Decoupling Computation and Result Write-Back for Thread-Level Parallelization

Thread-level speculation (TLS) is an approach to enhance the opportunity of parallelization of programs. A TLS system enables multiple threads to begin the execution of tasks in parallel even if there may be the dependency between tasks. When any dependency violation is detected, the TLS system enforces the violating thread to abort and re-execute the task. So, the frequency of aborts is one of the factors that damage the performance of the speculative execution. This article proposes a new technique named the code shelving, which enables threads not to need to abort. It is available not only for TLS but also as a flexible synchronization technique in conventional and non-speculatively parallel execution. The authors implemented the code shelving on their parallel execution system called Speculative Memory (SM) and verified the effectiveness of the code shelving.