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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/* $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
Al Viro7caaeab2005-09-11 20:14:07 -070046 .globl _Div
Linus Torvalds1da177e2005-04-16 15:20:36 -070047.div:
Al Viro7caaeab2005-09-11 20:14:07 -070048_Div: /* needed for export */
Linus Torvalds1da177e2005-04-16 15:20:36 -070049 ! compute sign of result; if neither is negative, no problem
50 orcc %o1, %o0, %g0 ! either negative?
51 bge 2f ! no, go do the divide
52 xor %o1, %o0, %g2 ! compute sign in any case
53
54 tst %o1
55 bge 1f
56 tst %o0
57 ! %o1 is definitely negative; %o0 might also be negative
58 bge 2f ! if %o0 not negative...
59 sub %g0, %o1, %o1 ! in any case, make %o1 nonneg
601: ! %o0 is negative, %o1 is nonnegative
61 sub %g0, %o0, %o0 ! make %o0 nonnegative
622:
63
64 ! Ready to divide. Compute size of quotient; scale comparand.
65 orcc %o1, %g0, %o5
66 bne 1f
67 mov %o0, %o3
68
69 ! Divide by zero trap. If it returns, return 0 (about as
70 ! wrong as possible, but that is what SunOS does...).
71 ta ST_DIV0
72 retl
73 clr %o0
74
751:
76 cmp %o3, %o5 ! if %o1 exceeds %o0, done
77 blu Lgot_result ! (and algorithm fails otherwise)
78 clr %o2
79
80 sethi %hi(1 << (32 - 4 - 1)), %g1
81
82 cmp %o3, %g1
83 blu Lnot_really_big
84 clr %o4
85
86 ! Here the dividend is >= 2**(31-N) or so. We must be careful here,
87 ! as our usual N-at-a-shot divide step will cause overflow and havoc.
88 ! The number of bits in the result here is N*ITER+SC, where SC <= N.
89 ! Compute ITER in an unorthodox manner: know we need to shift V into
90 ! the top decade: so do not even bother to compare to R.
91 1:
92 cmp %o5, %g1
93 bgeu 3f
94 mov 1, %g7
95
96 sll %o5, 4, %o5
97
98 b 1b
99 add %o4, 1, %o4
100
101 ! Now compute %g7.
102 2:
103 addcc %o5, %o5, %o5
104 bcc Lnot_too_big
105 add %g7, 1, %g7
106
107 ! We get here if the %o1 overflowed while shifting.
108 ! This means that %o3 has the high-order bit set.
109 ! Restore %o5 and subtract from %o3.
110 sll %g1, 4, %g1 ! high order bit
111 srl %o5, 1, %o5 ! rest of %o5
112 add %o5, %g1, %o5
113
114 b Ldo_single_div
115 sub %g7, 1, %g7
116
117 Lnot_too_big:
118 3:
119 cmp %o5, %o3
120 blu 2b
121 nop
122
123 be Ldo_single_div
124 nop
125 /* NB: these are commented out in the V8-Sparc manual as well */
126 /* (I do not understand this) */
127 ! %o5 > %o3: went too far: back up 1 step
128 ! srl %o5, 1, %o5
129 ! dec %g7
130 ! do single-bit divide steps
131 !
132 ! We have to be careful here. We know that %o3 >= %o5, so we can do the
133 ! first divide step without thinking. BUT, the others are conditional,
134 ! and are only done if %o3 >= 0. Because both %o3 and %o5 may have the high-
135 ! order bit set in the first step, just falling into the regular
136 ! division loop will mess up the first time around.
137 ! So we unroll slightly...
138 Ldo_single_div:
139 subcc %g7, 1, %g7
140 bl Lend_regular_divide
141 nop
142
143 sub %o3, %o5, %o3
144 mov 1, %o2
145
146 b Lend_single_divloop
147 nop
148 Lsingle_divloop:
149 sll %o2, 1, %o2
150
151 bl 1f
152 srl %o5, 1, %o5
153 ! %o3 >= 0
154 sub %o3, %o5, %o3
155
156 b 2f
157 add %o2, 1, %o2
158 1: ! %o3 < 0
159 add %o3, %o5, %o3
160 sub %o2, 1, %o2
161 2:
162 Lend_single_divloop:
163 subcc %g7, 1, %g7
164 bge Lsingle_divloop
165 tst %o3
166
167 b,a Lend_regular_divide
168
169Lnot_really_big:
1701:
171 sll %o5, 4, %o5
172 cmp %o5, %o3
173 bleu 1b
174 addcc %o4, 1, %o4
175
176 be Lgot_result
177 sub %o4, 1, %o4
178
179 tst %o3 ! set up for initial iteration
180Ldivloop:
181 sll %o2, 4, %o2
182 ! depth 1, accumulated bits 0
183 bl L.1.16
184 srl %o5,1,%o5
185 ! remainder is positive
186 subcc %o3,%o5,%o3
