%
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section{SetLevels}
***************************
Overview
***************************
1. We attach binding levels to Core bindings, in preparation for floating
outwards (@FloatOut@).
2. We also let-ify many expressions (notably case scrutinees), so they
will have a fighting chance of being floated sensible.
3. We clone the binders of any floatable let-binding, so that when it is
floated out it will be unique. (This used to be done by the simplifier
but the latter now only ensures that there's no shadowing; indeed, even
that may not be true.)
NOTE: this can't be done using the uniqAway idea, because the variable
must be unique in the whole program, not just its current scope,
because two variables in different scopes may float out to the
same top level place
NOTE: Very tiresomely, we must apply this substitution to
the rules stored inside a variable too.
We do *not* clone top-level bindings, because some of them must not change,
but we *do* clone bindings that are heading for the top level
4. In the expression
case x of wild { p -> ...wild... }
we substitute x for wild in the RHS of the case alternatives:
case x of wild { p -> ...x... }
This means that a sub-expression involving x is not "trapped" inside the RHS.
And it's not inconvenient because we already have a substitution.
Note that this is EXACTLY BACKWARDS from the what the simplifier does.
The simplifier tries to get rid of occurrences of x, in favour of wild,
in the hope that there will only be one remaining occurrence of x, namely
the scrutinee of the case, and we can inline it.
\begin{code}
module SetLevels (
setLevels,
Level(..), tOP_LEVEL,
LevelledBind, LevelledExpr,
incMinorLvl, ltMajLvl, ltLvl, isTopLvl
) where
#include "HsVersions.h"
import CoreSyn
import CoreMonad ( FloatOutSwitches(..) )
import CoreUtils ( exprType, mkPiTypes )
import CoreArity ( exprBotStrictness_maybe )
import CoreFVs
import CoreSubst ( Subst, emptySubst, extendInScope, extendInScopeList,
extendIdSubst, cloneIdBndr, cloneRecIdBndrs )
import Id
import IdInfo
import Var
import VarSet
import VarEnv
import Demand ( StrictSig, increaseStrictSigArity )
import Name ( getOccName, mkSystemVarName )
import OccName ( occNameString )
import Type ( isUnLiftedType, Type )
import BasicTypes ( TopLevelFlag(..), Arity )
import UniqSupply
import Util
import Outputable
import FastString
\end{code}
%************************************************************************
%* *
\subsection{Level numbers}
%* *
%************************************************************************
\begin{code}
data Level = Level Int
Int
\end{code}
The {\em level number} on a (type-)lambda-bound variable is the
nesting depth of the (type-)lambda which binds it. The outermost lambda
has level 1, so (Level 0 0) means that the variable is bound outside any lambda.
On an expression, it's the maximum level number of its free
(type-)variables. On a let(rec)-bound variable, it's the level of its
RHS. On a case-bound variable, it's the number of enclosing lambdas.
Top-level variables: level~0. Those bound on the RHS of a top-level
definition but ``before'' a lambda; e.g., the \tr{x} in (levels shown
as ``subscripts'')...
\begin{verbatim}
a_0 = let b_? = ... in
x_1 = ... b ... in ...
\end{verbatim}
The main function @lvlExpr@ carries a ``context level'' (@ctxt_lvl@).
That's meant to be the level number of the enclosing binder in the
final (floated) program. If the level number of a sub-expression is
less than that of the context, then it might be worth let-binding the
sub-expression so that it will indeed float.
If you can float to level @Level 0 0@ worth doing so because then your
allocation becomes static instead of dynamic. We always start with
context @Level 0 0@.
Note [FloatOut inside INLINE]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@InlineCtxt@ very similar to @Level 0 0@, but is used for one purpose:
to say "don't float anything out of here". That's exactly what we
want for the body of an INLINE, where we don't want to float anything
out at all. See notes with lvlMFE below.
But, check this out:
-- At one time I tried the effect of not float anything out of an InlineMe,
-- but it sometimes works badly. For example, consider PrelArr.done. It
-- has the form __inline (\d. e)
-- where e doesn't mention d. If we float this to
-- __inline (let x = e in \d. x)
-- things are bad. The inliner doesn't even inline it because it doesn't look
-- like a head-normal form. So it seems a lesser evil to let things float.
