LinqPad to reproduce https://twitter.com/badamczewski01/status/1388853741831565316

Sum.cs

void Main()
{
    var summary = BenchmarkRunner.Run<BenchmarkSum>();
}

[BenchmarkDotNet.Attributes.MemoryDiagnoser]
public class BenchmarkSum
{
    [Benchmark]
    public void Slow()
    {
        SumSlow(8192, 8, 9);
    }

    [Benchmark]
    public void Fast()
    {
        SumFast(8192, 8, 9);
    }

    [Benchmark]
    public void FastAlloc()
    {
        SumFastAlloc(8192, 8, 9);
    }

    [Benchmark]
    public void M2()
    {
        M2(8192, 8, 9);
    }

    int SumSlow(int size, int x, int y)
    {
        int sum = 0;
        int hoist = x * y;
        for (int i = 0; i < size; i++)
        {
            try { sum += hoist; }
            catch { }
        }
        return sum;
    }

    int SumFast(int size, int x, int y)
    {
        int sum = 0;
        int hoist = x * y;
        int[] tmp = new int[1];
        for (int i = 0; i < size; i++)
        {
            try
            {
                tmp[0] = hoist;
                sum += tmp[0];
            }
            catch { }
        }
        return sum;
    }

    int SumFastAlloc(int size, int x, int y)
    {
        int sum = 0;
        int hoist = x * y;
        Span<int> tmp = stackalloc int[1];
        for (int i = 0; i < size; i++)
        {
            try
            {
                tmp[0] = hoist;
                sum += tmp[0];
            }
            catch { }
        }
        return sum;
    }
    
    int M2(int size, int x, int y)
    {
        int sum = 0;
        Span<int> tmp = stackalloc int[1];
        tmp[0] = x* y;
        for (int i = 0; i < size; i++)
        {
            try {
                sum += tmp[0];}
            catch {}
        }
        return sum;
    }
}

Added Stackalloc.

change move.