arch/mips/math-emu/sp_rint.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* IEEE754 floating point arithmetic
   3  * single precision
   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 "ieee754sp.h"
  13
  14 union ieee754sp ieee754sp_rint(union ieee754sp x)
  15 {
  16         union ieee754sp ret;
  17         u32 residue;
  18         int sticky;
  19         int round;
  20         int odd;
  21
  22         COMPXDP;                /* <-- DP needed for 64-bit mantissa tmp */
  23
  24         ieee754_clearcx();
  25
  26         EXPLODEXSP;
  27         FLUSHXSP;
  28
  29         if (xc == IEEE754_CLASS_SNAN)
  30                 return ieee754sp_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 >= SP_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 << (xe + 1);
  47                 residue <<= 31 - SP_FBITS;
  48                 round = (residue >> 31) != 0;
  49                 sticky = (residue << 1) != 0;
  50                 xm >>= SP_FBITS - xe;
  51         }
  52
  53         odd = (xm & 0x1) != 0x0;
  54
  55         switch (ieee754_csr.rm) {
  56         case FPU_CSR_RN:        /* toward nearest */
  57                 if (round && (sticky || odd))
  58                         xm++;
  59                 break;
  60         case FPU_CSR_RZ:        /* toward zero */
  61                 break;
  62         case FPU_CSR_RU:        /* toward +infinity */
  63                 if ((round || sticky) && !xs)
  64                         xm++;
  65                 break;
  66         case FPU_CSR_RD:        /* toward -infinity */
  67                 if ((round || sticky) && xs)
  68                         xm++;
  69                 break;
  70         }
  71
  72         if (round || sticky)
  73                 ieee754_setcx(IEEE754_INEXACT);
  74
  75         ret = ieee754sp_flong(xm);
  76         SPSIGN(ret) = xs;
  77
  78         return ret;
  79 }