Bluespec SystemVerilog: Why we need abstraction in HDLs
Dec 4, 04:33 PM
A friend of mine pointed me toward a wonderful Master’s Thesis about using Bluespec SystemVerilog (BSV) to develop an H.264 hardware video decoder. The introduction provides a clear overview of why C-based reference designs fall over for things like H.264 encoding/decoding, and the body of the paper demonstrates how to apply BSV to serious problems.
My professor in Computer Hardware Design this semester, when asked about BSV, dismissed it with something along the lines of “kids invent new HDLs all the time, but real men use VHDL or Verilog.” I’m getting the impression this is a prevalent believe in the electrical engineering world. Instead of moving forward and developing better and better tools, electrical engineers get stuck with old technology that is rarely optimal for the job. Things like BSV come along with the potential to completely change the market, but nobody notices because they’re too busy solving the same problems over and over again in lower-level languages.
Bluespec SystemVerilog provides some of the kind of abstraction I’m going for with Computer.Build. It’s a great tool, and I’m totally using it for Advanced Computer Hardware Design next semester. Unfortunately, it fall short of supporting metaprogramming. Why in the world would you want metaprogramming with hardware? For the same reasons you do it in software! Syntactic abstraction makes problem and solution definitions more concise and closer to the actual problem domain. This paper talks about exactly why this is crucial for H.264 decoding, but it applies everywhere. The C implementations just pass around huge shared memory structures, but this isn’t how the actual process of H.264 decoding works. BSV provides some great abstractions that get much closer to the problem, and for this application may be the best tool for the job.
I’m going for even more with Computer.Build, though. My goal is to allow the development of a multitude of DSLs for defining different kinds of hardware. For one-off solutions, you’re probably better off with BSV, but Computer.Build is intended to solve entire classes of problems in a manner only doable with DSLs or some other kind of language-level abstraction.
