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Trim netcoreapp libraries against implementations #136495

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78656c1
Trim netcoreapp libraries against implementations
am11 Oct 26, 2026
1db83d6
Merge remote-tracking branch 'dotnet/main' into illink-impl-references
am11 Oct 28, 2026
ae5bdc6
Merge remote-tracking branch 'dotnet/main' into illink-impl-references
am11 Oct 29, 2026
43672fb
Address review feedback
am11 Oct 29, 2026
3f3c51c
Merge remote-tracking branch 'dotnet/main' into HEAD
am11 Oct 29, 2026
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144 changes: 122 additions & 22 deletions eng/illink.targets
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,11 @@
<PropertyGroup>
<IsTrimmable Condition="'$(IsTrimmable)' == ''">true</IsTrimmable>
<PrepareResourcesDependsOn>_EmbedILLinkXmls;$(PrepareResourcesDependsOn)</PrepareResourcesDependsOn>
<TargetsTriggeredByCompilation Condition="'$(DesignTimeBuild)' != 'true'">$(TargetsTriggeredByCompilation);ILLinkTrimAssembly</TargetsTriggeredByCompilation>
<TargetsTriggeredByCompilation Condition="'$(DesignTimeBuild)' != 'true'">$(TargetsTriggeredByCompilation);_ILLinkMoveUntrimmedAssembly</TargetsTriggeredByCompilation>
<!-- Anything consuming the compiler output, including concurrent requests to build this project, must wait for
it to be trimmed. API compat runs after CoreCompile and validates the trimmed assembly. -->
<CompileDependsOn>$(CompileDependsOn);ILLinkTrimAssembly</CompileDependsOn>
<ApiCompatValidateAssembliesDependsOn>$(ApiCompatValidateAssembliesDependsOn);ILLinkTrimAssembly</ApiCompatValidateAssembliesDependsOn>

<ILLinkDirectory Condition="'$(ILLinkDirectory)' == ''">$(MSBuildProjectDirectory)\ILLink\</ILLinkDirectory>
<ILLinkTrimAssemblyPath>$(IntermediateOutputPath)$(TargetName)$(TargetExt)</ILLinkTrimAssemblyPath>
Expand Down Expand Up @@ -54,6 +58,12 @@
TargetPath="%(FileName).$(AssemblyName).xml" />
</ItemGroup>

<!-- The untrimmed assembly is kept for trimming it again without recompiling, so it must survive IncrementalClean
in every build of the project, including those in which the trimming targets don't run. -->
<ItemGroup Condition="'$(ILLinkTrimAssembly)' == 'true'">
<FileWrites Include="$(ILLinkTrimInputAssembly);$(ILLinkTrimInputSymbols)" />
</ItemGroup>

<ItemGroup>
<ILLinkSubstitutionsXmls Include="$(ILLinkResourcesSubstitutionIntermediatePath)"
Condition="'$(GenerateResourcesSubstitutions)' == 'true'" />
Expand Down Expand Up @@ -192,15 +202,113 @@
</PropertyGroup>
</Target>

<!-- Examines the "input assembly" for IL that is unreachable from public API and trims that,
rewriting the assembly to an "output assembly" -->
<!-- Returns the implementation assemblies of the project references and, transitively, of their project references
(e.g. System.Private.Uri, which System.Runtime forwards to). A reference is resolved to the flavor that is built
for the TargetOS, which is the one in the shared framework, rather than the flavor that is compatible with the
referencing project's flavor (e.g. the unix flavor of System.Net.Http compiles against System.Net.Quic's
platform-agnostic flavor, while linux uses its linux flavor). -->
<Target Name="_GetILLinkReferencedImplementations"
Returns="@(_ILLinkTransitiveImplementation)">
<MSBuild Projects="@(_MSBuildProjectReferenceExistent)"
Targets="GetILLinkImplementationClosureForTargetOS"
Properties="%(_MSBuildProjectReferenceExistent.SetConfiguration)"
RemoveProperties="TargetFramework;%(_MSBuildProjectReferenceExistent.GlobalPropertiesToRemove)"
SkipNonexistentTargets="true"
BuildInParallel="$(BuildInParallel)">
<Output TaskParameter="TargetOutputs" ItemName="_ILLinkTransitiveImplementation" />
</MSBuild>
</Target>

