ReverseBug.cs

using System;

public class Program 
{
    public static int[] Reverse(int[] values) 
    {
        int N = values.Length;
        for (var i = 0; i < N; i++)
        {
            values[i] = values[N-i];
            values[N-i] = values[i];
        }

        return values;
    }

    public static void Main() 
    {
        int[] values = new [] {1,2,3,4};
        int[] reverse = Reverse(values);

        for (var i = 0; i < values.Length; i++)
        {
            Console.WriteLine($"Reverse: {values[i]}, {reverse[i]}");
        }
    }
}

​ReverseBug.il

.class private auto ansi '<Module>'
{
} // end of class <Module>

.class public auto ansi beforefieldinit Program
    extends [System.Private.CoreLib]System.Object
{
    // Methods
    .method public hidebysig static 
        int32[] Reverse (
            int32[] values
        ) cil managed 
    {
        // Method begins at RVA 0x2050
        // Code size 45 (0x2d)
        .maxstack 5
        .locals init (
            [0] int32,
            [1] int32,
            [2] bool,
            [3] int32[]
        )

        IL_0000: nop
        IL_0001: ldarg.0
        IL_0002: ldlen
        IL_0003: conv.i4
        IL_0004: stloc.0
        IL_0005: ldc.i4.0
        IL_0006: stloc.1
        // sequence point: hidden
        IL_0007: br.s IL_001f
        // loop start (head: IL_001f)
            IL_0009: nop
            IL_000a: ldarg.0
            IL_000b: ldloc.1
            IL_000c: ldarg.0
            IL_000d: ldloc.0
            IL_000e: ldloc.1
            IL_000f: sub
            IL_0010: ldelem.i4
            IL_0011: stelem.i4
            IL_0012: ldarg.0
            IL_0013: ldloc.0
            IL_0014: ldloc.1
            IL_0015: sub
            IL_0016: ldarg.0
            IL_0017: ldloc.1
            IL_0018: ldelem.i4
            IL_0019: stelem.i4
            IL_001a: nop
            IL_001b: ldloc.1
            IL_001c: ldc.i4.1
            IL_001d: add
            IL_001e: stloc.1

            IL_001f: ldloc.1
            IL_0020: ldloc.0
            IL_0021: clt
            IL_0023: stloc.2
            // sequence point: hidden
            IL_0024: ldloc.2
            IL_0025: brtrue.s IL_0009
        // end loop

        IL_0027: ldarg.0
        IL_0028: stloc.3
        IL_0029: br.s IL_002b

        IL_002b: ldloc.3
        IL_002c: ret
    } // end of method Program::Reverse

    .method public hidebysig static 
        void Main () cil managed 
    {
        // Method begins at RVA 0x208c
        // Code size 79 (0x4f)
        .maxstack 4
        .locals init (
            [0] int32[],
            [1] int32[],
            [2] int32,
            [3] bool
        )

        IL_0000: nop
        IL_0001: ldc.i4.4
        IL_0002: newarr [System.Private.CoreLib]System.Int32
        IL_0007: dup
        IL_0008: ldtoken field valuetype '<PrivateImplementationDetails>'/'__StaticArrayInitTypeSize=16' '<PrivateImplementationDetails>'::'1456763F890A84558F99AFA687C36B9037697848'
        IL_000d: call void [System.Private.CoreLib]System.Runtime.CompilerServices.RuntimeHelpers::InitializeArray(class [System.Private.CoreLib]System.Array, valuetype [System.Private.CoreLib]System.RuntimeFieldHandle)
        IL_0012: stloc.0
        IL_0013: ldloc.0
        IL_0014: call int32[] Program::Reverse(int32[])
        IL_0019: stloc.1
        IL_001a: ldc.i4.0
        IL_001b: stloc.2
        // sequence point: hidden
        IL_001c: br.s IL_0044
        // loop start (head: IL_0044)
            IL_001e: nop
            IL_001f: ldstr "Reverse: {0}, {1}"
            IL_0024: ldloc.0
            IL_0025: ldloc.2
            IL_0026: ldelem.i4
            IL_0027: box [System.Private.CoreLib]System.Int32
            IL_002c: ldloc.1
            IL_002d: ldloc.2
            IL_002e: ldelem.i4
            IL_002f: box [System.Private.CoreLib]System.Int32
            IL_0034: call string [System.Private.CoreLib]System.String::Format(string, object, object)
            IL_0039: call void [System.Console]System.Console::WriteLine(string)
            IL_003e: nop
            IL_003f: nop
            IL_0040: ldloc.2
            IL_0041: ldc.i4.1
            IL_0042: add
            IL_0043: stloc.2

            IL_0044: ldloc.2
            IL_0045: ldloc.0
            IL_0046: ldlen
            IL_0047: conv.i4
            IL_0048: clt
            IL_004a: stloc.3
            // sequence point: hidden
            IL_004b: ldloc.3
            IL_004c: brtrue.s IL_001e
        // end loop

        IL_004e: ret
    } // end of method Program::Main

    .method public hidebysig specialname rtspecialname 
        instance void .ctor () cil managed 
    {
        // Method begins at RVA 0x20e7
        // Code size 8 (0x8)
        .maxstack 8

        IL_0000: ldarg.0
        IL_0001: call instance void [System.Private.CoreLib]System.Object::.ctor()
        IL_0006: nop
        IL_0007: ret
    } // end of method Program::.ctor

} // end of class Program

.class private auto ansi sealed '<PrivateImplementationDetails>'
    extends [System.Private.CoreLib]System.Object
{
    .custom instance void [System.Private.CoreLib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = (
        01 00 00 00
    )
    // Nested Types
    .class nested private explicit ansi sealed '__StaticArrayInitTypeSize=16'
        extends [System.Private.CoreLib]System.ValueType
    {
        .pack 1
        .size 16

    } // end of class __StaticArrayInitTypeSize=16


    // Fields
    .field assembly static initonly valuetype '<PrivateImplementationDetails>'/'__StaticArrayInitTypeSize=16' '1456763F890A84558F99AFA687C36B9037697848' at I_00002908

} // end of class <PrivateImplementationDetails>

​​.sharplab.json

{
    "version": 1,
    "target": "IL",
    "mode": "Debug"
}

https://sharplab.io/#gist:00f7dbad4c1c407e005238c85eeb65de