Fix coroutine MIR saved local remapping by dingxiangfei2009 · Pull Request #158655 · rust-lang/rust

dingxiangfei2009 · 2026-07-01T12:32:15Z

The unsound analysis was found while I was working on the async-drop code. Apparently the counter variable in the array drop glue is not correctly identified as a saved local.

Also we did not patch up indices in ProjectionElem::Index when they are saved locals.

The reproduction is in the older commit with the expected output.

rustbot · 2026-07-01T12:32:18Z

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

rustbot · 2026-07-01T12:32:21Z

r? @TaKO8Ki

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dingxiangfei2009 · 2026-07-01T12:32:47Z

r? cjgillot

who probably has more context

dingxiangfei2009 · 2026-07-03T16:15:45Z

@rustbot ready

Signed-off-by: Xiangfei Ding <dingxiangfei2009@protonmail.ch>

rustbot · 2026-07-04T19:24:19Z

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.

Storage is still required even if the local is moved out and immediately moved in again. Signed-off-by: Xiangfei Ding <dingxiangfei2009@protonmail.ch>

dingxiangfei2009 · 2026-07-06T10:54:44Z

@rustbot ready

dingxiangfei2009 · 2026-07-07T15:58:58Z

@cjgillot Thank you for your review!

I have applied the suggestions. Let me know any other outstanding concerns. Cheers!

cjgillot · 2026-07-08T01:34:04Z

Great !
@bors r+

…uwer Rollup of 18 pull requests Successful merges: - #158871 (add relnotes for 1.97.0) - #150946 (intrinsics: Add a fallback for non-const libm float functions) - #158617 (allow mGCA const arguments to fall back to anon consts) - #158645 (Fix splat ICEs and ban it in closures) - #158655 (Fix coroutine MIR saved local remapping) - #158666 (Carry the `b_offset` inside `BackendRepr::ScalarPair`) - #158920 (Update wasm-component-ld to 0.5.26) - #158926 (wrapping_sh* methods: clarify underspecified reference) - #158927 (add core test run with `-Zforce-intrinsic-fallback`) - #151379 (Stabilize `VecDeque::retain_back` from `truncate_front`) - #158807 (Add regression test for CString::clone_into unwind safety) - #158862 (Fix the span for parameter suggestion ) - #158883 (tests: fix enum-match.rs to handle LLVM 23) - #158894 (Make the ordering of non-terminal binds in ambiguity error messages deterministic) - #158902 (add codegen test for range length bound propagation) - #158913 (Update `browser-ui-test` version to `0.24.1`) - #158935 (std: support real fd methods on Emscripten) - #158951 (Merge three `MaxUniverse`s into one)

…cjgillot Fix coroutine MIR saved local remapping The unsound analysis was found while I was working on the `async-drop` code. Apparently the counter variable in the array drop glue is not correctly identified as a saved local. Also we did not patch up indices in `ProjectionElem::Index` when they are saved locals. The reproduction is in the older commit with the expected output.

…uwer Rollup of 25 pull requests Successful merges: - #158871 (add relnotes for 1.97.0) - #158968 (stdarch subtree update) - #154445 (rustdoc: Represent `--output-format=json` coverage and ir differently) - #156370 (Reject linked dylib EII default overrides) - #157153 (allow `Allocator`s to be used as `#[global_allocator]`s) - #158495 (Rename HAS_CT_PROJECTION to HAS_CONST_ALIAS) - #158617 (allow mGCA const arguments to fall back to anon consts) - #158645 (Fix splat ICEs and ban it in closures) - #158655 (Fix coroutine MIR saved local remapping) - #158666 (Carry the `b_offset` inside `BackendRepr::ScalarPair`) - #158912 (Introduce new bootstrap config section for PGO configuration) - #158920 (Update wasm-component-ld to 0.5.26) - #158926 (wrapping_sh* methods: clarify underspecified reference) - #158927 (add core test run with `-Zforce-intrinsic-fallback`) - #158932 (Do not build the compiler when invoking `x perf compare`) - #158937 (Emit the emscripten entry point as `__main_argc_argv`) - #151379 (Stabilize `VecDeque::retain_back` from `truncate_front`) - #156548 ( Library support for aarch64-unknown-linux-pauthtest target) - #158307 (CI job for parallel frontend ui tests) - #158347 (Improve generic parameters handling for #[diagnostic::on_const]) - #158722 (delegation: do not always inherit `ConstArgHasType` predicates) - #158741 (Simplify `Option::into_flat_iter` signature) - #158807 (Add regression test for CString::clone_into unwind safety) - #158862 (Fix the span for parameter suggestion ) - #158883 (tests: fix enum-match.rs to handle LLVM 23)

