AMD uses LLVM for our code generation on x86, so when LLVM adds support for AVX, we will inherit it when we update to that version.
Thank you for your swift reply.
Just an update. I looked into LLVM's support for AVX and it seems that they have been working on it since 2009, but as of Nov 1, 2010, it's not yet ready for full scale use.
Also, after AVX they intend to add support for FMA4:
Some AVX stuff has been added to the LLVM API: (Search for AVX)