<PropertyGroup>
<_GetILLinkImplementationClosureForTargetOSDependsOn Condition="'$(IsCrossTargetingBuild)' == 'true'">GetProjectWithBestTargetFrameworks</_GetILLinkImplementationClosureForTargetOSDependsOn>
</PropertyGroup>

<Target Name="GetILLinkImplementationClosureForTargetOS"
DependsOnTargets="$(_GetILLinkImplementationClosureForTargetOSDependsOn)"
Returns="@(_ILLinkImplementationClosureForTargetOS)">
<ItemGroup Condition="'$(IsCrossTargetingBuild)' == 'true'">
<_ILLinkBestInnerBuild Include="@(InnerBuildProjectsWithBestTargetFramework)"
Condition="$([System.String]::Copy('%(AdditionalProperties)').StartsWith('TargetFramework=$(NetCoreAppCurrent)'))" />
</ItemGroup>

<!-- The flavor isn't necessarily the one the project reference built, so make sure it is up to date. -->
<MSBuild Projects="@(_ILLinkBestInnerBuild)"
Targets="Build;GetILLinkImplementationClosure"
SkipNonexistentTargets="true"
Condition="'$(IsCrossTargetingBuild)' == 'true'">
<Output TaskParameter="TargetOutputs" ItemName="_ILLinkImplementationClosureForTargetOS" />
</MSBuild>

<CallTarget Targets="GetILLinkImplementationClosure"
Condition="'$(IsCrossTargetingBuild)' != 'true'">
<Output TaskParameter="TargetOutputs" ItemName="_ILLinkImplementationClosureForTargetOS" />
</CallTarget>
</Target>

<!-- Returns this project's implementation assembly followed by the implementations it references.
Packable libraries can be replaced by a newer package at run time, so they contribute their reference
assembly instead to avoid baking their implementation details into the referencing library. -->
<Target Name="GetILLinkImplementationClosure"
Condition="'$(IsReferenceAssemblyProject)' != 'true'"
DependsOnTargets="ResolveProjectReferences;_GetILLinkReferencedImplementations"
Returns="@(_ILLinkImplementationClosure)">
<ItemGroup>
<_ILLinkImplementationClosure Include="@(ResolvedMatchingContract->'%(FullPath)')"
Condition="'$(IsPackable)' == 'true'" />
<_ILLinkImplementationClosure Include="$(TargetPath)"
Condition="'$(IsPackable)' != 'true' or '@(ResolvedMatchingContract)' == ''" />
<_ILLinkImplementationClosure Include="@(_ILLinkTransitiveImplementation)" />
</ItemGroup>
</Target>

<UsingTask TaskName="ILLink"
AssemblyFile="$(ILLinkTasksAssembly)"
TaskFactory="TaskHostFactory"
Condition="'$(ILLinkTasksAssembly)' != ''" />

<!-- Move the freshly compiled assembly into a subdirectory for ILLink. -->
<Target Name="_ILLinkMoveUntrimmedAssembly"
Condition="'$(ILLinkTrimAssembly)' == 'true'">
<Move SourceFiles="$(ILLinkTrimAssemblyPath)"
DestinationFolder="$(ILLinkTrimInputPath)" />

<!-- Move the PDB into a subdirectory for ILLink if we are rewriting PDBs -->
<Move SourceFiles="$(ILLinkTrimAssemblySymbols)"
DestinationFolder="$(ILLinkTrimInputPath)"
Condition="'$(ILLinkRewritePDBs)' == 'true' and Exists('$(ILLinkTrimAssemblySymbols)')" />
</Target>

