softfloat/s_subMagsF32.c

   1
   2 /*============================================================================
   3
   4 This C source file is part of the SoftFloat IEEE Floating-Point Arithmetic
   5 Package, Release 3d, by John R. Hauser.
   6
   7 Copyright 2011, 2012, 2013, 2014, 2015, 2016 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 "specialize.h"
  42 #include "softfloat.h"
  43
  44 float32_t softfloat_subMagsF32( uint_fast32_t uiA, uint_fast32_t uiB )
  45 {
  46     int_fast16_t expA;
  47     uint_fast32_t sigA;
  48     int_fast16_t expB;
  49     uint_fast32_t sigB;
  50     int_fast16_t expDiff;
  51     uint_fast32_t uiZ;
  52     int_fast32_t sigDiff;
  53     bool signZ;
  54     int_fast8_t shiftDist;
  55     int_fast16_t expZ;
  56     uint_fast32_t sigX, sigY;
  57     union ui32_f32 uZ;
  58
  59     /*------------------------------------------------------------------------
  60     *------------------------------------------------------------------------*/
  61     expA = expF32UI( uiA );
  62     sigA = fracF32UI( uiA );
  63     expB = expF32UI( uiB );
  64     sigB = fracF32UI( uiB );
  65     /*------------------------------------------------------------------------
  66     *------------------------------------------------------------------------*/
  67     expDiff = expA - expB;
  68     if ( ! expDiff ) {
  69         /*--------------------------------------------------------------------
  70         *--------------------------------------------------------------------*/
  71         if ( expA == 0xFF ) {
  72             if ( sigA | sigB ) goto propagateNaN;
  73             softfloat_raiseFlags( softfloat_flag_invalid );
  74             uiZ = defaultNaNF32UI;
  75             goto uiZ;
  76         }
  77         sigDiff = sigA - sigB;
  78         if ( ! sigDiff ) {
  79             uiZ =
  80                 packToF32UI(
  81                     (softfloat_roundingMode == softfloat_round_min), 0, 0 );
  82             goto uiZ;
  83         }
  84         if ( expA ) --expA;
  85         signZ = signF32UI( uiA );
  86         if ( sigDiff < 0 ) {
  87             signZ = ! signZ;
  88             sigDiff = -sigDiff;
  89         }
  90         shiftDist = softfloat_countLeadingZeros32( sigDiff ) - 8;
  91         expZ = expA - shiftDist;
  92         if ( expZ < 0 ) {
  93             shiftDist = expA;
  94             expZ = 0;
  95         }
  96         uiZ = packToF32UI( signZ, expZ, sigDiff<<shiftDist );
  97         goto uiZ;
  98     } else {
  99         /*--------------------------------------------------------------------
 100         *--------------------------------------------------------------------*/
 101         signZ = signF32UI( uiA );
 102         sigA <<= 7;
 103         sigB <<= 7;
 104         if ( expDiff < 0 ) {
 105             /*----------------------------------------------------------------
 106             *----------------------------------------------------------------*/
 107             signZ = ! signZ;
 108             if ( expB == 0xFF ) {
 109                 if ( sigB ) goto propagateNaN;
 110                 uiZ = packToF32UI( signZ, 0xFF, 0 );
 111                 goto uiZ;
 112             }
 113             expZ = expB - 1;
 114             sigX = sigB | 0x40000000;
 115             sigY = sigA + (expA ? 0x40000000 : sigA);
 116             expDiff = -expDiff;
 117         } else {
 118             /*----------------------------------------------------------------
 119             *----------------------------------------------------------------*/
 120             if ( expA == 0xFF ) {
 121                 if ( sigA ) goto propagateNaN;
 122                 uiZ = uiA;
 123                 goto uiZ;
 124             }
 125             expZ = expA - 1;
 126             sigX = sigA | 0x40000000;
 127             sigY = sigB + (expB ? 0x40000000 : sigB);
 128         }
 129         return
 130             softfloat_normRoundPackToF32(
 131                 signZ, expZ, sigX - softfloat_shiftRightJam32( sigY, expDiff )
 132             );
 133     }
 134     /*------------------------------------------------------------------------
 135     *------------------------------------------------------------------------*/
 136  propagateNaN:
 137     uiZ = softfloat_propagateNaNF32UI( uiA, uiB );
 138  uiZ:
 139     uZ.ui = uiZ;
 140     return uZ.f;
 141
 142 }
 143