From: Peter Krefting <peter@softwolves.pp.se>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH] configure: Remove dcbzl check for e500v1 and e500v2 architectures
Date: Wed, 28 Sep 2022 13:52:46 +0100 (CET)
Message-ID: <6d864071-af72-e562-65c6-be714a4ca3@softwolves.pp.se> (raw)
In-Reply-To: <1EC39695-B7C3-4EF3-A2F9-D60280B14EE5@remlab.net>
Hi!
>> The DCBZL instruction is not available for the e500v1 and e500v2
>> architectures, but may still be recognized by the toolchain, so we need to
>> remove the test for it explicitly for these architectures.
> Isn't this the sort of thing that's supposed ti be guarded by run-time CPU flags rather than in the configure script?
Our compiler (powerpc-btech-linux-gnuspe-gcc (crosstool-NG 1.24.0)
8.3.0) recognizes the instruction, so the configure test succeeds, but
the CPU (e500v2) crashes if it tries to execute it.
I previously had a patch (d5733936d857ce5c7d28c0bc9e89a2e2548f8895) to
suppress the instruction, but it broke at some point, this patch tries
to fix it in a slightly better way.
Having said that, the test is there due to the fix in
a4adb60858f1fa0b35b08576ea34e531f0f83459 (from 2003), and disabling the
instruction does not bring back the old optimizations as it just expects
it not to work at all. But for our purposes this is not as important as h
aving a working library.
--
\\// Peter - http://www.softwolves.pp.se/
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next prev parent reply other threads:[~2022-09-28 12:52 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-26 10:51 Peter Krefting
2022-09-26 11:24 ` Rémi Denis-Courmont
2022-09-28 12:52 ` Peter Krefting [this message]
2022-09-28 14:28 ` Rémi Denis-Courmont
2022-09-28 15:15 ` Peter Krefting
2024-01-05 21:35 ` Michael Niedermayer
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