More features ! (one day)

A project log for Libre Gates

A Libre VHDL framework for the static and dynamic analysis of mapped, gate-level circuits for FPGA and ASIC. Design For Test or nothing !

Yann Guidon / YGDESYann Guidon / YGDES 09/08/2020 at 16:400 Comments

While replying to Pat in comments in I’m Sorry Dave, You Shouldn’t Write Verilog, I realised that this little library could perform more functions, in particular "auto-pipeline" (the automatic insertion of DFF in the middle of a circuit to increase its clock speed). This requires the new function that re-exports a (modified) netlist. And from there, it's "all the way down on the slippery slope", with the possibility to modify the netlist in whatever other ways we might desire (extract a logic cone, strip DFFs to de-pipeline, you name it). It would become like a sort of sed for netlists ;-)

I don't think it will be hard to re-export a netlist, based on the depthlist. I'd love to visualise the graphs however !

Another possible funny application would be "de-synthesising" because the PA3 files contain a symbolic/algebraic representation of the boolean function of each gate, in text format ! Just substitute the operands with the net name and you get source code. So, given a netlist of gates with 3 inputs each, finding the corresponding reverse boolean function/name is quite easy and the netlist can be decompiled into a higher-level description, that is easier to read. You don't even need to know the name of the gate or function, the 8 bits of the LUT are enough (as found in some EDIF dumps), and applying permutations to the inputs will compress the 256 cases down to the known non-degenerate cases. I don't know if/how that will be useful in practice but it opens the perspective to transcode a library into another (when I'll have integrated other libraries). Can you imagine being able to port a design to another technology with a simple run of a program and not bother with the gates naming ? This means you can start your design on whatever platform you like and not being locked into it.