[TEST] Test clearing VN after optComputeLoopSideEffects()

src/coreclr/jit/optimizer.cpp

@@ -4304,17 +4304,19 @@ PhaseStatus Compiler::optUnrollLoops()
         // Heuristic: Estimated cost in code size of the unrolled loop.
 
         {
-            ClrSafeInt<unsigned> loopCostSz; // Cost is size of one iteration
-            auto                 tryIndex = loop.lpTop->bbTryIndex;
+            ClrSafeInt<unsigned>    loopCostSz; // Cost is size of one iteration
+            const BasicBlock* const top = loop.lpTop;
 
             // Besides calculating the loop cost, also ensure that all loop blocks are within the same EH
             // region, and count the number of BBJ_RETURN blocks in the loop.
             loopRetCount = 0;
             for (BasicBlock* const block : loop.LoopBlocks())
             {
-                if (block->bbTryIndex != tryIndex)
+                if (!BasicBlock::sameEHRegion(block, top))
                 {
                     // Unrolling would require cloning EH regions
+                    // Note that only non-funclet model (x86) could actually have a loop including a handler
+                    // but not it's corresponding `try`, if its `try` was moved due to being marked "rare".
                     JITDUMP("Failed to unroll loop " FMT_LP ": EH constraint\n", lnum);
                     goto DONE_LOOP;
                 }
@@ -8799,6 +8801,11 @@ bool Compiler::optComputeLoopSideEffectsOfBlock(BasicBlock* blk)
                 }
             }
         }
+
+        // If there is a tree node, clear its ValueNumber. This is to ensure that for those blocks that
+        // are unreachable, which we still handle in this loop but not during Value Numbering,
+        // USE THIS:
+        // stmt->GetRootNode()->gtVNPair.SetBoth(ValueNumStore::NoVN);
     }
 
     if (memoryHavoc != emptyMemoryKindSet)

src/coreclr/jit/valuenum.cpp

@@ -8086,6 +8086,22 @@ PhaseStatus Compiler::fgValueNumber()
     // Compute the side effects of loops.
     optComputeLoopSideEffects();
 
+    // The implementation of optComputeLoopSideEffects() can set some value numbers. These should not be used,
+    // and in fact, the implementation should probably clear them or use a side table or other implementation
+    // to avoid touching the value number field, as for reachable blocks they will get overridden below.
+    {
+        for (BasicBlock* const blk : Blocks())
+        {
+            for (Statement* const stmt : blk->NonPhiStatements())
+            {
+                for (GenTree* const tree : stmt->TreeList())
+                {
+                    tree->gtVNPair.SetBoth(ValueNumStore::NoVN);
+                }
+            }
+        }
+    }
+
     // At the block level, we will use a modified worklist algorithm.  We will have two
     // "todo" sets of unvisited blocks.  Blocks (other than the entry block) are put in a
     // todo set only when some predecessor has been visited, so all blocks have at least one

src/tests/JIT/Regression/JitBlue/Runtime_81675/Runtime_81675.cs

@@ -0,0 +1,68 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+// Generated by Fuzzlyn v1.5 on 2023-02-06 00:41:34
+// Run on X86 Windows
+// Seed: 12611629827253727687
+// Reduced from 444.9 KiB to 1.1 KiB in 00:13:23
+// Hits JIT assert in Release:
+// Assertion failed '!"Jump into the middle of handler region"' in 'Program:Main(Fuzzlyn.ExecutionServer.IRuntime)' during 'Unroll loops' (IL size 131; hash 0xade6b36b; FullOpts)
+// 
+//     File: D:\a\_work\1\s\src\coreclr\jit\fgdiagnostic.cpp Line: 2609
+// 
+public interface I0
+{
+}
+
+public class C0 : I0
+{
+    public sbyte F3;
+}
+
+public class Runtime_81675
+{
+    public static ushort s_11;
+    public static bool[][] s_18;
+    public static C0 s_26;
+    public static short[] s_42;
+    public static void Main()
+    {
+        short vr7 = default(short);
+        for (int vr8 = 0; vr8 < 0; vr8++)
+        {
+            try
+            {
+                System.Console.WriteLine(32767);
+            }
+            finally
+            {
+                I0 vr9 = new C0();
+            }
+        }
+
+        for (int vr10 = 0; vr10 < 0; vr10++)
+        {
+            if (s_18[0][0])
+            {
+                var vr11 = s_26.F3;
+            }
+            else
+            {
+                System.Console.WriteLine(0);
+            }
+
+            if (!((ushort)(-s_11++) >= 0))
+            {
+                vr7 = vr7;
+                try
+                {
+                    vr7 = 0;
+                }
+                finally
+                {
+                    vr7 = s_42[0];
+                }
+            }
+        }
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_81675/Runtime_81675.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <Optimize>True</Optimize>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>