[wasm][coreclr] Do not try to probe .ni.dll assemblies

[radekdoulik]

And remove obsolete code around .ni assemblies and executables

[Copilot]

Pull request overview

This PR optimizes assembly loading for WebAssembly by removing native image (.ni.dll) probing, which is no longer supported on WASM and can negatively impact startup performance. The change affects only the CoreCLR binder's assembly probing logic.

Key Changes

• Conditionally excludes .ni.dll from assembly probe candidates when targeting WASM
• Updates loop iteration to use ARRAY_SIZE macro instead of hardcoded value for better maintainability

[radekdoulik]

@jkotas there's still many places related to .ni.dll.

> git grep ni.dll | wc -l  
      45

Would it be worth to remove .ni.dll support in the whole repo?

[vitek-karas]

@grendello was looking into something similar for Android (we don't need/want it there either)... and I assume we would like that for iOS as well.
I know that there was a discussion if we should just remove this functionality from the runtime everywhere (personally I've never seen an app which would use this).

[jkotas]

Would it be worth to remove .ni.dll support in the whole repo?

Yes, I went over the grep output and it looks all dead code, outdated comments, or local workaround for compat (PdbWriter.cs, CallChainProfile.cs, DumpModel.cs - these should be kept). Can you give it a shot to clean up the rest?

[jkotas]

Could you please also delete --out-near-input option for crossgen?

[radekdoulik]

There is still a lookup map in https://github.com/dotnet/runtime/blob/main/src/coreclr/vm/ceeload.h#L1667-L1675 which we can possibly get rid of.

I also kept the related parts of tools/aot/crossgen2/Program.cs as it was also in tools/aot area as the other .cs files. Let me know in case this is also obsolete.

[jkotas]

There is still a lookup map in https://github.com/dotnet/runtime/blob/main/src/coreclr/vm/ceeload.h#L1667-L1675 which we can possibly get rid of.

That is just a comment talking about .ni.dll. The map itself is no specific to .ni.dlls. You can fix the comment so that it is not talking about .ni.dll. "When that happens a.ni.dll stores" -> "When that happens a.dll R2R image stores"

[radekdoulik]

Could you please also delete --out-near-input option for crossgen?

What about the single file compilation, should I remove it too or keep it and not complain about --out-near-input option?

[jkotas]

What about the single file compilation, should I remove it too or keep it and not complain about --out-near-input option?

I do not see --out-near-input and --single-file-compilation used or tested anywhere. All of it looks like dead code to me.

@elinor-fung @davidwrighton Could you please confirm that it is fine to delete this?

[am11]

We can also delete .ni.dll from bringup script (used by new platform ports):

--- a/src/tests/Common/scripts/bringup_runtest.sh
+++ b/src/tests/Common/scripts/bringup_runtest.sh
@@ -424,14 +424,6 @@ function create_core_overlay {
     fi
     cp -f -v "$testDependenciesDir/"xunit* "$coreOverlayDir/" 2>/dev/null
     cp -n -v "$testDependenciesDir/"* "$coreOverlayDir/" 2>/dev/null
-    if [ -f "$coreOverlayDir/mscorlib.ni.dll" ]; then
-        # Test dependencies come from a Windows build, and mscorlib.ni.dll would be the one from Windows
-        rm -f "$coreOverlayDir/mscorlib.ni.dll"
-    fi
-    if [ -f "$coreOverlayDir/System.Private.CoreLib.ni.dll" ]; then
-        # Test dependencies come from a Windows build, and System.Private.CoreLib.ni.dll would be the one from Windows
-        rm -f "$coreOverlayDir/System.Private.CoreLib.ni.dll"
-    fi
     copy_test_native_bin_to_test_root $coreOverlayDir
 }
 
@@ -452,7 +444,7 @@ function precompile_overlay_assemblies {
     if [[ "$doCrossgen" == 1 ]]; then
         local overlayDir=$CORE_ROOT
 
-        filesToPrecompile=$(find -L $overlayDir -iname \*.dll -not -iname \*.ni.dll -not -iname \*-ms-win-\* -type f )
+        filesToPrecompile=$(find -L $overlayDir -iname \*.dll -not -iname \*-ms-win-\* -type f )
         for fileToPrecompile in ${filesToPrecompile}
         do
             local filename=${fileToPrecompile}

These are also not needed?

