv are all empty, + substExpr does nothing (Note that the above rule for substIdBndr + maintains this property. If the incoming envts are both empty, then + substituting the type and IdInfo can't change anything.) + +* In lookupIdSubst, we *must* look up the Id in the in-scope set, because + it may contain non-trivial changes. Example: + (/\a. \x:a. ...x...) Int + We extend the TvSubstEnv with [a |-> Int]; but x's unique does not change + so we only extend the in-scope set. Then we must look up in the in-scope + set when we find the occurrence of x. + +* The requirement to look up the Id in the in-scope set means that we + must NOT take no-op short cut when the IdSubst is empty. + We must still look up every Id in the in-scope set. + +* (However, we don't need to do so for expressions found in the IdSubst + itself, whose range is assumed to be correct wrt the in-scope set.) + +Why do we make a different choice for the IdSubstEnv than the +TvSubstEnv and CvSubstEnv? + +* For Ids, we change the IdInfo all the time (e.g. deleting the + unfolding), and adding it back later, so using the TyVar convention + would entail extending the substitution almost all the time + +* The simplifier wants to look up in the in-scope set anyway, in case it + can see a better unfolding from an enclosing case expression + +* For TyVars, only coercion variables can possibly change, and they are + easy to spot +\begin{code} +-- | An environment for substituting for 'Id's type IdSubstEnv = IdEnv CoreExpr ---------------------------- isEmptySubst :: Subst -> Bool -isEmptySubst (Subst _ id_env tv_env) = isEmptyVarEnv id_env && isEmptyVarEnv tv_env +isEmptySubst (Subst _ id_env tv_env cv_env) + = isEmptyVarEnv id_env && isEmptyVarEnv tv_env && isEmptyVarEnv cv_env emptySubst :: Subst -emptySubst = Subst emptyInScopeSet emptyVarEnv emptyVarEnv +emptySubst = Subst emptyInScopeSet emptyVarEnv emptyVarEnv emptyVarEnv mkEmptySubst :: InScopeSet -> Subst -mkEmptySubst in_scope = Subst in_scope emptyVarEnv emptyVarEnv - -mkSubst :: InScopeSet -> TvSubstEnv -> IdSubstEnv -> Subst -mkSubst in_scope tvs ids = Subst in_scope ids tvs - --- getTvSubst :: Subst -> TvSubst --- getTvSubst (Subst in_scope _ tv_env) = TvSubst in_scope tv_env +mkEmptySubst in_scope = Subst in_scope emptyVarEnv emptyVarEnv emptyVarEnv --- getTvSubstEnv :: Subst -> TvSubstEnv --- getTvSubstEnv (Subst _ _ tv_env) = tv_env --- --- setTvSubstEnv :: Subst -> TvSubstEnv -> Subst --- setTvSubstEnv (Subst in_scope ids _) tvs = Subst in_scope ids tvs +mkSubst :: InScopeSet -> TvSubstEnv -> CvSubstEnv -> IdSubstEnv -> Subst +mkSubst in_scope tvs cvs ids = Subst in_scope ids tvs cvs +-- | Find the in-scope set: see "CoreSubst#in_scope_invariant" substInScope :: Subst -> InScopeSet -substInScope (Subst in_scope _ _) = in_scope +substInScope (Subst in_scope _ _ _) = in_scope --- zapSubstEnv :: Subst -> Subst --- zapSubstEnv (Subst in_scope _ _) = Subst in_scope emptyVarEnv emptyVarEnv +-- | Remove all substitutions for 'Id's and 'Var's that might have been built up +-- while preserving the in-scope set +zapSubstEnv :: Subst -> Subst +zapSubstEnv (Subst in_scope _ _ _) = Subst in_scope emptyVarEnv emptyVarEnv emptyVarEnv --- ToDo: add an ASSERT that fvs(subst-result) is already in the in-scope set +-- | Add a substitution for an 'Id' to the 'Subst': you must ensure that the in-scope set is +-- such that the "CoreSubst#in_scope_invariant" is true after extending the substitution like this extendIdSubst :: Subst -> Id -> CoreExpr -> Subst -extendIdSubst (Subst in_scope ids tvs) v r = Subst in_scope (extendVarEnv ids v r) tvs +-- ToDo: add an ASSERT that fvs(subst-result) is already in the in-scope set +extendIdSubst (Subst in_scope ids tvs cvs) v r = Subst in_scope (extendVarEnv ids v r) tvs cvs +-- | Adds multiple 'Id' substitutions to the 'Subst': see also 'extendIdSubst' extendIdSubstList :: Subst -> [(Id, CoreExpr)] -> Subst -extendIdSubstList (Subst in_scope ids tvs) prs = Subst in_scope (extendVarEnvList ids prs) tvs +extendIdSubstList (Subst in_scope ids tvs cvs) prs = Subst in_scope (extendVarEnvList ids prs) tvs cvs +-- | Add a substitution for a 'TyVar' to the 'Subst': you must ensure that the in-scope set is +-- such that the "CoreSubst#in_scope_invariant" is true after extending the substitution like this extendTvSubst :: Subst -> TyVar -> Type -> Subst -extendTvSubst (Subst in_scope ids tvs) v r = Subst in_scope ids (extendVarEnv tvs v r) +extendTvSubst (Subst in_scope ids tvs cvs) v r = Subst in_scope ids (extendVarEnv tvs v r) cvs +-- | Adds multiple 'TyVar' substitutions to the 'Subst': see also 'extendTvSubst' extendTvSubstList :: Subst -> [(TyVar,Type)] -> Subst -extendTvSubstList (Subst in_scope ids tvs) prs = Subst in_scope ids (extendVarEnvList tvs prs) - -lookupIdSubst :: Subst -> Id -> CoreExpr -lookupIdSubst (Subst in_scope ids tvs) v +extendTvSubstList (Subst in_scope ids tvs cvs) prs = Subst in_scope ids (extendVarEnvList tvs prs) cvs + +-- | Add a substitution from a 'TyCoVar' to a 'Coercion' to the 'Subst': you must ensure that the in-scope set is +-- such that the "CoreSubst#in_scope_invariant" is true after extending the substitution like this +extendCvSubst :: Subst -> TyCoVar -> Coercion -> Subst +extendCvSubst (Subst in_scope ids tvs cvs) v r = Subst in_scope ids tvs (extendVarEnv cvs v r) + +-- | Adds multiple 'TyCoVar' -> 'Coercion' substitutions to the +-- 'Subst': see also 'extendCvSubst' +extendCvSubstList :: Subst -> [(TyCoVar,Coercion)] -> Subst +extendCvSubstList (Subst in_scope ids tvs cvs) prs = Subst in_scope ids tvs (extendVarEnvList cvs prs) + +-- | Add a substitution appropriate to the thing being substituted +-- (whether an expression, type, or coercion). See also +-- 'extendIdSubst', 'extendTvSubst', and 'extendCvSubst'. +extendSubst :: Subst -> Var -> CoreArg -> Subst +extendSubst subst var arg + = case arg of + Type ty -> ASSERT( isTyVar var ) extendTvSubst subst var ty + Coercion co -> ASSERT( isCoVar var ) extendCvSubst subst var co + _ -> ASSERT( isId var ) extendIdSubst subst var arg + +extendSubstWithVar :: Subst -> Var -> Var -> Subst +extendSubstWithVar subst v1 v2 + | isTyVar v1 = ASSERT( isTyVar v2 ) extendTvSubst subst v1 (mkTyVarTy v2) + | isCoVar v1 = ASSERT( isCoVar v2 ) extendCvSubst subst v1 (mkCoVarCo v2) + | otherwise = ASSERT( isId v2 ) extendIdSubst subst v1 (Var v2) + +-- | Add a substitution as appropriate to each of the terms being +-- substituted (whether expressions, types, or coercions). See also +-- 'extendSubst'. +extendSubstList :: Subst -> [(Var,CoreArg)] -> Subst +extendSubstList subst [] = subst +extendSubstList subst ((var,rhs):prs) = extendSubstList (extendSubst subst var rhs) prs + +-- | Find the substitution for an 'Id' in the 'Subst' +lookupIdSubst :: SDoc -> Subst -> Id -> CoreExpr +lookupIdSubst doc (Subst in_scope ids _ _) v | not (isLocalId v) = Var v - | otherwise - = case lookupVarEnv ids v of { - Just e -> e ; - Nothing -> - case lookupInScope in_scope v of { - -- Watch out! Must get the Id from the in-scope set, - -- because its type there may differ - Just v -> Var v ; - Nothing -> WARN( True, ptext SLIT("CoreSubst.lookupIdSubst") <+> ppr v ) - Var v - }} + | Just e <- lookupVarEnv ids v = e + | Just v' <- lookupInScope in_scope v = Var v' + -- Vital! See Note [Extending the Subst] + | otherwise = WARN( True, ptext (sLit "CoreSubst.lookupIdSubst") <+> ppr v $$ ppr in_scope $$ doc) + Var v +-- | Find the substitution for a 'TyVar' in the 'Subst' lookupTvSubst :: Subst -> TyVar -> Type -lookupTvSubst (Subst _ ids tvs) v = lookupVarEnv tvs v `orElse` mkTyVarTy v +lookupTvSubst (Subst _ _ tvs _) v = ASSERT( isTyVar v) lookupVarEnv tvs v `orElse` Type.mkTyVarTy v + +-- | Find the coercion substitution for a 'TyCoVar' in the 'Subst' +lookupCvSubst :: Subst -> CoVar -> Coercion +lookupCvSubst (Subst _ _ _ cvs) v = ASSERT( isCoVar v ) lookupVarEnv cvs v `orElse` mkCoVarCo v + +delBndr :: Subst -> Var -> Subst +delBndr (Subst in_scope ids tvs cvs) v + | isCoVar v = Subst in_scope ids tvs (delVarEnv cvs v) + | isTyVar v = Subst in_scope ids (delVarEnv tvs v) cvs + | otherwise = Subst in_scope (delVarEnv ids v) tvs cvs + +delBndrs :: Subst -> [Var] -> Subst +delBndrs (Subst in_scope ids tvs cvs) vs + = Subst in_scope (delVarEnvList ids vs) (delVarEnvList tvs vs) (delVarEnvList cvs vs) + -- Easist thing is just delete all from all! + +-- | Simultaneously substitute for a bunch of variables +-- No left-right shadowing +-- ie the substitution for (\x \y. e) a1 a2 +-- so neither x nor y scope over a1 a2 +mkOpenSubst :: InScopeSet -> [(Var,CoreArg)] -> Subst +mkOpenSubst in_scope pairs = Subst in_scope + (mkVarEnv [(id,e) | (id, e) <- pairs, isId id]) + (mkVarEnv [(tv,ty) | (tv, Type ty) <- pairs]) + (mkVarEnv [(v,co) | (v, Coercion co) <- pairs]) ------------------------------ isInScope :: Var -> Subst -> Bool -isInScope v (Subst in_scope _ _) = v `elemInScopeSet` in_scope +isInScope v (Subst in_scope _ _ _) = v `elemInScopeSet` in_scope + +-- | Add the 'Var' to the in-scope set, but do not remove +-- any existing substitutions for it +addInScopeSet :: Subst -> VarSet -> Subst +addInScopeSet (Subst in_scope ids tvs cvs) vs + = Subst (in_scope `extendInScopeSetSet` vs) ids tvs cvs +-- | Add the 'Var' to the in-scope set: as a side effect, +-- and remove any existing substitutions