third_party/flac/src/libFLAC/include/private/bitmath.h

/* libFLAC - Free Lossless Audio Codec library
 * Copyright (C) 2001-2009  Josh Coalson
 * Copyright (C) 2011-2022  Xiph.Org Foundation
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 *
 * - Neither the name of the Xiph.org Foundation nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef FLAC__PRIVATE__BITMATH_H
#define FLAC__PRIVATE__BITMATH_H

#include "FLAC/ordinals.h"
#include "FLAC/assert.h"

#include "share/compat.h"

#if defined(_MSC_VER)
#include <intrin.h> /* for _BitScanReverse* */
#endif

/* Will never be emitted for MSVC, GCC, Intel compilers */
static inline uint32_t FLAC__clz_soft_uint32(FLAC__uint32 word) {
  static const uint8_t byte_to_unary_table[] = {
      8, 7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4, 3, 3, 3, 3, 3, 3, 3, 3,
      3, 3, 3, 3, 3, 3, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
      2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1,
      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
      1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  };

  return word > 0xffffff ? byte_to_unary_table[word >> 24]
         : word > 0xffff ? byte_to_unary_table[word >> 16] + 8
         : word > 0xff   ? byte_to_unary_table[word >> 8] + 16
                         : byte_to_unary_table[word] + 24;
}

static inline uint32_t FLAC__clz_uint32(FLAC__uint32 v) {
  /* Never used with input 0 */
  FLAC__ASSERT(v > 0);
#if defined(__INTEL_COMPILER)
  return _bit_scan_reverse(v) ^ 31U;
#elif defined(__GNUC__) && (__GNUC__ >= 4 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4))
/* This will translate either to (bsr ^ 31U), clz , ctlz, cntlz, lzcnt depending on
 * -march= setting or to a software routine in exotic machines. */
return __builtin_clz(v);
#elif defined(_MSC_VER)
  {
    uint32_t idx;
    _BitScanReverse(&idx, v);
    return idx ^ 31U;
  }
#else
  return FLAC__clz_soft_uint32(v);
#endif
}

/* Used when 64-bit bsr/clz is unavailable; can use 32-bit bsr/clz when possible
 */
static inline uint32_t FLAC__clz_soft_uint64(FLAC__uint64 word) {
  return (FLAC__uint32)(word >> 32)
             ? FLAC__clz_uint32((FLAC__uint32)(word >> 32))
             : FLAC__clz_uint32((FLAC__uint32)word) + 32;
}

static inline uint32_t FLAC__clz_uint64(FLAC__uint64 v) {
  /* Never used with input 0 */
  FLAC__ASSERT(v > 0);
#if defined(__GNUC__) && \
    (__GNUC__ >= 4 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4))
  return __builtin_clzll(v);
#elif (defined(__INTEL_COMPILER) || defined(_MSC_VER)) && \
    (defined(_M_IA64) || defined(_M_X64))
{
  uint32_t idx;
  _BitScanReverse64(&idx, v);
  return idx ^ 63U;
}
#else
  return FLAC__clz_soft_uint64(v);
#endif
}

/* These two functions work with input 0 */
static inline uint32_t FLAC__clz2_uint32(FLAC__uint32 v) {
  if (!v) {
    return 32;
  }
  return FLAC__clz_uint32(v);
}

static inline uint32_t FLAC__clz2_uint64(FLAC__uint64 v) {
  if (!v) {
    return 64;
  }
  return FLAC__clz_uint64(v);
}

/* An example of what FLAC__bitmath_ilog2() computes:
 *
 * ilog2( 0) = assertion failure
 * ilog2( 1) = 0
 * ilog2( 2) = 1
 * ilog2( 3) = 1
 * ilog2( 4) = 2
 * ilog2( 5) = 2
 * ilog2( 6) = 2
 * ilog2( 7) = 2
 * ilog2( 8) = 3
 * ilog2( 9) = 3
 * ilog2(10) = 3
 * ilog2(11) = 3
 * ilog2(12) = 3
 * ilog2(13) = 3
 * ilog2(14) = 3
 * ilog2(15) = 3
 * ilog2(16) = 4
 * ilog2(17) = 4
 * ilog2(18) = 4
 */

static inline uint32_t FLAC__bitmath_ilog2(FLAC__uint32 v) {
  FLAC__ASSERT(v > 0);
#if defined(__INTEL_COMPILER)
  return _bit_scan_reverse(v);
#elif defined(_MSC_VER)
{
  uint32_t idx;
  _BitScanReverse(&idx, v);
  return idx;
}
#else
  return FLAC__clz_uint32(v) ^ 31U;
#endif
}

static inline uint32_t FLAC__bitmath_ilog2_wide(FLAC__uint64 v) {
  FLAC__ASSERT(v > 0);
#if defined(__GNUC__) && (__GNUC__ >= 4 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4))
  return __builtin_clzll(v) ^ 63U;
/* Sorry, only supported in x64/Itanium.. and both have fast FPU which makes integer-only encoder pointless */
#elif (defined(__INTEL_COMPILER) || defined(_MSC_VER)) && \
    (defined(_M_IA64) || defined(_M_X64))
{
  uint32_t idx;
  _BitScanReverse64(&idx, v);
  return idx;
}
#else
  /*  Brain-damaged compilers will use the fastest possible way that is,
          de Bruijn sequences
     (http://supertech.csail.mit.edu/papers/debruijn.pdf) (C) Timothy B.
     Terriberry (tterribe@xiph.org) 2001-2009 CC0 (Public domain).
  */
  {
    static const uint8_t DEBRUIJN_IDX64[64] = {
        0,  1,  2,  7,  3,  13, 8,  19, 4,  25, 14, 28, 9,  34, 20, 40,
        5,  17, 26, 38, 15, 46, 29, 48, 10, 31, 35, 54, 21, 50, 41, 57,
        63, 6,  12, 18, 24, 27, 33, 39, 16, 37, 45, 47, 30, 53, 49, 56,
        62, 11, 23, 32, 36, 44, 52, 55, 61, 22, 43, 51, 60, 42, 59, 58};
    v |= v >> 1;
    v |= v >> 2;
    v |= v >> 4;
    v |= v >> 8;
    v |= v >> 16;
    v |= v >> 32;
    v = (v >> 1) + 1;
    return DEBRUIJN_IDX64[v * FLAC__U64L(0x218A392CD3D5DBF) >> 58 & 0x3F];
  }
#endif
}

uint32_t FLAC__bitmath_silog2(FLAC__int64 v);

#endif