Add Vivado power optimization option flag

[sebinho]

This proposal adds a flag to enable power optimization during implementation stage of a Vivado run.
Power optimization can have huge impacts, especially when using a device that has a PS (Processing System).

To use this new option, simply add the following flag in your *.core file:

flow_options :
            part           : xczu3eg-sfvc784-1-e
            power_opt      : 1

If set to 0, it will disable the power optimizations (and also if the options is not specified at all)

[sebinho]

So on my setup, it works well when using the FLOW approach.
I am not sure why I get those checks failures. Maybe @olofk can help explaining why this fails?

Thanks

[olofk]

Generally, we try to avoid adding explicit options when there are other ways to accomplish the same thing. The reason for that is there would otherwise be a million different flags which adds complexity. Instead, I propose doing the following:

Create a TCL file which contains set_property strategy Power_DefaultOpt [get_runs impl_1] and add that to a fileset with file_type : tclSource. Just tried that on a design and it seems to do the trick, but I don't have a good way to verify.

[sebinho]

Thanks for the suggestion @olofk
I tried and it does indeed work as expected.

My only comment would be to say that the Vivado implementation step power_opt_design is quite common and one of the steps used very often. So I think it could be a good idea to somehow integrate this in the flow.
I know that Vivado has tons of flags that can be set, but this one seems like a big one.

Anyways, thanks a lot for your help.

[olofk]

I understand your point, but one reflection I have made over the 12 years I have been working on this is that people are using these tools in such incredibly different ways. Things I thought everyone was doing turned out to of little use to others. We also used to have some assumptions built in that turned out to break code for others. That would not happen in this case, but it's the general reason why I am knowingly keeping things as lean as possible

[sebinho]

I get your point. For sure there are many ways to look at it and different people will have different approaches and will use different parameters.
Thanks for being responsive, for the time being I will close the pull request to get this out of your hair.