Enable R2R precompilation of blittable ObjC P/Invokes by davidnguyen-tech · Pull Request #124770 · dotnet/runtime

davidnguyen-tech · 2026-02-23T22:47:33Z

Description

Enables ReadyToRun precompilation of blittable objc_msgSend-family P/Invokes on Apple platforms. The R2R-emitted stub now calls a managed ObjectiveCMarshal.ThrowPendingExceptionObject() helper right after the native call, so ObjC P/Invokes no longer have to fall back to JIT/interpreter for the pending-exception check.

Changes

Adds ObjectiveCMarshal.ThrowPendingExceptionObject() in CoreLib and exposes it to the runtime binder via corelib.h.
R2R PInvokeILEmitter emits a call to that helper for ObjC P/Invokes, spilling the native return value across the call so the IL evaluation stack is empty at the helper site.
Marshaller.ReadyToRun no longer rejects ObjC P/Invokes, and PInvokeILStubMethodIL.IsMarshallingRequired is the single place that gates the ObjC pending-exception check.
ReadyToRunCodegenCompilation pre-registers ObjectiveCMarshal / ThrowPendingExceptionObject references with the manifest before fixup emission, mirroring the existing AddNecessaryAsyncReferences pattern. Required in non-composite mode (the default on iOS), where CoreLib is an external reference and would otherwise get rejected as out-of-bubble.
New R2R test src/tests/readytorun/ObjCPInvokeR2R/ asserts both that the stubs land in the crossgen2 .map (MethodWithGCInfo) and that the pending-exception path actually executes by hijacking MessageSendFunction.MsgSend with a managed callback.

Impact

Synthetic ObjC P/Invoke benchmark on osx-arm64 Release: a console host invokes 100 distinct blittable objc_msgSend P/Invokes per iteration.

Metric	Base	With PR	Delta
Total time for 100 ObjC P/Invoke calls	7.728 ms	1.961 ms	-5.77 ms (-75%)
Time spent JIT'ing the P/Invoke stubs	5.163 ms	4.031 ms	-1.13 ms (-22%)
P/Invoke stubs AOT-compiled into R2R	0 / 100	100 / 100	+100

MAUI template app on device doesn't provide measurable improvements because ObjC P/Invokes on the MAUI startup path are not the dominant cost.

Copilot

Pull request overview

Enables ReadyToRun (R2R) precompilation of Objective-C objc_msgSend-family P/Invoke stubs by emitting a managed pending-exception check after the native call, avoiding a runtime-stub/interpreter fallback on JIT-less Apple platforms.

Changes:

Add ObjectiveCMarshal.ThrowPendingExceptionObject() in CoreCLR and expose it to the runtime binder.
Update the R2R PInvokeILEmitter to emit a post-call pending-exception check instead of rejecting ObjC P/Invokes.
Adjust R2R compilation policy and IL caching behavior to allow ObjC P/Invokes to be attempted and to gracefully fall back when unsupported.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/coreclr/vm/corelib.h	Adds CoreLib binder entry for `ObjectiveCMarshal.ThrowPendingExceptionObject`.
src/coreclr/tools/aot/ILCompiler.ReadyToRun/JitInterface/CorInfoImpl.ReadyToRun.cs	Simplifies P/Invoke stub IL retrieval logic now that unsupported cases are handled/cached in ILCache.
src/coreclr/tools/aot/ILCompiler.ReadyToRun/IL/Stubs/PInvokeILEmitter.cs	Emits `ThrowPendingExceptionObject` after ObjC native calls; removes ObjC-specific `NotSupportedException`.
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/ReadyToRunCompilationModuleGroupBase.cs	Allows `GeneratesPInvoke` for ObjC msgSend P/Invokes even when marshalling is otherwise considered required.
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/ReadyToRunCodegenCompilation.cs	Caches “requires runtime JIT” decisions for unsupported P/Invoke stub emission via `RequiresRuntimeJitException` catch.
src/coreclr/System.Private.CoreLib/src/System/Runtime/InteropServices/ObjectiveCMarshal.CoreCLR.cs	Implements `ThrowPendingExceptionObject()` using pending-exception storage and `ExceptionDispatchInfo.Throw`.

dotnet-policy-service · 2026-02-23T22:59:12Z

Tagging subscribers to 'os-ios': @vitek-karas, @kotlarmilos, @steveisok, @akoeplinger
See info in area-owners.md if you want to be subscribed.

