reverse.h

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// SPDX-License-Identifier: Apache-2.0
// Copyright Contributors to the OpenQMC Project.
 
 
#pragma once
 
#include "gpu.h"
 
#include <cstdint>
 
namespace oqmc
{
 
OQMC_HOST_DEVICE constexpr std::uint32_t reverseBits32(std::uint32_t value)
{
#if defined(__CUDA_ARCH__)
    value = __brev(value);
#else
    value = (((value & 0xaaaaaaaa) >> 1) | ((value & 0x55555555) << 1));
    value = (((value & 0xcccccccc) >> 2) | ((value & 0x33333333) << 2));
    value = (((value & 0xf0f0f0f0) >> 4) | ((value & 0x0f0f0f0f) << 4));
 
#if defined(_MSC_VER)
    value = (((value & 0xff00ff00) >> 8) | ((value & 0x00ff00ff) << 8));
    value = ((value >> 16) | (value << 16));
#else
    value = __builtin_bswap32(value);
#endif
#endif
 
    return value;
}
 
OQMC_HOST_DEVICE constexpr std::uint16_t reverseBits16(std::uint16_t value)
{
#if defined(__CUDA_ARCH__)
    value = __brev(value) >> 16;
#else
    value = (((value & 0xaaaaaaaa) >> 1) | ((value & 0x55555555) << 1));
    value = (((value & 0xcccccccc) >> 2) | ((value & 0x33333333) << 2));
    value = (((value & 0xf0f0f0f0) >> 4) | ((value & 0x0f0f0f0f) << 4));
 
#if defined(_MSC_VER)
    value = ((value >> 8) | (value << 8));
#else
    value = __builtin_bswap16(value);
#endif
#endif
 
    return value;
}
 
} // namespace oqmc