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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/184385">184385</a></dd>
<dt>Author</dt> <dd>carlosgc@webkit.org</dd>
<dt>Date</dt> <dd>2015-05-15 05:44:50 -0700 (Fri, 15 May 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>Merge <a href="http://trac.webkit.org/projects/webkit/changeset/184346">r184346</a> - String.prototype.split() should create efficient substrings.
<https://webkit.org/b/144985>
<rdar://problem/20949344>
Reviewed by Geoffrey Garen.
Teach split() how to make substring JSStrings instead of relying on StringImpl's
substring sharing mechanism. The optimization works by deferring the construction
of a StringImpl until the substring's value is actually needed.
This knocks ~2MB off of theverge.com by avoiding the extra StringImpl allocations.
Out of ~70000 substrings created by split(), only ~2000 of them get reified.
* runtime/StringPrototype.cpp:
(JSC::jsSubstring):
(JSC::splitStringByOneCharacterImpl):
(JSC::stringProtoFuncSplit):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#releasesWebKitGTKwebkit28SourceJavaScriptCoreChangeLog">releases/WebKitGTK/webkit-2.8/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#releasesWebKitGTKwebkit28SourceJavaScriptCoreruntimeStringPrototypecpp">releases/WebKitGTK/webkit-2.8/Source/JavaScriptCore/runtime/StringPrototype.cpp</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="releasesWebKitGTKwebkit28SourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: releases/WebKitGTK/webkit-2.8/Source/JavaScriptCore/ChangeLog (184384 => 184385)</h4>
<pre class="diff"><span>
<span class="info">--- releases/WebKitGTK/webkit-2.8/Source/JavaScriptCore/ChangeLog 2015-05-15 12:38:28 UTC (rev 184384)
+++ releases/WebKitGTK/webkit-2.8/Source/JavaScriptCore/ChangeLog 2015-05-15 12:44:50 UTC (rev 184385)
</span><span class="lines">@@ -1,3 +1,23 @@
</span><ins>+2015-05-14 Andreas Kling <akling@apple.com>
+
+ String.prototype.split() should create efficient substrings.
+ <https://webkit.org/b/144985>
+ <rdar://problem/20949344>
+
+ Reviewed by Geoffrey Garen.
+
+ Teach split() how to make substring JSStrings instead of relying on StringImpl's
+ substring sharing mechanism. The optimization works by deferring the construction
+ of a StringImpl until the substring's value is actually needed.
+
+ This knocks ~2MB off of theverge.com by avoiding the extra StringImpl allocations.
+ Out of ~70000 substrings created by split(), only ~2000 of them get reified.
+
+ * runtime/StringPrototype.cpp:
+ (JSC::jsSubstring):
+ (JSC::splitStringByOneCharacterImpl):
+ (JSC::stringProtoFuncSplit):
+
</ins><span class="cx"> 2015-05-12 Gabor Loki <loki@webkit.org>
</span><span class="cx">
</span><span class="cx"> Workaround for Cortex-A53 erratum 843419
</span></span></pre></div>
<a id="releasesWebKitGTKwebkit28SourceJavaScriptCoreruntimeStringPrototypecpp"></a>
<div class="modfile"><h4>Modified: releases/WebKitGTK/webkit-2.8/Source/JavaScriptCore/runtime/StringPrototype.cpp (184384 => 184385)</h4>
<pre class="diff"><span>
<span class="info">--- releases/WebKitGTK/webkit-2.8/Source/JavaScriptCore/runtime/StringPrototype.cpp 2015-05-15 12:38:28 UTC (rev 184384)
+++ releases/WebKitGTK/webkit-2.8/Source/JavaScriptCore/runtime/StringPrototype.cpp 2015-05-15 12:44:50 UTC (rev 184385)
</span><span class="lines">@@ -168,6 +168,16 @@
</span><span class="cx"> return jsString(exec, string);
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+// Helper that tries to use the JSString substring sharing mechanism if 'originalValue' is a JSString.
+static inline JSString* jsSubstring(ExecState* exec, JSValue originalValue, const String& string, unsigned offset, unsigned length)
+{
+ if (originalValue.isString()) {
+ ASSERT(asString(originalValue)->value(exec) == string);
+ return jsSubstring(exec, asString(originalValue), offset, length);
+ }
+ return jsSubstring(exec, string, offset, length);
+}
+
</ins><span class="cx"> static NEVER_INLINE String substituteBackreferencesSlow(StringView replacement, StringView source, const int* ovector, RegExp* reg, size_t i)
</span><span class="cx"> {
</span><span class="cx"> StringBuilder substitutedReplacement;
</span><span class="lines">@@ -1010,7 +1020,7 @@
</span><span class="cx">
</span><span class="cx"> // Return true in case of early return (resultLength got to limitLength).
</span><span class="cx"> template<typename CharacterType>
</span><del>-static ALWAYS_INLINE bool splitStringByOneCharacterImpl(ExecState* exec, JSArray* result, const String& input, StringImpl* string, UChar separatorCharacter, size_t& position, unsigned& resultLength, unsigned limitLength)
</del><ins>+static ALWAYS_INLINE bool splitStringByOneCharacterImpl(ExecState* exec, JSArray* result, JSValue originalValue, const String& input, StringImpl* string, UChar separatorCharacter, size_t& position, unsigned& resultLength, unsigned limitLength)
</ins><span class="cx"> {
</span><span class="cx"> // 12. Let q = p.
