altHashing.cpp revision 4527:6f817ce50129 
1/*
2 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
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23 */
24
25#include "precompiled.hpp"
26#include "classfile/altHashing.hpp"
27#include "classfile/symbolTable.hpp"
28#include "classfile/systemDictionary.hpp"
29#include "oops/markOop.hpp"
30#include "runtime/thread.hpp"
31
32// Get the hash code of the classes mirror if it exists, otherwise just
33// return a random number, which is one of the possible hash code used for
34// objects.  We don't want to call the synchronizer hash code to install
35// this value because it may safepoint.
36intptr_t object_hash(Klass* k) {
37  intptr_t hc = k->java_mirror()->mark()->hash();
38  return hc != markOopDesc::no_hash ? hc : os::random();
39}
40
41// Seed value used for each alternative hash calculated.
42jint AltHashing::compute_seed() {
43  jlong nanos = os::javaTimeNanos();
44  jlong now = os::javaTimeMillis();
45  jint SEED_MATERIAL[8] = {
46            (jint) object_hash(SystemDictionary::String_klass()),
47            (jint) object_hash(SystemDictionary::System_klass()),
48            (jint) os::random(),  // current thread isn't a java thread
49            (jint) (((julong)nanos) >> 32),
50            (jint) nanos,
51            (jint) (((julong)now) >> 32),
52            (jint) now,
53            (jint) (os::javaTimeNanos() >> 2)
54  };
55
56  return murmur3_32(SEED_MATERIAL, 8);
57}
58
59
60// Murmur3 hashing for Symbol
61jint AltHashing::murmur3_32(jint seed, const jbyte* data, int len) {
62  jint h1 = seed;
63  int count = len;
64  int offset = 0;
65
66  // body
67  while (count >= 4) {
68    jint k1 = (data[offset] & 0x0FF)
69        | (data[offset + 1] & 0x0FF) << 8
70        | (data[offset + 2] & 0x0FF) << 16
71        | data[offset + 3] << 24;
72
73    count -= 4;
74    offset += 4;
75
76    k1 *= 0xcc9e2d51;
77    k1 = Integer_rotateLeft(k1, 15);
78    k1 *= 0x1b873593;
79
80    h1 ^= k1;
81    h1 = Integer_rotateLeft(h1, 13);
82    h1 = h1 * 5 + 0xe6546b64;
83  }
84
85  // tail
86
87  if (count > 0) {
88    jint k1 = 0;
89
90    switch (count) {
91      case 3:
92        k1 ^= (data[offset + 2] & 0xff) << 16;
93      // fall through
94      case 2:
95        k1 ^= (data[offset + 1] & 0xff) << 8;
96      // fall through
97      case 1:
98        k1 ^= (data[offset] & 0xff);
99      // fall through
100      default:
101        k1 *= 0xcc9e2d51;
102        k1 = Integer_rotateLeft(k1, 15);
103        k1 *= 0x1b873593;
104        h1 ^= k1;
105    }
106  }
107
108  // finalization
109  h1 ^= len;
110
111  // finalization mix force all bits of a hash block to avalanche
112  h1 ^= ((unsigned int)h1) >> 16;
113  h1 *= 0x85ebca6b;
114  h1 ^= ((unsigned int)h1) >> 13;
115  h1 *= 0xc2b2ae35;
116  h1 ^= ((unsigned int)h1) >> 16;
117
118  return h1;
119}
120
121// Murmur3 hashing for Strings
122jint AltHashing::murmur3_32(jint seed, const jchar* data, int len) {
123  jint h1 = seed;
124
125  int off = 0;
126  int count = len;
127
128  // body
129  while (count >= 2) {
130    jchar d1 = data[off++] & 0xFFFF;
131    jchar d2 = data[off++];
132    jint k1 = (d1 | d2 << 16);
133
134    count -= 2;
135
136    k1 *= 0xcc9e2d51;
137    k1 = Integer_rotateLeft(k1, 15);
138    k1 *= 0x1b873593;
139
140    h1 ^= k1;
141    h1 = Integer_rotateLeft(h1, 13);
142    h1 = h1 * 5 + 0xe6546b64;
143  }
144
145  // tail
146
147  if (count > 0) {
148    int k1 = data[off];
149
150    k1 *= 0xcc9e2d51;
151    k1 = Integer_rotateLeft(k1, 15);
152    k1 *= 0x1b873593;
153    h1 ^= k1;
154  }
155
156  // finalization
157  h1 ^= len * 2; // (Character.SIZE / Byte.SIZE);
158
159  // finalization mix force all bits of a hash block to avalanche
160  h1 ^= ((unsigned int)h1) >> 16;
161  h1 *= 0x85ebca6b;
162  h1 ^= ((unsigned int)h1) >> 13;
163  h1 *= 0xc2b2ae35;
164  h1 ^= ((unsigned int)h1) >> 16;
165
166  return h1;
167}
168
169// Hash used for the seed.
170jint AltHashing::murmur3_32(jint seed, const int* data, int len) {
171  jint h1 = seed;
172
173  int off = 0;
174  int end = len;
175
176  // body
177  while (off < end) {
178    jint k1 = data[off++];
179
180    k1 *= 0xcc9e2d51;
181    k1 = Integer_rotateLeft(k1, 15);
182    k1 *= 0x1b873593;
183
184    h1 ^= k1;
185    h1 = Integer_rotateLeft(h1, 13);
186    h1 = h1 * 5 + 0xe6546b64;
187  }
188
189  // tail (always empty, as body is always 32-bit chunks)
190
191  // finalization
192
193  h1 ^= len * 4; // (Integer.SIZE / Byte.SIZE);
194
195  // finalization mix force all bits of a hash block to avalanche
196  h1 ^= ((juint)h1) >> 16;
197  h1 *= 0x85ebca6b;
198  h1 ^= ((juint)h1) >> 13;
199  h1 *= 0xc2b2ae35;
200  h1 ^= ((juint)h1) >> 16;
201
202  return h1;
203}
204
205jint AltHashing::murmur3_32(const int* data, int len) {
206  return murmur3_32(0, data, len);
207}
208
209#ifndef PRODUCT
210// Overloaded versions for internal test.
