An Evaluation of Misaligned Data Access Handling Mechanisms in Dynamic Binary Translation Systems

Binary translation (BT) has been an important approach to migrate application software across instruction set architectures (ISAs). Some architectures, such as X86, allow misaligned data accesses (MDAs), while most modern architectures have the alignment restriction that requires data to be aligned in memory on natural boundaries. In a binary translation system, where the source ISA allows MDA and the target ISA does not, memory operations must be carefully translated to satisfy the alignment restriction. Naive translation will cause frequent misaligned data access traps to occur at runtime on the target machine, and severely slow down the migrated application.This paper evaluates different approaches in handling MDA in binary translation systems. It also proposes a new mechanism to deal with MDAs. Measurements based on SPEC CPU2000 and CPU2006 benchmark show that the proposed approach can significantly outperform existing methods.