Enable Mono for using faster invoke stubs

[steveharter]

Add support for Mono to emit faster invoke stubs for both the new invoke APIs added in #88415 as well as standard invoke.

Replacement for closed issue #88952

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Issue Details

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[Verifying Tests]

Author:	steveharter
Assignees:	steveharter
Labels:	area-System.Reflection
Milestone:	-

[EgorBo]

just curious - is it possible to avoid boxed Nullable<> in the first place? I guess it's not possible to create ones with plain C# (where boxed nullables are boxed as just plain values)

[steveharter]

just curious - is it possible to avoid boxed Nullable<> in the first place? I guess it's not possible to create ones with plain C# (where boxed nullables are boxed as just plain values)

It's done this way primarily for the interpreted path, which doesn't use emit and is located in the native runtime -- it either needs to be passed a pointer to a nullable or have special logic that creates a nullable from the null \ <T> input. The design we went with keeps the native code (and also emit) to be minimal, so we went with first approach where we pass in a pointer to a nullable which is triggered from the library reflection invoke code. The most straightforward way of doing that is to box a nullable.

Also, for both the interpreted path and the various emit paths we also wanted to normalize the object arg input and have the same validation\fix-up code so we can select the strategy without having to do special fix-ups and validation per strategy type.

[vargaz]

Why is this needed ?

[steveharter]

Thanks for this. With the last commit, it is no longer necessary. Also removed from core CLR.

It was necessary previously since the Opcodes.UnboxAny would throw a InvalidCastException for UIntPtr arguments.