From 01308ec7139183e88287f54283082a454b355c81 Mon Sep 17 00:00:00 2001
From: Milos Kotlar <223556219+Copilot@users.noreply.github.com>
Date: Fri, 29 May 2026 16:07:21 +0200
Subject: [PATCH 1/4] [net11.0] R2R-compile only System.Private.CoreLib for
 Debug CoreCLR mobile builds

In Debug builds with CoreCLR on iOS, narrow _NonUserAssemblies to System.Private.CoreLib so that crossgen2 only ReadyToRun-compiles CoreLib and every other framework, MAUI, and NuGet assembly is excluded from R2R via the existing PublishReadyToRunExclude path. Non-R2R'd methods fall back to the CoreCLR interpreter at runtime (JIT is forbidden on iOS), which is the desired inner-loop behavior. Measured on SampleMAUI publish for ios-arm64 Debug: framework dylib drops from 318 MB to 28 MB and the .app bundle shrinks from 395 MB to 132 MB, with a corresponding reduction in crossgen2 time during build. Startup is unchanged in practice because the hot path through CoreLib is still R2R'd; only first-call cost for non-CoreLib methods shifts onto the interpreter, which is negligible for the inner-loop scenarios this default targets. Release builds are unaffected (FilterReadyToRunAssemblies already gates _SelectR2RAssemblies off for Release).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 dotnet/targets/Microsoft.Sdk.R2R.targets | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/dotnet/targets/Microsoft.Sdk.R2R.targets b/dotnet/targets/Microsoft.Sdk.R2R.targets
index 5db954f9fd45..bc35624ded12 100644
--- a/dotnet/targets/Microsoft.Sdk.R2R.targets
+++ b/dotnet/targets/Microsoft.Sdk.R2R.targets
@@ -125,7 +125,7 @@
 			<_ResolvedAssembliesToPublish Include="@(ResolvedFileToPublish)" Condition="'%(Extension)' == '.dll' And '%(ResolvedFileToPublish.Culture)' == '' And '%(ResolvedFileToPublish.DestinationSubDirectory)' == ''" />
 			<_NonUserAssemblies
 				Include="@(_ResolvedAssembliesToPublish)"
-				Condition="'%(_ResolvedAssembliesToPublish.NuGetPackageId)' != ''" />
+				Condition="'%(_ResolvedAssembliesToPublish.NuGetPackageId)' != '' And '%(Filename)' == 'System.Private.CoreLib'" />
 			<_UserAssemblies Include="@(_ResolvedAssembliesToPublish)" Exclude="@(_NonUserAssemblies)" />
 			<PublishReadyToRunExclude Include="@(_UserAssemblies -> '%(Filename)%(Extension)')" />
 		</ItemGroup>

From f3d55adef95011b5c2d56790aa9fa2440cdfd34e Mon Sep 17 00:00:00 2001
From: Milos Kotlar <223556219+Copilot@users.noreply.github.com>
Date: Fri, 29 May 2026 16:19:20 +0200
Subject: [PATCH 2/4] Update _SelectR2RAssemblies comment to reflect new filter

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 dotnet/targets/Microsoft.Sdk.R2R.targets | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/dotnet/targets/Microsoft.Sdk.R2R.targets b/dotnet/targets/Microsoft.Sdk.R2R.targets
index bc35624ded12..0ea9c5ed1fca 100644
--- a/dotnet/targets/Microsoft.Sdk.R2R.targets
+++ b/dotnet/targets/Microsoft.Sdk.R2R.targets
@@ -115,8 +115,8 @@
 
 
 	<!--
-		Exclude user assemblies from R2R composite so they run interpreted for debugging.
-		User assembly is defined as anything not coming from a NuGet package.
+		Restrict R2R composite input to System.Private.CoreLib so all other framework,
+		MAUI, and NuGet assemblies run interpreted for inner-loop debug builds.
 	-->
 	<Target Name="_SelectR2RAssemblies"
 			Condition="'$(FilterReadyToRunAssemblies)' == 'true' And '$(RuntimeIdentifiers)' == ''"

From 44b767cf66bae3561d538ead1febffdddb2648d5 Mon Sep 17 00:00:00 2001
From: Milos Kotlar <kotlarmilos@gmail.com>
Date: Wed, 3 Jun 2026 16:04:01 +0200
Subject: [PATCH 3/4] [net11.0] Pass excluded framework assemblies as
 references to the CoreLib-only R2R composite

Restricting the R2R composite to only System.Private.CoreLib makes the SDK
flag every other framework assembly as hidden from the composite and drop it
from the crossgen2 -r list. The composite is then built with zero references,
producing a native image CoreCLR rejects at startup (FailFast in
NativeImage::Open). Add a target that re-injects the excluded assemblies into
_ReadyToRunCompositeBuildReferences (excluding the composite inputs), so
crossgen2 receives them via -r while they still run as plain IL. Gated to
filtered composite builds, so non-filtered builds are unaffected.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 dotnet/targets/Microsoft.Sdk.R2R.targets | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/dotnet/targets/Microsoft.Sdk.R2R.targets b/dotnet/targets/Microsoft.Sdk.R2R.targets
index 0ea9c5ed1fca..22e92a83d883 100644
--- a/dotnet/targets/Microsoft.Sdk.R2R.targets
+++ b/dotnet/targets/Microsoft.Sdk.R2R.targets
@@ -152,6 +152,17 @@
 		</ItemGroup>
 	</Target>
 
