In particular, although creating live intervals from live variable information is roughly similar to building an interference graph from live variable information, linear scan of live intervals is always much faster than coloring the interference graph.
Figure 3 shows that most of the overhead of linear scan register allocation is due to live variable analysis and "allocation setup," the coarsening of live variable information into live intervals.
This algorithm is appealing because it is simple and it minimizes expensive bitvector operations common in live variable analysis.
Table III compares the run time of applications compiled with full live variable analysis to that of applications compiled with SCC-based liveness analysis.
The second set of benchmarks consists of pathological programs that perform no useful computation but have huge numbers of simultaneously live variables that make register allocation difficult.