#10720: New GHC fails to specialize imported function -------------------------------------+------------------------------------- Reporter: wyager | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Keywords: | Operating System: MacOS X performance, inline, specialize | Architecture: x86_64 | Type of failure: Runtime (amd64) | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- I just installed the new Haskell platform for OS X. It seems to have caused a major performance regression for a program I'm working on, making it well over 25x slower. The culprit appears to be that the new GHC (7.10.2) fails to specialize an imported function. If I manually add a SPECIALIZE pragma, performance goes back to around what it used to be. The code in question is located at https://github.com/wyager/HNet . As it stands, the code takes about 30 seconds to run on my machine. With the previous haskell-platform, it only took about .9 seconds. If I modify Operations.hs and uncomment the SPECIALIZE pragma, runtime goes down to about 1.1 seconds (still slower for some reason, but not awful). To test, compile with -O2 (as the program makes heavy use of Data.Vector, which requires -fspec-constr for performance). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10720 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler