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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/171662">171662</a></dd>
<dt>Author</dt> <dd>fpizlo@apple.com</dd>
<dt>Date</dt> <dd>2014-07-27 16:35:32 -0700 (Sun, 27 Jul 2014)</dd>
</dl>
<h3>Log Message</h3>
<pre>[REGRESSION][ftlopt merge][32-bit] stress/prune-multi-put-by-offset-replace-or-transition-variant.js.dfg-eager hits an assertion in SpeculativeJIT::silentSavePlanForGPR
https://bugs.webkit.org/show_bug.cgi?id=135323
Reviewed by Oliver Hunt.
SpeculativeJIT::silentSavePlanForGPR likes to believe that if a node is a constant,
then it's a constant that can be represented using that node's current DataFormat.
This doesn't work if the constant had been filled as a JSValue, and then one of the
fillSpeculateBlah() methods had speculated that it's of some type that the constant
isn't. Unless fillSpeculateBlah() specifically defends against this case, we'll have
a constant that claims to have a contradictory data format.
This patch fixes such a bug in the 32-bit fillSpeculateCell(). The 64-bit
fillSpeculateCell() appears to not have this bug, but I added a similar defense
mechanism anyway just in case, since this is one of those mistakes that keeps
reappearing.
* dfg/DFGSpeculativeJIT.cpp:
(JSC::DFG::SpeculativeJIT::silentSavePlanForGPR):
* dfg/DFGSpeculativeJIT32_64.cpp:
(JSC::DFG::SpeculativeJIT::fillSpeculateCell):
* dfg/DFGSpeculativeJIT64.cpp:
(JSC::DFG::SpeculativeJIT::fillSpeculateCell):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoredfgDFGSpeculativeJITcpp">trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoredfgDFGSpeculativeJIT32_64cpp">trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT32_64.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoredfgDFGSpeculativeJIT64cpp">trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT64.cpp</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (171661 => 171662)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2014-07-27 23:33:10 UTC (rev 171661)
+++ trunk/Source/JavaScriptCore/ChangeLog 2014-07-27 23:35:32 UTC (rev 171662)
</span><span class="lines">@@ -1,5 +1,31 @@
</span><span class="cx"> 2014-07-27 Filip Pizlo <fpizlo@apple.com>
</span><span class="cx">
</span><ins>+ [REGRESSION][ftlopt merge][32-bit] stress/prune-multi-put-by-offset-replace-or-transition-variant.js.dfg-eager hits an assertion in SpeculativeJIT::silentSavePlanForGPR
+ https://bugs.webkit.org/show_bug.cgi?id=135323
+
+ Reviewed by Oliver Hunt.
+
+ SpeculativeJIT::silentSavePlanForGPR likes to believe that if a node is a constant,
+ then it's a constant that can be represented using that node's current DataFormat.
+ This doesn't work if the constant had been filled as a JSValue, and then one of the
+ fillSpeculateBlah() methods had speculated that it's of some type that the constant
+ isn't. Unless fillSpeculateBlah() specifically defends against this case, we'll have
+ a constant that claims to have a contradictory data format.
+
+ This patch fixes such a bug in the 32-bit fillSpeculateCell(). The 64-bit
+ fillSpeculateCell() appears to not have this bug, but I added a similar defense
+ mechanism anyway just in case, since this is one of those mistakes that keeps
+ reappearing.
+
+ * dfg/DFGSpeculativeJIT.cpp:
+ (JSC::DFG::SpeculativeJIT::silentSavePlanForGPR):
+ * dfg/DFGSpeculativeJIT32_64.cpp:
+ (JSC::DFG::SpeculativeJIT::fillSpeculateCell):
+ * dfg/DFGSpeculativeJIT64.cpp:
+ (JSC::DFG::SpeculativeJIT::fillSpeculateCell):
+
+2014-07-27 Filip Pizlo <fpizlo@apple.com>
+
</ins><span class="cx"> Merge r170090, r170092, r170129, r170141, r170161, r170215, r170275, r170375, r170376, r170382, r170383, r170399, r170436, r170489, r170490, r170556 from ftlopt.
</span><span class="cx">
</span><span class="cx"> This fixes the previous mismerge and adds test coverage for the thing that went wrong.
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoredfgDFGSpeculativeJITcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT.cpp (171661 => 171662)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT.cpp 2014-07-27 23:33:10 UTC (rev 171661)
+++ trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT.cpp 2014-07-27 23:35:32 UTC (rev 171662)
</span><span class="lines">@@ -343,6 +343,7 @@
</span><span class="cx"> } else if (registerFormat == DataFormatCell) {
</span><span class="cx"> ASSERT(info.gpr() == source);
</span><span class="cx"> if (node->hasConstant()) {
</span><ins>+ DFG_ASSERT(m_jit.graph(), m_currentNode, node->isCellConstant());
</ins><span class="cx"> node->asCell(); // To get the assertion.