-- In SetLevels we do set the context to (Level 0 0) when we get to an InlineMe
-- which discourages floating out.
So the conclusion is: don't do any floating at all inside an InlineMe.
(In the above example, don't float the {x=e} out of the \d.)
One particular case is that of workers: we don't want to float the
call to the worker outside the wrapper, otherwise the worker might get
inlined into the floated expression, and an importing module won't see
the worker at all.
\begin{code}
type LevelledExpr = TaggedExpr Level
type LevelledBind = TaggedBind Level
tOP_LEVEL :: Level
tOP_LEVEL = Level 0 0
incMajorLvl :: Level -> Level
incMajorLvl (Level major _) = Level (major + 1) 0
incMinorLvl :: Level -> Level
incMinorLvl (Level major minor) = Level major (minor+1)
maxLvl :: Level -> Level -> Level
maxLvl l1@(Level maj1 min1) l2@(Level maj2 min2)
| (maj1 > maj2) || (maj1 == maj2 && min1 > min2) = l1
| otherwise = l2
ltLvl :: Level -> Level -> Bool
ltLvl (Level maj1 min1) (Level maj2 min2)
= (maj1 < maj2) || (maj1 == maj2 && min1 < min2)
ltMajLvl :: Level -> Level -> Bool
ltMajLvl (Level maj1 _) (Level maj2 _) = maj1 < maj2
isTopLvl :: Level -> Bool
isTopLvl (Level 0 0) = True
isTopLvl _ = False
instance Outputable Level where
ppr (Level maj min) = hcat [ char '<', int maj, char ',', int min, char '>' ]
instance Eq Level where
(Level maj1 min1) == (Level maj2 min2) = maj1 == maj2 && min1 == min2
\end{code}
%************************************************************************
%* *
\subsection{Main level-setting code}
%* *
%************************************************************************
\begin{code}
setLevels :: FloatOutSwitches
-> [CoreBind]
-> UniqSupply
-> [LevelledBind]
setLevels float_lams binds us
= initLvl us (do_them init_env binds)
where
init_env = initialEnv float_lams
do_them :: LevelEnv -> [CoreBind] -> LvlM [LevelledBind]
do_them _ [] = return []
do_them env (b:bs)
= do { (lvld_bind, env') <- lvlTopBind env b
; lvld_binds <- do_them env' bs
; return (lvld_bind : lvld_binds) }
lvlTopBind :: LevelEnv -> Bind Id -> LvlM (LevelledBind, LevelEnv)
lvlTopBind env (NonRec binder rhs)
= lvlBind TopLevel tOP_LEVEL env (AnnNonRec binder (freeVars rhs))
lvlTopBind env (Rec pairs)
= lvlBind TopLevel tOP_LEVEL env (AnnRec [(b,freeVars rhs) | (b,rhs) <- pairs])
\end{code}
%************************************************************************
%* *
\subsection{Setting expression levels}
%* *
%************************************************************************
\begin{code}
lvlExpr :: Level
-> LevelEnv
-> CoreExprWithFVs
-> LvlM LevelledExpr
\end{code}
The @ctxt_lvl@ is, roughly, the level of the innermost enclosing
binder. Here's an example
v = \x -> ...\y -> let r = case (..x..) of
..x..
in ..
When looking at the rhs of @r@, @ctxt_lvl@ will be 1 because that's
the level of @r@, even though it's inside a level-2 @\y@. It's
important that @ctxt_lvl@ is 1 and not 2 in @r@'s rhs, because we
don't want @lvlExpr@ to turn the scrutinee of the @case@ into an MFE
--- because it isn't a *maximal* free expression.
