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1.1 root 1: /* $Id: udiv.S,v 1.4 1996/09/30 02:22:38 davem Exp $
2: * udiv.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: * .udiv name of function to generate
18: * div div=div => %o0 / %o1; div=rem => %o0 % %o1
19: * false false=true => signed; false=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 .udiv
46: .globl _Udiv
47: .udiv:
48: _Udiv: /* needed for export */
49:
50: ! Ready to divide. Compute size of quotient; scale comparand.
51: orcc %o1, %g0, %o5
52: bne 1f
53: mov %o0, %o3
54:
55: ! Divide by zero trap. If it returns, return 0 (about as
56: ! wrong as possible, but that is what SunOS does...).
57: ta 0x2
58: retl
59: clr %o0
60:
61: 1:
62: cmp %o3, %o5 ! if %o1 exceeds %o0, done
63: blu Lgot_result ! (and algorithm fails otherwise)
64: clr %o2
65:
66: sethi %hi(1 << (32 - 4 - 1)), %g1
67:
68: cmp %o3, %g1
69: blu Lnot_really_big
70: clr %o4
71:
72: ! Here the dividend is >= 2**(31-N) or so. We must be careful here,
73: ! as our usual N-at-a-shot divide step will cause overflow and havoc.
74: ! The number of bits in the result here is N*ITER+SC, where SC <= N.
75: ! Compute ITER in an unorthodox manner: know we need to shift V into
76: ! the top decade: so do not even bother to compare to R.
77: 1:
78: cmp %o5, %g1
79: bgeu 3f
80: mov 1, %g7
81:
82: sll %o5, 4, %o5
83:
84: b 1b
85: add %o4, 1, %o4
86:
87: ! Now compute %g7.
88: 2:
89: addcc %o5, %o5, %o5
90: bcc Lnot_too_big
91: add %g7, 1, %g7
92:
93: ! We get here if the %o1 overflowed while shifting.
94: ! This means that %o3 has the high-order bit set.
95: ! Restore %o5 and subtract from %o3.
96: sll %g1, 4, %g1 ! high order bit
97: srl %o5, 1, %o5 ! rest of %o5
98: add %o5, %g1, %o5
99:
100: b Ldo_single_div
101: sub %g7, 1, %g7
102:
103: Lnot_too_big:
104: 3:
105: cmp %o5, %o3
106: blu 2b
107: nop
108:
109: be Ldo_single_div
110: nop
111: /* NB: these are commented out in the V8-Sparc manual as well */
112: /* (I do not understand this) */
113: ! %o5 > %o3: went too far: back up 1 step
114: ! srl %o5, 1, %o5
115: ! dec %g7
116: ! do single-bit divide steps
117: !
118: ! We have to be careful here. We know that %o3 >= %o5, so we can do the
119: ! first divide step without thinking. BUT, the others are conditional,
120: ! and are only done if %o3 >= 0. Because both %o3 and %o5 may have the high-
121: ! order bit set in the first step, just falling into the regular
122: ! division loop will mess up the first time around.
123: ! So we unroll slightly...
124: Ldo_single_div:
125: subcc %g7, 1, %g7
126: bl Lend_regular_divide
127: nop
128:
129: sub %o3, %o5, %o3
130: mov 1, %o2
131:
132: b Lend_single_divloop
133: nop
134: Lsingle_divloop:
135: sll %o2, 1, %o2
136: bl 1f
137: srl %o5, 1, %o5
138: ! %o3 >= 0
139: sub %o3, %o5, %o3
140: b 2f
141: add %o2, 1, %o2
142: 1: ! %o3 < 0
143: add %o3, %o5, %o3
144: sub %o2, 1, %o2
145: 2:
146: Lend_single_divloop:
147: subcc %g7, 1, %g7
148: bge Lsingle_divloop
149: tst %o3
150:
151: b,a Lend_regular_divide
152:
153: Lnot_really_big:
154: 1:
155: sll %o5, 4, %o5
156:
157: cmp %o5, %o3
158: bleu 1b
159: addcc %o4, 1, %o4
160:
161: be Lgot_result
162: sub %o4, 1, %o4
163:
164: tst %o3 ! set up for initial iteration
165: Ldivloop:
166: sll %o2, 4, %o2
167: ! depth 1, accumulated bits 0
168: bl L.1.16
169: srl %o5,1,%o5
170: ! remainder is positive
171: subcc %o3,%o5,%o3
172: ! depth 2, accumulated bits 1
173: bl L.2.17
174: srl %o5,1,%o5
175: ! remainder is positive
176: subcc %o3,%o5,%o3
177: ! depth 3, accumulated bits 3
178: bl L.3.19
179: srl %o5,1,%o5
