int32 rotation in ironscheme

bench.cs

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

public class Program
{
    static void Main(string[] args)
    {
        BenchmarkRunner.Run<Program>();
    }

    [Benchmark(Baseline = true)]
    public static void R()
    {
        fxrotate();
    }

    static int fxrotate(int n = 41, int start = 0, int end = 5, int count = 1)
    {
        int num = n;
        int num2 = start;
        int num3 = end;
        int num4 = count;
        int num5 = num3 - num2;
        int num6 = num;
        int num7 = num2;
        int num8 = num3 - num4;
        int num9 = (num6 & ~(-1 << num8)) >> num7;
        int num10 = num;
        int num11 = num2;
        int num12 = num3;
        int num13 = (num10 & ~(-1 << num12)) >> num11;
        int num14 = num;
        int num15 = num2;
        int num16 = num3;
        int num17 = (num9 << num4) | (num13 >> (num5 - num4));
        int num18 = (-1 << num15) & ~(-1 << num16);
        int num19 = num17 << num15;
        int num20 = num14;
        return (num18 & num19) | (~num18 & num20);
    }

    [Benchmark]
    public static void R_opt()
    {
        fxrotate_opt();
    }

    static int fxrotate_opt(int n = 41, int start = 0, int end = 5, int count = 1)
    {
        int r = (-1 << start) & ~(-1 << end);
        return (r &
                (((n & ~(-1 << end - count)) >> start << count) | ((n & ~(-1 << end)) >> start >> (end - start - count))) <<
                start) | (~r & n);
    }
}

cat_spoiler.md

Spoiler

``` Method | Median | StdDev | Scaled | Scaled-SD | ------- |---------- |---------- |------- |---------- | R | 4.7609 ns | 0.0633 ns | 1.00 | 0.00 | R_opt | 4.8622 ns | 0.0339 ns | 1.02 | 0.01 | ```

i4rot.cs

public static object ironscheme.arithmetic.fixnums::fxrotate-bit-field(object n, object start, object end, object count)
{
  int num = (int) n;
  int num2 = (int) start;
  int num3 = (int) end;
  int num4 = (int) count;
  int num5 = num3 - num2;
  int num6 = num;
  int num7 = num2;
  int num8 = num3 - num4;
  int num9 = (num6 & ~(-1 << num8)) >> num7;
  int num10 = num;
  int num11 = num2;
  int num12 = num3;
  int num13 = (num10 & ~(-1 << num12)) >> num11;
  int num14 = num;
  int num15 = num2;
  int num16 = num3;
  int num17 = (num9 << num4) | (num13 >> (num5 - num4));
  int num18 = (-1 << num15) & ~(-1 << num16);
  int num19 = num17 << num15;
  int num20 = num14;
  return (num18 & num19) | (~num18 & num20);
}