Addressing svsim dependency inversion w.r.t. build systems

[oharboe]

Looking at out unit-tests, a lot of them are tests that issue a bunch of poke + step + expect.

Is there a way to get the svsim system to output this sequence to a yaml/json file without going through elaboration?

A colleague said that these are called "sequences" in UVM.

If so, then I could set up bazel to generate the sequences and have an action that uses a small c++ program to parse these poke + step + expect yaml/json sequences in a cc_test() on elaborated + firtool + verilated modules. The C++ side would then have to read in a string and apply it to the right input pin and read/check the output pins. This is a mapping from a dynamic name in yaml/.json to a static name in C++.

Some developers might prefer to write sequences such as the above directly in .json/yaml or capture them from integration tests too.

Of couser this would not work for more complicated test-cases that use peek() to modify the control flow in the Scala unit-test or even use peek() and implement their own check, though it could be useful to log peek() for human inspection or to implement warnings in the cc_test() or statistics or some feature that my imagniantion fails to capture.

For even faster test regression execution, it would be possible to pin the test-trace artifact and only update it when the test actually changes. It is a little bit tricky to express the dependencies for the test-trace accurately: it depends on the unit-test and the test interface, not the device under test. However, svsim does capture this concept in ModuleInfo, though it is a bit unclear to me how type information is captured. Does peek/poke/expect use ModuleInfo extracted from the DUT?

        ModuleInfo(
          name = "GCD",
          ports = Seq(
            new ModuleInfo.Port(
              name = "clock",
              isSettable = true,
              isGettable = true
            ),
            new ModuleInfo.Port(
              name = "a",
              isSettable = true,
              isGettable = true
            ),

This also gives me an idea on how to address the "missing" fork/join() feature of svsim. The output of the peek poke expect could output several independent "threads" and the cc_test() woudl the launch multiple threads(or handle it in a single thread). The use-case would be to have a "thread" that is issuing transactions(Decoupled) and a separated thread that checks expected answers(Valid).