src/rintf.c

/*
*  Copyright (C) 2008-2009 Advanced Micro Devices, Inc. All Rights Reserved.
*
*  This file is part of libacml_mv.
*
*  libacml_mv is free software; you can redistribute it and/or
*  modify it under the terms of the GNU Lesser General Public
*  License as published by the Free Software Foundation; either
*  version 2.1 of the License, or (at your option) any later version.
*
*  libacml_mv is distributed in the hope that it will be useful,
*  but WITHOUT ANY WARRANTY; without even the implied warranty of
*  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
*  Lesser General Public License for more details.
*
*  You should have received a copy of the GNU Lesser General Public
*  License along with libacml_mv.  If not, see
*  <http://www.gnu.org/licenses/>.
*
*/


#include "libm_amd.h"
#include "libm_util_amd.h"



float FN_PROTOTYPE(rintf)(float x)
{

    UT32 checkbits,sign,val_2p23;
    checkbits.f32=x;

    /* Clear the sign bit and check if the value can be rounded */
    if( (checkbits.u32 & 0x7FFFFFFF) > 0x4B000000)
    {
      /* Number exceeds the representable range could be nan or inf also*/
      /* take care of nan or inf */
      if((checkbits.u32 & 0x7f800000)== 0x7f800000)
          return x+x;
      else
          return x;
    }

    sign.u32 =  checkbits.u32 & 0x80000000;
    val_2p23.u32 = (checkbits.u32 & 0x80000000) | 0x4B000000;

   /* Add and sub 2^23 to round the number according to the current rounding direction */
    val_2p23.f32  = ((x + val_2p23.f32) - val_2p23.f32);

    /*This extra line is to take care of denormals and various rounding modes*/
    val_2p23.u32 = ((val_2p23.u32 << 1) >> 1) | sign.u32;

    if (val_2p23.f32 != x)
    {
        /* Raise floating-point inexact exception if the result differs in value from the argument */
         checkbits.u32 = 0xFFC00000;
         checkbits.f32 = checkbits.f32 +  checkbits.f32;        /* raise inexact exception by adding two nan numbers.*/
    }


    return val_2p23.f32;
}