github.com/igggame/nebulas-go@v2.1.0+incompatible/nbre/3rd_party/SoftFloat-3e/source/s_roundPackToF128.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  float128_t
    44   softfloat_roundPackToF128(
    45       bool sign,
    46       int_fast32_t exp,
    47       uint_fast64_t sig64,
    48       uint_fast64_t sig0,
    49       uint_fast64_t sigExtra
    50   )
    51  {
    52      uint_fast8_t roundingMode;
    53      bool roundNearEven, doIncrement, isTiny;
    54      struct uint128_extra sig128Extra;
    55      uint_fast64_t uiZ64, uiZ0;
    56      struct uint128 sig128;
    57      union ui128_f128 uZ;
    58  
    59      /*------------------------------------------------------------------------
    60      *------------------------------------------------------------------------*/
    61      roundingMode = softfloat_roundingMode;
    62      roundNearEven = (roundingMode == softfloat_round_near_even);
    63      doIncrement = (UINT64_C( 0x8000000000000000 ) <= sigExtra);
    64      if ( ! roundNearEven && (roundingMode != softfloat_round_near_maxMag) ) {
    65          doIncrement =
    66              (roundingMode
    67                   == (sign ? softfloat_round_min : softfloat_round_max))
    68                  && sigExtra;
    69      }
    70      /*------------------------------------------------------------------------
    71      *------------------------------------------------------------------------*/
    72      if ( 0x7FFD <= (uint32_t) exp ) {
    73          if ( exp < 0 ) {
    74              /*----------------------------------------------------------------
    75              *----------------------------------------------------------------*/
    76              isTiny =
    77                     (softfloat_detectTininess
    78                          == softfloat_tininess_beforeRounding)
    79                  || (exp < -1)
    80                  || ! doIncrement
    81                  || softfloat_lt128(
    82                         sig64,
    83                         sig0,
    84                         UINT64_C( 0x0001FFFFFFFFFFFF ),
    85                         UINT64_C( 0xFFFFFFFFFFFFFFFF )
    86                     );
    87              sig128Extra =
    88                  softfloat_shiftRightJam128Extra( sig64, sig0, sigExtra, -exp );
    89              sig64 = sig128Extra.v.v64;
    90              sig0  = sig128Extra.v.v0;
    91              sigExtra = sig128Extra.extra;
    92              exp = 0;
    93              if ( isTiny && sigExtra ) {
    94                  softfloat_raiseFlags( softfloat_flag_underflow );
    95              }
    96              doIncrement = (UINT64_C( 0x8000000000000000 ) <= sigExtra);
    97              if (
    98                     ! roundNearEven
    99                  && (roundingMode != softfloat_round_near_maxMag)
   100              ) {
   101                  doIncrement =
   102                      (roundingMode
   103                           == (sign ? softfloat_round_min : softfloat_round_max))
   104                          && sigExtra;
   105              }
   106          } else if (
   107                 (0x7FFD < exp)
   108              || ((exp == 0x7FFD)
   109                      && softfloat_eq128( 
   110                             sig64,
   111                             sig0,
   112                             UINT64_C( 0x0001FFFFFFFFFFFF ),
   113                             UINT64_C( 0xFFFFFFFFFFFFFFFF )
   114                         )
   115                      && doIncrement)
   116          ) {
   117              /*----------------------------------------------------------------
   118              *----------------------------------------------------------------*/
   119              softfloat_raiseFlags(
   120                  softfloat_flag_overflow | softfloat_flag_inexact );
   121              if (
   122                     roundNearEven
   123                  || (roundingMode == softfloat_round_near_maxMag)
   124                  || (roundingMode
   125                          == (sign ? softfloat_round_min : softfloat_round_max))
   126              ) {
   127                  uiZ64 = packToF128UI64( sign, 0x7FFF, 0 );
   128                  uiZ0  = 0;
   129              } else {
   130                  uiZ64 =
   131                      packToF128UI64(
   132                          sign, 0x7FFE, UINT64_C( 0x0000FFFFFFFFFFFF ) );
   133                  uiZ0 = UINT64_C( 0xFFFFFFFFFFFFFFFF );
   134              }
   135              goto uiZ;
   136          }
   137      }
   138      /*------------------------------------------------------------------------
   139      *------------------------------------------------------------------------*/
   140      if ( sigExtra ) {
   141          softfloat_exceptionFlags |= softfloat_flag_inexact;
   142  #ifdef SOFTFLOAT_ROUND_ODD
   143          if ( roundingMode == softfloat_round_odd ) {
   144              sig0 |= 1;
   145              goto packReturn;
   146          }
   147  #endif
   148      }
   149      if ( doIncrement ) {
   150          sig128 = softfloat_add128( sig64, sig0, 0, 1 );
   151          sig64 = sig128.v64;
   152          sig0 =
   153              sig128.v0
   154                  & ~(uint64_t)
   155                         (! (sigExtra & UINT64_C( 0x7FFFFFFFFFFFFFFF ))
   156                              & roundNearEven);
   157      } else {
   158          if ( ! (sig64 | sig0) ) exp = 0;
   159      }
   160      /*------------------------------------------------------------------------
   161      *------------------------------------------------------------------------*/
   162   packReturn:
   163      uiZ64 = packToF128UI64( sign, exp, sig64 );
   164      uiZ0  = sig0;
   165   uiZ:
   166      uZ.ui.v64 = uiZ64;
   167      uZ.ui.v0  = uiZ0;
   168      return uZ.f;
   169  
   170  }
   171