My experience is that most non-trivial assembly language is doing processing of large chunks of data (high-precision math, encrypting blocks of data, FFTs, etc.

My experience is that most non-trivial assembly language is doing processing of large chunks of data (high-precision math, encrypting blocks of data, FFTs, etc.) and therefore the startup cost of the function is not significant, so a tiny bit of inefficiency in that area is not something people care about. Or, put another way, writing tiny little assembly language functions is probably not worth it because the mere fact that you are using assembly language instead of (say) C/C++ means that you have missed many opportunities (code reordering, inlining, etc.) so assembly language functions _should_ be doing enough work to justify their calling cost. But, I'm not working on an assembler or even using one so I don't think I'll even file a feature request.