<Target Name="_PrepareILLinkTrimAssembly"
Condition="'$(ILLinkTrimAssembly)' == 'true'">
<!-- Shared framework libraries are trimmed against the implementations of their references, including
System.Private.CoreLib which is only reachable through type forwards, so that constants in those
implementations can be propagated. -->
<PropertyGroup>
<!-- The implementations (and their constants) are those of the TargetOS being built, so only use them
for flavors which run on that OS. -->
<_ILLinkUseImplementationReferences Condition="'$(IsNETCoreAppSrc)' == 'true' and
('$(TargetPlatformIdentifier)' == '' or
'$(TargetPlatformIdentifier)' == '$(TargetOS)' or
('$(TargetPlatformIdentifier)' == 'unix' and '$(TargetsUnix)' == 'true') or
('$(TargetPlatformIdentifier)' == 'linux' and '$(TargetsLinux)' == 'true') or
('$(TargetPlatformIdentifier)' == 'ios' and ('$(TargetsiOS)' == 'true' or '$(TargetsMacCatalyst)' == 'true')) or
('$(TargetPlatformIdentifier)' == 'tvos' and '$(TargetstvOS)' == 'true'))">true</_ILLinkUseImplementationReferences>
</PropertyGroup>

<CallTarget Targets="_GetILLinkReferencedImplementations"
Condition="'$(_ILLinkUseImplementationReferences)' == 'true'">
<Output TaskParameter="TargetOutputs" ItemName="_ILLinkReferencedImplementation" />
</CallTarget>
</Target>

<!-- Examines the "input assembly" for IL that is unreachable from public API and trims that,
rewriting the assembly to an "output assembly". Runs after CoreCompile rather than only when compiling
so that the assembly is trimmed again when the implementations it is trimmed against change. -->
<Target Name="ILLinkTrimAssembly"
Condition="'$(ILLinkTrimAssembly)' == 'true'"
DependsOnTargets="PrepareForAssembliesTrim">
Condition="'$(ILLinkTrimAssembly)' == 'true' and '$(DesignTimeBuild)' != 'true'"
DependsOnTargets="PrepareForAssembliesTrim;_PrepareILLinkTrimAssembly"
Inputs="$(ILLinkTrimInputAssembly);@(_ILLinkReferencedImplementation)"
Outputs="$(ILLinkTrimAssemblyPath)">
<PropertyGroup>
<!-- suppress warnings with the following codes:
IL2008: Could not find type A specified in resource B
Expand All @@ -220,8 +328,8 @@
<ILLinkArgs>$(ILLinkArgs) --action skip</ILLinkArgs>
<!-- trim the target assembly -->
<ILLinkArgs>$(ILLinkArgs) --action link $(TargetName)</ILLinkArgs>
<ILLinkArgs Condition="'$(ILLinkRewritePDBs)' == 'true' and Exists('$(ILLinkTrimAssemblySymbols)')">$(ILLinkArgs) -b true</ILLinkArgs>
<ILLinkArgs Condition="'$(ILLinkRewritePDBs)' == 'true' and Exists('$(ILLinkTrimAssemblySymbols)') and '$(DeterministicSourcePaths)' == 'true'">$(ILLinkArgs) --preserve-symbol-paths</ILLinkArgs>
<ILLinkArgs Condition="'$(ILLinkRewritePDBs)' == 'true' and Exists('$(ILLinkTrimInputSymbols)')">$(ILLinkArgs) -b true</ILLinkArgs>
<ILLinkArgs Condition="'$(ILLinkRewritePDBs)' == 'true' and Exists('$(ILLinkTrimInputSymbols)') and '$(DeterministicSourcePaths)' == 'true'">$(ILLinkArgs) --preserve-symbol-paths</ILLinkArgs>
<!-- pass the non-embedded descriptors xml file on the command line -->
<ILLinkArgs Condition="'@(ILLinkDescriptorsLibraryBuildXml)' != ''">$(ILLinkArgs) -x "@(ILLinkDescriptorsLibraryBuildXml->'%(FullPath)', '" -x "')"</ILLinkArgs>
<ILLinkArgs Condition="'$(ILLinkSubstitutionsLibraryBuildXml)' != ''">$(ILLinkArgs) --substitutions "$(ILLinkSubstitutionsLibraryBuildXml)"</ILLinkArgs>
Expand All @@ -235,7 +343,7 @@
<_ILLinkDefaultAction>skip</_ILLinkDefaultAction>
<_ILLinkNoWarn>$(LinkerNoWarn)</_ILLinkNoWarn>
<_ILLinkRemoveSymbols>true</_ILLinkRemoveSymbols>
<_ILLinkRemoveSymbols Condition="'$(ILLinkRewritePDBs)' == 'true' and Exists('$(ILLinkTrimAssemblySymbols)')">false</_ILLinkRemoveSymbols>
<_ILLinkRemoveSymbols Condition="'$(ILLinkRewritePDBs)' == 'true' and Exists('$(ILLinkTrimInputSymbols)')">false</_ILLinkRemoveSymbols>
<_ILLinkPreserveSymbolPaths Condition="'$(_ILLinkRemoveSymbols)' == 'false' and '$(DeterministicSourcePaths)' == 'true'">true</_ILLinkPreserveSymbolPaths>
<_ILLinkIPConstProp Condition="'$(ILLinkDisableIPConstProp)' == 'true'">false</_ILLinkIPConstProp>
<ILLinkArgs Condition="'$(ILLinkSubstitutionsLibraryBuildXml)' != ''">$(ILLinkArgs) --substitutions "$(ILLinkSubstitutionsLibraryBuildXml)"</ILLinkArgs>
Expand All @@ -250,21 +358,12 @@
Condition="'$(_ILLinkHasCustomArgs)' != 'true'" />
</ItemGroup>

