https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90181
--- Comment #7 from Segher Boessenkool <segher at gcc dot gnu.org> --- (In reply to nfxjfg from comment #6) > Yes, it's clear that that the constraint can't be _just_ the register name, > since they'll clash with builtin constraints now or with future > architectures (which may add arbitrary register names). The proposed > "*registername" is pretty nice, though. Having this would be great. Hrm, "*" already has a meaning with current GCC (it essentially is ignored in inline asm)... It might be better to have some new syntax that gives an error with older GCC. > I didn't find a RISC-V builtin for ecall (maybe I looked in the wrong > place). That wouldbn't be sufficient anyway. Right, you would need a builtin for every calling convention for syscalls. The aren't too many of those though? > Another situation where I > wanted to specify many fixed register constraints was a piece of inline code > that did some syscalls without touching the stack (it needed all inputs as > registers, and in specific registers, and have some registers for free use > by the asm code itself). A biggish piece of asm like that might be better as actual assembler code than as inline asm, you may want to consider that?