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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
581: ! %o0 is negative, %o1 is nonnegative
59 sub %g0, %o0, %o0 ! make %o0 nonnegative
602:
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
731:
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
167Lnot_really_big:
1681:
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
178Ldivloop:
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
203L.4.23:
204 ! remainder is negative
205 addcc %o3,%o5,%o3
206 b 9f
207 add %o2, (7*2-1), %o2
208
209L.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
220L.4.21:
221 ! remainder is negative
222 addcc %o3,%o5,%o3
223 b 9f
224 add %o2, (5*2-1), %o2
225
226L.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
242L.4.19:
243 ! remainder is negative
244 addcc %o3,%o5,%o3
245 b 9f
246 add %o2, (3*2-1), %o2
247
248
249L.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
260L.4.17:
261 ! remainder is negative
262 addcc %o3,%o5,%o3
263 b 9f
264 add %o2, (1*2-1), %o2
265
266L.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
287L.4.15:
288 ! remainder is negative
289 addcc %o3,%o5,%o3
290 b 9f
291 add %o2, (-1*2-1), %o2
292
293L.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
304L.4.13:
305 ! remainder is negative
306 addcc %o3,%o5,%o3
307 b 9f
308 add %o2, (-3*2-1), %o2
309
310L.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
326L.4.11:
327 ! remainder is negative
328 addcc %o3,%o5,%o3
329 b 9f
330 add %o2, (-5*2-1), %o2
331
332L.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
343L.4.9:
344 ! remainder is negative
345 addcc %o3,%o5,%o3
346 b 9f
347 add %o2, (-7*2-1), %o2
348
349 9:
350Lend_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
359Lgot_result:
360 ! check to see if answer should be < 0
361 tst %g2
362 bl,a 1f
363 sub %g0, %o2, %o2
3641:
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
3781: retl
379 nop