<!-- Move the assembly into a subdirectory for ILLink -->
<Move SourceFiles="$(ILLinkTrimAssemblyPath)"
DestinationFolder="$(ILLinkTrimInputPath)">
<Output TaskParameter="MovedFiles" ItemName="FileWrites" />
</Move>

<!-- Move the PDB into a subdirectory for ILLink if we are rewriting PDBs -->
<Move SourceFiles="$(ILLinkTrimAssemblySymbols)"
DestinationFolder="$(ILLinkTrimInputPath)"
Condition="'$(ILLinkRewritePDBs)' == 'true' and Exists('$(ILLinkTrimAssemblySymbols)')">
<Output TaskParameter="MovedFiles" ItemName="FileWrites" />
</Move>

<ItemGroup>
<_DependencyDirectoriesTemp Include="@(ReferencePathWithRefAssemblies->'%(RootDir)%(Directory)')" />
<_ILLinkReference Include="@(_ILLinkReferencedImplementation)"
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ReferenceSourceTarget="ProjectReference" />
<_ILLinkReference Include="@(ReferencePathWithRefAssemblies)"
Condition="'$(_ILLinkUseImplementationReferences)' != 'true' or '%(ReferencePathWithRefAssemblies.ReferenceSourceTarget)' != 'ProjectReference'" />
<_DependencyDirectoriesTemp Include="@(_ILLinkReference->'%(RootDir)%(Directory)')" />
<!-- Remove duplicate directories by batching over them -->
<!-- Add project references first to give precedence to project-specific files -->
<_DependencyDirectories Condition="'%(_DependencyDirectoriesTemp.ReferenceSourceTarget)'=='ProjectReference'" Include="%(_DependencyDirectoriesTemp.Identity)" />
Expand All @@ -285,6 +384,7 @@

<PropertyGroup>
<ILLinkArgs Condition="@(_DependencyDirectories->Count()) > 0">$(ILLinkArgs) -d @(_DependencyDirectories->'"%(Identity)"', ' -d ')</ILLinkArgs>
<ILLinkArgs Condition="'$(_ILLinkUseImplementationReferences)' == 'true'">$(ILLinkArgs) --ignore-substitutions true</ILLinkArgs>
</PropertyGroup>

<ILLink AssemblyPaths="@(_ILLinkAssemblyToTrim)"
Expand Down
14 changes: 0 additions & 14 deletions src/coreclr/vm/wasm/wasi/callhelpers-interp-to-managed.cpp
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