Idiom recognition in the Polaris parallelizing compiler

The elimination of induction variables and the parallelization of reductions in FORTRAN programs have been shown to be integral to performance improvement on parallel computers [7, 8]. As part of the Polaris project [5], compiler passes that recognize these idioms have been implemented and evaluated. Developing these techniques to the point necessary to achieve signi cant speedups on real applications has prompted solutions to problems that have not been addressed in previous reports on idiom recognition techniques. These include analysis techniques capable of disproving zero-trip loops, symbolic handling facilities to compute closed forms of recurrences, and interfaces to other compilation passes such as the data-dependence test. In comparison, the recognition phase of solving induction variables, which has receivedmost attention so far, has in fact turned out to be relatively straightforward. This paper provides an overview of techniques described in more detail in [12].