1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
|
/* $OpenBSD: fpu_add.c,v 1.3 1997/08/08 08:25:47 downsj Exp $ */
/* $NetBSD: fpu_add.c,v 1.3 1996/03/14 19:41:52 christos Exp $ */
/*
* Copyright (c) 1992, 1993
* The Regents of the University of California. All rights reserved.
*
* This software was developed by the Computer Systems Engineering group
* at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
* contributed to Berkeley.
*
* All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Lawrence Berkeley Laboratory.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)fpu_add.c 8.1 (Berkeley) 6/11/93
*/
/*
* Perform an FPU add (return x + y).
*
* To subtract, negate y and call add.
*/
#include <sys/types.h>
#ifdef DIAGNOSTIC
#include <sys/systm.h>
#endif
#include <machine/reg.h>
#include <machine/instr.h>
#include <sparc/fpu/fpu_arith.h>
#include <sparc/fpu/fpu_emu.h>
#include <sparc/fpu/fpu_extern.h>
struct fpn *
fpu_add(fe)
register struct fpemu *fe;
{
register struct fpn *x = &fe->fe_f1, *y = &fe->fe_f2, *r;
register u_int r0, r1, r2, r3;
register int rd;
/*
* Put the `heavier' operand on the right (see fpu_emu.h).
* Then we will have one of the following cases, taken in the
* following order:
*
* - y = NaN. Implied: if only one is a signalling NaN, y is.
* The result is y.
* - y = Inf. Implied: x != NaN (is 0, number, or Inf: the NaN
* case was taken care of earlier).
* If x = -y, the result is NaN. Otherwise the result
* is y (an Inf of whichever sign).
* - y is 0. Implied: x = 0.
* If x and y differ in sign (one positive, one negative),
* the result is +0 except when rounding to -Inf. If same:
* +0 + +0 = +0; -0 + -0 = -0.
* - x is 0. Implied: y != 0.
* Result is y.
* - other. Implied: both x and y are numbers.
* Do addition a la Hennessey & Patterson.
*/
ORDER(x, y);
if (ISNAN(y))
return (y);
if (ISINF(y)) {
if (ISINF(x) && x->fp_sign != y->fp_sign)
return (fpu_newnan(fe));
return (y);
}
rd = ((fe->fe_fsr >> FSR_RD_SHIFT) & FSR_RD_MASK);
if (ISZERO(y)) {
if (rd != FSR_RD_RM) /* only -0 + -0 gives -0 */
y->fp_sign &= x->fp_sign;
else /* any -0 operand gives -0 */
y->fp_sign |= x->fp_sign;
return (y);
}
if (ISZERO(x))
return (y);
/*
* We really have two numbers to add, although their signs may
* differ. Make the exponents match, by shifting the smaller
* number right (e.g., 1.011 => 0.1011) and increasing its
* exponent (2^3 => 2^4). Note that we do not alter the exponents
* of x and y here.
*/
r = &fe->fe_f3;
r->fp_class = FPC_NUM;
if (x->fp_exp == y->fp_exp) {
r->fp_exp = x->fp_exp;
r->fp_sticky = 0;
} else {
if (x->fp_exp < y->fp_exp) {
/*
* Try to avoid subtract case iii (see below).
* This also guarantees that x->fp_sticky = 0.
*/
SWAP(x, y);
}
/* now x->fp_exp > y->fp_exp */
r->fp_exp = x->fp_exp;
r->fp_sticky = fpu_shr(y, x->fp_exp - y->fp_exp);
}
r->fp_sign = x->fp_sign;
if (x->fp_sign == y->fp_sign) {
FPU_DECL_CARRY
/*
* The signs match, so we simply add the numbers. The result
* may be `supernormal' (as big as 1.111...1 + 1.111...1, or
* 11.111...0). If so, a single bit shift-right will fix it
* (but remember to adjust the exponent).
*/
/* r->fp_mant = x->fp_mant + y->fp_mant */
FPU_ADDS(r->fp_mant[3], x->fp_mant[3], y->fp_mant[3]);
FPU_ADDCS(r->fp_mant[2], x->fp_mant[2], y->fp_mant[2]);
FPU_ADDCS(r->fp_mant[1], x->fp_mant[1], y->fp_mant[1]);
FPU_ADDC(r0, x->fp_mant[0], y->fp_mant[0]);
if ((r->fp_mant[0] = r0) >= FP_2) {
(void) fpu_shr(r, 1);
r->fp_exp++;
}
} else {
FPU_DECL_CARRY
/*
* The signs differ, so things are rather more difficult.
* H&P would have us negate the negative operand and add;
* this is the same as subtracting the negative operand.
* This is quite a headache. Instead, we will subtract
* y from x, regardless of whether y itself is the negative
* operand. When this is done one of three conditions will
* hold, depending on the magnitudes of x and y:
* case i) |x| > |y|. The result is just x - y,
* with x's sign, but it may need to be normalized.
* case ii) |x| = |y|. The result is 0 (maybe -0)
* so must be fixed up.
* case iii) |x| < |y|. We goofed; the result should
* be (y - x), with the same sign as y.
* We could compare |x| and |y| here and avoid case iii,
* but that would take just as much work as the subtract.
* We can tell case iii has occurred by an overflow.
*
* N.B.: since x->fp_exp >= y->fp_exp, x->fp_sticky = 0.
*/
/* r->fp_mant = x->fp_mant - y->fp_mant */
FPU_SET_CARRY(y->fp_sticky);
FPU_SUBCS(r3, x->fp_mant[3], y->fp_mant[3]);
FPU_SUBCS(r2, x->fp_mant[2], y->fp_mant[2]);
FPU_SUBCS(r1, x->fp_mant[1], y->fp_mant[1]);
FPU_SUBC(r0, x->fp_mant[0], y->fp_mant[0]);
if (r0 < FP_2) {
/* cases i and ii */
if ((r0 | r1 | r2 | r3) == 0) {
/* case ii */
r->fp_class = FPC_ZERO;
r->fp_sign = rd == FSR_RD_RM;
return (r);
}
} else {
/*
* Oops, case iii. This can only occur when the
* exponents were equal, in which case neither
* x nor y have sticky bits set. Flip the sign
* (to y's sign) and negate the result to get y - x.
*/
#ifdef DIAGNOSTIC
if (x->fp_exp != y->fp_exp || r->fp_sticky)
panic("fpu_add");
#endif
r->fp_sign = y->fp_sign;
FPU_SUBS(r3, 0, r3);
FPU_SUBCS(r2, 0, r2);
FPU_SUBCS(r1, 0, r1);
FPU_SUBC(r0, 0, r0);
}
r->fp_mant[3] = r3;
r->fp_mant[2] = r2;
r->fp_mant[1] = r1;
r->fp_mant[0] = r0;
if (r0 < FP_1)
fpu_norm(r);
}
return (r);
}
|
