Use of Clip () in alpha cutouts?

I’ve seen in a number of examples and the debug of the ‘compiled’ shader the use of the following for creating a cutout or alpha for a texture:

clip (o.Alpha - Cutoff);

I get the whole alpha and cutoff, that’s not the question. I cannot find any more info on the clip() function, especially since the return doesn’t actually get assigned.

Any answers?

clip() is an intrinsic HLSL function. It “discards the current pixel if the specified value is less than zero.”