for it extendInScope :: Subst -> Var -> Subst -extendInScope (Subst in_scope ids tvs) v +extendInScope (Subst in_scope ids tvs cvs) v = Subst (in_scope `extendInScopeSet` v) - (ids `delVarEnv` v) (tvs `delVarEnv` v) + (ids `delVarEnv` v) (tvs `delVarEnv` v) (cvs `delVarEnv` v) + +-- | Add the 'Var's to the in-scope set: see also 'extendInScope' +extendInScopeList :: Subst -> [Var] -> Subst +extendInScopeList (Subst in_scope ids tvs cvs) vs + = Subst (in_scope `extendInScopeSetList` vs) + (ids `delVarEnvList` vs) (tvs `delVarEnvList` vs) (cvs `delVarEnvList` vs) +-- | Optimized version of 'extendInScopeList' that can be used if you are certain +-- all the things being added are 'Id's and hence none are 'TyVar's or 'CoVar's extendInScopeIds :: Subst -> [Id] -> Subst -extendInScopeIds (Subst in_scope ids tvs) vs +extendInScopeIds (Subst in_scope ids tvs cvs) vs = Subst (in_scope `extendInScopeSetList` vs) - (ids `delVarEnvList` vs) tvs + (ids `delVarEnvList` vs) tvs cvs + +setInScope :: Subst -> InScopeSet -> Subst +setInScope (Subst _ ids tvs cvs) in_scope = Subst in_scope ids tvs cvs \end{code} Pretty printing, for debugging only \begin{code} instance Outputable Subst where - ppr (Subst in_scope ids tvs) - = ptext SLIT(" braces (fsep (map ppr (varEnvElts (getInScopeVars in_scope)))) - $$ ptext SLIT(" IdSubst =") <+> ppr ids - $$ ptext SLIT(" TvSubst =") <+> ppr tvs + ppr (Subst in_scope ids tvs cvs) + = ptext (sLit " braces (fsep (map ppr (varEnvElts (getInScopeVars in_scope)))) + $$ ptext (sLit " IdSubst =") <+> ppr ids + $$ ptext (sLit " TvSubst =") <+> ppr tvs + $$ ptext (sLit " CvSubst =") <+> ppr cvs <> char '>' \end{code} @@ -173,20 +337,42 @@ instance Outputable Subst where %************************************************************************ \begin{code} -substExpr :: Subst -> CoreExpr -> CoreExpr -substExpr subst expr +-- | Apply a substititon to an entire 'CoreExpr'. Rememeber, you may only +-- apply the substitution /once/: see "CoreSubst#apply_once" +-- +-- Do *not* attempt to short-cut in the case of an empty substitution! +-- See Note [Extending the Subst] +substExprSC :: SDoc -> Subst -> CoreExpr -> CoreExpr +substExprSC _doc subst orig_expr + | isEmptySubst subst = orig_expr + | otherwise = -- pprTrace "enter subst-expr" (doc $$ ppr orig_expr) $ + subst_expr subst orig_expr + +substExpr :: SDoc -> Subst -> CoreExpr -> CoreExpr +substExpr _doc subst orig_expr = subst_expr subst orig_expr + +subst_expr :: Subst -> CoreExpr -> CoreExpr +subst_expr subst expr = go expr where - go (Var v) = lookupIdSubst subst v + go (Var v) = lookupIdSubst (text "subst_expr") subst v go (Type ty) = Type (substTy subst ty) + go (Coercion co) = Coercion (substCo subst co) go (Lit lit) = Lit lit 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' (substExpr subst' body) + go (Cast e co) = Cast (go e) (substCo subst co) + -- Do not optimise even identity coercions + -- Reason: substitution applies to the LHS of RULES, and + -- if you "optimise" an identity coercion, you may + -- lose a binder. We optimise the LHS of rules at + -- construction time + + go (Lam bndr body) = Lam bndr' (subst_expr subst' body) where (subst', bndr') = substBndr subst bndr - go (Let bind body) = Let bind' (substExpr subst' body) + go (Let bind body) = Let bind' (subst_expr subst' body) where (subst', bind') = substBind subst bind @@ -194,33 +380,52 @@ substExpr subst expr where (subst', bndr') = substBndr subst bndr - go_alt subst (con, bndrs, rhs) = (con, bndrs', substExpr subst' rhs) + go_alt subst (con, bndrs, rhs) = (con, bndrs', subst_expr subst' rhs) where (subst', bndrs') = substBndrs subst bndrs - go_note (Coerce ty1 ty2) = Coerce (substTy subst ty1) (substTy subst ty2) go_note note = note -substBind :: Subst -> CoreBind -> (Subst, CoreBind) -substBind subst (NonRec bndr rhs) = (subst', NonRec bndr' (substExpr subst rhs)) +-- | Apply a substititon to an entire 'CoreBind', additionally returning an updated 'Subst' +-- that should be used by subsequent substitutons. +substBind, substBindSC :: Subst -> CoreBind -> (Subst, CoreBind) + +substBindSC subst bind -- Short-cut if the substitution is empty + | not (isEmptySubst subst) + = substBind subst bind + | otherwise + = case bind of + NonRec bndr rhs -> (subst', NonRec bndr' rhs) + where + (subst', bndr') = substBndr subst bndr + Rec pairs -> (subst', Rec (bndrs' `zip` rhss')) + where + (bndrs, rhss) = unzip pairs + (subst', bndrs') = substRecBndrs subst bndrs + rhss' | isEmptySubst subst' = rhss + | otherwise = map (subst_expr subst') rhss + +substBind subst (NonRec bndr rhs) = (subst', NonRec bndr' (subst_expr subst rhs)) where (subst', bndr') = substBndr