Subversion Repositories HelenOS-historic

Rev

Rev 1653 | Go to most recent revision | Details | Compare with Previous | Last modification | View Log | RSS feed

Rev Author Line No. Line
829 cejka 1
/*
2
 * Copyright (C) 2005 Josef Cejka
3
 * All rights reserved.
4
 *
5
 * Redistribution and use in source and binary forms, with or without
6
 * modification, are permitted provided that the following conditions
7
 * are met:
8
 *
9
 * - Redistributions of source code must retain the above copyright
10
 *   notice, this list of conditions and the following disclaimer.
11
 * - Redistributions in binary form must reproduce the above copyright
12
 *   notice, this list of conditions and the following disclaimer in the
13
 *   documentation and/or other materials provided with the distribution.
14
 * - The name of the author may not be used to endorse or promote products
15
 *   derived from this software without specific prior written permission.
16
 *
17
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27
 */
28
 
1657 cejka 29
 /** @addtogroup softfloat 
30
 * @{
31
 */
32
/** @file
33
 */
34
 
829 cejka 35
#include<sftypes.h>
36
#include<common.h>
37
 
874 cejka 38
/* Table for fast leading zeroes counting */
39
char zeroTable[256] = {
40
    8, 7, 7, 6, 6, 6, 6, 4, 4, 4, 4, 4, 4, 4, 4, \
41
    3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, \
42
    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, \
43
    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, \
44
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
45
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
46
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
47
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
48
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \
49
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \
50
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \
51
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \
52
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \
53
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \
54
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \
55
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
56
};
57
 
58
 
59
 
829 cejka 60
/** Take fraction shifted by 10 bits to left, round it, normalize it and detect exceptions
1653 cejka 61
 * @param cexp exponent with bias
829 cejka 62
 * @param cfrac fraction shifted 10 places left with added hidden bit
1653 cejka 63
 * @param sign
829 cejka 64
 * @return valied float64
65
 */
1031 cejka 66
float64 finishFloat64(int32_t cexp, uint64_t cfrac, char sign)
829 cejka 67
{
68
    float64 result;
69
 
70
    result.parts.sign = sign;
71
 
72
    /* find first nonzero digit and shift result and detect possibly underflow */
73
    while ((cexp > 0) && (cfrac) && (!(cfrac & (FLOAT64_HIDDEN_BIT_MASK << (64 - FLOAT64_FRACTION_SIZE - 1 ) )))) {
74
        cexp--;
75
        cfrac <<= 1;
76
            /* TODO: fix underflow */
77
    };
78
 
834 cejka 79
    if ((cexp < 0) || ( cexp == 0 && (!(cfrac & (FLOAT64_HIDDEN_BIT_MASK << (64 - FLOAT64_FRACTION_SIZE - 1)))))) {
80
        /* FIXME: underflow */
81
        result.parts.exp = 0;
835 cejka 82
        if ((cexp + FLOAT64_FRACTION_SIZE + 1) < 0) { /* +1 is place for rounding */
834 cejka 83
            result.parts.fraction = 0;
84
            return result;
85
        }
835 cejka 86
 
834 cejka 87
        while (cexp < 0) {
88
            cexp++;
89
            cfrac >>= 1;
90
        }
835 cejka 91
 
92
        cfrac += (0x1 << (64 - FLOAT64_FRACTION_SIZE - 3));
93
 
874 cejka 94
        if (!(cfrac & (FLOAT64_HIDDEN_BIT_MASK << (64 - FLOAT64_FRACTION_SIZE - 1)))) {
834 cejka 95
 
835 cejka 96
            result.parts.fraction = ((cfrac >>(64 - FLOAT64_FRACTION_SIZE - 2) ) & (~FLOAT64_HIDDEN_BIT_MASK));
97
            return result;
98
        }  
99
    } else {
100
        cfrac += (0x1 << (64 - FLOAT64_FRACTION_SIZE - 3));
834 cejka 101
    }
102
 
