import FastTypes hiding ( fastOr )
import Outputable
-import List ( partition )
-
infixr 9 `thenLne`
\end{code}
the actual nested SRTs, and replaces the lists of Ids with (offset,length)
pairs.
+
+Interaction of let-no-escape with SRTs [Sept 01]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider
+
+ let-no-escape x = ...caf1...caf2...
+ in
+ ...x...x...x...
+
+where caf1,caf2 are CAFs. Since x doesn't have a closure, we
+build SRTs just as if x's defn was inlined at each call site, and
+that means that x's CAF refs get duplicated in the overall SRT.
+
+This is unlike ordinary lets, in which the CAF refs are not duplicated.
+
+We could fix this loss of (static) sharing by making a sort of pseudo-closure
+for x, solely to put in the SRTs lower down.
+
+
%************************************************************************
%* *
\subsection[binds-StgVarInfo]{Setting variable info: top-level, binds, RHSs}
coreTopBindToStg env body_fvs (NonRec id rhs)
= let
- caf_info = hasCafRefs env rhs
-
- env' = extendVarEnv env id (LetBound how_bound emptyLVS (predictArity rhs))
-
- how_bound | mayHaveCafRefs caf_info = TopLevelHasCafs
- | otherwise = TopLevelNoCafs
+ caf_info = hasCafRefs env rhs
+ env' = extendVarEnv env id how_bound
+ how_bound = LetBound (TopLet caf_info) (predictArity rhs)
- (stg_rhs, fvs', cafs) =
+ (stg_rhs, fvs', lv_info) =
initLne env (
- coreToStgRhs body_fvs TopLevel (id,rhs)
- `thenLne` \ (stg_rhs, fvs', _) ->
- freeVarsToLiveVars fvs' `thenLne` \ (_, cafs) ->
- returnLne (stg_rhs, fvs', cafs)
+ coreToStgRhs body_fvs TopLevel (id,rhs) `thenLne` \ (stg_rhs, fvs', _) ->
+ freeVarsToLiveVars fvs' `thenLne` \ lv_info ->
+ returnLne (stg_rhs, fvs', lv_info)
)
- bind = StgNonRec (SRTEntries cafs) id stg_rhs
+ bind = StgNonRec (mkSRT lv_info) id stg_rhs
in
ASSERT2(predictArity rhs == stgRhsArity stg_rhs, ppr id)
ASSERT2(consistent caf_info bind, ppr id)
= let
(binders, rhss) = unzip pairs
- -- to calculate caf_info, we initially map all the binders to
- -- TopLevelNoCafs.
+ -- To calculate caf_info, we initially map
+ -- all the binders to NoCafRefs
env1 = extendVarEnvList env
- [ (b, LetBound TopLevelNoCafs emptyLVS (error "no arity"))
+ [ (b, LetBound (TopLet NoCafRefs) (error "no arity"))
| b <- binders ]
caf_info = hasCafRefss env1{-NB: not env'-} rhss
env' = extendVarEnvList env
- [ (b, LetBound how_bound emptyLVS (predictArity rhs))
+ [ (b, LetBound (TopLet caf_info) (predictArity rhs))
| (b,rhs) <- pairs ]
- how_bound | mayHaveCafRefs caf_info = TopLevelHasCafs
- | otherwise = TopLevelNoCafs
-
- (stg_rhss, fvs', cafs)
+ (stg_rhss, fvs', lv_info)
= initLne env' (
mapAndUnzip3Lne (coreToStgRhs body_fvs TopLevel) pairs
`thenLne` \ (stg_rhss, fvss', _) ->
let fvs' = unionFVInfos fvss' in
- freeVarsToLiveVars fvs' `thenLne` \ (_, cafs) ->
- returnLne (stg_rhss, fvs', cafs)
+ freeVarsToLiveVars fvs' `thenLne` \ lv_info ->
+ returnLne (stg_rhss, fvs', lv_info)
)
- bind = StgRec (SRTEntries cafs) (zip binders stg_rhss)
+ bind = StgRec (mkSRT lv_info) (zip binders stg_rhss)
in
ASSERT2(and [predictArity rhs == stgRhsArity stg_rhs | (rhs,stg_rhs) <- rhss `zip` stg_rhss], ppr binders)
ASSERT2(consistent caf_info bind, ppr binders)
(f, args) = myCollectArgs expr
coreToStgExpr expr@(Lam _ _)
- = let (args, body) = myCollectBinders expr
+ = let
+ (args, body) = myCollectBinders expr
args' = filterStgBinders args
in
extendVarEnvLne [ (a, LambdaBound) | a <- args' ] $
coreToStgExpr body `thenLne` \ (body, body_fvs, body_escs) ->
let
- set_of_args = mkVarSet args'
fvs = args' `minusFVBinders` body_fvs
- escs = body_escs `minusVarSet` set_of_args
+ escs = body_escs `delVarSetList` args'
result_expr | null args' = body
| otherwise = StgLam (exprType expr) args' body
in
coreToStgExpr (Note other_note expr)
= coreToStgExpr expr
-
-- Cases require a little more real work.
