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Diffstat (limited to 'arch/sparc/lib/udiv.S')
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1 | /* $Id: udiv.S,v 1.4 1996/09/30 02:22:38 davem Exp $ | ||
2 | * udiv.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 | /* This file is generated from divrem.m4; DO NOT EDIT! */ | ||
8 | /* | ||
9 | * Division and remainder, from Appendix E of the Sparc Version 8 | ||
10 | * Architecture Manual, with fixes from Gordon Irlam. | ||
11 | */ | ||
12 | |||
13 | /* | ||
14 | * Input: dividend and divisor in %o0 and %o1 respectively. | ||
15 | * | ||
16 | * m4 parameters: | ||
17 | * .udiv name of function to generate | ||
18 | * div div=div => %o0 / %o1; div=rem => %o0 % %o1 | ||
19 | * false false=true => signed; false=false => unsigned | ||
20 | * | ||
21 | * Algorithm parameters: | ||
22 | * N how many bits per iteration we try to get (4) | ||
23 | * WORDSIZE total number of bits (32) | ||
24 | * | ||
25 | * Derived constants: | ||
26 | * TOPBITS number of bits in the top decade of a number | ||
27 | * | ||
28 | * Important variables: | ||
29 | * Q the partial quotient under development (initially 0) | ||
30 | * R the remainder so far, initially the dividend | ||
31 | * ITER number of main division loop iterations required; | ||
32 | * equal to ceil(log2(quotient) / N). Note that this | ||
33 | * is the log base (2^N) of the quotient. | ||
34 | * V the current comparand, initially divisor*2^(ITER*N-1) | ||
35 | * | ||
36 | * Cost: | ||
37 | * Current estimate for non-large dividend is | ||
38 | * ceil(log2(quotient) / N) * (10 + 7N/2) + C | ||
39 | * A large dividend is one greater than 2^(31-TOPBITS) and takes a | ||
40 | * different path, as the upper bits of the quotient must be developed | ||
41 | * one bit at a time. | ||
42 | */ | ||
43 | |||
44 | |||
45 | .globl .udiv | ||
46 | .udiv: | ||
47 | |||
48 | ! Ready to divide. Compute size of quotient; scale comparand. | ||
49 | orcc %o1, %g0, %o5 | ||
50 | bne 1f | ||
51 | mov %o0, %o3 | ||
52 | |||
53 | ! Divide by zero trap. If it returns, return 0 (about as | ||
54 | ! wrong as possible, but that is what SunOS does...). | ||
55 | ta ST_DIV0 | ||
56 | retl | ||
57 | clr %o0 | ||
58 | |||
59 | 1: | ||
60 | cmp %o3, %o5 ! if %o1 exceeds %o0, done | ||
61 | blu Lgot_result ! (and algorithm fails otherwise) | ||
62 | clr %o2 | ||
63 | |||
64 | sethi %hi(1 << (32 - 4 - 1)), %g1 | ||
65 | |||
66 | cmp %o3, %g1 | ||
67 | blu Lnot_really_big | ||
68 | clr %o4 | ||
69 | |||
70 | ! Here the dividend is >= 2**(31-N) or so. We must be careful here, | ||
71 | ! as our usual N-at-a-shot divide step will cause overflow and havoc. | ||
72 | ! The number of bits in the result here is N*ITER+SC, where SC <= N. | ||
73 | ! Compute ITER in an unorthodox manner: know we need to shift V into | ||
74 | ! the top decade: so do not even bother to compare to R. | ||
75 | 1: | ||
76 | cmp %o5, %g1 | ||
77 | bgeu 3f | ||
78 | mov 1, %g7 | ||
79 | |||
80 | sll %o5, 4, %o5 | ||
81 | |||
82 | b 1b | ||
83 | add %o4, 1, %o4 | ||
84 | |||
85 | ! Now compute %g7. | ||
86 | 2: | ||
87 | addcc %o5, %o5, %o5 | ||
88 | bcc Lnot_too_big | ||
89 | add %g7, 1, %g7 | ||
90 | |||
91 | ! We get here if the %o1 overflowed while shifting. | ||
92 | ! This means that %o3 has the high-order bit set. | ||
93 | ! Restore %o5 and subtract from %o3. | ||
94 | sll %g1, 4, %g1 ! high order bit | ||
95 | srl %o5, 1, %o5 ! rest of %o5 | ||
