[release/6.0] [mono][jit] Fix an infinite loop in the abcrem pass.

src/mono/mono/mini/abcremoval.c

@@ -493,7 +493,7 @@ get_relations_from_previous_bb (MonoVariableRelationsEvaluationArea *area, MonoB
 			symmetric_relation = MONO_SYMMETRIC_RELATION (branch_relation);
 
 			/* FIXME: Other compare opcodes */
-			if (compare->opcode == OP_ICOMPARE) {
+			if (compare->opcode == OP_ICOMPARE && compare->sreg1 != compare->sreg2) {
 				relations->relation1.variable = compare->sreg1;
 				relations->relation1.relation.relation = branch_relation;
 				relations->relation1.relation.related_value.type = MONO_VARIABLE_SUMMARIZED_VALUE;

src/tests/JIT/Regression/JitBlue/Runtime_71592/test71592.cs

@@ -0,0 +1,33 @@
+// 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.Threading.Tasks;
+
+public class Test
+{
+    public int foo;
+
+    public override bool Equals(object o) => false;
+    public override int GetHashCode() => 0;
+
+    public static bool operator ==(Test t1, Test t2) {
+        if (ReferenceEquals(t1, t1))
+            return true;
+        return t1.foo == t2.foo;
+    }
+
+    public static bool operator !=(Test t1, Test t2) {
+        if (ReferenceEquals(t1, t1))
+            return true;
+        return t1.foo == t2.foo;
+    }
+
+    public static int Main () {
+        var t1 = new Test () { foo = 1 };
+        var t2 = new Test () { foo = 2 };
+        if (t1 == t2)
+            return 100;
+        return 100;
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_71592/test71592.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <CLRTestPriority>0</CLRTestPriority>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="test71592.cs" />
+  </ItemGroup>
+</Project>