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// UNSUPPORTED: c++98, c++03
11
12#include <cassert>
13#include <tuple>
14#include "support/timer.hpp"
15
16template <std::size_t Indx, std::size_t Depth>
17struct C
18    : public virtual C<Indx, Depth-1>,
19      public virtual C<Indx+1, Depth-1>
20{
21    virtual ~C() {}
22};
23
24template <std::size_t Indx>
25struct C<Indx, 0>
26{
27    virtual ~C() {}
28};
29
30template <std::size_t Indx, std::size_t Depth>
31struct B
32    : public virtual C<Indx, Depth-1>,
33      public virtual C<Indx+1, Depth-1>
34{
35};
36
37template <class Indx, std::size_t Depth>
38struct makeB;
39
40template <std::size_t ...Indx, std::size_t Depth>
41struct makeB<std::__tuple_indices<Indx...>, Depth>
42    : public B<Indx, Depth>...
43{
44};
45
46template <std::size_t Width, std::size_t Depth>
47struct A
48    : public makeB<typename std::__make_tuple_indices<Width>::type, Depth>
49{
50};
51
52void test()
53{
54    const std::size_t Width = 10;
55    const std::size_t Depth = 5;
56    A<Width, Depth> a;
57    typedef B<Width/2, Depth> Destination;
58//    typedef A<Width, Depth> Destination;
59    Destination *b = nullptr;
60    {
61        timer t;
62        b = dynamic_cast<Destination*>((C<Width/2, 0>*)&a);
63    }
64    assert(b != 0);
65}
66
67int main()
68{
69    test();
70}
71
72/*
73Timing results I'm seeing (median of 3 microseconds):
74
75                          libc++abi    gcc's dynamic_cast
76B<Width/2, Depth> -O3      48.334         93.190           libc++abi 93% faster
77B<Width/2, Depth> -Os      58.535         94.103           libc++abi 61% faster
78A<Width, Depth>   -O3      11.515         33.134           libc++abi 188% faster
79A<Width, Depth>   -Os      12.631         31.553           libc++abi 150% faster
80
81*/
82