DMX -- Mopping Up Messes at Waffle House

DMX sentenced himself to hard labor yesterday, relieving a lowly Waffle House employee from mop duty ... and performing the filthy chore himself!

The photos were snapped at a WH in Greenville, South Carolina -- where the rapper stopped in for some late night eats ... after a Halloween party at a nearby strip club.

The rapper tells us, one of the workers -- who was mopping the floors at the time -- said he was a big fan ... and X was so touched, he grabbed the mop and finished the guy's job for him.

The Dog tells us, "I was in a good mood and felt that I would do that for him since it was 4am and [the employee] had been working all night."

The rapper adds, "The minute you get too big to mop a floor or wipe a counter, that’s the exact minute you have life f**ked up."