[Libre-soc-bugs] [Bug 425] DIV overflow not being calculated correctly

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Fri Jul 10 02:33:11 BST 2020


--- Comment #5 from Jacob Lifshay <programmerjake at gmail.com> ---
(In reply to Jacob Lifshay from comment #4)
> (In reply to Jacob Lifshay from comment #2)
> > I ran that test after fixing some breakage from recent changes in nmigen.
> > 
> > It passed. Could you point out in more detail what's broken?
> > 
> > I ran it with:
> > python src/soc/fu/div/test/test_pipe_caller.py DivTestCase.test_6_regression
> Aha, I was using DivTestCase instead of DIVTestCase. oops

Well, I got the test to fail, the problem is either the pipeline is broken to
the point where ra and rb in DivSetupStage and lots of other places are always
0, or nmigen's simulator is broken where it writes zeros to random wires in the
.vcd file.

I'd have to figure out where to add print statements for debugging or
something, since there are so many layers of abstraction that I'm a bit lost.

I'm not really sure how to write a test case that just sets the inputs of the
pipeline to values and runs it without needing all the extra stuff for handling
instruction cancellation, matching against qemu, or matching against the model
from the Power spec.

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