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 and exact_log2
  29    are defined as inline functions in hwint.h if GCC_VERSION >= 3004.
  30    The definitions here are used for older versions of GCC and non-GCC
  31    bootstrap compilers.  */
  32
  33 /* Given X, an unsigned number, return the largest int Y such that 2**Y <= X.
  34    If X is 0, return -1.  */
  35
  36 int
  37 floor_log2 (unsigned HOST_WIDE_INT x)
  38 {
  39   int t = 0;
  40
  41   if (x == 0)
  42     return -1;
  43
  44   if (HOST_BITS_PER_WIDE_INT > 64)
  45     if (x >= (unsigned HOST_WIDE_INT) 1 << (t + 64))
  46       t += 64;
  47   if (HOST_BITS_PER_WIDE_INT > 32)
  48     if (x >= ((unsigned HOST_WIDE_INT) 1) << (t + 32))
  49       t += 32;
  50   if (x >= ((unsigned HOST_WIDE_INT) 1) << (t + 16))
  51     t += 16;
  52   if (x >= ((unsigned HOST_WIDE_INT) 1) << (t + 8))
  53     t += 8;
  54   if (x >= ((unsigned HOST_WIDE_INT) 1) << (t + 4))
  55     t += 4;
  56   if (x >= ((unsigned HOST_WIDE_INT) 1) << (t + 2))
  57     t += 2;
  58   if (x >= ((unsigned HOST_WIDE_INT) 1) << (t + 1))
  59     t += 1;
  60
  61   return t;
  62 }
  63
  64 /* Return the logarithm of X, base 2, considering X unsigned,
  65    if X is a power of 2.  Otherwise, returns -1.  */
  66
  67 int
  68 exact_log2 (unsigned HOST_WIDE_INT x)
  69 {
  70   if (x != (x & -x))
  71     return -1;
  72   return floor_log2 (x);
  73 }
  74
  75 /* Given X, an unsigned number, return the number of least significant bits
  76    that are zero.  When X == 0, the result is the word size.  */
  77
  78 int
  79 ctz_hwi (unsigned HOST_WIDE_INT x)
  80 {
  81   return x ? floor_log2 (x & -x) : HOST_BITS_PER_WIDE_INT;
  82 }
  83
  84 /* Similarly for most significant bits.  */
  85
  86 int
  87 clz_hwi (unsigned HOST_WIDE_INT x)
  88 {
  89   return HOST_BITS_PER_WIDE_INT - 1 - floor_log2(x);
  90 }
  91
  92 /* Similar to ctz_hwi, except that the least significant bit is numbered
  93    starting from 1, and X == 0 yields 0.  */
  94
  95 int
  96 ffs_hwi (unsigned HOST_WIDE_INT x)
  97 {
  98   return 1 + floor_log2 (x & -x);
  99 }
 100
 101 #endif /* GCC_VERSION < 3004 */
 102
 103 /* Compute the absolute value of X.  */
 104
 105 HOST_WIDE_INT
 106 abs_hwi (HOST_WIDE_INT x)
 107 {
 108   gcc_checking_assert (x != HOST_WIDE_INT_MIN);
 109   return x >= 0 ? x : -x;
 110 }
 111
 112 /* Compute the greatest common divisor of two numbers A and B using
 113    Euclid's algorithm.  */
 114
 115 HOST_WIDE_INT
 116 gcd (HOST_WIDE_INT a, HOST_WIDE_INT b)
 117 {
 118   HOST_WIDE_INT x, y, z;
 119
 120   x = abs_hwi (a);
 121   y = abs_hwi (b);
 122
 123   while (x > 0)
 124     {
 125       z = y % x;
 126       y = x;
 127       x = z;
 128     }
 129
 130   return y;
 131 }
 132
 133 /* For X and Y positive integers, return X multiplied by Y and check
 134    that the result does not overflow.  */
 135
 136 HOST_WIDE_INT
 137 pos_mul_hwi (HOST_WIDE_INT x, HOST_WIDE_INT y)
 138 {
 139   if (x != 0)
 140     gcc_checking_assert ((HOST_WIDE_INT_MAX) / x >= y);
 141
 142   return x * y;
 143 }
 144
 145 /* Return X multiplied by Y and check that the result does not
 146    overflow.  */
 147
 148 HOST_WIDE_INT
 149 mul_hwi (HOST_WIDE_INT x, HOST_WIDE_INT y)
 150 {
 151   gcc_checking_assert (x != HOST_WIDE_INT_MIN
 152                        && y != HOST_WIDE_INT_MIN);
 153
 154   if (x >= 0)
 155     {
 156       if (y >= 0)
 157         return pos_mul_hwi (x, y);
 158
 159       return -pos_mul_hwi (x, -y);
 160     }
 161
 162   if (y >= 0)
 163     return -pos_mul_hwi (-x, y);
 164
 165   return pos_mul_hwi (-x, -y);
 166 }
 167
 168 /* Compute the least common multiple of two numbers A and B .  */
 169
 170 HOST_WIDE_INT
 171 least_common_multiple (HOST_WIDE_INT a, HOST_WIDE_INT b)
 172 {
 173   return mul_hwi (abs_hwi (a) / gcd (a, b), abs_hwi (b));
 174 }