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/* $Id: udiv.S,v 1.1 2005-12-20 09:50:47 jcastillo Exp $
 * udiv.S:      This routine was taken from glibc-1.09 and is covered
 *              by the GNU Library General Public License Version 2.
 */
 
 
/* This file is generated from divrem.m4; DO NOT EDIT! */
/*
 * Division and remainder, from Appendix E of the Sparc Version 8
 * Architecture Manual, with fixes from Gordon Irlam.
 */
 
/*
 * Input: dividend and divisor in %o0 and %o1 respectively.
 *
 * m4 parameters:
 *  .udiv       name of function to generate
 *  div         div=div => %o0 / %o1; div=rem => %o0 % %o1
 *  false               false=true => signed; false=false => unsigned
 *
 * Algorithm parameters:
 *  N           how many bits per iteration we try to get (4)
 *  WORDSIZE    total number of bits (32)
 *
 * Derived constants:
 *  TOPBITS     number of bits in the top decade of a number
 *
 * Important variables:
 *  Q           the partial quotient under development (initially 0)
 *  R           the remainder so far, initially the dividend
 *  ITER        number of main division loop iterations required;
 *              equal to ceil(log2(quotient) / N).  Note that this
 *              is the log base (2^N) of the quotient.
 *  V           the current comparand, initially divisor*2^(ITER*N-1)
 *
 * Cost:
 *  Current estimate for non-large dividend is
 *      ceil(log2(quotient) / N) * (10 + 7N/2) + C
 *  A large dividend is one greater than 2^(31-TOPBITS) and takes a
 *  different path, as the upper bits of the quotient must be developed
 *  one bit at a time.
 */
 
 
        .globl .udiv
.udiv:
 
        ! Ready to divide.  Compute size of quotient; scale comparand.
        orcc    %o1, %g0, %o5
        bne     1f
        mov     %o0, %o3
 
                ! Divide by zero trap.  If it returns, return 0 (about as
                ! wrong as possible, but that is what SunOS does...).
                ta      ST_DIV0
                retl
                clr     %o0
 
1:
        cmp     %o3, %o5                        ! if %o1 exceeds %o0, done
        blu     Lgot_result             ! (and algorithm fails otherwise)
        clr     %o2
        sethi   %hi(1 << (32 - 4 - 1)), %g1
        cmp     %o3, %g1
        blu     Lnot_really_big
        clr     %o4
 
        ! Here the dividend is >= 2**(31-N) or so.  We must be careful here,
        ! as our usual N-at-a-shot divide step will cause overflow and havoc.
        ! The number of bits in the result here is N*ITER+SC, where SC <= N.
        ! Compute ITER in an unorthodox manner: know we need to shift V into
        ! the top decade: so do not even bother to compare to R.
        1:
                cmp     %o5, %g1
                bgeu    3f
                mov     1, %g7
                sll     %o5, 4, %o5
                b       1b
                add     %o4, 1, %o4
 
        ! Now compute %g7.
        2:      addcc   %o5, %o5, %o5
                bcc     Lnot_too_big
                add     %g7, 1, %g7
 
                ! We get here if the %o1 overflowed while shifting.
                ! This means that %o3 has the high-order bit set.
                ! Restore %o5 and subtract from %o3.
                sll     %g1, 4, %g1     ! high order bit
                srl     %o5, 1, %o5             ! rest of %o5
                add     %o5, %g1, %o5
                b       Ldo_single_div
                sub     %g7, 1, %g7
 
