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. r~