Cliques of Registers

Today I finished the implementation of the build_list_of_cliques algorithm. The code is here. It uses liveness analysis information to find all the cliques in a basic block. By clique I mean a set of physical and virtual registers whose live ranges overlap. If a clique contains more than K elements, where K is the number of machine registers available for register allocation, then some virtual registers must be spilled. Now I am implementing a mapping between virtual registers and the instructions where they are defined or used.