%
% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
Utility functions on @Core@ syntax
\begin{code}
module CoreSubst (
Subst, TvSubstEnv, IdSubstEnv, InScopeSet,
deShadowBinds, substSpec, substRulesForImportedIds,
substTy, substExpr, substExprSC, substBind, substBindSC,
substUnfolding, substUnfoldingSC,
substUnfoldingSource, lookupIdSubst, lookupTvSubst, substIdOcc,
emptySubst, mkEmptySubst, mkSubst, mkOpenSubst, substInScope, isEmptySubst,
extendIdSubst, extendIdSubstList, extendTvSubst, extendTvSubstList,
extendSubst, extendSubstList, zapSubstEnv,
addInScopeSet, extendInScope, extendInScopeList, extendInScopeIds,
isInScope, setInScope,
delBndr, delBndrs,
substBndr, substBndrs, substRecBndrs,
cloneIdBndr, cloneIdBndrs, cloneRecIdBndrs,
simpleOptPgm, simpleOptExpr, simpleOptExprWith
) where
#include "HsVersions.h"
import CoreSyn
import CoreFVs
import CoreUtils
import PprCore
import OccurAnal( occurAnalyseExpr, occurAnalysePgm )
import qualified Type
import Type ( Type, TvSubst(..), TvSubstEnv )
import Coercion ( isIdentityCoercion )
import OptCoercion ( optCoercion )
import VarSet
import VarEnv
import Id
import Name ( Name )
import Var ( Var, TyVar, setVarUnique )
import IdInfo
import Unique
import UniqSupply
import Maybes
import ErrUtils
import DynFlags ( DynFlags, DynFlag(..) )
import BasicTypes ( isAlwaysActive )
import Outputable
import PprCore ()
import FastString
import Data.List
\end{code}
%************************************************************************
%* *
\subsection{Substitutions}
%* *
%************************************************************************
\begin{code}
data Subst
= Subst InScopeSet
IdSubstEnv
TvSubstEnv
\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
* 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?
* 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}
type IdSubstEnv = IdEnv CoreExpr
isEmptySubst :: Subst -> Bool
isEmptySubst (Subst _ id_env tv_env) = isEmptyVarEnv id_env && isEmptyVarEnv tv_env
emptySubst :: Subst
emptySubst = Subst emptyInScopeSet 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
substInScope :: Subst -> InScopeSet
substInScope (Subst in_scope _ _) = in_scope
zapSubstEnv :: Subst -> Subst
zapSubstEnv (Subst in_scope _ _) = Subst in_scope emptyVarEnv emptyVarEnv
extendIdSubst :: Subst -> Id -> CoreExpr -> Subst
extendIdSubst (Subst in_scope ids tvs) v r = Subst in_scope (extendVarEnv ids v r) tvs
extendIdSubstList :: Subst -> [(Id, CoreExpr)] -> Subst
extendIdSubstList (Subst in_scope ids tvs) prs = Subst in_scope (extendVarEnvList ids prs) tvs
extendTvSubst :: Subst -> TyVar -> Type -> Subst
extendTvSubst (Subst in_scope ids tvs) v r = Subst in_scope ids (extendVarEnv tvs v r)
extendTvSubstList :: Subst -> [(TyVar,Type)] -> Subst
extendTvSubstList (Subst in_scope ids tvs) prs = Subst in_scope ids (extendVarEnvList tvs prs)
extendSubst :: Subst -> Var -> CoreArg -> Subst
extendSubst (Subst in_scope ids tvs) tv (Type ty)
= ASSERT( isTyCoVar tv ) Subst in_scope ids (extendVarEnv tvs tv ty)
extendSubst (Subst in_scope ids tvs) id expr
= ASSERT( isId id ) Subst in_scope (extendVarEnv ids id expr) tvs
extendSubstList :: Subst -> [(Var,CoreArg)] -> Subst
extendSubstList subst [] = subst
extendSubstList subst ((var,rhs):prs) = extendSubstList (extendSubst subst var rhs) prs
lookupIdSubst :: SDoc -> Subst -> Id -> CoreExpr
lookupIdSubst doc (Subst in_scope ids _) v
| not (isLocalId v) = Var v
| Just e <- lookupVarEnv ids v = e
| Just v' <- lookupInScope in_scope v = Var v'
| otherwise = WARN( True, ptext (sLit "CoreSubst.lookupIdSubst") <+> ppr v $$ ppr in_scope $$ doc)
