[Bug c/126552] const-qualified local register variable used as an asm operand is silently discarded

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D126552

--- Comment #7 from Bernie Innocenti <bernie at codewiz dot org> ---
> Why does this use the "f" constraint when it wants an address register?

Dropping "f" doesn't make any difference, I tried that in the
"call_const_plain_r()" case of my initial report:

   https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D65196

I think it was there so the same macros can be used with functions taking fp
args as well as integral args.=