1/*
2 * Copyright (c) 2015-2017, Intel Corporation
3 *
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5 * modification, are permitted provided that the following conditions are met:
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15 *
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17 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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27 */
28
29/** \file
30 * \brief Platform specific popcount functions
31 */
32
33#ifndef UTIL_POPCOUNT_H_
34#define UTIL_POPCOUNT_H_
35
36#include "ue2common.h"
37#include "util/arch.h"
38
39static really_inline
40u32 popcount32(u32 x) {
41#if defined(HAVE_POPCOUNT_INSTR)
42 // Single-instruction builtin.
43 return _mm_popcnt_u32(x);
44#else
45 // Fast branch-free version from bit-twiddling hacks as older Intel
46 // processors do not have a POPCNT instruction.
47 x -= (x >> 1) & 0x55555555;
48 x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
49 return (((x + (x >> 4)) & 0xf0f0f0f) * 0x1010101) >> 24;
50#endif
51}
52
53static really_inline
54u32 popcount64(u64a x) {
55#if defined(ARCH_X86_64)
56# if defined(HAVE_POPCOUNT_INSTR)
57 // Single-instruction builtin.
58 return (u32)_mm_popcnt_u64(x);
59# else
60 // Fast branch-free version from bit-twiddling hacks as older Intel
61 // processors do not have a POPCNT instruction.
62 x -= (x >> 1) & 0x5555555555555555;
63 x = (x & 0x3333333333333333) + ((x >> 2) & 0x3333333333333333);
64 x = (x + (x >> 4)) & 0x0f0f0f0f0f0f0f0f;
65 return (x * 0x0101010101010101) >> 56;
66# endif
67#else
68 // Synthesise from two 32-bit cases.
69 return popcount32(x >> 32) + popcount32(x);
70#endif
71}
72
73#endif /* UTIL_POPCOUNT_H_ */
74
75