Mercurial > hg > CbC > CbC_gcc
comparison libquadmath/printf/divrem.c @ 68:561a7518be6b
update gcc-4.6
author | Nobuyasu Oshiro <dimolto@cr.ie.u-ryukyu.ac.jp> |
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date | Sun, 21 Aug 2011 07:07:55 +0900 |
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67:f6334be47118 | 68:561a7518be6b |
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1 /* mpn_divrem -- Divide natural numbers, producing both remainder and | |
2 quotient. | |
3 | |
4 Copyright (C) 1993, 1994, 1995, 1996 Free Software Foundation, Inc. | |
5 | |
6 This file is part of the GNU MP Library. | |
7 | |
8 The GNU MP Library is free software; you can redistribute it and/or modify | |
9 it under the terms of the GNU Lesser General Public License as published by | |
10 the Free Software Foundation; either version 2.1 of the License, or (at your | |
11 option) any later version. | |
12 | |
13 The GNU MP Library is distributed in the hope that it will be useful, but | |
14 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY | |
15 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public | |
16 License for more details. | |
17 | |
18 You should have received a copy of the GNU Lesser General Public License | |
19 along with the GNU MP Library; see the file COPYING.LIB. If not, write to | |
20 the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, | |
21 MA 02111-1307, USA. */ | |
22 | |
23 #include <config.h> | |
24 #include "gmp-impl.h" | |
25 | |
26 /* Divide num (NP/NSIZE) by den (DP/DSIZE) and write | |
27 the NSIZE-DSIZE least significant quotient limbs at QP | |
28 and the DSIZE long remainder at NP. If QEXTRA_LIMBS is | |
29 non-zero, generate that many fraction bits and append them after the | |
30 other quotient limbs. | |
31 Return the most significant limb of the quotient, this is always 0 or 1. | |
32 | |
33 Preconditions: | |
34 0. NSIZE >= DSIZE. | |
35 1. The most significant bit of the divisor must be set. | |
36 2. QP must either not overlap with the input operands at all, or | |
37 QP + DSIZE >= NP must hold true. (This means that it's | |
38 possible to put the quotient in the high part of NUM, right after the | |
39 remainder in NUM. | |
40 3. NSIZE >= DSIZE, even if QEXTRA_LIMBS is non-zero. */ | |
41 | |
42 mp_limb_t | |
43 #if __STDC__ | |
44 mpn_divrem (mp_ptr qp, mp_size_t qextra_limbs, | |
45 mp_ptr np, mp_size_t nsize, | |
46 mp_srcptr dp, mp_size_t dsize) | |
47 #else | |
48 mpn_divrem (qp, qextra_limbs, np, nsize, dp, dsize) | |
49 mp_ptr qp; | |
50 mp_size_t qextra_limbs; | |
51 mp_ptr np; | |
52 mp_size_t nsize; | |
53 mp_srcptr dp; | |
54 mp_size_t dsize; | |
55 #endif | |
56 { | |
57 mp_limb_t most_significant_q_limb = 0; | |
58 | |
59 switch (dsize) | |
60 { | |
61 case 0: | |
62 /* We are asked to divide by zero, so go ahead and do it! (To make | |
63 the compiler not remove this statement, return the value.) */ | |
64 return 1 / dsize; | |
65 | |
66 case 1: | |
67 { | |
68 mp_size_t i; | |
69 mp_limb_t n1; | |
70 mp_limb_t d; | |
71 | |
72 d = dp[0]; | |
73 n1 = np[nsize - 1]; | |
74 | |
75 if (n1 >= d) | |
76 { | |
77 n1 -= d; | |
78 most_significant_q_limb = 1; | |
79 } | |
80 | |
81 qp += qextra_limbs; | |
82 for (i = nsize - 2; i >= 0; i--) | |
83 udiv_qrnnd (qp[i], n1, n1, np[i], d); | |
84 qp -= qextra_limbs; | |
85 | |
86 for (i = qextra_limbs - 1; i >= 0; i--) | |
87 udiv_qrnnd (qp[i], n1, n1, 0, d); | |
88 | |
89 np[0] = n1; | |
90 } | |
91 break; | |
