Simon Peyton Jones pushed to branch wip/T26425 at Glasgow Haskell Compiler / GHC Commits: 0675a96c by Simon Peyton Jones at 2025-10-27T15:22:49+00:00 Fix buglet that led to non-termination! - - - - - 2 changed files: - compiler/GHC/Core/Opt/Simplify/Iteration.hs - compiler/GHC/Core/Unfold/Make.hs Changes: ===================================== compiler/GHC/Core/Opt/Simplify/Iteration.hs ===================================== @@ -4598,13 +4598,21 @@ mkLetUnfolding :: SimplEnv -> TopLevelFlag -> UnfoldingSource -> InId -> Bool -- True <=> this is a join point -> OutExpr -> SimplM Unfolding mkLetUnfolding env top_lvl src id is_join new_rhs - = return (mkUnfolding uf_opts src is_top_lvl is_bottoming is_join new_rhs Nothing) - -- We make an unfolding *even for loop-breakers*. - -- Reason: (a) It might be useful to know that they are WHNF - -- (b) In GHC.Iface.Tidy we currently assume that, if we want to - -- expose the unfolding then indeed we *have* an unfolding - -- to expose. (We could instead use the RHS, but currently - -- we don't.) The simple thing is always to have one. + | is_join + , UnfNever <- guidance + = -- For large join points, don't keep an unfolding at all if it is large + -- This is just an attempt to keep residency under control in + -- deeply-nested join-point such as those arising in #26425 + return NoUnfolding + + | otherwise + = return (mkCoreUnfolding src is_top_lvl new_rhs Nothing guidance) + -- We make an unfolding *even for loop-breakers*. + -- Reason: (a) It might be useful to know that they are WHNF + -- (b) In GHC.Iface.Tidy we currently assume that, if we want to + -- expose the unfolding then indeed we *have* an unfolding + -- to expose. (We could instead use the RHS, but currently + -- we don't.) The simple thing is always to have one. where -- !opts: otherwise, we end up retaining all the SimpleEnv !uf_opts = seUnfoldingOpts env @@ -4615,6 +4623,9 @@ mkLetUnfolding env top_lvl src id is_join new_rhs -- See Note [Force bottoming field] !is_bottoming = isDeadEndId id + is_top_bottoming = is_top_lvl && is_bottoming + guidance = calcUnfoldingGuidance uf_opts is_top_bottoming is_join new_rhs + ------------------- simplStableUnfolding :: SimplEnv -> BindContext -> InId ===================================== compiler/GHC/Core/Unfold/Make.hs ===================================== @@ -354,14 +354,6 @@ mkCoreUnfolding :: UnfoldingSource -> Bool -> CoreExpr -> Maybe UnfoldingCache -> UnfoldingGuidance -> Unfolding -- Occurrence-analyses the expression before capturing it mkCoreUnfolding src top_lvl expr precomputed_cache guidance - | UnfNever <- guidance - , not top_lvl - = -- For large, non-top-level bindings, don't keep an unfolding at all if it is large - -- Keep top-level ones in case of -fexpose-all-unfoldings - -- Just an attempt to keep residency under control in deeply-nested let bindings - NoUnfolding - - | otherwise = CoreUnfolding { uf_tmpl = cache `seq` occurAnalyseExpr expr -- occAnalyseExpr: see Note [OccInfo in unfoldings and rules] in GHC.Core View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/0675a96cd150475fb8f0a6ac303cfe16... -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/0675a96cd150475fb8f0a6ac303cfe16... You're receiving this email because of your account on gitlab.haskell.org.