If there were another lambda in @r@'s rhs, it would get level-2 as well.
\begin{code}
lvlExpr _ _ ( _, AnnType ty) = return (Type ty)
lvlExpr _ env (_, AnnVar v) = return (lookupVar env v)
lvlExpr _ _ (_, AnnLit lit) = return (Lit lit)
lvlExpr ctxt_lvl env expr@(_, AnnApp _ _) = do
let
(fun, args) = collectAnnArgs expr
case fun of
(_, AnnVar f) | floatPAPs env &&
arity > 0 && arity < n_val_args ->
do
let (lapp, rargs) = left (n_val_args arity) expr []
rargs' <- mapM (lvlMFE False ctxt_lvl env) rargs
lapp' <- lvlMFE False ctxt_lvl env lapp
return (foldl App lapp' rargs')
where
n_val_args = count (isValArg . deAnnotate) args
arity = idArity f
left 0 e rargs = (e, rargs)
left n (_, AnnApp f a) rargs
| isValArg (deAnnotate a) = left (n1) f (a:rargs)
| otherwise = left n f (a:rargs)
left _ _ _ = panic "SetLevels.lvlExpr.left"
_otherwise -> do
args' <- mapM (lvlMFE False ctxt_lvl env) args
fun' <- lvlExpr ctxt_lvl env fun
return (foldl App fun' args')
lvlExpr ctxt_lvl env (_, AnnNote note expr) = do
expr' <- lvlExpr ctxt_lvl env expr
return (Note note expr')
lvlExpr ctxt_lvl env (_, AnnCast expr co) = do
expr' <- lvlExpr ctxt_lvl env expr
return (Cast expr' co)
lvlExpr ctxt_lvl env expr@(_, AnnLam {}) = do
new_body <- lvlMFE True new_lvl new_env body
return (mkLams new_bndrs new_body)
where
(bndrs, body) = collectAnnBndrs expr
(new_lvl, new_bndrs) = lvlLamBndrs ctxt_lvl bndrs
new_env = extendLvlEnv env new_bndrs
lvlExpr ctxt_lvl env (_, AnnLet (AnnNonRec bndr rhs) body)
| isUnLiftedType (idType bndr) = do
rhs' <- lvlExpr ctxt_lvl env rhs
body' <- lvlExpr incd_lvl env' body
return (Let (NonRec bndr' rhs') body')
where
incd_lvl = incMinorLvl ctxt_lvl
bndr' = TB bndr incd_lvl
env' = extendLvlEnv env [bndr']
lvlExpr ctxt_lvl env (_, AnnLet bind body) = do
(bind', new_env) <- lvlBind NotTopLevel ctxt_lvl env bind
body' <- lvlExpr ctxt_lvl new_env body
return (Let bind' body')
lvlExpr ctxt_lvl env (_, AnnCase expr case_bndr ty alts) = do
expr' <- lvlMFE True ctxt_lvl env expr
let alts_env = extendCaseBndrLvlEnv env expr' case_bndr incd_lvl
alts' <- mapM (lvl_alt alts_env) alts
return (Case expr' (TB case_bndr incd_lvl) ty alts')
where
incd_lvl = incMinorLvl ctxt_lvl
lvl_alt alts_env (con, bs, rhs) = do
rhs' <- lvlMFE True incd_lvl new_env rhs
return (con, bs', rhs')
where
bs' = [ TB b incd_lvl | b <- bs ]
new_env = extendLvlEnv alts_env bs'
\end{code}
@lvlMFE@ is just like @lvlExpr@, except that it might let-bind
the expression, so that it can itself be floated.
Note [Unlifted MFEs]
~~~~~~~~~~~~~~~~~~~~
We don't float unlifted MFEs, which potentially loses big opportunites.
For example:
\x -> f (h y)
where h :: Int -> Int# is expensive. We'd like to float the (h y) outside
the \x, but we don't because it's unboxed. Possible solution: box it.
Note [Bottoming floats]
~~~~~~~~~~~~~~~~~~~~~~~
If we see
f = \x. g (error "urk")
we'd like to float the call to error, to get
lvl = error "urk"
f = \x. g lvl
Furthermore, we want to float a bottoming expression even if it has free
variables:
f = \x. g (let v = h x in error ("urk" ++ v))
Then we'd like to abstact over 'x' can float the whole arg of g:
lvl = \x. let v = h x in error ("urk" ++ v)
f = \x. g (lvl x)
See Maessen's paper 1999 "Bottom extraction: factoring error handling out
of functional programs" (unpublished I think).
