gcc/sreal.h

   1 /* Definitions for simple data type for real numbers.
   2    Copyright (C) 2002-2024 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   int64_t to_nearest_int () const;
  55   double to_double () const;
  56   void stream_out (struct output_block *);
  57   static sreal stream_in (class lto_input_block *);
  58   sreal operator+ (const sreal &other) const;
  59   sreal operator- (const sreal &other) const;
  60   sreal operator* (const sreal &other) const;
  61   sreal operator/ (const sreal &other) const;
  62
  63   bool operator< (const sreal &other) const
  64   {
  65     if (m_exp == other.m_exp)
  66       return m_sig < other.m_sig;
  67     else
  68     {
  69       bool negative = m_sig < 0;
  70       bool other_negative = other.m_sig < 0;
  71
  72       if (negative != other_negative)
  73         return negative > other_negative;
  74
  75       bool r = m_exp < other.m_exp;
  76       return negative ? !r : r;
  77     }
  78   }
  79
  80   bool operator== (const sreal &other) const
  81   {
  82     return m_exp == other.m_exp && m_sig == other.m_sig;
  83   }
  84
  85   sreal operator- () const
  86   {
  87     sreal tmp = *this;
  88     tmp.m_sig *= -1;
  89
  90     return tmp;
  91   }
  92
  93   sreal shift (int s) const
  94   {
  95     /* Zero needs no shifting.  */
  96     if (!m_sig)
  97       return *this;
  98     gcc_checking_assert (s <= SREAL_MAX_EXP);
  99     gcc_checking_assert (s >= -SREAL_MAX_EXP);
 100
 101     /* Overflows/drop to 0 could be handled gracefully, but hopefully we do not
 102        need to do so.  */
 103     gcc_checking_assert (m_exp + s <= SREAL_MAX_EXP);
 104     gcc_checking_assert (m_exp + s >= -SREAL_MAX_EXP);
 105
 106     sreal tmp = *this;
 107     tmp.m_exp += s;
 108
 109     return tmp;
 110   }
 111
 112   /* Global minimum sreal can hold.  */
 113   inline static sreal min ()
 114   {
 115     sreal min;
 116     /* This never needs normalization.  */
 117     min.m_sig = -SREAL_MAX_SIG;
 118     min.m_exp = SREAL_MAX_EXP;
 119     return min;
 120   }
 121
 122   /* Global minimum sreal can hold.  */
 123   inline static sreal max ()
 124   {
 125     sreal max;
 126     /* This never needs normalization.  */
 127     max.m_sig = SREAL_MAX_SIG;
 128     max.m_exp = SREAL_MAX_EXP;
 129     return max;
 130   }
 131
 132 private:
 133   inline void normalize (int64_t new_sig, signed int new_exp);
 134   inline void normalize_up (int64_t new_sig, signed int new_exp);
 135   inline void normalize_down (int64_t new_sig, signed int new_exp);
 136   void shift_right (int amount);
 137   static sreal signedless_plus (const sreal &a, const sreal &b, bool negative);
 138   static sreal signedless_minus (const sreal &a, const sreal &b, bool negative);
 139
 140   int32_t m_sig;                        /* Significant.  */
 141   signed int m_exp;                     /* Exponent.  */
 142 };
 143
 144 extern void debug (const sreal &ref);
 145 extern void debug (const sreal *ptr);
 146
 147 inline sreal &operator+= (sreal &a, const sreal &b)
 148 {
 149   return a = a + b;
 150 }
 151
 152 inline sreal &operator-= (sreal &a, const sreal &b)
 153 {
 154   return a = a - b;
 155 }
 156
 157 inline sreal &operator/= (sreal &a, const sreal &b)
 158 {
 159   return a = a / b;
 160 }
 161
 162 inline sreal &operator*= (sreal &a, const sreal &b)
 163 {
 164   return a = a  * b;
 165 }
 166
 167 inline bool operator!= (const sreal &a, const sreal &b)
 168 {
 169   return !(a == b);
 170 }
 171
 172 inline bool operator> (const sreal &a, const sreal &b)
 173 {
 174   return !(a == b || a < b);
 175 }
 176
 177 inline bool operator<= (const sreal &a, const sreal &b)
 178 {
 179   return a < b || a == b;
 180 }
 181
 182 inline bool operator>= (const sreal &a, const sreal &b)
 183 {
 184   return a == b || a > b;
 185 }
 186
 187 inline sreal operator<< (const sreal &a, int exp)
 188 {
 189   return a.shift (exp);
 190 }
 191
 192 inline sreal operator>> (const sreal &a, int exp)
 193 {
 194   return a.shift (-exp);
 195 }
 196
 197 /* Make significant to be >= SREAL_MIN_SIG.
