import SimplUtils
import FamInstEnv ( FamInstEnv )
import Id
-import MkId ( mkImpossibleExpr, seqId )
+import MkId ( seqId, realWorldPrimId )
+import MkCore ( mkImpossibleExpr )
import Var
import IdInfo
import Name ( mkSystemVarName, isExternalName )
import BasicTypes ( isMarkedStrict, Arity )
import CostCentre ( currentCCS, pushCCisNop )
import TysPrim ( realWorldStatePrimTy )
-import PrelInfo ( realWorldPrimId )
import BasicTypes ( TopLevelFlag(..), isTopLevel, RecFlag(..) )
import MonadUtils ( foldlM, mapAccumLM )
import Maybes ( orElse )
-- Simplify the RHS
; (body_env1, body1) <- simplExprF body_env body mkRhsStop
-- ANF-ise a constructor or PAP rhs
- ; (body_env2, body2) <- prepareRhs body_env1 bndr1 body1
+ ; (body_env2, body2) <- prepareRhs top_lvl body_env1 bndr1 body1
; (env', rhs')
<- if not (doFloatFromRhs top_lvl is_rec False body2 body_env2)
- then -- No floating, just wrap up!
- do { rhs' <- mkLam env tvs' (wrapFloats body_env2 body2)
+ then -- No floating, revert to body1
+ do { rhs' <- mkLam env tvs' (wrapFloats body_env1 body1)
; return (env, rhs') }
else if null tvs then -- Simple floating
= return env -- Here b is dead, and we avoid creating
| otherwise -- the binding b = (a,b)
= do { (env', bndr') <- simplBinder env bndr
- ; completeNonRecX env' (isStrictId bndr) bndr bndr' new_rhs }
+ ; completeNonRecX NotTopLevel env' (isStrictId bndr) bndr bndr' new_rhs }
+ -- simplNonRecX is only used for NotTopLevel things
-completeNonRecX :: SimplEnv
+completeNonRecX :: TopLevelFlag -> SimplEnv
-> Bool
-> InId -- Old binder
-> OutId -- New binder
-> OutExpr -- Simplified RHS
-> SimplM SimplEnv
-completeNonRecX env is_strict old_bndr new_bndr new_rhs
- = do { (env1, rhs1) <- prepareRhs (zapFloats env) new_bndr new_rhs
+completeNonRecX top_lvl env is_strict old_bndr new_bndr new_rhs
+ = do { (env1, rhs1) <- prepareRhs top_lvl (zapFloats env) new_bndr new_rhs
; (env2, rhs2) <-
if doFloatFromRhs NotTopLevel NonRecursive is_strict rhs1 env1
then do { tick LetFloatFromLet
That's what the 'go' loop in prepareRhs does
\begin{code}
-prepareRhs :: SimplEnv -> OutId -> OutExpr -> SimplM (SimplEnv, OutExpr)
+prepareRhs :: TopLevelFlag -> SimplEnv -> OutId -> OutExpr -> SimplM (SimplEnv, OutExpr)
-- Adds new floats to the env iff that allows us to return a good RHS
-prepareRhs env id (Cast rhs co) -- Note [Float coercions]
+prepareRhs top_lvl env id (Cast rhs co) -- Note [Float coercions]
| (ty1, _ty2) <- coercionKind co -- Do *not* do this if rhs has an unlifted type
, not (isUnLiftedType ty1) -- see Note [Float coercions (unlifted)]
- = do { (env', rhs') <- makeTrivialWithInfo env sanitised_info rhs
+ = do { (env', rhs') <- makeTrivialWithInfo top_lvl env sanitised_info rhs
; return (env', Cast rhs' co) }
where
sanitised_info = vanillaIdInfo `setStrictnessInfo` strictnessInfo info
`setDemandInfo` demandInfo info
info = idInfo id
-prepareRhs env0 _ rhs0
