Inter-block Scoreboard Scheduling in a JIT Compiler for VLIW Processors

We present a postpass instruction scheduling technique suitable for Just-In-Time (JIT) compilers targeted to VLIW processors. Its key features are: reduced compilation time and memory requirements; satisfaction of scheduling constraints along all program paths; and the ability to preserve existing prepass schedules, including software pipelines. This is achieved by combining two ideas: instruction scheduling similar to the dynamic scheduler of an out-of-order superscalar processor; the satisfaction of inter-block scheduling constraints by propagating them across the control-flow graph until fixed-point. We implemented this technique in a Common Language Infrastructure JIT compiler for the ST200 VLIW processors and the ARM processors.