When we do this, we set the strictness and arity of the new bottoming
Id, so that it's properly exposed as such in the interface file, even if
this is all happening after strictness analysis.
Note [Bottoming floats: eta expansion] c.f Note [Bottoming floats]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Tiresomely, though, the simplifier has an invariant that the manifest
arity of the RHS should be the same as the arity; but we can't call
etaExpand during SetLevels because it works over a decorated form of
CoreExpr. So we do the eta expansion later, in FloatOut.
Note [Case MFEs]
~~~~~~~~~~~~~~~~
We don't float a case expression as an MFE from a strict context. Why not?
Because in doing so we share a tiny bit of computation (the switch) but
in exchange we build a thunk, which is bad. This case reduces allocation
by 7% in spectral/puzzle (a rather strange benchmark) and 1.2% in real/fem.
Doesn't change any other allocation at all.
\begin{code}
lvlMFE :: Bool
-> Level
-> LevelEnv
-> CoreExprWithFVs
-> LvlM LevelledExpr
lvlMFE _ _ _ (_, AnnType ty)
= return (Type ty)
lvlMFE strict_ctxt ctxt_lvl env (_, AnnNote n e)
= do { e' <- lvlMFE strict_ctxt ctxt_lvl env e
; return (Note n e') }
lvlMFE strict_ctxt ctxt_lvl env (_, AnnCast e co)
= do { e' <- lvlMFE strict_ctxt ctxt_lvl env e
; return (Cast e' co) }
lvlMFE True ctxt_lvl env e@(_, AnnCase {})
= lvlExpr ctxt_lvl env e
lvlMFE strict_ctxt ctxt_lvl env ann_expr@(fvs, _)
| isUnLiftedType ty
|| notWorthFloating ann_expr abs_vars
|| not good_destination
=
lvlExpr ctxt_lvl env ann_expr
| otherwise
= do expr' <- lvlFloatRhs abs_vars dest_lvl env ann_expr
var <- newLvlVar abs_vars ty mb_bot
return (Let (NonRec (TB var dest_lvl) expr')
(mkVarApps (Var var) abs_vars))
where
expr = deAnnotate ann_expr
ty = exprType expr
mb_bot = exprBotStrictness_maybe expr
dest_lvl = destLevel env fvs (isFunction ann_expr) mb_bot
abs_vars = abstractVars dest_lvl env fvs
good_destination
| dest_lvl `ltMajLvl` ctxt_lvl
= True
| otherwise
= isTopLvl dest_lvl
&& floatConsts env
&& not strict_ctxt
annotateBotStr :: Id -> Maybe (Arity, StrictSig) -> Id
annotateBotStr id Nothing = id
annotateBotStr id (Just (arity,sig)) = id `setIdArity` arity
`setIdStrictness` sig
notWorthFloating :: CoreExprWithFVs -> [Var] -> Bool
notWorthFloating e abs_vars
= go e (count isId abs_vars)
where
go (_, AnnVar {}) n = n >= 0
go (_, AnnLit {}) n = n >= 0
go (_, AnnCast e _) n = go e n
go (_, AnnApp e arg) n
| (_, AnnType {}) <- arg = go e n
| n==0 = False
| is_triv arg = go e (n1)
| otherwise = False
go _ _ = False
is_triv (_, AnnLit {}) = True
is_triv (_, AnnVar {}) = True
is_triv (_, AnnCast e _) = is_triv e
is_triv (_, AnnApp e (_, AnnType {})) = is_triv e
is_triv _ = False
\end{code}
Note [Escaping a value lambda]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We want to float even cheap expressions out of value lambdas,
because that saves allocation. Consider
f = \x. .. (\y.e) ...
Then we'd like to avoid allocating the (\y.e) every time we call f,
(assuming e does not mention x).
An example where this really makes a difference is simplrun009.
Another reason it's good is because it makes SpecContr fire on functions.
Consider
f = \x. ....(f (\y.e))....
After floating we get
lvl = \y.e
f = \x. ....(f lvl)...
and that is much easier for SpecConstr to generate a robust specialisation for.
