Soft Error Effects Analysis and Mitigation in VLIW Safety-Critical Applications

VLIW architectures are widely employed in several embedded signal applications since they offer the opportunity to obtain high computational performances while maintaining reduced clock rate and power consumption. Recently, VLIW processors are being considered for employment in various embedded processing systems, including safety-critical ones (e.g., in the aerospace, automotive and rail transport domains). Terrestrial safety-critical applications based on newer nano-scale technologies raise increasing concerns about transient errors induced by neutrons. Therefore, techniques to effectively estimate and improve the reliability of VLIW processors are of great interest. In this paper, we present a novel technique aimed to further improve the efficiency of the Triple Modular Redundancy (TMR) hardening-technique applied at the software level on VLIW processors. In particular, we first experimentally demonstrate that the TMR-based software technique, when applied at the C code level, is not able to cope with most of the failures affecting user logic resources. Then, we propose a method able to analyze and modify the TMR-based code for a generic VLIW processor in order to improve the fault tolerance of the executed application without modifying the VLIW processor. In details, the proposed technique is able to reduce the number of cross-domain errors affecting the TMR-hardened code of a VLIW processor data path. We provide figures about performance and fault coverage for both the un-protected and protected versions of a set of benchmark applications, thus demonstrating the benefits and limitations of our approach.