softfloat/f128_div.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 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 float128_t f128_div( float128_t a, float128_t b )
  45 {
  46     union ui128_f128 uA;
  47     uint_fast64_t uiA64, uiA0;
  48     bool signA;
  49     int_fast32_t expA;
  50     struct uint128 sigA;
  51     union ui128_f128 uB;
  52     uint_fast64_t uiB64, uiB0;
  53     bool signB;
  54     int_fast32_t expB;
  55     struct uint128 sigB;
  56     bool signZ;
  57     struct exp32_sig128 normExpSig;
  58     int_fast32_t expZ;
  59     struct uint128 rem;
  60     uint_fast32_t recip32;
  61     int ix;
  62     uint_fast64_t q64;
  63     uint_fast32_t q;
  64     struct uint128 term;
  65     uint_fast32_t qs[3];
  66     uint_fast64_t sigZExtra;
  67     struct uint128 sigZ, uiZ;
  68     union ui128_f128 uZ;
  69
  70     /*------------------------------------------------------------------------
  71     *------------------------------------------------------------------------*/
  72     uA.f = a;
  73     uiA64 = uA.ui.v64;
  74     uiA0  = uA.ui.v0;
  75     signA = signF128UI64( uiA64 );
  76     expA  = expF128UI64( uiA64 );
  77     sigA.v64 = fracF128UI64( uiA64 );
  78     sigA.v0  = uiA0;
  79     uB.f = b;
  80     uiB64 = uB.ui.v64;
  81     uiB0  = uB.ui.v0;
  82     signB = signF128UI64( uiB64 );
  83     expB  = expF128UI64( uiB64 );
  84     sigB.v64 = fracF128UI64( uiB64 );
  85     sigB.v0  = uiB0;
  86     signZ = signA ^ signB;
  87     /*------------------------------------------------------------------------
  88     *------------------------------------------------------------------------*/
  89     if ( expA == 0x7FFF ) {
  90         if ( sigA.v64 | sigA.v0 ) goto propagateNaN;
  91         if ( expB == 0x7FFF ) {
  92             if ( sigB.v64 | sigB.v0 ) goto propagateNaN;
  93             goto invalid;
  94         }
  95         goto infinity;
  96     }
  97     if ( expB == 0x7FFF ) {
  98         if ( sigB.v64 | sigB.v0 ) goto propagateNaN;
  99         goto zero;
 100     }
 101     /*------------------------------------------------------------------------
 102     *------------------------------------------------------------------------*/
 103     if ( ! expB ) {
 104         if ( ! (sigB.v64 | sigB.v0) ) {
 105             if ( ! (expA | sigA.v64 | sigA.v0) ) goto invalid;
 106             softfloat_raiseFlags( softfloat_flag_infinite );
 107             goto infinity;
 108         }
 109         normExpSig = softfloat_normSubnormalF128Sig( sigB.v64, sigB.v0 );
 110         expB = normExpSig.exp;
 111         sigB = normExpSig.sig;
 112     }
 113     if ( ! expA ) {
 114         if ( ! (sigA.v64 | sigA.v0) ) goto zero;
 115         normExpSig = softfloat_normSubnormalF128Sig( sigA.v64, sigA.v0 );
 116         expA = normExpSig.exp;
 117         sigA = normExpSig.sig;
 118     }
 119     /*------------------------------------------------------------------------
 120     *------------------------------------------------------------------------*/
 121     expZ = expA - expB + 0x3FFE;
 122     sigA.v64 |= UINT64_C( 0x0001000000000000 );
 123     sigB.v64 |= UINT64_C( 0x0001000000000000 );
 124     rem = sigA;
 125     if ( softfloat_lt128( sigA.v64, sigA.v0, sigB.v64, sigB.v0 ) ) {
 126         --expZ;
 127         rem = softfloat_add128( sigA.v64, sigA.v0, sigA.v64, sigA.v0 );
 128     }
 129     recip32 = softfloat_approxRecip32_1( sigB.v64>>17 );
 130     ix = 3;
 131     for (;;) {
 132         q64 = (uint_fast64_t) (uint32_t) (rem.v64>>19) * recip32;
 133         q = (q64 + 0x80000000)>>32;
 134         --ix;
 135         if ( ix < 0 ) break;
 136         rem = softfloat_shortShiftLeft128( rem.v64, rem.v0, 29 );
 137         term = softfloat_mul128By32( sigB.v64, sigB.v0, q );
 138         rem = softfloat_sub128( rem.v64, rem.v0, term.v64, term.v0 );
 139         if ( rem.v64 & UINT64_C( 0x8000000000000000 ) ) {
 140             --q;
 141             rem = softfloat_add128( rem.v64, rem.v0, sigB.v64, sigB.v0 );
 142         }
 143         qs[ix] = q;
 144     }
 145     /*------------------------------------------------------------------------
 146     *------------------------------------------------------------------------*/
 147     if ( ((q + 1) & 7) < 2 ) {
 148         rem = softfloat_shortShiftLeft128( rem.v64, rem.v0, 29 );
 149         term = softfloat_mul128By32( sigB.v64, sigB.v0, q );
 150         rem = softfloat_sub128( rem.v64, rem.v0, term.v64, term.v0 );
 151         if ( rem.v64 & UINT64_C( 0x8000000000000000 ) ) {
 152             --q;
 153             rem = softfloat_add128( rem.v64, rem.v0, sigB.v64, sigB.v0 );
 154         } else if ( softfloat_le128( sigB.v64, sigB.v0, rem.v64, rem.v0 ) ) {
 155             ++q;
 156             rem = softfloat_sub128( rem.v64, rem.v0, sigB.v64, sigB.v0 );
 157         }
 158         if ( rem.v64 | rem.v0 ) q |= 1;
 159     }
 160     /*------------------------------------------------------------------------
 161     *------------------------------------------------------------------------*/
 162     sigZExtra = (uint64_t) ((uint_fast64_t) q<<60);
 163     term = softfloat_shortShiftLeft128( 0, qs[1], 54 );
 164     sigZ =
 165         softfloat_add128(
 166             (uint_fast64_t) qs[2]<<19, ((uint_fast64_t) qs[0]<<25) + (q>>4),
 167             term.v64, term.v0
 168         );
 169     return
 170         softfloat_roundPackToF128( signZ, expZ, sigZ.v64, sigZ.v0, sigZExtra );
 171     /*------------------------------------------------------------------------
 172     *------------------------------------------------------------------------*/
 173  propagateNaN:
 174     uiZ = softfloat_propagateNaNF128UI( uiA64, uiA0, uiB64, uiB0 );
 175     goto uiZ;
 176     /*------------------------------------------------------------------------
 177     *------------------------------------------------------------------------*/
 178  invalid:
 179     softfloat_raiseFlags( softfloat_flag_invalid );
 180     uiZ.v64 = defaultNaNF128UI64;
 181     uiZ.v0  = defaultNaNF128UI0;
 182     goto uiZ;
 183     /*------------------------------------------------------------------------
 184     *------------------------------------------------------------------------*/
 185  infinity:
 186     uiZ.v64 = packToF128UI64( signZ, 0x7FFF, 0 );
 187     goto uiZ0;
 188     /*------------------------------------------------------------------------
 189     *------------------------------------------------------------------------*/
 190  zero:
 191     uiZ.v64 = packToF128UI64( signZ, 0, 0 );
 192  uiZ0:
 193     uiZ.v0 = 0;
 194  uiZ:
 195     uZ.ui = uiZ;
 196     return uZ.f;
 197
 198 }
 199