coreToStgExpr (Case scrut bndr alts)
- = extendVarEnvLne [(bndr, CaseBound)] $
- vars_alts (findDefault alts) `thenLne` \ (alts2, alts_fvs, alts_escs) ->
- freeVarsToLiveVars alts_fvs `thenLne` \ (alts_lvs, alts_caf_refs) ->
+ = extendVarEnvLne [(bndr, LambdaBound)] (
+ mapAndUnzip3Lne vars_alt alts `thenLne` \ (alts2, fvs_s, escs_s) ->
+ returnLne ( mkStgAlts (idType bndr) alts2,
+ unionFVInfos fvs_s,
+ unionVarSets escs_s )
+ ) `thenLne` \ (alts2, alts_fvs, alts_escs) ->
let
- -- determine whether the default binder is dead or not
+ -- Determine whether the default binder is dead or not
-- This helps the code generator to avoid generating an assignment
-- for the case binder (is extremely rare cases) ToDo: remove.
- bndr'= if (bndr `elementOfFVInfo` alts_fvs)
- then bndr
- else bndr `setIdOccInfo` IAmDead
+ bndr' | bndr `elementOfFVInfo` alts_fvs = bndr
+ | otherwise = bndr `setIdOccInfo` IAmDead
-- Don't consider the default binder as being 'live in alts',
-- since this is from the point of view of the case expr, where
-- the default binder is not free.
- live_in_alts = (alts_lvs `minusVarSet` unitVarSet bndr)
+ alts_fvs_wo_bndr = bndr `minusFVBinder` alts_fvs
+ alts_escs_wo_bndr = alts_escs `delVarSet` bndr
in
- -- we tell the scrutinee that everything live in the alts
- -- is live in it, too.
- setVarsLiveInCont (live_in_alts,alts_caf_refs) (
+
+ freeVarsToLiveVars alts_fvs_wo_bndr `thenLne` \ alts_lv_info ->
+
+ -- We tell the scrutinee that everything
+ -- live in the alts is live in it, too.
+ setVarsLiveInCont alts_lv_info (
coreToStgExpr scrut `thenLne` \ (scrut2, scrut_fvs, scrut_escs) ->
- freeVarsToLiveVars scrut_fvs `thenLne` \ (scrut_lvs, _) ->
- returnLne (scrut2, scrut_fvs, scrut_escs, scrut_lvs)
+ freeVarsToLiveVars scrut_fvs `thenLne` \ scrut_lv_info ->
+ returnLne (scrut2, scrut_fvs, scrut_escs, scrut_lv_info)
)
- `thenLne` \ (scrut2, scrut_fvs, scrut_escs, scrut_lvs) ->
+ `thenLne` \ (scrut2, scrut_fvs, scrut_escs, scrut_lv_info) ->
- let srt = SRTEntries alts_caf_refs
- in
returnLne (
- StgCase scrut2 scrut_lvs live_in_alts bndr' srt alts2,
- bndr `minusFVBinder` (scrut_fvs `unionFVInfo` alts_fvs),
- (alts_escs `minusVarSet` unitVarSet bndr) `unionVarSet` getFVSet scrut_fvs
+ StgCase scrut2 (getLiveVars scrut_lv_info)
+ (getLiveVars alts_lv_info)
+ bndr'
+ (mkSRT alts_lv_info)
+ alts2,
+ scrut_fvs `unionFVInfo` alts_fvs_wo_bndr,
+ alts_escs_wo_bndr `unionVarSet` getFVSet scrut_fvs
-- You might think we should have scrut_escs, not
-- (getFVSet scrut_fvs), but actually we can't call, and
-- then return from, a let-no-escape thing.
