softfloat/f64_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 float64_t f64_div( float64_t a, float64_t b )
  45 {
  46     union ui64_f64 uA;
  47     uint_fast64_t uiA;
  48     bool signA;
  49     int_fast16_t expA;
  50     uint_fast64_t sigA;
  51     union ui64_f64 uB;
  52     uint_fast64_t uiB;
  53     bool signB;
  54     int_fast16_t expB;
  55     uint_fast64_t sigB;
  56     bool signZ;
  57     struct exp16_sig64 normExpSig;
  58     int_fast16_t expZ;
  59     uint32_t recip32, sig32Z, doubleTerm;
  60     uint_fast64_t rem;
  61     uint32_t q;
  62     uint_fast64_t sigZ;
  63     uint_fast64_t uiZ;
  64     union ui64_f64 uZ;
  65
  66     /*------------------------------------------------------------------------
  67     *------------------------------------------------------------------------*/
  68     uA.f = a;
  69     uiA = uA.ui;
  70     signA = signF64UI( uiA );
  71     expA  = expF64UI( uiA );
  72     sigA  = fracF64UI( uiA );
  73     uB.f = b;
  74     uiB = uB.ui;
  75     signB = signF64UI( uiB );
  76     expB  = expF64UI( uiB );
  77     sigB  = fracF64UI( uiB );
  78     signZ = signA ^ signB;
  79     /*------------------------------------------------------------------------
  80     *------------------------------------------------------------------------*/
  81     if ( expA == 0x7FF ) {
  82         if ( sigA ) goto propagateNaN;
  83         if ( expB == 0x7FF ) {
  84             if ( sigB ) goto propagateNaN;
  85             goto invalid;
  86         }
  87         goto infinity;
  88     }
  89     if ( expB == 0x7FF ) {
  90         if ( sigB ) goto propagateNaN;
  91         goto zero;
  92     }
  93     /*------------------------------------------------------------------------
  94     *------------------------------------------------------------------------*/
  95     if ( ! expB ) {
  96         if ( ! sigB ) {
  97             if ( ! (expA | sigA) ) goto invalid;
  98             softfloat_raiseFlags( softfloat_flag_infinite );
  99             goto infinity;
 100         }
 101         normExpSig = softfloat_normSubnormalF64Sig( sigB );
 102         expB = normExpSig.exp;
 103         sigB = normExpSig.sig;
 104     }
 105     if ( ! expA ) {
 106         if ( ! sigA ) goto zero;
 107         normExpSig = softfloat_normSubnormalF64Sig( sigA );
 108         expA = normExpSig.exp;
 109         sigA = normExpSig.sig;
 110     }
 111     /*------------------------------------------------------------------------
 112     *------------------------------------------------------------------------*/
 113     expZ = expA - expB + 0x3FE;
 114     sigA |= UINT64_C( 0x0010000000000000 );
 115     sigB |= UINT64_C( 0x0010000000000000 );
 116     if ( sigA < sigB ) {
 117         --expZ;
 118         sigA <<= 11;
 119     } else {
 120         sigA <<= 10;
 121     }
 122     sigB <<= 11;
 123     recip32 = softfloat_approxRecip32_1( sigB>>32 ) - 2;
 124     sig32Z = ((uint32_t) (sigA>>32) * (uint_fast64_t) recip32)>>32;
 125     doubleTerm = sig32Z<<1;
 126     rem =
 127         ((sigA - (uint_fast64_t) doubleTerm * (uint32_t) (sigB>>32))<<28)
 128             - (uint_fast64_t) doubleTerm * ((uint32_t) sigB>>4);
 129     q = (((uint32_t) (rem>>32) * (uint_fast64_t) recip32)>>32) + 4;
 130     sigZ = ((uint_fast64_t) sig32Z<<32) + ((uint_fast64_t) q<<4);
 131     /*------------------------------------------------------------------------
 132     *------------------------------------------------------------------------*/
 133     if ( (sigZ & 0x1FF) < 4<<4 ) {
 134         q &= ~7;
 135         sigZ &= ~(uint_fast64_t) 0x7F;
 136         doubleTerm = q<<1;
 137         rem =
 138             ((rem - (uint_fast64_t) doubleTerm * (uint32_t) (sigB>>32))<<28)
 139                 - (uint_fast64_t) doubleTerm * ((uint32_t) sigB>>4);
 140         if ( rem & UINT64_C( 0x8000000000000000 ) ) {
 141             sigZ -= 1<<7;
 142         } else {
 143             if ( rem ) sigZ |= 1;
 144         }
 145     }
 146     return softfloat_roundPackToF64( signZ, expZ, sigZ );
 147     /*------------------------------------------------------------------------
 148     *------------------------------------------------------------------------*/
 149  propagateNaN:
 150     uiZ = softfloat_propagateNaNF64UI( uiA, uiB );
 151     goto uiZ;
 152     /*------------------------------------------------------------------------
 153     *------------------------------------------------------------------------*/
 154  invalid:
 155     softfloat_raiseFlags( softfloat_flag_invalid );
 156     uiZ = defaultNaNF64UI;
 157     goto uiZ;
 158     /*------------------------------------------------------------------------
 159     *------------------------------------------------------------------------*/
 160  infinity:
 161     uiZ = packToF64UI( signZ, 0x7FF, 0 );
 162     goto uiZ;
 163     /*------------------------------------------------------------------------
 164     *------------------------------------------------------------------------*/
 165  zero:
 166     uiZ = packToF64UI( signZ, 0, 0 );
 167  uiZ:
 168     uZ.ui = uiZ;
 169     return uZ.f;
 170
 171 }
 172