[myhdl-list] supported operators for Signal class

[David S. <dst...@kc...>]

I'm trying some tests converting python code to MyHDL code that generates real hardware. As a hardware designer, I know some of these tests are going to be foolish first steps to make, but I also know that less experienced designers might make these same mistakes. Here's a simplified code block

    x, y = [Signal(intbv(1)[64:]) for i in range(2)]
    @always_seq(clk.posedge, reset)
    def test_divide():
        y.next = y / x

    return test_divide

and here's the error message I get:

    y.next = y / x
TypeError: unsupported operand type(s) for /: '_Signal' and '_Signal'


Which leads to the question, what operand types ARE supported for Signals? This feels like an obvious question, but I can't seem to find an answer anywhere in the documentation.

When I change the code to be

y.next = y ** x

I was surprised to get a different error message:

  File "/home/dstanford/.local/lib/python2.7/site-packages/myhdl/conversion/_toVHDL.py", line 171, in __call__
    _annotateTypes(genlist)
  File "/home/dstanford/.local/lib/python2.7/site-packages/myhdl/conversion/_toVHDL.py", line 2288, in _annotateTypes
    v.visit(tree)
  File "/usr/lib/python2.7/ast.py", line 241, in visit
    return visitor(node)
  File "/usr/lib/python2.7/ast.py", line 249, in generic_visit
    self.visit(item)
  File "/usr/lib/python2.7/ast.py", line 241, in visit
    return visitor(node)
  File "/home/dstanford/.local/lib/python2.7/site-packages/myhdl/conversion/_toVHDL.py", line 2029, in visit_FunctionDef
    self.visit(stmt)
  File "/usr/lib/python2.7/ast.py", line 241, in visit
    return visitor(node)
  File "/usr/lib/python2.7/ast.py", line 251, in generic_visit
    self.visit(value)
  File "/usr/lib/python2.7/ast.py", line 241, in visit
    return visitor(node)
  File "/home/dstanford/.local/lib/python2.7/site-packages/myhdl/conversion/_toVHDL.py", line 2137, in visit_BinOp
    self.inferBinOpType(node)
  File "/home/dstanford/.local/lib/python2.7/site-packages/myhdl/conversion/_toVHDL.py", line 2175, in inferBinOpType
    raise AssertionError("unexpected op %s" % op)
AssertionError: unexpected op <_ast.Pow object at 0x7fa74b0e3350>

And finally going through a list of basic python operators I tried out

y.next = y // x

which works, and makes sense though I didn't even know it was an option until I was trying this test out.

Am I searching poorly looking for a list of operators that works between signals, or does such a table not exist? Should it?

Thanks,

Dave Stanford


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