Abstract: Based on the work of Cytron and Cooper, we employ the concept of dominance frontier inverse (DFI) to present an iterative algorithm to simultaneously place -nodes for all variables of a function. The set DFI(x) is a set of the nodes N whose dominance frontier is x. The set DFI(x) has one important property: The nodes in the set DFI(x) must be the nodes whose level is no smaller than the level of x on the dominator tree. For each node y contained in the set DFI(x), the variables defined on node y should be placed on node x, and if there are -nodes only, the variables of -nodes should also be placed on x. In fact, the DFI set neednt be computed when placing -nodes in the algorithm of this paper, because a variable set is adopted to hold the -nodes. The algorithm firstly visits the dominator tree in a bottom-up traversal by levels, and then iteratively computes fixed point for the -nodes sets on the join nodes with the same level. The innovation is that the algorithm can directly work on the dominator tree. And it merges the former two-step algorithm into one. Experimental results of the C Specint2000 show that this algorithm is much faster than Cytrons original algorithm, and is also comparable with Cytrons -placement algorithm based on Coopers DF algorithm.