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src/hotspot/share/classfile/altHashing.cpp

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  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.
  36 static intptr_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.
  42 juint AltHashing::compute_seed() {
  43   jlong nanos = os::javaTimeNanos();
  44   jlong now = os::javaTimeMillis();
  45   int SEED_MATERIAL[8] = {
  46             (int) object_hash(SystemDictionary::String_klass()),
  47             (int) object_hash(SystemDictionary::System_klass()),
  48             os::random(),  // current thread isn't a java thread
  49             (int) (((julong)nanos) >> 32),
  50             (int) nanos,
  51             (int) (((julong)now) >> 32),
  52             (int) now,
  53             (int) (os::javaTimeNanos() >> 2)
  54   };
  55 
  56   return murmur3_32(SEED_MATERIAL, 8);
  57 }
  58 
  59 
  60 // Murmur3 hashing for Symbol
  61 juint AltHashing::murmur3_32(juint seed, const jbyte* data, int len) {
  62   juint h1 = seed;
  63   int count = len;
  64   int offset = 0;
  65 
  66   // body
  67   while (count >= 4) {
  68     juint 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;


 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 ^= h1 >> 16;
 161   h1 *= 0x85ebca6b;
 162   h1 ^= h1 >> 13;
 163   h1 *= 0xc2b2ae35;
 164   h1 ^= h1 >> 16;
 165 
 166   return h1;
 167 }
 168 
 169 // Hash used for the seed.
 170 juint AltHashing::murmur3_32(juint seed, const int* data, int len) {
 171   juint h1 = seed;
 172 
 173   int off = 0;
 174   int end = len;
 175 
 176   // body
 177   while (off < end) {
 178     juint k1 = (juint)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 ^= h1 >> 16;
 197   h1 *= 0x85ebca6b;
 198   h1 ^= h1 >> 13;
 199   h1 *= 0xc2b2ae35;
 200   h1 ^= h1 >> 16;
 201 
 202   return h1;
 203 }
 204 
 205 juint AltHashing::murmur3_32(const int* data, int len) {
 206   return murmur3_32(0, data, len);
 207 }


  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.
  36 static intptr_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.
  42 juint 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
  61 juint AltHashing::murmur3_32(juint seed, const jbyte* data, int len) {
  62   juint h1 = seed;
  63   int count = len;
  64   int offset = 0;
  65 
  66   // body
  67   while (count >= 4) {
  68     juint 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;


 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 ^= h1 >> 16;
 161   h1 *= 0x85ebca6b;
 162   h1 ^= h1 >> 13;
 163   h1 *= 0xc2b2ae35;
 164   h1 ^= h1 >> 16;
 165 
 166   return h1;
 167 }
 168 
 169 // Hash used for the seed.
 170 juint AltHashing::murmur3_32(juint seed, const jint* data, int len) {
 171   juint h1 = seed;
 172 
 173   int off = 0;
 174   int end = len;
 175 
 176   // body
 177   while (off < end) {
 178     juint k1 = (juint)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 ^= h1 >> 16;
 197   h1 *= 0x85ebca6b;
 198   h1 ^= h1 >> 13;
 199   h1 *= 0xc2b2ae35;
 200   h1 ^= h1 >> 16;
 201 
 202   return h1;
 203 }
 204 
 205 juint AltHashing::murmur3_32(const jint* data, int len) {
 206   return murmur3_32(0, data, len);
 207 }
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