[dotnet] Add support for ReadyToRun. #24437

rolfbjarne · 2025-12-12T17:47:18Z

Description

This PR adds ReadyToRun support for CoreCLR.

Changes

Introduce ReadyToRun configuration in Xamarin.Shared.Sdk.props.
Add ReadyToRun targets to Microsoft.Shared.R2R.targets (a new file).
Update bundler environment variables in Xamarin.Shared.Sdk.targets to support ReadyToRun
Add host_runtime_contract.h to the build process in Makefile
Update coreclr-bridge.m and runtime.m for R2R image handling and logging
Update runtime.h to reflect changes in the xamarin_pinvoke_override function signature
Add support in the CompileAppManifest target to create the Info.plist for frameworks.
Enable CoreCLR tests run R2R.
Add a test variation for CoreCLR for the app size test.

Fixes dotnet/runtime#120052.

Copilot

Pull request overview

This PR adds ReadyToRun (R2R) support for CoreCLR on Apple mobile platforms (iOS, tvOS). ReadyToRun is an ahead-of-time (AOT) compilation technology that improves app startup performance by pre-compiling managed assemblies to native code. The implementation involves integrating CoreCLR's R2R infrastructure through a new host runtime contract interface, generating composite R2R images into frameworks or dynamic libraries, and enabling the feature by default for non-macOS CoreCLR builds.

Key Changes

Added infrastructure to pass PublishReadyToRun configuration through the build pipeline
Implemented native code integration for R2R via the host_runtime_contract interface
Created MSBuild targets to build R2R composite images and link them into frameworks or dylibs
Removed libclrjit.dylib dependency when R2R is enabled (replaced with R2R interpretation)

Reviewed changes

Copilot reviewed 17 out of 18 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
tools/dotnet-linker/LinkerConfiguration.cs	Adds parsing for PublishReadyToRun configuration property
tools/common/Target.cs	Generates extern declarations for RTR_HEADER symbol in generated main.m file
tools/common/Application.cs	Adds PublishReadyToRun nullable boolean property to Application class
runtime/xamarin/runtime.h	Changes xamarin_pinvoke_override return type to const void*
runtime/xamarin/main.h	Declares xamarin_rtr_header global variable
runtime/runtime.m	Implements R2R integration via host_runtime_contract and adds dyld image size calculation
runtime/coreclr-bridge.m	Fixes logging bug where wrong variable was being accessed
runtime/Makefile	Updates to download host_runtime_contract.h header from dotnet/runtime
runtime/.gitignore	Ignores the downloaded host_runtime_contract.h file
msbuild/Xamarin.MacDev.Tasks/Tasks/CompileAppManifest.cs	Adds IsFramework property and CFBundlePackageType support for frameworks
dotnet/targets/Xamarin.Shared.Sdk.targets	Passes PublishReadyToRun to linker, removes libclrjit.dylib, imports R2R targets
dotnet/targets/Xamarin.Shared.Sdk.props	Sets R2R as default for CoreCLR mobile builds, adds environment variable fallback
dotnet/targets/Microsoft.Sdk.R2R.targets	New file implementing R2R composite image building and framework/dylib creation
dotnet/Makefile	Includes new Microsoft.Sdk.R2R.targets in SDK package
tests/dotnet/UnitTests/AppSizeTest.cs	Removes test ignore attribute and fixes assertion message logic
tests/dotnet/UnitTests/expected/iOS-CoreCLR-R2R-size.txt	New baseline for R2R app sizes
tests/dotnet/UnitTests/expected/iOS-CoreCLR-Interpreter-size.txt	Updated baseline reflecting removal of libclrjit.dylib

dotnet/targets/Microsoft.Sdk.R2R.targets

runtime/runtime.m

tools/common/Target.cs

dotnet/targets/Microsoft.Sdk.R2R.targets

vs-mobiletools-engineering-service2 · 2025-12-15T19:57:37Z

💻 [CI Build #55f9501] Tests on macOS M1 - Mac Ventura (13) passed 💻

✅ All tests on macOS M1 - Mac Ventura (13) passed.

Pipeline on Agent
Hash: 55f95010f0e7d43d3303265aa29fff58fd313896 [PR build]

…dyToRun compiler's composite output. And then link with and bundle the .framework or .dylib we created.

…e're in Release.

In particular use static libraries when using any runtime on device.

…when building for device.

vs-mobiletools-engineering-service2 · 2026-01-08T12:26:23Z

✅ [CI Build #8824e4e] Build passed (Build packages) ✅

Pipeline on Agent
Hash: 8824e4ed9abae37f54396ae756c0193a5fbe6bc6 [PR build]

vs-mobiletools-engineering-service2 · 2026-01-08T12:27:03Z

✅ [PR Build #8824e4e] Build passed (Detect API changes) ✅

Pipeline on Agent
Hash: 8824e4ed9abae37f54396ae756c0193a5fbe6bc6 [PR build]

vs-mobiletools-engineering-service2 · 2026-01-08T12:54:34Z

🔥 Failed to compare API and create generator diff 🔥

Error: 'make' failed for the hash aced0a1.

