softfloat/s_addMagsF16.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, 2017 The Regents of the
   8 University of 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 float16_t softfloat_addMagsF16( uint_fast16_t uiA, uint_fast16_t uiB )
  45 {
  46     int_fast8_t expA;
  47     uint_fast16_t sigA;
  48     int_fast8_t expB;
  49     uint_fast16_t sigB;
  50     int_fast8_t expDiff;
  51     uint_fast16_t uiZ;
  52     bool signZ;
  53     int_fast8_t expZ;
  54     uint_fast16_t sigZ;
  55     uint_fast16_t sigX, sigY;
  56     int_fast8_t shiftDist;
  57     uint_fast32_t sig32Z;
  58     int_fast8_t roundingMode;
  59     union ui16_f16 uZ;
  60
  61     /*------------------------------------------------------------------------
  62     *------------------------------------------------------------------------*/
  63     expA = expF16UI( uiA );
  64     sigA = fracF16UI( uiA );
  65     expB = expF16UI( uiB );
  66     sigB = fracF16UI( uiB );
  67     /*------------------------------------------------------------------------
  68     *------------------------------------------------------------------------*/
  69     expDiff = expA - expB;
  70     if ( ! expDiff ) {
  71         /*--------------------------------------------------------------------
  72         *--------------------------------------------------------------------*/
  73         if ( ! expA ) {
  74             uiZ = uiA + sigB;
  75             goto uiZ;
  76         }
  77         if ( expA == 0x1F ) {
  78             if ( sigA | sigB ) goto propagateNaN;
  79             uiZ = uiA;
  80             goto uiZ;
  81         }
  82         signZ = signF16UI( uiA );
  83         expZ = expA;
  84         sigZ = 0x0800 + sigA + sigB;
  85         if ( ! (sigZ & 1) && (expZ < 0x1E) ) {
  86             sigZ >>= 1;
  87             goto pack;
  88         }
  89         sigZ <<= 3;
  90     } else {
  91         /*--------------------------------------------------------------------
  92         *--------------------------------------------------------------------*/
  93         signZ = signF16UI( uiA );
  94         if ( expDiff < 0 ) {
  95             /*----------------------------------------------------------------
  96             *----------------------------------------------------------------*/
  97             if ( expB == 0x1F ) {
  98                 if ( sigB ) goto propagateNaN;
  99                 uiZ = packToF16UI( signZ, 0x1F, 0 );
 100                 goto uiZ;
 101             }
 102             if ( expDiff <= -13 ) {
 103                 uiZ = packToF16UI( signZ, expB, sigB );
 104                 if ( expA | sigA ) goto addEpsilon;
 105                 goto uiZ;
 106             }
 107             expZ = expB;
 108             sigX = sigB | 0x0400;
 109             sigY = sigA + (expA ? 0x0400 : sigA);
 110             shiftDist = 19 + expDiff;
 111         } else {
 112             /*----------------------------------------------------------------
 113             *----------------------------------------------------------------*/
 114             uiZ = uiA;
 115             if ( expA == 0x1F ) {
 116                 if ( sigA ) goto propagateNaN;
 117                 goto uiZ;
 118             }
 119             if ( 13 <= expDiff ) {
 120                 if ( expB | sigB ) goto addEpsilon;
 121                 goto uiZ;
 122             }
 123             expZ = expA;
 124             sigX = sigA | 0x0400;
 125             sigY = sigB + (expB ? 0x0400 : sigB);
 126             shiftDist = 19 - expDiff;
 127         }
 128         sig32Z =
 129             ((uint_fast32_t) sigX<<19) + ((uint_fast32_t) sigY<<shiftDist);
 130         if ( sig32Z < 0x40000000 ) {
 131             --expZ;
 132             sig32Z <<= 1;
 133         }
 134         sigZ = sig32Z>>16;
 135         if ( sig32Z & 0xFFFF ) {
 136             sigZ |= 1;
 137         } else {
 138             if ( ! (sigZ & 0xF) && (expZ < 0x1E) ) {
 139                 sigZ >>= 4;
 140                 goto pack;
 141             }
 142         }
 143     }
 144     return softfloat_roundPackToF16( signZ, expZ, sigZ );
 145     /*------------------------------------------------------------------------
 146     *------------------------------------------------------------------------*/
 147  propagateNaN:
 148     uiZ = softfloat_propagateNaNF16UI( uiA, uiB );
 149     goto uiZ;
 150     /*------------------------------------------------------------------------
 151     *------------------------------------------------------------------------*/
 152  addEpsilon:
 153     roundingMode = softfloat_roundingMode;
 154     if ( roundingMode != softfloat_round_near_even ) {
 155         if (
 156             roundingMode
 157                 == (signF16UI( uiZ ) ? softfloat_round_min
 158                         : softfloat_round_max)
 159         ) {
 160             ++uiZ;
 161             if ( (uint16_t) (uiZ<<1) == 0xF800 ) {
 162                 softfloat_raiseFlags(
 163                     softfloat_flag_overflow | softfloat_flag_inexact );
 164             }
 165         }
 166 #ifdef SOFTFLOAT_ROUND_ODD
 167         else if ( roundingMode == softfloat_round_odd ) {
 168             uiZ |= 1;
 169         }
 170 #endif
 171     }
 172     softfloat_exceptionFlags |= softfloat_flag_inexact;
 173     goto uiZ;
 174     /*------------------------------------------------------------------------
 175     *------------------------------------------------------------------------*/
 176  pack:
 177     uiZ = packToF16UI( signZ, expZ, sigZ );
 178  uiZ:
 179     uZ.ui = uiZ;
 180     return uZ.f;
 181
 182 }
 183