92 | |
93 case 2: | |
94 { | |
95 mp_size_t i; | |
96 mp_limb_t n1, n0, n2; | |
97 mp_limb_t d1, d0; | |
98 | |
99 np += nsize - 2; | |
100 d1 = dp[1]; | |
101 d0 = dp[0]; | |
102 n1 = np[1]; | |
103 n0 = np[0]; | |
104 | |
105 if (n1 >= d1 && (n1 > d1 || n0 >= d0)) | |
106 { | |
107 sub_ddmmss (n1, n0, n1, n0, d1, d0); | |
108 most_significant_q_limb = 1; | |
109 } | |
110 | |
111 for (i = qextra_limbs + nsize - 2 - 1; i >= 0; i--) | |
112 { | |
113 mp_limb_t q; | |
114 mp_limb_t r; | |
115 | |
116 if (i >= qextra_limbs) | |
117 np--; | |
118 else | |
119 np[0] = 0; | |
120 | |
121 if (n1 == d1) | |
122 { | |
123 /* Q should be either 111..111 or 111..110. Need special | |
124 treatment of this rare case as normal division would | |
125 give overflow. */ | |
126 q = ~(mp_limb_t) 0; | |
127 | |
128 r = n0 + d1; | |
129 if (r < d1) /* Carry in the addition? */ | |
130 { | |
131 add_ssaaaa (n1, n0, r - d0, np[0], 0, d0); | |
132 qp[i] = q; | |
133 continue; | |
134 } | |
135 n1 = d0 - (d0 != 0); | |
136 n0 = -d0; | |
137 } | |
138 else | |
139 { | |
140 udiv_qrnnd (q, r, n1, n0, d1); | |
141 umul_ppmm (n1, n0, d0, q); | |
142 } | |
143 | |
144 n2 = np[0]; | |
145 q_test: | |
146 if (n1 > r || (n1 == r && n0 > n2)) | |
147 { | |
148 /* The estimated Q was too large. */ | |
149 q--; | |
150 | |
151 sub_ddmmss (n1, n0, n1, n0, 0, d0); | |
152 r += d1; | |
153 if (r >= d1) /* If not carry, test Q again. */ | |
154 goto q_test; | |
155 } | |
156 | |
157 qp[i] = q; | |
158 sub_ddmmss (n1, n0, r, n2, n1, n0); | |
159 } | |
160 np[1] = n1; | |
161 np[0] = n0; | |
162 } | |
163 break; | |
164 | |
165 default: | |
166 { | |
167 mp_size_t i; | |
168 mp_limb_t dX, d1, n0; | |
169 | |
170 np += nsize - dsize; | |
171 dX = dp[dsize - 1]; | |
172 d1 = dp[dsize - 2]; | |
173 n0 = np[dsize - 1]; | |
174 | |
175 if (n0 >= dX) | |
176 { | |
177 if (n0 > dX || mpn_cmp (np, dp, dsize - 1) >= 0) | |
178 { | |
179 mpn_sub_n (np, np, dp, dsize); | |
180 n0 = np[dsize - 1]; | |
181 most_significant_q_limb = 1; | |
182 } | |
183 } | |
184 | |
185 for (i = qextra_limbs + nsize - dsize - 1; i >= 0; i--) | |
186 { | |
187 mp_limb_t q; | |
188 mp_limb_t n1, n2; | |
189 mp_limb_t cy_limb; | |
190 | |
191 if (i >= qextra_limbs) | |
192 { | |
193 np--; | |
194 n2 = np[dsize]; | |
195 } | |
196 else | |
197 { | |
198 n2 = np[dsize - 1]; | |
199 MPN_COPY_DECR (np + 1, np, dsize); | |
200 np[0] = 0; | |
201 } | |
202 | |
203 if (n0 == dX) | |
204 /* This might over-estimate q, but it's probably not worth | |
205 the extra code here to find out. */ | |
206 q = ~(mp_limb_t) 0; | |
207 else | |
208 { | |
209 mp_limb_t r; | |
210 | |
211 udiv_qrnnd (q, r, n0, np[dsize - 1], dX); | |
212 umul_ppmm (n1, n0, d1, q); | |
213 | |
214 while (n1 > r || (n1 == r && n0 > np[dsize - 2])) | |
215 { | |
216 q--; | |
217 r += dX; | |
218 if (r < dX) /* I.e. "carry in previous addition?" */ | |
219 break; | |
220 n1 -= n0 < d1; | |
221 n0 -= d1; | |
222 } | |
223 } | |
224 | |
225 /* Possible optimization: We already have (q * n0) and (1 * n1) | |
226 after the calculation of q. Taking advantage of that, we | |
227 could make this loop make two iterations less. */ | |
228 | |
229 cy_limb = mpn_submul_1 (np, dp, dsize, q); | |
230 | |
231 if (n2 != cy_limb) | |
232 { | |
233 mpn_add_n (np, np, dp, dsize); | |
234 q--; | |
235 } | |
236 | |
237 qp[i] = q; | |
238 n0 = np[dsize - 1]; | |
239 } | |
240 } | |
241 } | |
242 | |
243 return most_significant_q_limb; | |
244 } |