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From: "mkretz at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/109261] New: std::experimental::simd is not usable in
 several constant expressions
Date: Thu, 23 Mar 2023 10:02:31 +0000
X-Bugzilla-Reason: CC
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: libstdc++
X-Bugzilla-Version: 13.0
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X-Bugzilla-Severity: normal
X-Bugzilla-Who: mkretz at gcc dot gnu.org
X-Bugzilla-Status: UNCONFIRMED
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X-Bugzilla-Priority: P3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109261

            Bug ID: 109261
           Summary: std::experimental::simd is not usable in several
                    constant expressions
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: mkretz at gcc dot gnu.org
          Reporter: mkretz at gcc dot gnu.org
  Target Milestone: ---

std::experimental::simd wants to work in constant expressions with
-std=3Dgnu++17. But it fails for many valid cases.

Testcase (https://godbolt.org/z/sjrfMM89h):

#include <experimental/simd>
#include <array>

using V =3D std::experimental::simd<int>;
using V12 =3D std::experimental::fixed_size_simd<int, 12>;

constexpr std::array<int, V12::size()> data =3D {};
constexpr auto a =3D V12(data.data(), std::experimental::element_aligned);

constexpr auto b =3D []() constexpr {
    V12 x =3D 1;
    where(x > 0, x) =3D 0;
    return x;
}();

constexpr auto c =3D V()[0];

constexpr auto d =3D !V() && !!V();=