180: ! remainder is positive
181: subcc %o3,%o5,%o3
182: ! depth 4, accumulated bits 7
183: bl L.4.23
184: srl %o5,1,%o5
185: ! remainder is positive
186: subcc %o3,%o5,%o3
187: b 9f
188: add %o2, (7*2+1), %o2
189:
190: L.4.23:
191: ! remainder is negative
192: addcc %o3,%o5,%o3
193: b 9f
194: add %o2, (7*2-1), %o2
195:
196: L.3.19:
197: ! remainder is negative
198: addcc %o3,%o5,%o3
199: ! depth 4, accumulated bits 5
200: bl L.4.21
201: srl %o5,1,%o5
202: ! remainder is positive
203: subcc %o3,%o5,%o3
204: b 9f
205: add %o2, (5*2+1), %o2
206:
207: L.4.21:
208: ! remainder is negative
209: addcc %o3,%o5,%o3
210: b 9f
211: add %o2, (5*2-1), %o2
212:
213: L.2.17:
214: ! remainder is negative
215: addcc %o3,%o5,%o3
216: ! depth 3, accumulated bits 1
217: bl L.3.17
218: srl %o5,1,%o5
219: ! remainder is positive
220: subcc %o3,%o5,%o3
221: ! depth 4, accumulated bits 3
222: bl L.4.19
223: srl %o5,1,%o5
224: ! remainder is positive
225: subcc %o3,%o5,%o3
226: b 9f
227: add %o2, (3*2+1), %o2
228:
229: L.4.19:
230: ! remainder is negative
231: addcc %o3,%o5,%o3
232: b 9f
233: add %o2, (3*2-1), %o2
234:
235: L.3.17:
236: ! remainder is negative
237: addcc %o3,%o5,%o3
238: ! depth 4, accumulated bits 1
239: bl L.4.17
240: srl %o5,1,%o5
241: ! remainder is positive
242: subcc %o3,%o5,%o3
243: b 9f
244: add %o2, (1*2+1), %o2
245:
246: L.4.17:
247: ! remainder is negative
248: addcc %o3,%o5,%o3
249: b 9f
250: add %o2, (1*2-1), %o2
251:
252: L.1.16:
253: ! remainder is negative
254: addcc %o3,%o5,%o3
255: ! depth 2, accumulated bits -1
256: bl L.2.15
257: srl %o5,1,%o5
258: ! remainder is positive
259: subcc %o3,%o5,%o3
260: ! depth 3, accumulated bits -1
261: bl L.3.15
262: srl %o5,1,%o5
263: ! remainder is positive
264: subcc %o3,%o5,%o3
265: ! depth 4, accumulated bits -1
266: bl L.4.15
267: srl %o5,1,%o5
268: ! remainder is positive
269: subcc %o3,%o5,%o3
270: b 9f
271: add %o2, (-1*2+1), %o2
272:
273: L.4.15:
274: ! remainder is negative
275: addcc %o3,%o5,%o3
276: b 9f
277: add %o2, (-1*2-1), %o2
278:
279: L.3.15:
280: ! remainder is negative
281: addcc %o3,%o5,%o3
282: ! depth 4, accumulated bits -3
283: bl L.4.13
284: srl %o5,1,%o5
285: ! remainder is positive
286: subcc %o3,%o5,%o3
287: b 9f
288: add %o2, (-3*2+1), %o2
289:
290: L.4.13:
291: ! remainder is negative
292: addcc %o3,%o5,%o3
293: b 9f
294: add %o2, (-3*2-1), %o2
295:
296: L.2.15:
297: ! remainder is negative
298: addcc %o3,%o5,%o3
299: ! depth 3, accumulated bits -3
300: bl L.3.13
301: srl %o5,1,%o5
302: ! remainder is positive
303: subcc %o3,%o5,%o3
304: ! depth 4, accumulated bits -5
305: bl L.4.11
306: srl %o5,1,%o5
307: ! remainder is positive
308: subcc %o3,%o5,%o3
309: b 9f
310: add %o2, (-5*2+1), %o2
311:
312: L.4.11:
313: ! remainder is negative
314: addcc %o3,%o5,%o3
315: b 9f
316: add %o2, (-5*2-1), %o2
317:
318: L.3.13:
319: ! remainder is negative
320: addcc %o3,%o5,%o3
321: ! depth 4, accumulated bits -7
322: bl L.4.9
323: srl %o5,1,%o5
324: ! remainder is positive
325: subcc %o3,%o5,%o3
326: b 9f
327: add %o2, (-7*2+1), %o2
328:
329: L.4.9:
330: ! remainder is negative
331: addcc %o3,%o5,%o3
332: b 9f
333: add %o2, (-7*2-1), %o2
334:
335: 9:
336: Lend_regular_divide:
337: subcc %o4, 1, %o4
338: bge Ldivloop
339: tst %o3
340:
341: bl,a Lgot_result
342: ! non-restoring fixup here (one instruction only!)
343: sub %o2, 1, %o2
344:
345: Lgot_result:
346:
347: retl
348: mov %o2, %o0
349:
350: .globl .udiv_patch
351: .udiv_patch:
352: wr %g0, 0x0, %y
353: nop
354: nop
355: retl
356: udiv %o0, %o1, %o0
357: nop
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