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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using Microsoft.Xunit.Performance;
using System;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Reflection;
using System.Collections.Generic;
using Xunit;
[assembly: OptimizeForBenchmarks]
[assembly: MeasureInstructionsRetired]
namespace Inlining
{
public static class NoThrowInline
{
#if DEBUG
public const int Iterations = 1;
#else
public const int Iterations = 100000000;
#endif
static void ThrowIfNull(string s)
{
if (s == null)
ThrowArgumentNullException();
}
static void ThrowArgumentNullException()
{
throw new ArgumentNullException();
}
//
// We expect ThrowArgumentNullException to not be inlined into Bench, the throw code is pretty
// large and throws are extremly slow. However, we need to be careful not to degrade the
// non-exception path performance by preserving registers across the call. For this the compiler
// will have to understand that ThrowArgumentNullException never returns and omit the register
// preservation code.
//
// For example, the Bench method below has 4 arguments (all passed in registers on x64) and fairly
// typical argument validation code. If the compiler does not inline ThrowArgumentNullException
// and does not make use of the "no return" information then all 4 register arguments will have
// to be spilled and then reloaded. That would add 8 unnecessary memory accesses.
//
[MethodImpl(MethodImplOptions.NoInlining)]
static int Bench(string a, string b, string c, string d)
{
ThrowIfNull(a);
ThrowIfNull(b);
ThrowIfNull(c);
ThrowIfNull(d);
return a.Length + b.Length + c.Length + d.Length;
}
[Benchmark]
public static void Test()
{
foreach (var iteration in Benchmark.Iterations)
{
using (iteration.StartMeasurement())
{
Bench("a", "bc", "def", "ghij");
}
}
}
public static int Main()
{
return (Bench("a", "bc", "def", "ghij") == 10) ? 100 : -1;
}
}
}
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