Re: [Iverilog-devel] How to get gate count and delay for a (combinatorial) circuit?

[Stephen W. <st...@ic...>]

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Humm, the sizer target is only available in the git repository,
in the master branch:-( It may be time to make a snapshot.

On 11/09/2014 05:20 AM, Niels Möller wrote:
> Stephen Williams <st...@ic...> writes:
> 
>> The only accurate gate count fron synthesis is go get the gate
>> count from the synthesizer that you are using to targetting your
>> device. For FPGAs, that will be the vendor supplied synthesizer.
> 
> I think I'm more interested in a rough gate count for an asic 
> implementation, than resources used in any particular fpga.
> 
>> That said, you can use the "-tsizer" target to Icarus Verilog to 
>> get a very (VERY!) rough estimate of gate counts. This is really 
>> only useful for relative comparisons (i.e. "Did my last change 
>> cause a lot of new resources to be required?").
> 
> I think my use will be to (i) get a feeling for the relative
> complexity of different parts of a cpu, and (ii) compare different
> implementations of the same interface.
> 
> But how do I use this target? I'm trying as follows,
> 
> ~/hack/instr16/hw$ iverilog -tsizer -s add_bk8 add-bk8.vl
> add-gp.vl ERROR: Unable to read config file:
> /usr/lib/ivl/sizer.conf : error: target_design entry point is
> missing. error: Code generator failure: -2
> 
> add-bk8.vl defines a moule add_bk8, implementing an 8-bit
> Brent-Kung adder. Which is my intended "top-level" circuit.
> add-gp.vl is a helper module to combine two sets of
> generate/propagate signals, instantiated multiple times in
> add-bk8.vl.
> 
> And what about gate delay, can I get that for selected
> input/output pairs? I guess it's possible to try synthesis using
> iverilog or yosys and then do postprocessing of the generated
> netlist, but I was hoping for something simpler...
> 
> Regards, /Niels
> 


- -- 
Steve Williams                "The woods are lovely, dark and deep.
steve at icarus.com           But I have promises to keep,
http://www.icarus.com         and lines to code before I sleep,
http://www.picturel.com       And lines to code before I sleep."
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