On Fri, Sep 7, 2012 at 4:54 AM, Nicolas Trangez <nico...@incubaid.com> wrote: > On Thu, 2012-09-06 at 12:07 -0700, Johan Tibell wrote: >> Have a look at the popCount implementation for e.g. Int, which are >> written in C and called through the FFI: >> >> https://github.com/ghc/packages-ghc-prim/blob/master/cbits/popcnt.c > > Out of interest: isn't this compiled into the popCnt# primop (and popcnt > instruction on SSE4.2)?
It's the other way around the popCnt# primop is compiled into either calls to these C functions or into the popcnt instruction, if -msse4.2 is given. > I recently noticed Data.IntSet also contains a fairly basic "bitcount" > implementation [1]. Is this kept as-is for a reason, instead of using > popCount from Data.Bits? I don't think so, except that we want to support the last 3 released versions of GHC so we need to have a fallback if Data.Bits.popCount isn't defined. -- Johan _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
