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Diffstat (limited to 'arch/sparc/lib/sdiv.S')
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1 | /* $Id: sdiv.S,v 1.6 1996/10/02 17:37:00 davem Exp $ | ||
2 | * sdiv.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 | * .div name of function to generate | ||
18 | * div div=div => %o0 / %o1; div=rem => %o0 % %o1 | ||
19 | * true true=true => signed; true=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 .div | ||
46 | .div: | ||
47 | ! compute sign of result; if neither is negative, no problem | ||
48 | orcc %o1, %o0, %g0 ! either negative? | ||
49 | bge 2f ! no, go do the divide | ||
50 | xor %o1, %o0, %g2 ! compute sign in any case | ||
51 | |||
52 | tst %o1 | ||
53 | bge 1f | ||
54 | tst %o0 | ||
55 | ! %o1 is definitely negative; %o0 might also be negative | ||
56 | bge 2f ! if %o0 not negative... | ||
57 | sub %g0, %o1, %o1 ! in any case, make %o1 nonneg | ||
58 | 1: ! %o0 is negative, %o1 is nonnegative | ||
59 | sub %g0, %o0, %o0 ! make %o0 nonnegative | ||
60 | 2: | ||
61 | |||
62 | ! Ready to divide. Compute size of quotient; scale comparand. | ||
63 | orcc %o1, %g0, %o5 | ||
64 | bne 1f | ||
65 | mov %o0, %o3 | ||
66 | |||
67 | ! Divide by zero trap. If it returns, return 0 (about as | ||
68 | ! wrong as possible, but that is what SunOS does...). | ||
69 | ta ST_DIV0 | ||
70 | retl | ||
71 | clr %o0 | ||
72 | |||
73 | 1: | ||
74 | cmp %o3, %o5 ! if %o1 exceeds %o0, done | ||
75 | blu Lgot_result ! (and algorithm fails otherwise) | ||
76 | clr %o2 | ||
77 | |||
78 | sethi %hi(1 << (32 - 4 - 1)), %g1 | ||
79 | |||
80 | cmp %o3, %g1 | ||
81 | blu Lnot_really_big | ||
82 | clr %o4 | ||
83 | |||
84 | ! Here the dividend is >= 2**(31-N) or so. We must be careful here, | ||
85 | ! as our usual N-at-a-shot divide step will cause overflow and havoc. | ||
86 | ! The number of bits in the result here is N*ITER+SC, where SC <= N. | ||
87 | ! Compute ITER in an unorthodox manner: know we need to shift V into | ||
88 | ! the top decade: so do not even bother to compare to R. | ||
89 | 1: | ||
90 | cmp %o5, %g1 | ||
91 | bgeu 3f | ||
92 | mov 1, %g7 | ||
93 | |||
94 | sll %o5, 4, %o5 | ||
95 | |||
96 | b 1b | ||
97 | add %o4, 1, %o4 | ||
98 | |||
99 | ! Now compute %g7. | ||
100 | 2: | ||
101 | addcc %o5, %o5, %o5 | ||
102 | bcc Lnot_too_big | ||
103 | add %g7, 1, %g7 | ||
104 | |||
105 | ! We get here if the %o1 overflowed while shifting. | ||
106 | ! This means that %o3 has the high-order bit set. | ||
107 | ! Restore %o5 and subtract from %o3. | ||
108 | sll %g1, 4, %g1 ! high order bit | ||
109 | srl %o5, 1, %o5 ! rest of %o5 | ||
110 | add %o5, %g1, %o5 | ||
111 | |||
112 | b Ldo_single_div | ||
113 | sub %g7, 1, %g7 | ||
114 | |||
115 | Lnot_too_big: | ||
116 | 3: | ||
117 | cmp %o5, %o3 | ||
118 | blu 2b | ||
119 | nop | ||
120 | |||
121 | be Ldo_single_div | ||
122 | nop | ||
123 | /* NB: these are commented out in the V8-Sparc manual as well */ | ||
124 | /* (I do not understand this) */ | ||
125 | ! %o5 > %o3: went too far: back up 1 step | ||
126 | ! srl %o5, 1, %o5 | ||
127 | ! dec %g7 | ||
128 | ! do single-bit divide steps | ||
129 | ! | ||
130 | ! We have to be careful here. We know that %o3 >= %o5, so we can do the | ||
