Date: Mon, 18 Mar 2024 16:26:00 -0500
From: Nathan Bossart <nathandbossart@gmail.com>
To: "Amonson, Paul D" <paul.d.amonson@intel.com>
Cc: David Rowley <dgrowleyml@gmail.com>, Andres Freund <andres@anarazel.de>,
	Alvaro Herrera <alvherre@alvh.no-ip.org>,
	"Shankaran, Akash" <akash.shankaran@intel.com>,
	Noah Misch <noah@leadboat.com>, Tom Lane <tgl@sss.pgh.pa.us>,
	Matthias van de Meent <boekewurm+postgres@gmail.com>,
	"pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
Subject: Re: Popcount optimization using AVX512
Message-ID: <20240318212600.GA655785@nathanxps13>
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On Mon, Mar 18, 2024 at 09:22:43PM +0000, Amonson, Paul D wrote:
>> 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.
> 
> I am not sure how to read this. Does this mean that for popcount32_fast
> and popcount64_fast I can assume that the x86(_64) instructions exists
> and stop doing the runtime checks for instruction availability?

I think my question boils down to "if pg_popcount_available() returns true,
can I safely assume I'm on a 64-bit machine?"

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com