96 | add %o5, %g1, %o5 | ||
97 | |||
98 | b Ldo_single_div | ||
99 | sub %g7, 1, %g7 | ||
100 | |||
101 | Lnot_too_big: | ||
102 | 3: | ||
103 | cmp %o5, %o3 | ||
104 | blu 2b | ||
105 | nop | ||
106 | |||
107 | be Ldo_single_div | ||
108 | nop | ||
109 | /* NB: these are commented out in the V8-Sparc manual as well */ | ||
110 | /* (I do not understand this) */ | ||
111 | ! %o5 > %o3: went too far: back up 1 step | ||
112 | ! srl %o5, 1, %o5 | ||
113 | ! dec %g7 | ||
114 | ! do single-bit divide steps | ||
115 | ! | ||
116 | ! We have to be careful here. We know that %o3 >= %o5, so we can do the | ||
117 | ! first divide step without thinking. BUT, the others are conditional, | ||
118 | ! and are only done if %o3 >= 0. Because both %o3 and %o5 may have the high- | ||
119 | ! order bit set in the first step, just falling into the regular | ||
120 | ! division loop will mess up the first time around. | ||
121 | ! So we unroll slightly... | ||
122 | Ldo_single_div: | ||
123 | subcc %g7, 1, %g7 | ||
124 | bl Lend_regular_divide | ||
125 | nop | ||
126 | |||
127 | sub %o3, %o5, %o3 | ||
128 | mov 1, %o2 | ||
129 | |||
130 | b Lend_single_divloop | ||
131 | nop | ||
132 | Lsingle_divloop: | ||
133 | sll %o2, 1, %o2 | ||
134 | bl 1f | ||
135 | srl %o5, 1, %o5 | ||
136 | ! %o3 >= 0 | ||
137 | sub %o3, %o5, %o3 | ||
138 | b 2f | ||
139 | add %o2, 1, %o2 | ||
140 | 1: ! %o3 < 0 | ||
141 | add %o3, %o5, %o3 | ||
142 | sub %o2, 1, %o2 | ||
143 | 2: | ||
144 | Lend_single_divloop: | ||
145 | subcc %g7, 1, %g7 | ||
146 | bge Lsingle_divloop | ||
147 | tst %o3 | ||
148 | |||
149 | b,a Lend_regular_divide | ||
150 | |||
151 | Lnot_really_big: | ||
152 | 1: | ||
153 | sll %o5, 4, %o5 | ||
154 | |||
155 | cmp %o5, %o3 | ||
156 | bleu 1b | ||
157 | addcc %o4, 1, %o4 | ||
158 | |||
159 | be Lgot_result | ||
160 | sub %o4, 1, %o4 | ||
161 | |||
162 | tst %o3 ! set up for initial iteration | ||
163 | Ldivloop: | ||
164 | sll %o2, 4, %o2 | ||
165 | ! depth 1, accumulated bits 0 | ||
166 | bl L.1.16 | ||
167 | srl %o5,1,%o5 | ||
168 | ! remainder is positive | ||
169 | subcc %o3,%o5,%o3 | ||
170 | ! depth 2, accumulated bits 1 | ||
171 | bl L.2.17 | ||
172 | srl %o5,1,%o5 | ||
173 | ! remainder is positive | ||
174 | subcc %o3,%o5,%o3 | ||
175 | ! depth 3, accumulated bits 3 | ||
176 | bl L.3.19 | ||
177 | srl %o5,1,%o5 | ||
178 | ! remainder is positive | ||
179 | subcc %o3,%o5,%o3 | ||
180 | ! depth 4, accumulated bits 7 | ||
181 | bl L.4.23 | ||
182 | srl %o5,1,%o5 | ||
183 | ! remainder is positive | ||
184 | subcc %o3,%o5,%o3 | ||
185 | b 9f | ||
186 | add %o2, (7*2+1), %o2 | ||
187 | |||
188 | L.4.23: | ||
189 | ! remainder is negative | ||
190 | addcc %o3,%o5,%o3 | ||
191 | b 9f | ||
192 | add %o2, (7*2-1), %o2 | ||
193 | |||
194 | L.3.19: | ||
195 | ! remainder is negative | ||
196 | addcc %o3,%o5,%o3 | ||
197 | ! depth 4, accumulated bits 5 | ||
198 | bl L.4.21 | ||
199 | srl %o5,1,%o5 | ||
200 | ! remainder is positive | ||
201 | subcc %o3,%o5,%o3 | ||
202 | b 9f | ||
203 | add %o2, (5*2+1), %o2 | ||
204 | |||
205 | L.4.21: | ||
206 | ! remainder is negative | ||
207 | addcc %o3,%o5,%o3 | ||
208 | b 9f | ||
209 | add %o2, (5*2-1), %o2 | ||
210 | |||
211 | L.2.17: | ||
212 | ! remainder is negative | ||
213 | addcc %o3,%o5,%o3 | ||
214 | ! depth 3, accumulated bits 1 | ||
215 | bl L.3.17 | ||
216 | srl %o5,1,%o5 | ||
217 | ! remainder is positive | ||
218 | subcc %o3,%o5,%o3 | ||
219 | ! depth 4, accumulated bits 3 | ||