+prepareRhs top_lvl env0 _ rhs0
= do { (_is_exp, env1, rhs1) <- go 0 env0 rhs0
; return (env1, rhs1) }
where
go n_val_args env (App fun arg)
= do { (is_exp, env', fun') <- go (n_val_args+1) env fun
; case is_exp of
- True -> do { (env'', arg') <- makeTrivial env' arg
+ True -> do { (env'', arg') <- makeTrivial top_lvl env' arg
; return (True, env'', App fun' arg') }
False -> return (False, env, App fun arg) }
go n_val_args env (Var fun)
\begin{code}
-makeTrivial :: SimplEnv -> OutExpr -> SimplM (SimplEnv, OutExpr)
+makeTrivial :: TopLevelFlag -> SimplEnv -> OutExpr -> SimplM (SimplEnv, OutExpr)
-- Binds the expression to a variable, if it's not trivial, returning the variable
-makeTrivial env expr = makeTrivialWithInfo env vanillaIdInfo expr
+makeTrivial top_lvl env expr = makeTrivialWithInfo top_lvl env vanillaIdInfo expr
-makeTrivialWithInfo :: SimplEnv -> IdInfo -> OutExpr -> SimplM (SimplEnv, OutExpr)
+makeTrivialWithInfo :: TopLevelFlag -> SimplEnv -> IdInfo
+ -> OutExpr -> SimplM (SimplEnv, OutExpr)
-- Propagate strictness and demand info to the new binder
-- Note [Preserve strictness when floating coercions]
-- Returned SimplEnv has same substitution as incoming one
-makeTrivialWithInfo env info expr
- | exprIsTrivial expr
+makeTrivialWithInfo top_lvl env info expr
+ | exprIsTrivial expr -- Already trivial
+ || not (bindingOk top_lvl expr expr_ty) -- Cannot trivialise
+ -- See Note [Cannot trivialise]
= return (env, expr)
| otherwise -- See Note [Take care] below
= do { uniq <- getUniqueM
; let name = mkSystemVarName uniq (fsLit "a")
- var = mkLocalIdWithInfo name (exprType expr) info
- ; env' <- completeNonRecX env False var var expr
+ var = mkLocalIdWithInfo name expr_ty info
+ ; env' <- completeNonRecX top_lvl env False var var expr
; expr' <- simplVar env' var
; return (env', expr') }
-- The simplVar is needed becase we're constructing a new binding
-- is what completeNonRecX will do
-- To put it another way, it's as if we'd simplified
-- let var = e in var
+ where
+ expr_ty = exprType expr
+
+bindingOk :: TopLevelFlag -> CoreExpr -> Type -> Bool
+-- True iff we can have a binding of this expression at this level
+-- Precondition: the type is the type of the expression
+bindingOk top_lvl _ expr_ty
+ | isTopLevel top_lvl = not (isUnLiftedType expr_ty)
+ | otherwise = True
\end{code}
+Note [Cannot trivialise]
+~~~~~~~~~~~~~~~~~~~~~~~~
+Consider tih
+ f :: Int -> Addr#
+
+ foo :: Bar
+ foo = Bar (f 3)
+
+Then we can't ANF-ise foo, even though we'd like to, because
+we can't make a top-level binding for the Addr# (f 3). And if
+so we don't want to turn it into
+ foo = let x = f 3 in Bar x
+because we'll just end up inlining x back, and that makes the
+simplifier loop. Better not to ANF-ise it at all.
+
+A case in point is literal strings (a MachStr is not regarded as
+trivial):
+
+ foo = Ptr "blob"#
+
+We don't want to ANF-ise this.