131 | ! first divide step without thinking. BUT, the others are conditional, | ||
132 | ! and are only done if %o3 >= 0. Because both %o3 and %o5 may have the high- | ||
133 | ! order bit set in the first step, just falling into the regular | ||
134 | ! division loop will mess up the first time around. | ||
135 | ! So we unroll slightly... | ||
136 | Ldo_single_div: | ||
137 | subcc %g7, 1, %g7 | ||
138 | bl Lend_regular_divide | ||
139 | nop | ||
140 | |||
141 | sub %o3, %o5, %o3 | ||
142 | mov 1, %o2 | ||
143 | |||
144 | b Lend_single_divloop | ||
145 | nop | ||
146 | Lsingle_divloop: | ||
147 | sll %o2, 1, %o2 | ||
148 | |||
149 | bl 1f | ||
150 | srl %o5, 1, %o5 | ||
151 | ! %o3 >= 0 | ||
152 | sub %o3, %o5, %o3 | ||
153 | |||
154 | b 2f | ||
155 | add %o2, 1, %o2 | ||
156 | 1: ! %o3 < 0 | ||
157 | add %o3, %o5, %o3 | ||
158 | sub %o2, 1, %o2 | ||
159 | 2: | ||
160 | Lend_single_divloop: | ||
161 | subcc %g7, 1, %g7 | ||
162 | bge Lsingle_divloop | ||
163 | tst %o3 | ||
164 | |||
165 | b,a Lend_regular_divide | ||
166 | |||
167 | Lnot_really_big: | ||
168 | 1: | ||
169 | sll %o5, 4, %o5 | ||
170 | cmp %o5, %o3 | ||
171 | bleu 1b | ||
172 | addcc %o4, 1, %o4 | ||
173 | |||
174 | be Lgot_result | ||
175 | sub %o4, 1, %o4 | ||
176 | |||
177 | tst %o3 ! set up for initial iteration | ||
178 | Ldivloop: | ||
179 | sll %o2, 4, %o2 | ||
180 | ! depth 1, accumulated bits 0 | ||
181 | bl L.1.16 | ||
182 | srl %o5,1,%o5 | ||
183 | ! remainder is positive | ||
184 | subcc %o3,%o5,%o3 | ||
185 | ! depth 2, accumulated bits 1 | ||
186 | bl L.2.17 | ||
187 | srl %o5,1,%o5 | ||
188 | ! remainder is positive | ||
189 | subcc %o3,%o5,%o3 | ||
190 | ! depth 3, accumulated bits 3 | ||
191 | bl L.3.19 | ||
192 | srl %o5,1,%o5 | ||
193 | ! remainder is positive | ||
194 | subcc %o3,%o5,%o3 | ||
195 | ! depth 4, accumulated bits 7 | ||
196 | bl L.4.23 | ||
197 | srl %o5,1,%o5 | ||
198 | ! remainder is positive | ||
199 | subcc %o3,%o5,%o3 | ||
200 | b 9f | ||
201 | add %o2, (7*2+1), %o2 | ||
202 | |||
203 | L.4.23: | ||
204 | ! remainder is negative | ||
205 | addcc %o3,%o5,%o3 | ||
206 | b 9f | ||
207 | add %o2, (7*2-1), %o2 | ||
208 | |||
209 | L.3.19: | ||
210 | ! remainder is negative | ||
211 | addcc %o3,%o5,%o3 | ||
212 | ! depth 4, accumulated bits 5 | ||
213 | bl L.4.21 | ||
214 | srl %o5,1,%o5 | ||
215 | ! remainder is positive | ||
216 | subcc %o3,%o5,%o3 | ||
217 | b 9f | ||
218 | add %o2, (5*2+1), %o2 | ||
219 | |||
220 | L.4.21: | ||
221 | ! remainder is negative | ||
222 | addcc %o3,%o5,%o3 | ||
223 | b 9f | ||
224 | add %o2, (5*2-1), %o2 | ||
225 | |||
226 | L.2.17: | ||
227 | ! remainder is negative | ||
228 | addcc %o3,%o5,%o3 | ||
229 | ! depth 3, accumulated bits 1 | ||
230 | bl L.3.17 | ||
231 | srl %o5,1,%o5 | ||
232 | ! remainder is positive | ||
233 | subcc %o3,%o5,%o3 | ||
234 | ! depth 4, accumulated bits 3 | ||
235 | bl L.4.19 | ||
236 | srl %o5,1,%o5 | ||
237 | ! remainder is positive | ||
238 | subcc %o3,%o5,%o3 | ||
239 | b 9f | ||
240 | add %o2, (3*2+1), %o2 | ||
241 | |||
242 | L.4.19: | ||
243 | ! remainder is negative | ||
244 | addcc %o3,%o5,%o3 | ||
245 | b 9f | ||
246 | add %o2, (3*2-1), %o2 | ||
247 | |||
248 | |||
249 | L.3.17: | ||
250 | ! remainder is negative | ||
251 | addcc %o3,%o5,%o3 | ||
252 | ! depth 4, accumulated bits 1 | ||
253 | bl L.4.17 | ||
254 | srl %o5,1,%o5 | ||
255 | ! remainder is positive | ||
256 | subcc %o3,%o5,%o3 | ||
257 | b 9f | ||
258 | add %o2, (1*2+1), %o2 | ||
259 | |||
260 | L.4.17: | ||
261 | ! remainder is negative | ||
262 | addcc %o3,%o5,%o3 | ||
263 | b 9f | ||
264 | add %o2, (1*2-1), %o2 | ||
265 | |||
266 | L.1.16: | ||
267 | ! remainder is negative | ||
268 | addcc %o3,%o5,%o3 | ||
269 | ! depth 2, accumulated bits -1 | ||
270 | bl L.2.15 | ||
271 | srl %o5,1,%o5 | ||
272 | ! remainder is positive | ||
273 | subcc %o3,%o5,%o3 | ||
274 | ! depth 3, accumulated bits -1 | ||
275 | bl L.3.15 | ||
276 | srl %o5,1,%o5 | ||
277 | ! remainder is positive | ||
278 | subcc %o3,%o5,%o3 | ||
279 | ! depth 4, accumulated bits -1 | ||
280 | bl L.4.15 | ||
281 | srl %o5,1,%o5 | ||
282 | ! remainder is positive | ||
283 | subcc %o3,%o5,%o3 | ||
284 | b 9f | ||
285 | add %o2, (-1*2+1), %o2 | ||
286 | |||
287 | L.4.15: | ||
288 | ! remainder is negative | ||
289 | addcc %o3,%o5,%o3 | ||
290 | b 9f | ||
291 | add %o2, (-1*2-1), %o2 | ||
292 | |||
293 | L.3.15: | ||
294 | ! remainder is negative | ||
295 | addcc %o3,%o5,%o3 | ||
296 | ! depth 4, accumulated bits -3 | ||
297 | bl L.4.13 | ||
298 | srl %o5,1,%o5 | ||
299 | ! remainder is positive | ||
300 | subcc %o3,%o5,%o3 | ||
301 | b 9f | ||
302 | add %o2, (-3*2+1), %o2 | ||
303 | |||
304 | L.4.13: | ||
305 | ! remainder is negative | ||
306 | addcc %o3,%o5,%o3 | ||
307 | b 9f | ||
308 | add %o2, (-3*2-1), %o2 | ||
309 | |||
310 | L.2.15: | ||
311 | ! remainder is negative | ||
312 | addcc %o3,%o5,%o3 | ||
313 | ! depth 3, accumulated bits -3 | ||
314 | bl L.3.13 | ||
315 | srl %o5,1,%o5 | ||
316 | ! remainder is positive | ||
317 | subcc %o3,%o5,%o3 | ||
318 | ! depth 4, accumulated bits -5 | ||
319 | bl L.4.11 | ||
320 | srl %o5,1,%o5 | ||
321 | ! remainder is positive | ||
322 | subcc %o3,%o5,%o3 | ||
323 | b 9f | ||
324 | add %o2, (-5*2+1), %o2 | ||
325 | |||
326 | L.4.11: | ||
327 | ! remainder is negative | ||
328 | addcc %o3,%o5,%o3 | ||
329 | b 9f | ||
330 | add %o2, (-5*2-1), %o2 | ||
331 | |||
332 | L.3.13: | ||
333 | ! remainder is negative | ||
334 | addcc %o3,%o5,%o3 | ||
335 | ! depth 4, accumulated bits -7 | ||
336 | bl L.4.9 | ||
337 | srl %o5,1,%o5 | ||
338 | ! remainder is positive | ||
339 | subcc %o3,%o5,%o3 | ||
340 | b 9f | ||
341 | add %o2, (-7*2+1), %o2 | ||
342 | |||
343 | L.4.9: | ||
344 | ! remainder is negative | ||
345 | addcc %o3,%o5,%o3 | ||
346 | b 9f | ||
347 | add %o2, (-7*2-1), %o2 | ||
348 | |||
349 | 9: | ||
350 | Lend_regular_divide: | ||
351 | subcc %o4, 1, %o4 | ||
352 | bge Ldivloop | ||
353 | tst %o3 | ||
354 | |||
355 | bl,a Lgot_result | ||
356 | ! non-restoring fixup here (one instruction only!) | ||
357 | sub %o2, 1, %o2 | ||
358 | |||
359 | Lgot_result: | ||
360 | ! check to see if answer should be < 0 | ||
361 | tst %g2 | ||
362 | bl,a 1f | ||
363 | sub %g0, %o2, %o2 | ||
364 | 1: | ||
365 | retl | ||
366 | mov %o2, %o0 | ||
367 | |||
368 | .globl .div_patch | ||
369 | .div_patch: | ||
370 | sra %o0, 0x1f, %o2 | ||
371 | wr %o2, 0x0, %y | ||
372 | nop | ||
373 | nop | ||
374 | nop | ||
375 | sdivcc %o0, %o1, %o0 | ||
376 | bvs,a 1f | ||
377 | xnor %o0, %g0, %o0 | ||
378 | 1: retl | ||
379 | nop | ||