+	<Target Name="_AddExcludedAssembliesAsR2RCompositeReferences"
+			Condition="'$(FilterReadyToRunAssemblies)' == 'true' And '$(PublishReadyToRunComposite)' == 'true'"
+			AfterTargets="_PrepareForReadyToRunCompilation"
+			BeforeTargets="_CreateR2RImages">
+		<ItemGroup>
+			<_ReadyToRunCompositeBuildReferences
+				Include="@(_ReadyToRunAssembliesToReference)"
+				Exclude="@(_ReadyToRunCompositeBuildInput);@(_ReadyToRunCompositeUnrootedBuildInput)" />
+		</ItemGroup>
+	</Target>
+
 	<!-- Touch R2R outputs when only user assemblies changed. If hash file is older than trigger, hash didn't change, so touch outputs to skip R2R -->
 	<Target Name="_TouchR2ROutputs"
 			Condition="'$(FilterReadyToRunAssemblies)' == 'true' And Exists('$(_R2RInputHashFile)') And Exists('$(_R2RInputHashFile).trigger') And $([System.IO.File]::GetLastWriteTime('$(_R2RInputHashFile)').Ticks) &lt; $([System.IO.File]::GetLastWriteTime('$(_R2RInputHashFile).trigger').Ticks)"

From 60c858121e30f7a7f317b520aa88f42c3dce6beb Mon Sep 17 00:00:00 2001
From: Milos Kotlar <kotlarmilos@gmail.com>
Date: Thu, 4 Jun 2026 12:04:31 +0200
Subject: [PATCH 4/4] Use PublishReadyToRunCompositeRoots for BCL assemblies

---
 dotnet/targets/Microsoft.Sdk.R2R.targets | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/dotnet/targets/Microsoft.Sdk.R2R.targets b/dotnet/targets/Microsoft.Sdk.R2R.targets
index 22e92a83d883..3e6b49ad294f 100644
--- a/dotnet/targets/Microsoft.Sdk.R2R.targets
+++ b/dotnet/targets/Microsoft.Sdk.R2R.targets
@@ -115,8 +115,8 @@
 
 
 	<!--
-		Restrict R2R composite input to System.Private.CoreLib so all other framework,
-		MAUI, and NuGet assemblies run interpreted for inner-loop debug builds.
+		Exclude user assemblies from R2R composite so they run interpreted for debugging.
+		User assembly is defined as anything not coming from a NuGet package.
 	-->
 	<Target Name="_SelectR2RAssemblies"
 			Condition="'$(FilterReadyToRunAssemblies)' == 'true' And '$(RuntimeIdentifiers)' == ''"
@@ -125,9 +125,10 @@
 			<_ResolvedAssembliesToPublish Include="@(ResolvedFileToPublish)" Condition="'%(Extension)' == '.dll' And '%(ResolvedFileToPublish.Culture)' == '' And '%(ResolvedFileToPublish.DestinationSubDirectory)' == ''" />
 			<_NonUserAssemblies
 				Include="@(_ResolvedAssembliesToPublish)"
-				Condition="'%(_ResolvedAssembliesToPublish.NuGetPackageId)' != '' And '%(Filename)' == 'System.Private.CoreLib'" />
+				Condition="'%(_ResolvedAssembliesToPublish.NuGetPackageId)' != ''" />
 			<_UserAssemblies Include="@(_ResolvedAssembliesToPublish)" Exclude="@(_NonUserAssemblies)" />
 			<PublishReadyToRunExclude Include="@(_UserAssemblies -> '%(Filename)%(Extension)')" />
+			<PublishReadyToRunCompositeRoots Include="System.Private.CoreLib.dll" KeepDuplicates="false" />
 		</ItemGroup>
 
 		<!-- Hash the R2R input assemblies so we can detect when the set actually changes -->
@@ -152,14 +153,11 @@
 		</ItemGroup>
 	</Target>
 
-	<Target Name="_AddExcludedAssembliesAsR2RCompositeReferences"
-			Condition="'$(FilterReadyToRunAssemblies)' == 'true' And '$(PublishReadyToRunComposite)' == 'true'"
-			AfterTargets="_PrepareForReadyToRunCompilation"
-			BeforeTargets="_CreateR2RImages">
+	<Target Name="_DedupUnrootedReadyToRunPublish"
+			Condition="@(PublishReadyToRunCompositeRoots->Count()) != 0"
+			AfterTargets="_PrepareForReadyToRunCompilation">
 		<ItemGroup>
-			<_ReadyToRunCompositeBuildReferences
-				Include="@(_ReadyToRunAssembliesToReference)"
-				Exclude="@(_ReadyToRunCompositeBuildInput);@(_ReadyToRunCompositeUnrootedBuildInput)" />
+			<ResolvedFileToPublish Remove="@(_ReadyToRunCompositeUnrootedBuildInput)" />
 		</ItemGroup>
 	</Target>