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
383