The current stable ati-drivers does not compile with the latest stable gentoo-sources. Please mark 8.35.5 (or if that is not possible: 8.34.8) stable to have a fully stable system compile. (Please be aware that even though I am marked as maintainer for ati-drivers I do not use them on a "stable" system, so I will generally not file keyword bugs like this one soon enough. If someone notices a newer ati-drivers should go stable do not wait for me.)
x86/amd64 stable and closing