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<title>[167249] trunk/Source/JavaScriptCore</title>
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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/167249">167249</a></dd>
<dt>Author</dt> <dd>akling@apple.com</dd>
<dt>Date</dt> <dd>2014-04-14 09:19:58 -0700 (Mon, 14 Apr 2014)</dd>
</dl>
<h3>Log Message</h3>
<pre>Array.prototype.concat should allocate output storage only once.
<https://webkit.org/b/131609>
Do a first pass across 'this' and any arguments to compute the
final size of the resulting array from Array.prototype.concat.
This avoids having to grow the output incrementally as we go.
This also includes two other micro-optimizations:
- Mark getProperty() with ALWAYS_INLINE.
- Use JSArray::length() instead of taking the generic property
lookup path when we know an argument is an Array.
My MBP says ~3% progression on Dromaeo/jslib-traverse-jquery.
Reviewed by Darin Adler.
* runtime/ArrayPrototype.cpp:
(JSC::getProperty):
(JSC::arrayProtoFuncConcat):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreruntimeArrayPrototypecpp">trunk/Source/JavaScriptCore/runtime/ArrayPrototype.cpp</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (167248 => 167249)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2014-04-14 16:02:03 UTC (rev 167248)
+++ trunk/Source/JavaScriptCore/ChangeLog 2014-04-14 16:19:58 UTC (rev 167249)
</span><span class="lines">@@ -1,3 +1,27 @@
</span><ins>+2014-04-14 Andreas Kling <akling@apple.com>
+
+ Array.prototype.concat should allocate output storage only once.
+ <https://webkit.org/b/131609>
+
+ Do a first pass across 'this' and any arguments to compute the
+ final size of the resulting array from Array.prototype.concat.
+ This avoids having to grow the output incrementally as we go.
+
+ This also includes two other micro-optimizations:
+
+ - Mark getProperty() with ALWAYS_INLINE.
+
+ - Use JSArray::length() instead of taking the generic property
+ lookup path when we know an argument is an Array.
+
+ My MBP says ~3% progression on Dromaeo/jslib-traverse-jquery.
+
+ Reviewed by Darin Adler.
+
+ * runtime/ArrayPrototype.cpp:
+ (JSC::getProperty):
+ (JSC::arrayProtoFuncConcat):
+
</ins><span class="cx"> 2014-04-14 Benjamin Poulain <benjamin@webkit.org>
</span><span class="cx">
</span><span class="cx"> [JSC] Improve the call site of string comparison in some hot path
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreruntimeArrayPrototypecpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/runtime/ArrayPrototype.cpp (167248 => 167249)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/runtime/ArrayPrototype.cpp 2014-04-14 16:02:03 UTC (rev 167248)
+++ trunk/Source/JavaScriptCore/runtime/ArrayPrototype.cpp 2014-04-14 16:19:58 UTC (rev 167249)
</span><span class="lines">@@ -146,7 +146,7 @@
</span><span class="cx"> // ------------------------------ Array Functions ----------------------------
</span><span class="cx">
</span><span class="cx"> // Helper function
</span><del>-static JSValue getProperty(ExecState* exec, JSObject* obj, unsigned index)
</del><ins>+static ALWAYS_INLINE JSValue getProperty(ExecState* exec, JSObject* obj, unsigned index)
</ins><span class="cx"> {
</span><span class="cx"> PropertySlot slot(obj);
</span><span class="cx"> if (!obj->getPropertySlot(exec, index, slot))
</span><span class="lines">@@ -416,19 +416,33 @@
</span><span class="cx"> EncodedJSValue JSC_HOST_CALL arrayProtoFuncConcat(ExecState* exec)
</span><span class="cx"> {
</span><span class="cx"> JSValue thisValue = exec->thisValue().toThis(exec, StrictMode);
</span><del>- JSArray* arr = constructEmptyArray(exec, nullptr);
- unsigned n = 0;
</del><ins>+ size_t argCount = exec->argumentCount();
</ins><span class="cx"> JSValue curArg = thisValue.toObject(exec);
</span><ins>+ Checked<unsigned, RecordOverflow> finalArraySize = 0;
+
+ for (size_t i = 0; i <= argCount; ++i) {
+ if (JSArray* currentArray = jsDynamicCast<JSArray*>(curArg))
+ finalArraySize += currentArray->length();
+ else
+ finalArraySize++;
+ curArg = exec->uncheckedArgument(i);
+ }
+
+ if (finalArraySize.hasOverflowed())
+ return JSValue::encode(throwOutOfMemoryError(exec));
+
+ JSArray* arr = constructEmptyArray(exec, nullptr, finalArraySize.unsafeGet());
</ins><span class="cx"> if (exec->hadException())
</span><span class="cx"> return JSValue::encode(jsUndefined());
</span><ins>+
+ curArg = thisValue.toObject(exec);
+ unsigned n = 0;
</ins><span class="cx"> size_t i = 0;
</span><del>- size_t argCount = exec->argumentCount();
</del><span class="cx"> while (1) {
</span><del>- if (curArg.inherits(JSArray::info())) {
- unsigned length = curArg.get(exec, exec->propertyNames().length).toUInt32(exec);
- JSObject* curObject = curArg.toObject(exec);
</del><ins>+ if (JSArray* currentArray = jsDynamicCast<JSArray*>(curArg)) {
+ unsigned length = currentArray->length();
</ins><span class="cx"> for (unsigned k = 0; k < length; ++k) {
</span><del>- JSValue v = getProperty(exec, curObject, k);
</del><ins>+ JSValue v = getProperty(exec, currentArray, k);
</ins><span class="cx"> if (exec->hadException())
</span><span class="cx"> return JSValue::encode(jsUndefined());
</span><span class="cx"> if (v)
</span></span></pre>
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