Structural Optimization on Superscalar Processors

Superblock scheduling is a common technique to increase the level of instruction level parallelism (ILP) in generated code. Compared to a basic block, the superblock gives an optimizer or scheduler a longer range over which instructions can be moved. The bookkeeping necessary to execute that move is less than would be necessary inside an arbitrary trace region. Additionally, the process of forming superblocks generates more instructions that are eligible for movement. These factors combine to produce a significant increase in the ILP of a section of code. This work investigates the effect of structural optimization when targeting an x86 processor. We show that the effect of structural compilation to specialize the control flow for the typical path of execution is still beneficial.