The OLD CODE (given where this Note is referred to) prevents floating
of the example above, so I just don't understand the old code. I
don't understand the old comment either (which appears below). I
measured the effect on nofib of changing OLD CODE to 'True', and got
zeros everywhere, but a 4% win for 'puzzle'. Very small 0.5% loss for
'cse'; turns out to be because our arity analysis isn't good enough
yet (mentioned in Simon-nofib-notes).
OLD comment was:
Even if it escapes a value lambda, we only
float if it's not cheap (unless it'll get all the
way to the top). I've seen cases where we
float dozens of tiny free expressions, which cost
more to allocate than to evaluate.
NB: exprIsCheap is also true of bottom expressions, which
is good; we don't want to share them
It's only Really Bad to float a cheap expression out of a
strict context, because that builds a thunk that otherwise
would never be built. So another alternative would be to
add
|| (strict_ctxt && not (exprIsBottom expr))
to the condition above. We should really try this out.
%************************************************************************
%* *
\subsection{Bindings}
%* *
%************************************************************************
The binding stuff works for top level too.
\begin{code}
lvlBind :: TopLevelFlag
-> Level
-> LevelEnv
-> CoreBindWithFVs
-> LvlM (LevelledBind, LevelEnv)
lvlBind top_lvl ctxt_lvl env (AnnNonRec bndr rhs@(rhs_fvs,_))
| isTyCoVar bndr
= do rhs' <- lvlExpr ctxt_lvl env rhs
return (NonRec (TB bndr ctxt_lvl) rhs', env)
| null abs_vars
= do
rhs' <- lvlExpr dest_lvl env rhs
(env', bndr') <- cloneVar top_lvl env bndr ctxt_lvl dest_lvl
return (NonRec (TB bndr' dest_lvl) rhs', env')
| otherwise
= do
rhs' <- lvlFloatRhs abs_vars dest_lvl env rhs
(env', [bndr']) <- newPolyBndrs dest_lvl env abs_vars [bndr_w_str]
return (NonRec (TB bndr' dest_lvl) rhs', env')
where
bind_fvs = rhs_fvs `unionVarSet` idFreeVars bndr
abs_vars = abstractVars dest_lvl env bind_fvs
dest_lvl = destLevel env bind_fvs (isFunction rhs) mb_bot
mb_bot = exprBotStrictness_maybe (deAnnotate rhs)
bndr_w_str = annotateBotStr bndr mb_bot
\end{code}
\begin{code}
lvlBind top_lvl ctxt_lvl env (AnnRec pairs)
| null abs_vars
= do (new_env, new_bndrs) <- cloneRecVars top_lvl env bndrs ctxt_lvl dest_lvl
new_rhss <- mapM (lvlExpr ctxt_lvl new_env) rhss
return (Rec ([TB b dest_lvl | b <- new_bndrs] `zip` new_rhss), new_env)
| isSingleton pairs && count isId abs_vars > 1
= do
let
(bndr,rhs) = head pairs
(rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
rhs_env = extendLvlEnv env abs_vars_w_lvls
(rhs_env', new_bndr) <- cloneVar NotTopLevel rhs_env bndr rhs_lvl rhs_lvl
let
(lam_bndrs, rhs_body) = collectAnnBndrs rhs
(body_lvl, new_lam_bndrs) = lvlLamBndrs rhs_lvl lam_bndrs
body_env = extendLvlEnv rhs_env' new_lam_bndrs
new_rhs_body <- lvlExpr body_lvl body_env rhs_body
(poly_env, [poly_bndr]) <- newPolyBndrs dest_lvl env abs_vars [bndr]
return (Rec [(TB poly_bndr dest_lvl,
