1/* $Id: sdiv.S,v 1.1.1.1 2007-08-03 18:52:17 $
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	.globl _Div
47.div:
48_Div:	/* 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	 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
382