github.com/igggame/nebulas-go@v2.1.0+incompatible/nbre/3rd_party/SoftFloat-3e/source/f32_rem.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 The Regents of the University of California.
     8  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 "specialize.h"
    42  #include "softfloat.h"
    43  
    44  float32_t f32_rem( float32_t a, float32_t b )
    45  {
    46      union ui32_f32 uA;
    47      uint_fast32_t uiA;
    48      bool signA;
    49      int_fast16_t expA;
    50      uint_fast32_t sigA;
    51      union ui32_f32 uB;
    52      uint_fast32_t uiB;
    53      int_fast16_t expB;
    54      uint_fast32_t sigB;
    55      struct exp16_sig32 normExpSig;
    56      uint32_t rem;
    57      int_fast16_t expDiff;
    58      uint32_t q, recip32, altRem, meanRem;
    59      bool signRem;
    60      uint_fast32_t uiZ;
    61      union ui32_f32 uZ;
    62  
    63      /*------------------------------------------------------------------------
    64      *------------------------------------------------------------------------*/
    65      uA.f = a;
    66      uiA = uA.ui;
    67      signA = signF32UI( uiA );
    68      expA  = expF32UI( uiA );
    69      sigA  = fracF32UI( uiA );
    70      uB.f = b;
    71      uiB = uB.ui;
    72      expB = expF32UI( uiB );
    73      sigB = fracF32UI( uiB );
    74      /*------------------------------------------------------------------------
    75      *------------------------------------------------------------------------*/
    76      if ( expA == 0xFF ) {
    77          if ( sigA || ((expB == 0xFF) && sigB) ) goto propagateNaN;
    78          goto invalid;
    79      }
    80      if ( expB == 0xFF ) {
    81          if ( sigB ) goto propagateNaN;
    82          return a;
    83      }
    84      /*------------------------------------------------------------------------
    85      *------------------------------------------------------------------------*/
    86      if ( ! expB ) {
    87          if ( ! sigB ) goto invalid;
    88          normExpSig = softfloat_normSubnormalF32Sig( sigB );
    89          expB = normExpSig.exp;
    90          sigB = normExpSig.sig;
    91      }
    92      if ( ! expA ) {
    93          if ( ! sigA ) return a;
    94          normExpSig = softfloat_normSubnormalF32Sig( sigA );
    95          expA = normExpSig.exp;
    96          sigA = normExpSig.sig;
    97      }
    98      /*------------------------------------------------------------------------
    99      *------------------------------------------------------------------------*/
   100      rem = sigA | 0x00800000;
   101      sigB |= 0x00800000;
   102      expDiff = expA - expB;
   103      if ( expDiff < 1 ) {
   104          if ( expDiff < -1 ) return a;
   105          sigB <<= 6;
   106          if ( expDiff ) {
   107              rem <<= 5;
   108              q = 0;
   109          } else {
   110              rem <<= 6;
   111              q = (sigB <= rem);
   112              if ( q ) rem -= sigB;
   113          }
   114      } else {
   115          recip32 = softfloat_approxRecip32_1( sigB<<8 );
   116          /*--------------------------------------------------------------------
   117          | Changing the shift of `rem' here requires also changing the initial
   118          | subtraction from `expDiff'.
   119          *--------------------------------------------------------------------*/
   120          rem <<= 7;
   121          expDiff -= 31;
   122          /*--------------------------------------------------------------------
   123          | The scale of `sigB' affects how many bits are obtained during each
   124          | cycle of the loop.  Currently this is 29 bits per loop iteration,
   125          | which is believed to be the maximum possible.
   126          *--------------------------------------------------------------------*/
   127          sigB <<= 6;
   128          for (;;) {
   129              q = (rem * (uint_fast64_t) recip32)>>32;
   130              if ( expDiff < 0 ) break;
   131              rem = -(q * (uint32_t) sigB);
   132              expDiff -= 29;
   133          }
   134          /*--------------------------------------------------------------------
   135          | (`expDiff' cannot be less than -30 here.)
   136          *--------------------------------------------------------------------*/
   137          q >>= ~expDiff & 31;
   138          rem = (rem<<(expDiff + 30)) - q * (uint32_t) sigB;
   139      }
   140      /*------------------------------------------------------------------------
   141      *------------------------------------------------------------------------*/
   142      do {
   143          altRem = rem;
   144          ++q;
   145          rem -= sigB;
   146      } while ( ! (rem & 0x80000000) );
   147      meanRem = rem + altRem;
   148      if ( (meanRem & 0x80000000) || (! meanRem && (q & 1)) ) rem = altRem;
   149      signRem = signA;
   150      if ( 0x80000000 <= rem ) {
   151          signRem = ! signRem;
   152          rem = -rem;
   153      }
   154      return softfloat_normRoundPackToF32( signRem, expB, rem );
   155      /*------------------------------------------------------------------------
   156      *------------------------------------------------------------------------*/
   157   propagateNaN:
   158      uiZ = softfloat_propagateNaNF32UI( uiA, uiB );
   159      goto uiZ;
   160   invalid:
   161      softfloat_raiseFlags( softfloat_flag_invalid );
   162      uiZ = defaultNaNF32UI;
   163   uiZ:
   164      uZ.ui = uiZ;
   165      return uZ.f;
   166  
   167  }
   168