211jint AltHashing::murmur3_32(const jbyte* data, int len) {
212  return murmur3_32(0, data, len);
213}
214
215jint AltHashing::murmur3_32(const jchar* data, int len) {
216  return murmur3_32(0, data, len);
217}
218
219// Internal test for alternate hashing.  Translated from JDK version
220// test/sun/misc/Hashing.java
221static const jbyte ONE_BYTE[] = { (jbyte) 0x80};
222static const jbyte TWO_BYTE[] = { (jbyte) 0x80, (jbyte) 0x81};
223static const jchar ONE_CHAR[] = { (jchar) 0x8180};
224static const jbyte THREE_BYTE[] = { (jbyte) 0x80, (jbyte) 0x81, (jbyte) 0x82};
225static const jbyte FOUR_BYTE[] = { (jbyte) 0x80, (jbyte) 0x81, (jbyte) 0x82, (jbyte) 0x83};
226static const jchar TWO_CHAR[] = { (jchar) 0x8180, (jchar) 0x8382};
227static const jint ONE_INT[] = { 0x83828180};
228static const jbyte SIX_BYTE[] = { (jbyte) 0x80, (jbyte) 0x81, (jbyte) 0x82, (jbyte) 0x83, (jbyte) 0x84, (jbyte) 0x85};
229static const jchar THREE_CHAR[] = { (jchar) 0x8180, (jchar) 0x8382, (jchar) 0x8584};
230static const jbyte EIGHT_BYTE[] = {
231  (jbyte) 0x80, (jbyte) 0x81, (jbyte) 0x82,
232  (jbyte) 0x83, (jbyte) 0x84, (jbyte) 0x85,
233  (jbyte) 0x86, (jbyte) 0x87};
234static const jchar FOUR_CHAR[] = {
235  (jchar) 0x8180, (jchar) 0x8382,
236  (jchar) 0x8584, (jchar) 0x8786};
237
238static const jint TWO_INT[] = { 0x83828180, 0x87868584};
239
240static const juint MURMUR3_32_X86_CHECK_VALUE = 0xB0F57EE3;
241
242void AltHashing::testMurmur3_32_ByteArray() {
243  // printf("testMurmur3_32_ByteArray\n");
244
245  jbyte vector[256];
246  jbyte hashes[4 * 256];
247
248  for (int i = 0; i < 256; i++) {
249    vector[i] = (jbyte) i;
250  }
251
252  // Hash subranges {}, {0}, {0,1}, {0,1,2}, ..., {0,...,255}
253  for (int i = 0; i < 256; i++) {
254    jint hash = murmur3_32(256 - i, vector, i);
255    hashes[i * 4] = (jbyte) hash;
256    hashes[i * 4 + 1] = (jbyte) (((juint)hash) >> 8);
257    hashes[i * 4 + 2] = (jbyte) (((juint)hash) >> 16);
258    hashes[i * 4 + 3] = (jbyte) (((juint)hash) >> 24);
259  }
260
261  // hash to get const result.
262  juint final_hash = murmur3_32(hashes, 4*256);
263
264  assert (MURMUR3_32_X86_CHECK_VALUE == final_hash,
265    err_msg(
266        "Calculated hash result not as expected. Expected %08X got %08X\n",
267        MURMUR3_32_X86_CHECK_VALUE,
268        final_hash));
269}
270
271void AltHashing::testEquivalentHashes() {
272  jint jbytes, jchars, ints;
273
274  // printf("testEquivalentHashes\n");
275
276  jbytes = murmur3_32(TWO_BYTE, 2);
277  jchars = murmur3_32(ONE_CHAR, 1);
278  assert (jbytes == jchars,
279    err_msg("Hashes did not match. b:%08x != c:%08x\n", jbytes, jchars));
280
281  jbytes = murmur3_32(FOUR_BYTE, 4);
282  jchars = murmur3_32(TWO_CHAR, 2);
283  ints = murmur3_32(ONE_INT, 1);
284  assert ((jbytes == jchars) && (jbytes == ints),
285    err_msg("Hashes did not match. b:%08x != c:%08x != i:%08x\n", jbytes, jchars, ints));
286
287  jbytes = murmur3_32(SIX_BYTE, 6);
288  jchars = murmur3_32(THREE_CHAR, 3);
289  assert (jbytes == jchars,
290    err_msg("Hashes did not match. b:%08x != c:%08x\n", jbytes, jchars));
291
292  jbytes = murmur3_32(EIGHT_BYTE, 8);
293  jchars = murmur3_32(FOUR_CHAR, 4);
294  ints = murmur3_32(TWO_INT, 2);
295  assert ((jbytes == jchars) && (jbytes == ints),
296    err_msg("Hashes did not match. b:%08x != c:%08x != i:%08x\n", jbytes, jchars, ints));
297}
298
299// Returns true if the alternate hashcode is correct
300void AltHashing::test_alt_hash() {
301  testMurmur3_32_ByteArray();
302  testEquivalentHashes();
303}
304#endif // PRODUCT
305