Dynamic Binary Translators (DBT) and Dynamic Binary Opti- mization (DBO) by software are used widely for several reasons including performance, design simplification and virtualization. However, the software layer in such systems introduces non- negligible overheads which affect performance and user experi- ence. Hence, reducing DBT/DBO overheads is of paramount im- portance. In addition, reduced overheads have interesting collateral effects in the rest of the software layer, such as allowing optimiza- tions to be applied earlier. A cost-effective solution to this problem is to provide hardware support to speed up the primitives of the software layer, paying special attention to automate DBT/DBO mechanisms and leave the heuristics to the software, which is more flexible. In this work, we have characterized the overheads of a DBO sys- tem using DynamoRIO implementing several basic optimizations. We have seen that the computation of the Data Dependence Graph (DDG) accounts for 5%-10% of the execution time. For this rea- son, we propose to add hardware support for this task in the form of a new functional unit, called DDGacc, which is integrated in a conventional pipeline processor and is operated through new ISA instructions. Our evaluation shows that DDGacc reduces the cost of computing the DDG by 32x, which reduces overall execution time by 5%-10% on average and up to 18% for applications where the DBO optimizes large code footprints.

Peer Reviewed