LLVM X86 AVX Backend

Hello,

I have to work on x86 avx backend to add certain things. Is there any complete flow/ tutorial/ document available to do this?

Need help

Thank You

Might want to be less mysterious and more specific about "certain things"
in order for people to give you relevant information. Worst case you have
the source code..

i want to add some new extension like avx how can i do?