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
|
/* $Id: mul.S,v 1.4 1996/09/30 02:22:32 davem Exp $
* mul.S: This routine was taken from glibc-1.09 and is covered
* by the GNU Library General Public License Version 2.
*/
/*
* Signed multiply, from Appendix E of the Sparc Version 8
* Architecture Manual.
*/
/*
* Returns %o0 * %o1 in %o1%o0 (i.e., %o1 holds the upper 32 bits of
* the 64-bit product).
*
* This code optimizes short (less than 13-bit) multiplies.
*/
.globl .mul
.globl _Mul
.mul:
_Mul: /* needed for export */
mov %o0, %y ! multiplier -> Y
andncc %o0, 0xfff, %g0 ! test bits 12..31
be Lmul_shortway ! if zero, can do it the short way
andcc %g0, %g0, %o4 ! zero the partial product and clear N and V
/*
* Long multiply. 32 steps, followed by a final shift step.
*/
mulscc %o4, %o1, %o4 ! 1
mulscc %o4, %o1, %o4 ! 2
mulscc %o4, %o1, %o4 ! 3
mulscc %o4, %o1, %o4 ! 4
mulscc %o4, %o1, %o4 ! 5
mulscc %o4, %o1, %o4 ! 6
mulscc %o4, %o1, %o4 ! 7
mulscc %o4, %o1, %o4 ! 8
mulscc %o4, %o1, %o4 ! 9
mulscc %o4, %o1, %o4 ! 10
mulscc %o4, %o1, %o4 ! 11
mulscc %o4, %o1, %o4 ! 12
mulscc %o4, %o1, %o4 ! 13
mulscc %o4, %o1, %o4 ! 14
mulscc %o4, %o1, %o4 ! 15
mulscc %o4, %o1, %o4 ! 16
mulscc %o4, %o1, %o4 ! 17
mulscc %o4, %o1, %o4 ! 18
mulscc %o4, %o1, %o4 ! 19
mulscc %o4, %o1, %o4 ! 20
mulscc %o4, %o1, %o4 ! 21
mulscc %o4, %o1, %o4 ! 22
mulscc %o4, %o1, %o4 ! 23
mulscc %o4, %o1, %o4 ! 24
mulscc %o4, %o1, %o4 ! 25
mulscc %o4, %o1, %o4 ! 26
mulscc %o4, %o1, %o4 ! 27
mulscc %o4, %o1, %o4 ! 28
mulscc %o4, %o1, %o4 ! 29
mulscc %o4, %o1, %o4 ! 30
mulscc %o4, %o1, %o4 ! 31
mulscc %o4, %o1, %o4 ! 32
mulscc %o4, %g0, %o4 ! final shift
! If %o0 was negative, the result is
! (%o0 * %o1) + (%o1 << 32))
! We fix that here.
#if 0
tst %o0
bge 1f
rd %y, %o0
! %o0 was indeed negative; fix upper 32 bits of result by subtracting
! %o1 (i.e., return %o4 - %o1 in %o1).
retl
sub %o4, %o1, %o1
1:
retl
mov %o4, %o1
#else
/* Faster code adapted from tege@sics.se's code for umul.S. */
sra %o0, 31, %o2 ! make mask from sign bit
and %o1, %o2, %o2 ! %o2 = 0 or %o1, depending on sign of %o0
rd %y, %o0 ! get lower half of product
retl
sub %o4, %o2, %o1 ! subtract compensation
! and put upper half in place
#endif
Lmul_shortway:
/*
* Short multiply. 12 steps, followed by a final shift step.
* The resulting bits are off by 12 and (32-12) = 20 bit positions,
* but there is no problem with %o0 being negative (unlike above).
*/
mulscc %o4, %o1, %o4 ! 1
mulscc %o4, %o1, %o4 ! 2
mulscc %o4, %o1, %o4 ! 3
mulscc %o4, %o1, %o4 ! 4
mulscc %o4, %o1, %o4 ! 5
mulscc %o4, %o1, %o4 ! 6
mulscc %o4, %o1, %o4 ! 7
mulscc %o4, %o1, %o4 ! 8
mulscc %o4, %o1, %o4 ! 9
mulscc %o4, %o1, %o4 ! 10
mulscc %o4, %o1, %o4 ! 11
mulscc %o4, %o1, %o4 ! 12
mulscc %o4, %g0, %o4 ! final shift
/*
* %o4 has 20 of the bits that should be in the low part of the
* result; %y has the bottom 12 (as %y's top 12). That is:
*
* %o4 %y
* +----------------+----------------+
* | -12- | -20- | -12- | -20- |
* +------(---------+------)---------+
* --hi-- ----low-part----
*
* The upper 12 bits of %o4 should be sign-extended to form the
* high part of the product (i.e., highpart = %o4 >> 20).
*/
rd %y, %o5
sll %o4, 12, %o0 ! shift middle bits left 12
srl %o5, 20, %o5 ! shift low bits right 20, zero fill at left
or %o5, %o0, %o0 ! construct low part of result
retl
sra %o4, 20, %o1 ! ... and extract high part of result
.globl .mul_patch
.mul_patch:
smul %o0, %o1, %o0
retl
rd %y, %o1
nop
|
