Hi Amr,
Not from AMD, but here is my perception about the issues you mentioned :
1- Yes, there is currently no implementation of double precision transcendentals in hardware nor in software. Hopefully AMD will release a software implementation soon...
2- The topic you mentioned was about floating-point constants in the code. That is, if you write
double a = 1.23456789012345;
it will be truncated to something like
double a = 1.2345679f;
Passing double variables using function parameters, stream or constant memory should work correctly.
3- From my own tests on a 3850, it appears that the double precision MAD is actually fused (computes a*b+c exactly, then rounds at the end), though I have not seen it mentioned anywhere. So you might end up with a result more precise than on the CPU if you use it.
DP division is implemented in software using the fused MAD (FMA), but does not seem to provide correct rounding in every case, so it may yield different results than the CPU.
Sylvain