#8456: Control flow optimisations duplicate blocks --------------------------------------------+------------------------------ Reporter: jstolarek | Owner: jstolarek Type: bug | Status: new Priority: highest | Milestone: 7.8.1 Component: Compiler | Version: 7.7 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime performance bug | Unknown/Multiple Test Case: | Difficulty: Unknown Blocking: 8275 | Blocked By: | Related Tickets: --------------------------------------------+------------------------------ Comment (by simonmar): `lookup` looks up in the domain, not the range. You would need to do something like `elem b' (mapElems shortcut_map)`. This is O(n). But I still think you don't need this test. You're keeping `backEdges` up to date, so there's no reason to believe that you have something "hidden" in the `shortcut_map` that would represent more predecessors, right? The `shortcut_map` is for replacing labels inside expressions after the pass is complete. It used to update calls, but as you point out, the pass now does this as it goes along. There are no extra invariants. The `shortcut_map` doesn't represent any extra edges in the graph. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8456#comment:14 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler