Linear scan to assign physical registers. SSA liveness must have been computed already. It also spills registers that are live during gc calls.

References
Linear Scan Register Allocation by Massimiliano Poletto and Vivek Sarkar http://www.cs.ucla.edu/~palsberg/course/cs132/linearscan.pdf
Linear Scan Register Allocation for the Java HotSpot Client Compiler by Christian Wimmer and http://www.ssw.uni-linz.ac.at/Research/Papers/Wimmer04Master/
Quality and Speed in Linear-scan Register Allocation by Omri Traub, Glenn Holloway, Michael D. Smith http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.34.8435

Optimization pass entry point:
linear-scan ( cfg -- )