I don't know how, but I forgot to implement the is_simd_flag_type trait. This fixes it. No new check-simd failures on x86_64-pc-linux-gnu --------------- 8< ------------------ Signed-off-by: Matthias Kretz libstdc++-v3/ChangeLog: * include/experimental/bits/simd.h (is_simd_flag_type): New. (_IsSimdFlagType): New. (copy_from, copy_to, load ctors): Constrain _Flags using _IsSimdFlagType. --- libstdc++-v3/include/experimental/bits/simd.h | 52 ++++++++++++++----- 1 file changed, 39 insertions(+), 13 deletions(-) -- ────────────────────────────────────────────────────────────────────────── Dr. Matthias Kretz https://mattkretz.github.io GSI Helmholtz Centre for Heavy Ion Research https://gsi.de stdₓ::simd ──────────────────────────────────────────────────────────────────────────