https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87733
--- Comment #24 from Rich Felker <bugdal at aerifal dot cx> --- The reasons I was hesitant to force n to a particular register through an extra register __asm__ temp var was that I was unsure how it would interact with the "i" constraint (maybe prevent it from being used?) and that this is code that needs to be inlined all over the place, and adding more specific-register constraints usually hurts register allocation in all functions where it's used. If the "0"(r2) input constraint seems unsafe to rely on with r2 being uninitialized (is this a real concern I should have?) just writing 0 or n to r2 before the asm would only waste one instruction and shouldn't really hurt.
