Improve WTF::HashTable performance by changing probing method

Source/wtf/HashFunctions.h

Index: Source/wtf/HashFunctions.h
diff --git a/Source/wtf/HashFunctions.h b/Source/wtf/HashFunctions.h
index 75fabcd97ad02cea0bcff9ffbb836e80c7dfb93e..ee842c3f7225416b88712ec2250f2b1e98c3d802 100644
--- a/Source/wtf/HashFunctions.h
+++ b/Source/wtf/HashFunctions.h
@@ -32,57 +32,25 @@ namespace WTF {
     template<> struct IntTypes<4> { typedef int32_t SignedType; typedef uint32_t UnsignedType; };
     template<> struct IntTypes<8> { typedef int64_t SignedType; typedef uint64_t UnsignedType; };
 
-    // integer hash function
-
-    // Thomas Wang's 32 Bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
     inline unsigned intHash(uint8_t key8)
     {
-        unsigned key = key8;
-        key += ~(key << 15);
-        key ^= (key >> 10);
-        key += (key << 3);
-        key ^= (key >> 6);
-        key += ~(key << 11);
-        key ^= (key >> 16);
-        return key;
+        return key8;
     }
 
-    // Thomas Wang's 32 Bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
     inline unsigned intHash(uint16_t key16)
     {
-        unsigned key = key16;
-        key += ~(key << 15);
-        key ^= (key >> 10);
-        key += (key << 3);
-        key ^= (key >> 6);
-        key += ~(key << 11);
-        key ^= (key >> 16);
-        return key;
+        return key16;
     }
 
-    // Thomas Wang's 32 Bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
     inline unsigned intHash(uint32_t key) 
     {
-        key += ~(key << 15);
-        key ^= (key >> 10);
-        key += (key << 3);
-        key ^= (key >> 6);
-        key += ~(key << 11);
-        key ^= (key >> 16);
-        return key;
+        return key ^ (key >> 16);
     }
-    
-    // Thomas Wang's 64 bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
+
     inline unsigned intHash(uint64_t key)
     {
-        key += ~(key << 32);
-        key ^= (key >> 22);
-        key += ~(key << 13);
-        key ^= (key >> 8);
-        key += (key << 3);
-        key ^= (key >> 15);
-        key += ~(key << 27);
-        key ^= (key >> 31);
+        key ^= key >> 32;
+        key ^= key >> 16;
         return static_cast<unsigned>(key);
     }
 
@@ -126,7 +94,9 @@ namespace WTF {
 #pragma warning(push)
 #pragma warning(disable: 4244) // work around what seems to be a bug in MSVC's conversion warnings
 #endif
-            return IntHash<uintptr_t>::hash(reinterpret_cast<uintptr_t>(key));
+            uintptr_t keyIntPtr = reinterpret_cast<uintptr_t>(key);
+            keyIntPtr ^= keyIntPtr >> 6;
+            return IntHash<uintptr_t>::hash(keyIntPtr);
 #if COMPILER(MSVC)
 #pragma warning(pop)
 #endif