LLVM is being added to the OpenGL stack. Right now the feature-set of programs using OpenGL is limited by the machine they run on. Because the Mac has a smaller market size, it is not economical to develop software that relies on more recent capabilities of 3D hardware. Although the Mac’s OpenGL drivers apparently already try to fill in some of the gaps, LLVM should extend the range of supported features because it’s a full blown compiler rather than a set of optimized canned routines.
A similar technology exists for Windows and gives pretty good performance.
I find this another interesting example of Apple leveraging open source software to improve its proprietary OS: They employed LLVM’s main author, Chris Lattner, who’s PhD topic was LLVM. This may end up being one of Leopard’s most important features: it will make CoreAnimation and CoreVideo available to many more Macs. It continues Mac OS X’ counter-tradition of each new release being faster than the previous one.