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      1 /* mpfr_add -- add two floating-point numbers
      2 
      3 Copyright 1999-2004, 2006-2023 Free Software Foundation, Inc.
      4 Contributed by the AriC and Caramba projects, INRIA.
      5 
      6 This file is part of the GNU MPFR Library.
      7 
      8 The GNU MPFR Library is free software; you can redistribute it and/or modify
      9 it under the terms of the GNU Lesser General Public License as published by
     10 the Free Software Foundation; either version 3 of the License, or (at your
     11 option) any later version.
     12 
     13 The GNU MPFR Library is distributed in the hope that it will be useful, but
     14 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
     15 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
     16 License for more details.
     17 
     18 You should have received a copy of the GNU Lesser General Public License
     19 along with the GNU MPFR Library; see the file COPYING.LESSER.  If not, see
     20 https://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
     21 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
     22 
     23 #include "mpfr-impl.h"
     24 
     25 MPFR_HOT_FUNCTION_ATTR int
     26 mpfr_add (mpfr_ptr a, mpfr_srcptr b, mpfr_srcptr c, mpfr_rnd_t rnd_mode)
     27 {
     28   MPFR_LOG_FUNC
     29     (("b[%Pd]=%.*Rg c[%Pd]=%.*Rg rnd=%d",
     30       mpfr_get_prec (b), mpfr_log_prec, b,
     31       mpfr_get_prec (c), mpfr_log_prec, c, rnd_mode),
     32      ("a[%Pd]=%.*Rg", mpfr_get_prec (a), mpfr_log_prec, a));
     33 
     34   if (MPFR_ARE_SINGULAR_OR_UBF (b, c))
     35     {
     36       if (MPFR_IS_NAN(b) || MPFR_IS_NAN(c))
     37         {
     38           MPFR_SET_NAN(a);
     39           MPFR_RET_NAN;
     40         }
     41       /* neither b nor c is NaN here */
     42       else if (MPFR_IS_INF(b))
     43         {
     44           if (!MPFR_IS_INF(c) || MPFR_SIGN(b) == MPFR_SIGN(c))
     45             {
     46               MPFR_SET_INF(a);
     47               MPFR_SET_SAME_SIGN(a, b);
     48               MPFR_RET(0); /* exact */
     49             }
     50           else
     51             {
     52               MPFR_SET_NAN(a);
     53               MPFR_RET_NAN;
     54             }
     55         }
     56       else if (MPFR_IS_INF(c))
     57           {
     58             MPFR_SET_INF(a);
     59             MPFR_SET_SAME_SIGN(a, c);
     60             MPFR_RET(0); /* exact */
     61           }
     62       /* now both b and c are finite numbers */
     63       else if (MPFR_IS_ZERO(b))
     64         {
     65           if (MPFR_IS_ZERO(c))
     66             {
     67               /* for round away, we take the same convention for 0 + 0
     68                  as for round to zero or to nearest: it always gives +0,
     69                  except (-0) + (-0) = -0. */
     70               MPFR_SET_SIGN(a,
     71                             (rnd_mode != MPFR_RNDD ?
     72                              (MPFR_IS_NEG(b) && MPFR_IS_NEG(c) ?
     73                               MPFR_SIGN_NEG : MPFR_SIGN_POS) :
     74                              (MPFR_IS_POS(b) && MPFR_IS_POS(c) ?
     75                               MPFR_SIGN_POS : MPFR_SIGN_NEG)));
     76               MPFR_SET_ZERO(a);
     77               MPFR_RET(0); /* 0 + 0 is exact */
     78             }
     79           return mpfr_set (a, c, rnd_mode);
     80         }
     81       else if (MPFR_IS_ZERO(c))
     82         {
     83           return mpfr_set (a, b, rnd_mode);
     84         }
     85       else
     86         {
     87           MPFR_ASSERTD (MPFR_IS_PURE_UBF (b));
     88           MPFR_ASSERTD (MPFR_IS_PURE_UBF (c));
     89           /* mpfr_sub1sp and mpfr_add1sp are not intended to support UBF,
     90              for which optimization is less important. */
     91           if (MPFR_SIGN(b) != MPFR_SIGN(c))
     92             return mpfr_sub1 (a, b, c, rnd_mode);
     93           else if (MPFR_UBF_EXP_LESS_P (b, c))
     94             return mpfr_add1 (a, c, b, rnd_mode);
     95           else
     96             return mpfr_add1 (a, b, c, rnd_mode);
     97         }
     98     }
     99 
    100   MPFR_ASSERTD (MPFR_IS_PURE_FP (b));
    101   MPFR_ASSERTD (MPFR_IS_PURE_FP (c));
    102 
    103   if (MPFR_UNLIKELY(MPFR_SIGN(b) != MPFR_SIGN(c)))
    104     { /* signs differ, it is a subtraction */
    105       if (MPFR_LIKELY(MPFR_PREC(a) == MPFR_PREC(b)
    106                       && MPFR_PREC(b) == MPFR_PREC(c)))
    107         return mpfr_sub1sp(a, b, c, rnd_mode);
    108       else
    109         return mpfr_sub1(a, b, c, rnd_mode);
    110     }
    111   else
    112     { /* signs are equal, it's an addition */
    113       if (MPFR_LIKELY(MPFR_PREC(a) == MPFR_PREC(b)
    114                       && MPFR_PREC(b) == MPFR_PREC(c)))
    115         return mpfr_add1sp(a, b, c, rnd_mode);
    116       else
    117         if (MPFR_GET_EXP(b) < MPFR_GET_EXP(c))
    118           return mpfr_add1(a, c, b, rnd_mode);
    119         else
    120           return mpfr_add1(a, b, c, rnd_mode);
    121     }
    122 }
    123