[Haskell-cafe] performance issues with popCount

[Nicolas Trangez]

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)?

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?

Nicolas

[1]
https://github.com/ghc/packages-containers/blob/master/Data/IntSet/Base.hs#L1459