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
16 template <std::size_t Indx, std::size_t Depth>
17 struct C
18 : public virtual C<Indx, Depth-1>,
19 public virtual C<Indx+1, Depth-1>
20 {
~CC21 virtual ~C() {}
22 };
23
24 template <std::size_t Indx>
25 struct C<Indx, 0>
26 {
~CC27 virtual ~C() {}
28 };
29
30 template <std::size_t Indx, std::size_t Depth>
31 struct B
32 : public virtual C<Indx, Depth-1>,
33 public virtual C<Indx+1, Depth-1>
34 {
35 };
36
37 template <class Indx, std::size_t Depth>
38 struct makeB;
39
40 template <std::size_t ...Indx, std::size_t Depth>
41 struct makeB<std::__tuple_indices<Indx...>, Depth>
42 : public B<Indx, Depth>...
43 {
44 };
45
46 template <std::size_t Width, std::size_t Depth>
47 struct A
48 : public makeB<typename std::__make_tuple_indices<Width>::type, Depth>
49 {
50 };
51
test()52 void 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
main()67 int main()
68 {
69 test();
70 }
71
72 /*
73 Timing results I'm seeing (median of 3 microseconds):
74
75 libc++abi gcc's dynamic_cast
76 B<Width/2, Depth> -O3 48.334 93.190 libc++abi 93% faster
77 B<Width/2, Depth> -Os 58.535 94.103 libc++abi 61% faster
78 A<Width, Depth> -O3 11.515 33.134 libc++abi 188% faster
79 A<Width, Depth> -Os 12.631 31.553 libc++abi 150% faster
80
81 */
82