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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/193964">193964</a></dd>
<dt>Author</dt> <dd>matthew_hanson@apple.com</dd>
<dt>Date</dt> <dd>2015-12-11 10:26:28 -0800 (Fri, 11 Dec 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>Merge <a href="http://trac.webkit.org/projects/webkit/changeset/193470">r193470</a>. rdar://problem/23849785</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#branchessafari601branchSourceJavaScriptCoreChangeLog">branches/safari-601-branch/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#branchessafari601branchSourceJavaScriptCoredfgDFGByteCodeParsercpp">branches/safari-601-branch/Source/JavaScriptCore/dfg/DFGByteCodeParser.cpp</a></li>
<li><a href="#branchessafari601branchSourceJavaScriptCoredfgDFGFixupPhasecpp">branches/safari-601-branch/Source/JavaScriptCore/dfg/DFGFixupPhase.cpp</a></li>
<li><a href="#branchessafari601branchSourceJavaScriptCoredfgDFGNodeh">branches/safari-601-branch/Source/JavaScriptCore/dfg/DFGNode.h</a></li>
<li><a href="#branchessafari601branchSourceJavaScriptCoredfgDFGWatchpointCollectionPhasecpp">branches/safari-601-branch/Source/JavaScriptCore/dfg/DFGWatchpointCollectionPhase.cpp</a></li>
<li><a href="#branchessafari601branchSourceJavaScriptCoreftlFTLLowerDFGToLLVMcpp">branches/safari-601-branch/Source/JavaScriptCore/ftl/FTLLowerDFGToLLVM.cpp</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="branchessafari601branchSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: branches/safari-601-branch/Source/JavaScriptCore/ChangeLog (193963 => 193964)</h4>
<pre class="diff"><span>
<span class="info">--- branches/safari-601-branch/Source/JavaScriptCore/ChangeLog 2015-12-11 18:26:25 UTC (rev 193963)
+++ branches/safari-601-branch/Source/JavaScriptCore/ChangeLog 2015-12-11 18:26:28 UTC (rev 193964)
</span><span class="lines">@@ -1,3 +1,68 @@
</span><ins>+2015-12-11 Matthew Hanson <matthew_hanson@apple.com>
+
+ Merge r193470. rdar://problem/23849785
+
+ 2015-12-04 Filip Pizlo <fpizlo@apple.com>
+
+ Having a bad time has a really awful time when it runs at the same time as the JIT
+ https://bugs.webkit.org/show_bug.cgi?id=151882
+ rdar://problem/23547038
+
+ Reviewed by Geoffrey Garen.
+
+ The DFG's use of watchpoints for havingABadTime goes back a long time. We introduced this feature
+ when we first introduced watchpoints. That left it open to a lot of bitrot. On top of that, this
+ code doesn't get tested much because having a bad time is not something that is really supposed to
+ happen.
+
+ Well, now I've got reports that it does happen - or at least, we know that it is because of
+ crashes in an assertion that could only be triggered if a bad time was had. In the meantime, we
+ added two new features without adequately testing havingABadTime: concurrent JIT and FTL.
+ Concurrency means that we have to worry about the havingABadTime watchpoint triggering during
+ compilation. FTL means that we have new code and new optimizations that needs to deal with this
+ feature correctly.
+
+ The bug can arise via race condition or just goofy profiling. As in the newly added test, we could
+ first profile an allocation thinking that it will allocate sane arrays. Then we might have a bad
+ time, and then compile that function with the FTL. The ByteCodeParser will represent the
+ allocation with a NewArray node that has a sane indexingType(). But when we go to lower the Node,
+ we observe that the Structure* that the JSGlobalObject tells us to use has a different indexing
+ type. This is a feature of havingABadTime that the DFG knew about, but the FTL didn't. The FTL
+ didn't know about it because we didn't have adequate tests, and this code rarely gets triggered in
+ the wild. So, the FTL had a silly assertion that the indexing types match. They absolutely don't
+ have to match.
