import CoreFVs -- all of it
import CoreSubst ( Subst, emptySubst, extendInScope, extendIdSubst,
cloneIdBndr, cloneRecIdBndrs )
-import Id ( Id, idType, mkSysLocal, isOneShotLambda,
+import Id ( idType, mkSysLocal, isOneShotLambda,
zapDemandIdInfo, transferPolyIdInfo,
idSpecialisation, idWorkerInfo, setIdInfo
)
@lvlMFE@ is just like @lvlExpr@, except that it might let-bind
the expression, so that it can itself be floated.
-[NOTE: unlifted MFEs]
+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 [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 -- True <=> strict context [body of case or let]
-> Level -- Level of innermost enclosing lambda/tylam
lvlMFE _ _ _ (_, AnnType ty)
= return (Type ty)
+-- No point in floating out an expression wrapped in a coercion;
+-- If we do we'll transform lvl = e |> co
+-- to lvl' = e; lvl = lvl' |> co
+-- and then inline lvl. Better just to float out the payload.
+lvlMFE strict_ctxt ctxt_lvl env (_, AnnCast e co)
+ = do { expr' <- lvlMFE strict_ctxt ctxt_lvl env e
+ ; return (Cast expr' co) }
+
+-- Note [Case MFEs]
+lvlMFE True ctxt_lvl env e@(_, AnnCase {})
+ = lvlExpr ctxt_lvl env e -- Don't share cases
lvlMFE strict_ctxt ctxt_lvl env ann_expr@(fvs, _)
- | isUnLiftedType ty -- Can't let-bind it; see [NOTE: unlifted MFEs]
+ | isUnLiftedType ty -- Can't let-bind it; see Note [Unlifted MFEs]
|| isInlineCtxt ctxt_lvl -- Don't float out of an __inline__ context
|| exprIsTrivial expr -- Never float if it's trivial
|| not good_destination
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 isIdVar abs_vars > 1
+ | isSingleton pairs && count isId abs_vars > 1
= do -- Special case for self recursion where there are
-- several variables carried around: build a local loop:
-- poly_f = \abs_vars. \lam_vars . letrec f = \lam_vars. rhs in f lam_vars
[] bndrs
where
go old_lvl bumped_major rev_lvld_bndrs (bndr:bndrs)
- | isIdVar bndr && -- Go to the next major level if this is a value binder,
+ | isId bndr && -- Go to the next major level if this is a value binder,
not bumped_major && -- and we havn't already gone to the next level (one jump per group)
not (isOneShotLambda bndr) -- and it isn't a one-shot lambda
= go new_lvl True (TB bndr new_lvl : rev_lvld_bndrs) bndrs
-- We may only want to do this if there are sufficiently few free
-- variables. We certainly only want to do it for values, and not for
-- constructors. So the simple thing is just to look for lambdas
-isFunction (_, AnnLam b e) | isIdVar b = True
+isFunction (_, AnnLam b e) | isId b = True
| otherwise = isFunction e
isFunction (_, AnnNote _ e) = isFunction e
isFunction _ = False
initialEnv float_lams = (float_lams, emptyVarEnv, emptySubst, emptyVarEnv)
floatLams :: LevelEnv -> Bool
-floatLams (FloatOutSw float_lams _, _, _, _) = float_lams
+floatLams (fos, _, _, _) = floatOutLambdas fos
floatConsts :: LevelEnv -> Bool
-floatConsts (FloatOutSw _ float_consts, _, _, _) = float_consts
+floatConsts (fos, _, _, _) = floatOutConstants fos
extendLvlEnv :: LevelEnv -> [TaggedBndr Level] -> LevelEnv
-- Used when *not* cloning
Nothing -> [in_var])
max_out out_var lvl
- | isIdVar out_var = case lookupVarEnv lvl_env out_var of
+ | isId out_var = case lookupVarEnv lvl_env out_var of
Just lvl' -> maxLvl lvl' lvl
Nothing -> lvl
- | otherwise = lvl -- Ignore tyvars in *maxIdLevel*
+ | otherwise = lvl -- Ignore tyvars in *maxIdLevel*
lookupVar :: LevelEnv -> Id -> LevelledExpr
lookupVar (_, _, _, id_env) v = case lookupVarEnv id_env v of
-- We are going to lambda-abstract, so nuke any IdInfo,
-- and add the tyvars of the Id (if necessary)
- zap v | isIdVar v = WARN( workerExists (idWorkerInfo v) ||
+ zap v | isId v = WARN( workerExists (idWorkerInfo v) ||
not (isEmptySpecInfo (idSpecialisation v)),
text "absVarsOf: discarding info on" <+> ppr v )
setIdInfo v vanillaIdInfo
-- we must look in x's type
-- And similarly if x is a coercion variable.
absVarsOf id_env v
- | isIdVar v = [av2 | av1 <- lookup_avs v
+ | isId v = [av2 | av1 <- lookup_avs v
, av2 <- add_tyvars av1]
| isCoVar v = add_tyvars v
| otherwise = [v]
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 $ -- Note [transferPolyIdInfo] in Id.lhs
+ mk_poly_bndr bndr uniq = transferPolyIdInfo bndr abs_vars $ -- Note [transferPolyIdInfo] in Id.lhs
mkSysLocal (mkFastString str) uniq poly_ty
where
str = "poly_" ++ occNameString (getOccName bndr)
cloneVar TopLevel env v _ _
= return (env, v) -- Don't clone top level things
cloneVar NotTopLevel env@(_,_,subst,_) v ctxt_lvl dest_lvl
- = ASSERT( isIdVar v ) do
+ = ASSERT( isId v ) do
us <- getUniqueSupplyM
let
(subst', v1) = cloneIdBndr subst us v
cloneRecVars TopLevel env vs _ _
= return (env, vs) -- Don't clone top level things
cloneRecVars NotTopLevel env@(_,_,subst,_) vs ctxt_lvl dest_lvl
- = ASSERT( all isIdVar vs ) do
+ = ASSERT( all isId vs ) do
us <- getUniqueSupplyM
let
(subst', vs1) = cloneRecIdBndrs subst us vs
projects / ghc-hetmet.git / blobdiff