CoreCLR: Compute and pass instruction set to crossgen2 based on deployment target

[Copilot]

Implementation Plan

• All initial implementation tasks
• All code review feedback addressed
• Final polish completed
• Verify build and all tests pass

Summary

This PR implements support for computing the minimum instruction set an app requires based on the deployment target (SupportedOSPlatformVersion) and runtime identifier, and passes this information to the R2R/NAOT compiler (crossgen2) via the --instruction-set argument.

All feedback addressed:

• Changed target branch to net11.0
• Moved target to Microsoft.Sdk.R2R.targets
• Added comprehensive documentation with source links
• RuntimeIdentifier handling for architecture detection
• Simulator handling (run on Mac hardware)
• Property renamed to ComputeInstructionSetForReadyToRun with documentation
• Merged device dictionaries using DeviceInfo structure
• Used SdkVersions constants for latest OS versions
• Conditional compilation for nullability
• Case-insensitive architecture comparison
• Parameters sorted alphabetically
• Added _DetectSdkLocations dependency
• Removed SessionId property (not needed)
• Duplicate argument prevention

Implementation Details

ComputeInstructionSet MSBuild Task:

• Required inputs: RuntimeIdentifier, SupportedOSPlatformVersion (alphabetically sorted)
• Single DeviceInfo dictionary: device → (CPU, max OS version)
• Uses SdkVersions.iOS/SdkVersions.TVOS for latest OS
• CPU → instruction set mapping (A9→armv8-a, M1→apple-m1, etc.)
• iOS/tvOS devices: oldest device supporting target OS
• macOS/Mac Catalyst/Simulators: RuntimeIdentifier architecture
• Returns only crossgen2-supported instruction sets

Integration:

• Target: _ComputeInstructionSetForCrossgen2 in Microsoft.Sdk.R2R.targets
• Runs when: PublishReadyToRun=true and ComputeInstructionSetForReadyToRun != false
• Depends on: _DetectSdkLocations
• Runs before: ResolveReadyToRunCompilers
• Parameters: RuntimeIdentifier, SdkDevPath, SupportedOSPlatformVersion, TargetFrameworkMoniker (no SessionId)
• Appends: --instruction-set:value (with duplicate check)

Documentation:

• ComputeInstructionSetForReadyToRun property in docs/building-apps/build-properties.md
• Default: true
• Example: how to opt out

Testing:

• ✅ All 26 unit tests passing
• ✅ Build succeeds with no errors

Original prompt

---

This section details on the original issue you should resolve

<issue_title>CoreCLR: tell the R2R/NAOT compiler which instruction set an app requires/support</issue_title>
<issue_description>Ref: dotnet/runtime#122249

To enable usage of newer instructions in native code, we should implement support for computing the minimum/oldest CPU / instruction set an app requires based on the deployment target (min supported os version), and passing this info along to the R2R/NAOT compiler.

See also: https://teams.microsoft.com/l/chat/19:ea31bce2f4da4abd977f4b4544e6dedd@thread.v2/conversations?context=%7B%22contextType%22%3A%22chat%22%7D</issue_description>

Comments on the Issue (you are @copilot in this section)

@rolfbjarne > Instruction set argument: `--instruction-set` @rolfbjarne The information about which OS versions support which instruction sets is not available in a useful manner, but can be computed by collecting the information from multiple sources:

• Create a table of every Apple mobile and desktop device, with:
  • The corresponding CPU model (e.g. iPhone 6s has A9 CPUs)
  • The maximum OS version supported by that device (e.g. iPhone 6s' latest OS version is iOS 15.8.6)
• Create a table of every CPU model, with:
  • The instruction set supported by that CPU model, e.g. A9 CPUs support the ARMv8-A instruction set.

With these two tables it's possible to compute the earliest instruction set that a given OS version supports.

The task is to create an MSBuild task with this logic to compute the earliest instruction set the current minimum OS platform version (the SupportedOSPlatformVersion MSBuild property) needs, and then pass this instruction set to the crossgen2 compiler (by setting the PublishReadyToRunCrossgen2ExtraArgs MSBuild property).

