root/arch/mips/math-emu/dp_rint.c

DEFINITIONS

1. ieee754dp_rint

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* IEEE754 floating point arithmetic
   3  * double precision: common utilities
   4  */
   5 /*
   6  * MIPS floating point support
   7  * Copyright (C) 1994-2000 Algorithmics Ltd.
   8  * Copyright (C) 2017 Imagination Technologies, Ltd.
   9  * Author: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
  10  */
  11 
  12 #include "ieee754dp.h"
  13 
  14 union ieee754dp ieee754dp_rint(union ieee754dp x)
  15 {
  16         union ieee754dp ret;
  17         u64 residue;
  18         int sticky;
  19         int round;
  20         int odd;
  21 
  22         COMPXDP;
  23 
  24         ieee754_clearcx();
  25 
  26         EXPLODEXDP;
  27         FLUSHXDP;
  28 
  29         if (xc == IEEE754_CLASS_SNAN)
  30                 return ieee754dp_nanxcpt(x);
  31 
  32         if ((xc == IEEE754_CLASS_QNAN) ||
  33             (xc == IEEE754_CLASS_INF) ||
  34             (xc == IEEE754_CLASS_ZERO))
  35                 return x;
  36 
  37         if (xe >= DP_FBITS)
  38                 return x;
  39 
  40         if (xe < -1) {
  41                 residue = xm;
  42                 round = 0;
  43                 sticky = residue != 0;
  44                 xm = 0;
  45         } else {
  46                 residue = xm << (64 - DP_FBITS + xe);
  47                 round = (residue >> 63) != 0;
  48                 sticky = (residue << 1) != 0;
  49                 xm >>= DP_FBITS - xe;
  50         }
  51 
  52         odd = (xm & 0x1) != 0x0;
  53 
  54         switch (ieee754_csr.rm) {
  55         case FPU_CSR_RN:        /* toward nearest */
  56                 if (round && (sticky || odd))
  57                         xm++;
  58                 break;
  59         case FPU_CSR_RZ:        /* toward zero */
  60                 break;
  61         case FPU_CSR_RU:        /* toward +infinity */
  62                 if ((round || sticky) && !xs)
  63                         xm++;
  64                 break;
  65         case FPU_CSR_RD:        /* toward -infinity */
  66                 if ((round || sticky) && xs)
  67                         xm++;
  68                 break;
  69         }
  70 
  71         if (round || sticky)
  72                 ieee754_setcx(IEEE754_INEXACT);
  73 
  74         ret = ieee754dp_flong(xm);
  75         DPSIGN(ret) = xs;
  76 
  77         return ret;
  78 }