…cjgillot Fix coroutine MIR saved local remapping The unsound analysis was found while I was working on the `async-drop` code. Apparently the counter variable in the array drop glue is not correctly identified as a saved local. Also we did not patch up indices in `ProjectionElem::Index` when they are saved locals. The reproduction is in the older commit with the expected output.

Rollup of 25 pull requests Successful merges: - #158871 (add relnotes for 1.97.0) - #158968 (stdarch subtree update) - #157690 (codegen_ssa: pack small const aggregates into immediate stores) - #158541 (Move `std::io::Write` to `core::io`) - #154445 (rustdoc: Represent `--output-format=json` coverage and ir differently) - #156370 (Reject linked dylib EII default overrides) - #157153 (allow `Allocator`s to be used as `#[global_allocator]`s) - #158495 (Rename HAS_CT_PROJECTION to HAS_CONST_ALIAS) - #158617 (allow mGCA const arguments to fall back to anon consts) - #158645 (Fix splat ICEs and ban it in closures) - #158655 (Fix coroutine MIR saved local remapping) - #158666 (Carry the `b_offset` inside `BackendRepr::ScalarPair`) - #158870 (std: merge the unix-like io::error modules into one file) - #158920 (Update wasm-component-ld to 0.5.26) - #158926 (wrapping_sh* methods: clarify underspecified reference) - #158927 (add core test run with `-Zforce-intrinsic-fallback`) - #158932 (Do not build the compiler when invoking `x perf compare`) - #158937 (Emit the emscripten entry point as `__main_argc_argv`) - #151379 (Stabilize `VecDeque::retain_back` from `truncate_front`) - #156144 (Better docs for PartialEq (includes macro rename)) - #156548 ( Library support for aarch64-unknown-linux-pauthtest target) - #158307 (CI job for parallel frontend ui tests) - #158347 (Improve generic parameters handling for #[diagnostic::on_const]) - #158722 (delegation: do not always inherit `ConstArgHasType` predicates) - #158741 (Simplify `Option::into_flat_iter` signature)

jhpratt · 2026-07-09T00:51:21Z

I think this may be the cause of #158986 (comment), but I'm not certain.

@bors try jobs=aarch64-gnu-debug

@bors r-

Fix coroutine MIR saved local remapping try-job: aarch64-gnu-debug

rust-bors · 2026-07-09T00:51:31Z

This pull request was unapproved.

This PR was contained in a rollup (#158986), which was unapproved.

View changes since this unapproval

rust-bors · 2026-07-09T02:11:00Z

☀️ Try build successful (CI)
Build commit: fea2ff1 (fea2ff15d501ff090e07e8b8e0e3923a45526ac9)
Base parent: 14cae68 (14cae681329a63c622a6e1fbe1d30f9374bc51d8)

dingxiangfei2009 · 2026-07-11T09:27:02Z

@bors try

Fix coroutine MIR saved local remapping

rust-bors · 2026-07-11T11:37:05Z

☀️ Try build successful (CI)
Build commit: 47885b7 (47885b7d3a2f833e136633bcfcf7622f33f1004b)
Base parent: ad49852 (ad49852b6f3dd9c1c73fe909d8843bb7e464b387)

dingxiangfei2009 · 2026-07-11T15:31:46Z

@bors try jobs=aarch64-gnu-debug

rust-bors · 2026-07-11T15:31:49Z

Unknown command "jobs". Run @bors help or go to https://bors.rust-lang.org/help to see available commands.