 198
 199    Make this separate method so inliner can handle hot path better.  */
 200
 201 inline void
 202 sreal::normalize_up (int64_t new_sig, signed int new_exp)
 203 {
 204   unsigned HOST_WIDE_INT sig = absu_hwi (new_sig);
 205   int shift = SREAL_PART_BITS - 2 - floor_log2 (sig);
 206
 207   gcc_checking_assert (shift > 0);
 208   sig <<= shift;
 209   new_exp -= shift;
 210   gcc_checking_assert (sig <= SREAL_MAX_SIG && sig >= SREAL_MIN_SIG);
 211
 212   /* Check underflow.  */
 213   if (new_exp < -SREAL_MAX_EXP)
 214     {
 215       new_exp = -SREAL_MAX_EXP;
 216       sig = 0;
 217     }
 218   m_exp = new_exp;
 219   if (SREAL_SIGN (new_sig) == -1)
 220     m_sig = -sig;
 221   else
 222     m_sig = sig;
 223 }
 224
 225 /* Make significant to be <= SREAL_MAX_SIG.
 226
 227    Make this separate method so inliner can handle hot path better.  */
 228
 229 inline void
 230 sreal::normalize_down (int64_t new_sig, signed int new_exp)
 231 {
 232   int last_bit;
 233   unsigned HOST_WIDE_INT sig = absu_hwi (new_sig);
 234   int shift = floor_log2 (sig) - SREAL_PART_BITS + 2;
 235
 236   gcc_checking_assert (shift > 0);
 237   last_bit = (sig >> (shift-1)) & 1;
 238   sig >>= shift;
 239   new_exp += shift;
 240   gcc_checking_assert (sig <= SREAL_MAX_SIG && sig >= SREAL_MIN_SIG);
 241
 242   /* Round the number.  */
 243   sig += last_bit;
 244   if (sig > SREAL_MAX_SIG)
 245     {
 246       sig >>= 1;
 247       new_exp++;
 248     }
 249
 250   /* Check overflow.  */
 251   if (new_exp > SREAL_MAX_EXP)
 252     {
 253       new_exp = SREAL_MAX_EXP;
 254       sig = SREAL_MAX_SIG;
 255     }
 256   m_exp = new_exp;
 257   if (SREAL_SIGN (new_sig) == -1)
 258     m_sig = -sig;
 259   else
 260     m_sig = sig;
 261 }
 262
 263 /* Normalize *this; the hot path.  */
 264
 265 inline void
 266 sreal::normalize (int64_t new_sig, signed int new_exp)
 267 {
 268   unsigned HOST_WIDE_INT sig = absu_hwi (new_sig);
 269
 270   if (sig == 0)
 271     {
 272       m_sig = 0;
 273       m_exp = -SREAL_MAX_EXP;
 274     }
 275   else if (sig > SREAL_MAX_SIG)
 276     normalize_down (new_sig, new_exp);
 277   else if (sig < SREAL_MIN_SIG)
 278     normalize_up (new_sig, new_exp);
 279   else
 280     {
 281       m_sig = new_sig;
 282       m_exp = new_exp;
 283     }
 284 }
 285
 286 #endif