dynamic_cast_stress.pass.cpp
1.92 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
//===------------------------- dynamic_cast_stress.cpp --------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// UNSUPPORTED: c++03
#include <cassert>
#include <tuple>
#include "support/timer.h"
template <std::size_t Indx, std::size_t Depth>
struct C
: public virtual C<Indx, Depth-1>,
public virtual C<Indx+1, Depth-1>
{
virtual ~C() {}
};
template <std::size_t Indx>
struct C<Indx, 0>
{
virtual ~C() {}
};
template <std::size_t Indx, std::size_t Depth>
struct B
: public virtual C<Indx, Depth-1>,
public virtual C<Indx+1, Depth-1>
{
};
template <class Indx, std::size_t Depth>
struct makeB;
template <std::size_t ...Indx, std::size_t Depth>
struct makeB<std::__tuple_indices<Indx...>, Depth>
: public B<Indx, Depth>...
{
};
template <std::size_t Width, std::size_t Depth>
struct A
: public makeB<typename std::__make_tuple_indices<Width>::type, Depth>
{
};
void test()
{
const std::size_t Width = 10;
const std::size_t Depth = 5;
A<Width, Depth> a;
typedef B<Width/2, Depth> Destination;
// typedef A<Width, Depth> Destination;
Destination *b = nullptr;
{
timer t;
b = dynamic_cast<Destination*>((C<Width/2, 0>*)&a);
}
assert(b != 0);
}
int main()
{
test();
}
/*
Timing results I'm seeing (median of 3 microseconds):
libc++abi gcc's dynamic_cast
B<Width/2, Depth> -O3 48.334 93.190 libc++abi 93% faster
B<Width/2, Depth> -Os 58.535 94.103 libc++abi 61% faster
A<Width, Depth> -O3 11.515 33.134 libc++abi 188% faster
A<Width, Depth> -Os 12.631 31.553 libc++abi 150% faster
*/