mkLams abs_vars_w_lvls $
mkLams new_lam_bndrs $
Let (Rec [(TB new_bndr rhs_lvl, mkLams new_lam_bndrs new_rhs_body)])
(mkVarApps (Var new_bndr) lam_bndrs))],
poly_env)
| otherwise = do
(new_env, new_bndrs) <- newPolyBndrs dest_lvl env abs_vars bndrs
new_rhss <- mapM (lvlFloatRhs abs_vars dest_lvl new_env) rhss
return (Rec ([TB b dest_lvl | b <- new_bndrs] `zip` new_rhss), new_env)
where
(bndrs,rhss) = unzip pairs
bind_fvs = (unionVarSets [ idFreeVars bndr `unionVarSet` rhs_fvs
| (bndr, (rhs_fvs,_)) <- pairs])
`minusVarSet`
mkVarSet bndrs
dest_lvl = destLevel env bind_fvs (all isFunction rhss) Nothing
abs_vars = abstractVars dest_lvl env bind_fvs
lvlFloatRhs :: [CoreBndr] -> Level -> LevelEnv -> CoreExprWithFVs
-> UniqSM (Expr (TaggedBndr Level))
lvlFloatRhs abs_vars dest_lvl env rhs = do
rhs' <- lvlExpr rhs_lvl rhs_env rhs
return (mkLams abs_vars_w_lvls rhs')
where
(rhs_lvl, abs_vars_w_lvls) = lvlLamBndrs dest_lvl abs_vars
rhs_env = extendLvlEnv env abs_vars_w_lvls
\end{code}
%************************************************************************
%* *
\subsection{Deciding floatability}
%* *
%************************************************************************
\begin{code}
lvlLamBndrs :: Level -> [CoreBndr] -> (Level, [TaggedBndr Level])
lvlLamBndrs lvl []
= (lvl, [])
lvlLamBndrs lvl bndrs
= go (incMinorLvl lvl)
False
[] bndrs
where
go old_lvl bumped_major rev_lvld_bndrs (bndr:bndrs)
| isId bndr &&
not bumped_major &&
not (isOneShotLambda bndr)
= go new_lvl True (TB bndr new_lvl : rev_lvld_bndrs) bndrs
| otherwise
= go old_lvl bumped_major (TB bndr old_lvl : rev_lvld_bndrs) bndrs
where
new_lvl = incMajorLvl old_lvl
go old_lvl _ rev_lvld_bndrs []
= (old_lvl, reverse rev_lvld_bndrs)
\end{code}
\begin{code}
destLevel :: LevelEnv -> VarSet -> Bool -> Maybe (Arity, StrictSig) -> Level
destLevel env fvs is_function mb_bot
| Just {} <- mb_bot = tOP_LEVEL
| Just n_args <- floatLams env
, n_args > 0
, is_function
, countFreeIds fvs <= n_args
= tOP_LEVEL
| otherwise = maxIdLevel env fvs
isFunction :: CoreExprWithFVs -> Bool
isFunction (_, AnnLam b e) | isId b = True
| otherwise = isFunction e
isFunction (_, AnnNote _ e) = isFunction e
isFunction _ = False
countFreeIds :: VarSet -> Int
countFreeIds = foldVarSet add 0
where
add :: Var -> Int -> Int
add v n | isId v = n+1
| otherwise = n
\end{code}
%************************************************************************
%* *
\subsection{Free-To-Level Monad}
%* *
%************************************************************************
\begin{code}
data LevelEnv
= LE { le_switches :: FloatOutSwitches
, le_lvl_env :: VarEnv Level
, le_subst :: Subst
, le_env :: IdEnv ([Var], LevelledExpr)
}
initialEnv :: FloatOutSwitches -> LevelEnv
initialEnv float_lams
= LE { le_switches = float_lams, le_lvl_env = emptyVarEnv
, le_subst = emptySubst, le_env = emptyVarEnv }
floatLams :: LevelEnv -> Maybe Int
floatLams le = floatOutLambdas (le_switches le)
floatConsts :: LevelEnv -> Bool
floatConsts le = floatOutConstants (le_switches le)
