JIT: Prevent loop hoisting across volatile reads

src/coreclr/jit/optimizer.cpp

@@ -5376,6 +5376,17 @@ void Compiler::optComputeLoopSideEffectsOfBlock(BasicBlock* blk, FlowGraphNatura
                 }
                 break;
 
+                case GT_IND:
+                case GT_BLK:
+                {
+                    if (tree->AsIndir()->IsVolatile())
+                    {
+                        // On a loop backedge, memory operations in a subsequent iteration may follow this acquire.
+                        memoryHavoc |= memoryKindSet(GcHeap, ByrefExposed);
+                    }
+                }
+                break;
+
                 case GT_STOREIND:
                 case GT_STORE_BLK:
                 {

src/tests/JIT/Regression_o_2/Runtime_133579.cs

@@ -0,0 +1,60 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace Runtime_133579;
+
+using System.Runtime.CompilerServices;
+using System.Threading;
+using TestLibrary;
+using Xunit;
+
+public class Runtime_133579
+{
+    private sealed class Box
+    {
+        public int Value;
+        public int Ready;
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
+    private static int ReadAfterAcquire(Box box, ManualResetEventSlim readerStarted)
+    {
+        readerStarted.Set();
+
+        int value = 0;
+        int seen = 0;
+        while (seen < 2)
+        {
+            value = box.Value;
+            if (Volatile.Read(ref box.Ready) != 0)
+            {
+                seen++;
+            }
+        }
+
+        return value;
+    }
+
+    [OuterLoop]
+    [Fact]
+    [ActiveIssue("https://github.com/dotnet/runtime/issues/41472", typeof(PlatformDetection), nameof(PlatformDetection.IsNotMultithreadingSupported))]
+    public static void OrdinaryLoadIsNotHoistedAcrossVolatileRead()
+    {
+        Box box = new();
+        using ManualResetEventSlim readerStarted = new();
+        int readerResult = -1;
+        Thread reader = new(() =>
+        {
+            readerResult = ReadAfterAcquire(box, readerStarted);
+        });
+        reader.Start();
+
+        readerStarted.Wait();
+        Thread.Sleep(50);
+        box.Value = 42;
+        Volatile.Write(ref box.Ready, 1);
+        reader.Join();
+
+        Assert.Equal(42, readerResult);
+    }
+}