Software Bubbles: Using Predication to Compensate for Aliasing in Software

This paper describes a technique for utilizing predication to support software pipelining on EPIC architectures in the presence of dynamic memory aliasing. The essential idea is that the compiler generates an optimistic software-pipelined schedule that assumes there is no memory aliasing. The operations in the pipeline kernel are predicated, however, so that if memory aliasing is detected by a run-time check, the predicate registers are set to disable the iterations that are so tightly overlapped as to violate the memory dependences. We refer to these disabled kernel operations as software bubbles.