JIT: optimize popped boxes in the importer (dotnet#101303)

Fixes dotnet#82291.

src/coreclr/jit/importer.cpp

@@ -7999,6 +7999,14 @@ void Compiler::impImportBlockCode(BasicBlock* block)
                     /* Append the value to the tree list */
                     goto SPILL_APPEND;
                 }
+                else
+                {
+                    if (op1->IsBoxedValue())
+                    {
+                        JITDUMP("\n CEE_POP box...\n");
+                        gtTryRemoveBoxUpstreamEffects(op1);
+                    }
+                }
 
                 /* No side effects - just throw the <BEEP> thing away */
             }

src/tests/JIT/Regression/JitBlue/Runtime_82291/Runtime_82291.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Runtime.CompilerServices;
+using Xunit;
+
+public class Runtime_82291 
+{
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static bool GetValueOrNull<T>()
+    {
+        if (default(T) != null)
+         return true;
+
+       return false;
+    }    
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static bool GetValueOrNullSlow<T>()
+    {
+        if (default(T) != null)
+         return false;
+
+       return false;
+    }    
+
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static void GetValueOrNullSlow2<T>()
+    {
+        if (default(T) != null)
+         return;
+
+       return;
+    }   
+
+    [Fact]
+    public static void Test()
+    {
+       GetValueOrNull<int>();
+       GetValueOrNullSlow<int>();
+       GetValueOrNullSlow2<int>();
+    } 
+}

src/tests/JIT/Regression/JitBlue/Runtime_82291/Runtime_82291.csproj

@@ -0,0 +1,5 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>