        Lnot_too_big:
        3:      cmp     %o5, %o3
                blu     2b
                nop
                be      Ldo_single_div
                nop
        /* NB: these are commented out in the V8-Sparc manual as well */
        /* (I do not understand this) */
        ! %o5 > %o3: went too far: back up 1 step
        !       srl     %o5, 1, %o5
        !       dec     %g7
        ! do single-bit divide steps
        !
        ! We have to be careful here.  We know that %o3 >= %o5, so we can do the
        ! first divide step without thinking.  BUT, the others are conditional,
        ! and are only done if %o3 >= 0.  Because both %o3 and %o5 may have the high-
        ! order bit set in the first step, just falling into the regular
        ! division loop will mess up the first time around.
        ! So we unroll slightly...
        Ldo_single_div:
                subcc   %g7, 1, %g7
                bl      Lend_regular_divide
                nop
                sub     %o3, %o5, %o3
                mov     1, %o2
                b       Lend_single_divloop
                nop
        Lsingle_divloop:
                sll     %o2, 1, %o2
                bl      1f
                srl     %o5, 1, %o5
                ! %o3 >= 0
                sub     %o3, %o5, %o3
                b       2f
                add     %o2, 1, %o2
        1:      ! %o3 < 0
                add     %o3, %o5, %o3
                sub     %o2, 1, %o2
        2:
        Lend_single_divloop:
                subcc   %g7, 1, %g7
                bge     Lsingle_divloop
                tst     %o3
                b,a     Lend_regular_divide
 
Lnot_really_big:
1:
        sll     %o5, 4, %o5
        cmp     %o5, %o3
        bleu    1b
        addcc   %o4, 1, %o4
        be      Lgot_result
        sub     %o4, 1, %o4
 
        tst     %o3     ! set up for initial iteration
Ldivloop:
        sll     %o2, 4, %o2
                ! depth 1, accumulated bits 0
        bl      L.1.16
        srl     %o5,1,%o5
        ! remainder is positive
        subcc   %o3,%o5,%o3
                        ! depth 2, accumulated bits 1
        bl      L.2.17
        srl     %o5,1,%o5
        ! remainder is positive
        subcc   %o3,%o5,%o3
                        ! depth 3, accumulated bits 3
        bl      L.3.19
        srl     %o5,1,%o5
        ! remainder is positive
        subcc   %o3,%o5,%o3
                        ! depth 4, accumulated bits 7
        bl      L.4.23
        srl     %o5,1,%o5
        ! remainder is positive
        subcc   %o3,%o5,%o3
                b       9f
                add     %o2, (7*2+1), %o2
 
L.4.23:
        ! remainder is negative
        addcc   %o3,%o5,%o3
                b       9f
                add     %o2, (7*2-1), %o2
 
 
L.3.19:
        ! remainder is negative
        addcc   %o3,%o5,%o3
                        ! depth 4, accumulated bits 5
        bl      L.4.21
        srl     %o5,1,%o5
        ! remainder is positive
        subcc   %o3,%o5,%o3
                b       9f
                add     %o2, (5*2+1), %o2
 
L.4.21:
        ! remainder is negative
        addcc   %o3,%o5,%o3
                b       9f
                add     %o2, (5*2-1), %o2
 
 
 
L.2.17:
        ! remainder is negative
        addcc   %o3,%o5,%o3
                        ! depth 3, accumulated bits 1
        bl      L.3.17
        srl     %o5,1,%o5
        ! remainder is positive
        subcc   %o3,%o5,%o3
                        ! depth 4, accumulated bits 3
        bl      L.4.19
        srl     %o5,1,%o5
        ! remainder is positive
        subcc   %o3,%o5,%o3
                b       9f
                add     %o2, (3*2+1), %o2
 
L.4.19:
        ! remainder is negative
        addcc   %o3,%o5,%o3
                b       9f
                add     %o2, (3*2-1), %o2
 
 
L.3.17:
        ! remainder is negative
        addcc   %o3,%o5,%o3
                        ! depth 4, accumulated bits 1
        bl      L.4.17
        srl     %o5,1,%o5
        ! remainder is positive
        subcc   %o3,%o5,%o3
                b       9f
                add     %o2, (1*2+1), %o2
 
L.4.17:
        ! remainder is negative
        addcc   %o3,%o5,%o3
                b       9f
                add     %o2, (1*2-1), %o2
 
 
 
 
L.1.16:
        ! remainder is negative
        addcc   %o3,%o5,%o3
                        ! depth 2, accumulated bits -1
        bl      L.2.15
        srl     %o5,1,%o5
        ! remainder is positive
        subcc   %o3,%o5,%o3
                        ! depth 3, accumulated bits -1
        bl      L.3.15
        srl     %o5,1,%o5
        ! remainder is positive
        subcc   %o3,%o5,%o3
                        ! depth 4, accumulated bits -1
        bl      L.4.15
        srl     %o5,1,%o5
        ! remainder is positive
        subcc   %o3,%o5,%o3
                b       9f
                add     %o2, (-1*2+1), %o2
 
