Promote armv8r-none-eabihf to Tier 2

[thejpster]

Proposal

I would like to promote armv8r-none-eabihf to Tier 2, joining armv7r-none-eabi, armv7r-none-eabihf and armv7a-none-eabi. It's the target for using the Cortex-R52 processor, which is turning up in increasing numbers of SoCs - often as a Safety Island alongside a cluster of Cortex-A cores. Armv8-R AArch32 changes the FPU type as compared to Armv7-R AArch32. It also introduces Hypervisor support with an EL2 level, which was seen in Armv7-A but not in Armv7-R. It therefore warrants its own target.

The armv8r-none-eabihf target has been at Tier 3 since February 2024 and is tested in https://github.com/rust-embedded/cortex-ar.

Process

The main points of the Major Change Process are as follows:

• File an issue describing the proposal.
• A compiler team member who is knowledgeable in the area can second by writing @rustbot second or kickoff a team FCP with @rfcbot fcp $RESOLUTION.
  • Refer to Proposals, Approvals and Stabilization docs for when a second is sufficient, or when a full team FCP is required.
• Once an MCP is seconded, the Final Comment Period begins.
  • Final Comment Period lasts for 10 days after all outstanding concerns are solved.
  • Outstanding concerns will block the Final Comment Period from finishing. Once all concerns are resolved, the 10 day countdown is restarted.
  • If no concerns are raised after 10 days since the resolution of the last outstanding concern, the MCP is considered approved.

You can read more about Major Change Proposals on forge.

[rustbot]

Important

This issue is not meant to be used for technical discussion. There is a Zulip stream for that.
Use this issue to leave procedural comments, such as volunteering to review, indicating that you second the proposal (or third, etc), or raising a concern that you would like to be addressed.

Concerns or objections can formally be registered here by adding a comment.

@rustbot concern reason-for-concern
<description of the concern>

Concerns can be lifted with:

@rustbot resolve reason-for-concern

See documentation at https://forge.rust-lang.org

cc @rust-lang/compiler

[davidtwco]

Compliance with target tier policy is documented in rust-lang/rust#146520 so starting an FCP to approve this per our target approvals docs.

@rfcbot fcp merge

[rust-rfcbot]

Team member @davidtwco has proposed to merge this. The next step is review by the rest of the tagged team members:

• @Mark-Simulacrum
• @Noratrieb
• @SparrowLii
• @cjgillot
• @compiler-errors
• @davidtwco
• @estebank
• @jieyouxu
• @matthewjasper
• @nagisa
• @oli-obk
• @petrochenkov
• @spastorino
• @wesleywiser

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

[rust-rfcbot]

🔔 This is now entering its final comment period, as per the review above. 🔔