1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2 /* ***** BEGIN LICENSE BLOCK *****
3 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
4 *
5 * The contents of this file are subject to the Mozilla Public License Version
6 * 1.1 (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 * http://www.mozilla.org/MPL/
9 *
10 * Software distributed under the License is distributed on an "AS IS" basis,
11 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
12 * for the specific language governing rights and limitations under the
13 * License.
14 *
15 * The Original Code is Mozilla Communicator client code, released
16 * March 31, 1998.
17 *
18 * The Initial Developer of the Original Code is
19 * Netscape Communications Corporation.
20 * Portions created by the Initial Developer are Copyright (C) 1998
21 * the Initial Developer. All Rights Reserved.
22 *
23 * Contributor(s):
24 *
25 * Alternatively, the contents of this file may be used under the terms of
26 * either of the GNU General Public License Version 2 or later (the "GPL"),
27 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
28 * in which case the provisions of the GPL or the LGPL are applicable instead
29 * of those above. If you wish to allow use of your version of this file only
30 * under the terms of either the GPL or the LGPL, and not to allow others to
31 * use your version of this file under the terms of the MPL, indicate your
32 * decision by deleting the provisions above and replace them with the notice
33 * and other provisions required by the GPL or the LGPL. If you do not delete
34 * the provisions above, a recipient may use your version of this file under
35 * the terms of any one of the MPL, the GPL or the LGPL.
36 *
37 * ***** END LICENSE BLOCK ***** */
38
39 #include "jsstddef.h"
40 #include "jstypes.h"
41 #include "jslong.h"
42
43 static JSInt64 ll_zero = JSLL_INIT( 0x00000000,0x00000000 );
44 static JSInt64 ll_maxint = JSLL_INIT( 0x7fffffff, 0xffffffff );
45 static JSInt64 ll_minint = JSLL_INIT( 0x80000000, 0x00000000 );
46
47 #ifdef HAVE_WATCOM_BUG_2
48 JSInt64 __pascal __loadds __export
JSLL_Zero(void)49 JSLL_Zero(void) { return ll_zero; }
50 JSInt64 __pascal __loadds __export
JSLL_MaxInt(void)51 JSLL_MaxInt(void) { return ll_maxint; }
52 JSInt64 __pascal __loadds __export
JSLL_MinInt(void)53 JSLL_MinInt(void) { return ll_minint; }
54 #else
JSLL_Zero(void)55 JS_PUBLIC_API(JSInt64) JSLL_Zero(void) { return ll_zero; }
JSLL_MaxInt(void)56 JS_PUBLIC_API(JSInt64) JSLL_MaxInt(void) { return ll_maxint; }
JSLL_MinInt(void)57 JS_PUBLIC_API(JSInt64) JSLL_MinInt(void) { return ll_minint; }
58 #endif
59
60 #ifndef JS_HAVE_LONG_LONG
61 /*
62 ** Divide 64-bit a by 32-bit b, which must be normalized so its high bit is 1.
63 */
norm_udivmod32(JSUint32 * qp,JSUint32 * rp,JSUint64 a,JSUint32 b)64 static void norm_udivmod32(JSUint32 *qp, JSUint32 *rp, JSUint64 a, JSUint32 b)
65 {
66 JSUint32 d1, d0, q1, q0;
67 JSUint32 r1, r0, m;
68
69 d1 = jshi16(b);
70 d0 = jslo16(b);
71 r1 = a.hi % d1;
72 q1 = a.hi / d1;
73 m = q1 * d0;
74 r1 = (r1 << 16) | jshi16(a.lo);
75 if (r1 < m) {
76 q1--, r1 += b;
77 if (r1 >= b /* i.e., we didn't get a carry when adding to r1 */
78 && r1 < m) {
79 q1--, r1 += b;
80 }
81 }
82 r1 -= m;
83 r0 = r1 % d1;
84 q0 = r1 / d1;
85 m = q0 * d0;
86 r0 = (r0 << 16) | jslo16(a.lo);
87 if (r0 < m) {
88 q0--, r0 += b;
89 if (r0 >= b
90 && r0 < m) {
91 q0--, r0 += b;
92 }
93 }
94 *qp = (q1 << 16) | q0;
95 *rp = r0 - m;
96 }
97
CountLeadingZeros(JSUint32 a)98 static JSUint32 CountLeadingZeros(JSUint32 a)
99 {
100 JSUint32 t;
101 JSUint32 r = 32;
102
103 if ((t = a >> 16) != 0)
104 r -= 16, a = t;
105 if ((t = a >> 8) != 0)
106 r -= 8, a = t;
107 if ((t = a >> 4) != 0)
108 r -= 4, a = t;
109 if ((t = a >> 2) != 0)
110 r -= 2, a = t;
111 if ((t = a >> 1) != 0)
112 r -= 1, a = t;
113 if (a & 1)
114 r--;
115 return r;
116 }
117
jsll_udivmod(JSUint64 * qp,JSUint64 * rp,JSUint64 a,JSUint64 b)118 JS_PUBLIC_API(void) jsll_udivmod(JSUint64 *qp, JSUint64 *rp, JSUint64 a, JSUint64 b)
119 {
120 JSUint32 n0, n1, n2;
121 JSUint32 q0, q1;
122 JSUint32 rsh, lsh;
123
124 n0 = a.lo;
125 n1 = a.hi;
126
127 if (b.hi == 0) {
128 if (b.lo > n1) {
129 /* (0 q0) = (n1 n0) / (0 D0) */
130
131 lsh = CountLeadingZeros(b.lo);
132
133 if (lsh) {
134 /*
135 * Normalize, i.e. make the most significant bit of the
136 * denominator be set.
