1
2/*============================================================================
3
4This C source file is part of the SoftFloat IEEE Floating-Point Arithmetic
5Package, Release 3e, by John R. Hauser.
6
7Copyright 2011, 2012, 2013, 2014, 2015, 2016, 2017 The Regents of the
8University of California.  All rights reserved.
9
10Redistribution and use in source and binary forms, with or without
11modification, 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
24THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS "AS IS", AND ANY
25EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
26WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ARE
27DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
28DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
29(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
30LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
31ON 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
33SOFTWARE, 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
44float16_t softfloat_addMagsF16( uint_fast16_t uiA, uint_fast16_t uiB )
45{
46    int_fast8_t expA;
47    uint_fast16_t sigA;
48    int_fast8_t expB;
49    uint_fast16_t sigB;
50    int_fast8_t expDiff;
51    uint_fast16_t uiZ;
52    bool signZ;
53    int_fast8_t expZ;
54    uint_fast16_t sigZ;
55    uint_fast16_t sigX, sigY;
56    int_fast8_t shiftDist;
57    uint_fast32_t sig32Z;
58    int_fast8_t roundingMode;
59    union ui16_f16 uZ;
60
61    /*------------------------------------------------------------------------
62    *------------------------------------------------------------------------*/
63    expA = expF16UI( uiA );
64    sigA = fracF16UI( uiA );
65    expB = expF16UI( uiB );
66    sigB = fracF16UI( uiB );
67    /*------------------------------------------------------------------------
68    *------------------------------------------------------------------------*/
69    expDiff = expA - expB;
70    if ( ! expDiff ) {
71        /*--------------------------------------------------------------------
72        *--------------------------------------------------------------------*/
73        if ( ! expA ) {
74            uiZ = uiA + sigB;
75            goto uiZ;
76        }
77        if ( expA == 0x1F ) {
78            if ( sigA | sigB ) goto propagateNaN;
79            uiZ = uiA;
80            goto uiZ;
81        }
82        signZ = signF16UI( uiA );
83        expZ = expA;
84        sigZ = 0x0800 + sigA + sigB;
85        if ( ! (sigZ & 1) && (expZ < 0x1E) ) {
86            sigZ >>= 1;
87            goto pack;
88        }
89        sigZ <<= 3;
90    } else {
91        /*--------------------------------------------------------------------
92        *--------------------------------------------------------------------*/
93        signZ = signF16UI( uiA );
94        if ( expDiff < 0 ) {
95            /*----------------------------------------------------------------
96            *----------------------------------------------------------------*/
97            if ( expB == 0x1F ) {
98                if ( sigB ) goto propagateNaN;
99                uiZ = packToF16UI( signZ, 0x1F, 0 );
100                goto uiZ;
101            }
102            if ( expDiff <= -13 ) {
103                uiZ = packToF16UI( signZ, expB, sigB );
104                if ( expA | sigA ) goto addEpsilon;
105                goto uiZ;
106            }
107            expZ = expB;
108            sigX = sigB | 0x0400;
109            sigY = sigA + (expA ? 0x0400 : sigA);
110            shiftDist = 19 + expDiff;
111        } else {
112            /*----------------------------------------------------------------
113            *----------------------------------------------------------------*/
114            uiZ = uiA;
115            if ( expA == 0x1F ) {
116                if ( sigA ) goto propagateNaN;
117                goto uiZ;
118            }
119            if ( 13 <= expDiff ) {
120                if ( expB | sigB ) goto addEpsilon;
121                goto uiZ;
122            }
123            expZ = expA;
124            sigX = sigA | 0x0400;
125            sigY = sigB + (expB ? 0x0400 : sigB);
126            shiftDist = 19 - expDiff;
127        }
128        sig32Z =
129            ((uint_fast32_t) sigX<<19) + ((uint_fast32_t) sigY<<shiftDist);
130        if ( sig32Z < 0x40000000 ) {
131            --expZ;
132            sig32Z <<= 1;
133        }
134        sigZ = sig32Z>>16;
135        if ( sig32Z & 0xFFFF ) {
136            sigZ |= 1;
137        } else {
138            if ( ! (sigZ & 0xF) && (expZ < 0x1E) ) {
139                sigZ >>= 4;
140                goto pack;
141            }
142        }
143    }
144    return softfloat_roundPackToF16( signZ, expZ, sigZ );
145    /*------------------------------------------------------------------------
146    *------------------------------------------------------------------------*/
147 propagateNaN:
148    uiZ = softfloat_propagateNaNF16UI( uiA, uiB );
149    goto uiZ;
150    /*------------------------------------------------------------------------
151    *------------------------------------------------------------------------*/
152 addEpsilon:
153    roundingMode = softfloat_roundingMode;
154    if ( roundingMode != softfloat_round_near_even ) {
155        if (
156            roundingMode
157                == (signF16UI( uiZ ) ? softfloat_round_min
158                        : softfloat_round_max)
159        ) {
160            ++uiZ;
161            if ( (uint16_t) (uiZ<<1) == 0xF800 ) {
162                softfloat_raiseFlags(
163                    softfloat_flag_overflow | softfloat_flag_inexact );
164            }
165        }
166#ifdef SOFTFLOAT_ROUND_ODD
167        else if ( roundingMode == softfloat_round_odd ) {
168            uiZ |= 1;
169        }
170#endif
171    }
172    softfloat_raiseFlags( softfloat_flag_inexact );
173    goto uiZ;
174    /*------------------------------------------------------------------------
175    *------------------------------------------------------------------------*/
176 pack:
177    uiZ = packToF16UI( signZ, expZ, sigZ );
178 uiZ:
179    uZ.ui = uiZ;
180    return uZ.f;
181
182}
183
184