Re: optimize lookups in snapshot [sub]xip arrays

On Thu, Aug 4, 2022 at 3:25 AM Nathan Bossart <nathandbossart(at)gmail(dot)com>
wrote:
> Here is a new patch set without the annotation.

Were you considering adding the new function to simd.h now that that's
committed? It's a bit up in the air what should go in there, but this new
function is low-level and generic enough to be a candidate...

I wonder if the "pg_" prefix is appropriate here, as that is most often
used for things that hide specific details *and* where the base name would
clash, like OS calls or C library functions. I'm not quite sure where the
line is drawn, but I mean that "linearsearch" is a generic algorithm and
not a specific API we are implementing, if that makes sense.

The suffix "_uint32" might be more succinct as "32" (cf pg_bswap32(),
pg_popcount32, etc). We'll likely want to search bytes sometime, so
something to keep in mind as far as naming ("_int" vs "_byte"?).

I'm not a fan of "its" as a variable name, and I'm curious what it's
intended to convey.

All the __m128i vars could technically be declared const, although I think
it doesn't matter -- it's just a hint to the reader.

Out of curiosity do we know how much we get by loading four registers
rather than two?
--
John Naylor
EDB: http://www.enterprisedb.com