BranchElimination2.cs

public class BranchElimination
    {
        int[] aTab;
        int[] xTab;
        int[] xInpTab;

        [GlobalSetup]
        public void Global()
        {
            aTab = new int[5] { 10, 20, 30, 40, 50 };
            xTab = new int[4] { 100, 200, 300, 400 };

            int[] rndVals = new int[] { 50, 100, 150, 200, 250, 300, 350, 400, 450, 500 };

            Random rnd = new Random();

            xInpTab = new int[1024 * 4];
            for(int i = 0; i < 1024 * 4; i++)
            {
                xInpTab[i] = rndVals[rnd.Next(0, 10)];
            }
        }

        [BenchmarkCategory("1"), Benchmark(Baseline = true)]
        public int Branch()
        {
            int cnt = 0;
            for (int i = 0; i < xInpTab.Length; i++)
            {
                var x = xInpTab[i];
                var a = 0;

                if (x < xTab[2])
                {
                    a = aTab[2];
                }
                else if (x < xTab[3])
                {
                    a = aTab[3];
                }
                else
                {
                    a = aTab[4];
                }

                cnt += a;
            }

            return cnt;
        }

        [BenchmarkCategory("1"), Benchmark]
        public int Branchless()
        {
            int cnt = 0;
            for (int i = 0; i < xInpTab.Length; i++)
            {
                var x = xInpTab[i];
 
                uint x_lt_x1 = (uint)((x - xTab[2]) >> 31);
                uint x_lt_x2 = (uint)((x - xTab[3]) >> 31);
                var result_0 = (int)((x_lt_x2 & aTab[3]) | (~x_lt_x2 & aTab[4]));
                var result   = (int)((x_lt_x1 & aTab[2]) | (~x_lt_x1 & result_0));

                cnt += result;
            }

            return cnt;
        }
    }