137 */
138 b.lo = b.lo << lsh;
139 n1 = (n1 << lsh) | (n0 >> (32 - lsh));
140 n0 = n0 << lsh;
141 }
142
143 a.lo = n0, a.hi = n1;
144 norm_udivmod32(&q0, &n0, a, b.lo);
145 q1 = 0;
146
147 /* remainder is in n0 >> lsh */
148 } else {
149 /* (q1 q0) = (n1 n0) / (0 d0) */
150
151 if (b.lo == 0) /* user wants to divide by zero! */
152 b.lo = 1 / b.lo; /* so go ahead and crash */
153
154 lsh = CountLeadingZeros(b.lo);
155
156 if (lsh == 0) {
157 /*
158 * From (n1 >= b.lo)
159 * && (the most significant bit of b.lo is set),
160 * conclude that
161 * (the most significant bit of n1 is set)
162 * && (the leading quotient digit q1 = 1).
163 *
164 * This special case is necessary, not an optimization
165 * (Shifts counts of 32 are undefined).
166 */
167 n1 -= b.lo;
168 q1 = 1;
169 } else {
170 /*
171 * Normalize.
172 */
173 rsh = 32 - lsh;
174
175 b.lo = b.lo << lsh;
176 n2 = n1 >> rsh;
177 n1 = (n1 << lsh) | (n0 >> rsh);
178 n0 = n0 << lsh;
179
180 a.lo = n1, a.hi = n2;
181 norm_udivmod32(&q1, &n1, a, b.lo);
182 }
183
184 /* n1 != b.lo... */
185
186 a.lo = n0, a.hi = n1;
187 norm_udivmod32(&q0, &n0, a, b.lo);
188
189 /* remainder in n0 >> lsh */
190 }
191
192 if (rp) {
193 rp->lo = n0 >> lsh;
194 rp->hi = 0;
195 }
196 } else {
197 if (b.hi > n1) {
198 /* (0 0) = (n1 n0) / (D1 d0) */
199
200 q0 = 0;
201 q1 = 0;
202
203 /* remainder in (n1 n0) */
204 if (rp) {
205 rp->lo = n0;
206 rp->hi = n1;
207 }
208 } else {
209 /* (0 q0) = (n1 n0) / (d1 d0) */
210
211 lsh = CountLeadingZeros(b.hi);
212 if (lsh == 0) {
213 /*
214 * From (n1 >= b.hi)
215 * && (the most significant bit of b.hi is set),
216 * conclude that
217 * (the most significant bit of n1 is set)
218 * && (the quotient digit q0 = 0 or 1).
219 *
220 * This special case is necessary, not an optimization.
221 */
222
223 /*
224 * The condition on the next line takes advantage of that
225 * n1 >= b.hi (true due to control flow).
226 */
227 if (n1 > b.hi || n0 >= b.lo) {
228 q0 = 1;
229 a.lo = n0, a.hi = n1;
230 JSLL_SUB(a, a, b);
231 } else {
232 q0 = 0;
233 }
234 q1 = 0;
235
236 if (rp) {
237 rp->lo = n0;
238 rp->hi = n1;
239 }
240 } else {
241 JSInt64 m;
242
243 /*
244 * Normalize.
245 */
246 rsh = 32 - lsh;
247
248 b.hi = (b.hi << lsh) | (b.lo >> rsh);
249 b.lo = b.lo << lsh;
250 n2 = n1 >> rsh;
251 n1 = (n1 << lsh) | (n0 >> rsh);
252 n0 = n0 << lsh;
253
254 a.lo = n1, a.hi = n2;
255 norm_udivmod32(&q0, &n1, a, b.hi);
256 JSLL_MUL32(m, q0, b.lo);
257
258 if ((m.hi > n1) || ((m.hi == n1) && (m.lo > n0))) {
259 q0--;
260 JSLL_SUB(m, m, b);
261 }
262
263 q1 = 0;
264
265 /* Remainder is ((n1 n0) - (m1 m0)) >> lsh */
266 if (rp) {
267 a.lo = n0, a.hi = n1;
268 JSLL_SUB(a, a, m);
269 rp->lo = (a.hi << rsh) | (a.lo >> lsh);
270 rp->hi = a.hi >> lsh;
271 }
272 }
273 }
274 }
275
276 if (qp) {
277 qp->lo = q0;
278 qp->hi = q1;
279 }
280 }
281 #endif /* !JS_HAVE_LONG_LONG */
282