Var v
lookupTvSubst :: Subst -> TyVar -> Type
lookupTvSubst (Subst _ _ tvs) v = lookupVarEnv tvs v `orElse` Type.mkTyVarTy v
delBndr :: Subst -> Var -> Subst
delBndr (Subst in_scope tvs ids) v
| isId v = Subst in_scope tvs (delVarEnv ids v)
| otherwise = Subst in_scope (delVarEnv tvs v) ids
delBndrs :: Subst -> [Var] -> Subst
delBndrs (Subst in_scope tvs ids) vs
= Subst in_scope (delVarEnvList tvs vs_tv) (delVarEnvList ids vs_id)
where
(vs_id, vs_tv) = partition isId vs
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])
isInScope :: Var -> Subst -> Bool
isInScope v (Subst in_scope _ _) = v `elemInScopeSet` in_scope
addInScopeSet :: Subst -> VarSet -> Subst
addInScopeSet (Subst in_scope ids tvs) vs
= Subst (in_scope `extendInScopeSetSet` vs) ids tvs
extendInScope :: Subst -> Var -> Subst
extendInScope (Subst in_scope ids tvs) v
= Subst (in_scope `extendInScopeSet` v)
(ids `delVarEnv` v) (tvs `delVarEnv` v)
extendInScopeList :: Subst -> [Var] -> Subst
extendInScopeList (Subst in_scope ids tvs) vs
= Subst (in_scope `extendInScopeSetList` vs)
(ids `delVarEnvList` vs) (tvs `delVarEnvList` vs)
extendInScopeIds :: Subst -> [Id] -> Subst
extendInScopeIds (Subst in_scope ids tvs) vs
= Subst (in_scope `extendInScopeSetList` vs)
(ids `delVarEnvList` vs) tvs
setInScope :: Subst -> InScopeSet -> Subst
setInScope (Subst _ ids tvs) in_scope = Subst in_scope ids tvs
\end{code}
Pretty printing, for debugging only
\begin{code}
instance Outputable Subst where
ppr (Subst in_scope ids tvs)
= ptext (sLit "<InScope =") <+> braces (fsep (map ppr (varEnvElts (getInScopeVars in_scope))))
$$ ptext (sLit " IdSubst =") <+> ppr ids
$$ ptext (sLit " TvSubst =") <+> ppr tvs
<> char '>'
\end{code}
%************************************************************************
%* *
Substituting expressions
%* *
%************************************************************************
\begin{code}
substExprSC :: SDoc -> Subst -> CoreExpr -> CoreExpr
substExprSC _doc subst orig_expr
| isEmptySubst subst = orig_expr
| otherwise =
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 (text "subst_expr") subst v
go (Type ty) = Type (substTy subst ty)
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 (Cast e co) = Cast (go e) (optCoercion (getTvSubst subst) co)
go (Lam bndr body) = Lam bndr' (subst_expr subst' body)
where
(subst', bndr') = substBndr subst bndr
go (Let bind body) = Let bind' (subst_expr subst' body)
where
(subst', bind') = substBind subst bind
go (Case scrut bndr ty alts) = Case (go scrut) bndr' (substTy subst ty) (map (go_alt subst') alts)
where
(subst', bndr') = substBndr subst bndr
go_alt subst (con, bndrs, rhs) = (con, bndrs', subst_expr subst' rhs)
where
(subst', bndrs') = substBndrs subst bndrs
go_note note = note
substBind, substBindSC :: Subst -> CoreBind -> (Subst, CoreBind)
substBindSC subst bind
| 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 (bndrs' `zip` rhss'))
where
(bndrs, rhss) = unzip pairs
(subst', bndrs') = substRecBndrs subst bndrs
rhss' = map (subst_expr subst') rhss
\end{code}
\begin{code}
deShadowBinds :: [CoreBind] -> [CoreBind]
deShadowBinds binds = snd (mapAccumL substBind emptySubst binds)
\end{code}
%************************************************************************
%* *
Substituting binders
%* *
%************************************************************************
Remember that substBndr and friends are used when doing expression
substitution only. Their only business is substitution, so they
preserve all IdInfo (suitably substituted). For example, we *want* to
preserve occ info in rules.