)
where
- scrut_ty = idType bndr
- prim_case = isUnLiftedType scrut_ty && not (isUnboxedTupleType scrut_ty)
-
- vars_alts (alts,deflt)
- | prim_case
- = mapAndUnzip3Lne vars_prim_alt alts
- `thenLne` \ (alts2, alts_fvs_list, alts_escs_list) ->
- let
- alts_fvs = unionFVInfos alts_fvs_list
- alts_escs = unionVarSets alts_escs_list
- in
- vars_deflt deflt `thenLne` \ (deflt2, deflt_fvs, deflt_escs) ->
- returnLne (
- mkStgPrimAlts scrut_ty alts2 deflt2,
- alts_fvs `unionFVInfo` deflt_fvs,
- alts_escs `unionVarSet` deflt_escs
- )
-
- | otherwise
- = mapAndUnzip3Lne vars_alg_alt alts
- `thenLne` \ (alts2, alts_fvs_list, alts_escs_list) ->
- let
- alts_fvs = unionFVInfos alts_fvs_list
- alts_escs = unionVarSets alts_escs_list
- in
- vars_deflt deflt `thenLne` \ (deflt2, deflt_fvs, deflt_escs) ->
- returnLne (
- mkStgAlgAlts scrut_ty alts2 deflt2,
- alts_fvs `unionFVInfo` deflt_fvs,
- alts_escs `unionVarSet` deflt_escs
- )
-
- where
- vars_prim_alt (LitAlt lit, _, rhs)
- = coreToStgExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
- returnLne ((lit, rhs2), rhs_fvs, rhs_escs)
-
- vars_alg_alt (DataAlt con, binders, rhs)
- = let
- -- remove type variables
- binders' = filterStgBinders binders
- in
- extendVarEnvLne [(b, CaseBound) | b <- binders'] $
- coreToStgExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
- let
- good_use_mask = [ b `elementOfFVInfo` rhs_fvs | b <- binders' ]
- -- records whether each param is used in the RHS
- in
- returnLne (
- (con, binders', good_use_mask, rhs2),
- binders' `minusFVBinders` rhs_fvs,
- rhs_escs `minusVarSet` mkVarSet binders'
- -- ToDo: remove the minusVarSet;
- -- since escs won't include any of these binders
- )
- vars_alg_alt other = pprPanic "vars_alg_alt" (ppr other)
-
- vars_deflt Nothing
- = returnLne (StgNoDefault, emptyFVInfo, emptyVarSet)
-
- vars_deflt (Just rhs)
- = coreToStgExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
- returnLne (StgBindDefault rhs2, rhs_fvs, rhs_escs)
+ vars_alt (con, binders, rhs)
+ = let -- Remove type variables
+ binders' = filterStgBinders binders
+ in
+ extendVarEnvLne [(b, LambdaBound) | b <- binders'] $
+ coreToStgExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
+ let
+ -- Records whether each param is used in the RHS
+ good_use_mask = [ b `elementOfFVInfo` rhs_fvs | b <- binders' ]
+ in
+ returnLne ( (con, binders', good_use_mask, rhs2),
+ binders' `minusFVBinders` rhs_fvs,
+ rhs_escs `delVarSetList` binders' )
+ -- ToDo: remove the delVarSet;
+ -- since escs won't include any of these binders
\end{code}
Lets not only take quite a bit of work, but this is where we convert
\end{code}
\begin{code}
-mkStgAlgAlts ty alts deflt
- = case alts of
- -- Get the tycon from the data con
- (dc, _, _, _) : _rest
- -> StgAlgAlts (Just (dataConTyCon dc)) alts deflt
-
- -- Otherwise just do your best
- [] -> case splitTyConApp_maybe (repType ty) of
- Just (tc,_) | isAlgTyCon tc
- -> StgAlgAlts (Just tc) alts deflt
- other
- -> StgAlgAlts Nothing alts deflt
-
-mkStgPrimAlts ty alts deflt
- = StgPrimAlts (tyConAppTyCon ty) alts deflt
+mkStgAlts scrut_ty orig_alts
+ | is_prim_case = StgPrimAlts (tyConAppTyCon scrut_ty) prim_alts deflt
