Not sure I'd call it an Icarus bug, but ok, great that it works now. Built-in sim is only for pure migen designs, right?
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Imo this is a two-part problem: (1) a netlist format and (2) a standard cell library. The "industry solutions" would be EDIF and LPM. Both not very convincing solutions imo.
Netlist formats are all very easy to convert losslessly. Cell libraries (we are talking parameterized coarse grain cells here) aren't always. But for example Yosys RTLIL and Chisel FIRRTL are surprisingly similar in this regard.