Commit | Line | Data |
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88278ca2 | 1 | /* |
1da177e4 LT |
2 | * mul.S: This routine was taken from glibc-1.09 and is covered |
3 | * by the GNU Library General Public License Version 2. | |
4 | */ | |
5 | ||
6 | /* | |
7 | * Signed multiply, from Appendix E of the Sparc Version 8 | |
8 | * Architecture Manual. | |
9 | */ | |
10 | ||
11 | /* | |
12 | * Returns %o0 * %o1 in %o1%o0 (i.e., %o1 holds the upper 32 bits of | |
13 | * the 64-bit product). | |
14 | * | |
15 | * This code optimizes short (less than 13-bit) multiplies. | |
16 | */ | |
17 | ||
18 | .globl .mul | |
7caaeabb | 19 | .globl _Mul |
1da177e4 | 20 | .mul: |
7caaeabb | 21 | _Mul: /* needed for export */ |
1da177e4 LT |
22 | mov %o0, %y ! multiplier -> Y |
23 | andncc %o0, 0xfff, %g0 ! test bits 12..31 | |
24 | be Lmul_shortway ! if zero, can do it the short way | |
25 | andcc %g0, %g0, %o4 ! zero the partial product and clear N and V | |
26 | ||
27 | /* | |
28 | * Long multiply. 32 steps, followed by a final shift step. | |
29 | */ | |
30 | mulscc %o4, %o1, %o4 ! 1 | |
31 | mulscc %o4, %o1, %o4 ! 2 | |
32 | mulscc %o4, %o1, %o4 ! 3 | |
33 | mulscc %o4, %o1, %o4 ! 4 | |
34 | mulscc %o4, %o1, %o4 ! 5 | |
35 | mulscc %o4, %o1, %o4 ! 6 | |
36 | mulscc %o4, %o1, %o4 ! 7 | |
37 | mulscc %o4, %o1, %o4 ! 8 | |
38 | mulscc %o4, %o1, %o4 ! 9 | |
39 | mulscc %o4, %o1, %o4 ! 10 | |
40 | mulscc %o4, %o1, %o4 ! 11 | |
41 | mulscc %o4, %o1, %o4 ! 12 | |
42 | mulscc %o4, %o1, %o4 ! 13 | |
43 | mulscc %o4, %o1, %o4 ! 14 | |
44 | mulscc %o4, %o1, %o4 ! 15 | |
45 | mulscc %o4, %o1, %o4 ! 16 | |
46 | mulscc %o4, %o1, %o4 ! 17 | |
47 | mulscc %o4, %o1, %o4 ! 18 | |
48 | mulscc %o4, %o1, %o4 ! 19 | |
49 | mulscc %o4, %o1, %o4 ! 20 | |
50 | mulscc %o4, %o1, %o4 ! 21 | |
51 | mulscc %o4, %o1, %o4 ! 22 | |
52 | mulscc %o4, %o1, %o4 ! 23 | |
53 | mulscc %o4, %o1, %o4 ! 24 | |
54 | mulscc %o4, %o1, %o4 ! 25 | |
55 | mulscc %o4, %o1, %o4 ! 26 | |
56 | mulscc %o4, %o1, %o4 ! 27 | |
57 | mulscc %o4, %o1, %o4 ! 28 | |
58 | mulscc %o4, %o1, %o4 ! 29 | |
59 | mulscc %o4, %o1, %o4 ! 30 | |
60 | mulscc %o4, %o1, %o4 ! 31 | |
61 | mulscc %o4, %o1, %o4 ! 32 | |
62 | mulscc %o4, %g0, %o4 ! final shift | |
63 | ||
64 | ! If %o0 was negative, the result is | |
65 | ! (%o0 * %o1) + (%o1 << 32)) | |
66 | ! We fix that here. | |
67 | ||
68 | #if 0 | |
69 | tst %o0 | |
70 | bge 1f | |
71 | rd %y, %o0 | |
72 | ||
73 | ! %o0 was indeed negative; fix upper 32 bits of result by subtracting | |
74 | ! %o1 (i.e., return %o4 - %o1 in %o1). | |
75 | retl | |
76 | sub %o4, %o1, %o1 | |
77 | ||
78 | 1: | |
79 | retl | |
80 | mov %o4, %o1 | |
81 | #else | |
82 | /* Faster code adapted from tege@sics.se's code for umul.S. */ | |
83 | sra %o0, 31, %o2 ! make mask from sign bit | |
84 | and %o1, %o2, %o2 ! %o2 = 0 or %o1, depending on sign of %o0 | |
85 | rd %y, %o0 ! get lower half of product | |
86 | retl | |
87 | sub %o4, %o2, %o1 ! subtract compensation | |
88 | ! and put upper half in place | |
89 | #endif | |
90 | ||
91 | Lmul_shortway: | |
92 | /* | |
93 | * Short multiply. 12 steps, followed by a final shift step. | |
94 | * The resulting bits are off by 12 and (32-12) = 20 bit positions, | |
95 | * but there is no problem with %o0 being negative (unlike above). | |
96 | */ | |
97 | mulscc %o4, %o1, %o4 ! 1 | |
98 | mulscc %o4, %o1, %o4 ! 2 | |
99 | mulscc %o4, %o1, %o4 ! 3 | |
100 | mulscc %o4, %o1, %o4 ! 4 | |
101 | mulscc %o4, %o1, %o4 ! 5 | |
102 | mulscc %o4, %o1, %o4 ! 6 | |
103 | mulscc %o4, %o1, %o4 ! 7 | |
104 | mulscc %o4, %o1, %o4 ! 8 | |
105 | mulscc %o4, %o1, %o4 ! 9 | |
106 | mulscc %o4, %o1, %o4 ! 10 | |
107 | mulscc %o4, %o1, %o4 ! 11 | |
108 | mulscc %o4, %o1, %o4 ! 12 | |
109 | mulscc %o4, %g0, %o4 ! final shift | |
110 | ||
111 | /* | |
112 | * %o4 has 20 of the bits that should be in the low part of the | |
113 | * result; %y has the bottom 12 (as %y's top 12). That is: | |
114 | * | |
115 | * %o4 %y | |
116 | * +----------------+----------------+ | |
117 | * | -12- | -20- | -12- | -20- | | |
118 | * +------(---------+------)---------+ | |
119 | * --hi-- ----low-part---- | |
120 | * | |
121 | * The upper 12 bits of %o4 should be sign-extended to form the | |
122 | * high part of the product (i.e., highpart = %o4 >> 20). | |
123 | */ | |
124 | ||
125 | rd %y, %o5 | |
126 | sll %o4, 12, %o0 ! shift middle bits left 12 | |
127 | srl %o5, 20, %o5 ! shift low bits right 20, zero fill at left | |
128 | or %o5, %o0, %o0 ! construct low part of result | |
129 | retl | |
130 | sra %o4, 20, %o1 ! ... and extract high part of result | |
131 | ||
132 | .globl .mul_patch | |
133 | .mul_patch: | |
134 | smul %o0, %o1, %o0 | |
135 | retl | |
136 | rd %y, %o1 | |
137 | nop |