Re: [PATCH -v2] x86/hweight: Get rid of the special calling convention

[H. Peter Anvin]

On May 11, 2016 4:24:09 AM PDT, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>On Wed, May 11, 2016 at 07:15:19AM -0400, Brian Gerst wrote:
>
>> I think he meant the out of line version would be asm, so you could
>> control what registers were clobbered.
>
>Yeah, it might save a few cycles on the call, but given that most
>machines should have popcnt these days is it worth the hassle/cost of
>duplicating the lib/hweight.c magic in asm (and remember, twice, once
>for 32bit and once for 64bit) ?

I was thinking it isn't really very complex code even in assembly as it is super-regular; you can even crib the gcc-generated code if you wish.
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