Problem is that some registers have non-zero default values (swd debug pin functions for example) so the set() function would still need to do a read modify write operation which isn't the theoretically optimal code gen.

Then it’s a question of annotating this function with ALWAYS_INLINE and letting the compiler optimise it.

I'd probably write a quick python script to generate a function/string table in that case (or I could even do it with a vim macro).

and then check that vim-macro in your code-base somewhere ? sure ^^ ... that will work.