Re: refactor architecture-specific popcount code

On Feb 3 2026, at 12:41 pm, Nathan Bossart <nathandbossart(at)gmail(dot)com> wrote:

> On Tue, Feb 03, 2026 at 12:19:48PM -0500, Greg Burd wrote:
>> Thanks for the focus on this area of the code. I've been looking into
>> what to do with popcnt when building Win11/ARM64/MSVC. I know that when
>> _MSC_VER and _M_ARM64 are defined we can make use of the
>> __popcnt(unsigned int) and __popcnt64(unsigned __int64) intrinsics which
>> have been available since VS 2022 17.11+. I thought I'd check that combo
>> out and it turns out that it is identical to clang/gcc on that platform
>> [0].
>>
>> I'll wait for your work to land before proposing a patch to add these
>> unless it is really easy to fit it and you feel like giving it a go. :)
>
> We should probably just add something like
>
> #ifdef _MSC_VER
> return __popcnt(word);

Right, it seemed to me after reviewing the patch to fit right in.

> for the new inlined versions of pg_popcount{32,64}. We're already doing
> that today for x86-64, and the AArch64-specific versions use intrinsics
> that in theory compile to the same thing. Plus, popcnt is required for
> Windows these days.
>
> I'm working on polishing/benchmarking these patches at the moment, so I
> will work this change in. Thanks!

Not a problem, thank you!

> --
> nathan

-greg