Trim unused CoreCLR native components from dotnet-linker-tests build

[sbomer]

The Runtime_Release jobs in the dotnet-linker-tests pipeline build the clr subset. That expands to a list of CoreCLR subsets (eng/Subsets.props, DefaultCoreClrSubsets) which includes clr.native, and clr.native performs a full CoreCLR native build. That pulls in components the trimming and NativeAOT tests never use — most notably the cross-target alt-JITs and SuperPMI.

This PR narrows the subset list to what those tests actually need, and fixes a Windows/Unix asymmetry in the JIT install rules that blocked doing so.

1. src/coreclr/jit/CMakeLists.txt — install the target-specific JIT into the jit component on Windows

crossgen2 and ILC don't load clrjit; they load the JIT named for the target they're compiling for, e.g. clrjit_win_x64_x64 when targeting win-x64.

On Unix that JIT is already installed into the jit component alongside clrjit:

if (CLR_CMAKE_TARGET_UNIX)
      ...
      install_clr(TARGETS clrjit_unix_${ARCH_TARGET_NAME}_${ARCH_HOST_NAME} DESTINATIONS . COMPONENT jit)
endif()

Windows had no equivalent rule, so there the target-specific JIT was only ever installed as part of alljits. Any Windows build that selects native components individually rather than doing a full native build therefore produces a crossgen2 that fails as soon as it runs:

EXEC : error : Dll was not found. [src\coreclr\crossgen-corelib.proj]
error MSB3073: ...crossgen2.exe ... System.Private.CoreLib.dll ... exited with code 1

This mirrors the existing Unix rule for Windows targets. Full native builds are unaffected, since alljits already installed these JITs — it only makes the jit component self-contained on Windows the way it already is on Unix.

2. eng/pipelines/runtime-linker-tests.yml — narrow the subset list

clr.native is replaced by clr.runtime + clr.nativeaotruntime (the runtime and nativeaot CMake components). src/coreclr/components.cmake shows runtime already depends on jit, iltools, debug and hosts, and with the fix above jit now also carries the JIT crossgen2/ILC need.

Dropped as a result:

• alljits — the cross-target alt-JITs. On win-x64 only clrjit and clrjit_win_x64_x64 are now built; on linux-x64 only clrjit and clrjit_unix_x64_x64.
• spmi — SuperPMI and its shims.
• clr.packages — only produces the ILAsm/ILDAsm/TestHost/Sdk.IL nupkgs, referenced solely by eng/Publishing.props for official-build publishing. Packing them takes ~2.5s, so this is a cleanliness change, not a perf one.
• clr.crossarchtools — redundant here: _BuildCrossComponents is already set whenever ClrRuntimeBuildSubsets is non-empty for CoreCLR, and the cross-tool build is gated on _BuildAnyCrossArch, which is false for native windows-x64/linux-x64. Verified that no cross-arch build directory is produced either way.

Measurements

Measured on CI, comparing build 1538104 (this PR) against 1534932 (a recent PR build of the unchanged pipeline):

	ninja targets	"Build product"
windows-x64 (critical path)	2646 → 1901 (−28.2%)	40.0m → 35.4m (−4.6m)
linux-x64	2837 → 2132 (−24.8%)	31.7m → 29.0m (−2.7m)
browser-wasm	unaffected (builds mono)	26.0m → 26.7m

The windows-x64 job as a whole goes from 62.4m to 56.5m. Total build wall clock went from 75.0m to 68.0m, though that figure includes queue variance across runs — the "Build product" numbers are the reliable ones. linux-x64 saves time too but stays off the critical path.

Locally, isolating just the CoreCLR native build on linux-x64 at ninja -j 4 (the parallelism CI uses) gives 4m03s → 3m05s, i.e. −24%, consistent with the CI result.

Validation

Locally, from a clean tree with the narrowed subsets:

• Trimming tests: 88 tests pass
• NativeAOT test apps: 57 tests pass
• Artifacts verified: libcoreclr.so, ilc, crossgen2, ilasm/ildasm, DAC/mscordbi and the aotsdk all still present; superpmi and the unused alt-JITs gone

On CI, all three dotnet-linker-tests jobs (windows-x64, linux-x64, browser-wasm) pass, including the trimming and NativeAOT test app steps, with no change in test counts or coverage.

Two unrelated failures show up on this PR and are not caused by it:

• runtime (Build openbsd-x64 Debug CoreCLR_Bootstrapped) — fails with NETSDK1203 on every recent PR (sampled 6/6); the leg only passes on main because rolling builds run it as Release.
• System.Net.Security.Tests.TlsSessionTests.SslStreamServer_RejectsClientCert_ClientObservesAlert on linux-arm64 — known flaky, tracked by Disable TLS resume in SslStreamServer_RejectsClientCert_ClientObservesAlert #131755 (44 hits in the last month).

Note

This content was created with assistance from AI.

[azure-pipelines]

Azure Pipelines:
Successfully started running 5 pipeline(s).
11 pipeline(s) were filtered out due to trigger conditions.
There may be pipelines that require an authorized user to comment /azp run to run.

[dotnet-policy-service]

Tagging subscribers to this area: @agocke, @dotnet/ilc-contrib
See info in area-owners.md if you want to be subscribed.

[Copilot]

Pull request overview

Updates the runtime-linker-tests Azure Pipelines definition to build a narrower set of CoreCLR subsets for the Runtime_Release jobs, aiming to avoid building unused native components during trimming and NativeAOT test runs.

Changes:

• Replaces -s clr+... with an explicit subset list centered on clr.runtime plus NativeAOT/tooling subsets.
• Adds inline pipeline comments documenting why alljits and spmi are intentionally excluded.

Show a summary per file

File	Description
eng/pipelines/runtime-linker-tests.yml	Switches the CoreCLR build from clr to an explicit subset list intended to avoid building unused native components for linker/NativeAOT tests.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 1

[Copilot]

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 0 new

[Copilot]

Copilot's findings

Suppressed comments (1)

eng/pipelines/runtime-linker-tests.yml:119

• The comment is slightly inaccurate: the clr subset expands to the full $(DefaultCoreClrSubsets) list (which includes clr.native among others), not to clr.native alone. Rewording avoids confusion for future maintainers reading the pipeline.

            # This replaces the previous `clr` subset (which expands to `clr.native` and builds every native component)

• Files reviewed: 2/2 changed files
• Comments generated: 0 new

[azure-pipelines]

Azure Pipelines:
Successfully started running 7 pipeline(s).
9 pipeline(s) were filtered out due to trigger conditions.
There may be pipelines that require an authorized user to comment /azp run to run.