subst bndr -substBind subst (Rec pairs) = (subst', Rec pairs') +substBind subst (Rec pairs) = (subst', Rec (bndrs' `zip` rhss')) where - (subst', bndrs') = substRecBndrs subst (map fst pairs) - pairs' = bndrs' `zip` rhss' - rhss' = map (substExpr subst' . snd) pairs + (bndrs, rhss) = unzip pairs + (subst', bndrs') = substRecBndrs subst bndrs + rhss' = map (subst_expr subst') rhss \end{code} -De-shadowing the program is sometimes a useful pre-pass. It can be done simply -by running over the bindings with an empty substitution, becuase substitution -returns a result that has no-shadowing guaranteed. - -(Actually, within a single *type* there might still be shadowing, because -substType is a no-op for the empty substitution, but that's OK.) - \begin{code} +-- | De-shadowing the program is sometimes a useful pre-pass. It can be done simply +-- by running over the bindings with an empty substitution, becuase substitution +-- returns a result that has no-shadowing guaranteed. +-- +-- (Actually, within a single /type/ there might still be shadowing, because +-- 'substTy' is a no-op for the empty substitution, but that's probably OK.) +-- +-- [Aug 09] This function is not used in GHC at the moment, but seems so +-- short and simple that I'm going to leave it here deShadowBinds :: [CoreBind] -> [CoreBind] deShadowBinds binds = snd (mapAccumL substBind emptySubst binds) \end{code} @@ -238,57 +443,81 @@ preserve all IdInfo (suitably substituted). For example, we *want* to preserve occ info in rules. \begin{code} +-- | Substitutes a 'Var' for another one according to the 'Subst' given, returning +-- the result and an updated 'Subst' that should be used by subsequent substitutons. +-- 'IdInfo' is preserved by this process, although it is substituted into appropriately. substBndr :: Subst -> Var -> (Subst, Var) substBndr subst bndr | isTyVar bndr = substTyVarBndr subst bndr - | otherwise = substIdBndr subst subst bndr + | isCoVar bndr = substCoVarBndr subst bndr + | otherwise = substIdBndr (text "var-bndr") subst subst bndr +-- | Applies 'substBndr' to a number of 'Var's, accumulating a new 'Subst' left-to-right substBndrs :: Subst -> [Var] -> (Subst, [Var]) substBndrs subst bndrs = mapAccumL substBndr subst bndrs +-- | Substitute in a mutually recursive group of 'Id's substRecBndrs :: Subst -> [Id] -> (Subst, [Id]) --- Substitute a mutually recursive group substRecBndrs subst bndrs = (new_subst, new_bndrs) where -- Here's the reason we need to pass rec_subst to subst_id - (new_subst, new_bndrs) = mapAccumL (substIdBndr new_subst) subst bndrs + (new_subst, new_bndrs) = mapAccumL (substIdBndr (text "rec-bndr") new_subst) subst bndrs \end{code} \begin{code} -substIdBndr :: Subst -- Substitution to use for the IdInfo - -> Subst -> Id -- Substitition and Id to transform - -> (Subst, Id) -- Transformed pair - -substIdBndr rec_subst subst@(Subst in_scope env tvs) old_id - = (Subst (in_scope `extendInScopeSet` new_id) new_env tvs, new_id) +substIdBndr :: SDoc + -> Subst -- ^ Substitution to use for the IdInfo + -> Subst -> Id -- ^ Substitition and Id to transform + -> (Subst, Id) -- ^ Transformed pair + -- NB: unfolding may be zapped + +substIdBndr _doc rec_subst subst@(Subst in_scope env tvs cvs) old_id + = -- pprTrace "substIdBndr" (doc $$ ppr old_id $$ ppr in_scope) $ + (Subst (in_scope `extendInScopeSet` new_id) new_env tvs cvs, new_id) where id1 = uniqAway in_scope old_id -- id1 is cloned if necessary - id2 = substIdType subst id1 -- id2 has its type zapped + id2 | no_type_change = id1 + | otherwise = setIdType id1 (substTy subst old_ty) + + old_ty = idType old_id + no_type_change = isEmptyVarEnv tvs || + isEmptyVarSet (Type.tyVarsOfType old_ty) -- new_id has the right IdInfo -- The lazy-set is because we're in a loop here, with -- rec_subst, when dealing with a mutually-recursive group - new_id = maybeModifyIdInfo (substIdInfo rec_subst) id2 + new_id = maybeModifyIdInfo mb_new_info id2 + mb_new_info = substIdInfo rec_subst id2 (idInfo id2) + -- NB: unfolding info may be zapped -- Extend the substitution if the unique has changed -- See the notes with substTyVarBndr for the delVarEnv - new_env | new_id /= old_id = extendVarEnv env old_id (Var new_id) - | otherwise = delVarEnv env old_id + new_env | no_change = delVarEnv env old_id + | otherwise = extendVarEnv env old_id (Var new_id) + + no_change = id1 == old_id + -- See Note [Extending the Subst] + -- it's /not/ necessary to check mb_new_info and no_type_change \end{code} Now a variant that unconditionally allocates a new unique. It also unconditionally zaps the OccInfo. \begin{code} +-- | Very similar to 'substBndr', but it always allocates a new 'Unique' for +-- each variable in its output. It substitutes the IdInfo though. cloneIdBndr :: Subst -> UniqSupply -> Id -> (Subst, Id) cloneIdBndr subst us old_id = clone_id subst subst (old_id, uniqFromSupply us) +-- | Applies 'cloneIdBndr' to a number of 'Id's, accumulating a final +-- substitution from left to right cloneIdBndrs :: Subst -> UniqSupply -> [Id] -> (Subst, [Id]) cloneIdBndrs subst us ids = mapAccumL (clone_id subst) subst (ids `zip` uniqsFromSupply us) +-- | Clone a mutually recursive group of 'Id's cloneRecIdBndrs :: Subst -> UniqSupply -> [Id] -> (Subst, [Id]) cloneRecIdBndrs subst us ids = (subst', ids') @@ -302,35 +531,52 @@ clone_id :: Subst -- Substitution for the IdInfo -> Subst -> (Id, Unique) -- Substitition and Id to transform -> (Subst, Id) -- Transformed pair -clone_id rec_subst subst@(Subst in_scope env tvs) (old_id, uniq) - = (Subst (in_scope `extendInScopeSet` new_id) new_env tvs, new_id) +clone_id rec_subst subst@(Subst in_scope env tvs cvs) (old_id, uniq) + = (Subst (in_scope `extendInScopeSet` new_id) new_env tvs cvs, new_id) where id1 = setVarUnique old_id uniq id2 = substIdType subst id1 - new_id = maybeModifyIdInfo (substIdInfo rec_subst) id2 + new_id = maybeModifyIdInfo (substIdInfo rec_subst id2 (idInfo old_id)) id2 new_env = extendVarEnv env old_id (Var new_id) \end{code} %************************************************************************ %* * - Types + Types and Coercions %* * %************************************************************************ -For types we just call the corresponding function in Type, but we have -to repackage the substitution, from a Subst to a TvSubst +For types and coercions we just call the corresponding functions in +Type and Coercion, but we have to repackage the substitution, from a +Subst to a TvSubst. \begin{code} substTyVarBndr :: Subst -> TyVar -> (Subst, TyVar) -substTyVarBndr (Subst in_scope id_env tv_env) tv +substTyVarBndr (Subst in_scope id_env tv_env cv_env) tv = case Type.substTyVarBndr (TvSubst in_scope tv_env) tv of (TvSubst in_scope' tv_env', tv') - -> (Subst in_scope' id_env tv_env', tv') + -> (Subst in_scope' id_env tv_env' cv_env, tv') +substCoVarBndr :: Subst -> TyVar -> (Subst, TyVar) +substCoVarBndr (Subst in_scope id_env tv_env cv_env) cv + = case Coercion.substCoVarBndr (CvSubst in_scope tv_env cv_env) cv of + (CvSubst in_scope' tv_env' cv_env', cv') + -> (Subst in_scope' id_env tv_env' cv_env', cv') + +-- | See 'Type.substTy' substTy :: Subst -> Type -> Type -substTy (Subst in_scope id_env tv_env) ty - = Type.substTy (TvSubst in_scope tv_env) ty +substTy subst ty = Type.substTy (getTvSubst subst) ty + +getTvSubst :: Subst -> TvSubst +getTvSubst (Subst in_scope _ tenv _) = TvSubst in_scope tenv + +getCvSubst :: Subst -> CvSubst +getCvSubst (Subst in_scope _ tenv cenv) = CvSubst in_scope tenv cenv + +-- | See 'Coercion.substCo' +substCo :: Subst -> Coercion -> Coercion +substCo subst co = Coercion.substCo (getCvSubst subst) co \end{code} @@ -342,8 +588,8 @@ substTy (Subst in_scope id_env tv_env) ty \begin{code} substIdType :: Subst -> Id -> Id -substIdType subst@(Subst in_scope id_env tv_env) id - | isEmptyVarEnv tv_env || isEmptyVarSet (tyVarsOfType old_ty) = id +substIdType subst@(Subst _ _ tv_env cv_env) id + | (isEmptyVarEnv tv_env && isEmptyVarEnv cv_env) || isEmptyVarSet (Type.tyVarsOfType old_ty) = id | otherwise = setIdType id (substTy subst old_ty) -- The tyVarsOfType is cheaper than it looks -- because we cache the free tyvars of the type @@ -352,60 +598,394 @@ substIdType subst@(Subst in_scope id_env tv_env) id old_ty = idType id ------------------ -substIdInfo :: Subst -> IdInfo -> Maybe IdInfo --- Always zaps the unfolding, to save substitution work -substIdInfo subst info +-- | Substitute into some 'IdInfo' with regard to the supplied new 'Id'. +substIdInfo :: Subst -> Id -> IdInfo -> Maybe IdInfo +substIdInfo subst new_id info | nothing_to_do = Nothing - | otherwise = Just (info `setSpecInfo` substSpec subst old_rules - `setWorkerInfo` substWorker subst old_wrkr - `setUnfoldingInfo` noUnfolding) + | otherwise = Just (info `setSpecInfo` substSpec subst new_id old_rules + `setUnfoldingInfo` substUnfolding subst old_unf) where old_rules = specInfo info - old_wrkr = workerInfo info - nothing_to_do = isEmptySpecInfo old_rules && - not (workerExists old_wrkr) && - not (hasUnfolding (unfoldingInfo info)) + old_unf = unfoldingInfo info + nothing_to_do = isEmptySpecInfo old_rules && isClosedUnfolding old_unf ------------------ -substWorker :: Subst -> WorkerInfo -> WorkerInfo - -- Seq'ing on the returned WorkerInfo is enough to cause all the - -- substitutions to happen completely - -substWorker