</span><span class="cx"> size_t matchPosition;
</span><span class="lines">@@ -1024,7 +1034,7 @@
</span><span class="cx"> // through q (exclusive).
</span><span class="cx"> // 2. Call the [[DefineOwnProperty]] internal method of A with arguments ToString(lengthA),
</span><span class="cx"> // Property Descriptor {[[Value]]: T, [[Writable]]: true, [[Enumerable]]: true, [[Configurable]]: true}, and false.
</span><del>- result->putDirectIndex(exec, resultLength, jsSubstring(exec, input, position, matchPosition - position));
</del><ins>+ result->putDirectIndex(exec, resultLength, jsSubstring(exec, originalValue, input, position, matchPosition - position));
</ins><span class="cx"> // 3. Increment lengthA by 1.
</span><span class="cx"> // 4. If lengthA == lim, return A.
</span><span class="cx"> if (++resultLength == limitLength)
</span><span class="lines">@@ -1130,7 +1140,7 @@
</span><span class="cx"> // through q (exclusive).
</span><span class="cx"> // 2. Call the [[DefineOwnProperty]] internal method of A with arguments ToString(lengthA),
</span><span class="cx"> // Property Descriptor {[[Value]]: T, [[Writable]]: true, [[Enumerable]]: true, [[Configurable]]: true}, and false.
</span><del>- result->putDirectIndex(exec, resultLength, jsSubstring(exec, input, position, matchPosition - position));
</del><ins>+ result->putDirectIndex(exec, resultLength, jsSubstring(exec, thisValue, input, position, matchPosition - position));
</ins><span class="cx">
</span><span class="cx"> // 3. Increment lengthA by 1.
</span><span class="cx"> // 4. If lengthA == lim, return A.
</span><span class="lines">@@ -1150,7 +1160,7 @@
</span><span class="cx"> // ToString(lengthA), Property Descriptor {[[Value]]: cap[i], [[Writable]]:
</span><span class="cx"> // true, [[Enumerable]]: true, [[Configurable]]: true}, and false.
</span><span class="cx"> int sub = ovector[i * 2];
</span><del>- result->putDirectIndex(exec, resultLength, sub < 0 ? jsUndefined() : jsSubstring(exec, input, sub, ovector[i * 2 + 1] - sub));
</del><ins>+ result->putDirectIndex(exec, resultLength, sub < 0 ? jsUndefined() : jsSubstring(exec, thisValue, input, sub, ovector[i * 2 + 1] - sub));
</ins><span class="cx"> // c Increment lengthA by 1.
</span><span class="cx"> // d If lengthA == lim, return A.
</span><span class="cx"> if (++resultLength == limit)
</span><span class="lines">@@ -1215,10 +1225,10 @@
</span><span class="cx"> separatorCharacter = separatorImpl->characters16()[0];
</span><span class="cx">
</span><span class="cx"> if (stringImpl->is8Bit()) {
</span><del>- if (splitStringByOneCharacterImpl<LChar>(exec, result, input, stringImpl, separatorCharacter, position, resultLength, limit))
</del><ins>+ if (splitStringByOneCharacterImpl<LChar>(exec, result, thisValue, input, stringImpl, separatorCharacter, position, resultLength, limit))
</ins><span class="cx"> return JSValue::encode(result);
</span><span class="cx"> } else {
</span><del>- if (splitStringByOneCharacterImpl<UChar>(exec, result, input, stringImpl, separatorCharacter, position, resultLength, limit))
</del><ins>+ if (splitStringByOneCharacterImpl<UChar>(exec, result, thisValue, input, stringImpl, separatorCharacter, position, resultLength, limit))
</ins><span class="cx"> return JSValue::encode(result);
</span><span class="cx"> }
</span><span class="cx"> } else {
</span><span class="lines">@@ -1233,7 +1243,7 @@
</span><span class="cx"> // through q (exclusive).
</span><span class="cx"> // 2. Call the [[DefineOwnProperty]] internal method of A with arguments ToString(lengthA),
</span><span class="cx"> // Property Descriptor {[[Value]]: T, [[Writable]]: true, [[Enumerable]]: true, [[Configurable]]: true}, and false.
</span><del>- result->putDirectIndex(exec, resultLength, jsSubstring(exec, input, position, matchPosition - position));
</del><ins>+ result->putDirectIndex(exec, resultLength, jsSubstring(exec, thisValue, input, position, matchPosition - position));
</ins><span class="cx"> // 3. Increment lengthA by 1.
</span><span class="cx"> // 4. If lengthA == lim, return A.
</span><span class="cx"> if (++resultLength == limit)
</span><span class="lines">@@ -1250,7 +1260,7 @@
</span><span class="cx"> // through s (exclusive).
</span><span class="cx"> // 15. Call the [[DefineOwnProperty]] internal method of A with arguments ToString(lengthA), Property Descriptor
</span><span class="cx"> // {[[Value]]: T, [[Writable]]: true, [[Enumerable]]: true, [[Configurable]]: true}, and false.
</span><del>- result->putDirectIndex(exec, resultLength++, jsSubstring(exec, input, position, input.length() - position));
</del><ins>+ result->putDirectIndex(exec, resultLength++, jsSubstring(exec, thisValue, input, position, input.length() - position));
</ins><span class="cx">
</span><span class="cx"> // 16. Return A.
</span><span class="cx"> return JSValue::encode(result);
</span></span></pre>
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