gcc/sreal.h

   1 /* Definitions for simple data type for real numbers.
   2    Copyright (C) 2002-2021 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 #define SREAL_PART_BITS 31
  24
  25 #define UINT64_BITS     64
  26
  27 #define SREAL_MIN_SIG ((int64_t) 1 << (SREAL_PART_BITS - 2))
  28 #define SREAL_MAX_SIG (((int64_t) 1 << (SREAL_PART_BITS - 1)) - 1)
  29 #define SREAL_MAX_EXP (INT_MAX / 4)
  30
  31 #define SREAL_BITS SREAL_PART_BITS
  32
  33 #define SREAL_SIGN(v) (v < 0 ? -1: 1)
  34 #define SREAL_ABS(v) (v < 0 ? -v: v)
  35
  36 struct output_block;
  37 class lto_input_block;
  38
  39 /* Structure for holding a simple real number.  */
  40 class sreal
  41 {
  42 public:
  43   /* Construct an uninitialized sreal.  */
  44   sreal () : m_sig (-1), m_exp (-1) {}
  45
  46   /* Construct a sreal.  */
  47   sreal (int64_t sig, int exp = 0)
  48   {
  49     normalize (sig, exp);
  50   }
  51
  52   void dump (FILE *) const;
  53   int64_t to_int () const;
  54   double to_double () const;
  55   void stream_out (struct output_block *);
  56   static sreal stream_in (class lto_input_block *);
  57   sreal operator+ (const sreal &other) const;
  58   sreal operator- (const sreal &other) const;
  59   sreal operator* (const sreal &other) const;
  60   sreal operator/ (const sreal &other) const;
  61
  62   bool operator< (const sreal &other) const
  63   {
  64     if (m_exp == other.m_exp)
  65       return m_sig < other.m_sig;
  66     else
  67     {
  68       bool negative = m_sig < 0;
  69       bool other_negative = other.m_sig < 0;
  70
  71       if (negative != other_negative)
  72         return negative > other_negative;
  73
  74       bool r = m_exp < other.m_exp;
  75       return negative ? !r : r;
  76     }
  77   }
  78
  79   bool operator== (const sreal &other) const
  80   {
  81     return m_exp == other.m_exp && m_sig == other.m_sig;
  82   }
  83
  84   sreal operator- () const
  85   {
  86     sreal tmp = *this;
  87     tmp.m_sig *= -1;
  88
  89     return tmp;
  90   }
  91
  92   sreal shift (int s) const
  93   {
  94     /* Zero needs no shifting.  */
  95     if (!m_sig)
  96       return *this;
  97     gcc_checking_assert (s <= SREAL_MAX_EXP);
  98     gcc_checking_assert (s >= -SREAL_MAX_EXP);
  99
 100     /* Overflows/drop to 0 could be handled gracefully, but hopefully we do not
 101        need to do so.  */
 102     gcc_checking_assert (m_exp + s <= SREAL_MAX_EXP);
 103     gcc_checking_assert (m_exp + s >= -SREAL_MAX_EXP);
 104
 105     sreal tmp = *this;
 106     tmp.m_exp += s;
 107
 108     return tmp;
 109   }
 110
 111   /* Global minimum sreal can hold.  */
 112   inline static sreal min ()
 113   {
 114     sreal min;
 115     /* This never needs normalization.  */
 116     min.m_sig = -SREAL_MAX_SIG;
 117     min.m_exp = SREAL_MAX_EXP;
 118     return min;
 119   }
 120
 121   /* Global minimum sreal can hold.  */
 122   inline static sreal max ()
 123   {
 124     sreal max;
 125     /* This never needs normalization.  */
 126     max.m_sig = SREAL_MAX_SIG;
 127     max.m_exp = SREAL_MAX_EXP;
 128     return max;
 129   }
 130
 131 private:
 132   inline void normalize (int64_t new_sig, signed int new_exp);
 133   inline void normalize_up (int64_t new_sig, signed int new_exp);
 134   inline void normalize_down (int64_t new_sig, signed int new_exp);
 135   void shift_right (int amount);
 136   static sreal signedless_plus (const sreal &a, const sreal &b, bool negative);
 137   static sreal signedless_minus (const sreal &a, const sreal &b, bool negative);
 138
 139   int32_t m_sig;                        /* Significant.  */