+ | otherwise = StgAlgAlts maybe_tycon alg_alts deflt
+ where
+ is_prim_case = isUnLiftedType scrut_ty && not (isUnboxedTupleType scrut_ty)
+
+ prim_alts = [(lit, rhs) | (LitAlt lit, _, _, rhs) <- other_alts]
+ alg_alts = [(con, bndrs, use, rhs) | (DataAlt con, bndrs, use, rhs) <- other_alts]
+
+ (other_alts, deflt)
+ = case orig_alts of -- DEFAULT is always first if it's there at all
+ (DEFAULT, _, _, rhs) : other_alts -> (other_alts, StgBindDefault rhs)
+ other -> (orig_alts, StgNoDefault)
+
+ maybe_tycon = case alg_alts of
+ -- Get the tycon from the data con
+ (dc, _, _, _) : _rest -> Just (dataConTyCon dc)
+
+ -- Otherwise just do your best
+ [] -> case splitTyConApp_maybe (repType scrut_ty) of
+ Just (tc,_) | isAlgTyCon tc -> Just tc
+ _other -> Nothing
\end{code}
-- let f = \ab -> e in f
-- No point in having correct arity info for f!
-- Hence the hasArity stuff below.
+ -- NB: f_arity is only consulted for LetBound things
f_arity = case how_bound of
- LetBound _ _ arity -> arity
- _ -> 0
+ LetBound _ arity -> arity
fun_occ
| not_letrec_bound = noBinderInfo -- Uninteresting variable
-- is among the escaping vars
coreToStgLet let_no_escape bind body
- = fixLne (\ ~(_, _, _, _, _, _, rec_body_fvs, _, _) ->
+ = fixLne (\ ~(_, _, _, _, _, rec_body_fvs, _, _) ->
-- Do the bindings, setting live_in_cont to empty if
-- we ain't in a let-no-escape world
getVarsLiveInCont `thenLne` \ live_in_cont ->
setVarsLiveInCont (if let_no_escape
then live_in_cont
- else emptyLVS)
+ else emptyLiveInfo)
(vars_bind rec_body_fvs bind)
- `thenLne` \ ( bind2, bind_fvs, bind_escs
- , bind_lvs, bind_cafs, env_ext) ->
+ `thenLne` \ ( bind2, bind_fvs, bind_escs, bind_lv_info, env_ext) ->
-- Do the body
extendVarEnvLne env_ext (
coreToStgExpr body `thenLne` \(body2, body_fvs, body_escs) ->
- freeVarsToLiveVars body_fvs `thenLne` \(body_lvs, _) ->
+ freeVarsToLiveVars body_fvs `thenLne` \ body_lv_info ->
- returnLne (bind2, bind_fvs, bind_escs, bind_lvs, bind_cafs,
- body2, body_fvs, body_escs, body_lvs)
+ returnLne (bind2, bind_fvs, bind_escs, getLiveVars bind_lv_info,
+ body2, body_fvs, body_escs, getLiveVars body_lv_info)
)
- ) `thenLne` (\ (bind2, bind_fvs, bind_escs, bind_lvs, bind_cafs,
+ ) `thenLne` (\ (bind2, bind_fvs, bind_escs, bind_lvs,
body2, body_fvs, body_escs, body_lvs) ->
= binders `minusFVBinders` (bind_fvs `unionFVInfo` body_fvs)
live_in_whole_let
- = bind_lvs `unionVarSet` (body_lvs `minusVarSet` set_of_binders)
+ = bind_lvs `unionVarSet` (body_lvs `delVarSetList` binders)
real_bind_escs = if let_no_escape then
bind_escs
getFVSet bind_fvs
-- Everything escapes which is free in the bindings
- let_escs = (real_bind_escs `unionVarSet` body_escs) `minusVarSet` set_of_binders
+ let_escs = (real_bind_escs `unionVarSet` body_escs) `delVarSetList` binders
all_escs = bind_escs `unionVarSet` body_escs -- Still includes binders of
-- this let(rec)
))
where
set_of_binders = mkVarSet binders
- binders = case bind of
- NonRec binder rhs -> [binder]
- Rec pairs -> map fst pairs
+ binders = bindersOf bind
- mk_binding bind_lvs bind_cafs binder rhs
- = (binder, LetBound NotTopLevelBound -- Not top level
