Changeset 43090 in webkit for trunk/JavaScriptCore

Timestamp:

Apr 30, 2009, 2:18:31 PM (16 years ago)

Author:

[email protected]

Message:

2009-04-30 Maciej Stachowiak <​[email protected]>

Reviewed by Geoff Garen.

• make BaseStrings have themselves as a base, instead of nothing, to remove common branches

~0.7% SunSpider speedup

• runtime/UString.h: (JSC::UString::Rep::Rep): For the constructor without a base, set self as base instead of null. (JSC::UString::Rep::baseString): Just read m_baseString - no more branching.

Location:

trunk/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• runtime/UString.h (modified) (4 diffs)

trunk/JavaScriptCore/ChangeLog

@@ +1 @@
+2009-04-30  Maciej Stachowiak  <[email protected]>
+
+        Reviewed by Geoff Garen.
+
+        - make BaseStrings have themselves as a base, instead of nothing, to remove common branches
+
+        ~0.7% SunSpider speedup
+
+        * runtime/UString.h:
+        (JSC::UString::Rep::Rep): For the constructor without a base, set self as base instead of null.
+        (JSC::UString::Rep::baseString): Just read m_baseString - no more branching.
+
 2009-04-30  Gavin Barraclough  <[email protected]>
 

trunk/JavaScriptCore/runtime/UString.h

@@ -134 +134 @@
 
         protected:
+            // constructor for use by BaseString subclass; they are their own bases
             Rep(int length)
                 : offset(0)
@@ -139 +140 @@
                 , rc(1)
                 , _hash(0)
-                , m_nothing(0)
+                , m_baseString(static_cast<BaseString*>(this))
             {
             }
@@ -153 +154 @@
             }
 
-            union {
-                // If !baseIsSelf()
-                BaseString* m_baseString;
-                // If baseIsSelf()
-                void* m_nothing;
-            };
+
+            BaseString* m_baseString;
 
         private:
@@ -411 +408 @@
     inline UString::BaseString* UString::Rep::baseString()
     {
-        return baseIsSelf() ? reinterpret_cast<BaseString*>(this) : m_baseString;
+        return m_baseString;
     }
 
     inline const UString::BaseString* UString::Rep::baseString() const
     {
-        return const_cast<Rep*>(this)->baseString();
+        return m_baseString;
     }