softfloat/source/s_subMagsExtF80.c

   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 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 extFloat80_t
  45  softfloat_subMagsExtF80(
  46      uint_fast16_t uiA64,
  47      uint_fast64_t uiA0,
  48      uint_fast16_t uiB64,
  49      uint_fast64_t uiB0,
  50      bool signZ
  51  )
  52 {
  53     int_fast32_t expA;
  54     uint_fast64_t sigA;
  55     int_fast32_t expB;
  56     uint_fast64_t sigB;
  57     int_fast32_t expDiff;
  58     uint_fast16_t uiZ64;
  59     uint_fast64_t uiZ0;
  60     int_fast32_t expZ;
  61     uint_fast64_t sigExtra;
  62     struct uint128 sig128, uiZ;
  63     union { struct extFloat80M s; extFloat80_t f; } uZ;
  64
  65     /*------------------------------------------------------------------------
  66     *------------------------------------------------------------------------*/
  67     expA = expExtF80UI64( uiA64 );
  68     sigA = uiA0;
  69     expB = expExtF80UI64( uiB64 );
  70     sigB = uiB0;
  71     /*------------------------------------------------------------------------
  72     *------------------------------------------------------------------------*/
  73     expDiff = expA - expB;
  74     if ( 0 < expDiff ) goto expABigger;
  75     if ( expDiff < 0 ) goto expBBigger;
  76     if ( expA == 0x7FFF ) {
  77         if ( (sigA | sigB) & UINT64_C( 0x7FFFFFFFFFFFFFFF ) ) {
  78             goto propagateNaN;
  79         }
  80         softfloat_raiseFlags( softfloat_flag_invalid );
  81         uiZ64 = defaultNaNExtF80UI64;
  82         uiZ0  = defaultNaNExtF80UI0;
  83         goto uiZ;
  84     }
  85     /*------------------------------------------------------------------------
  86     *------------------------------------------------------------------------*/
  87     expZ = expA;
  88     if ( ! expZ ) expZ = 1;
  89     sigExtra = 0;
  90     if ( sigB < sigA ) goto aBigger;
  91     if ( sigA < sigB ) goto bBigger;
  92     uiZ64 =
  93         packToExtF80UI64( (softfloat_roundingMode == softfloat_round_min), 0 );
  94     uiZ0 = 0;
  95     goto uiZ;
  96     /*------------------------------------------------------------------------
  97     *------------------------------------------------------------------------*/
  98  expBBigger:
  99     if ( expB == 0x7FFF ) {
 100         if ( sigB & UINT64_C( 0x7FFFFFFFFFFFFFFF ) ) goto propagateNaN;
 101         uiZ64 = packToExtF80UI64( signZ ^ 1, 0x7FFF );
 102         uiZ0  = UINT64_C( 0x8000000000000000 );
 103         goto uiZ;
 104     }
 105     if ( ! expA ) {
 106         ++expDiff;
 107         sigExtra = 0;
 108         if ( ! expDiff ) goto newlyAlignedBBigger;
 109     }
 110     sig128 = softfloat_shiftRightJam128( sigA, 0, -expDiff );
 111     sigA = sig128.v64;
 112     sigExtra = sig128.v0;
 113  newlyAlignedBBigger:
 114     expZ = expB;
 115  bBigger:
 116     signZ = ! signZ;
 117     sig128 = softfloat_sub128( sigB, 0, sigA, sigExtra );
 118     goto normRoundPack;
 119     /*------------------------------------------------------------------------
 120     *------------------------------------------------------------------------*/
 121  expABigger:
 122     if ( expA == 0x7FFF ) {
 123         if ( sigA & UINT64_C( 0x7FFFFFFFFFFFFFFF ) ) goto propagateNaN;
 124         uiZ64 = uiA64;
 125         uiZ0  = uiA0;
 126         goto uiZ;
 127     }
 128     if ( ! expB ) {
 129         --expDiff;
 130         sigExtra = 0;
 131         if ( ! expDiff ) goto newlyAlignedABigger;
 132     }
 133     sig128 = softfloat_shiftRightJam128( sigB, 0, expDiff );
 134     sigB = sig128.v64;
 135     sigExtra = sig128.v0;
 136  newlyAlignedABigger:
 137     expZ = expA;
 138  aBigger:
 139     sig128 = softfloat_sub128( sigA, 0, sigB, sigExtra );
 140     /*------------------------------------------------------------------------
 141     *------------------------------------------------------------------------*/
 142  normRoundPack:
 143     return
 144         softfloat_normRoundPackToExtF80(
 145             signZ, expZ, sig128.v64, sig128.v0, extF80_roundingPrecision );
 146     /*------------------------------------------------------------------------
 147     *------------------------------------------------------------------------*/
 148  propagateNaN:
 149     uiZ = softfloat_propagateNaNExtF80UI( uiA64, uiA0, uiB64, uiB0 );
 150     uiZ64 = uiZ.v64;
 151     uiZ0  = uiZ.v0;
 152  uiZ:
 153     uZ.s.signExp = uiZ64;
 154     uZ.s.signif  = uiZ0;
 155     return uZ.f;
 156
 157 }
 158