- live_vars (predictArity rhs)
- )
+ mk_binding bind_lv_info binder rhs
+ = (binder, LetBound (NestedLet live_vars) (predictArity rhs))
where
- live_vars = if let_no_escape then
- (extendVarSet bind_lvs binder, bind_cafs)
- else
- (unitVarSet binder, emptyVarSet)
+ live_vars | let_no_escape = addLiveVar bind_lv_info binder
+ | otherwise = unitLiveVar binder
+ -- c.f. the invariant on NestedLet
vars_bind :: FreeVarsInfo -- Free var info for body of binding
-> CoreBind
-> LneM (StgBinding,
FreeVarsInfo,
EscVarsSet, -- free vars; escapee vars
- StgLiveVars, -- vars live in binding
- IdSet, -- CAFs live in binding
+ LiveInfo, -- Vars and CAFs live in binding
[(Id, HowBound)]) -- extension to environment
= coreToStgRhs body_fvs NotTopLevel (binder,rhs)
`thenLne` \ (rhs2, bind_fvs, escs) ->
- freeVarsToLiveVars bind_fvs `thenLne` \ (bind_lvs, bind_cafs) ->
+ freeVarsToLiveVars bind_fvs `thenLne` \ bind_lv_info ->
let
- env_ext_item = mk_binding bind_lvs bind_cafs binder rhs
+ env_ext_item = mk_binding bind_lv_info binder rhs
in
- returnLne (StgNonRec (SRTEntries bind_cafs) binder rhs2,
- bind_fvs, escs, bind_lvs, bind_cafs, [env_ext_item])
+ returnLne (StgNonRec (mkSRT bind_lv_info) binder rhs2,
+ bind_fvs, escs, bind_lv_info, [env_ext_item])
vars_bind body_fvs (Rec pairs)
- = fixLne (\ ~(_, rec_rhs_fvs, _, bind_lvs, bind_cafs, _) ->
+ = fixLne (\ ~(_, rec_rhs_fvs, _, bind_lv_info, _) ->
let
rec_scope_fvs = unionFVInfo body_fvs rec_rhs_fvs
binders = map fst pairs
- env_ext = [ mk_binding bind_lvs bind_cafs b rhs
+ env_ext = [ mk_binding bind_lv_info b rhs
| (b,rhs) <- pairs ]
in
extendVarEnvLne env_ext (
escs = unionVarSets escss
in
freeVarsToLiveVars (binders `minusFVBinders` bind_fvs)
- `thenLne` \ (bind_lvs, bind_cafs) ->
+ `thenLne` \ bind_lv_info ->
- returnLne (StgRec (SRTEntries bind_cafs) (binders `zip` rhss2),
- bind_fvs, escs, bind_lvs, bind_cafs, env_ext)
+ returnLne (StgRec (mkSRT bind_lv_info) (binders `zip` rhss2),
+ bind_fvs, escs, bind_lv_info, env_ext)
)
)
\begin{code}
type LneM a = IdEnv HowBound
- -> (StgLiveVars, -- vars live in continuation
- IdSet) -- cafs live in continuation
+ -> LiveInfo -- Vars and CAFs live in continuation
-> a
+type LiveInfo = (StgLiveVars, -- Dynamic live variables;
+ -- i.e. ones with a nested (non-top-level) binding
+ CafSet) -- Static live variables;
+ -- i.e. top-level variables that are CAFs or refer to them
+
+type EscVarsSet = IdSet
+type CafSet = IdSet
+
data HowBound
= ImportBound -- Used only as a response to lookupBinding; never
-- exists in the range of the (IdEnv HowBound)
- | CaseBound
- | LambdaBound
- | LetBound
- TopLevelCafInfo
- (StgLiveVars, IdSet) -- (Live vars, Live CAFs)... see notes below
- Arity -- its arity (local Ids don't have arity info at this point)
-
-isLetBound (LetBound _ _ _) = True
-isLetBound other = False
+
+ | LetBound -- A let(rec) in this module
+ LetInfo -- Whether top level or nested
+ Arity -- Its arity (local Ids don't have arity info at this point)
+
+ | LambdaBound -- Used for both lambda and case
+
+data LetInfo = NestedLet LiveInfo -- For nested things, what is live if this thing is live?