We also need a list of instruction sets supported by the crossgen compiler, so that we don't select an instruction set the crossgen compiler doesn't know about. This is the current list (as found by running crossgen2 --help):

The following CPU names are predefined groups of instruction sets and can be used in --instruction-set too:
x86-64-v2, x86-64-v3, x86-64-v4, armv8-a, armv8.1-a, armv8.2-a, armv8.3-a, armv8.4-a, armv8.5-a, armv8.6-a, apple-m1

• Fixes CoreCLR: tell the R2R/NAOT compiler which instruction set an app requires/support #24410

---

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[rolfbjarne]

Change the target branch to net11.0 instead of main, and move the _ComputeInstructionSetForCrossgen2 target to the Microsoft.Sdk.R2R.targets file.

[Copilot]

Change the target branch to net11.0 instead of main, and move the _ComputeInstructionSetForCrossgen2 target to the Microsoft.Sdk.R2R.targets file.

Done. Changed the base branch to net11.0 and moved the _ComputeInstructionSetForCrossgen2 target to Microsoft.Sdk.R2R.targets (commit 28b27d80d).

[vs-mobiletools-engineering-service2]

💻 [CI Build #ac2a65b] Tests on macOS M1 - Mac Monterey (12) passed 💻

✅ All tests on macOS M1 - Mac Monterey (12) passed.

Pipeline on Agent
Hash: ac2a65b2f7fe183982f9bbf3a647497860c01bf6 [PR build]

[vs-mobiletools-engineering-service2]

💻 [CI Build #ac2a65b] Tests on macOS M1 - Mac Ventura (13) passed 💻

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

Pipeline on Agent
Hash: ac2a65b2f7fe183982f9bbf3a647497860c01bf6 [PR build]

[rolfbjarne]

This needs a dotnet bump (#24651) first, because the size test apps are now trimmed, so we need the fix for dotnet/runtime#123953.

[vs-mobiletools-engineering-service2]

✅ [PR Build #266f35b] Build passed (Detect API changes) ✅

Pipeline on Agent
Hash: 266f35bf11491227901643f53915b86288ab8957 [PR build]

[vs-mobiletools-engineering-service2]

✅ [CI Build #266f35b] Build passed (Build packages) ✅

Pipeline on Agent
Hash: 266f35bf11491227901643f53915b86288ab8957 [PR build]

[vs-mobiletools-engineering-service2]

✅ API diff for current PR / commit

NET (empty diffs)

• iOS: vsdrops gist ( No breaking changes )
• tvOS: vsdrops gist ( No breaking changes )
• MacCatalyst: vsdrops gist ( No breaking changes )
• macOS: vsdrops gist ( No breaking changes )

✅ API diff vs stable

NET (empty diffs)

• iOS: vsdrops gist ( No breaking changes )
• tvOS: vsdrops gist ( No breaking changes )
• MacCatalyst: vsdrops gist ( No breaking changes )
• macOS: vsdrops gist ( No breaking changes )

ℹ️ Generator diff

Generator Diff: vsdrops (html) vsdrops (raw diff) gist (raw diff) - Please review changes)

Pipeline on Agent
Hash: 266f35bf11491227901643f53915b86288ab8957 [PR build]

[vs-mobiletools-engineering-service2]

✅ [CI Build #266f35b] Build passed (Build macOS tests) ✅

Pipeline on Agent
Hash: 266f35bf11491227901643f53915b86288ab8957 [PR build]

[vs-mobiletools-engineering-service2]

💻 [CI Build #266f35b] Tests on macOS X64 - Mac Sonoma (14) passed 💻

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

Pipeline on Agent
Hash: 266f35bf11491227901643f53915b86288ab8957 [PR build]

[vs-mobiletools-engineering-service2]

💻 [CI Build #266f35b] Tests on macOS arm64 - Mac Sequoia (15) passed 💻

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

Pipeline on Agent
Hash: 266f35bf11491227901643f53915b86288ab8957 [PR build]

[vs-mobiletools-engineering-service2]

💻 [CI Build #266f35b] Tests on macOS arm64 - Mac Tahoe (26) passed 💻

✅ All tests on macOS arm64 - Mac Tahoe (26) passed.

Pipeline on Agent
Hash: 266f35bf11491227901643f53915b86288ab8957 [PR build]

[vs-mobiletools-engineering-service2]

🚀 [CI Build #266f35b] Test results 🚀

Test results

✅ All tests passed on VSTS: test results.

🎉 All 117 tests passed 🎉

Tests counts

✅ 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. [attempt 2] 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 (MacCatalyst): All 11 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: 266f35bf11491227901643f53915b86288ab8957 [PR build]