dingxiangfei2009 · 2026-07-11T15:32:13Z

@bors try jobs=aarch64-gnu-debug

Fix coroutine MIR saved local remapping try-job: aarch64-gnu-debug

rust-bors · 2026-07-11T16:46:07Z

☀️ Try build successful (CI)
Build commit: 5f08f47 (5f08f47e109fef96c446a1db4e145e1e70bc4d71)
Base parent: acf6a00 (acf6a00aff5d8aa8892aadff0b48364b50f97cf4)

dingxiangfei2009 · 2026-07-11T16:53:48Z

@jhpratt Okay it looks like the previous failure was due to another PR in the rollup.

Shall we proceed?

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jul 1, 2026

rustbot assigned TaKO8Ki Jul 1, 2026

rustbot assigned cjgillot and unassigned TaKO8Ki Jul 1, 2026

dingxiangfei2009 requested a review from cjgillot July 1, 2026 12:33

cjgillot reviewed Jul 1, 2026

View reviewed changes

Comment thread compiler/rustc_mir_transform/src/coroutine/mod.rs Outdated

Comment thread compiler/rustc_mir_transform/src/coroutine/mod.rs Outdated

Comment thread tests/ui/async-await/async-drop/async-drop-initial.rs

cjgillot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 2, 2026

dingxiangfei2009 force-pushed the fix-remapping branch from f809a69 to fd23727 Compare July 3, 2026 07:55

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 3, 2026

cjgillot reviewed Jul 3, 2026

View reviewed changes

reproduction of miscompilation

9566dad

Signed-off-by: Xiangfei Ding <dingxiangfei2009@protonmail.ch>

dingxiangfei2009 force-pushed the fix-remapping branch from fd23727 to aa485b2 Compare July 4, 2026 19:24

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dingxiangfei2009 force-pushed the fix-remapping branch from aa485b2 to bb63725 Compare July 6, 2026 05:19

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dingxiangfei2009 force-pushed the fix-remapping branch from bb63725 to 81a734f Compare July 6, 2026 06:45

fix remapping in indexing and self-assignments

401dc21

Storage is still required even if the local is moved out and immediately moved in again. Signed-off-by: Xiangfei Ding <dingxiangfei2009@protonmail.ch>

dingxiangfei2009 force-pushed the fix-remapping branch from 81a734f to 401dc21 Compare July 6, 2026 06:46

dingxiangfei2009 requested a review from cjgillot July 6, 2026 10:54

JonathanBrouwer mentioned this pull request Jul 8, 2026

Rollup of 18 pull requests #158958

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JonathanBrouwer mentioned this pull request Jul 8, 2026

Rollup of 25 pull requests #158973

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JonathanBrouwer mentioned this pull request Jul 8, 2026

Rollup of 25 pull requests #158977

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jhpratt mentioned this pull request Jul 8, 2026

Rollup of 25 pull requests #158986

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rust-bors Bot pushed a commit that referenced this pull request Jul 9, 2026

Auto merge of #158655 - dingxiangfei2009:fix-remapping, r=<try>

fea2ff1

Fix coroutine MIR saved local remapping try-job: aarch64-gnu-debug

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rust-bors Bot pushed a commit that referenced this pull request Jul 11, 2026

Auto merge of #158655 - dingxiangfei2009:fix-remapping, r=<try>

47885b7

Fix coroutine MIR saved local remapping

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rust-bors Bot pushed a commit that referenced this pull request Jul 11, 2026

Auto merge of #158655 - dingxiangfei2009:fix-remapping, r=<try>

5f08f47

Fix coroutine MIR saved local remapping try-job: aarch64-gnu-debug

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