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.udiv:
47
48	! Ready to divide.  Compute size of quotient; scale comparand.
49	orcc	%o1, %g0, %o5
50	bne	1f
51	 mov	%o0, %o3
52
53		! Divide by zero trap.  If it returns, return 0 (about as
54		! wrong as possible, but that is what SunOS does...).
55		ta	ST_DIV0
56		retl
57		 clr	%o0
58
591:
60	cmp	%o3, %o5			! if %o1 exceeds %o0, done
61	blu	Lgot_result		! (and algorithm fails otherwise)
62	 clr	%o2
63
64	sethi	%hi(1 << (32 - 4 - 1)), %g1
65
66	cmp	%o3, %g1
67	blu	Lnot_really_big
68	 clr	%o4
69
70	! Here the dividend is >= 2**(31-N) or so.  We must be careful here,
71	! as our usual N-at-a-shot divide step will cause overflow and havoc.
72	! The number of bits in the result here is N*ITER+SC, where SC <= N.
73	! Compute ITER in an unorthodox manner: know we need to shift V into
74	! the top decade: so do not even bother to compare to R.
75	1:
76		cmp	%o5, %g1
77		bgeu	3f
78		 mov	1, %g7
79
80		sll	%o5, 4, %o5
81
82		b	1b
83		 add	%o4, 1, %o4
84
85	! Now compute %g7.
86	2:
87		addcc	%o5, %o5, %o5
88		bcc	Lnot_too_big
89		 add	%g7, 1, %g7
90
91		! We get here if the %o1 overflowed while shifting.
92		! This means that %o3 has the high-order bit set.
93		! Restore %o5 and subtract from %o3.
94		sll	%g1, 4, %g1	! high order bit
95		srl	%o5, 1, %o5		! rest of %o5
96		add	%o5, %g1, %o5
97
98		b	Ldo_single_div
99		 sub	%g7, 1, %g7
100
101	Lnot_too_big:
102	3:
103		cmp	%o5, %o3
104		blu	2b
105		 nop
106
107		be	Ldo_single_div
108		 nop
109	/* NB: these are commented out in the V8-Sparc manual as well */
110	/* (I do not understand this) */
111	! %o5 > %o3: went too far: back up 1 step
112	!	srl	%o5, 1, %o5
113	!	dec	%g7
114	! do single-bit divide steps
115	!
116	! We have to be careful here.  We know that %o3 >= %o5, so we can do the
117	! first divide step without thinking.  BUT, the others are conditional,
118	! and are only done if %o3 >= 0.  Because both %o3 and %o5 may have the high-
119	! order bit set in the first step, just falling into the regular
120	! division loop will mess up the first time around.
121	! So we unroll slightly...
122	Ldo_single_div:
123		subcc	%g7, 1, %g7
124		bl	Lend_regular_divide
125		 nop
126
127		sub	%o3, %o5, %o3
128		mov	1, %o2
129
130		b	Lend_single_divloop
131		 nop
132	Lsingle_divloop:
133		sll	%o2, 1, %o2
134		bl	1f
135		 srl	%o5, 1, %o5
136		! %o3 >= 0
137		sub	%o3, %o5, %o3
138		b	2f
139		 add	%o2, 1, %o2
140	1:	! %o3 < 0
141		add	%o3, %o5, %o3
142		sub	%o2, 1, %o2
143	2:
144	Lend_single_divloop:
145		subcc	%g7, 1, %g7
146		bge	Lsingle_divloop
147		 tst	%o3
148
149		b,a	Lend_regular_divide
150
151Lnot_really_big:
1521:
153	sll	%o5, 4, %o5
154
155	cmp	%o5, %o3
156	bleu	1b
157	 addcc	%o4, 1, %o4
158
159	be	Lgot_result
160	 sub	%o4, 1, %o4
161
162	tst	%o3	! set up for initial iteration
163Ldivloop:
164	sll	%o2, 4, %o2
165		! depth 1, accumulated bits 0
166	bl	L.1.16
167	 srl	%o5,1,%o5
168	! remainder is positive
169	subcc	%o3,%o5,%o3
170			! depth 2, accumulated bits 1
171	bl	L.2.17
172	 srl	%o5,1,%o5
173	! remainder is positive
174	subcc	%o3,%o5,%o3
175			! depth 3, accumulated bits 3
176	bl	L.3.19
177	 srl	%o5,1,%o5
178	! remainder is positive
179	subcc	%o3,%o5,%o3
180			! depth 4, accumulated bits 7
181	bl	L.4.23
182	 srl	%o5,1,%o5
