Offload safe mutable args with `Region` and `PartitioningStrategy` by Sa4dUs · Pull Request #158076 · rust-lang/rust

Sa4dUs · 2026-06-18T10:29:32Z

Now Region are lang items and mapped as slices.
~~needs #156620 to work~~

ZuseZ4 · 2026-09-05T22:13:10Z

Next round. I think we should actually refuse all cases (for now) where we have a Region within any ADT/struct/slice, etc. not just &Region. Most of them would be transfered incorrectly, and I don't think we gain much. The other direction is something like Region<Vec<f32>, S>, where we also transfer T incorrectly. But to be fair, I think that direction is already unchecked on main. I assume that offloading a vec will still do the wrong thing, so I'm fine if we accept that here as well till we implement a proper handling. But also feel free to already reject it already if you want.

ZuseZ4

I left another round, mostly about comments and tightening the checks.
I feel like we'll need to restrict get and get_mut a bit further (or at least describe them better), but we can leave that for the last round (and discuss on Wednesday).

Now that it seems closer to the final version, can you add a description to
https://rustc-dev-guide.rust-lang.org/offload/internals.html ?
Probably best as a new subsection, so that we have one about the build pipeline, and one about the safety/region design?

View changes since this review

rustbot · 2026-09-21T14:14:09Z

The rustc-dev-guide subtree was changed. If your future PRs only touch the subtree, consider submitting them directly to rust-lang/rustc-dev-guide, which is where the document is primarily maintained (and has faster CI).

cc @BoxyUwU, @tshepang

rustbot · 2026-09-23T17:35:48Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

ZuseZ4 · 2026-10-21T19:07:40Z

The intrinsic bypasses the safety checks but I think that's fine and actually good for experimenting. End-users shouldn't call our intrinsics anyway, and use the safe macro.

The number of tests looks good now, real uses are in our rajaperf implementation. We should talk in the next PR about how many of those usages we want to upstream, and might need to iterate on this implementation if we find memory access patterns that we can't safely wrap.

I also think we should generate noalias annotations for those NonNull pointers, but that's too tricky for this PR.

It's also inconvenient that we have to error for the args are not a tuple literal, but stored in a variable. I think oli had a prototype that allowed type-checking macro args, so we might be able to use that in the future.

@bors r+ rollup

rust-bors · 2026-10-21T19:07:44Z

📌 Commit fd0ae52 has been approved by ZuseZ4

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 5. This pull request will be tested once the tree is reopened.

Reason for tree closure: github outage

…uwer Rollup of 6 pull requests Successful merges: - #164383 (handle higher-ranked preds in imperfect derives diagnostic) - #164620 (Wrap expected_ty for cfi-{diag,recover} in with_no_trimmed_paths) - #164684 (Remove redundant `PartialOrd` chaining methods) - #158076 (Offload safe mutable args with `Region` and `PartitioningStrategy`) - #164680 (Add regression test for async fn declared with #[eii]) - #164696 (Add `#[default]` for `newtype_index!`)

@ZuseZ4

Rollup merge of #158076 - Sa4dUs:offload-region, r=ZuseZ4 Offload safe mutable args with `Region` and `PartitioningStrategy` Now `Region` are lang items and mapped as slices. ~needs #156620 to work~ r? @ZuseZ4

rustbot assigned ZuseZ4 Jun 18, 2026

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jun 18, 2026