[Bug target/115362] fixed_size_simd dot product recognition and sign of determinant not working for stdx::reduce

[jondaniel879 at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115362

--- Comment #16 from Jon Daniel <jondaniel879 at gmail dot com> ---
See https://github.com/Const-me/SimdIntroArticle/ for different AVX2 DotProduct
examples and check if they have different signs with g++/clang++.