This MEP is intended to add support for top-level methods in conversion. Using classes/objects to organize digital hardware can be a natural and a useful development approach for complex and modular IP.
In the latest release version, 0.7, top-level methods are not
convertible because the object reference (
self) is treated
as a port. For top-level methods to be convertible the object
self) needs to be ignored.
Example (existing function conversion)
MyHDL converts MyHDL functions, which represent a hardware module, to Verilog and VHDL. For a function to be convertible it needs ports and to return a MyHDL generator(s). The converter code identifies the arguments of Signal type and adds them to the port list.
The following is an example of a converitble function.
def adder(x, y, z): @always_comb def logic(): z.next = x + y return logic
>>> toVerilog(adder, x, y, z) >>> toVHDL(adder, x, y, z)
As mentioned the enhancement proposed is to add top-level method conversion support. The method to be converted has the same requirements as a function: it needs a ports and returns a generator(s).
Using the brief examples above a top-level convertible method might look like the following:
class Adder(): def __init__(self): pass def m_adder(self, x, y, z): @always_comb def logic(): z.next = x + y return logic
The above example isn't a good example why a class would be used to create, what is often consider a piece of IP, but it is sufficient as an example for method conversion.
To convert the method in the Adder object the convertible method is passed to the conversion functions.
>>> MyAddr = Adder() >>> toVerilog(MyAddr.m_adder, x, y, z) >>> toVHDL(MyAddr.m_adder, x, y, z)
In the above example and with the existing (0.7) conversion code the
self argument in the "m_adder" method will be converted to a
port in the lower-level Verilog/VHDL.
Top Function Visitor
The use of the
self argument, is only an issue for the
top-level method parsing. This is because the parser flattens
the design and the ports are not analyzed for functions and methods
lower in the hierarchy.
In the above node visitor a method is identified and the first argument is skipped.
is modified to identify the methods
that describe hardware and determine if conversion
function/method attributes are present. The extractor
checks for an argument named
self and retrieves the function
self. If a function is bound to
self the extractor
will use it in the extract hierarchy.