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1 | /* |
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 | .globl _Rem |
47 | .rem: |
48 | _Rem: /* needed for export */ |
49 | ! 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 | mov %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 |
60 | 1: ! %o0 is negative, %o1 is nonnegative |
61 | sub %g0, %o0, %o0 ! make %o0 nonnegative |
62 | 2: |
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 | |
75 | 1: |
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 | |
105 | bcc Lnot_too_big |
106 | add %g7, 1, %g7 |
107 | |
108 | ! We get here if the %o1 overflowed while shifting. |
109 | ! This means that %o3 has the high-order bit set. |
110 | ! Restore %o5 and subtract from %o3. |
111 | sll %g1, 4, %g1 ! high order bit |
112 | srl %o5, 1, %o5 ! rest of %o5 |
113 | add %o5, %g1, %o5 |
114 | |
115 | b Ldo_single_div |
116 | sub %g7, 1, %g7 |
117 | |
118 | Lnot_too_big: |
119 | 3: |
120 | cmp %o5, %o3 |
121 | blu 2b |
122 | nop |
123 | |
124 | be Ldo_single_div |
125 | nop |
126 | /* NB: these are commented out in the V8-Sparc manual as well */ |
127 | /* (I do not understand this) */ |
128 | ! %o5 > %o3: went too far: back up 1 step |
129 | ! srl %o5, 1, %o5 |
130 | ! dec %g7 |
131 | ! do single-bit divide steps |
132 | ! |
133 | ! We have to be careful here. We know that %o3 >= %o5, so we can do the |
134 | ! first divide step without thinking. BUT, the others are conditional, |
135 | ! and are only done if %o3 >= 0. Because both %o3 and %o5 may have the high- |
136 | ! order bit set in the first step, just falling into the regular |
137 | ! division loop will mess up the first time around. |
138 | ! So we unroll slightly... |
139 | Ldo_single_div: |
140 | subcc %g7, 1, %g7 |
141 | bl Lend_regular_divide |
142 | nop |
143 | |
144 | sub %o3, %o5, %o3 |
145 | mov 1, %o2 |
146 | |
147 | b Lend_single_divloop |
148 | nop |
149 | Lsingle_divloop: |
150 | sll %o2, 1, %o2 |
151 | |
152 | bl 1f |
153 | srl %o5, 1, %o5 |
154 | ! %o3 >= 0 |
155 | sub %o3, %o5, %o3 |
156 | |
157 | b 2f |
158 | add %o2, 1, %o2 |
159 | 1: ! %o3 < 0 |
160 | add %o3, %o5, %o3 |
161 | sub %o2, 1, %o2 |
162 | 2: |
163 | Lend_single_divloop: |
164 | subcc %g7, 1, %g7 |
165 | bge Lsingle_divloop |
166 | tst %o3 |
167 | |
168 | b,a Lend_regular_divide |
169 | |
170 | Lnot_really_big: |
171 | 1: |
172 | sll %o5, 4, %o5 |
173 | cmp %o5, %o3 |
174 | bleu 1b |
175 | addcc %o4, 1, %o4 |
176 | be Lgot_result |
177 | sub %o4, 1, %o4 |
178 | |
179 | tst %o3 ! set up for initial iteration |
180 | Ldivloop: |
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 | |
203 | b 9f |
204 | add %o2, (7*2+1), %o2 |
205 | |
206 | L.4.23: |
207 | ! remainder is negative |
208 | addcc %o3,%o5,%o3 |
209 | b 9f |
210 | add %o2, (7*2-1), %o2 |
211 | |
212 | L.3.19: |
213 | ! remainder is negative |
214 | addcc %o3,%o5,%o3 |
215 | ! depth 4, accumulated bits 5 |
216 | bl L.4.21 |
217 | srl %o5,1,%o5 |
218 | ! remainder is positive |
219 | subcc %o3,%o5,%o3 |
220 | b 9f |
221 | add %o2, (5*2+1), %o2 |
222 | |
223 | L.4.21: |
224 | ! remainder is negative |
225 | addcc %o3,%o5,%o3 |
226 | b 9f |
227 | add %o2, (5*2-1), %o2 |
228 | |
229 | L.2.17: |
230 | ! remainder is negative |
231 | addcc %o3,%o5,%o3 |
232 | ! depth 3, accumulated bits 1 |
233 | bl L.3.17 |
234 | srl %o5,1,%o5 |
235 | ! remainder is positive |
236 | subcc %o3,%o5,%o3 |
237 | ! depth 4, accumulated bits 3 |
238 | bl L.4.19 |
239 | srl %o5,1,%o5 |
240 | ! remainder is positive |
241 | subcc %o3,%o5,%o3 |
242 | b 9f |
243 | add %o2, (3*2+1), %o2 |
244 | |
245 | L.4.19: |
246 | ! remainder is negative |
247 | addcc %o3,%o5,%o3 |
248 | b 9f |
249 | add %o2, (3*2-1), %o2 |
250 | |
251 | L.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 | |
262 | L.4.17: |
263 | ! remainder is negative |
264 | addcc %o3,%o5,%o3 |
265 | b 9f |
266 | add %o2, (1*2-1), %o2 |
267 | |
268 | L.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 | |
289 | L.4.15: |
290 | ! remainder is negative |
291 | addcc %o3,%o5,%o3 |
292 | b 9f |
293 | add %o2, (-1*2-1), %o2 |
294 | |
295 | L.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 | |
306 | L.4.13: |
307 | ! remainder is negative |
308 | addcc %o3,%o5,%o3 |
309 | b 9f |
310 | add %o2, (-3*2-1), %o2 |
311 | |
312 | L.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 | |
328 | L.4.11: |
329 | ! remainder is negative |
330 | addcc %o3,%o5,%o3 |
331 | b 9f |
332 | add %o2, (-5*2-1), %o2 |
333 | |
334 | |
335 | L.3.13: |
336 | ! remainder is negative |
337 | addcc %o3,%o5,%o3 |
338 | ! depth 4, accumulated bits -7 |
339 | bl L.4.9 |
340 | srl %o5,1,%o5 |
341 | ! remainder is positive |
342 | subcc %o3,%o5,%o3 |
343 | b 9f |
344 | add %o2, (-7*2+1), %o2 |
345 | |
346 | L.4.9: |
347 | ! remainder is negative |
348 | addcc %o3,%o5,%o3 |
349 | b 9f |
350 | add %o2, (-7*2-1), %o2 |
351 | |
352 | 9: |
353 | Lend_regular_divide: |
354 | subcc %o4, 1, %o4 |
355 | bge Ldivloop |
356 | tst %o3 |
357 | |
358 | bl,a Lgot_result |
359 | ! non-restoring fixup here (one instruction only!) |
360 | add %o3, %o1, %o3 |
361 | |
362 | Lgot_result: |
363 | ! check to see if answer should be < 0 |
364 | tst %g2 |
365 | bl,a 1f |
366 | sub %g0, %o3, %o3 |
367 | 1: |
368 | retl |
369 | mov %o3, %o0 |
370 | |
371 | .globl .rem_patch |
372 | .rem_patch: |
373 | sra %o0, 0x1f, %o4 |
374 | wr %o4, 0x0, %y |
375 | nop |
376 | nop |
377 | nop |
378 | sdivcc %o0, %o1, %o2 |
379 | bvs,a 1f |
380 | xnor %o2, %g0, %o2 |
381 | 1: smul %o2, %o1, %o2 |
382 | retl |
383 | sub %o0, %o2, %o0 |
384 | nop |
385 |
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