gcc/sreal.h

   1 /* Definitions for simple data type for real numbers.
   2    Copyright (C) 2002-2014 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 3, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING3.  If not see
  18 <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef GCC_SREAL_H
  21 #define GCC_SREAL_H
  22
  23 /* SREAL_PART_BITS has to be an even number.  */
  24 #define SREAL_PART_BITS 32
  25
  26 #define UINT64_BITS     64
  27
  28 #define SREAL_MIN_SIG ((int64_t) 1 << (SREAL_PART_BITS - 2))
  29 #define SREAL_MAX_SIG (((int64_t) 1 << (SREAL_PART_BITS - 1)) - 1)
  30 #define SREAL_MAX_EXP (INT_MAX / 4)
  31
  32 #define SREAL_BITS SREAL_PART_BITS
  33
  34 /* Structure for holding a simple real number.  */
  35 class sreal
  36 {
  37 public:
  38   /* Construct an uninitialized sreal.  */
  39   sreal () : m_sig (-1), m_exp (-1) {}
  40
  41   /* Construct a sreal.  */
  42   sreal (int64_t sig, int exp = 0) : m_sig (sig), m_exp (exp)
  43   {
  44     normalize ();
  45   }
  46
  47   void dump (FILE *) const;
  48   int64_t to_int () const;
  49   double to_double () const;
  50   sreal operator+ (const sreal &other) const;
  51   sreal operator- (const sreal &other) const;
  52   sreal operator* (const sreal &other) const;
  53   sreal operator/ (const sreal &other) const;
  54
  55   bool operator< (const sreal &other) const
  56   {
  57     if (m_exp == other.m_exp)
  58       return m_sig < other.m_sig;
  59     else
  60     {
  61       bool negative = m_sig < 0;
  62       bool other_negative = other.m_sig < 0;
  63
  64       if (negative != other_negative)
  65         return negative > other_negative;
  66
  67       bool r = m_exp < other.m_exp;
  68       return negative ? !r : r;
  69     }
  70   }
  71
  72   bool operator== (const sreal &other) const
  73   {
  74     return m_exp == other.m_exp && m_sig == other.m_sig;
  75   }
  76
  77   sreal operator- () const
  78   {
  79     sreal tmp = *this;
  80     tmp.m_sig *= -1;
  81
  82     return tmp;
  83   }
  84
  85   sreal shift (int s) const
  86   {
  87     /* Zero needs no shifting.  */
  88     if (!m_sig)
  89       return *this;
  90     gcc_checking_assert (s <= SREAL_MAX_EXP);
  91     gcc_checking_assert (s >= -SREAL_MAX_EXP);
  92
  93     /* Overflows/drop to 0 could be handled gracefully, but hopefully we do not
  94        need to do so.  */
  95     gcc_checking_assert (m_exp + s <= SREAL_MAX_EXP);
  96     gcc_checking_assert (m_exp + s >= -SREAL_MAX_EXP);
  97
  98     sreal tmp = *this;
  99     tmp.m_exp += s;
 100
 101     return tmp;
 102   }
 103
 104   /* Global minimum sreal can hold.  */
 105   inline static sreal min ()
 106   {
 107     static sreal min = sreal (-SREAL_MAX_SIG, SREAL_MAX_EXP);
 108     return min;
 109   }
 110
 111   /* Global minimum sreal can hold.  */
 112   inline static sreal max ()
 113   {
 114     static sreal max = sreal (SREAL_MAX_SIG, SREAL_MAX_EXP);
 115     return max;
 116   }
 117
 118 private:
 119   inline void normalize ();
 120   inline void normalize_up ();
 121   inline void normalize_down ();
 122   void shift_right (int amount);
 123   static sreal signedless_plus (const sreal &a, const sreal &b, bool negative);
 124   static sreal signedless_minus (const sreal &a, const sreal &b, bool negative);
 125
