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 *    may be used to endorse or promote products derived from this software
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/** \file
 * \brief Platform specific popcount functions
 */

#ifndef POPCOUNT_H_075D843B4545B6
#define POPCOUNT_H_075D843B4545B6

#include "ue2common.h"

// We have a native popcount where the compiler has defined __POPCNT__.
#if defined(__POPCNT__)
#define HAVE_POPCOUNT_INSTR
#elif defined(_WIN32) && defined(__AVX__) // TODO: fix win preproc
#define HAVE_POPCOUNT_INSTR
#endif

static really_inline
u32 popcount32(u32 x) {
#if defined(HAVE_POPCOUNT_INSTR)
    // Single-instruction builtin.
    return _mm_popcnt_u32(x);
#else
    // Fast branch-free version from bit-twiddling hacks as older Intel
    // processors do not have a POPCNT instruction.
    x -= (x >> 1) & 0x55555555;
    x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
    return (((x + (x >> 4)) & 0xf0f0f0f) * 0x1010101) >> 24;
#endif
}

static really_inline
u32 popcount64(u64a x) {
#if defined(ARCH_X86_64)
# if defined(HAVE_POPCOUNT_INSTR)
    // Single-instruction builtin.
    return (u32)_mm_popcnt_u64(x);
# else
    // Fast branch-free version from bit-twiddling hacks as older Intel
    // processors do not have a POPCNT instruction.
    x -= (x >> 1) & 0x5555555555555555;
    x = (x & 0x3333333333333333) + ((x >> 2) & 0x3333333333333333);
    x = (x + (x >> 4)) & 0x0f0f0f0f0f0f0f0f;
    return (x * 0x0101010101010101) >> 56;
# endif
#else
    // Synthesise from two 32-bit cases.
    return popcount32(x >> 32) + popcount32(x);
#endif
}

#endif /* POPCOUNT_H_075D843B4545B6 */