llvm dev - Mar 2016 - buld_vector and shuffle_vector DAG nodes

I'm not quite clear what BUILD_VECTOR and SHUFFLE_VECTOR instructions do. I
understand that they somehow build a vector and shuffle a vector, but how
exactly it translates into a given target, that I can not figure out. I
also tried reading code for other targets but I really lack experience.
Would anyone be able to give a clear explanation, maybe even an example if
possible?

Any help is appreciated.

-- 
Rail Shafigulin
Software Engineer
Esencia Technologies
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