103
    ++cexp;
104
 
829 cejka 105
    if (cfrac & (FLOAT64_HIDDEN_BIT_MASK << (64 - FLOAT64_FRACTION_SIZE - 1 ))) {
106
        ++cexp;
107
        cfrac >>= 1;
834 cejka 108
    }  
829 cejka 109
 
110
    /* check overflow */
111
    if (cexp >= FLOAT64_MAX_EXPONENT ) {
112
        /* FIXME: overflow, return infinity */
113
        result.parts.exp = FLOAT64_MAX_EXPONENT;
114
        result.parts.fraction = 0;
115
        return result;
116
    }
117
 
1031 cejka 118
    result.parts.exp = (uint32_t)cexp;
829 cejka 119
 
120
    result.parts.fraction = ((cfrac >>(64 - FLOAT64_FRACTION_SIZE - 2 ) ) & (~FLOAT64_HIDDEN_BIT_MASK));
121
 
122
    return result; 
123
}
834 cejka 124
 
874 cejka 125
/** Counts leading zeroes in 64bit unsigned integer
126
 * @param i
127
 */
1031 cejka 128
int countZeroes64(uint64_t i)
874 cejka 129
{
130
    int j;
131
    for (j =0; j < 64; j += 8) {
132
        if ( i & (0xFFll << (56 - j))) {
133
            return (j + countZeroes8(i >> (56 - j)));
134
        }
135
    }
136
 
137
    return 64;
138
}
139
 
140
/** Counts leading zeroes in 32bit unsigned integer
141
 * @param i
142
 */
1031 cejka 143
int countZeroes32(uint32_t i)
874 cejka 144
{
145
    int j;
146
    for (j =0; j < 32; j += 8) {
147
        if ( i & (0xFF << (24 - j))) {
148
            return (j + countZeroes8(i >> (24 - j)));
149
        }
150
    }
151
 
152
    return 32;
153
}
154
 
155
/** Counts leading zeroes in byte
156
 * @param i
157
 */
1031 cejka 158
int countZeroes8(uint8_t i)
874 cejka 159
{
160
    return zeroTable[i];
161
}
162
 
163
/** Round and normalize number expressed by exponent and fraction with first bit (equal to hidden bit) at 30. bit
164
 * @param exp exponent
165
 * @param fraction part with hidden bit shifted to 30. bit
166
 */
1031 cejka 167
void roundFloat32(int32_t *exp, uint32_t *fraction)
874 cejka 168
{
169
    /* rounding - if first bit after fraction is set then round up */
170
    (*fraction) += (0x1 << 6);
171
 
172
    if ((*fraction) & (FLOAT32_HIDDEN_BIT_MASK << 8)) {
173
        /* rounding overflow */
174
        ++(*exp);
175
        (*fraction) >>= 1;
176
    };
177
 
178
    if (((*exp) >= FLOAT32_MAX_EXPONENT ) || ((*exp) < 0)) {
179
        /* overflow - set infinity as result */
180
        (*exp) = FLOAT32_MAX_EXPONENT;
181
        (*fraction) = 0;
182
        return;
183
    }
184
 
185
    return;
186
}
187
 
188
/** Round and normalize number expressed by exponent and fraction with first bit (equal to hidden bit) at 62. bit
189
 * @param exp exponent
190
 * @param fraction part with hidden bit shifted to 62. bit
191
 */
1031 cejka 192
void roundFloat64(int32_t *exp, uint64_t *fraction)
874 cejka 193
{
194
    /* rounding - if first bit after fraction is set then round up */
195
    (*fraction) += (0x1 << 9);
196
 
197
    if ((*fraction) & (FLOAT64_HIDDEN_BIT_MASK << 11)) {
198
        /* rounding overflow */
199
        ++(*exp);
200
        (*fraction) >>= 1;
201
    };
202
 
203
    if (((*exp) >= FLOAT64_MAX_EXPONENT ) || ((*exp) < 0)) {
204
        /* overflow - set infinity as result */
205
        (*exp) = FLOAT64_MAX_EXPONENT;
206
        (*fraction) = 0;
207
        return;
208
    }
209
 
210
    return;
211
}
212
 
1657 cejka 213
 
214
 /** @}
215
 */
216