Softspec: Software-based Speculative Parallelism

Abstract

We present Softspec, a technique for parallelizing sequential applications using a hybrid compile-time and run-time technique. Softspec parallelizes loops whose memory references are stride-predictable. By detecting and speculatively executing potential parallelism at runtime Softspec eliminates the need for complex program analysis required by parallelizing compilers. By using runtime information Softspec succeeds in parallelizing loops whose memory access patterns are statically indeterminable. For example, Softspec can parallelize while loops with un-analyzable exit conditions, linked list traversals, and sparse matrix applications with predictable memory patterns. We show performance results using our software prototype implementation