Intrinsify typeof(T).IsGenericType

[Sergio0694]

Contributes to #96898

public static bool Test<T>() => typeof(T).IsGenericType;

Codegen diffs:

; Assembly listing for method Methods:Test[int]():ubyte (FullOpts)
-   sub      rsp, 40
-   mov      rcx, 0x1D980105580      ; 'System.Int32'
-   call     [System.RuntimeType:get_IsGenericType():ubyte:this]
-   add      rsp, 40
+   xor      eax, eax
    ret

; Assembly listing for method Methods:Test[System.Nullable`1[int]]():ubyte (FullOpts)
-   sub      rsp, 40
-   mov      rcx, 0x1D980109298 
-   call     [System.RuntimeType:get_IsGenericType():ubyte:this]
-   nop 
-   add      rsp, 40
+   mov      eax, 1
    ret      

; Assembly listing for method Methods:Test[System.Collections.Generic.KeyValuePair`2[System.__Canon,System.__Canon]]():ubyte (FullOpts)
-   sub      rsp, 40
-   mov      qword ptr [rsp+0x20], rcx
-   mov      rcx, qword ptr [rcx+0x38]
-   mov      rcx, qword ptr [rcx]
-   call     CORINFO_HELP_TYPEHANDLE_TO_RUNTIMETYPE
-   mov      rcx, rax
-   call     [System.RuntimeType:get_IsGenericType():ubyte:this]
-   nop      
-   add      rsp, 40
+   mov      eax, 1
    ret

Note

Reopening from #97148 because I force pushed while that was closed 😅

[AaronRobinsonMSFT]

/cc @davidwrighton

[Sergio0694]

@MihuBot

[Sergio0694]

@MihuBot

[Sergio0694]

@MihuBot

[Sergio0694]

Only non-well-known failing test seems to be:

LibraryImportGenerator.UnitTests.Compiles.ValidateNoGeneratedOutputForNoImport

NuGet.Protocol.Core.Types.FatalProtocolException : An error occurred while retrieving package metadata for 'Microsoft.NETFramework.ReferenceAssemblies.net48.1.0.2' from source 'nuget.org'.
---- System.Net.Http.HttpRequestException : A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond. (api.nuget.org:443)
-------- System.Net.Sockets.SocketException : A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.

Seems unrelated?