Ensuring Consistency between Cycle-Accurate and Instruction Set Simulators

Abstract

The xMAS micro-architecture modeling language has been introduced by Intel to facilitate the formal representation and analysis of on-chip interconnect fabrics. In this paper, we introduce xMAStime, a new domain-specific language inspired by xMAS. xMAStime allows the modeling of full micro-architectures comprising certain classes of CPU pipelines, caches, and RAM. Given an in-order pipeline model in xMAStime, we automatically generate both a Cycle-Accurate, Bit-Accurate (CABA) hardware simulator and a timed instruction set simulator where time is accounted with safe upper bounds, as in the pipeline analysis step of Worst-Case Execution Time (WCET) analysis. The approach relies on the theory of endochronous systems, which allows us to ensure functional equivalence and timing consistency between the two generated simulators, using a delay-insensitivity argument. xMAStime is implemented over Lucid Synchrone-a dataflow synchronous language featuring a higher order type system and type inference, which facilitate the definition of our DSL. We use the new DSL to model and synthesize simulation code for a full-fledged MIPS32-based architecture.