How to get "round_z" in asm code by HLSL?

Question

When I'm reading the asm code ,I dont know how to get the instruction "round_" just below. Which function should I use in HLSL to get it? Or had it be replaced with the update of versions? The following is asm code:round_z r15.x

Answer 1

There doesn't appear to be one, you can easily implement it though:

dst = sign(src) * floor(abs(src))

Answer 2

The function you are looking for is modf. In the following snippet, i is the result of round_z:

float i;
modf(input, i);