+
+ There is another bug, a race condition, that remains even if we remove the bad assertion. We set
+ the havingABadTime watchpoint late in compilation, and we do it based on whether the watchpoint is
+ still OK. This means that we could parse a function before we have a bad time and then do
+ optimizations (for example in AbstractInterpreter) like proving that the structure set associated
+ with the value returned by the NewArray is the one with a sane indexing type. Then, after those
+ optimizations have already been done, we will go to set the watchpoint. But just as we are doing
+ this, we could haveABadTime on the main thread. Currently this sort of almost works because
+ having a bad time requires doing a GC, and we can't GC until the watchpoint collection phase. But
+ that feels too fragile. So, this phase moves the setting of the watchpoint to the FixupPhase. This
+ is consistent with our long-term goal of removing the WatchpointCollectionPhase. Moving this to
+ FixupPhase means that we set the watchpoint before doing any optimizations. So, if having a bad
+ time happens before the FixupPhase then all optimizations will agree that we're having a bad time
+ and so everything is fine; if we have a bad time after FixupPhase then we will cancel the
+ compilation anyway.
+
+ * dfg/DFGByteCodeParser.cpp:
+ (JSC::DFG::ByteCodeParser::handleConstantInternalFunction):
+ * dfg/DFGFixupPhase.cpp:
+ (JSC::DFG::FixupPhase::fixupNode):
+ (JSC::DFG::FixupPhase::watchHavingABadTime):
+ (JSC::DFG::FixupPhase::createToString):
+ * dfg/DFGNode.h:
+ (JSC::DFG::Node::hasIndexingType):
+ (JSC::DFG::Node::indexingType):
+ * dfg/DFGWatchpointCollectionPhase.cpp:
+ (JSC::DFG::WatchpointCollectionPhase::handle):
+ * ftl/FTLLowerDFGToLLVM.cpp:
+ (JSC::FTL::DFG::LowerDFGToLLVM::compileNewArray):
+ (JSC::FTL::DFG::LowerDFGToLLVM::compileNewArrayBuffer):
+ * tests/stress/ftl-has-a-bad-time.js: Added.
+
</ins><span class="cx"> 2015-12-04 Matthew Hanson <matthew_hanson@apple.com>
</span><span class="cx">
</span><span class="cx"> Merge r192190. rdar://problem/23732407
</span></span></pre></div>
<a id="branchessafari601branchSourceJavaScriptCoredfgDFGByteCodeParsercpp"></a>
<div class="modfile"><h4>Modified: branches/safari-601-branch/Source/JavaScriptCore/dfg/DFGByteCodeParser.cpp (193963 => 193964)</h4>
<pre class="diff"><span>
<span class="info">--- branches/safari-601-branch/Source/JavaScriptCore/dfg/DFGByteCodeParser.cpp 2015-12-11 18:26:25 UTC (rev 193963)
+++ branches/safari-601-branch/Source/JavaScriptCore/dfg/DFGByteCodeParser.cpp 2015-12-11 18:26:28 UTC (rev 193964)
</span><span class="lines">@@ -2195,13 +2195,6 @@
</span><span class="cx"> if (verbose)
</span><span class="cx"> dataLog(" Handling constant internal function ", JSValue(function), "\n");
</span><span class="cx">
</span><del>- // If we ever find that we have a lot of internal functions that we specialize for,
- // then we should probably have some sort of hashtable dispatch, or maybe even
- // dispatch straight through the MethodTable of the InternalFunction. But for now,
- // it seems that this case is hit infrequently enough, and the number of functions
- // we know about is small enough, that having just a linear cascade of if statements
- // is good enough.
