504bc07d1a
This is needed when running the tests in Freestanding mode, where main() isn't treated specially. In Freestanding, main() doesn't get mangled as extern "C", so whatever runtime we're using fails to find the entry point. One way to solve this problem is to define a symbol alias from __Z4mainiPPc to _main, however this requires all definitions of main() to have the same mangling. Hence this commit.
83 lines
2 KiB
C++
83 lines
2 KiB
C++
//===------------------------- dynamic_cast_stress.cpp --------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// UNSUPPORTED: c++03
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#include <cassert>
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#include <tuple>
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#include "support/timer.h"
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template <std::size_t Indx, std::size_t Depth>
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struct C
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: public virtual C<Indx, Depth-1>,
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public virtual C<Indx+1, Depth-1>
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{
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virtual ~C() {}
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};
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template <std::size_t Indx>
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struct C<Indx, 0>
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{
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virtual ~C() {}
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};
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template <std::size_t Indx, std::size_t Depth>
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struct B
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: public virtual C<Indx, Depth-1>,
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public virtual C<Indx+1, Depth-1>
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{
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};
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template <class Indx, std::size_t Depth>
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struct makeB;
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template <std::size_t ...Indx, std::size_t Depth>
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struct makeB<std::__tuple_indices<Indx...>, Depth>
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: public B<Indx, Depth>...
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{
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};
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template <std::size_t Width, std::size_t Depth>
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struct A
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: public makeB<typename std::__make_tuple_indices<Width>::type, Depth>
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{
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};
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void test()
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{
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const std::size_t Width = 10;
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const std::size_t Depth = 5;
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A<Width, Depth> a;
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typedef B<Width/2, Depth> Destination;
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// typedef A<Width, Depth> Destination;
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Destination *b = nullptr;
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{
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timer t;
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b = dynamic_cast<Destination*>((C<Width/2, 0>*)&a);
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}
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assert(b != 0);
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}
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int main(int, char**)
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{
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test();
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return 0;
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}
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/*
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Timing results I'm seeing (median of 3 microseconds):
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libc++abi gcc's dynamic_cast
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B<Width/2, Depth> -O3 48.334 93.190 libc++abi 93% faster
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B<Width/2, Depth> -Os 58.535 94.103 libc++abi 61% faster
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A<Width, Depth> -O3 11.515 33.134 libc++abi 188% faster
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A<Width, Depth> -Os 12.631 31.553 libc++abi 150% faster
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*/
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