github.com/igggame/nebulas-go@v2.1.0+incompatible/nbre/3rd_party/SoftFloat-3e/source/s_roundPackToF64.c (about)

     1  
     2  /*============================================================================
     3  
     4  This C source file is part of the SoftFloat IEEE Floating-Point Arithmetic
     5  Package, Release 3e, by John R. Hauser.
     6  
     7  Copyright 2011, 2012, 2013, 2014, 2015, 2017 The Regents of the University of
     8  California.  All rights reserved.
     9  
    10  Redistribution and use in source and binary forms, with or without
    11  modification, are permitted provided that the following conditions are met:
    12  
    13   1. Redistributions of source code must retain the above copyright notice,
    14      this list of conditions, and the following disclaimer.
    15  
    16   2. Redistributions in binary form must reproduce the above copyright notice,
    17      this list of conditions, and the following disclaimer in the documentation
    18      and/or other materials provided with the distribution.
    19  
    20   3. Neither the name of the University nor the names of its contributors may
    21      be used to endorse or promote products derived from this software without
    22      specific prior written permission.
    23  
    24  THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS "AS IS", AND ANY
    25  EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
    26  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ARE
    27  DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
    28  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
    29  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
    30  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
    31  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    32  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
    33  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
    34  
    35  =============================================================================*/
    36  
    37  #include <stdbool.h>
    38  #include <stdint.h>
    39  #include "platform.h"
    40  #include "internals.h"
    41  #include "softfloat.h"
    42  
    43  float64_t
    44   softfloat_roundPackToF64( bool sign, int_fast16_t exp, uint_fast64_t sig )
    45  {
    46      uint_fast8_t roundingMode;
    47      bool roundNearEven;
    48      uint_fast16_t roundIncrement, roundBits;
    49      bool isTiny;
    50      uint_fast64_t uiZ;
    51      union ui64_f64 uZ;
    52  
    53      /*------------------------------------------------------------------------
    54      *------------------------------------------------------------------------*/
    55      roundingMode = softfloat_roundingMode;
    56      roundNearEven = (roundingMode == softfloat_round_near_even);
    57      roundIncrement = 0x200;
    58      if ( ! roundNearEven && (roundingMode != softfloat_round_near_maxMag) ) {
    59          roundIncrement =
    60              (roundingMode
    61                   == (sign ? softfloat_round_min : softfloat_round_max))
    62                  ? 0x3FF
    63                  : 0;
    64      }
    65      roundBits = sig & 0x3FF;
    66      /*------------------------------------------------------------------------
    67      *------------------------------------------------------------------------*/
    68      if ( 0x7FD <= (uint16_t) exp ) {
    69          if ( exp < 0 ) {
    70              /*----------------------------------------------------------------
    71              *----------------------------------------------------------------*/
    72              isTiny =
    73                  (softfloat_detectTininess == softfloat_tininess_beforeRounding)
    74                      || (exp < -1)
    75                      || (sig + roundIncrement < UINT64_C( 0x8000000000000000 ));
    76              sig = softfloat_shiftRightJam64( sig, -exp );
    77              exp = 0;
    78              roundBits = sig & 0x3FF;
    79              if ( isTiny && roundBits ) {
    80                  softfloat_raiseFlags( softfloat_flag_underflow );
    81              }
    82          } else if (
    83              (0x7FD < exp)
    84                  || (UINT64_C( 0x8000000000000000 ) <= sig + roundIncrement)
    85          ) {
    86              /*----------------------------------------------------------------
    87              *----------------------------------------------------------------*/
    88              softfloat_raiseFlags(
    89                  softfloat_flag_overflow | softfloat_flag_inexact );
    90              uiZ = packToF64UI( sign, 0x7FF, 0 ) - ! roundIncrement;
    91              goto uiZ;
    92          }
    93      }
    94      /*------------------------------------------------------------------------
    95      *------------------------------------------------------------------------*/
    96      sig = (sig + roundIncrement)>>10;
    97      if ( roundBits ) {
    98          softfloat_exceptionFlags |= softfloat_flag_inexact;
    99  #ifdef SOFTFLOAT_ROUND_ODD
   100          if ( roundingMode == softfloat_round_odd ) {
   101              sig |= 1;
   102              goto packReturn;
   103          }
   104  #endif
   105      }
   106      sig &= ~(uint_fast64_t) (! (roundBits ^ 0x200) & roundNearEven);
   107      if ( ! sig ) exp = 0;
   108      /*------------------------------------------------------------------------
   109      *------------------------------------------------------------------------*/
   110   packReturn:
   111      uiZ = packToF64UI( sign, exp, sig );
   112   uiZ:
   113      uZ.ui = uiZ;
   114      return uZ.f;
   115  
   116  }
   117