 126   int64_t m_sig;                        /* Significant.  */
 127   signed int m_exp;                     /* Exponent.  */
 128 };
 129
 130 extern void debug (const sreal &ref);
 131 extern void debug (const sreal *ptr);
 132
 133 inline sreal &operator+= (sreal &a, const sreal &b)
 134 {
 135   return a = a + b;
 136 }
 137
 138 inline sreal &operator-= (sreal &a, const sreal &b)
 139 {
 140   return a = a - b;
 141 }
 142
 143 inline sreal &operator/= (sreal &a, const sreal &b)
 144 {
 145   return a = a / b;
 146 }
 147
 148 inline sreal &operator*= (sreal &a, const sreal &b)
 149 {
 150   return a = a  * b;
 151 }
 152
 153 inline bool operator!= (const sreal &a, const sreal &b)
 154 {
 155   return !(a == b);
 156 }
 157
 158 inline bool operator> (const sreal &a, const sreal &b)
 159 {
 160   return !(a == b || a < b);
 161 }
 162
 163 inline bool operator<= (const sreal &a, const sreal &b)
 164 {
 165   return a < b || a == b;
 166 }
 167
 168 inline bool operator>= (const sreal &a, const sreal &b)
 169 {
 170   return a == b || a > b;
 171 }
 172
 173 inline sreal operator<< (const sreal &a, int exp)
 174 {
 175   return a.shift (exp);
 176 }
 177
 178 inline sreal operator>> (const sreal &a, int exp)
 179 {
 180   return a.shift (-exp);
 181 }
 182
 183 /* Make significant to be >= SREAL_MIN_SIG.
 184
 185    Make this separate method so inliner can handle hot path better.  */
 186
 187 inline void
 188 sreal::normalize_up ()
 189 {
 190   int64_t s = m_sig < 0 ? -1 : 1;
 191   unsigned HOST_WIDE_INT sig = absu_hwi (m_sig);
 192   int shift = SREAL_PART_BITS - 2 - floor_log2 (sig);
 193
 194   gcc_checking_assert (shift > 0);
 195   sig <<= shift;
 196   m_exp -= shift;
 197   gcc_checking_assert (sig <= SREAL_MAX_SIG && sig >= SREAL_MIN_SIG);
 198
 199   /* Check underflow.  */
 200   if (m_exp < -SREAL_MAX_EXP)
 201     {
 202       m_exp = -SREAL_MAX_EXP;
 203       sig = 0;
 204     }
 205   if (s == -1)
 206     m_sig = -sig;
 207   else
 208     m_sig = sig;
 209 }
 210
 211 /* Make significant to be <= SREAL_MAX_SIG.
 212
 213    Make this separate method so inliner can handle hot path better.  */
 214
 215 inline void
 216 sreal::normalize_down ()
 217 {
 218   int64_t s = m_sig < 0 ? -1 : 1;
 219   int last_bit;
 220   unsigned HOST_WIDE_INT sig = absu_hwi (m_sig);
 221   int shift = floor_log2 (sig) - SREAL_PART_BITS + 2;
 222
 223   gcc_checking_assert (shift > 0);
 224   last_bit = (sig >> (shift-1)) & 1;
 225   sig >>= shift;
 226   m_exp += shift;
 227   gcc_checking_assert (sig <= SREAL_MAX_SIG && sig >= SREAL_MIN_SIG);
 228
 229   /* Round the number.  */
 230   sig += last_bit;
 231   if (sig > SREAL_MAX_SIG)
 232     {
 233       sig >>= 1;
 234       m_exp++;
 235     }
 236
 237   /* Check overflow.  */
 238   if (m_exp > SREAL_MAX_EXP)
 239     {
 240       m_exp = SREAL_MAX_EXP;
 241       sig = SREAL_MAX_SIG;
 242     }
 243   if (s == -1)
 244     m_sig = -sig;
 245   else
 246     m_sig = sig;
 247 }
 248
 249 /* Normalize *this; the hot path.  */
 250
 251 inline void
 252 sreal::normalize ()
 253 {
 254   unsigned HOST_WIDE_INT sig = absu_hwi (m_sig);
 255
 256   if (sig == 0)
 257     m_exp = -SREAL_MAX_EXP;
 258   else if (sig > SREAL_MAX_SIG)
 259     normalize_down ();
 260   else if (sig < SREAL_MIN_SIG)
 261     normalize_up ();
 262 }
 263
 264 #endif