EgorBo

|      Method |        Job |                   Toolchain |      Mean |     Error |    StdDev | Ratio |
|------------ |----------- |----------------------------:|----------:|----------:|----------:|------:|
|     IndexOf | Job-OHKTCB | \Core_Root_Base\corerun.exe | 33.219 ns | 0.0815 ns | 0.0636 ns |  1.00 |
|     IndexOf | Job-QKMCMY | \Core_Root_EGOR\corerun.exe | 16.176 ns | 0.0254 ns | 0.0238 ns |  0.49 |
|             |            |                             |           |           |           |       |
| LastIndexOf | Job-OHKTCB | \Core_Root_Base\corerun.exe | 31.953 ns | 0.0232 ns | 0.0217 ns |  1.00 |
| LastIndexOf | Job-QKMCMY | \Core_Root_EGOR\corerun.exe | 15.704 ns | 0.0374 ns | 0.0312 ns |  0.49 |
|             |            |                             |           |           |           |       |
|    Contains | Job-OHKTCB | \Core_Root_Base\corerun.exe | 27.097 ns | 0.0301 ns | 0.0235 ns |  1.00 |

EgorBo

 Job-PEQKNF : .NET 7.0.0 (42.42.42.42424), X64 RyuJIT

WarmupCount=30

|      Method |                   Toolchain |               source |              str |       Mean |     Error |    StdDev |     Median | Ratio |
|------------ |-----------------------------|--------------------- |----------------- |-----------:|----------:|----------:|-----------:|------:|
|     IndexOf | \Core_Root_Base\corerun.exe | <html(...)html> [60] |          </hhhh> |  50.478 ns | 0.0415 ns | 0.0368 ns |  50.474 ns |  1.00 |
|     IndexOf | \Core_Root_EGOR\corerun.exe | <html(...)html> [60] |          </hhhh> |  15.091 ns | 0.0092 ns | 0.0081 ns |  15.090 ns |  0.30 | 👍
|             |                             |                      |                  |            |           |           |            |       |
| LastIndexOf | \Core_Root_Base\corerun.exe | <html(...)html> [60] |          </hhhh> |  43.979 ns | 0.0783 ns | 0.0732 ns |  43.970 ns |  1.00 |

EgorBo

using System.Diagnostics;
using System.Numerics;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.X86;
using System.Text;

public class Prog

EgorBo

using System.Diagnostics;
using System.Numerics;
using System.Runtime.CompilerServices;
using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.Arm;
using System.Runtime.Intrinsics.X86;
using System.Text;
using BenchmarkDotNet.Attributes;

EgorBo

using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.X86;
using BenchmarkDotNet.Attributes;


//BenchmarkDotNet=v0.13.1, OS=Windows 10.0.19042.1415 (20H2/October2020Update)
//Intel Core i7-8700K CPU 3.70GHz (Coffee Lake), 1 CPU, 12 logical and 6 physical cores

EgorBo

using System;
using System.IO;

static class Program
{
    static void WL(string str) => File.AppendAllText(@"C:\prj\t.cs", str + Environment.NewLine);

    static void Main()
    {
        string[] values =

EgorBo

using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

public class Program
{
    static ref byte GetRawData(object obj) => 
        ref Unsafe.As<RawData>(obj).Data;

    [StructLayout(LayoutKind.Sequential)]

EgorBo

using System;
using System.Diagnostics;
using System.Runtime.CompilerServices;
using System.Threading;

public interface IInterface1 { IInterface2 GetInterface(); }
public interface IInterface2 { IInterface3 GetInterface(); }
public interface IInterface3 { IInterface4 GetInterface(); }
public interface IInterface4 { void SayHello(); }

EgorBo

using System;
using System.IO;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Threading;

public class Program
{
    public static void Main()
    {

EgorBo

Dynamic PGO in .NET 6.0

Dynamic PGO (Profile-guided optimization) is a JIT-compiler optimization technique that allows JIT to collect additional information about surroundings (aka profile) in tier0 codegen in order to rely on it later during promotion from tier0 to tier1 for hot methods to make them even more efficient.

What exactly PGO can optimize for us?

1. Profile-driving inlining - inliner relies on PGO data and can be very aggressive for hot paths and care less about cold ones, see dotnet/runtime#52708 and dotnet/runtime#55478. A good example where it has visible effects is this StringBuilder benchmark:

2. Guarded devirtualization - most monomorphic virtual/interface calls can be devirtualized using PGO data, e.g.:

void DisposeMe(IDisposable d)