#14208: Performance with O0 is much better than the default or with -O2, runghc performs the best -------------------------------------+------------------------------------- Reporter: harendra | Owner: osa1 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 mpickering): I noticed two things from a brief look. 1. `fmap` is not SATed. Which means the static `f` won't be eliminated. 2. A bad(?) loopbreaker is chosen in `Prelude.foldrM`, `yield` rather than `go`. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14208#comment:35 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler