On Thu, Jan 15, 2026 at 11:42:14AM +0200, Heikki Linnakangas wrote: > On 15/01/2026 11:07, John Naylor wrote: >> s/slow/generic/: >> >> I'm ambivalent about this. The "slow" designation is flat-out wrong >> since at least Power and aarch64 can emit a single instruction here >> without prodding the compiler. On the other hand, "generic" seems >> wrong too, since e.g. pg_popcount64_slow() has three configure symbols >> and two compiler builtins. :-D > > "fallback", or "portable" ?
I've no strong opinions, but "portable" seems reasonable to me. > Yeah, I noticed that on x86_64, pg_popcount_optimized is always a function > pointer with runtime check, even if you use compiler flags to target a CPU > where the special instructions are available unconditionally. I wonder how close we are to being able to just require SSE4.2/POPCNT for x86-64 builds. I suppose there's always a chance that someone will try to run Postgres 19 on a CPU from the aughts... In any case, avoiding the function pointer when possible seems like a good follow-up. -- nathan
