[gcc r12-10575] libstdc++: Fix test on x86_64 and non-simd targets

[Matthias Kretz]

https://gcc.gnu.org/g:169d4d1addaac7eef6cde4049aa8b4f3d81c28b0

commit r12-10575-g169d4d1addaac7eef6cde4049aa8b4f3d81c28b0
Author: Matthias Kretz <m.kretz@gsi.de>
Date:   Fri Jun 21 16:22:22 2024 +0200

    libstdc++: Fix test on x86_64 and non-simd targets
    
    * Running a test compiled with AVX512 instructions requires
    avx512f_runtime not just avx512f.
    
    * The 'reduce2' test violated an invariant of fixed_size_simd_mask and
    thus failed on all targets without 16-Byte vector builtins enabled (in
    bits/simd.h).
    
    Signed-off-by: Matthias Kretz <m.kretz@gsi.de>
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/115575
            * testsuite/experimental/simd/pr115454_find_last_set.cc: Require
            avx512f_runtime. Don't memcpy fixed_size masks.
    
    (cherry picked from commit 77f321435b4ac37992c2ed6737ca0caa1dd50551)

Diff:
---
 libstdc++-v3/testsuite/experimental/simd/pr115454_find_last_set.cc | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/testsuite/experimental/simd/pr115454_find_last_set.cc b/libstdc++-v3/testsuite/experimental/simd/pr115454_find_last_set.cc
index b47f19d3067..25a713b4e94 100644
--- a/libstdc++-v3/testsuite/experimental/simd/pr115454_find_last_set.cc
+++ b/libstdc++-v3/testsuite/experimental/simd/pr115454_find_last_set.cc
@@ -1,7 +1,7 @@
 // { dg-options "-std=gnu++17" }
 // { dg-do run { target *-*-* } }
 // { dg-require-effective-target c++17 }
-// { dg-additional-options "-march=x86-64-v4" { target avx512f } }
+// { dg-additional-options "-march=x86-64-v4" { target avx512f_runtime } }
 // { dg-require-cmath "" }
 
 #include <experimental/simd>
@@ -25,7 +25,9 @@ int reduce2()
 {
   using M8 = typename V<short, 8>::mask_type;
   using M4 = typename V<int, 4>::mask_type;
-  if constexpr (sizeof(M8) == sizeof(M4))
+  if constexpr (sizeof(M8) == sizeof(M4)
+		  && !std::is_same_v<M4, stdx::fixed_size_simd_mask<int, 4>>)
+    // fixed_size invariant: padding bits of masks are zero, the memcpy would violate that
     {
       M4 k;
       __builtin_memcpy(&__data(k), &__data(M8(true)), sizeof(M4));