import Type ( TvSubstEnv, isUnLiftedType, seqType, tyConAppArgs, funArgTy,
splitFunTy_maybe, splitFunTy, coreEqType
)
-import VarEnv ( elemVarEnv )
+import VarEnv ( elemVarEnv, emptyVarEnv )
import TysPrim ( realWorldStatePrimTy )
import PrelInfo ( realWorldPrimId )
import BasicTypes ( TopLevelFlag(..), isTopLevel,
RecFlag(..), isNonRec
)
+import StaticFlags ( opt_PprStyle_Debug )
import OrdList
import Maybes ( orElse )
import Outputable
-> SimplM [OutAlt] -- Includes the continuation
simplAlts env handled_cons case_bndr' alts cont'
- = mapSmpl simpl_alt alts
+ = do { mb_alts <- mapSmpl simpl_alt alts
+ ; return [alt' | Just (_, alt') <- mb_alts] }
+ -- Filter out the alternatives that are inaccessible
where
- simpl_alt alt = simplAlt env handled_cons case_bndr' alt cont' `thenSmpl` \ (_, alt') ->
- returnSmpl alt'
+ simpl_alt alt = simplAlt env handled_cons case_bndr' alt cont'
simplAlt :: SimplEnv -> [AltCon] -> OutId -> InAlt -> SimplCont
- -> SimplM (Maybe TvSubstEnv, OutAlt)
+ -> SimplM (Maybe (TvSubstEnv, OutAlt))
-- Simplify an alternative, returning the type refinement for the
-- alternative, if the alternative does any refinement at all
+-- Nothing => the alternative is inaccessible
simplAlt env handled_cons case_bndr' (DEFAULT, bndrs, rhs) cont'
= ASSERT( null bndrs )
simplExprC env' rhs cont' `thenSmpl` \ rhs' ->
- returnSmpl (Nothing, (DEFAULT, [], rhs'))
+ returnSmpl (Just (emptyVarEnv, (DEFAULT, [], rhs')))
where
env' = mk_rhs_env env case_bndr' (mkOtherCon handled_cons)
-- Record the constructors that the case-binder *can't* be.
simplAlt env handled_cons case_bndr' (LitAlt lit, bndrs, rhs) cont'
= ASSERT( null bndrs )
simplExprC env' rhs cont' `thenSmpl` \ rhs' ->
- returnSmpl (Nothing, (LitAlt lit, [], rhs'))
+ returnSmpl (Just (emptyVarEnv, (LitAlt lit, [], rhs')))
where
env' = mk_rhs_env env case_bndr' (mkUnfolding False (Lit lit))
env' = mk_rhs_env env case_bndr' unf
in
simplExprC env' rhs cont' `thenSmpl` \ rhs' ->
- returnSmpl (Nothing, (DataAlt con, vs', rhs'))
+ returnSmpl (Just (emptyVarEnv, (DataAlt con, vs', rhs')))
| otherwise -- GADT case
= let
in
simplBinders env tvs `thenSmpl` \ (env1, tvs') ->
case coreRefineTys (getInScope env1) con tvs' (idType case_bndr') of {
- Nothing -- Dead code; for now, I'm just going to put in an
- -- error case so I can see them
+ Nothing -- Inaccessible
+ | opt_PprStyle_Debug -- Hack: if debugging is on, generate an error case
+ -- so we can see it
-> let rhs' = mkApps (Var eRROR_ID)
[Type (substTy env (exprType rhs)),
Lit (mkStringLit "Impossible alternative (GADT)")]
in
simplBinders env1 ids `thenSmpl` \ (env2, ids') ->
- returnSmpl (Nothing, (DataAlt con, tvs' ++ ids', rhs')) ;
+ returnSmpl (Just (emptyVarEnv, (DataAlt con, tvs' ++ ids', rhs')))
+
+ | otherwise -- Filter out the inaccessible branch
+ -> return Nothing ;
Just refine@(tv_subst_env, _) -> -- The normal case
vs' = tvs' ++ ids'
in
simplExprC env_w_unf rhs cont' `thenSmpl` \ rhs' ->
- returnSmpl (Just tv_subst_env, (DataAlt con, vs', rhs')) }
+ returnSmpl (Just (tv_subst_env, (DataAlt con, vs', rhs'))) }
where
-- add_evals records the evaluated-ness of the bound variables of
-- This has been this way for a long time, so I'll leave it,
-- but I can't convince myself that it's right.
--- gaw 2004
mkDupableCont env (Select _ case_bndr alts se cont)
= -- e.g. (case [...hole...] of { pi -> ei })
-- ===>
where
go env [] = returnSmpl (emptyFloats env, [])
go env (alt:alts)
- = mkDupableAlt env case_bndr' dupable_cont alt `thenSmpl` \ (floats1, alt') ->
- addFloats env floats1 $ \ env ->
- go env alts `thenSmpl` \ (floats2, alts') ->
- returnSmpl (floats2, alt' : alts')
+ = do { (floats1, mb_alt') <- mkDupableAlt env case_bndr' dupable_cont alt
+ ; addFloats env floats1 $ \ env -> do
+ { (floats2, alts') <- go env alts
+ ; returnSmpl (floats2, case mb_alt' of
+ Just alt' -> alt' : alts'
+ Nothing -> alts'
+ )}}
mkDupableAlt env case_bndr' cont alt
- = simplAlt env [] case_bndr' alt cont `thenSmpl` \ (mb_reft, (con, bndrs', rhs')) ->
+ = simplAlt env [] case_bndr' alt cont `thenSmpl` \ mb_stuff ->
+ case mb_stuff of {
+ Nothing -> returnSmpl (emptyFloats env, Nothing) ;
+
+ Just (reft, (con, bndrs', rhs')) ->
-- Safe to say that there are no handled-cons for the DEFAULT case
if exprIsDupable rhs' then
- returnSmpl (emptyFloats env, (con, bndrs', rhs'))
+ returnSmpl (emptyFloats env, Just (con, bndrs', rhs'))
-- It is worth checking for a small RHS because otherwise we
-- get extra let bindings that may cause an extra iteration of the simplifier to
-- inline back in place. Quite often the rhs is just a variable or constructor.
rhs_ty' = exprType rhs'
used_bndrs' = filter abstract_over (case_bndr' : bndrs')
abstract_over bndr
- | isTyVar bndr = not (mb_reft `refines` bndr)
+ | isTyVar bndr = not (bndr `elemVarEnv` reft)
-- Don't abstract over tyvar binders which are refined away
+ -- See Note [Refinement] below
| otherwise = not (isDeadBinder bndr)
-- The deadness info on the new Ids is preserved by simplBinders
- refines Nothing bndr = False
- refines (Just tv_subst) bndr = bndr `elemVarEnv` tv_subst
- -- See Note [Refinement] below
in
-- If we try to lift a primitive-typed something out
-- for let-binding-purposes, we will *caseify* it (!),
join_rhs = mkLams really_final_bndrs rhs'
join_call = mkApps (Var join_bndr) final_args
in
- returnSmpl (unitFloat env join_bndr join_rhs, (con, bndrs', join_call))
+ returnSmpl (unitFloat env join_bndr join_rhs, Just (con, bndrs', join_call)) }
\end{code}
Note [Refinement]
projects / ghc-hetmet.git / commitdiff