subst NoWorker - = NoWorker -substWorker subst (HasWorker w a) - = case lookupIdSubst subst w of - Var w1 -> HasWorker w1 a - other -> WARN( not (exprIsTrivial other), text "CoreSubst.substWorker:" <+> ppr w ) - NoWorker -- Worker has got substituted away altogether - -- (This can happen if it's trivial, - -- via postInlineUnconditionally, hence warning) +-- | Substitutes for the 'Id's within an unfolding +substUnfolding, substUnfoldingSC :: Subst -> Unfolding -> Unfolding + -- Seq'ing on the returned Unfolding is enough to cause + -- all the substitutions to happen completely + +substUnfoldingSC subst unf -- Short-cut version + | isEmptySubst subst = unf + | otherwise = substUnfolding subst unf + +substUnfolding subst (DFunUnfolding ar con args) + = DFunUnfolding ar con (map subst_arg args) + where + subst_arg = fmap (substExpr (text "dfun-unf") subst) + +substUnfolding subst unf@(CoreUnfolding { uf_tmpl = tmpl, uf_src = src }) + -- Retain an InlineRule! + | not (isStableSource src) -- Zap an unstable unfolding, to save substitution work + = NoUnfolding + | otherwise -- But keep a stable one! + = seqExpr new_tmpl `seq` + new_src `seq` + unf { uf_tmpl = new_tmpl, uf_src = new_src } + where + new_tmpl = substExpr (text "subst-unf") subst tmpl + new_src = substUnfoldingSource subst src + +substUnfolding _ unf = unf -- NoUnfolding, OtherCon + +------------------- +substUnfoldingSource :: Subst -> UnfoldingSource -> UnfoldingSource +substUnfoldingSource (Subst in_scope ids _ _) (InlineWrapper wkr) + | Just wkr_expr <- lookupVarEnv ids wkr + = case wkr_expr of + Var w1 -> InlineWrapper w1 + _other -> -- WARN( True, text "Interesting! CoreSubst.substWorker1:" <+> ppr wkr + -- <+> ifPprDebug (equals <+> ppr wkr_expr) ) + -- Note [Worker inlining] + InlineStable -- It's not a wrapper any more, but still inline it! + + | Just w1 <- lookupInScope in_scope wkr = InlineWrapper w1 + | otherwise = -- WARN( True, text "Interesting! CoreSubst.substWorker2:" <+> ppr wkr ) + -- This can legitimately happen. The worker has been inlined and + -- dropped as dead code, because we don't treat the UnfoldingSource + -- as an "occurrence". + -- Note [Worker inlining] + InlineStable + +substUnfoldingSource _ src = src + +------------------ +substIdOcc :: Subst -> Id -> Id +-- These Ids should not be substituted to non-Ids +substIdOcc subst v = case lookupIdSubst (text "substIdOcc") subst v of + Var v' -> v' + other -> pprPanic "substIdOcc" (vcat [ppr v <+> ppr other, ppr subst]) + +------------------ +-- | Substitutes for the 'Id's within the 'WorkerInfo' given the new function 'Id' +substSpec :: Subst -> Id -> SpecInfo -> SpecInfo +substSpec subst new_id (SpecInfo rules rhs_fvs) + = seqSpecInfo new_spec `seq` new_spec + where + subst_ru_fn = const (idName new_id) + new_spec = SpecInfo (map (substRule subst subst_ru_fn) rules) + (substVarSet subst rhs_fvs) ------------------ -substSpec :: Subst -> SpecInfo -> SpecInfo +substRulesForImportedIds :: Subst -> [CoreRule] -> [CoreRule] +substRulesForImportedIds subst rules + = map (substRule subst not_needed) rules + where + not_needed name = pprPanic "substRulesForImportedIds" (ppr name) -substSpec subst spec@(SpecInfo rules rhs_fvs) - | isEmptySubst subst - = spec - | otherwise - = seqSpecInfo new_rules `seq` new_rules +------------------ +substRule :: Subst -> (Name -> Name) -> CoreRule -> CoreRule + +-- The subst_ru_fn argument is applied to substitute the ru_fn field +-- of the rule: +-- - Rules for *imported* Ids never change ru_fn +-- - Rules for *local* Ids are in the IdInfo for that Id, +-- and the ru_fn field is simply replaced by the new name +-- of the Id +substRule _ _ rule@(BuiltinRule {}) = rule +substRule subst subst_ru_fn rule@(Rule { ru_bndrs = bndrs, ru_args = args + , ru_fn = fn_name, ru_rhs = rhs + , ru_local = is_local }) + = rule { ru_bndrs = bndrs', + ru_fn = if is_local + then subst_ru_fn fn_name + else fn_name, + ru_args = map (substExpr (text "subst-rule" <+> ppr fn_name) subst') args, + ru_rhs = simpleOptExprWith subst' rhs } + -- Do simple optimisation on RHS, in case substitution lets + -- you improve it. The real simplifier never gets to look at it. where - new_rules = SpecInfo (map do_subst rules) (substVarSet subst rhs_fvs) + (subst', bndrs') = substBndrs subst bndrs - do_subst rule@(BuiltinRule {}) = rule - do_subst rule@(Rule { ru_bndrs = bndrs, ru_args = args, ru_rhs = rhs }) - = rule { ru_bndrs = bndrs', - ru_args = map (substExpr subst') args, - ru_rhs = substExpr subst' rhs } - where - (subst', bndrs') = substBndrs subst bndrs +------------------ +substVects :: Subst -> [CoreVect] -> [CoreVect] +substVects subst = map (substVect