-
</del><span class="cx"> if (function->classInfo() == ArrayConstructor::info()) {
</span><span class="cx"> if (function->globalObject() != m_inlineStackTop->m_codeBlock->globalObject())
</span><span class="cx"> return false;
</span></span></pre></div>
<a id="branchessafari601branchSourceJavaScriptCoredfgDFGFixupPhasecpp"></a>
<div class="modfile"><h4>Modified: branches/safari-601-branch/Source/JavaScriptCore/dfg/DFGFixupPhase.cpp (193963 => 193964)</h4>
<pre class="diff"><span>
<span class="info">--- branches/safari-601-branch/Source/JavaScriptCore/dfg/DFGFixupPhase.cpp 2015-12-11 18:26:25 UTC (rev 193963)
+++ branches/safari-601-branch/Source/JavaScriptCore/dfg/DFGFixupPhase.cpp 2015-12-11 18:26:28 UTC (rev 193964)
</span><span class="lines">@@ -853,6 +853,8 @@
</span><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> case NewArray: {
</span><ins>+ watchHavingABadTime(node);
+
</ins><span class="cx"> for (unsigned i = m_graph.varArgNumChildren(node); i--;) {
</span><span class="cx"> node->setIndexingType(
</span><span class="cx"> leastUpperBoundOfIndexingTypeAndType(
</span><span class="lines">@@ -890,6 +892,8 @@
</span><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> case NewTypedArray: {
</span><ins>+ watchHavingABadTime(node);
+
</ins><span class="cx"> if (node->child1()->shouldSpeculateInt32()) {
</span><span class="cx"> fixEdge<Int32Use>(node->child1());
</span><span class="cx"> node->clearFlags(NodeMustGenerate);
</span><span class="lines">@@ -899,6 +903,7 @@
</span><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> case NewArrayWithSize: {
</span><ins>+ watchHavingABadTime(node);
</ins><span class="cx"> fixEdge<Int32Use>(node->child1());
</span><span class="cx"> break;
</span><span class="cx"> }
</span><span class="lines">@@ -1323,6 +1328,20 @@
</span><span class="cx"> #endif
</span><span class="cx"> }
</span><span class="cx"> }
</span><ins>+
+ void watchHavingABadTime(Node* node)
+ {
+ JSGlobalObject* globalObject = m_graph.globalObjectFor(node->origin.semantic);
+
+ // If this global object is not having a bad time, watch it. We go down this path anytime the code
+ // does an array allocation. The types of array allocations may change if we start to have a bad
+ // time. It's easier to reason about this if we know that whenever the types change after we start
+ // optimizing, the code just gets thrown out. Doing this at FixupPhase is just early enough, since
+ // prior to this point nobody should have been doing optimizations based on the indexing type of
+ // the allocation.
+ if (!globalObject->isHavingABadTime())
+ m_graph.watchpoints().addLazily(globalObject->havingABadTimeWatchpoint());
+ }
</ins><span class="cx">
</span><span class="cx"> template<UseKind useKind>
</span><span class="cx"> void createToString(Node* node, Edge& edge)
</span></span></pre></div>
<a id="branchessafari601branchSourceJavaScriptCoredfgDFGNodeh"></a>
<div class="modfile"><h4>Modified: branches/safari-601-branch/Source/JavaScriptCore/dfg/DFGNode.h (193963 => 193964)</h4>
<pre class="diff"><span>
<span class="info">--- branches/safari-601-branch/Source/JavaScriptCore/dfg/DFGNode.h 2015-12-11 18:26:25 UTC (rev 193963)
+++ branches/safari-601-branch/Source/JavaScriptCore/dfg/DFGNode.h 2015-12-11 18:26:28 UTC (rev 193964)
</span><span class="lines">@@ -903,7 +903,15 @@
</span><span class="cx"> return false;
</span><span class="cx"> }
</span><span class="cx"> }
</span><del>-
</del><ins>+
+ // Return the indexing type that an array allocation *wants* to use. It may end up using a different
+ // type if we're having a bad time. You can determine the actual indexing type by asking the global
+ // object:
+ //
+ // m_graph.globalObjectFor(node->origin.semantic)->arrayStructureForIndexingTypeDuringAllocation(node->indexingType())
+ //
+ // This will give you a Structure*, and that will have some indexing type that may be different from
+ // the this one.
