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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/187028">187028</a></dd>
<dt>Author</dt> <dd>fpizlo@apple.com</dd>
<dt>Date</dt> <dd>2015-07-20 12:04:19 -0700 (Mon, 20 Jul 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>REGRESSION(186691): OSR entry is broken on loop headers that have no live variables
https://bugs.webkit.org/show_bug.cgi?id=147074
rdar://problem/21869970
Reviewed by Michael Saboff.
The OSR entry must-handle block/value widening introduced in <a href="http://trac.webkit.org/projects/webkit/changeset/186691">r186691</a> would cause the
CFA to reexecute if it caused any live local variables to change value. But this fails
if the must-handle block has no live local variables, and the entry block otherwise
appears to be unreachable.
This fixes the bug by having the change detection include whether the block hadn't been
visited in addition to whether any local variable values got widened.
This is a ~4% speed-up on SunSpider in browser.
* dfg/DFGCFAPhase.cpp:
(JSC::DFG::CFAPhase::run):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoredfgDFGCFAPhasecpp">trunk/Source/JavaScriptCore/dfg/DFGCFAPhase.cpp</a></li>
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<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (187027 => 187028)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2015-07-20 18:51:41 UTC (rev 187027)
+++ trunk/Source/JavaScriptCore/ChangeLog 2015-07-20 19:04:19 UTC (rev 187028)
</span><span class="lines">@@ -1,3 +1,24 @@
</span><ins>+2015-07-18 Filip Pizlo <fpizlo@apple.com>
+
+ REGRESSION(186691): OSR entry is broken on loop headers that have no live variables
+ https://bugs.webkit.org/show_bug.cgi?id=147074
+ rdar://problem/21869970
+
+ Reviewed by Michael Saboff.
+
+ The OSR entry must-handle block/value widening introduced in r186691 would cause the
+ CFA to reexecute if it caused any live local variables to change value. But this fails
+ if the must-handle block has no live local variables, and the entry block otherwise
+ appears to be unreachable.
+
+ This fixes the bug by having the change detection include whether the block hadn't been
+ visited in addition to whether any local variable values got widened.
+
+ This is a ~4% speed-up on SunSpider in browser.
+
+ * dfg/DFGCFAPhase.cpp:
+ (JSC::DFG::CFAPhase::run):
+
</ins><span class="cx"> 2015-07-20 Mark Lam <mark.lam@apple.com>
</span><span class="cx">
</span><span class="cx"> Rollout r187020 and r187021: breaks JSC API tests on debug builds.
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoredfgDFGCFAPhasecpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/dfg/DFGCFAPhase.cpp (187027 => 187028)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/dfg/DFGCFAPhase.cpp 2015-07-20 18:51:41 UTC (rev 187027)
+++ trunk/Source/JavaScriptCore/dfg/DFGCFAPhase.cpp 2015-07-20 19:04:19 UTC (rev 187028)
</span><span class="lines">@@ -107,7 +107,7 @@
</span><span class="cx"> m_graph, resultFor(node->variableAccessData()->flushFormat()));
</span><span class="cx"> }
</span><span class="cx">
</span><del>- if (changed) {
</del><ins>+ if (changed || !block->cfaHasVisited) {
</ins><span class="cx"> m_changed = true;
</span><span class="cx"> block->cfaShouldRevisit = true;
</span><span class="cx"> }
</span></span></pre>
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