cpu.h

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2020, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */

#pragma once

#include <mrpt/core/common.h>
#include <array>
#include <string>

namespace mrpt::cpu
{
/** OS-portable set of CPU feature definitions, for usage in mrpt::cpu::supports
 * \ingroup mrpt_core_grp
 */
enum class feature : unsigned int
{
    MMX = 0,
    POPCNT,
    SSE,
    SSE2,
    SSE3,
    SSSE3,
    SSE4_1,
    SSE4_2,
    AVX,
    AVX2,
    // ---- end of list ----
    FEATURE_COUNT
};

namespace internal
{
/** Auxiliary class. Users should use mrpt::core::supports() instead.
 * \ingroup mrpt_core_grp
 */
class CPU_analyzer
{
   public:
    static CPU_analyzer& Instance() noexcept;

    std::array<
        bool, static_cast<std::size_t>(mrpt::cpu::feature::FEATURE_COUNT)>
        feat_detected;

    inline bool& feat(mrpt::cpu::feature f) noexcept
    {
        return feat_detected[static_cast<std::size_t>(f)];
    }
    inline bool feat(mrpt::cpu::feature f) const noexcept
    {
        return feat_detected[static_cast<std::size_t>(f)];
    }

   private:
    // Ctor: runs all the checks and fills in the vector of features:
    CPU_analyzer() noexcept
    {
        // Start with all falses:
        feat_detected.fill(false);
        detect_impl();
    }
    void detect_impl() noexcept;
};
}  // namespace internal

/** Returns true if the current CPU (and OS) supports the given CPU feature.
 * \ingroup mrpt_core_grp
 */
inline bool supports(feature f) noexcept
{
    const auto& o = internal::CPU_analyzer::Instance();
    return o.feat(f);
}

/** Blindly enables/disables a CPU feature flag in the list
 * of detected features to be reported in subsequent calls to
 * mrpt::cpu::supports(). Could be used to disable a given CPU feature for
 * benchmarking dynamically-dispatched functions.
 *
 * \note Enabling a feature that is not actually supported by the current CPU
 * would probably lead to program crashes.
 *
 * \ingroup mrpt_core_grp
 */
inline void overrideDetectedFeature(feature f, bool newValue) noexcept
{
    auto& o = internal::CPU_analyzer::Instance();
    o.feat(f) = newValue;
}

/** Returns a string with detected features: "MMX:1 SSE2:0 etc."
 * \ingroup mrpt_core_grp
 */
std::string features_as_string() noexcept;

}  // namespace mrpt::cpu