Am 24.03.2011 um 18:41 schrieb Richard Henderson <r...@twiddle.net>:
> On 03/24/2011 10:29 AM, Peter Maydell wrote: >> On 24 March 2011 15:58, Alexander Graf <ag...@suse.de> wrote: >> >> This is more random comments in passing than a thorough review; sorry. >> >>> +#if HOST_LONG_BITS == 64 && defined(__GNUC__) >>> + /* assuming 64-bit hosts have __uint128_t */ >>> + __uint128_t dividend = (((__uint128_t)env->regs[r1]) << 64) | >>> + (env->regs[r1+1]); >>> + __uint128_t quotient = dividend / divisor; >>> + env->regs[r1+1] = quotient; >>> + __uint128_t remainder = dividend % divisor; >>> + env->regs[r1] = remainder; >>> +#else >>> + /* 32-bit hosts would need special wrapper functionality - just >>> abort if >>> + we encounter such a case; it's very unlikely anyways. */ >>> + cpu_abort(env, "128 -> 64/64 division not implemented\n"); >>> +#endif >> >> ...I'm still using a 32 bit system :-) > > A couple of options: > > (1) Steal code from gcc's __[u]divdi3 for implementing double-word division > via > single-word division. In this case, your "single-word" will be long long. > > (2) Implement a simple bit reduction loop. This is probably easiest. > > (3) Reuse some of the softfloat code that manipulates 128bit quantities. This > is probably the best option, particularly if the availability of __uint128 > is taught to softfloat so that it doesn't always open-code stuff that the > compiler could take care of. In all applications I've run so far this abort has _never_ fired. I'm not sure gcc even emits it. So IMHO this abort doesn't hurt. Once we get a bug report of a user hitting it, we can think of ways to implement the missing bits. For now, it's not worse than a not implemented opcode (of which we still have quite a number). Alex >
