Define "initial entries" for P4 tables, in addition to currently defined "const entries"

[jafingerhut]

Personnel

• Owner: @jafingerhut
• Supporters: @thantry

Design

• Document: https://docs.google.com/presentation/d/1GW-9FDtyLuwqV_mdGeDh_qqDiey0VkQ1/edit?usp=sharing&ouid=113165450274035133953&rtpof=true&sd=true

Implementation

• p4-spec: There are at least two different proposed syntaxes in two different PRs (1) Add definition of initial table entries, without const qualifier #1180 (2) Add definition of initial table entries, without const qualifier #1231 For a summary of differences see here Add definition of initial table entries, without const qualifier #1180 (comment) At the 2023-May-01 LDWG meeting, there was general agreement preferring the backwards-compatible syntax extension decribed in Add definition of initial table entries, without const qualifier #1180 over Add definition of initial table entries, without const qualifier #1231
• p4c: Step 1 of implementation, adding only the new parts of the grammar Implement support for non-const table entries p4c#3748
• p4c: Step 2 of implementation, generating correct P4Info file generated by p4c: Minor fix-ups to support for tables with initial entries and their P4Runtime API output files p4c#4016 (must wait until P4 API work group approves how this feature is represented in P4Runtime API)

Process

• LDWG discussed: October 2022: https://docs.google.com/document/d/1XSgdXeG1UuF1FM_XAqxDrHeN4dHZWBnJPKVS6SnGNwM/edit#heading=h.37p6wudxij34
• LDWG approved: Discussed last at 2023-May-01 LDWG meeting, and PR Add definition of initial table entries, without const qualifier #1180 version was preferred over the alternative Add definition of initial table entries, without const qualifier #1231
• Merged into p4-spec: This PR was merged on 2023-May-15: Add definition of initial table entries, without const qualifier #1180
• Merged into p4c:

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[jafingerhut]

The language spec changes have been merged in and released as part of v1.2.4 of the spec in 2023-May. Leaving this issue open to track the implementation in open source p4c front end, which is not complete as of this writing on 2023-May-18.

[mihaibudiu]

p4lang/p4c#3748 is the proof-of-concept, I will finalize it based on the accepted syntax.

[jnfoster]

Closing as the P4C PR has also been merged.