1//===------------------------- dynamic_cast_stress.cpp --------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is dual licensed under the MIT and the University of Illinois Open
6// Source Licenses. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#include <cassert>
11#include <tuple>
12#include "support/timer.hpp"
13
14template <std::size_t Indx, std::size_t Depth>
15struct C
16    : public virtual C<Indx, Depth-1>,
17      public virtual C<Indx+1, Depth-1>
18{
19    virtual ~C() {}
20};
21
22template <std::size_t Indx>
23struct C<Indx, 0>
24{
25    virtual ~C() {}
26};
27
28template <std::size_t Indx, std::size_t Depth>
29struct B
30    : public virtual C<Indx, Depth-1>,
31      public virtual C<Indx+1, Depth-1>
32{
33};
34
35template <class Indx, std::size_t Depth>
36struct makeB;
37
38template <std::size_t ...Indx, std::size_t Depth>
39struct makeB<std::__tuple_indices<Indx...>, Depth>
40    : public B<Indx, Depth>...
41{
42};
43
44template <std::size_t Width, std::size_t Depth>
45struct A
46    : public makeB<typename std::__make_tuple_indices<Width>::type, Depth>
47{
48};
49
50void test()
51{
52    const std::size_t Width = 10;
53    const std::size_t Depth = 5;
54    A<Width, Depth> a;
55    typedef B<Width/2, Depth> Destination;
56//    typedef A<Width, Depth> Destination;
57    Destination *b = nullptr;
58    {
59        timer t;
60        b = dynamic_cast<Destination*>((C<Width/2, 0>*)&a);
61    }
62    assert(b != 0);
63}
64
65int main()
66{
67    test();
68}
69
70/*
71Timing results I'm seeing (median of 3 microseconds):
72
73                          libc++abi    gcc's dynamic_cast
74B<Width/2, Depth> -O3      48.334         93.190           libc++abi 93% faster
75B<Width/2, Depth> -Os      58.535         94.103           libc++abi 61% faster
76A<Width, Depth>   -O3      11.515         33.134           libc++abi 188% faster
77A<Width, Depth>   -Os      12.631         31.553           libc++abi 150% faster
78
79*/
80