Implementation of Chaitin's graph coloring register allocation algorithm in C.

$ make
$ ./cgc 
~~~~~~~~~~~~~~~~
Cha Cha Chaitin:
----------------
Enter number of vertices in graph: 3
* added vertices a through c
Enter number of edges: 2
Enter edges one by one in form <source><space><target>
Edge 1: a b
Edge 2: a c
* added 2 edges
Enter number of colors: 2
* 2 colored graph
a : 0 -> b c
b : 1 -> a
c : 1 -> a
Total: 3 nodes

Vertices are automatically named a-z. Graphs are undirected.

a : 1 -> b c
b : 0 -> a
c : 0 -> a
Total: 3 nodes 2 colors

• a, b, and c are the vertices.
• 1, 0, and 0 are the colors of the vertices.
• Characters after the -> are the vertices to which an edge exists.

This is a graph with 3 vertices where b and c are connected to a.

If a graph is not n-colorable then a variable(a vertex) is spilled. Spilled vertices are removed from the graph and not colored.

A spilled vertex is represented with color -1.

a : -1 -> b c
b : 0 -> a
c : 0 -> a
Total: 3 nodes 1 color

Since 1-coloring the graph was impossible, a was spilled.