floatPAPs :: LevelEnv -> Bool
floatPAPs le = floatOutPartialApplications (le_switches le)
extendLvlEnv :: LevelEnv -> [TaggedBndr Level] -> LevelEnv
extendLvlEnv le@(LE { le_lvl_env = lvl_env, le_subst = subst, le_env = id_env })
prs
= le { le_lvl_env = foldl add_lvl lvl_env prs
, le_subst = foldl del_subst subst prs
, le_env = foldl del_id id_env prs }
where
add_lvl env (TB v l) = extendVarEnv env v l
del_subst env (TB v _) = extendInScope env v
del_id env (TB v _) = delVarEnv env v
extendInScopeEnv :: LevelEnv -> Var -> LevelEnv
extendInScopeEnv le@(LE { le_subst = subst }) v
= le { le_subst = extendInScope subst v }
extendInScopeEnvList :: LevelEnv -> [Var] -> LevelEnv
extendInScopeEnvList le@(LE { le_subst = subst }) vs
= le { le_subst = extendInScopeList subst vs }
extendCaseBndrLvlEnv :: LevelEnv -> Expr (TaggedBndr Level) -> Var -> Level
-> LevelEnv
extendCaseBndrLvlEnv le@(LE { le_lvl_env = lvl_env, le_subst = subst, le_env = id_env })
(Var scrut_var) case_bndr lvl
= le { le_lvl_env = extendVarEnv lvl_env case_bndr lvl
, le_subst = extendIdSubst subst case_bndr (Var scrut_var)
, le_env = extendVarEnv id_env case_bndr ([scrut_var], Var scrut_var) }
extendCaseBndrLvlEnv env _scrut case_bndr lvl
= extendLvlEnv env [TB case_bndr lvl]
extendPolyLvlEnv :: Level -> LevelEnv -> [Var] -> [(Var, Var)] -> LevelEnv
extendPolyLvlEnv dest_lvl
le@(LE { le_lvl_env = lvl_env, le_subst = subst, le_env = id_env })
abs_vars bndr_pairs
= le { le_lvl_env = foldl add_lvl lvl_env bndr_pairs
, le_subst = foldl add_subst subst bndr_pairs
, le_env = foldl add_id id_env bndr_pairs }
where
add_lvl env (_, v') = extendVarEnv env v' dest_lvl
add_subst env (v, v') = extendIdSubst env v (mkVarApps (Var v') abs_vars)
add_id env (v, v') = extendVarEnv env v ((v':abs_vars), mkVarApps (Var v') abs_vars)
extendCloneLvlEnv :: Level -> LevelEnv -> Subst -> [(Var, Var)] -> LevelEnv
extendCloneLvlEnv lvl le@(LE { le_lvl_env = lvl_env, le_env = id_env })
new_subst bndr_pairs
= le { le_lvl_env = foldl add_lvl lvl_env bndr_pairs
, le_subst = new_subst
, le_env = foldl add_id id_env bndr_pairs }
where
add_lvl env (_, v') = extendVarEnv env v' lvl
add_id env (v, v') = extendVarEnv env v ([v'], Var v')
maxIdLevel :: LevelEnv -> VarSet -> Level
maxIdLevel (LE { le_lvl_env = lvl_env, le_env = id_env }) var_set
= foldVarSet max_in tOP_LEVEL var_set
where
max_in in_var lvl = foldr max_out lvl (case lookupVarEnv id_env in_var of
Just (abs_vars, _) -> abs_vars
Nothing -> [in_var])
max_out out_var lvl
| isId out_var = case lookupVarEnv lvl_env out_var of
Just lvl' -> maxLvl lvl' lvl
Nothing -> lvl
| otherwise = lvl
lookupVar :: LevelEnv -> Id -> LevelledExpr
lookupVar le v = case lookupVarEnv (le_env le) v of
Just (_, expr) -> expr
_ -> Var v
abstractVars :: Level -> LevelEnv -> VarSet -> [Var]
abstractVars dest_lvl (LE { le_lvl_env = lvl_env, le_env = id_env }) fvs
= map zap $ uniq $ sortLe le
[var | fv <- varSetElems fvs
, var <- absVarsOf id_env fv
, abstract_me var ]
