LXR linux/arch/mips/math-emu/dp

   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
  25union 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}
  90