fifo: better testing

[anshumanmohan]

This PR adds a slightly more sophisticated testing setup for the FIFO queues.

Before

• We had a hand-written file fifo.data.
• We had a hand-written file fifo.expect.
• We had a hand-written file fifo.py: the eDSL implementation.
• On testing with runt, we'd automatically:
  • Run fifo.py to get Calyx code.
  • Run this Calyx code against fifo.data.
  • Compare the output against fifo.expect.

After

• We have a new script fifo_data_gen.py that prints pseudorandom information to populate three lists: commands, values, ans_mem. These contain the formatting info that Calyx expects, and can be piped into a file fifo.data.
• We have another new script fifo_oracle.py that:
  • Reads a .data-like thing from stdin (the .data thing will have commands, values, and ans_mem, but we care only about the first two).
  • "Runs" the FIFO program using those two lists, and collects the answer in an ans list.
  • Dumps the ans list along with the commands and values to screen, in an .expect-like format.
  • All told, this output can be piped into fifo.expect.
• The eDSL code fifo.py is unchanged.
• The testing process is the same as before; we just probably have a better .data file and a .expect file that was created by a clever oracle and not a tired grad student.

What this PR is not doing

Just to be clear, this PR is not running the Python scripts every time in any clever way. The data-generating Python script is seeded with a constant, and after some brute-force searching I've found a constant (5) that generates data that runs the queue through its paces a little. I've run the two new scripts, piped their results into fifo.data and fifo.expect, and committed those new files. The commands I ran were:

python calyx-py/calyx/fifo_data_gen.py > calyx-py/test/correctness/fifo.data

and

python calyx-py/calyx/fifo_data_gen.py | python calyx-py/calyx/fifo_oracle.py > calyx-py/test/correctness/fifo.expect

If you want to try it with new data, you'll need to change the random seed in fifo_data_gen.py, run these two scripts to clobber the .data and .expect files, and then run runt as usual.

[anshumanmohan]

@calebmkim requesting a review from you since we talked about this recently. I think this is actually a teeny bit more sophisticated that the systolic stuff, since I do have the ability to generate new "problems" for myself, and the oracle reads the new problem every time. This is as opposed to "knowing" the problem beforehand. I pipe the oracle's output to an expect file and then leave the testing of the answer to the usual runt script.

[calebmkim]

I think this all lgtm!
Doesn't have to be in this PR, but I can imagine a future version of this that allows you to set MAX_CMDS and ANS_MEM_LEN user command line inputs to the python program.