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<dl class="meta">
<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/191930">191930</a></dd>
<dt>Author</dt> <dd>sbarati@apple.com</dd>
<dt>Date</dt> <dd>2015-11-02 17:19:17 -0800 (Mon, 02 Nov 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>Wrong value recovery for DFG try/catch with a getter that throws during an IC miss
https://bugs.webkit.org/show_bug.cgi?id=150760
Reviewed by Geoffrey Garen.
This is related to using PhantomLocal instead of Flush as
the liveness preservation mechanism for live catch variables.
I'm temporarily switching things back to Flush. This will be a
performance hit for try/catch in the DFG. Landing this patch,
though, will allow me to land try/catch in the FTL. It also
makes try/catch in the DFG sound. I have opened another
bug to further investigate using PhantomLocal as the
liveness preservation mechanism: https://bugs.webkit.org/show_bug.cgi?id=150824
* dfg/DFGLiveCatchVariablePreservationPhase.cpp:
(JSC::DFG::LiveCatchVariablePreservationPhase::handleBlock):
* tests/stress/dfg-try-catch-wrong-value-recovery-on-ic-miss.js: Added.
(assert):
(let.oThrow.get f):
(let.o2.get f):
(foo):
(f):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoredfgDFGLiveCatchVariablePreservationPhasecpp">trunk/Source/JavaScriptCore/dfg/DFGLiveCatchVariablePreservationPhase.cpp</a></li>
</ul>
<h3>Added Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoretestsstressdfgtrycatchwrongvaluerecoveryonicmissjs">trunk/Source/JavaScriptCore/tests/stress/dfg-try-catch-wrong-value-recovery-on-ic-miss.js</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (191929 => 191930)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2015-11-03 01:15:51 UTC (rev 191929)
+++ trunk/Source/JavaScriptCore/ChangeLog 2015-11-03 01:19:17 UTC (rev 191930)
</span><span class="lines">@@ -1,3 +1,28 @@
</span><ins>+2015-11-02 Saam barati <sbarati@apple.com>
+
+ Wrong value recovery for DFG try/catch with a getter that throws during an IC miss
+ https://bugs.webkit.org/show_bug.cgi?id=150760
+
+ Reviewed by Geoffrey Garen.
+
+ This is related to using PhantomLocal instead of Flush as
+ the liveness preservation mechanism for live catch variables.
+ I'm temporarily switching things back to Flush. This will be a
+ performance hit for try/catch in the DFG. Landing this patch,
+ though, will allow me to land try/catch in the FTL. It also
+ makes try/catch in the DFG sound. I have opened another
+ bug to further investigate using PhantomLocal as the
+ liveness preservation mechanism: https://bugs.webkit.org/show_bug.cgi?id=150824
+
+ * dfg/DFGLiveCatchVariablePreservationPhase.cpp:
+ (JSC::DFG::LiveCatchVariablePreservationPhase::handleBlock):
+ * tests/stress/dfg-try-catch-wrong-value-recovery-on-ic-miss.js: Added.
+ (assert):
+ (let.oThrow.get f):
+ (let.o2.get f):
+ (foo):
+ (f):
+
</ins><span class="cx"> 2015-11-02 Andy Estes <aestes@apple.com>
</span><span class="cx">
</span><span class="cx"> [Cocoa] Add tvOS and watchOS to SUPPORTED_PLATFORMS
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoredfgDFGLiveCatchVariablePreservationPhasecpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/dfg/DFGLiveCatchVariablePreservationPhase.cpp (191929 => 191930)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/dfg/DFGLiveCatchVariablePreservationPhase.cpp 2015-11-03 01:15:51 UTC (rev 191929)
+++ trunk/Source/JavaScriptCore/dfg/DFGLiveCatchVariablePreservationPhase.cpp 2015-11-03 01:19:17 UTC (rev 191930)
</span><span class="lines">@@ -118,7 +118,7 @@
</span><span class="cx"> variableAccessData = newVariableAccessData(operand);
</span><span class="cx">
</span><span class="cx"> insertionSet.insertNode(i, SpecNone,
</span><del>- PhantomLocal, node->origin, OpInfo(variableAccessData));
</del><ins>+ Flush, node->origin, OpInfo(variableAccessData));
</ins><span class="cx"> }
</span><span class="cx"> }
</span><span class="cx">
</span><span class="lines">@@ -127,10 +127,10 @@
</span><span class="cx"> }
</span><span class="cx"> }
</span><span class="cx">
</span><del>- // Insert PhantomLocals for everything at the end of the block.
