29.10.7.4 basic_simd exposition only conditional operators [simd.cond]
friend constexpr basic_simd
simd-select-impl(const mask_type& mask, const basic_simd& a, const basic_simd& b) noexcept;
Returns: A
basic_simd object where the
ith element equals
mask[i] ? a[i] : b[i] for all
i in the range of
[
0, size())
.