Modular Hardware Design with Timeline Types

Modular design is a key challenge for enabling large-scale reuse of hardware modules. Unlike software, however, hardware designs correspond to physical circuits and inherit constraints from them. Timing constraints -- which cycle a signal arrives, when an input is read -- and structural constraints -- how often a multiplier accepts new inputs -- are fundamental to hardware interfaces. Existing hardware design languages do not provide a way to encode these constraints; a user must read documentation, build scripts, or in the worst case, a module's implementation to understand how to use it. We present Filament, a language for modular hardware design that supports the specification and enforcement of timing and structural constraints for statically scheduled pipelines. Filament uses timeline types, which describe the intervals of clock-cycle time when a given signal is available or required. Filament enables safe composition of hardware modules, ensures that the resulting designs are correctly pipelined, and predictably lowers them to efficient hardware.Comment: Extended version of PLDI '23 pape

Domain Specific Computing in Tightly-Coupled Heterogeneous Systems

Over the past several decades, researchers and programmers across many disciplines have relied on Moores law and Dennard scaling for increases in compute capability in modern processors. However, recent data suggest that the number of transistors per square inch on integrated circuits is losing pace with Moores laws projection due to the breakdown of Dennard scaling at smaller semiconductor process nodes. This has signaled the beginning of a new “golden age in computer architecture” in which the paradigm will be shifted from improving traditional processor performance for general tasks to architecting hardware that executes a class of applications in a high-performing manner. This shift will be paved, in part, by making compute systems more heterogeneous and investigating domain specific architectures. However, the notion of domain specific architectures raises many research questions. Specifically, what constitutes a domain? How does one architect hardware for a specific domain? In this dissertation, we present our work towards domain specific computing. We start by constructing a guiding definition for our target domain and then creating a benchmark suite of applications based on our domain definition. We then use quantitative metrics from the literature to characterize our domain in order to gain insights regarding what would be most beneficial in hardware targeted specifically for the domain. From the characterization, we learn that data movement is a particularly salient aspect of our domain. Motivated by this fact, we evaluate our target platform, the Intel HARPv2 CPU+FPGA system, for architecting domain specific hardware through a portability and performance evaluation. To guide the creation of domain specific hardware for this platform, we create a novel tool to quantify spatial and temporal locality. We apply this tool to our benchmark suite and use the generated outputs as features to an unsupervised clustering algorithm. We posit that the resulting clusters represent sub-domains within our originally specified domain; specifically, these clusters inform whether a kernel of computation should be designed as a widely vectorized or deeply pipelined compute unit. Using the lessons learned from the domain characterization and hardware platform evaluation, we outline our process of designing hardware for our domain, and empirically verify that our prediction regarding a wide or deep kernel implementation is correct

Proceedings of the 22nd Conference on Formal Methods in Computer-Aided Design – FMCAD 2022

The Conference on Formal Methods in Computer-Aided Design (FMCAD) is an annual conference on the theory and applications of formal methods in hardware and system verification. FMCAD provides a leading forum to researchers in academia and industry for presenting and discussing groundbreaking methods, technologies, theoretical results, and tools for reasoning formally about computing systems. FMCAD covers formal aspects of computer-aided system design including verification, specification, synthesis, and testing

Proceedings of the 22nd Conference on Formal Methods in Computer-Aided Design – FMCAD 2022

The Conference on Formal Methods in Computer-Aided Design (FMCAD) is an annual conference on the theory and applications of formal methods in hardware and system verification. FMCAD provides a leading forum to researchers in academia and industry for presenting and discussing groundbreaking methods, technologies, theoretical results, and tools for reasoning formally about computing systems. FMCAD covers formal aspects of computer-aided system design including verification, specification, synthesis, and testing