220 | bl L.4.19 | ||
221 | srl %o5,1,%o5 | ||
222 | ! remainder is positive | ||
223 | subcc %o3,%o5,%o3 | ||
224 | b 9f | ||
225 | add %o2, (3*2+1), %o2 | ||
226 | |||
227 | L.4.19: | ||
228 | ! remainder is negative | ||
229 | addcc %o3,%o5,%o3 | ||
230 | b 9f | ||
231 | add %o2, (3*2-1), %o2 | ||
232 | |||
233 | L.3.17: | ||
234 | ! remainder is negative | ||
235 | addcc %o3,%o5,%o3 | ||
236 | ! depth 4, accumulated bits 1 | ||
237 | bl L.4.17 | ||
238 | srl %o5,1,%o5 | ||
239 | ! remainder is positive | ||
240 | subcc %o3,%o5,%o3 | ||
241 | b 9f | ||
242 | add %o2, (1*2+1), %o2 | ||
243 | |||
244 | L.4.17: | ||
245 | ! remainder is negative | ||
246 | addcc %o3,%o5,%o3 | ||
247 | b 9f | ||
248 | add %o2, (1*2-1), %o2 | ||
249 | |||
250 | L.1.16: | ||
251 | ! remainder is negative | ||
252 | addcc %o3,%o5,%o3 | ||
253 | ! depth 2, accumulated bits -1 | ||
254 | bl L.2.15 | ||
255 | srl %o5,1,%o5 | ||
256 | ! remainder is positive | ||
257 | subcc %o3,%o5,%o3 | ||
258 | ! depth 3, accumulated bits -1 | ||
259 | bl L.3.15 | ||
260 | srl %o5,1,%o5 | ||
261 | ! remainder is positive | ||
262 | subcc %o3,%o5,%o3 | ||
263 | ! depth 4, accumulated bits -1 | ||
264 | bl L.4.15 | ||
265 | srl %o5,1,%o5 | ||
266 | ! remainder is positive | ||
267 | subcc %o3,%o5,%o3 | ||
268 | b 9f | ||
269 | add %o2, (-1*2+1), %o2 | ||
270 | |||
271 | L.4.15: | ||
272 | ! remainder is negative | ||
273 | addcc %o3,%o5,%o3 | ||
274 | b 9f | ||
275 | add %o2, (-1*2-1), %o2 | ||
276 | |||
277 | L.3.15: | ||
278 | ! remainder is negative | ||
279 | addcc %o3,%o5,%o3 | ||
280 | ! depth 4, accumulated bits -3 | ||
281 | bl L.4.13 | ||
282 | srl %o5,1,%o5 | ||
283 | ! remainder is positive | ||
284 | subcc %o3,%o5,%o3 | ||
285 | b 9f | ||
286 | add %o2, (-3*2+1), %o2 | ||
287 | |||
288 | L.4.13: | ||
289 | ! remainder is negative | ||
290 | addcc %o3,%o5,%o3 | ||
291 | b 9f | ||
292 | add %o2, (-3*2-1), %o2 | ||
293 | |||
294 | L.2.15: | ||
295 | ! remainder is negative | ||
296 | addcc %o3,%o5,%o3 | ||
297 | ! depth 3, accumulated bits -3 | ||
298 | bl L.3.13 | ||
299 | srl %o5,1,%o5 | ||
300 | ! remainder is positive | ||
301 | subcc %o3,%o5,%o3 | ||
302 | ! depth 4, accumulated bits -5 | ||
303 | bl L.4.11 | ||
304 | srl %o5,1,%o5 | ||
305 | ! remainder is positive | ||
306 | subcc %o3,%o5,%o3 | ||
307 | b 9f | ||
308 | add %o2, (-5*2+1), %o2 | ||
309 | |||
310 | L.4.11: | ||
311 | ! remainder is negative | ||
312 | addcc %o3,%o5,%o3 | ||
313 | b 9f | ||
314 | add %o2, (-5*2-1), %o2 | ||
315 | |||
316 | L.3.13: | ||
317 | ! remainder is negative | ||
318 | addcc %o3,%o5,%o3 | ||
319 | ! depth 4, accumulated bits -7 | ||
320 | bl L.4.9 | ||
321 | srl %o5,1,%o5 | ||
322 | ! remainder is positive | ||
323 | subcc %o3,%o5,%o3 | ||
324 | b 9f | ||
325 | add %o2, (-7*2+1), %o2 | ||
326 | |||
327 | L.4.9: | ||
328 | ! remainder is negative | ||
329 | addcc %o3,%o5,%o3 | ||
330 | b 9f | ||
331 | add %o2, (-7*2-1), %o2 | ||
332 | |||
333 | 9: | ||
334 | Lend_regular_divide: | ||
335 | subcc %o4, 1, %o4 | ||
336 | bge Ldivloop | ||
337 | tst %o3 | ||
338 | |||
339 | bl,a Lgot_result | ||
340 | ! non-restoring fixup here (one instruction only!) | ||
341 | sub %o2, 1, %o2 | ||
342 | |||
343 | Lgot_result: | ||
344 | |||
345 | retl | ||
346 | mov %o2, %o0 | ||
347 | |||
348 | .globl .udiv_patch | ||
349 | .udiv_patch: | ||
350 | wr %g0, 0x0, %y | ||
351 | nop | ||
352 | nop | ||
353 | retl | ||
354 | udiv %o0, %o1, %o0 | ||
355 | nop | ||