There is an interesting project going forward here: http://libjpeg-turbo.virtualgl.org/ - it's a API/ABI compatible libjpeg implementation making use of SSE/MMX. It claims to be twice as fast using SSE and at least 25% on other platforms. According to this page, Fedora will switch to this library, so it might make sense to provide this as an alternative to libjpeg (may be by using a virtual?) Also, what's very important is that the project seems to be more open than original libjpeg. That can only be a plus to gentoo Reproducible: Always
*** This bug has been marked as a duplicate of bug 327487 ***