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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 18:20:36 -0400
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 18:20:36 -0400
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/sparc/lib/rem.S
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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1/* $Id: rem.S,v 1.7 1996/09/30 02:22:34 davem Exp $
2 * rem.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 * .rem name of function to generate
18 * rem rem=div => %o0 / %o1; rem=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 .rem
46.rem:
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 mov %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
103 bcc Lnot_too_big
104 add %g7, 1, %g7
105
106 ! We get here if the %o1 overflowed while shifting.
107 ! This means that %o3 has the high-order bit set.
108 ! Restore %o5 and subtract from %o3.
109 sll %g1, 4, %g1 ! high order bit
110 srl %o5, 1, %o5 ! rest of %o5
111 add %o5, %g1, %o5
112
113 b Ldo_single_div
114 sub %g7, 1, %g7
115
116 Lnot_too_big:
117 3:
118 cmp %o5, %o3
119 blu 2b
120 nop
121
122 be Ldo_single_div
123 nop
124 /* NB: these are commented out in the V8-Sparc manual as well */
125 /* (I do not understand this) */
126 ! %o5 > %o3: went too far: back up 1 step
127 ! srl %o5, 1, %o5
128 ! dec %g7
129 ! do single-bit divide steps
130 !
131 ! We have to be careful here. We know that %o3 >= %o5, so we can do the
132 ! first divide step without thinking. BUT, the others are conditional,
133 ! and are only done if %o3 >= 0. Because both %o3 and %o5 may have the high-
134 ! order bit set in the first step, just falling into the regular
135 ! division loop will mess up the first time around.
136 ! So we unroll slightly...
137 Ldo_single_div:
138 subcc %g7, 1, %g7
139 bl Lend_regular_divide
140 nop
141
142 sub %o3, %o5, %o3
143 mov 1, %o2
144
145 b Lend_single_divloop
146 nop
147 Lsingle_divloop:
148 sll %o2, 1, %o2
149
150 bl 1f
151 srl %o5, 1, %o5
152 ! %o3 >= 0
153 sub %o3, %o5, %o3
154
155 b 2f
156 add %o2, 1, %o2
157 1: ! %o3 < 0
158 add %o3, %o5, %o3
159 sub %o2, 1, %o2
160 2:
161 Lend_single_divloop:
162 subcc %g7, 1, %g7
163 bge Lsingle_divloop
164 tst %o3
165
166 b,a Lend_regular_divide
167
168Lnot_really_big:
1691:
170 sll %o5, 4, %o5
171 cmp %o5, %o3
172 bleu 1b
173 addcc %o4, 1, %o4
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
201 b 9f
202 add %o2, (7*2+1), %o2
203
204L.4.23:
205 ! remainder is negative
206 addcc %o3,%o5,%o3
207 b 9f
208 add %o2, (7*2-1), %o2
209
210L.3.19:
211 ! remainder is negative
212 addcc %o3,%o5,%o3
213 ! depth 4, accumulated bits 5
214 bl L.4.21
215 srl %o5,1,%o5
216 ! remainder is positive
217 subcc %o3,%o5,%o3
218 b 9f
219 add %o2, (5*2+1), %o2
220
221L.4.21:
222 ! remainder is negative
223 addcc %o3,%o5,%o3
224 b 9f
225 add %o2, (5*2-1), %o2
226
227L.2.17:
228 ! remainder is negative
229 addcc %o3,%o5,%o3
230 ! depth 3, accumulated bits 1
231 bl L.3.17
232 srl %o5,1,%o5
233 ! remainder is positive
234 subcc %o3,%o5,%o3
235 ! depth 4, accumulated bits 3
236 bl L.4.19
237 srl %o5,1,%o5
238 ! remainder is positive
239 subcc %o3,%o5,%o3
240 b 9f
241 add %o2, (3*2+1), %o2
242
243L.4.19:
244 ! remainder is negative
245 addcc %o3,%o5,%o3
246 b 9f
247 add %o2, (3*2-1), %o2
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
332
333L.3.13:
334 ! remainder is negative
335 addcc %o3,%o5,%o3
336 ! depth 4, accumulated bits -7
337 bl L.4.9
338 srl %o5,1,%o5
339 ! remainder is positive
340 subcc %o3,%o5,%o3
341 b 9f
342 add %o2, (-7*2+1), %o2
343
344L.4.9:
345 ! remainder is negative
346 addcc %o3,%o5,%o3
347 b 9f
348 add %o2, (-7*2-1), %o2
349
350 9:
351Lend_regular_divide:
352 subcc %o4, 1, %o4
353 bge Ldivloop
354 tst %o3
355
356 bl,a Lgot_result
357 ! non-restoring fixup here (one instruction only!)
358 add %o3, %o1, %o3
359
360Lgot_result:
361 ! check to see if answer should be < 0
362 tst %g2
363 bl,a 1f
364 sub %g0, %o3, %o3
3651:
366 retl
367 mov %o3, %o0
368
369 .globl .rem_patch
370.rem_patch:
371 sra %o0, 0x1f, %o4
372 wr %o4, 0x0, %y
373 nop
374 nop
375 nop
376 sdivcc %o0, %o1, %o2
377 bvs,a 1f
378 xnor %o2, %g0, %o2
3791: smul %o2, %o1, %o2
380 retl
381 sub %o0, %o2, %o0
382 nop