subst) ------------------ -substVarSet subst fvs +substVect :: Subst -> CoreVect -> CoreVect +substVect _subst (Vect v Nothing) = Vect v Nothing +substVect subst (Vect v (Just rhs)) = Vect v (Just (simpleOptExprWith subst rhs)) + +------------------ +substVarSet :: Subst -> VarSet -> VarSet +substVarSet subst fvs = foldVarSet (unionVarSet . subst_fv subst) emptyVarSet fvs where subst_fv subst fv - | isId fv = exprFreeVars (lookupIdSubst subst fv) - | otherwise = tyVarsOfType (lookupTvSubst subst fv) + | isId fv = exprFreeVars (lookupIdSubst (text "substVarSet") subst fv) + | otherwise = Type.tyVarsOfType (lookupTvSubst subst fv) +\end{code} + +Note [Worker inlining] +~~~~~~~~~~~~~~~~~~~~~~ +A worker can get sustituted away entirely. + - it might be trivial + - it might simply be very small +We do not treat an InlWrapper as an 'occurrence' in the occurence +analyser, so it's possible that the worker is not even in scope any more. + +In all all these cases we simply drop the special case, returning to +InlVanilla. The WARN is just so I can see if it happens a lot. + + +%************************************************************************ +%* * + The Very Simple Optimiser +%* * +%************************************************************************ + +\begin{code} +simpleOptExpr :: CoreExpr -> CoreExpr +-- Do simple optimisation on an expression +-- The optimisation is very straightforward: just +-- inline non-recursive bindings that are used only once, +-- or where the RHS is trivial +-- +-- The result is NOT guaranteed occurence-analysed, becuase +-- in (let x = y in ....) we substitute for x; so y's occ-info +-- may change radically + +simpleOptExpr expr + = -- pprTrace "simpleOptExpr" (ppr init_subst $$ ppr expr) + simpleOptExprWith init_subst expr + where + init_subst = mkEmptySubst (mkInScopeSet (exprFreeVars expr)) + -- It's potentially important to make a proper in-scope set + -- Consider let x = ..y.. in \y. ...x... + -- Then we should remember to clone y before substituting + -- for x. It's very unlikely to occur, because we probably + -- won't *be* substituting for x if it occurs inside a + -- lambda. + -- + -- It's a bit painful to call exprFreeVars, because it makes + -- three passes instead of two (occ-anal, and go) + +simpleOptExprWith :: Subst -> InExpr -> OutExpr +simpleOptExprWith subst expr = simple_opt_expr subst (occurAnalyseExpr expr) + +---------------------- +simpleOptPgm :: DynFlags -> [CoreBind] -> [CoreRule] -> [CoreVect] + -> IO ([CoreBind], [CoreRule], [CoreVect]) +simpleOptPgm dflags binds rules vects + = do { dumpIfSet_dyn dflags Opt_D_dump_occur_anal "Occurrence analysis" + (pprCoreBindings occ_anald_binds); + + ; return (reverse binds', substRulesForImportedIds subst' rules, substVects subst' vects) } + where + occ_anald_binds = occurAnalysePgm Nothing {- No rules active -} + rules vects binds + (subst', binds') = foldl do_one (emptySubst, []) occ_anald_binds + + do_one (subst, binds') bind + = case simple_opt_bind subst bind of + (subst', Nothing) -> (subst', binds') + (subst', Just bind') -> (subst', bind':binds') + +---------------------- +type InVar = Var +type OutVar = Var +type InId = Id +type OutId = Id +type InExpr = CoreExpr +type OutExpr = CoreExpr + +-- In these functions the substitution maps InVar -> OutExpr + +---------------------- +simple_opt_expr, simple_opt_expr' :: Subst -> InExpr -> OutExpr +simple_opt_expr s e = simple_opt_expr' s e + +simple_opt_expr' subst expr + = go expr + where + go (Var v) = lookupIdSubst (text "simpleOptExpr") subst v + go (App e1 e2) = simple_app subst e1 [go e2] + go (Type ty) = Type (substTy subst ty) + go (Coercion co) = Coercion (optCoercion (getCvSubst subst) co) + go (Lit lit) = Lit lit + go (Note note e) = Note note (go e) + go (Cast e co) | isReflCo co' = go e + | otherwise = Cast (go e) co' + where + co' = optCoercion (getCvSubst subst) co + + go (Let bind body) = case simple_opt_bind subst bind of + (subst', Nothing) -> simple_opt_expr subst' body + (subst', Just bind) -> Let bind (simple_opt_expr subst' body) + + go lam@(Lam {}) = go_lam [] subst lam + go (Case e b ty as) = Case (go e) b' (substTy subst ty) + (map (go_alt subst') as) + where + (subst', b') = subst_opt_bndr subst b + + ---------------------- + go_alt subst (con, bndrs, rhs) + = (con, bndrs', simple_opt_expr subst' rhs) + where + (subst', bndrs') = subst_opt_bndrs subst bndrs + + ---------------------- + -- go_lam tries eta reduction + go_lam bs' subst (Lam b e) + = go_lam (b':bs') subst' e + where + (subst', b') = subst_opt_bndr subst b + go_lam bs' subst e + | Just etad_e <- tryEtaReduce bs e' = etad_e + | otherwise = mkLams bs