#3034: divInt# floated into a position which leads to low arity --------------------------------------------+------------------------------ Reporter: batterseapower | Owner: Type: bug | Status: patch Priority: lowest | Milestone: 7.6.2 Component: Compiler | Version: 6.10.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime performance bug | Unknown/Multiple Test Case: | Difficulty: Unknown Blocking: | Blocked By: | Related Tickets: --------------------------------------------+------------------------------ Changes (by nomeata): * status: new => patch Comment: Changing `primOpIsCheap` to always True validates, and has no allocation change in nofib. I guess I should be measuring runtime numbers, but for that I’ll need the machine to be unloaded, maybe later today.... Alright, numbers are in: {{{ Min -0.0% -0.0% -7.1% -6.5% -1.8% Max +0.0% +0.0% +2.1% +1.5% +19.8% Geometric Mean -0.0% -0.0% -0.6% -0.5% +0.2% }}} so it seems to be worth it. Not pushing quite yet: Assuming we make the cheapness configurable in `primops.txt.pp`, what primops should not be cheap? To me all of them look cheap (e.g. arithmetic) or are side-effecting (like `copyArray#`, in which case the `primOpIsCheap` information hopefully has no effect. So it seems to me that we do not need to a flag in `primops.txt.pp` just yet; maybe something will show up later. (Marking as for review without a patch because the patch is trivial; it is this question that need to be reviewed.) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/3034#comment:14 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler