softfloat/f16_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, 2015, 2016 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 extern const uint16_t softfloat_approxRecip_1k0s[];
  45 extern const uint16_t softfloat_approxRecip_1k1s[];
  46
  47 float16_t f16_div( float16_t a, float16_t b )
  48 {
  49     union ui16_f16 uA;
  50     uint_fast16_t uiA;
  51     bool signA;
  52     int_fast8_t expA;
  53     uint_fast16_t sigA;
  54     union ui16_f16 uB;
  55     uint_fast16_t uiB;
  56     bool signB;
  57     int_fast8_t expB;
  58     uint_fast16_t sigB;
  59     bool signZ;
  60     struct exp8_sig16 normExpSig;
  61     int_fast8_t expZ;
  62 #ifdef SOFTFLOAT_FAST_DIV32TO16
  63     uint_fast32_t sig32A;
  64     uint_fast16_t sigZ;
  65 #else
  66     int index;
  67     uint16_t r0;
  68     uint_fast16_t sigZ, rem;
  69 #endif
  70     uint_fast16_t uiZ;
  71     union ui16_f16 uZ;
  72
  73     /*------------------------------------------------------------------------
  74     *------------------------------------------------------------------------*/
  75     uA.f = a;
  76     uiA = uA.ui;
  77     signA = signF16UI( uiA );
  78     expA  = expF16UI( uiA );
  79     sigA  = fracF16UI( uiA );
  80     uB.f = b;
  81     uiB = uB.ui;
  82     signB = signF16UI( uiB );
  83     expB  = expF16UI( uiB );
  84     sigB  = fracF16UI( uiB );
  85     signZ = signA ^ signB;
  86     /*------------------------------------------------------------------------
  87     *------------------------------------------------------------------------*/
  88     if ( expA == 0x1F ) {
  89         if ( sigA ) goto propagateNaN;
  90         if ( expB == 0x1F ) {
  91             if ( sigB ) goto propagateNaN;
  92             goto invalid;
  93         }
  94         goto infinity;
  95     }
  96     if ( expB == 0x1F ) {
  97         if ( sigB ) goto propagateNaN;
  98         goto zero;
  99     }
 100     /*------------------------------------------------------------------------
 101     *------------------------------------------------------------------------*/
 102     if ( ! expB ) {
 103         if ( ! sigB ) {
 104             if ( ! (expA | sigA) ) goto invalid;
 105             softfloat_raiseFlags( softfloat_flag_infinite );
 106             goto infinity;
 107         }
 108         normExpSig = softfloat_normSubnormalF16Sig( sigB );
 109         expB = normExpSig.exp;
 110         sigB = normExpSig.sig;
 111     }
 112     if ( ! expA ) {
 113         if ( ! sigA ) goto zero;
 114         normExpSig = softfloat_normSubnormalF16Sig( sigA );
 115         expA = normExpSig.exp;
 116         sigA = normExpSig.sig;
 117     }
 118     /*------------------------------------------------------------------------
 119     *------------------------------------------------------------------------*/
 120     expZ = expA - expB + 0xE;
 121     sigA |= 0x0400;
 122     sigB |= 0x0400;
 123 #ifdef SOFTFLOAT_FAST_DIV32TO16
 124     if ( sigA < sigB ) {
 125         --expZ;
 126         sig32A = (uint_fast32_t) sigA<<15;
 127     } else {
 128         sig32A = (uint_fast32_t) sigA<<14;
 129     }
 130     sigZ = sig32A / sigB;
 131     if ( ! (sigZ & 7) ) sigZ |= ((uint_fast32_t) sigB * sigZ != sig32A);
 132 #else
 133     if ( sigA < sigB ) {
 134         --expZ;
 135         sigA <<= 5;
 136     } else {
 137         sigA <<= 4;
 138     }
 139     index = sigB>>6 & 0xF;
 140     r0 = softfloat_approxRecip_1k0s[index]
 141              - (((uint_fast32_t) softfloat_approxRecip_1k1s[index]
 142                      * (sigB & 0x3F))
 143                     >>10);
 144     sigZ = ((uint_fast32_t) sigA * r0)>>16;
 145     rem = (sigA<<10) - sigZ * sigB;
 146     sigZ += (rem * (uint_fast32_t) r0)>>26;
 147     /*------------------------------------------------------------------------
 148     *------------------------------------------------------------------------*/
 149     ++sigZ;
 150     if ( ! (sigZ & 7) ) {
 151         sigZ &= ~1;
 152         rem = (sigA<<10) - sigZ * sigB;
 153         if ( rem & 0x8000 ) {
 154             sigZ -= 2;
 155         } else {
 156             if ( rem ) sigZ |= 1;
 157         }
 158     }
 159 #endif
 160     return softfloat_roundPackToF16( signZ, expZ, sigZ );
 161     /*------------------------------------------------------------------------
 162     *------------------------------------------------------------------------*/
 163  propagateNaN:
 164     uiZ = softfloat_propagateNaNF16UI( uiA, uiB );
 165     goto uiZ;
 166     /*------------------------------------------------------------------------
 167     *------------------------------------------------------------------------*/
 168  invalid:
 169     softfloat_raiseFlags( softfloat_flag_invalid );
 170     uiZ = defaultNaNF16UI;
 171     goto uiZ;
 172     /*------------------------------------------------------------------------
 173     *------------------------------------------------------------------------*/
 174  infinity:
 175     uiZ = packToF16UI( signZ, 0x1F, 0 );
 176     goto uiZ;
 177     /*------------------------------------------------------------------------
 178     *------------------------------------------------------------------------*/
 179  zero:
 180     uiZ = packToF16UI( signZ, 0, 0 );
 181  uiZ:
 182     uZ.ui = uiZ;
 183     return uZ.f;
 184
 185 }
 186