</ins><span class="cx"> IndexingType indexingType()
</span><span class="cx"> {
</span><span class="cx"> ASSERT(hasIndexingType());
</span></span></pre></div>
<a id="branchessafari601branchSourceJavaScriptCoredfgDFGWatchpointCollectionPhasecpp"></a>
<div class="modfile"><h4>Modified: branches/safari-601-branch/Source/JavaScriptCore/dfg/DFGWatchpointCollectionPhase.cpp (193963 => 193964)</h4>
<pre class="diff"><span>
<span class="info">--- branches/safari-601-branch/Source/JavaScriptCore/dfg/DFGWatchpointCollectionPhase.cpp 2015-12-11 18:26:25 UTC (rev 193963)
+++ branches/safari-601-branch/Source/JavaScriptCore/dfg/DFGWatchpointCollectionPhase.cpp 2015-12-11 18:26:28 UTC (rev 193964)
</span><span class="lines">@@ -97,13 +97,6 @@
</span><span class="cx"> }
</span><span class="cx"> break;
</span><span class="cx">
</span><del>- case NewArray:
- case NewArrayWithSize:
- case NewArrayBuffer:
- if (!globalObject()->isHavingABadTime() && !hasAnyArrayStorage(m_node->indexingType()))
- addLazily(globalObject()->havingABadTimeWatchpoint());
- break;
-
</del><span class="cx"> case VarInjectionWatchpoint:
</span><span class="cx"> addLazily(globalObject()->varInjectionWatchpoint());
</span><span class="cx"> break;
</span></span></pre></div>
<a id="branchessafari601branchSourceJavaScriptCoreftlFTLLowerDFGToLLVMcpp"></a>
<div class="modfile"><h4>Modified: branches/safari-601-branch/Source/JavaScriptCore/ftl/FTLLowerDFGToLLVM.cpp (193963 => 193964)</h4>
<pre class="diff"><span>
<span class="info">--- branches/safari-601-branch/Source/JavaScriptCore/ftl/FTLLowerDFGToLLVM.cpp 2015-12-11 18:26:25 UTC (rev 193963)
+++ branches/safari-601-branch/Source/JavaScriptCore/ftl/FTLLowerDFGToLLVM.cpp 2015-12-11 18:26:28 UTC (rev 193964)
</span><span class="lines">@@ -3278,9 +3278,7 @@
</span><span class="cx"> JSGlobalObject* globalObject = m_graph.globalObjectFor(m_node->origin.semantic);
</span><span class="cx"> Structure* structure = globalObject->arrayStructureForIndexingTypeDuringAllocation(
</span><span class="cx"> m_node->indexingType());
</span><del>-
- DFG_ASSERT(m_graph, m_node, structure->indexingType() == m_node->indexingType());
-
</del><ins>+
</ins><span class="cx"> if (!globalObject->isHavingABadTime() && !hasAnyArrayStorage(m_node->indexingType())) {
</span><span class="cx"> unsigned numElements = m_node->numChildren();
</span><span class="cx">
</span><span class="lines">@@ -3357,8 +3355,6 @@
</span><span class="cx"> Structure* structure = globalObject->arrayStructureForIndexingTypeDuringAllocation(
</span><span class="cx"> m_node->indexingType());
</span><span class="cx">
</span><del>- DFG_ASSERT(m_graph, m_node, structure->indexingType() == m_node->indexingType());
-
</del><span class="cx"> if (!globalObject->isHavingABadTime() && !hasAnyArrayStorage(m_node->indexingType())) {
</span><span class="cx"> unsigned numElements = m_node->numConstants();
</span><span class="cx">
</span></span></pre>
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