\begin{code}
substBndr :: Subst -> Var -> (Subst, Var)
substBndr subst bndr
| isTyCoVar bndr = substTyVarBndr subst bndr
| otherwise = substIdBndr (text "var-bndr") subst subst bndr
substBndrs :: Subst -> [Var] -> (Subst, [Var])
substBndrs subst bndrs = mapAccumL substBndr subst bndrs
substRecBndrs :: Subst -> [Id] -> (Subst, [Id])
substRecBndrs subst bndrs
= (new_subst, new_bndrs)
where
(new_subst, new_bndrs) = mapAccumL (substIdBndr (text "rec-bndr") new_subst) subst bndrs
\end{code}
\begin{code}
substIdBndr :: SDoc
-> Subst
-> Subst -> Id
-> (Subst, Id)
substIdBndr _doc rec_subst subst@(Subst in_scope env tvs) old_id
=
(Subst (in_scope `extendInScopeSet` new_id) new_env tvs, new_id)
where
id1 = uniqAway in_scope old_id
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 = maybeModifyIdInfo mb_new_info id2
mb_new_info = substIdInfo rec_subst id2 (idInfo id2)
new_env | no_change = delVarEnv env old_id
| otherwise = extendVarEnv env old_id (Var new_id)
no_change = id1 == old_id
\end{code}
Now a variant that unconditionally allocates a new unique.
It also unconditionally zaps the OccInfo.
\begin{code}
cloneIdBndr :: Subst -> UniqSupply -> Id -> (Subst, Id)
cloneIdBndr subst us old_id
= clone_id subst subst (old_id, uniqFromSupply us)
cloneIdBndrs :: Subst -> UniqSupply -> [Id] -> (Subst, [Id])
cloneIdBndrs subst us ids
= mapAccumL (clone_id subst) subst (ids `zip` uniqsFromSupply us)
cloneRecIdBndrs :: Subst -> UniqSupply -> [Id] -> (Subst, [Id])
cloneRecIdBndrs subst us ids
= (subst', ids')
where
(subst', ids') = mapAccumL (clone_id subst') subst
(ids `zip` uniqsFromSupply us)
clone_id :: Subst
-> Subst -> (Id, Unique)
-> (Subst, Id)
clone_id rec_subst subst@(Subst in_scope env tvs) (old_id, uniq)
= (Subst (in_scope `extendInScopeSet` new_id) new_env tvs, new_id)
where
id1 = setVarUnique old_id uniq
id2 = substIdType subst id1
new_id = maybeModifyIdInfo (substIdInfo rec_subst id2 (idInfo old_id)) id2
new_env = extendVarEnv env old_id (Var new_id)
\end{code}
%************************************************************************
%* *
Types
%* *
%************************************************************************
For types we just call the corresponding function in Type, 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
= case Type.substTyVarBndr (TvSubst in_scope tv_env) tv of
(TvSubst in_scope' tv_env', tv')
-> (Subst in_scope' id_env tv_env', tv')
substTy :: Subst -> Type -> Type
substTy subst ty = Type.substTy (getTvSubst subst) ty
getTvSubst :: Subst -> TvSubst
getTvSubst (Subst in_scope _id_env tv_env) = TvSubst in_scope tv_env
\end{code}
%************************************************************************
%* *
\section{IdInfo substitution}
%* *
%************************************************************************
\begin{code}
substIdType :: Subst -> Id -> Id
substIdType subst@(Subst _ _ tv_env) id
| isEmptyVarEnv tv_env || isEmptyVarSet (Type.tyVarsOfType old_ty) = id
| otherwise = setIdType id (substTy subst old_ty)
where
old_ty = idType id
substIdInfo :: Subst -> Id -> IdInfo -> Maybe IdInfo
substIdInfo subst new_id info
| nothing_to_do = Nothing
| otherwise = Just (info `setSpecInfo` substSpec subst new_id old_rules
`setUnfoldingInfo` substUnfolding subst old_unf)
where
old_rules = specInfo info
old_unf = unfoldingInfo info
nothing_to_do = isEmptySpecInfo old_rules && isClosedUnfolding old_unf
