Well, decuda should be a quite sure way to find out, though I guess this is likely to depend on the architecture version (i.e. change with future graphic cards).
The decuda output uses the “@$pn.cond” prefix for this I think (where pn is the predicate register and cond is the condition on which the instruction behind this is executed).
I do not see any way to influence/see this in ptx, though that is no surprise since IMO the limit is likely to depend on the specific GPU (at least in the future),and the GPU-specific stuff is done in ptxas.
And please take care not to write “prediction” when you mean “predication”, while I am not sure if the later is really a valid word, the former already has a meaning, and a very different one.