Have COND_JUMP handling check for gtEffectiveVal

src/coreclr/jit/importer.cpp

@@ -7373,15 +7373,17 @@ void Compiler::impImportBlockCode(BasicBlock* block)
                 // fall through
 
             COND_JUMP:
-
+            {
                 /* Fold comparison if we can */
 
                 op1 = gtFoldExpr(op1);
 
                 /* Try to fold the really simple cases like 'iconst *, ifne/ifeq'*/
                 /* Don't make any blocks unreachable in import only mode */
 
-                if (op1->gtOper == GT_CNS_INT)
+                GenTree* effectiveOp1 = op1->gtEffectiveVal();
+
+                if (effectiveOp1->OperIs(GT_CNS_INT))
                 {
                     /* gtFoldExpr() should prevent this as we don't want to make any blocks
                        unreachable under compDbgCode */
@@ -7393,7 +7395,7 @@ void Compiler::impImportBlockCode(BasicBlock* block)
 
                     if (block->KindIs(BBJ_COND))
                     {
-                        bool const      isCondTrue   = op1->AsIntCon()->gtIconVal != 0;
+                        bool const      isCondTrue   = effectiveOp1->AsIntCon()->gtIconVal != 0;
                         FlowEdge* const removedEdge  = isCondTrue ? block->GetFalseEdge() : block->GetTrueEdge();
                         FlowEdge* const retainedEdge = isCondTrue ? block->GetTrueEdge() : block->GetFalseEdge();
 
@@ -7463,6 +7465,12 @@ void Compiler::impImportBlockCode(BasicBlock* block)
                         }
                     }
 
+                    if (!op1->OperIs(GT_CNS_INT))
+                    {
+                        // Ensure we spill any side effects and don't drop them
+                        op1 = gtUnusedValNode(op1);
+                        goto SPILL_APPEND;
+                    }
                     break;
                 }
 
@@ -7477,6 +7485,7 @@ void Compiler::impImportBlockCode(BasicBlock* block)
                 }
 
                 goto SPILL_APPEND;
+            }
 
             case CEE_CEQ:
                 oper = GT_EQ;

src/tests/JIT/Regression/JitBlue/Runtime_103600/Runtime_103600.cs

@@ -0,0 +1,52 @@
+// 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 Xunit;
+
+// Generated by Fuzzlyn v1.6 on 2024-06-16 15:10:23
+// Run on X64 Windows
+// Seed: 6886681321438315426
+// Reduced from 30.1 KiB to 0.3 KiB in 00:01:11
+// Hits JIT assert in Release:
+// Assertion failed 'cond == test->AsOp()->gtOp1' in 'Program:Main(Fuzzlyn.ExecutionServer.IRuntime)' during 'Update flow graph early pass' (IL size 27; hash 0xade6b36b; FullOpts)
+//
+//     File: D:\a\_work\1\s\src\coreclr\jit\fgopt.cpp Line: 5447
+//
+public class Runtime_103600
+{
+    [Fact]
+    public static int TestEntryPoint()
+    {
+        int result = 0;
+
+        try
+        {
+            Test();
+        }
+        catch (NullReferenceException)
+        {
+            result = 100;
+        }
+
+        return result;
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static void Test()
+    {
+        ulong[] vr0 = default(ulong[]);
+
+        if (0 > vr0[0])
+        {
+            vr0 = vr0;
+        }
+        else
+        {
+            vr0 = new ulong[]{0};
+        }
+
+        vr0[0] = vr0[0];
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_103600/Runtime_103600.csproj

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