BrzVlad · 2026-02-24T07:38:31Z

Were there also any interpreted pinvokes with non-blittable types ? In case we might need additional fixes, related to the original plan of using LibraryImport.

AaronRobinsonMSFT · 2026-02-24T17:39:26Z

Do we need to re-enable or create a new sets of tests for this? We have tests for these APIs, src/tests/Interop/ObjectiveC/ObjectiveCMarshalAPI, but I don't know if we've disabled them for R2R (it doesn't look like it), so are we missing them during R2R testing somehow?

/cc @jkoritzinsky

jkoritzinsky · 2026-02-24T19:04:53Z

Do we need to re-enable or create a new sets of tests for this? We have tests for these APIs, src/tests/Interop/ObjectiveC/ObjectiveCMarshalAPI, but I don't know if we've disabled them for R2R (it doesn't look like it), so are we missing them during R2R testing somehow?

The tests there are falling back to JIT/Interpreter for these stubs (which is correct behavior). We could add testing to validate that the methods were actually generated (src/tests/readytorun/tests/test.cs and the mainv1.csproj project file have examples of the logic (pass the --map option when running cg2 and then validate the expected entries exist as part of running the test).

Analyzes reviewer feedback from BrzVlad, AaronRobinsonMSFT, and jkoritzinsky. Includes recommended code changes and test coverage plan. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…ning findings - Add LibraryImport vs DllImport analysis explaining why switching macios wouldn't solve the R2R precompilation issue - Add P/Invoke inlining call chain trace showing CorInfoImpl.ReadyToRun.cs path (not VM dllimport.cpp) for R2R marshalling decisions - Document graceful fallback behavior for unsupported marshalling types - Confirm BrzVlad's approach is both cleaner and more efficient Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

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- Document new 3-commit structure and PInvokeILStubMethodIL mechanism - Mark BrzVlad's recommendations as implemented (GeneratesPInvoke reverted, ShouldCheckForPendingException removed from IsMarshallingRequired) - Add open concerns: code size, P/Invoke frame correctness, non-void IL stack risk, JIT helper alternative under investigation - Test coverage still flagged as missing (merge blocker) Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

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Adds a ReadyToRun test that validates objc_msgSend P/Invoke stubs are precompiled into the R2R image using crossgen2's --map output. The test: - Declares blittable objc_msgSend DllImport methods - Compiles them with crossgen2 --map - At runtime, reads the .map file and asserts P/Invoke stub entries exist - Only runs on macOS (CLRTestTargetUnsupported for non-Apple platforms) Addresses reviewer feedback from jkoritzinsky and AaronRobinsonMSFT requesting test coverage for the R2R ObjC P/Invoke precompilation feature. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Validates that blittable objc_msgSend P/Invoke stubs are precompiled into the ReadyToRun image by checking the crossgen2 --map output for MethodWithGCInfo entries. Key details: - Uses /usr/lib/libobjc.dylib (exact path matched by ShouldCheckForPendingException) - Checks specifically for MethodWithGCInfo entries (not just any map reference) - Requires --inputbubble so crossgen2 can resolve ThrowPendingExceptionObject tokens - macOS-only (CLRTestTargetUnsupported for non-OSX) Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Promote regression test verification to a mandatory section in copilot-instructions.md with explicit guidance on using baseline build artifacts for negative verification - Add ReadyToRun/crossgen2 test gotchas section covering --inputbubble, map entry semantics, and MarshalHelpers.cs string matching - Add cross-component build warning (crossgen2 + CoreLib changes) - Add design doc discoverability instruction - Strengthen CoreLib rebuild guidance to explain libs.pretest necessity - Add Step 5 (mandatory negative verification) to jit-regression-test skill - Create src/tests/readytorun/README.md documenting test patterns, map validation rules, version bubble constraints, and platform gating Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 4 comments.

