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
44float64_t
45 softfloat_subMagsF64( uint_fast64_t uiA, uint_fast64_t uiB, bool signZ )
46{
47    int_fast16_t expA;
48    uint_fast64_t sigA;
49    int_fast16_t expB;
50    uint_fast64_t sigB;
51    int_fast16_t expDiff;
52    uint_fast64_t uiZ;
53    int_fast64_t sigDiff;
54    int_fast8_t shiftDist;
55    int_fast16_t expZ;
56    uint_fast64_t sigZ;
57    union ui64_f64 uZ;
58
59    /*------------------------------------------------------------------------
60    *------------------------------------------------------------------------*/
61    expA = expF64UI( uiA );
62    sigA = fracF64UI( uiA );
63    expB = expF64UI( uiB );
64    sigB = fracF64UI( uiB );
65    /*------------------------------------------------------------------------
66    *------------------------------------------------------------------------*/
67    expDiff = expA - expB;
68    if ( ! expDiff ) {
69        /*--------------------------------------------------------------------
70        *--------------------------------------------------------------------*/
71        if ( expA == 0x7FF ) {
72            if ( sigA | sigB ) goto propagateNaN;
73            softfloat_raiseFlags( softfloat_flag_invalid );
74            uiZ = defaultNaNF64UI;
75            goto uiZ;
76        }
77        sigDiff = sigA - sigB;
78        if ( ! sigDiff ) {
79            uiZ =
80                packToF64UI(
81                    (softfloat_roundingMode == softfloat_round_min), 0, 0 );
82            goto uiZ;
83        }
84        if ( expA ) --expA;
85        if ( sigDiff < 0 ) {
86            signZ = ! signZ;
87            sigDiff = -sigDiff;
88        }
89        shiftDist = softfloat_countLeadingZeros64( sigDiff ) - 11;
90        expZ = expA - shiftDist;
91        if ( expZ < 0 ) {
92            shiftDist = expA;
93            expZ = 0;
94        }
95        uiZ = packToF64UI( signZ, expZ, sigDiff<<shiftDist );
96        goto uiZ;
97    } else {
98        /*--------------------------------------------------------------------
99        *--------------------------------------------------------------------*/
100        sigA <<= 10;
101        sigB <<= 10;
102        if ( expDiff < 0 ) {
103            /*----------------------------------------------------------------
104            *----------------------------------------------------------------*/
105            signZ = ! signZ;
106            if ( expB == 0x7FF ) {
107                if ( sigB ) goto propagateNaN;
108                uiZ = packToF64UI( signZ, 0x7FF, 0 );
109                goto uiZ;
110            }
111            sigA += expA ? UINT64_C( 0x4000000000000000 ) : sigA;
112            sigA = softfloat_shiftRightJam64( sigA, -expDiff );
113            sigB |= UINT64_C( 0x4000000000000000 );
114            expZ = expB;
115            sigZ = sigB - sigA;
116        } else {
117            /*----------------------------------------------------------------
118            *----------------------------------------------------------------*/
119            if ( expA == 0x7FF ) {
120                if ( sigA ) goto propagateNaN;
121                uiZ = uiA;
122                goto uiZ;
123            }
124            sigB += expB ? UINT64_C( 0x4000000000000000 ) : sigB;
125            sigB = softfloat_shiftRightJam64( sigB, expDiff );
126            sigA |= UINT64_C( 0x4000000000000000 );
127            expZ = expA;
128            sigZ = sigA - sigB;
129        }
130        return softfloat_normRoundPackToF64( signZ, expZ - 1, sigZ );
131    }
132    /*------------------------------------------------------------------------
133    *------------------------------------------------------------------------*/
134 propagateNaN:
135    uiZ = softfloat_propagateNaNF64UI( uiA, uiB );
136 uiZ:
137    uZ.ui = uiZ;
138    return uZ.f;
139
140}
141
142