diff options
Diffstat (limited to 'compiler/GHC/Core/Opt/DmdAnal.hs')
| -rw-r--r-- | compiler/GHC/Core/Opt/DmdAnal.hs | 12 |
1 files changed, 7 insertions, 5 deletions
diff --git a/compiler/GHC/Core/Opt/DmdAnal.hs b/compiler/GHC/Core/Opt/DmdAnal.hs index 4869fb1fa9..ae8aab18a8 100644 --- a/compiler/GHC/Core/Opt/DmdAnal.hs +++ b/compiler/GHC/Core/Opt/DmdAnal.hs @@ -233,9 +233,10 @@ dmdAnal' env dmd (Case scrut case_bndr ty [(alt, bndrs, rhs)]) (rhs_ty, rhs') = dmdAnal env dmd rhs (alt_ty1, dmds) = findBndrsDmds env rhs_ty bndrs (alt_ty2, case_bndr_dmd) = findBndrDmd env False alt_ty1 case_bndr - -- Evaluation cardinality on the case binder is irrelevant and a no-op. - -- What matters is its nested sub-demand! - (_ :* case_bndr_sd) = case_bndr_dmd + -- The peelDmd below will lazify the relative sub-demands if the + -- case_bndr_dmd had lazy evaluation cardinality. + -- See Note [Absent sub-demand] in GHC.Types.Demand + case_bndr_sd = peelDmd case_bndr_dmd -- Compute demand on the scrutinee (bndrs', scrut_sd) | DataAlt _ <- alt @@ -388,9 +389,10 @@ dmdAnalSumAlt :: AnalEnv -> SubDemand -> Id -> Alt Var -> (DmdType, Alt Var) dmdAnalSumAlt env dmd case_bndr (con,bndrs,rhs) | (rhs_ty, rhs') <- dmdAnal env dmd rhs , (alt_ty, dmds) <- findBndrsDmds env rhs_ty bndrs - , let (_ :* case_bndr_sd) = findIdDemand alt_ty case_bndr + , let case_bndr_dmd = findIdDemand alt_ty case_bndr -- See Note [Demand on scrutinee of a product case] - id_dmds = addCaseBndrDmd case_bndr_sd dmds + -- See Note [Absent sub-demand] in GHC.Types.Demand + id_dmds = addCaseBndrDmd (peelDmd case_bndr_dmd) dmds = (alt_ty, (con, setBndrsDemandInfo bndrs id_dmds, rhs')) {- |