Steps to reproduce:

Originally reported on Discussions here: [https://discussions.unity.com/t/poor-performance-of-synchronization-primitives-lock-volatile-interlocked-in-il2cpp/1489837]

 
{code:java}
int count;
public void TestNormal()
{
    [MethodImpl(MethodImplOptions.NoOptimization)]
    static void Incr(ref int v)
    {
        v+;
    }
    for (int i = 0; i < 100000000; i)
    {
        Incr(ref count);
    }
}
public void TestVolatile()
{
    for (int i = 0; i < 100000000; i+)
    {
        Volatile.Write(ref count, Volatile.Read(ref count) + 1);
    }
}
public void TestInterlocked()
{
    for (int i = 0; i < 100000000; i+)
    {
        Interlocked.Increment(ref count);
    }
}
public void TestLock()
{
    for (int i = 0; i < 100000000; i)
    {
        lock (this)
        {
            count+;
        }
    }
}
{code}
 

Actual results: 

Mono
{code:java}
normal: 142ms
volatile: 143ms
Interlocked: 347ms
lock: 1782ms{code}
IL2CPP
{code:java}
normal: 114ms
volatile: 1310ms
Interlocked: 990ms
lock: 6872ms{code}
.NET 8
{code:java}
normal: 23.43ms
volatile: 21.70ms
Interlocked: 343.34ms
lock: 1,305.52ms{code}
 

Expected results: 

Reproducible with versions: 

6.0 preview

Tested on (OS): 

Windows