On Tue, 19 Mar 2024 at 10:08, Nathan Bossart <nathandboss...@gmail.com> wrote: > > On Tue, Mar 19, 2024 at 10:02:18AM +1300, David Rowley wrote: > > The only thing I'd question in the patch is in pg_popcount_fast(). It > > looks like you've opted to not do the 32-bit processing on 32-bit > > machines. I think that's likely still worth coding in a similar way to > > how pg_popcount_slow() works. i.e. use "#if SIZEOF_VOID_P >= 8". > > Probably one day we'll remove that code, but it seems strange to have > > pg_popcount_slow() do it and not pg_popcount_fast(). > > The only reason I left it out was because I couldn't convince myself that > it wasn't dead code, given we assume that popcntq is available in > pg_popcount64_fast() today. But I don't see any harm in adding that just > in case.
It's probably more of a case of using native instructions rather than ones that might be implemented only via microcode. For the record, I don't know if that would be the case for popcntq on x86 32-bit and I don't have the hardware to test it. It just seems less risky just to do it. David
