#14880: GHC panic: updateRole -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: goldfire Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.2.2 checker) | Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple crash or panic | Test Case: Blocked By: | Blocking: Related Tickets: #15076 | Differential Rev(s): Phab:D4769 Wiki Page: | -------------------------------------+------------------------------------- Comment (by tdammers): Drilling down some more, I found that the biggest performance sink is `tcPolyInfer`, in both the pre- and post-patch versions; in both cases, it is responsible for just over 50% of allocations, but in terms of runtime, it's 36% before the patch, but 45% after - so that alone would explain a 5% performance deviation. Further data points: - On the first run after making a fresh build, `withCleanupSession.cleanup` shows up prominently, but from the second run onwards, it scores 0 on all metrics. - Overall performance for profile builds is such that the patch does actually produce a performance improvement, from approx. 1.25 seconds down to 1.07. - The patch does not touch `tcPolyInfer` at all, the entire module is identical between both versions - The performance counters suggests that code paths taken inside `tcPolyInfer` are the same -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14880#comment:40 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler