[Java.Interop] Avoid some method group conversions #1050
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Context: https://learn.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-11#improved-method-group-conversion-to-delegate Context: dotnet#1034 Context: dotnet/roslyn#62832 C#11 introduced a "slight semantic" change with "Improved method group conversion to delegate": > The C# 11 compiler caches the delegate object created from a method > group conversion and reuses that single delegate object. The result of optimization is that for current `generator`-emitted code such as: static Delegate GetFooHandler () { if (cb_foo == null) cb_foo = JNINativeWrapper.CreateDelegate ((_JniMarshal_PP_V) n_Foo); return cb_foo; } The `(_JniMarshal_PP_V) n_Foo` expression is a "method group conversion", and under C#11 the generated IL is *larger*, as the delegate instance is *cached* in case it is needed again. However in *our* case we *know* the delegate instance won't be needed again, not in this scope, so all this "optimization" does *for us* is increase the size of our binding assemblies when built under C#11. Review `src/Java.Interop` for use of `new JniNativeMethodRegistration` and replace "cast-style" method group conversions `(D) M` to "new-style" delegate conversions `new D(M)`. This explicitly "opts-out" of the C#11 optimization.
jpobst
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Oct 11, 2022
jonpryor
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Nov 1, 2022
Fixes: dotnet/java-interop#1034 Fixes: dotnet/java-interop#1051 Context: 938b2cb Changes: dotnet/java-interop@e1ee4b1...5318261 * dotnet/java-interop@53182615: [build] Update Microsoft.* NuGet package versions (dotnet/java-interop#1055) * dotnet/java-interop@8e18c909: [generator] Avoid C#11 delegate cache overhead. (dotnet/java-interop#1053) * dotnet/java-interop@2d8b6d24: [generator] More AttributeTargets on SupportedOSPlatformAttribute (dotnet/java-interop#1054) * dotnet/java-interop@7dfbab67: [generator] Add [SupportedOSPlatform] to bound constant fields (dotnet/java-interop#1038) * dotnet/java-interop@1720628a: [generator] Mark generated .cs files as generated (dotnet/java-interop#1052) * dotnet/java-interop@f498fcf5: [Java.Interop] Avoid some method group conversions (dotnet/java-interop#1050) * dotnet/java-interop@16e1ecd4: [build] Use $(VSINSTALLDIR), not $(VSINSTALLROOT) (dotnet/java-interop#1048) * dotnet/java-interop@8e4c7d20: [Hello-Core] Add "low level" sample. (dotnet/java-interop#1047) Additionally, remove `$(LangVersion)`=10 from `Mono.Android.csproj`, which was a hack to work around a size regression due to delegate caching in C# 11; see also 938b2cb, dotnet/java-interop@8e18c909. Co-authored-by: Jonathan Pobst <[email protected]>
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Context: https://learn.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-11#improved-method-group-conversion-to-delegate Context: #1034 Context: dotnet/roslyn#62832
C#11 introduced a "slight semantic" change with "Improved method group conversion to delegate":
The result of optimization is that for current
generator-emitted code such as:The
(_JniMarshal_PP_V) n_Fooexpression is a "method group conversion", and under C#11 the generated IL is larger, as the delegate instance is cached in case it is needed again.However in our case we know the delegate instance won't be needed again, not in this scope, so all this "optimization" does for us is increase the size of our binding assemblies when built under C#11.
Review
src/Java.Interopfor use ofnew JniNativeMethodRegistrationand replace "cast-style" method group conversions(D) Mto "new-style" delegate conversionsnew D(M). This explicitly "opts-out" of the C#11 optimization.