Re: Popcount optimization using AVX512

From: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
To: "Amonson, Paul D" <paul(dot)d(dot)amonson(at)intel(dot)com>
Cc: Nathan Bossart <nathandbossart(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, "Shankaran, Akash" <akash(dot)shankaran(at)intel(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Popcount optimization using AVX512
Date: 2024-03-07 17:53:12
Message-ID: 202403071753.mirzr4kppbkb@alvherre.pgsql
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On 2024-Mar-04, Amonson, Paul D wrote:

> > -#define LARGE_OFF_T (((off_t) 1 << 62) - 1 + ((off_t) 1 << 62))
> > +#define LARGE_OFF_T ((((off_t) 1 << 31) << 31) - 1 + (((off_t) 1 << 31)
> > +<< 31))
> >
> > IME this means that the autoconf you are using has been patched. A
> > quick search on the mailing lists seems to indicate that it might be
> > specific to Debian [1].
>
> I am not sure what the ask is here? I made changes to the
> configure.ac and ran autoconf2.69 to get builds to succeed. Do you
> have a separate feedback here?

So what happens here is that autoconf-2.69 as shipped by Debian contains
some patches on top of the one released by GNU. We use the latter, so
if you run Debian's, then the generated configure script will contain
the differences coming from Debian's version.

Really, I don't think this is very important as a review point, because
if the configure.ac file is changed in the patch, it's best for the
committer to run autoconf on their own, using a pristine GNU autoconf;
the configure file in the submitted patch is not relevant, only
configure.ac matters.

What committers do (or should do) is keep an install of autoconf-2.69
straight from GNU.

--
Álvaro Herrera Breisgau, Deutschland — https://www.EnterpriseDB.com/

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