Fast Data-Dependence Profiling by Skipping Repeatedly Executed Memory Operations

Abstract

Nowadays, more and more program analysis tools adopt profiling approaches in order to obtain data dependences because of their ability of tracking dynamically allocated memory, pointers, and array indices. However, dependence profiling suffers from high time overhead. To lower the overhead, former dependence profiling techniques either exploit features of the specific program analyses they are designed for, or let the profiling process run in parallel. Although they successfully lowered the time overhead of dependence profiling by a certain amount, none of them have tried to solve the fundamental problem that causes the high time overhead: the memory operations that are repeatedly executed in loops. In most of the time, these memory operations lead to exactly the same data dependences. However, a profiling method has to profile all these memory operations over and over again in order to not miss a single dependence that may occur just once. In this paper, we present a method that allow a dependence profiling technique to skip memory operations that are repeatedly executed in loops without missing any single data dependence. Our method works with all types of loops and does not require any prepossessing like source annotation of the input code. Experiment results show that our method can lower the time overhead of data-dependence profiling by up to 52 %.