[release/8.0-staging] JIT: Fix loop recognition bug in .NET 8

src/coreclr/jit/optimizer.cpp

@@ -1801,7 +1801,7 @@ class LoopSearch
     //
     BasicBlock* FindEntry(BasicBlock* head, BasicBlock* top, BasicBlock* bottom)
     {
-        if (head->bbJumpKind == BBJ_ALWAYS)
+        if ((head->bbJumpKind == BBJ_ALWAYS) && !head->isBBCallAlwaysPairTail())
         {
             if (head->bbJumpDest->bbNum <= bottom->bbNum && head->bbJumpDest->bbNum >= top->bbNum)
             {

src/tests/JIT/Regression/JitBlue/Runtime_108811/Runtime_108811.cs

@@ -0,0 +1,74 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime.CompilerServices;
+using System.Security.Cryptography;
+using System.IO;
+using System.Text;
+using System.Threading;
+using Xunit;
+
+public class Runtime_108811
+{
+    [MethodImpl(MethodImplOptions.AggressiveOptimization)]
+    [Fact]
+    public static int Test()
+    {
+        var hex = "3AE46205A50ED00E7612A91692552B7A";
+        var key = "abcdef1234567890";
+        var iv = "abcdef1234567890";
+        var bytes = Convert.FromHexString(hex);
+        int retval = 100;
+        for (int i = 0; i < 200; i++)
+        {
+            var result = new Runtime_108811().Decrypt(bytes, key, iv, out _);
+            Console.Write($"{result} ");
+            if (result != 9)
+            {
+                retval = -1;
+                break;
+            }
+            Thread.Sleep(10);
+        }
+        Console.WriteLine();
+        return retval;
+    }
+
+    public int Decrypt(byte[] buffer, string key, string iv, out byte[] decryptedData)
+    {
+        int decryptedByteCount = 0;
+        decryptedData = new byte[buffer.Length];
+
+        using var aes = Aes.Create();
+        aes.Mode = CipherMode.CBC;
+        aes.KeySize = 128;
+        aes.Padding = PaddingMode.Zeros;
+
+        var instPwdArray = Encoding.ASCII.GetBytes(key);
+        var instSaltArray = Encoding.ASCII.GetBytes(iv);
+
+        using (var decryptor = aes.CreateDecryptor(instPwdArray, instSaltArray))
+        {
+            using (var memoryStream = new MemoryStream(buffer))
+            {
+                using (var cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
+                {
+                    int read;
+                    do
+                    {
+                        read = cryptoStream.Read(
+                            decryptedData,
+                            decryptedByteCount,
+                            decryptedData.Length - decryptedByteCount);
+                        decryptedByteCount += read;
+                    } while (read != 0);
+                }
+            }
+        }
+        // Found the accurate length of decrypted data
+        while (decryptedData[decryptedByteCount - 1] == 0 && decryptedByteCount > 0)
+            decryptedByteCount--;
+        return decryptedByteCount;
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_108811/Runtime_108811.csproj

@@ -0,0 +1,8 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <Optimize>True</Optimize>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>

src/tests/issues.targets

@@ -3241,6 +3241,9 @@
         <ExcludeList Include="$(XunitTestBinBase)/JIT/Regression/JitBlue/Runtime_90219/Runtime_90219/*">
             <Issue>Loads an assembly from file</Issue>
         </ExcludeList>
+        <ExcludeList Include="$(XunitTestBinBase)/JIT/Regression/JitBlue/Runtime_108811/Runtime_108811/*">
+            <Issue>Requires AES</Issue>
+        </ExcludeList>
     </ItemGroup>
 
     <ItemGroup Condition="'$(TargetArchitecture)' == 'wasm'">