L.4.15:
        ! remainder is negative
        addcc   %o3,%o5,%o3
                b       9f
                add     %o2, (-1*2-1), %o2
 
 
L.3.15:
        ! remainder is negative
        addcc   %o3,%o5,%o3
                        ! depth 4, accumulated bits -3
        bl      L.4.13
        srl     %o5,1,%o5
        ! remainder is positive
        subcc   %o3,%o5,%o3
                b       9f
                add     %o2, (-3*2+1), %o2
 
L.4.13:
        ! remainder is negative
        addcc   %o3,%o5,%o3
                b       9f
                add     %o2, (-3*2-1), %o2
 
 
 
L.2.15:
        ! remainder is negative
        addcc   %o3,%o5,%o3
                        ! depth 3, accumulated bits -3
        bl      L.3.13
        srl     %o5,1,%o5
        ! remainder is positive
        subcc   %o3,%o5,%o3
                        ! depth 4, accumulated bits -5
        bl      L.4.11
        srl     %o5,1,%o5
        ! remainder is positive
        subcc   %o3,%o5,%o3
                b       9f
                add     %o2, (-5*2+1), %o2
 
L.4.11:
        ! remainder is negative
        addcc   %o3,%o5,%o3
                b       9f
                add     %o2, (-5*2-1), %o2
 
 
L.3.13:
        ! remainder is negative
        addcc   %o3,%o5,%o3
                        ! depth 4, accumulated bits -7
        bl      L.4.9
        srl     %o5,1,%o5
        ! remainder is positive
        subcc   %o3,%o5,%o3
                b       9f
                add     %o2, (-7*2+1), %o2
 
L.4.9:
        ! remainder is negative
        addcc   %o3,%o5,%o3
                b       9f
                add     %o2, (-7*2-1), %o2
 
 
 
 
        9:
Lend_regular_divide:
        subcc   %o4, 1, %o4
        bge     Ldivloop
        tst     %o3
        bl,a    Lgot_result
        ! non-restoring fixup here (one instruction only!)
        sub     %o2, 1, %o2
 
 
Lgot_result:
 
        retl
        mov %o2, %o0

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[/] [or1k_old/] [trunk/] [rc203soc/] [sw/] [uClinux/] [arch/] [sparc/] [lib/] [udiv.S] - Blame information for rev 1765

