Changeset 141295 in webkit

Timestamp:

Jan 30, 2013 12:05:14 PM (11 years ago)

Author:

mhahnenberg@apple.com

Message:

Structure::m_outOfLineCapacity is unnecessary
​https://bugs.webkit.org/show_bug.cgi?id=108206

Reviewed by Geoffrey Garen.

Source/JavaScriptCore:

We can calculate our out of line capacity by using the outOfLineSize and our knowledge about our resize policy.
According to GDB, this knocks Structures down from 136 bytes to 128 bytes (I'm guessing the extra bytes are from
better alignment of object fields), which puts Structures in a smaller size class. Woohoo! Looks neutral on our
benchmarks.

• runtime/Structure.cpp:

(JSC::Structure::Structure):
(JSC):
(JSC::Structure::suggestedNewOutOfLineStorageCapacity):
(JSC::Structure::addPropertyTransition):
(JSC::Structure::addPropertyWithoutTransition):

• runtime/Structure.h:

(Structure):
(JSC::Structure::outOfLineCapacity):
(JSC::Structure::totalStorageCapacity):

Source/WTF:

We're adding a new function that gives us the ability to round a value up to the next power of a certain base.

• wtf/MathExtras.h:

(WTF::roundUpToPowerOf):

Location:

trunk/Source

Files:

• JavaScriptCore/ChangeLog (modified) (1 diff)
• JavaScriptCore/runtime/Structure.cpp (modified) (7 diffs)
• JavaScriptCore/runtime/Structure.h (modified) (3 diffs)
• WTF/ChangeLog (modified) (1 diff)
• WTF/wtf/MathExtras.h (modified) (1 diff)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2013-01-29  Mark Hahnenberg  <mhahnenberg@apple.com>
+
+        Structure::m_outOfLineCapacity is unnecessary
+        https://bugs.webkit.org/show_bug.cgi?id=108206
+
+        Reviewed by Geoffrey Garen.
+
+        We can calculate our out of line capacity by using the outOfLineSize and our knowledge about our resize policy.
+        According to GDB, this knocks Structures down from 136 bytes to 128 bytes (I'm guessing the extra bytes are from
+        better alignment of object fields), which puts Structures in a smaller size class. Woohoo! Looks neutral on our 
+        benchmarks.
+
+        * runtime/Structure.cpp:
+        (JSC::Structure::Structure):
+        (JSC):
+        (JSC::Structure::suggestedNewOutOfLineStorageCapacity):
+        (JSC::Structure::addPropertyTransition):
+        (JSC::Structure::addPropertyWithoutTransition):
+        * runtime/Structure.h:
+        (Structure):
+        (JSC::Structure::outOfLineCapacity):
+        (JSC::Structure::totalStorageCapacity):
+
 2013-01-29  Geoffrey Garen  <ggaren@apple.com>
 

trunk/Source/JavaScriptCore/runtime/Structure.cpp

@@ -158 +158 @@
     , m_classInfo(classInfo)
     , m_transitionWatchpointSet(InitializedWatching)
-    , m_outOfLineCapacity(0)
     , m_inlineCapacity(inlineCapacity)
     , m_offset(invalidOffset)
@@ -185 +184 @@
     , m_classInfo(&s_info)
     , m_transitionWatchpointSet(InitializedWatching)
-    , m_outOfLineCapacity(0)
     , m_inlineCapacity(0)
     , m_offset(invalidOffset)
@@ -208 +206 @@
     , m_classInfo(previous->m_classInfo)
     , m_transitionWatchpointSet(InitializedWatching)
-    , m_outOfLineCapacity(previous->m_outOfLineCapacity)
     , m_inlineCapacity(previous->m_inlineCapacity)
     , m_offset(invalidOffset)
@@ -274 +271 @@
 }
 
-void Structure::growOutOfLineCapacity()
-{
-    m_outOfLineCapacity = nextOutOfLineStorageCapacity(m_outOfLineCapacity);
-}
-
 size_t Structure::suggestedNewOutOfLineStorageCapacity()
 {
-    return nextOutOfLineStorageCapacity(m_outOfLineCapacity);
+    return nextOutOfLineStorageCapacity(outOfLineCapacity());
 }
  
