Re: [GHC] #9583: Simplifier ticks exhausted while compiling Cabal HEAD

#9583: Simplifier ticks exhausted while compiling Cabal HEAD -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: bug | Status: new Priority: highest | Milestone: Component: Compiler | Version: 7.9 Resolution: | Keywords: Operating System: | Architecture: Unknown/Multiple Unknown/Multiple | Difficulty: Unknown Type of failure: Compile- | Blocked By: time crash | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by Simon Peyton Jones ): In [changeset:"5fa6e75960b3dddbc72c35eb3fc0f2759215dfbb/ghc"]: {{{ #!CommitTicketReference repository="ghc" revision="5fa6e75960b3dddbc72c35eb3fc0f2759215dfbb" Ensure that loop breakers are computed when glomming This patch fixes Trac #9583, a loop in the simplifier. I thought this was going to be very complicated but it turned out to be very simple! The occurrence analyser does something called "glomming" if the application of imported RULES means that something that didn't look recursive becomes recursive. See `Note [Glomming]` in `OccurAnal`. Under these circumstances we group all the top-level bindings into a single massive `Rec`. But, crucially, I failed to repeat the occurrence analysis on this glommed set of bindings. That means that we weren't establishing the right loop breakers (indeed there were no loop breakers whatsoever), and that led immediately to the loop. The only surprising this is that it didn't happen before. }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9583#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler