Improved Passive Splitting

We present a graph coloring register allocator which uses an improved form of passive live range splitting to reduce the count of dynamic spill operations. Program structure is used to guide the global splitting of live ranges and to place split operations at infrequently executed portions of the program. We also optimistically reconsider spill decisions at certain points to potentially enable more splits and/or fewer spills. Certain issues that complicate implementation of the original passive splitting method are discussed. Finally, experimental results are presented which indicate that the improved passive splitter is effective. Keywords— global register allocation, live range splitting.