Bringing Tier -2 to Tier-1

I am planning to contribute my efforts to promote Rust support of Tier-2 platforms to Tier-1. It will be a great start if i could know what are all the gaps to be filled to achieve it ?

Although technically not accepted AFAICT, I believe the best source we have on this subject is:

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Yeah, I suspect the hardest parts would be figuring out how to make it scalable in terms of manpower. You would need to find people who are able to commit to testing and debugging issues for the platforms you wish to promote. You would also need to find a viable way for them to get access to those platforms for developing on the compiler itself.

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The main difference between Tier 2 and Tier 1, as I understand from early discussion around ARM macOS, is that Tier 2 just guarantees that the standard library (cross) compiles on (to) that architecture, and Tier 1 guarantees that all of the tests pass on that architecture.

So there's two constraints for a target to be Tier 1:

  • There needs to be CI machines available with that architecture to run the tests. This probably means some company with a CI offering sponsoring the machines required to run the CI jobs, and making sure that this is done in a way that doesn't slow down the existing long CI times.
  • There needs to be people available to fix any issues that arise with platform specific support for that architecture. If there aren't, the platform is just going to be degraded back down to "Tier 1.5" as tests get disabled on the platform because nobody is fixing them.