#5615: ghc produces poor code for `div` with constant powers of 2. -------------------------------------+------------------------------------- Reporter: Lennart | Owner: akio Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.4.1-rc1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: x86 Type of failure: Runtime | Test Case: performance bug | Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D2486 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ben Gamari ): In [changeset:"6ea62427de419ea071e1ea79ad0c15d9f4e90a67/ghc" 6ea6242/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="6ea62427de419ea071e1ea79ad0c15d9f4e90a67" Turn divInt# and modInt# into bitwise operations when possible This implements #5615 for divInt# and modInt#. I also included rules to do constant-folding when the both arguments are known. Test Plan: validate Reviewers: austin, simonmar, bgamari Reviewed By: bgamari Subscribers: hvr, thomie Differential Revision: https://phabricator.haskell.org/D2486 GHC Trac Issues: #5615 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/5615#comment:31 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler