Filed #76953 (similar to this post from a few years ago, which unfortunately got little traffic). Even a trivial 10-element global array codegens move instructions without -O. 
At a minimum, I hope that simple static arrays of numeric constants could be done this way without it being expensive; my own use cases aren't embedded programming but it feels like this would be a major need there to embed data without incurring major codegen/runtime costs.