Pipeline on Agent
Hash: 8824e4ed9abae37f54396ae756c0193a5fbe6bc6 [PR build]

vs-mobiletools-engineering-service2 · 2026-01-08T13:01:36Z

✅ [CI Build #8824e4e] Build passed (Build macOS tests) ✅

Pipeline on Agent
Hash: 8824e4ed9abae37f54396ae756c0193a5fbe6bc6 [PR build]

vs-mobiletools-engineering-service2 · 2026-01-08T13:11:49Z

💻 [CI Build #8824e4e] Tests on macOS X64 - Mac Sonoma (14) passed 💻

✅ All tests on macOS X64 - Mac Sonoma (14) passed.

Pipeline on Agent
Hash: 8824e4ed9abae37f54396ae756c0193a5fbe6bc6 [PR build]

vs-mobiletools-engineering-service2 · 2026-01-08T13:16:33Z

💻 [CI Build #8824e4e] Tests on macOS arm64 - Mac Sequoia (15) passed 💻

✅ All tests on macOS arm64 - Mac Sequoia (15) passed.

Pipeline on Agent
Hash: 8824e4ed9abae37f54396ae756c0193a5fbe6bc6 [PR build]

vs-mobiletools-engineering-service2 · 2026-01-08T13:25:59Z

❌ [CI Build #8824e4e] Tests on macOS arm64 - Mac Tahoe (26) failed ❌

Tests on macOS arm64 - Mac Tahoe (26) failed for unknown reasons.

Pipeline on Agent
Hash: 8824e4ed9abae37f54396ae756c0193a5fbe6bc6 [PR build]

vs-mobiletools-engineering-service2 · 2026-01-08T13:50:16Z

🔥 [CI Build #8824e4e] Test results 🔥

Test results

❌ Tests failed on VSTS: test results

0 tests crashed, 1 tests failed, 116 tests passed.

Failures

❌ monotouch tests (MacCatalyst)

1 tests failed, 10 tests passed.

Failed tests

monotouch-test/Mac Catalyst/Release (managed static registrar): Failed (Test run failed.
Tests run: 3493 Passed: 3291 Inconclusive: 13 Failed: 1 Ignored: 201)

Html Report (VSDrops) Download

Successes

✅ cecil: All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (iOS): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (MacCatalyst): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (macOS): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (Multiple platforms): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (tvOS): All 1 tests passed. Html Report (VSDrops) Download
✅ framework: All 2 tests passed. Html Report (VSDrops) Download
✅ fsharp: All 4 tests passed. Html Report (VSDrops) Download
✅ generator: All 5 tests passed. Html Report (VSDrops) Download
✅ interdependent-binding-projects: All 4 tests passed. Html Report (VSDrops) Download
✅ introspection: All 4 tests passed. Html Report (VSDrops) Download
✅ linker: All 44 tests passed. Html Report (VSDrops) Download
✅ monotouch (iOS): All 9 tests passed. Html Report (VSDrops) Download
✅ monotouch (macOS): All 9 tests passed. Html Report (VSDrops) Download
✅ monotouch (tvOS): All 9 tests passed. Html Report (VSDrops) Download
✅ msbuild: All 2 tests passed. Html Report (VSDrops) Download
✅ windows: All 3 tests passed. Html Report (VSDrops) Download
✅ xcframework: All 4 tests passed. Html Report (VSDrops) Download
✅ xtro: All 1 tests passed. Html Report (VSDrops) Download

Pipeline on Agent
Hash: 8824e4ed9abae37f54396ae756c0193a5fbe6bc6 [PR build]

kotlarmilos · 2026-01-08T14:03:43Z

dotnet/targets/Microsoft.Sdk.R2R.targets

+		<CreateR2RFramework Condition="'$(CreateR2RFramework)' == '' ">true</CreateR2RFramework>
+		<CreateR2RDylib Condition="'$(CreateR2RDylib)' == '' And '$(CreateR2RFramework)' != 'true'">true</CreateR2RDylib>
+
+		<FilterReadyToRunAssemblies Condition="'$(FilterReadyToRunAssemblies)' == '' And '$(Configuration)' == 'Release'">true</FilterReadyToRunAssemblies>


I think user assemblies should be excluded in Debug build to allow for debugging, not in Release build.

kotlarmilos · 2026-01-08T14:05:06Z

dotnet/targets/Microsoft.Sdk.R2R.targets

+			BeforeTargets="ResolveReadyToRunCompilers">
+		<ItemGroup>
+			<_ResolvedAssembliesToPublish Include="@(ResolvedFileToPublish)" Condition="'%(Extension)' == '.dll' And '%(ResolvedFileToPublish.Culture)' == '' And '%(ResolvedFileToPublish.DestinationSubDirectory)' == ''" />
+			<_NonUserAssemblies