where
v1 `le` v2 = case (is_tv v1, is_tv v2) of
(True, False) -> True
(False, True) -> False
_ -> v1 <= v2
is_tv v = isTyCoVar v && not (isCoVar v)
uniq :: [Var] -> [Var]
uniq (v1:v2:vs) | v1 == v2 = uniq (v2:vs)
| otherwise = v1 : uniq (v2:vs)
uniq vs = vs
abstract_me v = case lookupVarEnv lvl_env v of
Just lvl -> dest_lvl `ltLvl` lvl
Nothing -> False
zap v | isId v = WARN( isStableUnfolding (idUnfolding v) ||
not (isEmptySpecInfo (idSpecialisation v)),
text "absVarsOf: discarding info on" <+> ppr v )
setIdInfo v vanillaIdInfo
| otherwise = v
absVarsOf :: IdEnv ([Var], LevelledExpr) -> Var -> [Var]
absVarsOf id_env v
| isId v = [av2 | av1 <- lookup_avs v
, av2 <- add_tyvars av1]
| isCoVar v = add_tyvars v
| otherwise = [v]
where
lookup_avs v = case lookupVarEnv id_env v of
Just (abs_vars, _) -> abs_vars
Nothing -> [v]
add_tyvars v = v : varSetElems (varTypeTyVars v)
\end{code}
\begin{code}
type LvlM result = UniqSM result
initLvl :: UniqSupply -> UniqSM a -> a
initLvl = initUs_
\end{code}
\begin{code}
newPolyBndrs :: Level -> LevelEnv -> [Var] -> [Id] -> UniqSM (LevelEnv, [Id])
newPolyBndrs dest_lvl env abs_vars bndrs = do
uniqs <- getUniquesM
let new_bndrs = zipWith mk_poly_bndr bndrs uniqs
return (extendPolyLvlEnv dest_lvl env abs_vars (bndrs `zip` new_bndrs), new_bndrs)
where
mk_poly_bndr bndr uniq = transferPolyIdInfo bndr abs_vars $
mkSysLocal (mkFastString str) uniq poly_ty
where
str = "poly_" ++ occNameString (getOccName bndr)
poly_ty = mkPiTypes abs_vars (idType bndr)
newLvlVar :: [CoreBndr] -> Type
-> Maybe (Arity, StrictSig)
-> LvlM Id
newLvlVar vars body_ty mb_bot
= do { uniq <- getUniqueM
; return (mkLocalIdWithInfo (mk_name uniq) (mkPiTypes vars body_ty) info) }
where
mk_name uniq = mkSystemVarName uniq (mkFastString "lvl")
arity = count isId vars
info = case mb_bot of
Nothing -> vanillaIdInfo
Just (bot_arity, sig) -> vanillaIdInfo
`setArityInfo` (arity + bot_arity)
`setStrictnessInfo` Just (increaseStrictSigArity arity sig)
cloneVar :: TopLevelFlag -> LevelEnv -> Id -> Level -> Level -> LvlM (LevelEnv, Id)
cloneVar TopLevel env v _ _
= return (extendInScopeEnv env v, v)
cloneVar NotTopLevel env v ctxt_lvl dest_lvl
= ASSERT( isId v ) do
us <- getUniqueSupplyM
let
(subst', v1) = cloneIdBndr (le_subst env) us v
v2 = zap_demand ctxt_lvl dest_lvl v1
env' = extendCloneLvlEnv dest_lvl env subst' [(v,v2)]
return (env', v2)
cloneRecVars :: TopLevelFlag -> LevelEnv -> [Id] -> Level -> Level -> LvlM (LevelEnv, [Id])
cloneRecVars TopLevel env vs _ _
= return (extendInScopeEnvList env vs, vs)
cloneRecVars NotTopLevel env vs ctxt_lvl dest_lvl
= ASSERT( all isId vs ) do
us <- getUniqueSupplyM
let
(subst', vs1) = cloneRecIdBndrs (le_subst env) us vs
vs2 = map (zap_demand ctxt_lvl dest_lvl) vs1
env' = extendCloneLvlEnv dest_lvl env subst' (vs `zip` vs2)
return (env', vs2)
zap_demand :: Level -> Level -> Id -> Id
zap_demand dest_lvl ctxt_lvl id
| ctxt_lvl == dest_lvl,
not (isTopLvl dest_lvl) = id
| otherwise = zapDemandIdInfo id
\end{code}