</del><ins>+ // Insert Flush for everything at the end of the block.
</ins><span class="cx"> {
</span><span class="cx"> NodeOrigin origin = block->at(block->size() - 1)->origin;
</span><del>- auto insertPhantomLocalAtEnd = [&] (VirtualRegister operand, bool alwaysInsert) {
</del><ins>+ auto preserveLivenessAtEndOfBlock = [&] (VirtualRegister operand, bool alwaysInsert) {
</ins><span class="cx"> if ((operand.isLocal() && m_currentBlockLiveness.get(operand.toLocal()))
</span><span class="cx"> || operand.isArgument()
</span><span class="cx"> || alwaysInsert) {
</span><span class="lines">@@ -141,14 +141,14 @@
</span><span class="cx"> currentBlockAccessData.operand(operand) = accessData;
</span><span class="cx">
</span><span class="cx"> insertionSet.insertNode(block->size(), SpecNone,
</span><del>- PhantomLocal, origin, OpInfo(accessData));
</del><ins>+ Flush, origin, OpInfo(accessData));
</ins><span class="cx"> }
</span><span class="cx"> };
</span><span class="cx"> for (unsigned local = 0; local < block->variablesAtTail.numberOfLocals(); local++)
</span><del>- insertPhantomLocalAtEnd(virtualRegisterForLocal(local), false);
</del><ins>+ preserveLivenessAtEndOfBlock(virtualRegisterForLocal(local), false);
</ins><span class="cx"> for (InlineCallFrame* inlineCallFrame : seenInlineCallFrames)
</span><del>- insertPhantomLocalAtEnd(VirtualRegister(inlineCallFrame->stackOffset + CallFrame::thisArgumentOffset()), true);
- insertPhantomLocalAtEnd(VirtualRegister(CallFrame::thisArgumentOffset()), true);
</del><ins>+ preserveLivenessAtEndOfBlock(VirtualRegister(inlineCallFrame->stackOffset + CallFrame::thisArgumentOffset()), true);
+ preserveLivenessAtEndOfBlock(VirtualRegister(CallFrame::thisArgumentOffset()), true);
</ins><span class="cx"> }
</span><span class="cx"> }
</span><span class="cx">
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoretestsstressdfgtrycatchwrongvaluerecoveryonicmissjs"></a>
<div class="addfile"><h4>Added: trunk/Source/JavaScriptCore/tests/stress/dfg-try-catch-wrong-value-recovery-on-ic-miss.js (0 => 191930)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/tests/stress/dfg-try-catch-wrong-value-recovery-on-ic-miss.js (rev 0)
+++ trunk/Source/JavaScriptCore/tests/stress/dfg-try-catch-wrong-value-recovery-on-ic-miss.js 2015-11-03 01:19:17 UTC (rev 191930)
</span><span class="lines">@@ -0,0 +1,50 @@
</span><ins>+function assert(b) {
+ if (!b)
+ throw new Error("bad value")
+}
+noInline(assert);
+
+let oThrow = {
+ x: 20,
+ y: 40,
+ z: 50,
+ get f() { throw new Error("Hello World!"); }
+};
+
+let o1 = {
+ x: 20,
+ f: 40
+};
+
+let o2 = {
+ x: 20,
+ y: 50,
+ f: 500,
+ get f() { return 20; }
+};
+
+function foo(f) {
+ let o = f();
+ try {
+ o = o.f;
+ } catch(e) {
+ assert(o === oThrow); // Make sure this is not undefined.
+ }
+}
+noInline(foo);
+
+let i;
+let flag = false;
+function f() {
+ if (flag)
+ return oThrow;
+ if (i % 2)
+ return o1;
+ return o2;
+}
+noInline(f);
+for (i = 0; i < 10000; i++) {
+ foo(f);
+}
+flag = true;
+foo(f);
</ins></span></pre>
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