e' + where + bs = reverse bs' + e' = simple_opt_expr subst e + +---------------------- +-- simple_app collects arguments for beta reduction +simple_app :: Subst -> InExpr -> [OutExpr] -> CoreExpr +simple_app subst (App e1 e2) as + = simple_app subst e1 (simple_opt_expr subst e2 : as) +simple_app subst (Lam b e) (a:as) + = case maybe_substitute subst b a of + Just ext_subst -> simple_app ext_subst e as + Nothing -> Let (NonRec b2 a) (simple_app subst' e as) + where + (subst', b') = subst_opt_bndr subst b + b2 = add_info subst' b b' +simple_app subst e as + = foldl App (simple_opt_expr subst e) as + +---------------------- +simple_opt_bind,simple_opt_bind' :: Subst -> CoreBind -> (Subst, Maybe CoreBind) +simple_opt_bind s b -- Can add trace stuff here + = simple_opt_bind' s b + +simple_opt_bind' subst (Rec prs) + = (subst'', res_bind) + where + res_bind = Just (Rec (reverse rev_prs')) + (subst', bndrs') = subst_opt_bndrs subst (map fst prs) + (subst'', rev_prs') = foldl do_pr (subst', []) (prs `zip` bndrs') + do_pr (subst, prs) ((b,r), b') + = case maybe_substitute subst b r2 of + Just subst' -> (subst', prs) + Nothing -> (subst, (b2,r2):prs) + where + b2 = add_info subst b b' + r2 = simple_opt_expr subst r + +simple_opt_bind' subst (NonRec b r) + = case maybe_substitute subst b r' of + Just ext_subst -> (ext_subst, Nothing) + Nothing -> (subst', Just (NonRec b2 r')) + where + r' = simple_opt_expr subst r + (subst', b') = subst_opt_bndr subst b + b2 = add_info subst' b b' + +---------------------- +maybe_substitute :: Subst -> InVar -> OutExpr -> Maybe Subst + -- (maybe_substitute subst in_var out_rhs) + -- either extends subst with (in_var -> out_rhs) + -- or returns Nothing +maybe_substitute subst b r + | Type ty <- r -- let a::* = TYPE ty in + = ASSERT( isTyVar b ) + Just (extendTvSubst subst b ty) + + | Coercion co <- r + = ASSERT( isCoVar b ) + Just (extendCvSubst subst b co) + + | isId b -- let x = e in + , safe_to_inline (idOccInfo b) + , isAlwaysActive (idInlineActivation b) -- Note [Inline prag in simplOpt] + , not (isStableUnfolding (idUnfolding b)) + , not (isExportedId b) + = Just (extendIdSubst subst b r) + + | otherwise + = Nothing + where + -- Unconditionally safe to inline + safe_to_inline :: OccInfo -> Bool + safe_to_inline (IAmALoopBreaker {}) = False + safe_to_inline IAmDead = True + safe_to_inline (OneOcc in_lam one_br _) = (not in_lam && one_br) || exprIsTrivial r + safe_to_inline NoOccInfo = exprIsTrivial r + +---------------------- +subst_opt_bndr :: Subst -> InVar -> (Subst, OutVar) +subst_opt_bndr subst bndr + | isTyVar bndr = substTyVarBndr subst bndr + | isCoVar bndr = substCoVarBndr subst bndr + | otherwise = subst_opt_id_bndr subst bndr + +subst_opt_id_bndr :: Subst -> InId -> (Subst, OutId) +-- Nuke all fragile IdInfo, unfolding, and RULES; +-- it gets added back later by add_info +-- Rather like SimplEnv.substIdBndr +-- +-- It's important to zap fragile OccInfo (which CoreSubst.substIdBndr +-- carefully does not do) because simplOptExpr invalidates it + +subst_opt_id_bndr subst@(Subst in_scope id_subst tv_subst cv_subst) old_id + = (Subst new_in_scope new_id_subst tv_subst cv_subst, new_id) + where + id1 = uniqAway in_scope old_id + id2 = setIdType id1 (substTy subst (idType old_id)) + new_id = zapFragileIdInfo id2 -- Zaps rules, worker-info, unfolding + -- and fragile OccInfo + new_in_scope = in_scope `extendInScopeSet` new_id + + -- Extend the substitution if the unique has changed, + -- or there's some useful occurrence information + -- See the notes with substTyVarBndr for the delSubstEnv + new_id_subst | new_id /= old_id + = extendVarEnv id_subst old_id (Var new_id) + | otherwise + = delVarEnv id_subst old_id + +---------------------- +subst_opt_bndrs :: Subst -> [InVar] -> (Subst, [OutVar]) +subst_opt_bndrs subst bndrs + = mapAccumL subst_opt_bndr subst bndrs + +---------------------- +add_info :: Subst -> InVar -> OutVar -> OutVar +add_info subst old_bndr new_bndr + | isTyVar old_bndr = new_bndr + | otherwise = maybeModifyIdInfo mb_new_info new_bndr + where + mb_new_info = substIdInfo subst new_bndr (idInfo old_bndr) \end{code} + +Note [Inline prag in simplOpt] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +If there's an INLINE/NOINLINE pragma that restricts the phase in +which the binder can be inlined, we don't inline here; after all, +we don't know what phase we're in. Here's an example + + foo :: Int -> Int -> Int + {-# INLINE foo #-} + foo m n = inner m + where + {-# INLINE [1] inner #-} + inner m = m+n + + bar :: Int -> Int + bar n = foo n 1 + +When inlining 'foo' in 'bar' we want the let-binding for 'inner' +to remain visible until Phase 1 + +