+ -- Invariant: the binder itself is always a member of
+ -- the dynamic set of its own LiveInfo
+ | TopLet CafInfo -- For top level things, is it a CAF, or can it refer to one?
+
+isLetBound (LetBound _ _) = True
+isLetBound other = False
+
+topLevelBound ImportBound = True
+topLevelBound (LetBound (TopLet _) _) = True
+topLevelBound other = False
\end{code}
-For a let(rec)-bound variable, x, we record StgLiveVars, the set of
-variables that are live if x is live. For "normal" variables that is
-just x alone. If x is a let-no-escaped variable then x is represented
-by a code pointer and a stack pointer (well, one for each stack). So
-all of the variables needed in the execution of x are live if x is,
-and are therefore recorded in the LetBound constructor; x itself
-*is* included.
+For a let(rec)-bound variable, x, we record LiveInfo, the set of
+variables that are live if x is live. This LiveInfo comprises
+ (a) dynamic live variables (ones with a non-top-level binding)
+ (b) static live variabes (CAFs or things that refer to CAFs)
-The set of live variables is guaranteed ot have no further let-no-escaped
+For "normal" variables (a) is just x alone. If x is a let-no-escaped
+variable then x is represented by a code pointer and a stack pointer
+(well, one for each stack). So all of the variables needed in the
+execution of x are live if x is, and are therefore recorded in the
+LetBound constructor; x itself *is* included.
+
+The set of dynamic live variables is guaranteed ot have no further let-no-escaped
variables in it.
+\begin{code}
+emptyLiveInfo :: LiveInfo
+emptyLiveInfo = (emptyVarSet,emptyVarSet)
+
+unitLiveVar :: Id -> LiveInfo
+unitLiveVar lv = (unitVarSet lv, emptyVarSet)
+
+unitLiveCaf :: Id -> LiveInfo
+unitLiveCaf caf = (emptyVarSet, unitVarSet caf)
+
+addLiveVar :: LiveInfo -> Id -> LiveInfo
+addLiveVar (lvs, cafs) id = (lvs `extendVarSet` id, cafs)
+
+deleteLiveVar :: LiveInfo -> Id -> LiveInfo
+deleteLiveVar (lvs, cafs) id = (lvs `delVarSet` id, cafs)
+
+unionLiveInfo :: LiveInfo -> LiveInfo -> LiveInfo
+unionLiveInfo (lv1,caf1) (lv2,caf2) = (lv1 `unionVarSet` lv2, caf1 `unionVarSet` caf2)
+
+unionLiveInfos :: [LiveInfo] -> LiveInfo
+unionLiveInfos lvs = foldr unionLiveInfo emptyLiveInfo lvs
+
+mkSRT :: LiveInfo -> SRT
+mkSRT (_, cafs) = SRTEntries cafs
+
+getLiveVars :: LiveInfo -> StgLiveVars
+getLiveVars (lvs, _) = lvs
+\end{code}
+
+
The std monad functions:
\begin{code}
initLne :: IdEnv HowBound -> LneM a -> a
-initLne env m = m env emptyLVS
+initLne env m = m env emptyLiveInfo
+
-emptyLVS = (emptyVarSet,emptyVarSet)
{-# INLINE thenLne #-}
{-# INLINE returnLne #-}
Functions specific to this monad:
\begin{code}
-getVarsLiveInCont :: LneM (StgLiveVars, IdSet)
+getVarsLiveInCont :: LneM LiveInfo
getVarsLiveInCont env lvs_cont = lvs_cont
-setVarsLiveInCont :: (StgLiveVars,IdSet) -> LneM a -> LneM a
+setVarsLiveInCont :: LiveInfo -> LneM a -> LneM a
setVarsLiveInCont new_lvs_cont expr env lvs_cont
= expr env new_lvs_cont
-- only ever tacked onto a decorated expression. It is never used as
-- the basis of a control decision, which might give a black hole.