substUnfolding, substUnfoldingSC :: Subst -> Unfolding -> Unfolding
substUnfoldingSC subst unf
| 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 })
| not (isStableSource src)
= NoUnfolding
| otherwise
= 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
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 ->
InlineStable
| Just w1 <- lookupInScope in_scope wkr = InlineWrapper w1
| otherwise =
InlineStable
substUnfoldingSource _ src = src
substIdOcc :: Subst -> Id -> Id
substIdOcc subst v = case lookupIdSubst (text "substIdOcc") subst v of
Var v' -> v'
other -> pprPanic "substIdOcc" (vcat [ppr v <+> ppr other, ppr subst])
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)
substRulesForImportedIds :: Subst -> [CoreRule] -> [CoreRule]
substRulesForImportedIds subst rules
= map (substRule subst not_needed) rules
where
not_needed name = pprPanic "substRulesForImportedIds" (ppr name)
substRule :: Subst -> (Name -> Name) -> CoreRule -> CoreRule
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 }
where
(subst', bndrs') = substBndrs subst bndrs
substVarSet :: Subst -> VarSet -> VarSet
substVarSet subst fvs
= foldVarSet (unionVarSet . subst_fv subst) emptyVarSet fvs
where
subst_fv 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
simpleOptExpr expr
=
simpleOptExprWith init_subst expr
where
init_subst = mkEmptySubst (mkInScopeSet (exprFreeVars expr))
simpleOptExprWith :: Subst -> InExpr -> OutExpr
simpleOptExprWith subst expr = simple_opt_expr subst (occurAnalyseExpr expr)
simpleOptPgm :: DynFlags -> [CoreBind] -> [CoreRule] -> IO ([CoreBind], [CoreRule])
simpleOptPgm dflags binds rules
= do { dumpIfSet_dyn dflags Opt_D_dump_occur_anal "Occurrence analysis"
(pprCoreBindings occ_anald_binds);
; return (reverse binds', substRulesForImportedIds subst' rules) }
where
occ_anald_binds = occurAnalysePgm Nothing
rules 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
simple_opt_expr :: Subst -> InExpr -> OutExpr
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 (Lit lit) = Lit lit
go (Note note e) = Note note (go e)
go (Cast e co) | isIdentityCoercion co' = go e
| otherwise = Cast (go e) co'
where
co' = substTy 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 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 :: 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 :: Subst -> CoreBind -> (Subst, Maybe CoreBind)
simple_opt_bind subst (Rec prs)
= (subst'', Just (Rec (reverse rev_prs')))
where
(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 b r
| Type ty <- r
= ASSERT( isTyCoVar b )
Just (extendTvSubst subst b ty)
| isId b
, safe_to_inline (idOccInfo b)
, isAlwaysActive (idInlineActivation b)
, not (isStableUnfolding (idUnfolding b))
, not (isExportedId b)
= Just (extendIdSubst subst b r)
| otherwise
= Nothing
where
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
| isTyCoVar bndr = substTyVarBndr subst bndr
| otherwise = subst_opt_id_bndr subst bndr
subst_opt_id_bndr :: Subst -> InId -> (Subst, OutId)
subst_opt_id_bndr subst@(Subst in_scope id_subst tv_subst) old_id
= (Subst new_in_scope new_id_subst tv_subst, new_id)
where
id1 = uniqAway in_scope old_id
id2 = setIdType id1 (substTy subst (idType old_id))
new_id = zapFragileIdInfo id2
new_in_scope = in_scope `extendInScopeSet` new_id
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
| isTyCoVar 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