docs/design/features/jump-stubs.md:scenario. Mscorlib.ni.dll itself has 72 entries in the helper table.
docs/design/features/jump-stubs.md:System.XML.ni.dll has 51 entries, which would lead to 288 and 204 bytes
docs/workflow/editing-and-debugging.md:     * `crossgen` - This is the host program that runs the JIT compiler and produces .NET Native images (`*.ni.dll`)
src/installer/tests/HostActivation.Tests/DependencyResolution/ResolveComponentDependencies.cs:                        .WithAsset("ComponentDependency.ni.dll"))));
src/installer/tests/HostActivation.Tests/DependencyResolution/ResolveComponentDependencies.cs:                .And.HaveStdOutContaining("path: 'ComponentDependency.ni.dll'")
src/libraries/Microsoft.Extensions.DependencyModel/tests/DependencyContextTests.cs:        [InlineData("System.Collections.ni.dll", "System.Collections")]
src/tests/GC/Regressions/v2.0-beta2/445488/445488.cs:*** WARNING: Unable to verify checksum for D:\WINDOWS\Microsoft.NET\Framework\v2.0.x86dbg\assembly\NativeImages_v2.0.x86dbg_32\mscorlib\ab6a82069375373ebc7e85bf2de124cb\mscorlib.ni.dll
src/tests/GC/Regressions/v2.0-beta2/445488/445488.cs:*** ERROR: Module load completed but symbols could not be loaded for D:\WINDOWS\Microsoft.NET\Framework\v2.0.x86dbg\assembly\NativeImages_v2.0.x86dbg_32\mscorlib\ab6a82069375373ebc7e85bf2de124cb\mscorlib.ni.dll
src/tests/GC/Regressions/v2.0-beta2/445488/445488.cs:*** WARNING: Unable to verify checksum for D:\WINDOWS\Microsoft.NET\Framework\v2.0.x86dbg\assembly\NativeImages_v2.0.x86dbg_32\System\08fb29f559b89437a7fc3f4a7dbde9c1\System.ni.dll
src/tests/GC/Regressions/v2.0-beta2/445488/445488.cs:*** ERROR: Module load completed but symbols could not be loaded for D:\WINDOWS\Microsoft.NET\Framework\v2.0.x86dbg\assembly\NativeImages_v2.0.x86dbg_32\System\08fb29f559b89437a7fc3f4a7dbde9c1\System.ni.dll
src/tests/JIT/Performance/CodeQuality/Roslyn/CscBench.cs:        // Some CoreCLR packages have System.Private.CoreLib.ni.dll only
src/tests/JIT/Performance/CodeQuality/Roslyn/CscBench.cs:        string nicorlib = Path.Combine(CoreRoot, "System.Private.CoreLib.ni.dll");

[jkoritzinsky]

I believe --out-near-input and --single-file-compilation were both options in use by @dotnet/samsung.

[tomeksowi]

I believe --out-near-input and --single-file-compilation were both options in use by @dotnet/samsung.

I don't recall using them for RISC-V

[gbalykov]

I believe --out-near-input and --single-file-compilation were both options in use by @dotnet/samsung.

Yes, we use these on Tizen to improve crossgen2 performance

[jkotas]

Yes, we use these on Tizen to improve crossgen2 performance

Do you still need that now that crossgen2 is compiled with native aot? I assume that this was introduced to workaround startup cost of the managed rewrite of crossgen2.

Also, do you depend on the .ni probing that is being deleted in the rest of the PR? We want to delete that since it is adding unnecessary overhead.

[gbalykov]

Do you still need that now that crossgen2 is compiled with native aot? I assume that this was introduced to workaround startup cost of the managed rewrite of crossgen2.

Yes, this is needed to perform crossgen2 initialization only once instead of for each individual dll compilation (#51154 (comment)). We do not use nativeaot on tizen yet, so it's better to keep these. Looks like "single-file-compilation" and "out-near-input" options can be kept mostly unchanged, creating same *.ni.dll as now (or any other file extension), and an extra step will be needed from users of these options to move *.ni.dll to corresponding *.dll (this step will not be part of crossgen2 itself).

Also, do you depend on the .ni probing that is being deleted in the rest of the PR? We want to delete that since it is adding unnecessary overhead.

Having both plain dll and R2R with the same file extension makes harder to distinguish them: instead of checking file extension we'll need to parse PE. And, similarly, both plain dll and R2R can't be kept in the same path if ni.dll is removed. In overall, this removal probably is not too critical, since we updated part of logic during removal of app .ni probing previously (APP_NI_PATHS), and this also will affect only .NET 11 and above.

[jkotas]

@radekdoulik Let's revert the crossgen2 changes for now