-freeVarsToLiveVars :: FreeVarsInfo -> LneM (StgLiveVars, IdSet)
+freeVarsToLiveVars :: FreeVarsInfo -> LneM LiveInfo
freeVarsToLiveVars fvs env live_in_cont
- = returnLne (lvs, cafs) env live_in_cont
+ = returnLne live_info env live_in_cont
where
- (lvs_cont, cafs_cont) = live_in_cont -- not a strict pattern match!
-
- (lvs_from_fvs, caf_from_fvs) = unzip (map do_one (allFreeIds fvs))
-
- lvs = unionVarSets lvs_from_fvs `unionVarSet` lvs_cont
- cafs = unionVarSets caf_from_fvs `unionVarSet` cafs_cont
+ live_info = foldr unionLiveInfo live_in_cont lvs_from_fvs
+ lvs_from_fvs = map do_one (allFreeIds fvs)
- do_one v
- = case lookupBinding env v of
- LetBound caf_ness (lvs,cafs) _ ->
- case caf_ness of
- TopLevelHasCafs -> ASSERT( isEmptyVarSet lvs ) (emptyVarSet, unitVarSet v)
- TopLevelNoCafs -> ASSERT( isEmptyVarSet lvs ) (emptyVarSet, emptyVarSet)
- NotTopLevelBound -> (extendVarSet lvs v, cafs)
+ do_one (v, how_bound)
+ = case how_bound of
+ ImportBound -> unitLiveCaf v -- Only CAF imports are
+ -- recorded in fvs
+ LetBound (TopLet caf_info) _
+ | mayHaveCafRefs caf_info -> unitLiveCaf v
+ | otherwise -> emptyLiveInfo
- ImportBound | mayHaveCafRefs (idCafInfo v) -> (emptyVarSet, unitVarSet v)
- | otherwise -> (emptyVarSet, emptyVarSet)
+ LetBound (NestedLet lvs) _ -> lvs -- lvs already contains v
+ -- (see the invariant on NestedLet)
- _nested_binding -> (unitVarSet v, emptyVarSet) -- Bound by lambda or case
+ _lambda_or_case_binding -> unitLiveVar v -- Bound by lambda or case
\end{code}
%************************************************************************
%************************************************************************
\begin{code}
-type FreeVarsInfo = VarEnv (Var, TopLevelCafInfo, StgBinderInfo)
+type FreeVarsInfo = VarEnv (Var, HowBound, StgBinderInfo)
+ -- The Var is so we can gather up the free variables
+ -- as a set.
+ --
+ -- The HowBound info just saves repeated lookups;
+ -- we look up just once when we encounter the occurrence.
+ -- INVARIANT: Any ImportBound Ids are HaveCafRef Ids
+ -- Imported Ids without CAF refs are simply
+ -- not put in the FreeVarsInfo for an expression;
+ -- see singletonFVInfo
+ --
+ -- StgBinderInfo
-- If f is mapped to noBinderInfo, that means
-- that f *is* mentioned (else it wouldn't be in the
-- IdEnv at all), but perhaps in an unsaturated applications.
--
-- For ILX we track free var info for type variables too;
-- hence VarEnv not IdEnv
-
-data TopLevelCafInfo
- = NotTopLevelBound
- | TopLevelNoCafs
- | TopLevelHasCafs
- deriving Eq
-
-type EscVarsSet = IdSet
\end{code}
\begin{code}
emptyFVInfo = emptyVarEnv
singletonFVInfo :: Id -> HowBound -> StgBinderInfo -> FreeVarsInfo
+-- Don't record non-CAF imports at all, to keep free-var sets small
singletonFVInfo id ImportBound info
- | mayHaveCafRefs (idCafInfo id) = unitVarEnv id (id, TopLevelHasCafs, info)
+ | mayHaveCafRefs (idCafInfo id) = unitVarEnv id (id, ImportBound, info)
| otherwise = emptyVarEnv
-singletonFVInfo id (LetBound top_level _ _) info
- = unitVarEnv id (id, top_level, info)
-singletonFVInfo id other info
- = unitVarEnv id (id, NotTopLevelBound, info)
+singletonFVInfo id how_bound info = unitVarEnv id (id, how_bound, info)
tyvarFVInfo :: TyVarSet -> FreeVarsInfo
tyvarFVInfo tvs = foldVarSet add emptyFVInfo tvs
where
- add tv fvs = extendVarEnv fvs tv (tv, NotTopLevelBound, noBinderInfo)
+ add tv fvs = extendVarEnv fvs tv (tv, LambdaBound, noBinderInfo)
+ -- Type variables must be lambda-bound
unionFVInfo :: FreeVarsInfo -> FreeVarsInfo -> FreeVarsInfo
unionFVInfo fv1 fv2 = plusVarEnv_C plusFVInfo fv1 fv2
Nothing -> noBinderInfo
Just (_,_,info) -> info
-allFreeIds :: FreeVarsInfo -> [Id] -- Non-top-level things only
-allFreeIds fvs = [id | (id,_,_) <- rngVarEnv fvs, isId id]
+allFreeIds :: FreeVarsInfo -> [(Id,HowBound)] -- Both top level and non-top-level Ids
+allFreeIds fvs = [(id,how_bound) | (id,how_bound,_) <- rngVarEnv fvs, isId id]
--- Non-top-level things only, both type variables and ids (type variables
--- only if opt_RuntimeTypes.