%************************************************************************
%* *
-> OccInfo -> OutExpr
-> Unfolding -> SimplM Unfolding
-- Note [Setting the new unfolding]
-simplUnfolding env _ _ _ _ (DFunUnfolding con ops)
- = return (DFunUnfolding con ops')
+simplUnfolding env _ _ _ _ (DFunUnfolding ar con ops)
+ = return (DFunUnfolding ar con ops')
where
ops' = map (substExpr (text "simplUnfolding") env) ops
n_params = length bndrs
(bndrs, body) = collectBinders expr
zap | n_args >= n_params = \b -> b
- | otherwise = \b -> if isTyVar b then b
+ | otherwise = \b -> if isTyCoVar b then b
else zapLamIdInfo b
-- NB: we count all the args incl type args
-- so we must count all the binders (incl type lambdas)
-- First deal with type applications and type lets
-- (/\a. e) (Type ty) and (let a = Type ty in e)
simplNonRecE env bndr (Type ty_arg, rhs_se) (bndrs, body) cont
- = ASSERT( isTyVar bndr )
+ = ASSERT( isTyCoVar bndr )
do { ty_arg' <- simplType (rhs_se `setInScope` env) ty_arg
; simplLam (extendTvSubst env bndr ty_arg') bndrs body cont }
(StrictBind bndr bndrs body env cont) }
| otherwise
- = ASSERT( not (isTyVar bndr) )
+ = ASSERT( not (isTyCoVar bndr) )
do { (env1, bndr1) <- simplNonRecBndr env bndr
; let (env2, bndr2) = addBndrRules env1 bndr bndr1
; env3 <- simplLazyBind env2 NotTopLevel NonRecursive bndr bndr2 rhs rhs_se
simplVar :: SimplEnv -> InVar -> SimplM OutExpr
-- Look up an InVar in the environment
simplVar env var
- | isTyVar var
+ | isTyCoVar var
= return (Type (substTyVar env var))
| otherwise
= case substId env var of
= go vs the_strs
where
go [] [] = []
- go (v:vs') strs | isTyVar v = v : go vs' strs
+ go (v:vs') strs | isTyCoVar v = v : go vs' strs
go (v:vs') (str:strs)
| isMarkedStrict str = evald_v : go vs' strs
| otherwise = zapped_v : go vs' strs
bind_args env' [] _ = return env'
bind_args env' (b:bs') (Type ty : args)
- = ASSERT( isTyVar b )
+ = ASSERT( isTyCoVar b )
bind_args (extendTvSubst env' b ty) bs' args
bind_args env' (b:bs') (arg : args)
mkDupableCont env (StrictArg info cci cont)
-- See Note [Duplicating StrictArg]
= do { (env', dup, nodup) <- mkDupableCont env cont
- ; (env'', args') <- mapAccumLM makeTrivial env' (ai_args info)
+ ; (env'', args') <- mapAccumLM (makeTrivial NotTopLevel) env' (ai_args info)
; return (env'', StrictArg (info { ai_args = args' }) cci dup, nodup) }
mkDupableCont env (ApplyTo _ arg se cont)
-- in [...hole...] a
do { (env', dup_cont, nodup_cont) <- mkDupableCont env cont
; arg' <- simplExpr (se `setInScope` env') arg
- ; (env'', arg'') <- makeTrivial env' arg'
+ ; (env'', arg'') <- makeTrivial NotTopLevel env' arg'
; let app_cont = ApplyTo OkToDup arg'' (zapSubstEnv env'') dup_cont
; return (env'', app_cont, nodup_cont) }
DataAlt dc -> setIdUnfolding case_bndr unf
where
-- See Note [Case binders and join points]
- unf = mkInlineRule needSaturated rhs 0
+ unf = mkInlineRule rhs Nothing
rhs = mkConApp dc (map Type (tyConAppArgs scrut_ty)
++ varsToCoreExprs bndrs')
| otherwise = bndrs' ++ [case_bndr_w_unf]
abstract_over bndr
- | isTyVar bndr = True -- Abstract over all type variables just in case
+ | isTyCoVar bndr = True -- Abstract over all type variables just in case
| otherwise = not (isDeadBinder bndr)
-- The deadness info on the new Ids is preserved by simplBinders
but that is bad if 'c' is *not* later scrutinised.
So instead we do both: we pass 'c' and 'c#' , and record in c's inlining
-that it's really I# c#, thus
+(an InlineRule) that it's really I# c#, thus
$j = \c# -> \c[=I# c#] -> ...c....
Absence analysis may later discard 'c'.
+NB: take great care when doing strictness analysis;
+ see Note [Lamba-bound unfoldings] in DmdAnal.
+
+Also note that we can still end up passing stuff that isn't used. Before
+strictness analysis we have
+ let $j x y c{=(x,y)} = (h c, ...)
+ in ...
+After strictness analysis we see that h is strict, we end up with
+ let $j x y c{=(x,y)} = ($wh x y, ...)
+and c is unused.
Note [Duplicated env]
~~~~~~~~~~~~~~~~~~~~~
projects / ghc-hetmet.git / blobdiff