187 ! depth 2, accumulated bits 1
188 bl L.2.17
189 srl %o5,1,%o5
190 ! remainder is positive
191 subcc %o3,%o5,%o3
192 ! depth 3, accumulated bits 3
193 bl L.3.19
194 srl %o5,1,%o5
195 ! remainder is positive
196 subcc %o3,%o5,%o3
197 ! depth 4, accumulated bits 7
198 bl L.4.23
199 srl %o5,1,%o5
200 ! remainder is positive
201 subcc %o3,%o5,%o3
202 b 9f
203 add %o2, (7*2+1), %o2
204
205L.4.23:
206 ! remainder is negative
207 addcc %o3,%o5,%o3
208 b 9f
209 add %o2, (7*2-1), %o2
210
211L.3.19:
212 ! remainder is negative
213 addcc %o3,%o5,%o3
214 ! depth 4, accumulated bits 5
215 bl L.4.21
216 srl %o5,1,%o5
217 ! remainder is positive
218 subcc %o3,%o5,%o3
219 b 9f
220 add %o2, (5*2+1), %o2
221
222L.4.21:
223 ! remainder is negative
224 addcc %o3,%o5,%o3
225 b 9f
226 add %o2, (5*2-1), %o2
227
228L.2.17:
229 ! remainder is negative
230 addcc %o3,%o5,%o3
231 ! depth 3, accumulated bits 1
232 bl L.3.17
233 srl %o5,1,%o5
234 ! remainder is positive
235 subcc %o3,%o5,%o3
236 ! depth 4, accumulated bits 3
237 bl L.4.19
238 srl %o5,1,%o5
239 ! remainder is positive
240 subcc %o3,%o5,%o3
241 b 9f
242 add %o2, (3*2+1), %o2
243
244L.4.19:
245 ! remainder is negative
246 addcc %o3,%o5,%o3
247 b 9f
248 add %o2, (3*2-1), %o2
249
250
251L.3.17:
252 ! remainder is negative
253 addcc %o3,%o5,%o3
254 ! depth 4, accumulated bits 1
255 bl L.4.17
256 srl %o5,1,%o5
257 ! remainder is positive
258 subcc %o3,%o5,%o3
259 b 9f
260 add %o2, (1*2+1), %o2
261
262L.4.17:
263 ! remainder is negative
264 addcc %o3,%o5,%o3
265 b 9f
266 add %o2, (1*2-1), %o2
267
268L.1.16:
269 ! remainder is negative
270 addcc %o3,%o5,%o3
271 ! depth 2, accumulated bits -1
272 bl L.2.15
273 srl %o5,1,%o5
274 ! remainder is positive
275 subcc %o3,%o5,%o3
276 ! depth 3, accumulated bits -1
277 bl L.3.15
278 srl %o5,1,%o5
279 ! remainder is positive
280 subcc %o3,%o5,%o3
281 ! depth 4, accumulated bits -1
282 bl L.4.15
283 srl %o5,1,%o5
284 ! remainder is positive
285 subcc %o3,%o5,%o3
286 b 9f
287 add %o2, (-1*2+1), %o2
288
289L.4.15:
290 ! remainder is negative
291 addcc %o3,%o5,%o3
292 b 9f
293 add %o2, (-1*2-1), %o2
294
295L.3.15:
296 ! remainder is negative
297 addcc %o3,%o5,%o3
298 ! depth 4, accumulated bits -3
299 bl L.4.13
300 srl %o5,1,%o5
301 ! remainder is positive
302 subcc %o3,%o5,%o3
303 b 9f
304 add %o2, (-3*2+1), %o2
305
306L.4.13:
307 ! remainder is negative
308 addcc %o3,%o5,%o3
309 b 9f
310 add %o2, (-3*2-1), %o2
311
312L.2.15:
313 ! remainder is negative
314 addcc %o3,%o5,%o3
315 ! depth 3, accumulated bits -3
316 bl L.3.13
317 srl %o5,1,%o5
318 ! remainder is positive
319 subcc %o3,%o5,%o3
320 ! depth 4, accumulated bits -5
321 bl L.4.11
322 srl %o5,1,%o5
323 ! remainder is positive
324 subcc %o3,%o5,%o3
325 b 9f
326 add %o2, (-5*2+1), %o2
327
328L.4.11:
329 ! remainder is negative
330 addcc %o3,%o5,%o3
331 b 9f
332 add %o2, (-5*2-1), %o2
333
334L.3.13:
335 ! remainder is negative
336 addcc %o3,%o5,%o3
337 ! depth 4, accumulated bits -7
338 bl L.4.9
339 srl %o5,1,%o5
340 ! remainder is positive
341 subcc %o3,%o5,%o3
342 b 9f
343 add %o2, (-7*2+1), %o2
344
345L.4.9:
346 ! remainder is negative
347 addcc %o3,%o5,%o3
348 b 9f
349 add %o2, (-7*2-1), %o2
350
351 9:
352Lend_regular_divide:
353 subcc %o4, 1, %o4
354 bge Ldivloop
355 tst %o3
356
357 bl,a Lgot_result
358 ! non-restoring fixup here (one instruction only!)
359 sub %o2, 1, %o2
360
361Lgot_result:
362 ! check to see if answer should be < 0
363 tst %g2
364 bl,a 1f
365 sub %g0, %o2, %o2
3661:
367 retl
368 mov %o2, %o0
369
370 .globl .div_patch
371.div_patch:
372 sra %o0, 0x1f, %o2
373 wr %o2, 0x0, %y
374 nop
375 nop
376 nop
377 sdivcc %o0, %o1, %o0
378 bvs,a 1f
379 xnor %o0, %g0, %o0
3801: retl
381 nop