+-- Non-top-level things only, both type variables and ids
+-- (type variables only if opt_RuntimeTypes)
getFVs :: FreeVarsInfo -> [Var]
-getFVs fvs = [id | (id,NotTopLevelBound,_) <- rngVarEnv fvs]
+getFVs fvs = [id | (id, how_bound, _) <- rngVarEnv fvs,
+ not (topLevelBound how_bound) ]
getFVSet :: FreeVarsInfo -> VarSet
getFVSet fvs = mkVarSet (getFVs fvs)
-plusFVInfo (id1,top1,info1) (id2,top2,info2)
- = ASSERT (id1 == id2 && top1 == top2)
- (id1, top1, combineStgBinderInfo info1 info2)
+plusFVInfo (id1,hb1,info1) (id2,hb2,info2)
+ = ASSERT (id1 == id2 && hb1 `check_eq_how_bound` hb2)
+ (id1, hb1, combineStgBinderInfo info1 info2)
+
+#ifdef DEBUG
+-- The HowBound info for a variable in the FVInfo should be consistent
+check_eq_how_bound ImportBound ImportBound = True
+check_eq_how_bound LambdaBound LambdaBound = True
+check_eq_how_bound (LetBound li1 ar1) (LetBound li2 ar2) = ar1 == ar2 && check_eq_li li1 li2
+check_eq_how_bound hb1 hb2 = False
+
+check_eq_li (NestedLet _) (NestedLet _) = True
+check_eq_li (TopLet _) (TopLet _) = True
+check_eq_li li1 li2 = False
+#endif
\end{code}
Misc.
cafRefs p (Var id)
= case lookupVarEnv p id of
- Just (LetBound TopLevelHasCafs _ _) -> fastBool True -- Top level
- Just (LetBound TopLevelNoCafs _ _) -> fastBool False -- Top level
- Nothing | isLocalId id -> fastBool False -- Nested binder
- | otherwise -> fastBool (mayHaveCafRefs (idCafInfo id)) -- Imported
- Just _other -> error ("cafRefs " ++ showSDoc (ppr id)) -- No nested things in env
-
+ Just (LetBound (TopLet caf_info) _) -> fastBool (mayHaveCafRefs caf_info)
+ Nothing | isGlobalId id -> fastBool (mayHaveCafRefs (idCafInfo id)) -- Imported
+ | otherwise -> fastBool False -- Nested binder
+ _other -> error ("cafRefs " ++ showSDoc (ppr id)) -- No nested things in env
cafRefs p (Lit l) = fastBool False
cafRefs p (App f a) = fastOr (cafRefs p f) (cafRefs p) a
cafRefs p (Lam x e) = cafRefs p e
cafRefs p (Let b e) = fastOr (cafRefss p (rhssOfBind b)) (cafRefs p) e
-cafRefs p (Case e bndr alts) = fastOr (cafRefs p e)
- (cafRefss p) (rhssOfAlts alts)
+cafRefs p (Case e bndr alts) = fastOr (cafRefs p e) (cafRefss p) (rhssOfAlts alts)
cafRefs p (Note n e) = cafRefs p e
cafRefs p (Type t) = fastBool False
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