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From: "iam at valdikss dot org.ru" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/100758] __builtin_cpu_supports does not (always) detect "sse2"
Date: Wed, 01 Feb 2023 14:23:45 +0000	[thread overview]
Message-ID: <bug-100758-4-so7HsBtW4V@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-100758-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100758

--- Comment #11 from ValdikSS <iam at valdikss dot org.ru> ---
Well, the function is called __builtin_cpu_supports, for which one might expect
that it just checks CPUID and returns reliable results, while in reality it
operates using the build-in CPU support list. The function does not return an
error if it's unable to detect the feature, resulting in incorrect results,
which makes the function unreliable. The fact that it may not always detect
features which are present in the CPU is not documented, which brings the
confusion among developers such as this bug.

VIA processors have progressed into Zhaoxin CPU family which is fairly recent
(2014-2019, with plans to release new processors soon). They both share almost
the same CPUID data, that's why adding support for either of these CPU
automatically implements the other one.

  parent reply	other threads:[~2023-02-01 14:23 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-25 18:37 [Bug c/100758] New: " gcc at eckner dot net
2021-05-26  7:57 ` [Bug target/100758] " marxin at gcc dot gnu.org
2021-05-26  9:12 ` gcc at eckner dot net
2021-05-26  9:23 ` marxin at gcc dot gnu.org
2021-05-26  9:46 ` gcc at eckner dot net
2021-05-26  9:54 ` rguenth at gcc dot gnu.org
2021-05-26 10:09 ` marxin at gcc dot gnu.org
2021-05-26 10:13 ` gcc at eckner dot net
2021-06-01 13:26 ` marxin at gcc dot gnu.org
2023-01-27 20:48 ` iam at valdikss dot org.ru
2023-02-01 14:03 ` marxin at gcc dot gnu.org
2023-02-01 14:23 ` iam at valdikss dot org.ru [this message]
2023-02-01 14:32 ` marxin at gcc dot gnu.org
2023-02-09 10:50 ` cvs-commit at gcc dot gnu.org
2023-02-09 11:40 ` jakub at gcc dot gnu.org
2023-02-09 11:47 ` marxin at gcc dot gnu.org
2023-02-09 12:22 ` jakub at gcc dot gnu.org
2023-02-09 16:22 ` gcc at eckner dot net
2023-02-09 16:37 ` jakub at gcc dot gnu.org
2023-02-09 16:45 ` cvs-commit at gcc dot gnu.org
2023-02-09 20:37 ` gcc at eckner dot net
2023-02-09 21:35 ` iam at valdikss dot org.ru
2023-02-10  8:27 ` marxin at gcc dot gnu.org
2023-02-10  9:45 ` jakub at gcc dot gnu.org
2023-02-20  9:50 ` Mayshao-oc at zhaoxin dot com
2023-03-19  5:29 ` cvs-commit at gcc dot gnu.org
2023-05-02 20:14 ` cvs-commit at gcc dot gnu.org
2023-05-03 15:21 ` cvs-commit at gcc dot gnu.org

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