https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97708
--- Comment #18 from Boris <bp at alien8 dot de> --- It would be awesome if this text continued: "... and specify any constraint letter that matches the register. If the operand constraint doesn't match the register, former has higher priority over the local register specification and gcc will adhere to the constraint specification." I'll even put it in a patch and send it on... :-)