An Architecture & Mechanism for Supporting Speculative Execution of a Context-full Reconfigurable Function Unit

Recently researchers have shown interest in integrating Reconfigurable logic into conventional processors as a Reconfigurable Function Unit (RFU). A context-full RFU supports holding intermediate results inside itself, which eliminates some data movement overheads and has some other benefits. Most contemporary processors support out-of-order execution and speculation. When a context-full RFU is integrated into a speculative processor, if a speculative RFU instruction has modified the RFU context but cannot be committed in the end, the RFU context must be recovered. Traditional mechanisms to handle speculative execution of instructions cannot effectively address this issue. Because of the design complexity, previous proposals did not support context-full RFUs in speculative processors. In this paper, we propose an architecture & mechanism for supporting speculative execution of a context-full RFU in in-order issue, out-of-order execution processors. It does not require too much extra space for the RFU context storage and the performance penalty shown to be low in practice.