@@ -366 +358 @@
         ASSERT(structure != transition);
         offset = transition->putSpecificValue(globalData, propertyName, attributes, specificValue);
-        if (transition->outOfLineSize() > transition->outOfLineCapacity())
-            transition->growOutOfLineCapacity();
         return transition;
     }
@@ -392 +382 @@
 
     offset = transition->putSpecificValue(globalData, propertyName, attributes, specificValue);
-    if (transition->outOfLineSize() > transition->outOfLineCapacity())
-        transition->growOutOfLineCapacity();
 
     transition->m_offset = offset;
@@ -665 +653 @@
     pin();
 
-    PropertyOffset offset = putSpecificValue(globalData, propertyName, attributes, specificValue);
-    if (outOfLineSize() > outOfLineCapacity())
-        growOutOfLineCapacity();
-    return offset;
+    return putSpecificValue(globalData, propertyName, attributes, specificValue);
 }
 

trunk/Source/JavaScriptCore/runtime/Structure.h

@@ -183 +183 @@
         bool transitivelyTransitionedFrom(Structure* structureToFind);
 
-        void growOutOfLineCapacity();
         unsigned outOfLineCapacity() const
         {
-            ASSERT(structure()->classInfo() == &s_info);
-            return m_outOfLineCapacity;
+            unsigned outOfLineSize = this->outOfLineSize();
+
+            if (!outOfLineSize)
+                return 0;
+
+            if (outOfLineSize <= initialOutOfLineCapacity)
+                return initialOutOfLineCapacity;
+
+            ASSERT(outOfLineSize > initialOutOfLineCapacity);
+            return WTF::roundUpToPowerOf<outOfLineGrowthFactor>(outOfLineSize);
         }
         unsigned outOfLineSize() const
@@ -227 +234 @@
         {
             ASSERT(structure()->classInfo() == &s_info);
-            return m_outOfLineCapacity + inlineCapacity();
+            return outOfLineCapacity() + inlineCapacity();
         }
 
@@ -436 +443 @@
         mutable InlineWatchpointSet m_transitionWatchpointSet;
 
-        uint32_t m_outOfLineCapacity;
         uint8_t m_inlineCapacity;
         COMPILE_ASSERT(firstOutOfLineOffset < 256, firstOutOfLineOffset_fits);

trunk/Source/WTF/ChangeLog

@@ +1 @@
+2013-01-29  Mark Hahnenberg  <mhahnenberg@apple.com>
+
+        Structure::m_outOfLineCapacity is unnecessary
+        https://bugs.webkit.org/show_bug.cgi?id=108206
+
+        Reviewed by Geoffrey Garen.
+
+        We're adding a new function that gives us the ability to round a value up to the next power of a certain base.
+
+        * wtf/MathExtras.h:
+        (WTF::roundUpToPowerOf):
+
 2013-01-30  Zeno Albisser  <zeno@webkit.org>
 

trunk/Source/WTF/wtf/MathExtras.h

@@ -430 +430 @@
 }
 
+namespace WTF {
+
+// Be careful, this might be super slow in a hot loop.
+template<size_t exponent> inline size_t roundUpToPowerOf(size_t v)
+{
+    return round(pow(static_cast<double>(exponent), ceil(log(static_cast<double>(v)) / log(static_cast<double>(exponent)))));
+}
+
+// From http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
+template<> inline size_t roundUpToPowerOf<2>(size_t v)
+{
+    v--;
+    v |= v >> 1;
+    v |= v >> 2;
+    v |= v >> 4;
+    v |= v >> 8;
+    v |= v >> 16;
+#if defined(__LP64__) && __LP64__
+    v |= v >> 32;
+#endif
+    v++;
+    return v;
+}
+
+} // namespace WTF
+
 #endif // #ifndef WTF_MathExtras_h