#14208: Performance with -O2 is worse than with -O0 which is worse than runghc -------------------------------------+------------------------------------- Reporter: harendra | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by harendra): Earlier I thought the problem occurs with `-O2` but that is not the case, `-O2` is irrelevant. `-O2` gives the same performance as the default i.e. without any optimization flags. The difference is between `-O0` and the absence of it. Adding `-O0` improves performance drastically. I have updated the github repo and removed `-O2`. This is such an ironic case, `runghc` has the best performance, the next best is `-O0` and any optimization is the worst! Maybe we should just reverse the flags :-) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14208#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler