Changeset 27127 in webkit for trunk/JavaScriptCore

Timestamp:

Oct 26, 2007, 3:45:34 PM (18 years ago)

Author:

ggaren

Message:

Reviewed by Maciej Stachowiak.

Tweaked property maps to remove 2 branches. 2.5% speedup on SunSpider.

• kjs/property_map.cpp: Use a special no branch accessor to the UString's hash value. Also, return immediately instead of branching to the end of the loop if the value is not found. (KJS::PropertyMap::get): (KJS::PropertyMap::getLocation): (KJS::PropertyMap::put): (KJS::PropertyMap::insert): (KJS::PropertyMap::remove): (KJS::PropertyMap::checkConsistency):

• kjs/ustring.h: (KJS::UString::Rep::computedHash): Special no branch accessor to the UString's hash value. Used when the caller knows that the hash value has already been computed. (For example, if the caller got the UString from an Identifier.)

Location:

trunk/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• kjs/property_map.cpp (modified) (14 diffs)
• kjs/ustring.h (modified) (1 diff)

trunk/JavaScriptCore/ChangeLog

@@ +1 @@
+2007-10-26  Geoffrey Garen  <[email protected]>
+
+        Reviewed by Maciej Stachowiak.
+        
+        Tweaked property maps to remove 2 branches. 2.5% speedup on SunSpider.
+
+        * kjs/property_map.cpp: Use a special no branch accessor to the UString's
+        hash value. Also, return immediately instead of branching to the end
+        of the loop if the value is not found.
+        (KJS::PropertyMap::get):
+        (KJS::PropertyMap::getLocation):
+        (KJS::PropertyMap::put):
+        (KJS::PropertyMap::insert):
+        (KJS::PropertyMap::remove):
+        (KJS::PropertyMap::checkConsistency):
+
+        * kjs/ustring.h:
+        (KJS::UString::Rep::computedHash): Special no branch accessor to the
+        UString's hash value. Used when the caller knows that the hash value
+        has already been computed. (For example, if the caller got the UString
+        from an Identifier.)
+
 2007-10-26  Geoffrey Garen  <[email protected]>
 

trunk/JavaScriptCore/kjs/property_map.cpp

@@ -38 +38 @@
 #define USE_SINGLE_ENTRY 1
 
-// 2/28/2006 ggaren: super accurate JS iBench says that USE_SINGLE_ENTRY is a
+// 2/28/2006 ggaren: command-line JS iBench says that USE_SINGLE_ENTRY is a
 // 3.2% performance boost.
 
@@ -176 +176 @@
     }
     
-    unsigned h = rep->hash();
+    unsigned h = rep->computedHash();
     int sizeMask = m_u.table->sizeMask;
     Entry *entries = m_u.table->entries;
@@ -185 +185 @@
     numCollisions += entries[i].key && entries[i].key != rep;
 #endif
-    while (UString::Rep *key = entries[i].key) {
+    while (1) {
+        UString::Rep* key = entries[i].key;
+
+        if (!key)
+            return 0;
+
         if (rep == key) {
             attributes = entries[i].attributes;
             return entries[i].value;
         }
+        
         if (k == 0)
             k = 1 | (h % sizeMask);
@@ -197 +203 @@
 #endif
     }
-    return 0;
 }
 
@@ -215 +220 @@
     }
     
-    unsigned h = rep->hash();
+    unsigned h = rep->computedHash();
     int sizeMask = m_u.table->sizeMask;
     Entry *entries = m_u.table->entries;
@@ -224 +229 @@
     numCollisions += entries[i].key && entries[i].key != rep;
 #endif
-    while (UString::Rep *key = entries[i].key) {
+    while (1) {
+        UString::Rep* key = entries[i].key;
+
+        if (!key)
+            return 0;
+
         if (rep == key)
             return entries[i].value;
+        
         if (k == 0)
             k = 1 | (h % sizeMask);
@@ -234 +245 @@
 #endif
     }
-    return 0;
 }
 
@@ -252 +262 @@
     }
     
-    unsigned h = rep->hash();
+    unsigned h = rep->computedHash();
     int sizeMask = m_u.table->sizeMask;
     Entry *entries = m_u.table->entries;
@@ -261 +271 @@
     numCollisions += entries[i].key && entries[i].key != rep;
 #endif
-    while (UString::Rep *key = entries[i].key) {
+    while (1) {
+        UString::Rep* key = entries[i].key;
+
+        if (!key)
+            return 0;
+
         if (rep == key)
             return &entries[i].value;
+        
         if (k == 0)
             k = 1 | (h % sizeMask);
@@ -271 +287 @@
 #endif
     }
-    return 0;
 }
 
@@ -331 +346 @@
         expand();
     
-    unsigned h = rep->hash();
+    unsigned h = rep->computedHash();
     int sizeMask = m_u.table->sizeMask;
     Entry *entries = m_u.table->entries;
@@ -385 +400 @@
     ASSERT(m_u.table);
 
-    unsigned h = key->hash();
+    unsigned h = key->computedHash();
     int sizeMask = m_u.table->sizeMask;
     Entry *entries = m_u.table->entries;
@@ -512 +527 @@
 
     // Find the thing to remove.
-    unsigned h = rep->hash();
+    unsigned h = rep->computedHash();
     int sizeMask = m_u.table->sizeMask;
     Entry *entries = m_u.table->entries;
@@ -729 +744 @@
             continue;
         }
-        unsigned h = rep->hash();
+        unsigned h = rep->computedHash();
         int i = h & m_u.table->sizeMask;
         int k = 0;

trunk/JavaScriptCore/kjs/ustring.h

@@ -148 +148 @@
       
       unsigned hash() const { if (_hash == 0) _hash = computeHash(data(), len); return _hash; }
+      unsigned computedHash() const { ASSERT(_hash); return _hash; } // fast path for Identifiers
+
       static unsigned computeHash(const UChar *, int length);
       static unsigned computeHash(const char *);