softfloat/f16_mul.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 float16_t f16_mul( float16_t a, float16_t b )
  45 {
  46     union ui16_f16 uA;
  47     uint_fast16_t uiA;
  48     bool signA;
  49     int_fast8_t expA;
  50     uint_fast16_t sigA;
  51     union ui16_f16 uB;
  52     uint_fast16_t uiB;
  53     bool signB;
  54     int_fast8_t expB;
  55     uint_fast16_t sigB;
  56     bool signZ;
  57     uint_fast16_t magBits;
  58     struct exp8_sig16 normExpSig;
  59     int_fast8_t expZ;
  60     uint_fast32_t sig32Z;
  61     uint_fast16_t sigZ, uiZ;
  62     union ui16_f16 uZ;
  63
  64     /*------------------------------------------------------------------------
  65     *------------------------------------------------------------------------*/
  66     uA.f = a;
  67     uiA = uA.ui;
  68     signA = signF16UI( uiA );
  69     expA  = expF16UI( uiA );
  70     sigA  = fracF16UI( uiA );
  71     uB.f = b;
  72     uiB = uB.ui;
  73     signB = signF16UI( uiB );
  74     expB  = expF16UI( uiB );
  75     sigB  = fracF16UI( uiB );
  76     signZ = signA ^ signB;
  77     /*------------------------------------------------------------------------
  78     *------------------------------------------------------------------------*/
  79     if ( expA == 0x1F ) {
  80         if ( sigA || ((expB == 0x1F) && sigB) ) goto propagateNaN;
  81         magBits = expB | sigB;
  82         goto infArg;
  83     }
  84     if ( expB == 0x1F ) {
  85         if ( sigB ) goto propagateNaN;
  86         magBits = expA | sigA;
  87         goto infArg;
  88     }
  89     /*------------------------------------------------------------------------
  90     *------------------------------------------------------------------------*/
  91     if ( ! expA ) {
  92         if ( ! sigA ) goto zero;
  93         normExpSig = softfloat_normSubnormalF16Sig( sigA );
  94         expA = normExpSig.exp;
  95         sigA = normExpSig.sig;
  96     }
  97     if ( ! expB ) {
  98         if ( ! sigB ) goto zero;
  99         normExpSig = softfloat_normSubnormalF16Sig( sigB );
 100         expB = normExpSig.exp;
 101         sigB = normExpSig.sig;
 102     }
 103     /*------------------------------------------------------------------------
 104     *------------------------------------------------------------------------*/
 105     expZ = expA + expB - 0xF;
 106     sigA = (sigA | 0x0400)<<4;
 107     sigB = (sigB | 0x0400)<<5;
 108     sig32Z = (uint_fast32_t) sigA * sigB;
 109     sigZ = sig32Z>>16;
 110     if ( sig32Z & 0xFFFF ) sigZ |= 1;
 111     if ( sigZ < 0x4000 ) {
 112         --expZ;
 113         sigZ <<= 1;
 114     }
 115     return softfloat_roundPackToF16( signZ, expZ, sigZ );
 116     /*------------------------------------------------------------------------
 117     *------------------------------------------------------------------------*/
 118  propagateNaN:
 119     uiZ = softfloat_propagateNaNF16UI( uiA, uiB );
 120     goto uiZ;
 121     /*------------------------------------------------------------------------
 122     *------------------------------------------------------------------------*/
 123  infArg:
 124     if ( ! magBits ) {
 125         softfloat_raiseFlags( softfloat_flag_invalid );
 126         uiZ = defaultNaNF16UI;
 127     } else {
 128         uiZ = packToF16UI( signZ, 0x1F, 0 );
 129     }
 130     goto uiZ;
 131     /*------------------------------------------------------------------------
 132     *------------------------------------------------------------------------*/
 133  zero:
 134     uiZ = packToF16UI( signZ, 0, 0 );
 135  uiZ:
 136     uZ.ui = uiZ;
 137     return uZ.f;
 138
 139 }
 140