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Add P/Invoke marshalling and R2R-specific review rules: - inputbubble requirement for cross-module CoreLib references - IsMarshallingRequired prevents JIT from inlining past R2R stubs - Separation of marshalling vs platform-specific stub requirements - DllImport detection string matching against MarshalHelpers.cs - R2R map validation (MethodWithGCInfo vs MethodFixupSignature) - R2R+NativeAOT P/Invoke emitter alignment checks - R2R tests need both map validation and runtime verification Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

kotlarmilos · 2026-05-18T13:02:04Z

@copilot resolve the merge conflicts in this pull request

Copilot

Copilot's findings

Files reviewed: 12/12 changed files
Comments generated: 7

- Spill native return value across the ThrowPendingExceptionObject helper call so the IL evaluation stack is empty at the call site. - Add runtime pending-exception validation to the ObjCPInvokeR2R test via SetMessageSendCallback + SetMessageSendPendingException. - Add $(TestLibraryProjectPath) ProjectReference to ObjCPInvokeR2R.csproj to match other R2R test projects. - Remove pr-124770-{plan,analysis}.md scratch notes. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Copilot's findings

Files reviewed: 6/6 changed files
Comments generated: 0 new

Mirrors the existing AddNecessaryAsyncReferences pattern: when an ObjC P/Invoke is selected for R2R compilation, the new emitter calls ObjectiveCMarshal.ThrowPendingExceptionObject() in CoreLib. In non-composite mode (the default on iOS), CoreLib is an external reference, so without manifest pre-registration the version-bubble check in ManifestMetadataTableNode rejects the helper and crossgen2 fails. Uses GetType(throwIfNotFound: false) so non-Apple workloads (no ObjC interop) skip the lookup harmlessly. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

CopilotAI review requested due to automatic review settings February 23, 2026 22:47

davidnguyen-tech self-assigned this Feb 23, 2026

github-actionsBot added the area-ReadyToRun label Feb 23, 2026

Copilotstarted reviewing on behalf of davidnguyen-tech February 23, 2026 22:48 View session

davidnguyen-tech requested a review from BrzVlad February 23, 2026 22:55

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davidnguyen-tech added area-ReadyToRun-coreclr os-ios Apple iOS labels Feb 23, 2026

davidnguyen-tech changed the title ~~Enable R2R precompilation of ObjC objc_msgSend P/Invoke stubs~~Enable R2R precompilation of objc_msgSend P/Invoke stubsFeb 23, 2026

teo-tsirpanis added area-ReadyToRun-coreclr and removed area-ReadyToRun-coreclr area-ReadyToRun labels Feb 23, 2026

BrzVlad reviewed Feb 24, 2026
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Comment threadsrc/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/ReadyToRunCompilationModuleGroupBase.cs Outdated

BrzVlad mentioned this pull request Feb 24, 2026
Increase number of R2R methods used at runtime on ios #124799
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build-analysisBot mentioned this pull request Mar 11, 2026
MsQuic fails with QUIC_STATUS_OUT_OF_MEMORY on AzureLinux #123216
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This was referenced Mar 13, 2026
System.Diagnostics.Tests.ProcessStartInfoTests.TestWindowStyle failing in CI #119533
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System.IO.Tests.Directory_Create_Tests.FileSystemWatcher_Directory_Create_InNestedDirectory fails with "Created event did not occur as expected" #103630
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Comment threadsrc/tests/readytorun/README.md Outdated
Comment threadsrc/tests/readytorun/ObjCPInvokeR2R/ObjCPInvokeR2R.csproj
Comment threadpr-124770-plan.md Outdated
Comment threadpr-124770-analysis.md Outdated

build-analysisBot mentioned this pull request Mar 20, 2026
runtime / Build / maccatalyst-x64 release MonoAOTOffsets / Build product failure #120116
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PureWeen mentioned this pull request Mar 20, 2026
Improve Copilot guidance for R2R tests and regression verification #125833
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CopilotAI mentioned this pull request Mar 20, 2026
Fix flaky TestWindowStyle: check only STARTF_USESHOWWINDOW bit, remove ShellExecute cases #125847
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github-actionsBot added the area-crossgen2-coreclr only use for closed issues label Apr 9, 2026

Merge branch 'main' into feature/r2r-objc-pinvoke-stubs
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kotlarmilosand others added 2 commits May 18, 2026 16:18

Drop unrelated .github and README changes
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Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

CopilotAI review requested due to automatic review settings May 18, 2026 14:21

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build-analysisBot mentioned this pull request May 18, 2026
[wasm] Tests failing with DirectoryNotFoundException trying to load test data #128293
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