 140   signed int m_exp;                     /* Exponent.  */
 141 };
 142
 143 extern void debug (const sreal &ref);
 144 extern void debug (const sreal *ptr);
 145
 146 inline sreal &operator+= (sreal &a, const sreal &b)
 147 {
 148   return a = a + b;
 149 }
 150
 151 inline sreal &operator-= (sreal &a, const sreal &b)
 152 {
 153   return a = a - b;
 154 }
 155
 156 inline sreal &operator/= (sreal &a, const sreal &b)
 157 {
 158   return a = a / b;
 159 }
 160
 161 inline sreal &operator*= (sreal &a, const sreal &b)
 162 {
 163   return a = a  * b;
 164 }
 165
 166 inline bool operator!= (const sreal &a, const sreal &b)
 167 {
 168   return !(a == b);
 169 }
 170
 171 inline bool operator> (const sreal &a, const sreal &b)
 172 {
 173   return !(a == b || a < b);
 174 }
 175
 176 inline bool operator<= (const sreal &a, const sreal &b)
 177 {
 178   return a < b || a == b;
 179 }
 180
 181 inline bool operator>= (const sreal &a, const sreal &b)
 182 {
 183   return a == b || a > b;
 184 }
 185
 186 inline sreal operator<< (const sreal &a, int exp)
 187 {
 188   return a.shift (exp);
 189 }
 190
 191 inline sreal operator>> (const sreal &a, int exp)
 192 {
 193   return a.shift (-exp);
 194 }
 195
 196 /* Make significant to be >= SREAL_MIN_SIG.
 197
 198    Make this separate method so inliner can handle hot path better.  */
 199
 200 inline void
 201 sreal::normalize_up (int64_t new_sig, signed int new_exp)
 202 {
 203   unsigned HOST_WIDE_INT sig = absu_hwi (new_sig);
 204   int shift = SREAL_PART_BITS - 2 - floor_log2 (sig);
 205
 206   gcc_checking_assert (shift > 0);
 207   sig <<= shift;
 208   new_exp -= shift;
 209   gcc_checking_assert (sig <= SREAL_MAX_SIG && sig >= SREAL_MIN_SIG);
 210
 211   /* Check underflow.  */
 212   if (new_exp < -SREAL_MAX_EXP)
 213     {
 214       new_exp = -SREAL_MAX_EXP;
 215       sig = 0;
 216     }
 217   m_exp = new_exp;
 218   if (SREAL_SIGN (new_sig) == -1)
 219     m_sig = -sig;
 220   else
 221     m_sig = sig;
 222 }
 223
 224 /* Make significant to be <= SREAL_MAX_SIG.
 225
 226    Make this separate method so inliner can handle hot path better.  */
 227
 228 inline void
 229 sreal::normalize_down (int64_t new_sig, signed int new_exp)
 230 {
 231   int last_bit;
 232   unsigned HOST_WIDE_INT sig = absu_hwi (new_sig);
 233   int shift = floor_log2 (sig) - SREAL_PART_BITS + 2;
 234
 235   gcc_checking_assert (shift > 0);
 236   last_bit = (sig >> (shift-1)) & 1;
 237   sig >>= shift;
 238   new_exp += shift;
 239   gcc_checking_assert (sig <= SREAL_MAX_SIG && sig >= SREAL_MIN_SIG);
 240
 241   /* Round the number.  */
 242   sig += last_bit;
 243   if (sig > SREAL_MAX_SIG)
 244     {
 245       sig >>= 1;
 246       new_exp++;
 247     }
 248
 249   /* Check overflow.  */
 250   if (new_exp > SREAL_MAX_EXP)
 251     {
 252       new_exp = SREAL_MAX_EXP;
 253       sig = SREAL_MAX_SIG;
 254     }
 255   m_exp = new_exp;
 256   if (SREAL_SIGN (new_sig) == -1)
 257     m_sig = -sig;
 258   else
 259     m_sig = sig;
 260 }
 261
 262 /* Normalize *this; the hot path.  */
 263
 264 inline void
 265 sreal::normalize (int64_t new_sig, signed int new_exp)
 266 {
 267   unsigned HOST_WIDE_INT sig = absu_hwi (new_sig);
 268
 269   if (sig == 0)
 270     {
 271       m_sig = 0;
 272       m_exp = -SREAL_MAX_EXP;
 273     }
 274   else if (sig > SREAL_MAX_SIG)
 275     normalize_down (new_sig, new_exp);
 276   else if (sig < SREAL_MIN_SIG)
 277     normalize_up (new_sig, new_exp);
 278   else
 279     {
 280       m_sig = new_sig;
 281       m_exp = new_exp;
 282     }
 283 }
 284
 285 #endif