DOTNET_TC_AggressiveTiering doesn't work as expected

[EgorBo]

The default tiering strategy is quite obscure and it's not obvious how to make a small console repro to show a Tier1 codegen for a method without disabling TC completely. DOTNET_TC_AggressiveTiering=1 was desinged to help with that, but it's still not working as expected, example:

using System.Runtime.CompilerServices;

public class Prog
{
    static void Main()
    {
        for (int i = 0; i < 10000000; i++)
            Test();
    }

    [MethodImpl(MethodImplOptions.NoInlining)]
    static void Test() { }
}

Even with DOTNET_TC_AggressiveTiering=1 we never end up requesting a recompilation for Test and it stays in Tier0. I think, with DOTNET_TC_AggressiveTiering we should install call-counting stub synchrously without a delay/timer, so even:

using System.Runtime.CompilerServices;

public class Prog
{
    static void Main()
    {
        for (int i = 0; i < 2; i++)
            Test();
    }

    [MethodImpl(MethodImplOptions.NoInlining)]
    static void Test() { }
}

should print a Tier1 version (or at least, Tier0-instrumented) of Test

[dotnet-policy-service]

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