https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87733
--- Comment #30 from Rich Felker <bugdal at aerifal dot cx> --- > You need to make $r10 not a clobber but an inout, of course. And not That's not a correct constraint, because it's clobbered by the kernel between the first syscall instruction's execution and the second execution of the addu instruction after the kernel returns to restart it. $10 absolutely needs to be a clobber because the kernel clobbers it. The asm block can't use any registers the kernel clobbers. > allowing the "i" just costs one more register move, not so bad imo. > So you do have a workaround now. Of course we should see if this can > actually be fixed instead ;-) I don't follow. As long as the "i" gets chosen, the asm inlines nicely. If not, it forces a gratuitous stack frame to spill a non-clobberlisted register to use as the input. The code has been working for the past 8 years with the "0"(r2) input constraint added, and would clearly be valid if r2 were pre-initialized with something.
