byteman: A Bitstream Manipulation Framework.

From better resource pooling for FPGA cloud providers to building dynamic execution pipelines at runtime, the capabilities of partial reconfiguration (PR) are waiting to be fully explored. However, the community still fails to materialize PR at scale, and FPGAs are only used as updatable ASICs, hence, omitting the opportunities offered by dynamically reconfiguring FPGAs at runtime. This work proposes a resourceful FPGA bitstream manipulation framework. The proposed tool provides means for parsing, modification, and generation of bitstream files, and it has been open-sourced and demonstrated in a working system. As a distinguished feature, it supports multidie FPGAs (among the 106 Xilinx 7 Series, UltraScale, and UltraScale+ devices), and enables datacenter FPGAs to be used for relocatable PR. Using the versatile tool's built-in (dis)assembler allows for manual bitstream manipulations. Bundled with an efficient bitstream manipulation core, the efficacy is demonstrated by two case studies where we observe 58 - 377x higher bitstream merging throughput than a current state-of-art tool.