#9246: GHC generates poor code for repeated uses of min/max --------------------------------------------+------------------------------ Reporter: arotenberg | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Resolution: | Keywords: Operating System: Windows | Architecture: x86_64 Type of failure: Runtime performance bug | (amd64) Test Case: | Difficulty: Unknown Blocking: | Blocked By: | Related Tickets: #6135 --------------------------------------------+------------------------------ Comment (by arotenberg): You should be able to reproduce the issue by using the versions and flags I listed in the original description with a fresh GHC 7.8.2 install. I'm in no rush to get this fixed since the program I'm working on is just a hobby project. I just ran into the issue and figured I'd report it. I mentioned "min/max-like functions" in my previous comment because it's easy to contrive other functions that cause similar issues. Try compiling this module with `ghc -O -ddump-simpl -ddump-to-file UglyBranching.hs` and look at the Core file it generates. {{{ module UglyBranching where foo :: Int -> Int -> Int -> Int -> Int foo a b c d = (((a `bar` b) `bar` (c `bar` d)) `bar` ((a `bar` c) `bar` (b `bar` d))) `bar` (((b `bar` a) `bar` (d `bar` c)) `bar` ((c `bar` a) `bar` (d `bar` b))) bar :: Int -> Int -> Int bar m n = if m + n > 5 then m else n }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9246#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler