@target_clones ala clang?

[Bruce Carneal]

Is implementing a clang style @target_clones capability for LDC a 
big ask?

@target_clones only works on a per-function basis within a single 
CPU family currently but can easily be employed in modules 
intended for multi CPU family use by selecting the @target_clones 
string from within version(CPU_family_predefine) statements. This 
might be useful for the front end, runtime, and Phobos as well as 
to code written with auto vectorization in mind.

There are manual workarounds and extensions, such as library 
versioning with eager or late (LTO) target binding, so it might 
not be worth more than a modest effort but I thought I'd ask.