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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/202093">202093</a></dd>
<dt>Author</dt> <dd>keith_miller@apple.com</dd>
<dt>Date</dt> <dd>2016-06-15 09:39:19 -0700 (Wed, 15 Jun 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>DFGByteCodeParser should be able to infer a property is unset from the Baseline inline cache.
https://bugs.webkit.org/show_bug.cgi?id=158774
Reviewed by Filip Pizlo.
This patch allows the DFGByteCodeParser to speculatively convert a property access into a
constant if that access was always a miss in the Baseline inline cache. This patch does
not add support for MultiGetByOffset and unset properties. That functionality will come
a future patch.
* bytecode/ComplexGetStatus.cpp:
(JSC::ComplexGetStatus::computeFor):
* bytecode/GetByIdStatus.cpp:
(JSC::GetByIdStatus::computeForStubInfoWithoutExitSiteFeedback):
* bytecode/GetByIdVariant.h:
(JSC::GetByIdVariant::isPropertyUnset):
* bytecode/PutByIdVariant.h:
(JSC::PutByIdVariant::isPropertyUnset):
* dfg/DFGByteCodeParser.cpp:
(JSC::DFG::ByteCodeParser::load):
(JSC::DFG::ByteCodeParser::handleGetById):
* tests/stress/undefined-access-then-self-change.js: Added.
(foo):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCorebytecodeComplexGetStatuscpp">trunk/Source/JavaScriptCore/bytecode/ComplexGetStatus.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCorebytecodeGetByIdStatuscpp">trunk/Source/JavaScriptCore/bytecode/GetByIdStatus.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCorebytecodeGetByIdVarianth">trunk/Source/JavaScriptCore/bytecode/GetByIdVariant.h</a></li>
<li><a href="#trunkSourceJavaScriptCorebytecodePutByIdVarianth">trunk/Source/JavaScriptCore/bytecode/PutByIdVariant.h</a></li>
<li><a href="#trunkSourceJavaScriptCoredfgDFGByteCodeParsercpp">trunk/Source/JavaScriptCore/dfg/DFGByteCodeParser.cpp</a></li>
</ul>
<h3>Added Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoretestsstressundefinedaccessthenselfchangejs">trunk/Source/JavaScriptCore/tests/stress/undefined-access-then-self-change.js</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (202092 => 202093)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2016-06-15 16:30:00 UTC (rev 202092)
+++ trunk/Source/JavaScriptCore/ChangeLog 2016-06-15 16:39:19 UTC (rev 202093)
</span><span class="lines">@@ -1,3 +1,29 @@
</span><ins>+2016-06-15 Keith Miller <keith_miller@apple.com>
+
+ DFGByteCodeParser should be able to infer a property is unset from the Baseline inline cache.
+ https://bugs.webkit.org/show_bug.cgi?id=158774
+
+ Reviewed by Filip Pizlo.
+
+ This patch allows the DFGByteCodeParser to speculatively convert a property access into a
+ constant if that access was always a miss in the Baseline inline cache. This patch does
+ not add support for MultiGetByOffset and unset properties. That functionality will come
+ a future patch.
+
+ * bytecode/ComplexGetStatus.cpp:
+ (JSC::ComplexGetStatus::computeFor):
+ * bytecode/GetByIdStatus.cpp:
+ (JSC::GetByIdStatus::computeForStubInfoWithoutExitSiteFeedback):
+ * bytecode/GetByIdVariant.h:
+ (JSC::GetByIdVariant::isPropertyUnset):
+ * bytecode/PutByIdVariant.h:
+ (JSC::PutByIdVariant::isPropertyUnset):
+ * dfg/DFGByteCodeParser.cpp:
+ (JSC::DFG::ByteCodeParser::load):
+ (JSC::DFG::ByteCodeParser::handleGetById):
+ * tests/stress/undefined-access-then-self-change.js: Added.