Does this include iOS SDK and MAUI assemblies?

kotlarmilos · 2026-01-08T14:18:52Z

dotnet/targets/Xamarin.Shared.Sdk.targets

-			<_LibMonoLinkMode Condition="'$(_LibMonoLinkMode)' == ''">static</_LibMonoLinkMode>
+			<_LibMonoLinkMode Condition="'$(_LibMonoLinkMode)' == '' And '$(_PlatformName)' == 'MacCatalyst' And '$(UseMonoRuntime)' == 'true'">static</_LibMonoLinkMode>
+			<!-- we can't use dylibs for mobile apps when building for device, because the App Store won't allow it -->
+			<_LibMonoLinkMode Condition="'$(_LibMonoLinkMode)' == '' And '$(ComputedPlatform)' == 'iPhone'">static</_LibMonoLinkMode>


Does it convert dylib to a framework instead of static linking?

kotlarmilos · 2026-01-08T14:21:52Z

tests/dotnet/UnitTests/expected/iOS-CoreCLR-R2R-size.txt

+archived-expanded-entitlements.xcent: 384 bytes (0.4 KB = 0.0 MB)
+Frameworks/libclrjit.framework/_CodeSignature/CodeResources: 1,798 bytes (1.8 KB = 0.0 MB)
+Frameworks/libclrjit.framework/Info.plist: 808 bytes (0.8 KB = 0.0 MB)
+Frameworks/libclrjit.framework/libclrjit: 3,157,152 bytes (3,083.2 KB = 3.0 MB)


This should be excluded from the app bundle.

kotlarmilos · 2026-01-08T14:24:08Z

dotnet/targets/Microsoft.Sdk.R2R.targets

+			<_R2RFrameworkSymlinks Include="$(_R2RFrameworkPath)/Versions/Current" SymlinkTo="A" />
+		</ItemGroup>
+
+		<!-- write a hash of all the relevant input so that we can force a re-link if necessary -->


/cc: @simonrozsival Caching of R2R image on iOS.

rolfbjarne requested a review from Copilot December 12, 2025 17:47

Copilot started reviewing on behalf of rolfbjarne December 12, 2025 17:47 View session

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rolfbjarne force-pushed the dev/rolf/coreclr-r2r branch from 5d67786 to 270a76b Compare December 12, 2025 18:08

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rolfbjarne and others added 2 commits January 8, 2026 09:30

[dotnet] Add support for creating a .framework or .dylib from the Rea…

26943b9

…dyToRun compiler's composite output. And then link with and bundle the .framework or .dylib we created.

[dotnet] Exclude user assemblies from ReadyToRun compilation unless w…

d5c9059

…e're in Release.

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rolfbjarne added 4 commits January 8, 2026 12:53

[xharness] Add missing flags for a few CoreCLR variations.

8c4513f

[dotnet] Fix computing _LibMonoLinkMode when not using Mono.

0ea2e6d

In particular use static libraries when using any runtime on device.

[dotnet] Add support for transforming CoreCLR's dylibs to frameworks …

19ce833

…when building for device.

[tests] Enable ReadyToRun app size test.

8824e4e

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rolfbjarne force-pushed the dev/rolf/coreclr-r2r branch from f5899ab to 8824e4e Compare January 8, 2026 11:54

kotlarmilos reviewed Jan 8, 2026

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[dotnet] Add support for ReadyToRun. #24437

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[dotnet] Add support for ReadyToRun. #24437

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Key Changes

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vs-mobiletools-engineering-service2 commented Dec 15, 2025

💻 [CI Build #55f9501] Tests on macOS M1 - Mac Ventura (13) passed 💻

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vs-mobiletools-engineering-service2 commented Jan 8, 2026

✅ [CI Build #8824e4e] Build passed (Build packages) ✅

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vs-mobiletools-engineering-service2 commented Jan 8, 2026

✅ [PR Build #8824e4e] Build passed (Detect API changes) ✅

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vs-mobiletools-engineering-service2 commented Jan 8, 2026

✅ [CI Build #8824e4e] Build passed (Build macOS tests) ✅

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vs-mobiletools-engineering-service2 commented Jan 8, 2026

💻 [CI Build #8824e4e] Tests on macOS X64 - Mac Sonoma (14) passed 💻

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vs-mobiletools-engineering-service2 commented Jan 8, 2026

💻 [CI Build #8824e4e] Tests on macOS arm64 - Mac Sequoia (15) passed 💻

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vs-mobiletools-engineering-service2 commented Jan 8, 2026

❌ [CI Build #8824e4e] Tests on macOS arm64 - Mac Tahoe (26) failed ❌

rolfbjarne commented Dec 12, 2025 •

edited

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