84 lines
1.8 KiB
C++
84 lines
1.8 KiB
C++
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// Copyright Oliver Kowalke 2014.
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#ifndef CYCLE_I386_H
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#define CYCLE_I386_H
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#include <algorithm>
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#include <numeric>
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#include <cstddef>
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#include <vector>
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#include <boost/assert.hpp>
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#include <boost/bind.hpp>
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#include <boost/cstdint.hpp>
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#define BOOST_CONTEXT_CYCLE
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typedef boost::uint64_t cycle_type;
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#if _MSC_VER
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inline
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cycle_type cycles()
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{
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cycle_type c;
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__asm {
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cpuid
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rdtsc
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mov dword ptr [c + 0], eax
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mov dword ptr [c + 4], edx
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}
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return c;
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}
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#elif defined(__GNUC__) || \
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defined(__INTEL_COMPILER) || defined(__ICC) || defined(_ECC) || defined(__ICL)
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inline
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cycle_type cycles()
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{
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boost::uint32_t lo, hi;
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__asm__ __volatile__ (
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"xorl %%eax, %%eax\n"
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"cpuid\n"
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::: "%eax", "%ebx", "%ecx", "%edx"
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);
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__asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi) );
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__asm__ __volatile__ (
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"xorl %%eax, %%eax\n"
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"cpuid\n"
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::: "%eax", "%ebx", "%ecx", "%edx"
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);
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return ( cycle_type)hi << 32 | lo;
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}
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#else
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# error "this compiler is not supported"
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#endif
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struct cycle_overhead
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{
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cycle_type operator()()
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{
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cycle_type start( cycles() );
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return cycles() - start;
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}
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};
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inline
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cycle_type overhead_cycle()
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{
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std::size_t iterations( 10);
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std::vector< cycle_type > overhead( iterations, 0);
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for ( std::size_t i( 0); i < iterations; ++i)
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std::generate(
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overhead.begin(), overhead.end(),
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cycle_overhead() );
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BOOST_ASSERT( overhead.begin() != overhead.end() );
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return std::accumulate( overhead.begin(), overhead.end(), 0) / iterations;
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}
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#endif // CYCLE_I386_H
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