arch/mips/math-emu/dp_rint.c

   1 /* IEEE754 floating point arithmetic
   2  * double precision: common utilities
   3  */
   4 /*
   5  * MIPS floating point support
   6  * Copyright (C) 1994-2000 Algorithmics Ltd.
   7  * Copyright (C) 2017 Imagination Technologies, Ltd.
   8  * Author: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
   9  *
  10  *  This program is free software; you can distribute it and/or modify it
  11  *  under the terms of the GNU General Public License (Version 2) as
  12  *  published by the Free Software Foundation.
  13  *
  14  *  This program is distributed in the hope it will be useful, but WITHOUT
  15  *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  16  *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  17  *  for more details.
  18  *
  19  *  You should have received a copy of the GNU General Public License along
  20  *  with this program.
  21  */
  22
  23 #include "ieee754dp.h"
  24
  25 union ieee754dp ieee754dp_rint(union ieee754dp x)
  26 {
  27         union ieee754dp ret;
  28         u64 residue;
  29         int sticky;
  30         int round;
  31         int odd;
  32
  33         COMPXDP;
  34
  35         ieee754_clearcx();
  36
  37         EXPLODEXDP;
  38         FLUSHXDP;
  39
  40         if (xc == IEEE754_CLASS_SNAN)
  41                 return ieee754dp_nanxcpt(x);
  42
  43         if ((xc == IEEE754_CLASS_QNAN) ||
  44             (xc == IEEE754_CLASS_INF) ||
  45             (xc == IEEE754_CLASS_ZERO))
  46                 return x;
  47
  48         if (xe >= DP_FBITS)
  49                 return x;
  50
  51         if (xe < -1) {
  52                 residue = xm;
  53                 round = 0;
  54                 sticky = residue != 0;
  55                 xm = 0;
  56         } else {
  57                 residue = xm << (64 - DP_FBITS + xe);
  58                 round = (residue >> 63) != 0;
  59                 sticky = (residue << 1) != 0;
  60                 xm >>= DP_FBITS - xe;
  61         }
  62
  63         odd = (xm & 0x1) != 0x0;
  64
  65         switch (ieee754_csr.rm) {
  66         case FPU_CSR_RN:        /* toward nearest */
  67                 if (round && (sticky || odd))
  68                         xm++;
  69                 break;
  70         case FPU_CSR_RZ:        /* toward zero */
  71                 break;
  72         case FPU_CSR_RU:        /* toward +infinity */
  73                 if ((round || sticky) && !xs)
  74                         xm++;
  75                 break;
  76         case FPU_CSR_RD:        /* toward -infinity */
  77                 if ((round || sticky) && xs)
  78                         xm++;
  79                 break;
  80         }
  81
  82         if (round || sticky)
  83                 ieee754_setcx(IEEE754_INEXACT);
  84
  85         ret = ieee754dp_flong(xm);
  86         DPSIGN(ret) = xs;
  87
  88         return ret;
  89 }