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From: "marxin at gcc dot gnu.org" <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 14:32:32 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100758

Martin Li=C5=A1ka <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |Mayshao-oc at zhaoxin dot =
com

--- Comment #12 from Martin Li=C5=A1ka <marxin at gcc dot gnu.org> ---
(In reply to ValdikSS from comment #11)
> 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.

Sure, it's not perfect, I can confirm that. I'm going to introduce a
documentation entry for this limitation.=20

>=20
> VIA processors have progressed into Zhaoxin CPU family which is fairly
> recent (2014-2019, with plans to release new processors soon).

Yep, and we support these (vendor =3D=3D signature_SHANGHAI_ebx) correctly =
since
r13-713-ga239aff82c3771.

Maybe the author of the commit will be interested in old VIA CPUs?=