GetNonRandomizedHashCode produces too many collisions for small strings #92556

using System.Diagnostics;
using System.Numerics;

var sw = Stopwatch.StartNew();
const int From = '0';
const int To = 'z';
var hashes = new HashSet<int>();
char[] str = "AA000".ToCharArray();
int totalCollisions = 0;

unsafe
{
    fixed (char* pStr = str)
    {
        for (int ch2 = From; ch2 < To; ch2++)
        for (int ch3 = From; ch3 < To; ch3++)
        for (int ch4 = From; ch4 < To; ch4++)
        {
            pStr[2] = (char)ch2;
            pStr[3] = (char)ch3;
            pStr[4] = (char)ch4;

            int hash = GetNonRandomizedHashCode(pStr, str.Length);
            if (!hashes.Add(hash)) 
                totalCollisions++;
        }
    }
}
sw.Stop();
Console.WriteLine($"Collisions found: {totalCollisions} in {sw.Elapsed.TotalSeconds}");


static unsafe int GetNonRandomizedHashCode(char* src, int length)
{
    uint hash1 = (5381 << 16) + 5381;
    uint hash2 = hash1;
    uint* ptr = (uint*)src;
    while (length > 2)
    {
        length -= 4;
        hash1 = (BitOperations.RotateLeft(hash1, 5) + hash1) ^ ptr[0];
        hash2 = (BitOperations.RotateLeft(hash2, 5) + hash2) ^ ptr[1];
        ptr += 2;
    }
    if (length > 0)
        hash2 = (BitOperations.RotateLeft(hash2, 5) + hash2) ^ ptr[0];
    return (int)(hash1 + (hash2 * 1566083941));
}