Line No.	Rev	Author	Line
1	1624	jcastillo	`/* $Id: udiv.S,v 1.1 2005-12-20 09:50:47 jcastillo 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 divisor2^(ITERN-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
59			`1:`
60			`cmp %o3, %o5 ! if %o1 exceeds %o0, done`
61			`blu Lgot_result ! (and algorithm fails otherwise)`
62			`clr %o2`
63			`sethi %hi(1 << (32 - 4 - 1)), %g1`
64			`cmp %o3, %g1`
65			`blu Lnot_really_big`
66			`clr %o4`
67
68			`! Here the dividend is >= 2**(31-N) or so. We must be careful here,`
69			`! as our usual N-at-a-shot divide step will cause overflow and havoc.`
70			`! The number of bits in the result here is N*ITER+SC, where SC <= N.`
71			`! Compute ITER in an unorthodox manner: know we need to shift V into`
72			`! the top decade: so do not even bother to compare to R.`
73			`1:`
74			`cmp %o5, %g1`
75			`bgeu 3f`
76			`mov 1, %g7`
77			`sll %o5, 4, %o5`
78			`b 1b`
79			`add %o4, 1, %o4`
80
81			`! Now compute %g7.`
82			`2: addcc %o5, %o5, %o5`
83			`bcc Lnot_too_big`
84			`add %g7, 1, %g7`
85
86			`! We get here if the %o1 overflowed while shifting.`
87			`! This means that %o3 has the high-order bit set.`
88			`! Restore %o5 and subtract from %o3.`
89			`sll %g1, 4, %g1 ! high order bit`
90			`srl %o5, 1, %o5 ! rest of %o5`
91			`add %o5, %g1, %o5`
92			`b Ldo_single_div`
93			`sub %g7, 1, %g7`
94
95			`Lnot_too_big:`
96			`3: cmp %o5, %o3`
97			`blu 2b`
98			`nop`
99			`be Ldo_single_div`
100			`nop`
101			`/* NB: these are commented out in the V8-Sparc manual as well */`
102			`/* (I do not understand this) */`
103			`! %o5 > %o3: went too far: back up 1 step`
104			`! srl %o5, 1, %o5`
105			`! dec %g7`
106			`! do single-bit divide steps`
107			`!`
108			`! We have to be careful here. We know that %o3 >= %o5, so we can do the`
109			`! first divide step without thinking. BUT, the others are conditional,`
110			`! and are only done if %o3 >= 0. Because both %o3 and %o5 may have the high-`
111			`! order bit set in the first step, just falling into the regular`
112			`! division loop will mess up the first time around.`
113			`! So we unroll slightly...`
114			`Ldo_single_div:`
115			`subcc %g7, 1, %g7`
116			`bl Lend_regular_divide`
117			`nop`
118			`sub %o3, %o5, %o3`
119			`mov 1, %o2`
120			`b Lend_single_divloop`
121			`nop`
122			`Lsingle_divloop:`
123			`sll %o2, 1, %o2`
124			`bl 1f`
125			`srl %o5, 1, %o5`
126			`! %o3 >= 0`
127			`sub %o3, %o5, %o3`
128			`b 2f`
129			`add %o2, 1, %o2`
130			`1: ! %o3 < 0`
131			`add %o3, %o5, %o3`
132			`sub %o2, 1, %o2`
133			`2:`
134			`Lend_single_divloop:`
135			`subcc %g7, 1, %g7`
136			`bge Lsingle_divloop`
137			`tst %o3`
138			`b,a Lend_regular_divide`
139
140			`Lnot_really_big:`
141			`1:`
142			`sll %o5, 4, %o5`
143			`cmp %o5, %o3`
144			`bleu 1b`
145			`addcc %o4, 1, %o4`
146			`be Lgot_result`
147			`sub %o4, 1, %o4`
148
149			`tst %o3 ! set up for initial iteration`
150			`Ldivloop:`
151			`sll %o2, 4, %o2`
152			`! depth 1, accumulated bits 0`
153			`bl L.1.16`
154			`srl %o5,1,%o5`
155			`! remainder is positive`
156			`subcc %o3,%o5,%o3`
157			`! depth 2, accumulated bits 1`
158			`bl L.2.17`
159			`srl %o5,1,%o5`
160			`! remainder is positive`
161			`subcc %o3,%o5,%o3`
162			`! depth 3, accumulated bits 3`
163			`bl L.3.19`
164			`srl %o5,1,%o5`
165			`! remainder is positive`
166			`subcc %o3,%o5,%o3`
167			`! depth 4, accumulated bits 7`
168			`bl L.4.23`
169			`srl %o5,1,%o5`
170			`! remainder is positive`
171			`subcc %o3,%o5,%o3`
172			`b 9f`
173			`add %o2, (7*2+1), %o2`
174
175			`L.4.23:`
176			`! remainder is negative`
