[NativeAOT] Properly implement System.Linq.Expressions substitutions according to the recent refactoring

[ivanpovazan]

#89308 introduced a regression for NativeAOT because the changes assumed that ILC trimming can propagate constants over methods. As this is not true, the Ref.Emit backend is not trimmed away by ILC anymore increasing the app size.

This PR fixes this regression, by adjusting the System.Linq.Expressions substitutions to wire DynamicCodeSupported feature switch value to get_CanCompileToIL and get_CanCreateArbitraryDelegates and substitute them with false - avoiding the constant propagation over methods limitation.

Additionally, I cleaned up a few places that had left overs of the removed private feature switches.

Verified that the regression has been fixed by adding a reference to System.Linq.Expressions in the HelloiOS sample and AOTing with and without changes in the PR:

HelloiOS sample	main	this PR
Size on disk (Mb)	53,3	12,14

Thanks @vitek-karas for figuring out the right approach.

@dotnet/ilc-contrib

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Fixes #89527

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Issue Details

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#89308 introduced a regression for NativeAOT because the changes assumed that ILC trimming can propagate constants over methods. As this is not true, the Ref.Emit backend is not trimmed away by ILC anymore increasing the app size.

This PR fixes this regression, by adjusting the System.Linq.Expressions substitutions to wire DynamicCodeSupported feature switch value to get_CanCompileToIL and get_CanCreateArbitraryDelegates and substitute them with false - avoiding the constant propagation over methods limitation.

Additionally, I cleaned up a few places that had left overs of the removed private feature switches.

Thanks @vitek-karas for figuring out the right approach.

@dotnet/ilc-contrib

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Fixes #89527

Author:	ivanpovazan
Assignees:	ivanpovazan
Labels:	area-NativeAOT-coreclr
Milestone:	-

[ivanpovazan]

/azp run runtime-extra-platforms

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[ivanpovazan]

@eerhardt I have measured the impact of this change with https://github.com/aspnet/Benchmarks/tree/main/src/BenchmarksApps/TodosApi on osx-arm64 comparing the main branch and this PR, with dotnet sdk version: 8.0.100-preview.7.23364.32 and locally built framework and ILCompiler packages referenced from the project file via:

  <ItemGroup>
    <FrameworkReference Update="Microsoft.NETCore.App" RuntimeFrameworkVersion="8.0.0-dev" />
    <PackageReference Include="Microsoft.DotNet.ILCompiler" Version="8.0.0-dev" />
  </ItemGroup>

The measurements show the following results:

TodosApi	main	this PR
Size on disk (Mb)	49,99	36,25

These numbers do not match what you posted in: #89527 (comment) but I only have a MacBookPro M1 at hand, so am not able to verify the impact of this change on win-x64. Nevertheless, presented measurements show the expected reduction in size.

I also double-checked the mstat files. confirming the fix:

main branch:

this PR:

[MichalStrehovsky]

Neat!