I think crest may be referring to function multiversioning, but that only helps choose/call the implementation, not generate it. github.com/google/highway supp

I think crest may be referring to function multiversioning, but that only helps choose/call the implementation, not generate it. github.com/google/highway supports compiling your single source code once into several versions, and then dispatching to the best one. Disclosure: I am the main author.