Typeforward System.Runtime.CompilerServices.Unsafe to SPC for netcore

[marek-safar]

Right now we have two different implementations of System.Runtime.CompilerServices.Unsafe type. One in System.Runtime.CompilerServices assembly and the second one in System.Private.Corelib assembly. We should unify them and type forward to SPC implementation. This would reduce code duplication and simplify JIT/AOT maintenance for the intrinsics as well as drop dependency on IL compiler for libraries build.

[stephentoub]

To clarify, this is more than type-forwarding:

• The one in corelib is actually Internal.Runtime.CompilerServices.Unsafe
• They do not currently have the same surface area. Methods have only been added to the internal one as they're needed.

[marek-safar]

this is more than type-forwarding

Yep, that's why I wrote "We should unify them and type forward ..."

They do not currently have the same surface area.

Is there any reason why they should not have the same surface area? Does the lack of lack of C# declaration in SPC buy us anything if they are runtime intrinsics anyway?

[stephentoub]

Does the lack of lack of C# declaration in SPC buy us anything if they are runtime intrinsics anyway?

I don't understand. The ones not declared in C# also aren't implemented in the runtime.

[marek-safar]

I meant that we have 3 different types of implementations (intrinsics, SPC/C# version, SRCU/IL version). I see that SPC version is missing about 2 different method sets (e.g. Subtract* with overloads). I didn't look closely but I expect the missing methods can be implemented as C# code in SPC which would expand the non-intrinsics methods in SPC and we could type-forward. I don't know what is the history about having only a subset of them available in SPC only though and if there is an important reason for that but as of today not all Unsafe methods in SPC are implemented as intrinsics for all codegens.

[stephentoub]

I don't know what is the history about having only a subset of them available in SPC

They were just added as they were needed by corelib.