There's been multiple mailing list discussions in past months and years about having a Fortran language front-end to LLVM, similar to Clang being the C/Objective-C/C++ compiler front-end to LLVM. The closest Fortran support would be using DragonEgg as a GCC plug-in to take some advantage of LLVM.
While not touched in one year, there was a FLANG project on GitHub to provide Fortran language support within LLVM. That project never got off the ground and doesn't fully support any Fortran standard.
Being proposed now as another possible LLVM Google Summer of Code project is a new FLANG, a.k.a. Fortran LLVM compiler support. The GSoC 2013 proposal can be read on GitHub.
This proposal is rather ambitious with the Irish student developer wanting to implement Fortran support via a "Flang" front-end in the proces of just 12 weeks. This would build upon earlier "Flang" work and taking advantage of the C++ LLVM API.
While there's much interest around a Fortran front-end to LLVM, the consensus so far on the LLVM developer's mailing list is that FLANG would be far too ambitious as a summer project. We'll have to wait and see whether the project is approved and what level of success it can achieve as Fortran language support over the course of one summer.