[ILLink] trimming null constant propagation #114730
Description
Problem
if (null != null) is not trimmed.
IL after trimming
namespace System.BloatCodeExample
{
public class Foo
{
private static void Main(string[] args)
{
object obj = (object) null;
if (true)
;
if (obj != null)
{
Console.WriteLine("This is bloated code");
Foo.Bloat();
}
Console.WriteLine("hello world");
}
private static void Bloat() => Console.WriteLine("And there could be lot of it");
}
}Repro
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<OutputType>Exe</OutputType>
<TargetFramework>net10.0</TargetFramework>
<RootNamespace>trim_constant_propagation</RootNamespace>
<ImplicitUsings>enable</ImplicitUsings>
<Nullable>enable</Nullable>
<IsTrimmable>true</IsTrimmable>
<PublishTrimmed>true</PublishTrimmed>
<TrimMode>full</TrimMode>
<_ExtraTrimmerArgs> $(_ExtraTrimmerArgs) --dump-dependencies</_ExtraTrimmerArgs>
</PropertyGroup>
<ItemGroup>
<RuntimeHostConfigurationOption Include="Bloat.IsSupported" Value="false" Trim="true" />
</ItemGroup>
</Project>using System.Diagnostics.CodeAnalysis;
using System.Reflection;
[assembly: AssemblyMetadata("IsTrimmable", "True")]
namespace System.BloatCodeExample;
public class Foo
{
[FeatureSwitchDefinition("Bloat.IsSupported")]
private static bool IsBloatSupported { get; } = InitializeIsBloatSupported();
private static bool InitializeIsBloatSupported() => AppContext.TryGetSwitch("Bloat.IsSupported", out bool isSupported) ? isSupported : true;
static void Main(string[] args)
{
var bar = BarFactory();
if (IsBloatSupported)
{
Console.WriteLine("Bloat is supported" + (bar!=null));
}
if (bar != null)
{
Console.WriteLine("This is bloated code");
Bloat();
}
//MethodInfo? bloat = typeof(Foo).GetMethod("Bloat", BindingFlags.NonPublic | BindingFlags.Static);
//Console.WriteLine("Was bloat trimmed ? : " + (bloat == null));
Console.WriteLine("hello world");
}
static void Bloat()
{
Console.WriteLine("And there could be lot of it");
}
static object BarFactory()
{
if (!IsBloatSupported)
{
return null;
}
return new object();
}
}