#11195: New pattern-match check can be non-performant -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: highest | Milestone: Component: Compiler | Version: 7.11 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- In my work in merging Phab:D808 (and originally pointed out by thomie), I ran into a peculiar bug: the new pattern-match check took gobs of memory (~10GB) to check !OptCoercion in the stage-2 compiler. My analysis got only as far as nailing the problem down to `pmTraverse`, which took 80% of the time, and got called roughly a gajillion times. To reproduce, simply compile !OptCoercion (with `-package ghc`) and you'll see your memory usage explode. So that you'll be able to build GHC until this is fixed, I've disable the pattern-match check in that file. There is a good chance that this is caused by an interaction between the pattern-match check and the type=kind code. I'm happy to probe further, but I'd want George's help. NB: This applies only after my patch is merged. Which should be today. For some value of today. Hopefully today's value of today. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11195 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler