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From: "marxin at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/100758] __builtin_cpu_supports does not (always) detect
 "sse2"
Date: Wed, 26 May 2021 10:09:17 +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
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |WONTFIX

--- Comment #6 from Martin Li=C5=A1ka <marxin at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #5)
> (In reply to Erich Eckner from comment #2)
> > We use this in archlinux32 to detect, if we can install packages, that =
have
> > sse2 opcodes:
> >=20
> > If one sets "Architecture =3D auto" in /etc/pacman.conf, uname only giv=
es
> > "i686" in both cases (this is how archlinux does/did the probing), and =
then,
> > we probe for sse2 to check, if we really are "i686" or "pentium4" (our
> > nomenclature for "i686" + sse2). This works well on amd and intel cpus,=
 but
> > fails on via cpus.
> >=20
> > Details about expected features: https://archlinux32.org/architecture/
> >=20
> > We can add some cumbersome code which probes for sse2, but I'd really p=
refer
> > some compiler builtin instead :-)
>=20
> Eh, including cpuid.h and using that to check for SSE2 shouldn't be too h=
ard
> (or parsing /proc/cpuinfo).

Yeah, the following should work for you:

#include <cpuid.h>

int main()
{
  unsigned int eax, ebx, ecx, edx;
  __get_cpuid(0, &eax, &ebx, &ecx, &edx);

  if (edx & bit_SSE2)
    __builtin_printf ("has SSE2\n");
}=