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 The Regents of the University of
8California.  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
44float32_t softfloat_subMagsF32( uint_fast32_t uiA, uint_fast32_t uiB )
45{
46    int_fast16_t expA;
47    uint_fast32_t sigA;
48    int_fast16_t expB;
49    uint_fast32_t sigB;
50    int_fast16_t expDiff;
51    uint_fast32_t uiZ;
52    int_fast32_t sigDiff;
53    bool signZ;
54    int_fast8_t shiftDist;
55    int_fast16_t expZ;
56    uint_fast32_t sigX, sigY;
57    union ui32_f32 uZ;
58
59    /*------------------------------------------------------------------------
60    *------------------------------------------------------------------------*/
61    expA = expF32UI( uiA );
62    sigA = fracF32UI( uiA );
63    expB = expF32UI( uiB );
64    sigB = fracF32UI( uiB );
65    /*------------------------------------------------------------------------
66    *------------------------------------------------------------------------*/
67    expDiff = expA - expB;
68    if ( ! expDiff ) {
69        /*--------------------------------------------------------------------
70        *--------------------------------------------------------------------*/
71        if ( expA == 0xFF ) {
72            if ( sigA | sigB ) goto propagateNaN;
73            softfloat_raiseFlags( softfloat_flag_invalid );
74            uiZ = defaultNaNF32UI;
75            goto uiZ;
76        }
77        sigDiff = sigA - sigB;
78        if ( ! sigDiff ) {
79            uiZ =
80                packToF32UI(
81                    (softfloat_roundingMode == softfloat_round_min), 0, 0 );
82            goto uiZ;
83        }
84        if ( expA ) --expA;
85        signZ = signF32UI( uiA );
86        if ( sigDiff < 0 ) {
87            signZ = ! signZ;
88            sigDiff = -sigDiff;
89        }
90        shiftDist = softfloat_countLeadingZeros32( sigDiff ) - 8;
91        expZ = expA - shiftDist;
92        if ( expZ < 0 ) {
93            shiftDist = expA;
94            expZ = 0;
95        }
96        uiZ = packToF32UI( signZ, expZ, sigDiff<<shiftDist );
97        goto uiZ;
98    } else {
99        /*--------------------------------------------------------------------
100        *--------------------------------------------------------------------*/
101        signZ = signF32UI( uiA );
102        sigA <<= 7;
103        sigB <<= 7;
104        if ( expDiff < 0 ) {
105            /*----------------------------------------------------------------
106            *----------------------------------------------------------------*/
107            signZ = ! signZ;
108            if ( expB == 0xFF ) {
109                if ( sigB ) goto propagateNaN;
110                uiZ = packToF32UI( signZ, 0xFF, 0 );
111                goto uiZ;
112            }
113            expZ = expB - 1;
114            sigX = sigB | 0x40000000;
115            sigY = sigA + (expA ? 0x40000000 : sigA);
116            expDiff = -expDiff;
117        } else {
118            /*----------------------------------------------------------------
119            *----------------------------------------------------------------*/
120            if ( expA == 0xFF ) {
121                if ( sigA ) goto propagateNaN;
122                uiZ = uiA;
123                goto uiZ;
124            }
125            expZ = expA - 1;
126            sigX = sigA | 0x40000000;
127            sigY = sigB + (expB ? 0x40000000 : sigB);
128        }
129        return
130            softfloat_normRoundPackToF32(
131                signZ, expZ, sigX - softfloat_shiftRightJam32( sigY, expDiff )
132            );
133    }
134    /*------------------------------------------------------------------------
135    *------------------------------------------------------------------------*/
136 propagateNaN:
137    uiZ = softfloat_propagateNaNF32UI( uiA, uiB );
138 uiZ:
139    uZ.ui = uiZ;
140    return uZ.f;
141
142}
143
144