Support multiple same table invocations in pipeline

[antoninbas]

P4_16 has no limitation on how many times the same table can be applied. Right now this is not supported by bmv2 (except potentially some very specific cases) because the JSON representation for P4 controls (as a table graph whose edges are actions) doesn't support it.

[antoninbas]

See p4lang/p4c#457 for detailed description.

[qobilidop]

Is anyone working on solving this? If not, I'd like to have a try.

[antoninbas]

You are welcome to give it a go. However, for the sake of setting expectations, please be aware that it is not a trivial task:

• the schema of the JSON file consumed by bmv2 needs to be extended, while ensuring backwards-compatibility (i.e., old JSON files should keep working)
• bmv2 itself needs to be updated to support this
• the p4c bmv2 backend needs to be updated to support this

[qobilidop]

Understood. Thanks for the information. I'll see how far I can go on this.