Re: Improve CRC32C performance on SSE4.2

From: Nathan Bossart <nathandbossart(at)gmail(dot)com>
To: "Devulapalli, Raghuveer" <raghuveer(dot)devulapalli(at)intel(dot)com>
Cc: John Naylor <johncnaylorls(at)gmail(dot)com>, Andy Fan <zhihuifan1213(at)163(dot)com>, Jesper Pedersen <jesperpedersen(dot)db(at)gmail(dot)com>, Tomas Vondra <tomas(at)vondra(dot)me>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>, "Shankaran, Akash" <akash(dot)shankaran(at)intel(dot)com>
Subject: Re: Improve CRC32C performance on SSE4.2
Date: 2025-06-16 22:14:19
Message-ID: aFCXO7MztuZezdpH@nathan
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On Mon, Jun 16, 2025 at 06:31:11PM +0000, Devulapalli, Raghuveer wrote:
> Attached is a simple reproducer. It passes with clang v16 -O0, but fails
> with 17 and 18 only when built with -O0..

I've just started looking into this, but the difference in code generated
for _mm512_castsi128_si512() between gcc, clang 16, and clang 17 looks
interesting.

--
nathan

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