[objects] seed NumberDictionary (only ia32 now)

src/ia32/macro-assembler-ia32.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 966 matching lines @@
   // r0 - holds the untagged key on entry and holds the hash once computed.
   //
   // r1 - used to hold the capacity mask of the dictionary
   //
   // r2 - used for the index into the dictionary.
   //
   // result - holds the result on exit if the load succeeds and we fall through.
 
   Label done;
 
+  // First of all lets assign to r1 value of HashSeed

[Erik Corry, 2012/01/10 10:13:51]

"First of all we assign the hash seed to r1."

+  if (Serializer::enabled()) {
+    ExternalReference roots_array_start =
+        ExternalReference::roots_array_start(isolate());
+    mov(r1, Immediate(Heap::kStringHashSeedRootIndex));
+    mov(r1, Operand::StaticArray(r1,
+                                 times_pointer_size,
+                                 roots_array_start));
+  } else {
+    int32_t seed = isolate()->heap()->StringHashSeed();
+    mov(r1, Operand(seed, RelocInfo::NONE));
+  }
+
+  // Xor original key with a seed
+  xor_(r1, r0);
+
   // Compute the hash code from the untagged key.  This must be kept in sync
   // with ComputeIntegerHash in utils.h.
   //
   // hash = ~hash + (hash << 15);
-  mov(r1, r0);
   not_(r0);

[Erik Corry, 2012/01/10 10:13:51]

The intention is that the original should be xored with the seed, but here r0 is
input unchanged into the algorithm.  In the next line half of the seed is thrown
away.

   shl(r1, 15);
   add(r0, r1);
   // hash = hash ^ (hash >> 12);
   mov(r1, r0);
   shr(r1, 12);
   xor_(r0, r1);
   // hash = hash + (hash << 2);
   lea(r0, Operand(r0, r0, times_4, 0));
   // hash = hash ^ (hash >> 4);
   mov(r1, r0);
@@ skipping 1682 matching lines @@
     cmp(length, Operand(bitmap_scratch, MemoryChunk::kSizeOffset));
     Check(less_equal, "Live Bytes Count overflow chunk size");
   }
 
   bind(&done);
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32