Add support for magma.Tuple to be a top level port

[rsetaluri]

import magma as m

class Foo(m.Circuit):
    IO = ["IFC", m.Tuple(I=m.In(m.Bit), O=m.Out(m.Bit))]

    @classmethod
    def definition(io):
        pass

if __name__ == "__main__":
    m.compile("foo", Foo, output="coreir")
    print (open("foo.json").read())

The above fails in the compile() call. The same holds for output=verilog but that's simply because magma.Tuple is simply not allowed in a verilog module declaration.

[rsetaluri]

The underlying issue seems to be that magma top level ports need to have isinput() or isoutput() == True in the core ir backend.

[phanrahan]

Currently magma modules can only have type Bit or Bits. Tuples or more general arrays are not supported.

[leonardt]

We should be able to support this in the coreir backend. The verilog backend doesn't have support for basic Tuples yet, so this definitely won't work for that.

[rsetaluri]

import magma as m

class Foo(m.Circuit):
    IO = ["I", m.In(m.Tuple(a=m.Bit, b=m.Bit)), "O", m.Out(m.Tuple(a=m.Bit, b=m.Bit))]

    @classmethod
    def definition(io):
        pass

if __name__ == "__main__":
    m.compile("foo", Foo, output="coreir")
    print (open("foo.json").read())

To be clear the above does work because the top level types are In/Out.

[rsetaluri]

@phanrahan: Is this true? I think Tuples and Arrays seem to be mostly working for the CoreIR backend. If it is the case, what is the purpose of these types? Just for internal use?

@leonardt: understood.

[phanrahan]

The intention is to support all types in module interfaces.

[leonardt]

Support for more complex arrays (e.g. nested) and tuples in the verilog backend require flattening the types to normal verilog types (1-D arrays, wire). We haven't added that yet since we wanted to be careful about how to do this right since it requires munging names. Coreir has built-in support for those types so we can support it, and the corier-verilog backend has implemented name munging for generating those types.

[rsetaluri]

To provide some more context:

import magma as m

foo = m.DefineCircuit("Foo", "ifc", m.Tuple(I=m.In(m.Bit), O=m.Out(m.Bit)))
m.wire(foo.ifc.I, foo.ifc.O)
m.EndCircuit()

m.compile("foo", foo, output="coreir")

This errors in compilation. I gave a shot at adding support for this but I noticed several things that needed to change (including that #260 was causing oddities in directionality in interface vs IO).

The expected CoreIR is:

{"top":"global.Foo",
"namespaces":{
  "global":{
    "modules":{
      "Foo":{
        "type":["Record",[
          ["ifc",["Record",[["I","BitIn"],["O","Bit"]]]]
        ]],
        "connections":[
          ["self.ifc.I", "self.ifc.O"]
        ]
      }
    }
  }
}
}

[rsetaluri]

Noticed something that doesn't work:

>>> T = Array(10, Tuple(I=In(Bit), O=Out(Bit)))
>>> Foo = magma.DefineCircuit("Foo", "IFC", T)
>>> for i in range(10):
...     wire(Foo.IFC[i].I, Foo.IFC[i].O)
... 
>>> EndCircuit()
>>> compile("foo", Foo, output="coreir")
>>>
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/setaluri/dev/magma/magma/compile.py", line 110, in compile
    __compile_to_coreir(main, file_name, opts)
  File "/Users/setaluri/dev/magma/magma/compile.py", line 66, in __compile_to_coreir
    backend.compile(main)
  File "/Users/setaluri/dev/magma/magma/backend/coreir_.py", line 400, in compile
    self.modules[defn.name] = self.compile_definition(defn)
  File "/Users/setaluri/dev/magma/magma/backend/coreir_.py", line 291, in compile_definition
    module_type = self.convert_interface_to_module_type(definition.interface)
  File "/Users/setaluri/dev/magma/magma/backend/coreir_.py", line 183, in convert_interface_to_module_type
    raise NotImplementedError()
NotImplementedError

Looking at the code at line 183: https://github.com/phanrahan/magma/blob/f84457fc125bd54751b5c0ad5fd450255eec91c8/magma/backend/coreir_.py#L178-L185

We always assert that a type is an In or an Out when converting interfaces -- unless the type is Tuple. With nesting however, this breaks down. Not sure what the right thing to do here is, because we want to make sure that everything has a direction at it's base level (e.g. all members of a tuple). Perhaps something like this?

def is_directed(T):
    if isinstance(T, magma.BitKind):
        return T.isinput() or T.isoutput()
    if isinstance(T, magma.ArrayKind):
        return all([is_directed(t) for t in T.Ts])
    if isinstance(T, magma.TupleKind):
        return all([is_directed(t) for t in T.Ts])
    raise NotImplementedError(T)

[leonardt]

Fixed by https://github.com/phanrahan/magma/pull/274, basically the logic to handle mixed direction children was already there, just only used for Tuples. Anytime that it checked if it was a tuple that could have mixed direction children, it now checks if it's an array that could have mixed direction children.

[phanrahan]

Looking at the source, I would think this should work:

def is_directed(T):
    return T.isinput() or T.isoutput()