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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/184767">184767</a></dd>
<dt>Author</dt> <dd>akling@apple.com</dd>
<dt>Date</dt> <dd>2015-05-22 03:18:47 -0700 (Fri, 22 May 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>[JSC] Speed up new array construction in Array.prototype.splice().
<https://webkit.org/b/145303>
Reviewed by Benjamin Poulain.
Give splice() a fast path just like slice(), for indexing types where the backing
store can be memcpy'd. I generalized JSArray::fastSlice() a little bit so it works
for this optimization as well.
7% progression on Kraken/stanford-crypto-pbkdf2.
* runtime/JSArray.h:
* runtime/JSArray.cpp:
(JSC::JSArray::fastSlice): Tweak this to return JSArray*, and don't bother throwing
out-of-memory exceptions. Let the caller worry about that.
* runtime/ArrayPrototype.cpp:
(JSC::arrayProtoFuncSlice): Update for fastSlice() changes.
(JSC::arrayProtoFuncSplice): If the object we're splicing out of is a bona fide
JSArray, use fastSlice() to create the returned array instead of doing a generic
get/put loop.</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>
<li><a href="#trunkSourceJavaScriptCoreruntimeJSArraycpp">trunk/Source/JavaScriptCore/runtime/JSArray.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoreruntimeJSArrayh">trunk/Source/JavaScriptCore/runtime/JSArray.h</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (184766 => 184767)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2015-05-22 08:15:34 UTC (rev 184766)
+++ trunk/Source/JavaScriptCore/ChangeLog 2015-05-22 10:18:47 UTC (rev 184767)
</span><span class="lines">@@ -1,3 +1,27 @@
</span><ins>+2015-05-22 Andreas Kling <akling@apple.com>
+
+ [JSC] Speed up new array construction in Array.prototype.splice().
+ <https://webkit.org/b/145303>
+
+ Reviewed by Benjamin Poulain.
+
+ Give splice() a fast path just like slice(), for indexing types where the backing
+ store can be memcpy'd. I generalized JSArray::fastSlice() a little bit so it works
+ for this optimization as well.
+
+ 7% progression on Kraken/stanford-crypto-pbkdf2.
+
+ * runtime/JSArray.h:
+ * runtime/JSArray.cpp:
+ (JSC::JSArray::fastSlice): Tweak this to return JSArray*, and don't bother throwing
+ out-of-memory exceptions. Let the caller worry about that.
+
+ * runtime/ArrayPrototype.cpp:
+ (JSC::arrayProtoFuncSlice): Update for fastSlice() changes.
+ (JSC::arrayProtoFuncSplice): If the object we're splicing out of is a bona fide
+ JSArray, use fastSlice() to create the returned array instead of doing a generic
+ get/put loop.
+
</ins><span class="cx"> 2015-05-21 Filip Pizlo <fpizlo@apple.com>
</span><span class="cx">
</span><span class="cx"> CPS rethreading should really get rid of GetLocals
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreruntimeArrayPrototypecpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/runtime/ArrayPrototype.cpp (184766 => 184767)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/runtime/ArrayPrototype.cpp 2015-05-22 08:15:34 UTC (rev 184766)
+++ trunk/Source/JavaScriptCore/runtime/ArrayPrototype.cpp 2015-05-22 10:18:47 UTC (rev 184767)
</span><span class="lines">@@ -602,9 +602,8 @@
</span><span class="cx"> unsigned end = argumentClampedIndexFromStartOrEnd(exec, 1, length, length);
</span><span class="cx">
</span><span class="cx"> if (isJSArray(thisObj)) {
</span><del>- EncodedJSValue result;
- if (asArray(thisObj)->fastSlice(*exec, begin, end - begin, result))
- return result;
</del><ins>+ if (JSArray* result = asArray(thisObj)->fastSlice(*exec, begin, end - begin))
+ return JSValue::encode(result);
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> JSArray* result = constructEmptyArray(exec, nullptr, end - begin);
</span><span class="lines">@@ -634,6 +633,8 @@
</span><span class="cx"> {
</span><span class="cx"> // 15.4.4.12
</span><span class="cx">
</span><ins>+ VM& vm = exec->vm();
+
</ins><span class="cx"> JSObject* thisObj = exec->thisValue().toThis(exec, StrictMode).toObject(exec);
</span><span class="cx"> unsigned length = getLength(exec, thisObj);
</span><span class="cx"> if (exec->hadException())
</span><span class="lines">@@ -655,17 +656,22 @@
</span><span class="cx"> deleteCount = static_cast<unsigned>(deleteDouble);
</span><span class="cx"> }
</span><span class="cx">
</span><del>- JSArray* resObj = JSArray::tryCreateUninitialized(exec->vm(), exec->lexicalGlobalObject()->arrayStructureForIndexingTypeDuringAllocation(ArrayWithUndecided), deleteCount);
- if (!resObj)