177			`addcc %o3,%o5,%o3`
178			`b 9f`
179			`add %o2, (7*2-1), %o2`
180
181
182			`L.3.19:`
183			`! remainder is negative`
184			`addcc %o3,%o5,%o3`
185			`! depth 4, accumulated bits 5`
186			`bl L.4.21`
187			`srl %o5,1,%o5`
188			`! remainder is positive`
189			`subcc %o3,%o5,%o3`
190			`b 9f`
191			`add %o2, (5*2+1), %o2`
192
193			`L.4.21:`
194			`! remainder is negative`
195			`addcc %o3,%o5,%o3`
196			`b 9f`
197			`add %o2, (5*2-1), %o2`
198
199
200
201			`L.2.17:`
202			`! remainder is negative`
203			`addcc %o3,%o5,%o3`
204			`! depth 3, accumulated bits 1`
205			`bl L.3.17`
206			`srl %o5,1,%o5`
207			`! remainder is positive`
208			`subcc %o3,%o5,%o3`
209			`! depth 4, accumulated bits 3`
210			`bl L.4.19`
211			`srl %o5,1,%o5`
212			`! remainder is positive`
213			`subcc %o3,%o5,%o3`
214			`b 9f`
215			`add %o2, (3*2+1), %o2`
216
217			`L.4.19:`
218			`! remainder is negative`
219			`addcc %o3,%o5,%o3`
220			`b 9f`
221			`add %o2, (3*2-1), %o2`
222
223
224			`L.3.17:`
225			`! remainder is negative`
226			`addcc %o3,%o5,%o3`
227			`! depth 4, accumulated bits 1`
228			`bl L.4.17`
229			`srl %o5,1,%o5`
230			`! remainder is positive`
231			`subcc %o3,%o5,%o3`
232			`b 9f`
233			`add %o2, (1*2+1), %o2`
234
235			`L.4.17:`
236			`! remainder is negative`
237			`addcc %o3,%o5,%o3`
238			`b 9f`
239			`add %o2, (1*2-1), %o2`
240
241
242
243
244			`L.1.16:`
245			`! remainder is negative`
246			`addcc %o3,%o5,%o3`
247			`! depth 2, accumulated bits -1`
248			`bl L.2.15`
249			`srl %o5,1,%o5`
250			`! remainder is positive`
251			`subcc %o3,%o5,%o3`
252			`! depth 3, accumulated bits -1`
253			`bl L.3.15`
254			`srl %o5,1,%o5`
255			`! remainder is positive`
256			`subcc %o3,%o5,%o3`
257			`! depth 4, accumulated bits -1`
258			`bl L.4.15`
259			`srl %o5,1,%o5`
260			`! remainder is positive`
261			`subcc %o3,%o5,%o3`
262			`b 9f`
263			`add %o2, (-1*2+1), %o2`
264
265			`L.4.15:`
266			`! remainder is negative`
267			`addcc %o3,%o5,%o3`
268			`b 9f`
269			`add %o2, (-1*2-1), %o2`
270
271
272			`L.3.15:`
273			`! remainder is negative`
274			`addcc %o3,%o5,%o3`
275			`! depth 4, accumulated bits -3`
276			`bl L.4.13`
277			`srl %o5,1,%o5`
278			`! remainder is positive`
279			`subcc %o3,%o5,%o3`
280			`b 9f`
281			`add %o2, (-3*2+1), %o2`
282
283			`L.4.13:`
284			`! remainder is negative`
285			`addcc %o3,%o5,%o3`
286			`b 9f`
287			`add %o2, (-3*2-1), %o2`
288
289
290
291			`L.2.15:`
292			`! remainder is negative`
293			`addcc %o3,%o5,%o3`
294			`! depth 3, accumulated bits -3`
295			`bl L.3.13`
296			`srl %o5,1,%o5`
297			`! remainder is positive`
298			`subcc %o3,%o5,%o3`
299			`! depth 4, accumulated bits -5`
300			`bl L.4.11`
301			`srl %o5,1,%o5`
302			`! remainder is positive`
303			`subcc %o3,%o5,%o3`
304			`b 9f`
305			`add %o2, (-5*2+1), %o2`
306
307			`L.4.11:`
308			`! remainder is negative`
309			`addcc %o3,%o5,%o3`
310			`b 9f`
311			`add %o2, (-5*2-1), %o2`
312
313
314			`L.3.13:`
315			`! remainder is negative`
316			`addcc %o3,%o5,%o3`
317			`! depth 4, accumulated bits -7`
318			`bl L.4.9`
319			`srl %o5,1,%o5`
320			`! remainder is positive`
321			`subcc %o3,%o5,%o3`
322			`b 9f`
323			`add %o2, (-7*2+1), %o2`
324
325			`L.4.9:`
326			`! remainder is negative`
327			`addcc %o3,%o5,%o3`
328			`b 9f`
329			`add %o2, (-7*2-1), %o2`
330
331
332
333
334			`9:`
335			`Lend_regular_divide:`
336			`subcc %o4, 1, %o4`
337			`bge Ldivloop`
338			`tst %o3`
339			`bl,a Lgot_result`
340			`! non-restoring fixup here (one instruction only!)`
341			`sub %o2, 1, %o2`
342
343
344			`Lgot_result:`
345
346			`retl`
347			`mov %o2, %o0`