Gentoo's Bugzilla –
Attachment 593990 Details for
Bug 698572sci-libs/fftw-3.3.6_p2 USE=cpu_flags_x86_avx2 - In file included from n1fv_2.c:3: .../work/fftw-3.3.6-pl2/simd-support/simd-avx2.h:43:2: error: #error "compiling simd-avx2.h without avx2 support"