Changeset 201784 in webkit

Timestamp:

Jun 7, 2016 6:53:44 PM (8 years ago)

Author:

akling@apple.com

Message:

CachedScript should avoid recomputing its hash multiple times.
<​https://webkit.org/b/158506>

Reviewed by Saam Barati.

JSBench was hitting CachedScript::script() hard and spending lots of time hashing scripts.
Since we're already caching the hash in a member variable, don't bother rehashing if we've
already done it before.

This takes total time spent in StringImpl::hashSlowCase() from 1600ms to 77ms on my MBP.

• loader/cache/CachedScript.cpp:

(WebCore::CachedScript::script):

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• loader/cache/CachedScript.cpp (modified) (1 diff)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2016-06-07  Andreas Kling  <akling@apple.com>
+
+        CachedScript should avoid recomputing its hash multiple times.
+        <https://webkit.org/b/158506>
+
+        Reviewed by Saam Barati.
+
+        JSBench was hitting CachedScript::script() hard and spending lots of time hashing scripts.
+        Since we're already caching the hash in a member variable, don't bother rehashing if we've
+        already done it before.
+
+        This takes total time spent in StringImpl::hashSlowCase() from 1600ms to 77ms on my MBP.
+
+        * loader/cache/CachedScript.cpp:
+        (WebCore::CachedScript::script):
+
 2016-06-07  Keith Rollin  <krollin@apple.com>
 

trunk/Source/WebCore/loader/cache/CachedScript.cpp

@@ -94 +94 @@
     if (!m_script) {
         m_script = m_decoder->decodeAndFlush(m_data->data(), encodedSize());
-        m_scriptHash = m_script.impl()->hash();
+        ASSERT(!m_scriptHash || m_scriptHash == m_script.impl()->hash());
+        if (m_decodingState == NeverDecoded)
+            m_scriptHash = m_script.impl()->hash();
         m_decodingState = DataAndDecodedStringHaveDifferentBytes;
         setDecodedSize(m_script.sizeInBytes());