x86 rep prefix with a count of zero: what happens?

x86 rep prefix with an initial count of zero: what happens?

Please be kind. :-) I know I just need to test this myself somehow, but I don’t have the necessary tools at hand at the moment. :-(

I think Félix Cloutier says explicitly it’s a while count != 0 loop with the test at the top, which is the sane expected behaviour, but most of the many vague reports I’ve seen elsewhere suggest that there’s no initial test for zero so it would be like a countdown with a test at the end and so disaster if it’s repeat {… count —=1; } until count == 0; or who knows.