Gentoo's Bugzilla –
Attachment 324682 Details for
Bug 435646sys-libs/glibc-2.15-r2 - In file included from ../sysdeps/x86_64/multiarch/strstr.c:21:0, [...], /usr/lib/gcc/x86_64-pc-linux-gnu/4.6.3/include/nmmintrin.h:31:3: error: #error "SSE4.2 instruction set not enabled"