OpenCores
URL https://opencores.org/ocsvn/or1k_soc_on_altera_embedded_dev_kit/or1k_soc_on_altera_embedded_dev_kit/trunk

Subversion Repositories or1k_soc_on_altera_embedded_dev_kit

[/] [or1k_soc_on_altera_embedded_dev_kit/] [trunk/] [linux-2.6/] [linux-2.6.24/] [arch/] [sparc/] [lib/] [mul.S] - Blame information for rev 3

Details | Compare with Previous | View Log

Line No. Rev Author Line
1 3 xianfeng 
/* $Id: mul.S,v 1.4 1996/09/30 02:22:32 davem Exp $
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
19 
        .globl _Mul
20 
.mul:
21 
_Mul:   /* needed for export */
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

powered by: WebSVN 2.1.0

© copyright 1999-2024 OpenCores.org, equivalent to Oliscience, all rights reserved. OpenCores®, registered trademark.