softfloat/s_subMagsF128.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 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 float128_t
  45  softfloat_subMagsF128(
  46      uint_fast64_t uiA64,
  47      uint_fast64_t uiA0,
  48      uint_fast64_t uiB64,
  49      uint_fast64_t uiB0,
  50      bool signZ
  51  )
  52 {
  53     int_fast32_t expA;
  54     struct uint128 sigA;
  55     int_fast32_t expB;
  56     struct uint128 sigB, sigZ;
  57     int_fast32_t expDiff, expZ;
  58     struct uint128 uiZ;
  59     union ui128_f128 uZ;
  60
  61     expA = expF128UI64( uiA64 );
  62     sigA.v64 = fracF128UI64( uiA64 );
  63     sigA.v0  = uiA0;
  64     expB = expF128UI64( uiB64 );
  65     sigB.v64 = fracF128UI64( uiB64 );
  66     sigB.v0  = uiB0;
  67     sigA = softfloat_shortShiftLeft128( sigA.v64, sigA.v0, 4 );
  68     sigB = softfloat_shortShiftLeft128( sigB.v64, sigB.v0, 4 );
  69     expDiff = expA - expB;
  70     if ( 0 < expDiff ) goto expABigger;
  71     if ( expDiff < 0 ) goto expBBigger;
  72     if ( expA == 0x7FFF ) {
  73         if ( sigA.v64 | sigA.v0 | sigB.v64 | sigB.v0 ) goto propagateNaN;
  74         softfloat_raiseFlags( softfloat_flag_invalid );
  75         uiZ.v64 = defaultNaNF128UI64;
  76         uiZ.v0  = defaultNaNF128UI0;
  77         goto uiZ;
  78     }
  79     expZ = expA;
  80     if ( ! expZ ) expZ = 1;
  81     if ( sigB.v64 < sigA.v64 ) goto aBigger;
  82     if ( sigA.v64 < sigB.v64 ) goto bBigger;
  83     if ( sigB.v0 < sigA.v0 ) goto aBigger;
  84     if ( sigA.v0 < sigB.v0 ) goto bBigger;
  85     uiZ.v64 =
  86         packToF128UI64(
  87             (softfloat_roundingMode == softfloat_round_min), 0, 0 );
  88     uiZ.v0 = 0;
  89     goto uiZ;
  90  expBBigger:
  91     if ( expB == 0x7FFF ) {
  92         if ( sigB.v64 | sigB.v0 ) goto propagateNaN;
  93         uiZ.v64 = packToF128UI64( signZ ^ 1, 0x7FFF, 0 );
  94         uiZ.v0  = 0;
  95         goto uiZ;
  96     }
  97     if ( expA ) {
  98         sigA.v64 |= UINT64_C( 0x0010000000000000 );
  99     } else {
 100         ++expDiff;
 101         if ( ! expDiff ) goto newlyAlignedBBigger;
 102     }
 103     sigA = softfloat_shiftRightJam128( sigA.v64, sigA.v0, -expDiff );
 104  newlyAlignedBBigger:
 105     expZ = expB;
 106     sigB.v64 |= UINT64_C( 0x0010000000000000 );
 107  bBigger:
 108     signZ = ! signZ;
 109     sigZ = softfloat_sub128( sigB.v64, sigB.v0, sigA.v64, sigA.v0 );
 110     goto normRoundPack;
 111  expABigger:
 112     if ( expA == 0x7FFF ) {
 113         if ( sigA.v64 | sigA.v0 ) goto propagateNaN;
 114         uiZ.v64 = uiA64;
 115         uiZ.v0  = uiA0;
 116         goto uiZ;
 117     }
 118     if ( expB ) {
 119         sigB.v64 |= UINT64_C( 0x0010000000000000 );
 120     } else {
 121         --expDiff;
 122         if ( ! expDiff ) goto newlyAlignedABigger;
 123     }
 124     sigB = softfloat_shiftRightJam128( sigB.v64, sigB.v0, expDiff );
 125  newlyAlignedABigger:
 126     expZ = expA;
 127     sigA.v64 |= UINT64_C( 0x0010000000000000 );
 128  aBigger:
 129     sigZ = softfloat_sub128( sigA.v64, sigA.v0, sigB.v64, sigB.v0 );
 130  normRoundPack:
 131     return softfloat_normRoundPackToF128( signZ, expZ - 5, sigZ.v64, sigZ.v0 );
 132  propagateNaN:
 133     uiZ = softfloat_propagateNaNF128UI( uiA64, uiA0, uiB64, uiB0 );
 134  uiZ:
 135     uZ.ui = uiZ;
 136     return uZ.f;
 137
 138 }
 139