183	! remainder is positive
184	subcc	%o3,%o5,%o3
185	b	9f
186	 add	%o2, (7*2+1), %o2
187
188L.4.23:
189	! remainder is negative
190	addcc	%o3,%o5,%o3
191	b	9f
192	 add	%o2, (7*2-1), %o2
193
194L.3.19:
195	! remainder is negative
196	addcc	%o3,%o5,%o3
197			! depth 4, accumulated bits 5
198	bl	L.4.21
199	 srl	%o5,1,%o5
200	! remainder is positive
201	subcc	%o3,%o5,%o3
202	b	9f
203	 add	%o2, (5*2+1), %o2
204
205L.4.21:
206	! remainder is negative
207	addcc	%o3,%o5,%o3
208	b	9f
209	 add	%o2, (5*2-1), %o2
210
211L.2.17:
212	! remainder is negative
213	addcc	%o3,%o5,%o3
214			! depth 3, accumulated bits 1
215	bl	L.3.17
216	 srl	%o5,1,%o5
217	! remainder is positive
218	subcc	%o3,%o5,%o3
219			! depth 4, accumulated bits 3
220	bl	L.4.19
221	 srl	%o5,1,%o5
222	! remainder is positive
223	subcc	%o3,%o5,%o3
224	b	9f
225	 add	%o2, (3*2+1), %o2
226
227L.4.19:
228	! remainder is negative
229	addcc	%o3,%o5,%o3
230	b	9f
231	 add	%o2, (3*2-1), %o2
232
233L.3.17:
234	! remainder is negative
235	addcc	%o3,%o5,%o3
236			! depth 4, accumulated bits 1
237	bl	L.4.17
238	 srl	%o5,1,%o5
239	! remainder is positive
240	subcc	%o3,%o5,%o3
241	b	9f
242	 add	%o2, (1*2+1), %o2
243
244L.4.17:
245	! remainder is negative
246	addcc	%o3,%o5,%o3
247	b	9f
248	 add	%o2, (1*2-1), %o2
249
250L.1.16:
251	! remainder is negative
252	addcc	%o3,%o5,%o3
253			! depth 2, accumulated bits -1
254	bl	L.2.15
255	 srl	%o5,1,%o5
256	! remainder is positive
257	subcc	%o3,%o5,%o3
258			! depth 3, accumulated bits -1
259	bl	L.3.15
260	 srl	%o5,1,%o5
261	! remainder is positive
262	subcc	%o3,%o5,%o3
263			! depth 4, accumulated bits -1
264	bl	L.4.15
265	 srl	%o5,1,%o5
266	! remainder is positive
267	subcc	%o3,%o5,%o3
268	b	9f
269	 add	%o2, (-1*2+1), %o2
270
271L.4.15:
272	! remainder is negative
273	addcc	%o3,%o5,%o3
274	b	9f
275	 add	%o2, (-1*2-1), %o2
276
277L.3.15:
278	! remainder is negative
279	addcc	%o3,%o5,%o3
280			! depth 4, accumulated bits -3
281	bl	L.4.13
282	 srl	%o5,1,%o5
283	! remainder is positive
284	subcc	%o3,%o5,%o3
285	b	9f
286	 add	%o2, (-3*2+1), %o2
287
288L.4.13:
289	! remainder is negative
290	addcc	%o3,%o5,%o3
291	b	9f
292	 add	%o2, (-3*2-1), %o2
293
294L.2.15:
295	! remainder is negative
296	addcc	%o3,%o5,%o3
297			! depth 3, accumulated bits -3
298	bl	L.3.13
299	 srl	%o5,1,%o5
300	! remainder is positive
301	subcc	%o3,%o5,%o3
302			! depth 4, accumulated bits -5
303	bl	L.4.11
304	 srl	%o5,1,%o5
305	! remainder is positive
306	subcc	%o3,%o5,%o3
307	b	9f
308	 add	%o2, (-5*2+1), %o2
309
310L.4.11:
311	! remainder is negative
312	addcc	%o3,%o5,%o3
313	b	9f
314	 add	%o2, (-5*2-1), %o2
315
316L.3.13:
317	! remainder is negative
318	addcc	%o3,%o5,%o3
319			! depth 4, accumulated bits -7
320	bl	L.4.9
321	 srl	%o5,1,%o5
322	! remainder is positive
323	subcc	%o3,%o5,%o3
324	b	9f
325	 add	%o2, (-7*2+1), %o2
326
327L.4.9:
328	! remainder is negative
329	addcc	%o3,%o5,%o3
330	b	9f
331	 add	%o2, (-7*2-1), %o2
332
333	9:
334Lend_regular_divide:
335	subcc	%o4, 1, %o4
336	bge	Ldivloop
337	 tst	%o3
338
339	bl,a	Lgot_result
340	! non-restoring fixup here (one instruction only!)
341	sub	%o2, 1, %o2
342
343Lgot_result:
344
345	retl
346	 mov %o2, %o0
347
348	.globl	.udiv_patch
349.udiv_patch:
350	wr	%g0, 0x0, %y
351	nop
352	nop
353	retl
354	 udiv	%o0, %o1, %o0
355	nop
356