static Result Block2(uint p0, uint p1) {
    p1 ^= p0;
    p0 = BitOperations.RotateLeft(p0, 20);

    p0 += p1;
    p1 = BitOperations.RotateLeft(p1, 9);

    p1 ^= p0;
    p0 = BitOperations.RotateLeft(p0, 27);

    p0 += p1;
    p1 = BitOperations.RotateLeft(p1, 19);

    return new(p0, p1);
}

static Result Block3(uint p0, uint p1) {
    p1 ^= p0;
    p0 = BitOperations.RotateLeft(p0, 20);

    p0 += p1;
    p1 = BitOperations.RotateLeft(p1, 9);

    p1 ^= p0;
    p0 = BitOperations.RotateLeft(p0, 27);

    p0 += p1;
    p1 = BitOperations.RotateLeft(p1, 19);

    return Result.From(p0, p1);
}

[StructLayout(LayoutKind.Sequential, Pack = 4, Size = 8)]
struct Result {
    uint Hi;
    uint Lo;

    internal static Result From(uint hi, uint lo) {
        ulong temp = (((ulong)hi) << 32) | lo;
        unsafe {
            return *(Result*)Unsafe.AsPointer(ref temp);
        }
    }

    public Result(uint hi, uint lo) {
        Hi = hi;
        Lo = lo;
    }
}

---

<Main>g__Block2|4_4 (UInt32, UInt32)
L0000   push    rax
L0001   xor edx, ecx
L0003   rol ecx, 0x14
L0006   add ecx, edx
L0008   rol edx, 9
L000b   xor edx, ecx
L000d   rol ecx, 0x1b
L0010   add ecx, edx
L0012   rol edx, 0x13
L0015   mov [rsp], ecx
L0018   mov [rsp+4], edx
L001c   mov rax, [rsp]
L0020   add rsp, 8
L0024   ret

<Main>g__Block3|4_5 (UInt32, UInt32)
L0000   xor edx, ecx
L0002   rol ecx, 0x14
L0005   add ecx, edx
L0007   rol edx, 9
L000a   xor edx, ecx
L000c   rol ecx, 0x1b
L000f   add ecx, edx
L0011   rol edx, 0x13
L0014   mov eax, ecx
L0016   shl rax, 0x20
L001a   mov edx, edx
L001c   or  rax, rdx
L001f   ret