- return JSValue::encode(throwOutOfMemoryError(exec));
</del><ins>+ JSArray* result = nullptr;
</ins><span class="cx">
</span><del>- JSValue result = resObj;
- VM& vm = exec->vm();
- for (unsigned k = 0; k < deleteCount; k++) {
- JSValue v = getProperty(exec, thisObj, k + begin);
- if (exec->hadException())
- return JSValue::encode(jsUndefined());
- resObj->initializeIndex(vm, k, v);
</del><ins>+ if (isJSArray(thisObj))
+ result = asArray(thisObj)->fastSlice(*exec, begin, deleteCount);
+
+ if (!result) {
+ result = JSArray::tryCreateUninitialized(vm, exec->lexicalGlobalObject()->arrayStructureForIndexingTypeDuringAllocation(ArrayWithUndecided), deleteCount);
+ if (!result)
+ return JSValue::encode(throwOutOfMemoryError(exec));
+
+ for (unsigned k = 0; k < deleteCount; ++k) {
+ JSValue v = getProperty(exec, thisObj, k + begin);
+ if (exec->hadException())
+ return JSValue::encode(jsUndefined());
+ result->initializeIndex(vm, k, v);
+ }
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> unsigned additionalArgs = std::max<int>(exec->argumentCount() - 2, 0);
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreruntimeJSArraycpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/runtime/JSArray.cpp (184766 => 184767)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/runtime/JSArray.cpp 2015-05-22 08:15:34 UTC (rev 184766)
+++ trunk/Source/JavaScriptCore/runtime/JSArray.cpp 2015-05-22 10:18:47 UTC (rev 184767)
</span><span class="lines">@@ -675,7 +675,7 @@
</span><span class="cx"> }
</span><span class="cx"> }
</span><span class="cx">
</span><del>-bool JSArray::fastSlice(ExecState& exec, unsigned startIndex, unsigned count, EncodedJSValue& result)
</del><ins>+JSArray* JSArray::fastSlice(ExecState& exec, unsigned startIndex, unsigned count)
</ins><span class="cx"> {
</span><span class="cx"> auto arrayType = indexingType();
</span><span class="cx"> switch (arrayType) {
</span><span class="lines">@@ -684,14 +684,12 @@
</span><span class="cx"> case ArrayWithContiguous: {
</span><span class="cx"> VM& vm = exec.vm();
</span><span class="cx"> if (count >= MIN_SPARSE_ARRAY_INDEX || structure(vm)->holesMustForwardToPrototype(vm))
</span><del>- return false;
</del><ins>+ return nullptr;
</ins><span class="cx">
</span><span class="cx"> Structure* resultStructure = exec.lexicalGlobalObject()->arrayStructureForIndexingTypeDuringAllocation(arrayType);
</span><span class="cx"> JSArray* resultArray = JSArray::tryCreateUninitialized(vm, resultStructure, count);
</span><del>- if (!resultArray) {
- result = JSValue::encode(throwOutOfMemoryError(&exec));
- return true;
- }
</del><ins>+ if (!resultArray)
+ return nullptr;
</ins><span class="cx">
</span><span class="cx"> auto& resultButterfly = *resultArray->butterfly();
</span><span class="cx"> if (arrayType == ArrayWithDouble)
</span><span class="lines">@@ -700,13 +698,11 @@
</span><span class="cx"> memcpy(resultButterfly.contiguous().data(), m_butterfly->contiguous().data() + startIndex, sizeof(JSValue) * count);
</span><span class="cx"> resultButterfly.setPublicLength(count);
</span><span class="cx">
</span><del>- result = JSValue::encode(resultArray);
- return true;
</del><ins>+ return resultArray;
</ins><span class="cx"> }
</span><span class="cx"> default:
</span><del>- break;
</del><ins>+ return nullptr;
</ins><span class="cx"> }
</span><del>- return false;
</del><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> bool JSArray::shiftCountWithArrayStorage(VM& vm, unsigned startIndex, unsigned count, ArrayStorage* storage)
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreruntimeJSArrayh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/runtime/JSArray.h (184766 => 184767)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/runtime/JSArray.h 2015-05-22 08:15:34 UTC (rev 184766)
+++ trunk/Source/JavaScriptCore/runtime/JSArray.h 2015-05-22 10:18:47 UTC (rev 184767)
</span><span class="lines">@@ -73,7 +73,7 @@
</span><span class="cx"> JS_EXPORT_PRIVATE void push(ExecState*, JSValue);
</span><span class="cx"> JS_EXPORT_PRIVATE JSValue pop(ExecState*);
</span><span class="cx">
</span><del>- bool fastSlice(ExecState&, unsigned startIndex, unsigned count, EncodedJSValue&);
</del><ins>+ JSArray* fastSlice(ExecState&, unsigned startIndex, unsigned count);
</ins><span class="cx">
</span><span class="cx"> enum ShiftCountMode {
</span><span class="cx"> // This form of shift hints that we're doing queueing. With this assumption in hand,
</span></span></pre>
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