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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/173534">173534</a></dd>
<dt>Author</dt> <dd>fpizlo@apple.com</dd>
<dt>Date</dt> <dd>2014-09-11 13:04:38 -0700 (Thu, 11 Sep 2014)</dd>
</dl>
<h3>Log Message</h3>
<pre>REGRESSION (<a href="http://trac.webkit.org/projects/webkit/changeset/172129">r172129</a>): Vine pages load as blank
https://bugs.webkit.org/show_bug.cgi?id=136655
rdar://problem/18281215
Reviewed by Michael Saboff.
If lastNode is something that is subject to DCE, then removing the Phantom's reference to something
that lastNode references means that the thing being referenced may no longer be kept alive for OSR.
Teach PhantomRemovalPhase that it's only safe to do this if lastNode is a Phantom. That's probably too
conservative, but that's fine since this is mainly just an optimization to make the IR sane to read and
reasonably compact; it's OK if we miss cases here.
* dfg/DFGPhantomRemovalPhase.cpp:
(JSC::DFG::PhantomRemovalPhase::run):
* tests/stress/remove-phantom-after-setlocal.js: Added.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoredfgDFGPhantomRemovalPhasecpp">trunk/Source/JavaScriptCore/dfg/DFGPhantomRemovalPhase.cpp</a></li>
</ul>
<h3>Added Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoretestsstressremovephantomaftersetlocaljs">trunk/Source/JavaScriptCore/tests/stress/remove-phantom-after-setlocal.js</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (173533 => 173534)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2014-09-11 19:57:33 UTC (rev 173533)
+++ trunk/Source/JavaScriptCore/ChangeLog 2014-09-11 20:04:38 UTC (rev 173534)
</span><span class="lines">@@ -1,3 +1,21 @@
</span><ins>+2014-09-11 Filip Pizlo <fpizlo@apple.com>
+
+ REGRESSION (r172129): Vine pages load as blank
+ https://bugs.webkit.org/show_bug.cgi?id=136655
+ rdar://problem/18281215
+
+ Reviewed by Michael Saboff.
+
+ If lastNode is something that is subject to DCE, then removing the Phantom's reference to something
+ that lastNode references means that the thing being referenced may no longer be kept alive for OSR.
+ Teach PhantomRemovalPhase that it's only safe to do this if lastNode is a Phantom. That's probably too
+ conservative, but that's fine since this is mainly just an optimization to make the IR sane to read and
+ reasonably compact; it's OK if we miss cases here.
+
+ * dfg/DFGPhantomRemovalPhase.cpp:
+ (JSC::DFG::PhantomRemovalPhase::run):
+ * tests/stress/remove-phantom-after-setlocal.js: Added.
+
</ins><span class="cx"> 2014-09-11 Bear Travis <betravis@adobe.com>
</span><span class="cx">
</span><span class="cx"> [CSS Font Loading] Enable CSS Font Loading on Mac
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoredfgDFGPhantomRemovalPhasecpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/dfg/DFGPhantomRemovalPhase.cpp (173533 => 173534)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/dfg/DFGPhantomRemovalPhase.cpp 2014-09-11 19:57:33 UTC (rev 173533)
+++ trunk/Source/JavaScriptCore/dfg/DFGPhantomRemovalPhase.cpp 2014-09-11 20:04:38 UTC (rev 173534)
</span><span class="lines">@@ -93,13 +93,17 @@
</span><span class="cx">
</span><span class="cx"> unsigned sourceIndex = 0;
</span><span class="cx"> unsigned targetIndex = 0;
</span><del>- Node* lastNode = nullptr;
</del><span class="cx"> while (sourceIndex < block->size()) {
</span><span class="cx"> Node* node = block->at(sourceIndex++);
</span><span class="cx"> switch (node->op()) {
</span><span class="cx"> case Phantom: {
</span><del>- if (lastNode && (lastNode->origin.forExit != node->origin.forExit || (lastNode->flags() & NodeHasVarArgs)))
- lastNode = nullptr;
</del><ins>+ Node* lastNode = nullptr;
+ if (sourceIndex > 1) {
+ lastNode = block->at(sourceIndex - 2);
+ if (lastNode->op() != Phantom
+ || lastNode->origin.forExit != node->origin.forExit)
+ lastNode = nullptr;
+ }
</ins><span class="cx"> for (unsigned i = 0; i < AdjacencyList::Size; ++i) {
</span><span class="cx"> Edge edge = node->children.child(i);
</span><span class="cx"> if (!edge)
</span><span class="lines">@@ -161,7 +165,7 @@
</span><span class="cx"> default:
</span><span class="cx"> break;
</span><span class="cx"> }
</span><del>- lastNode = node;
</del><ins>+
</ins><span class="cx"> block->at(targetIndex++) = node;
</span><span class="cx"> }
</span><span class="cx"> block->resize(targetIndex);
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoretestsstressremovephantomaftersetlocaljs"></a>
<div class="addfile"><h4>Added: trunk/Source/JavaScriptCore/tests/stress/remove-phantom-after-setlocal.js (0 => 173534)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/tests/stress/remove-phantom-after-setlocal.js (rev 0)
+++ trunk/Source/JavaScriptCore/tests/stress/remove-phantom-after-setlocal.js 2014-09-11 20:04:38 UTC (rev 173534)
</span><span class="lines">@@ -0,0 +1,18 @@
</span><ins>+var constant = {};
+
+function foo(o) {
+ var v = o.f;
+ return v === constant;
+}
+
+noInline(foo);
+
+for (var i = 0; i < 1000000; ++i) {
+ var result = foo({f:null});
+ if (result !== false)
+ throw "Error: bogus result in loop";
+}
+
+var result = foo({f:constant});
+if (result !== true)
+ throw "Error: bogus result at end";
</ins></span></pre>
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