</span><span class="cx"> fillAction = SetCellConstant;
</span><span class="cx"> } else {
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoredfgDFGSpeculativeJIT32_64cpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT32_64.cpp (171661 => 171662)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT32_64.cpp 2014-07-27 23:33:10 UTC (rev 171661)
+++ trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT32_64.cpp 2014-07-27 23:35:32 UTC (rev 171662)
</span><span class="lines">@@ -867,6 +867,15 @@
</span><span class="cx"> m_interpreter.filter(value, SpecCell);
</span><span class="cx"> VirtualRegister virtualRegister = edge->virtualRegister();
</span><span class="cx"> GenerationInfo& info = generationInfoFromVirtualRegister(virtualRegister);
</span><ins>+
+ if (edge->hasConstant() && !edge->isCellConstant()) {
+ // Protect the silent spill/fill logic by failing early. If we "speculate" on
+ // the constant then the silent filler may think that we have a cell and a
+ // constant, so it will try to fill this as an cell constant. Bad things will
+ // happen.
+ terminateSpeculativeExecution(Uncountable, JSValueRegs(), 0);
+ return allocate();
+ }
</ins><span class="cx">
</span><span class="cx"> switch (info.registerFormat()) {
</span><span class="cx"> case DataFormatNone: {
</span><span class="lines">@@ -878,13 +887,9 @@
</span><span class="cx"> if (edge->hasConstant()) {
</span><span class="cx"> JSValue jsValue = edge->asJSValue();
</span><span class="cx"> GPRReg gpr = allocate();
</span><del>- if (jsValue.isCell()) {
- m_gprs.retain(gpr, virtualRegister, SpillOrderConstant);
- m_jit.move(MacroAssembler::TrustedImmPtr(jsValue.asCell()), gpr);
- info.fillCell(*m_stream, gpr);
- return gpr;
- }
- terminateSpeculativeExecution(Uncountable, JSValueRegs(), 0);
</del><ins>+ m_gprs.retain(gpr, virtualRegister, SpillOrderConstant);
+ m_jit.move(MacroAssembler::TrustedImmPtr(jsValue.asCell()), gpr);
+ info.fillCell(*m_stream, gpr);
</ins><span class="cx"> return gpr;
</span><span class="cx"> }
</span><span class="cx">
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoredfgDFGSpeculativeJIT64cpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT64.cpp (171661 => 171662)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT64.cpp 2014-07-27 23:33:10 UTC (rev 171661)
+++ trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT64.cpp 2014-07-27 23:35:32 UTC (rev 171662)
</span><span class="lines">@@ -995,19 +995,21 @@
</span><span class="cx"> VirtualRegister virtualRegister = edge->virtualRegister();
</span><span class="cx"> GenerationInfo& info = generationInfoFromVirtualRegister(virtualRegister);
</span><span class="cx">
</span><ins>+ if (edge->hasConstant() && !edge->isCellConstant()) {
+ // Better to fail early on constants.
+ terminateSpeculativeExecution(Uncountable, JSValueRegs(), 0);
+ return allocate();
+ }
+
</ins><span class="cx"> switch (info.registerFormat()) {
</span><span class="cx"> case DataFormatNone: {
</span><span class="cx"> GPRReg gpr = allocate();
</span><span class="cx">
</span><span class="cx"> if (edge->hasConstant()) {
</span><span class="cx"> JSValue jsValue = edge->asJSValue();
</span><del>- if (jsValue.isCell()) {
- m_gprs.retain(gpr, virtualRegister, SpillOrderConstant);
- m_jit.move(MacroAssembler::TrustedImm64(JSValue::encode(jsValue)), gpr);
- info.fillJSValue(*m_stream, gpr, DataFormatJSCell);
- return gpr;
- }
- terminateSpeculativeExecution(Uncountable, JSValueRegs(), 0);
</del><ins>+ m_gprs.retain(gpr, virtualRegister, SpillOrderConstant);
+ m_jit.move(MacroAssembler::TrustedImm64(JSValue::encode(jsValue)), gpr);
+ info.fillJSValue(*m_stream, gpr, DataFormatJSCell);
</ins><span class="cx"> return gpr;
</span><span class="cx"> }
</span><span class="cx">
</span></span></pre>
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