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1da177e4 LT |
1 | | |
2 | | sgetem.sa 3.1 12/10/90 | |
3 | | | |
4 | | The entry point sGETEXP returns the exponent portion | |
5 | | of the input argument. The exponent bias is removed | |
6 | | and the exponent value is returned as an extended | |
7 | | precision number in fp0. sGETEXPD handles denormalized | |
8 | | numbers. | |
9 | | | |
10 | | The entry point sGETMAN extracts the mantissa of the | |
11 | | input argument. The mantissa is converted to an | |
12 | | extended precision number and returned in fp0. The | |
13 | | range of the result is [1.0 - 2.0). | |
14 | | | |
15 | | | |
16 | | Input: Double-extended number X in the ETEMP space in | |
17 | | the floating-point save stack. | |
18 | | | |
19 | | Output: The functions return exp(X) or man(X) in fp0. | |
20 | | | |
21 | | Modified: fp0. | |
22 | | | |
23 | | | |
24 | | Copyright (C) Motorola, Inc. 1990 | |
25 | | All Rights Reserved | |
26 | | | |
27 | | THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA | |
28 | | The copyright notice above does not evidence any | |
29 | | actual or intended publication of such source code. | |
30 | ||
31 | |SGETEM idnt 2,1 | Motorola 040 Floating Point Software Package | |
32 | ||
33 | |section 8 | |
34 | ||
35 | #include "fpsp.h" | |
36 | ||
37 | |xref nrm_set | |
38 | ||
39 | | | |
40 | | This entry point is used by the unimplemented instruction exception | |
41 | | handler. It points a0 to the input operand. | |
42 | | | |
43 | | | |
44 | | | |
45 | | SGETEXP | |
46 | | | |
47 | ||
48 | .global sgetexp | |
49 | sgetexp: | |
50 | movew LOCAL_EX(%a0),%d0 |get the exponent | |
51 | bclrl #15,%d0 |clear the sign bit | |
52 | subw #0x3fff,%d0 |subtract off the bias | |
53 | fmovew %d0,%fp0 |move the exp to fp0 | |
54 | rts | |
55 | ||
56 | .global sgetexpd | |
57 | sgetexpd: | |
58 | bclrb #sign_bit,LOCAL_EX(%a0) | |
59 | bsr nrm_set |normalize (exp will go negative) | |
60 | movew LOCAL_EX(%a0),%d0 |load resulting exponent into d0 | |
61 | subw #0x3fff,%d0 |subtract off the bias | |
62 | fmovew %d0,%fp0 |move the exp to fp0 | |
63 | rts | |
64 | | | |
65 | | | |
66 | | This entry point is used by the unimplemented instruction exception | |
67 | | handler. It points a0 to the input operand. | |
68 | | | |
69 | | | |
70 | | | |
71 | | SGETMAN | |
72 | | | |
73 | | | |
74 | | For normalized numbers, leave the mantissa alone, simply load | |
75 | | with an exponent of +/- $3fff. | |
76 | | | |
77 | .global sgetman | |
78 | sgetman: | |
79 | movel USER_FPCR(%a6),%d0 | |
80 | andil #0xffffff00,%d0 |clear rounding precision and mode | |
81 | fmovel %d0,%fpcr |this fpcr setting is used by the 882 | |
82 | movew LOCAL_EX(%a0),%d0 |get the exp (really just want sign bit) | |
83 | orw #0x7fff,%d0 |clear old exp | |
84 | bclrl #14,%d0 |make it the new exp +-3fff | |
85 | movew %d0,LOCAL_EX(%a0) |move the sign & exp back to fsave stack | |
86 | fmovex (%a0),%fp0 |put new value back in fp0 | |
87 | rts | |
88 | ||
89 | | | |
90 | | For denormalized numbers, shift the mantissa until the j-bit = 1, | |
91 | | then load the exponent with +/1 $3fff. | |
92 | | | |
93 | .global sgetmand | |
94 | sgetmand: | |
95 | movel LOCAL_HI(%a0),%d0 |load ms mant in d0 | |
96 | movel LOCAL_LO(%a0),%d1 |load ls mant in d1 | |
97 | bsr shft |shift mantissa bits till msbit is set | |
98 | movel %d0,LOCAL_HI(%a0) |put ms mant back on stack | |
99 | movel %d1,LOCAL_LO(%a0) |put ls mant back on stack | |
100 | bras sgetman | |
101 | ||
102 | | | |
103 | | SHFT | |
104 | | | |
105 | | Shifts the mantissa bits until msbit is set. | |
106 | | input: | |
107 | | ms mantissa part in d0 | |
108 | | ls mantissa part in d1 | |
109 | | output: | |
110 | | shifted bits in d0 and d1 | |
111 | shft: | |
112 | tstl %d0 |if any bits set in ms mant | |
113 | bnes upper |then branch | |
114 | | ;else no bits set in ms mant | |
115 | tstl %d1 |test if any bits set in ls mant | |
116 | bnes cont |if set then continue | |
117 | bras shft_end |else return | |
118 | cont: | |
119 | movel %d3,-(%a7) |save d3 | |
120 | exg %d0,%d1 |shift ls mant to ms mant | |
121 | bfffo %d0{#0:#32},%d3 |find first 1 in ls mant to d0 | |
122 | lsll %d3,%d0 |shift first 1 to integer bit in ms mant | |
123 | movel (%a7)+,%d3 |restore d3 | |
124 | bras shft_end | |
125 | upper: | |
126 | ||
127 | moveml %d3/%d5/%d6,-(%a7) |save registers | |
128 | bfffo %d0{#0:#32},%d3 |find first 1 in ls mant to d0 | |
129 | lsll %d3,%d0 |shift ms mant until j-bit is set | |
130 | movel %d1,%d6 |save ls mant in d6 | |
131 | lsll %d3,%d1 |shift ls mant by count | |
132 | movel #32,%d5 | |
133 | subl %d3,%d5 |sub 32 from shift for ls mant | |
134 | lsrl %d5,%d6 |shift off all bits but those that will | |
135 | | ;be shifted into ms mant | |
136 | orl %d6,%d0 |shift the ls mant bits into the ms mant | |
137 | moveml (%a7)+,%d3/%d5/%d6 |restore registers | |
138 | shft_end: | |
139 | rts | |
140 | ||
141 | |end |