Benchmark.cs

using System;
using System.Runtime.CompilerServices;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

public class Program
{
    static void Main(string[] args)
    {
        // I used .NET Core 3.1 + BDN 0.12.0
        BenchmarkRunner.Run<Program>();
    }

    private static bool AlwaysFalseProp { get; } = SetupField();

    [MethodImpl(MethodImplOptions.NoInlining)]
    private static bool SetupField()
    {
        return false; 
    }

    [Benchmark(Baseline = true)]
    public double Foo0()
    {
        return Math.Sqrt(42);
    }

    [Benchmark]
    [MethodImpl(MethodImplOptions.AggressiveOptimization)]
    public double Foo1()
    {
        if (AlwaysFalseProp)
        {
            Console.WriteLine();
            throw new Exception("unreachable");
        }

        return Math.Sqrt(42);
    }

    [Benchmark]
    public double Foo2()
    {
        if (AlwaysFalseProp)
        {
            Console.WriteLine();
            throw new Exception("unreachable");
        }

        return Math.Sqrt(42);
    }
}

/*

| Method |      Mean |     Error |    StdDev |  Ratio | RatioSD |
|------- |----------:|----------:|----------:|-------:|--------:|
|   Foo0 | 0.0103 ns | 0.0026 ns | 0.0023 ns |   1.00 |    0.00 |
|   Foo1 | 1.0871 ns | 0.0014 ns | 0.0013 ns | 110.79 |   24.92 |
|   Foo2 | 0.0230 ns | 0.0021 ns | 0.0017 ns |   2.49 |    0.61 |

*/