When solving backward data-flow problems, many resources (Wikipedia and many presentations found online) recommend traversing the control-flow graph (CFG) in post-order for fastest convergence, which makes sense.
Other resources (such as the "Engineering a Compiler" book) suggest to use reverse post-order (RPO) on the reversed CFG instead.
... and PO(graph) != RPO(rev(graph)) in some cases involving cycles.
My question is: which resource is right? Post-order makes sense, so why not just use that and save the CFG inversion? Why would I use RPO on reversed CFG instead?