CRAIG: a practical framework for combining instruction scheduling and register assignment

In compilers for machines with instruction-level parallelism, the phases of register assignment and instruction scheduling can be antagonistic. Whichever phase is executed first can have negative effects on the other’s performance. This paper describes a framework, called CRAIG (Combining Register Assignment Interference Graphs), that combines register assignment and instruction scheduling to alleviate the phase-orderingproblem. CRAIG utilizes information gained from instruction scheduling before register assignment as an upper bound on the freedom needed by the instruction scheduler to attain its “best” schedule. CRAIG then allows heuristics to choose how close to the “best” schedule one can get before the cost of additional register pressure is too high. Within the context of this framework, the paper evaluates an instance of CRAIG called CRAIG0.