gcc/hwint.c

   1 /* Operations on HOST_WIDE_INT.
   2    Copyright (C) 1987, 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
   3    1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
   4    Free Software Foundation, Inc.
   5
   6 This file is part of GCC.
   7
   8 GCC is free software; you can redistribute it and/or modify it under
   9 the terms of the GNU General Public License as published by the Free
  10 Software Foundation; either version 3, or (at your option) any later
  11 version.
  12
  13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  15 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  16 for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GCC; see the file COPYING3.  If not see
  20 <http://www.gnu.org/licenses/>.  */
  21
  22 #include "config.h"
  23 #include "system.h"
  24 #include "diagnostic-core.h"
  25
  26 #if GCC_VERSION < 3004
  27
  28 /* The functions clz_hwi, ctz_hwi, ffs_hwi, floor_log2, ceil_log2,
  29    and exact_log2 are defined as inline functions in hwint.h
  30    if GCC_VERSION >= 3004.
  31    The definitions here are used for older versions of GCC and
  32    non-GCC bootstrap compilers.  */
  33
  34 /* Given X, an unsigned number, return the largest int Y such that 2**Y <= X.
  35    If X is 0, return -1.  */
  36
  37 int
  38 floor_log2 (unsigned HOST_WIDE_INT x)
  39 {
  40   int t = 0;
  41
  42   if (x == 0)
  43     return -1;
  44
  45   if (HOST_BITS_PER_WIDE_INT > 64)
  46     if (x >= (unsigned HOST_WIDE_INT) 1 << (t + 64))
  47       t += 64;
  48   if (HOST_BITS_PER_WIDE_INT > 32)
  49     if (x >= ((unsigned HOST_WIDE_INT) 1) << (t + 32))
  50       t += 32;
  51   if (x >= ((unsigned HOST_WIDE_INT) 1) << (t + 16))
  52     t += 16;
  53   if (x >= ((unsigned HOST_WIDE_INT) 1) << (t + 8))
  54     t += 8;
  55   if (x >= ((unsigned HOST_WIDE_INT) 1) << (t + 4))
  56     t += 4;
  57   if (x >= ((unsigned HOST_WIDE_INT) 1) << (t + 2))
  58     t += 2;
  59   if (x >= ((unsigned HOST_WIDE_INT) 1) << (t + 1))
  60     t += 1;
  61
  62   return t;
  63 }
  64
  65 /* Given X, an unsigned number, return the largest Y such that 2**Y >= X.  */
  66
  67 int
  68 ceil_log2 (unsigned HOST_WIDE_INT x)
  69 {
  70   return floor_log2 (x - 1) + 1;
  71 }
  72
  73 /* Return the logarithm of X, base 2, considering X unsigned,
  74    if X is a power of 2.  Otherwise, returns -1.  */
  75
  76 int
  77 exact_log2 (unsigned HOST_WIDE_INT x)
  78 {
  79   if (x != (x & -x))
  80     return -1;
  81   return floor_log2 (x);
  82 }
  83
  84 /* Given X, an unsigned number, return the number of least significant bits
  85    that are zero.  When X == 0, the result is the word size.  */
  86
  87 int
  88 ctz_hwi (unsigned HOST_WIDE_INT x)
  89 {
  90   return x ? floor_log2 (x & -x) : HOST_BITS_PER_WIDE_INT;
  91 }
  92
  93 /* Similarly for most significant bits.  */
  94
  95 int
  96 clz_hwi (unsigned HOST_WIDE_INT x)
  97 {
  98   return HOST_BITS_PER_WIDE_INT - 1 - floor_log2(x);
  99 }
 100
 101 /* Similar to ctz_hwi, except that the least significant bit is numbered
 102    starting from 1, and X == 0 yields 0.  */
 103
 104 int
 105 ffs_hwi (unsigned HOST_WIDE_INT x)
 106 {
 107   return 1 + floor_log2 (x & -x);
 108 }
 109
 110 #endif /* GCC_VERSION < 3004 */
 111
 112 /* Compute the absolute value of X.  */
 113
 114 HOST_WIDE_INT
 115 abs_hwi (HOST_WIDE_INT x)
 116 {
 117   gcc_checking_assert (x != HOST_WIDE_INT_MIN);
 118   return x >= 0 ? x : -x;
 119 }
 120
 121 /* Compute the absolute value of X as an unsigned type.  */
 122
 123 unsigned HOST_WIDE_INT
 124 absu_hwi (HOST_WIDE_INT x)
 125 {
 126   return x >= 0 ? (unsigned HOST_WIDE_INT)x : -(unsigned HOST_WIDE_INT)x;
 127 }
 128
 129 /* Compute the greatest common divisor of two numbers A and B using
 130    Euclid's algorithm.  */
 131
 132 HOST_WIDE_INT
 133 gcd (HOST_WIDE_INT a, HOST_WIDE_INT b)
 134 {
 135   HOST_WIDE_INT x, y, z;
 136
 137   x = abs_hwi (a);
 138   y = abs_hwi (b);
 139
 140   while (x > 0)
 141     {
 142       z = y % x;
 143       y = x;
 144       x = z;
 145     }
 146
 147   return y;
 148 }
 149
 150 /* For X and Y positive integers, return X multiplied by Y and check
 151    that the result does not overflow.  */
 152
 153 HOST_WIDE_INT
 154 pos_mul_hwi (HOST_WIDE_INT x, HOST_WIDE_INT y)
 155 {
 156   if (x != 0)
 157     gcc_checking_assert ((HOST_WIDE_INT_MAX) / x >= y);
 158
 159   return x * y;
 160 }
 161
 162 /* Return X multiplied by Y and check that the result does not
 163    overflow.  */
 164
 165 HOST_WIDE_INT
 166 mul_hwi (HOST_WIDE_INT x, HOST_WIDE_INT y)
 167 {
 168   gcc_checking_assert (x != HOST_WIDE_INT_MIN
 169                        && y != HOST_WIDE_INT_MIN);
 170
 171   if (x >= 0)
 172     {
 173       if (y >= 0)
 174         return pos_mul_hwi (x, y);
 175
 176       return -pos_mul_hwi (x, -y);
 177     }
 178
 179   if (y >= 0)
 180     return -pos_mul_hwi (-x, y);
 181
 182   return pos_mul_hwi (-x, -y);
 183 }
 184
 185 /* Compute the least common multiple of two numbers A and B .  */
 186
 187 HOST_WIDE_INT
 188 least_common_multiple (HOST_WIDE_INT a, HOST_WIDE_INT b)
 189 {
 190   return mul_hwi (abs_hwi (a) / gcd (a, b), abs_hwi (b));
 191 }