[hal-01100773] An Axiomatic Memory Model for POWER Multiprocessors

The growing complexity of hardware optimizations employed by multiprocessors leads to subtle distinctions among allowed and dis-allowed behaviors, posing challenges in specifying their memory models formally and accurately, and in understanding and analyzing the behav-ior of concurrent software. This complexity is particularly evident in the IBM R Power Architecture R , for which a faithful specification was pub-lished only in 2011 using an operational style. In this paper we present an equivalent axiomatic specification, which is more abstract and con-cise. Although not officially sanctioned by the vendor, our results indicate that this axiomatic specification provides a reasonable basis for reasoning about current IBM R POWER R multiprocessors. We establish the equiva-lence of the axiomatic and operational specifications using both manual proof and extensive testing. To demonstrate that the constraint-based style of axiomatic specification is more amenable to computer-aided ver-ification, we develop a SAT-based tool for evaluating possible outcomes of multi-threaded test programs, and we show that this tool is signifi-cantly more efficient than a tool based on an operational specification.



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