1 |
2 | slog2.sa 3.1 12/10/90
3 |
4 | The entry point slog10 computes the ba
5 | logarithm of an input argument X.
6 | slog10d does the same except the input
7 | denormalized number.
8 | sLog2 and sLog2d are the base-2 analog
9 |
10 | INPUT: Double-extended value in memor
11 | by address register a0.
12 |
13 | OUTPUT: log_10(X) or log_2(X) returned
14 | register fp0.
15 |
16 | ACCURACY and MONOTONICITY: The returne
17 | ulps in 64 significant bit, i.
18 | to 53 bits if the result is su
19 | to double precision. The resul
20 | in double precision.
21 |
22 | SPEED: Two timings are measured, both
23 | The first one is measured when
24 | the first time (so the instruc
25 | in cache), and the second one
26 | function is reinvoked at the s
27 |
28 | ALGORITHM and IMPLEMENTATION NOTES:
29 |
30 | slog10d:
31 |
32 | Step 0. If X < 0, create a NaN and r
33 | flag. Otherwise, save FPCR i
34 | Notes: Default means round-to-neare
35 | traps, and precision control
36 |
37 | Step 1. Call slognd to obtain Y = lo
38 | Notes: Even if X is denormalized, l
39 |
40 | Step 2. Compute log_10(X) = log(X) *
41 | 2.1 Restore the user FPCR
42 | 2.2 Return ans := Y * INV_L10.
43 |
44 |
45 | slog10:
46 |
47 | Step 0. If X < 0, create a NaN and r
48 | flag. Otherwise, save FPCR i
49 | Notes: Default means round-to-neare
50 | traps, and precision control
51 |
52 | Step 1. Call sLogN to obtain Y = log
53 |
54 | Step 2. Compute log_10(X) = log(X) *
55 | 2.1 Restore the user FPCR
56 | 2.2 Return ans := Y * INV_L10.
57 |
58 |
59 | sLog2d:
60 |
61 | Step 0. If X < 0, create a NaN and r
62 | flag. Otherwise, save FPCR i
63 | Notes: Default means round-to-neare
64 | traps, and precision control
65 |
66 | Step 1. Call slognd to obtain Y = lo
67 | Notes: Even if X is denormalized, l
68 |
69 | Step 2. Compute log_10(X) = log(X) *
70 | 2.1 Restore the user FPCR
71 | 2.2 Return ans := Y * INV_L2.
72 |
73 |
74 | sLog2:
75 |
76 | Step 0. If X < 0, create a NaN and r
77 | flag. Otherwise, save FPCR i
78 | Notes: Default means round-to-neare
79 | traps, and precision control
80 |
81 | Step 1. If X is not an integer power
82 | go to Step 3.
83 |
84 | Step 2. Return k.
85 | 2.1 Get integer k, X = 2^k.
86 | 2.2 Restore the user FPCR.
87 | 2.3 Return ans := convert-to-dou
88 |
89 | Step 3. Call sLogN to obtain Y = log
90 |
91 | Step 4. Compute log_2(X) = log(X) *
92 | 4.1 Restore the user FPCR
93 | 4.2 Return ans := Y * INV_L2.
94 |
95
96 | Copyright (C) Motorola, Inc. 1
97 | All Rights Reserved
98 |
99 | For details on the license for this fi
100 | file, README, in this same directory.
101
102 |SLOG2 idnt 2,1 | Motorola 040 Floating
103
104 |section 8
105
106 |xref t_frcinx
107 |xref t_operr
108 |xref slogn
109 |xref slognd
110
111 INV_L10: .long 0x3FFD0000,0xDE5BD8A9,0x372871
112
113 INV_L2: .long 0x3FFF0000,0xB8AA3B29,0x5C17F0
114
115 .global slog10d
116 slog10d:
117 |--entry point for Log10(X), X is denormalized
118 movel (%a0),%d0
119 blt invalid
120 movel %d1,-(%sp)
121 clrl %d1
122 bsr slognd
123 fmovel (%sp)+,%fpcr
124 fmulx INV_L10,%fp0
125 bra t_frcinx
126
127 .global slog10
128 slog10:
129 |--entry point for Log10(X), X is normalized
130
131 movel (%a0),%d0
132 blt invalid
133 movel %d1,-(%sp)
134 clrl %d1
135 bsr slogn
136 fmovel (%sp)+,%fpcr
137 fmulx INV_L10,%fp0
138 bra t_frcinx
139
140
141 .global slog2d
142 slog2d:
143 |--entry point for Log2(X), X is denormalized
144
145 movel (%a0),%d0
146 blt invalid
147 movel %d1,-(%sp)
148 clrl %d1
149 bsr slognd
150 fmovel (%sp)+,%fpcr
151 fmulx INV_L2,%fp0
152 bra t_frcinx
153
154 .global slog2
155 slog2:
156 |--entry point for Log2(X), X is normalized
157 movel (%a0),%d0
158 blt invalid
159
160 movel 8(%a0),%d0
161 bnes continue
162
163 movel 4(%a0),%d0
164 andl #0x7FFFFFFF,%d0
165 tstl %d0
166 bnes continue
167
168 |--X = 2^k.
169 movew (%a0),%d0
170 andl #0x00007FFF,%d0
171 subl #0x3FFF,%d0
172 fmovel %d1,%fpcr
173 fmovel %d0,%fp0
174 bra t_frcinx
175
176 continue:
177 movel %d1,-(%sp)
178 clrl %d1
179 bsr slogn
180 fmovel (%sp)+,%fpcr
181 fmulx INV_L2,%fp0
182 bra t_frcinx
183
184 invalid:
185 bra t_operr
186
187 |end
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