Automatic Analysis of Scratch-Pad Memory Code for Heterogeneous Multicore Processors

Abstract

AbstractModern multicore processors, such as the Cell Broadband Engine, achieve high performance by equipping accelerator cores with small “scratch-pad” memories. The price for increased performance is higher programming complexity – the programmer must manually orchestrate data movement using direct memory access (DMA) operations. Programming using asynchronous DMAs is error-prone, and DMA races can lead to nondeterministic bugs which are hard to reproduce and fix. We present a method for DMA race analysis which automatically instruments the program with assertions modelling the semantics of a memory flow controller. To enable automatic verification of instrumented programs, we present a new formulation of k-induction geared towards software, as a proof rule operating on loops. We present a tool, Scratch, which we apply to a large set of programs supplied with the IBM Cell SDK, in which we discover a previously unknown bug. Our experimental results indicate that our k-induction method performs extremely well on this problem class. To our knowledge, this marks both the first application of k-induction to software verification, and the first example of software model checking for heterogeneous multicore processors.KeywordsModel CheckLoop IterationDirect Memory AccessProof RuleBounded Model CheckThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.