Live Range Splitting in a Graph Coloring Register Allocator

Graph coloring is the dominant paradigm for global register allocation [8, 7, 4]. Coloring allocators use an interference graph, Z, to model conflicts that prevent two values from sharing a register. Nodes in 2: represent live ranges. An edge between two nodes indicates that they are simultaneously live azld, thus, cannot share a register. The allocator tries to construct a k-coloring of 2:, for k equal to the number of registers on the target machine. If it succeeds, it maps the colors onto the machine registers to produce an allocation. Unfortunately, it may not discover a k-coloring. In that case, it sp///s some live ranges by saving their values to memory. Early coloring allocators spilled live ranges completely - at each definition and use. This approach often introduces more spill code than necessary. This paper presents a global approach that avoids some spill code by splitting the live range, breaking it into smaller pieces. We are not the first to study this problem. Bergner e...

• Type: Journal
• Year: 1998
• Where: CC
• Authors: Keith D. Cooper, L. Taylor Simpson
• Keywords: CC 1998, Global Register Allocation, Live Range, Live Range Splitting, System Software