+ (foo):
+
</ins><span class="cx"> 2016-06-15 Yusuke Suzuki <utatane.tea@gmail.com>
</span><span class="cx">
</span><span class="cx"> [JSC] Move calling convention flags to WTF
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorebytecodeComplexGetStatuscpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/bytecode/ComplexGetStatus.cpp (202092 => 202093)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/bytecode/ComplexGetStatus.cpp 2016-06-15 16:30:00 UTC (rev 202092)
+++ trunk/Source/JavaScriptCore/bytecode/ComplexGetStatus.cpp 2016-06-15 16:39:19 UTC (rev 202093)
</span><span class="lines">@@ -57,13 +57,12 @@
</span><span class="cx"> result.m_conditionSet.numberOfConditionsWithKind(PropertyCondition::Presence);
</span><span class="cx"> RELEASE_ASSERT(numberOfSlotBases <= 1);
</span><span class="cx"> if (!numberOfSlotBases) {
</span><del>- // Currently we don't support misses. That's a bummer.
- // FIXME: https://bugs.webkit.org/show_bug.cgi?id=133052
- return takesSlowPath();
</del><ins>+ ASSERT(result.m_offset == invalidOffset);
+ return result;
</ins><span class="cx"> }
</span><span class="cx"> ObjectPropertyCondition base = result.m_conditionSet.slotBaseCondition();
</span><span class="cx"> ASSERT(base.kind() == PropertyCondition::Presence);
</span><del>-
</del><ins>+
</ins><span class="cx"> result.m_offset = base.offset();
</span><span class="cx"> } else
</span><span class="cx"> result.m_offset = headStructure->getConcurrently(uid);
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorebytecodeGetByIdStatuscpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/bytecode/GetByIdStatus.cpp (202092 => 202093)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/bytecode/GetByIdStatus.cpp 2016-06-15 16:30:00 UTC (rev 202092)
+++ trunk/Source/JavaScriptCore/bytecode/GetByIdStatus.cpp 2016-06-15 16:39:19 UTC (rev 202093)
</span><span class="lines">@@ -218,7 +218,8 @@
</span><span class="cx">
</span><span class="cx"> switch (access.type()) {
</span><span class="cx"> case AccessCase::Load:
</span><del>- case AccessCase::GetGetter: {
</del><ins>+ case AccessCase::GetGetter:
+ case AccessCase::Miss: {
</ins><span class="cx"> break;
</span><span class="cx"> }
</span><span class="cx"> case AccessCase::IntrinsicGetter: {
</span><span class="lines">@@ -238,7 +239,8 @@
</span><span class="cx"> // future. https://bugs.webkit.org/show_bug.cgi?id=133052
</span><span class="cx"> return GetByIdStatus(slowPathState, true);
</span><span class="cx"> } }
</span><del>-
</del><ins>+
+ ASSERT((AccessCase::Miss == access.type()) == (access.offset() == invalidOffset));
</ins><span class="cx"> GetByIdVariant variant(
</span><span class="cx"> StructureSet(structure), complexGetStatus.offset(),
</span><span class="cx"> complexGetStatus.conditionSet(), WTFMove(callLinkStatus),
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorebytecodeGetByIdVarianth"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/bytecode/GetByIdVariant.h (202092 => 202093)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/bytecode/GetByIdVariant.h 2016-06-15 16:30:00 UTC (rev 202092)
+++ trunk/Source/JavaScriptCore/bytecode/GetByIdVariant.h 2016-06-15 16:39:19 UTC (rev 202093)
</span><span class="lines">@@ -64,6 +64,8 @@
</span><span class="cx"> JSFunction* intrinsicFunction() const { return m_intrinsicFunction; }
</span><span class="cx"> Intrinsic intrinsic() const { return m_intrinsicFunction ? m_intrinsicFunction->intrinsic() : NoIntrinsic; }
</span><span class="cx">
</span><ins>+ bool isPropertyUnset() const { return offset() == invalidOffset; }
+
</ins><span class="cx"> bool attemptToMerge(const GetByIdVariant& other);
</span><span class="cx">
</span><span class="cx"> void dump(PrintStream&) const;
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorebytecodePutByIdVarianth"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/bytecode/PutByIdVariant.h (202092 => 202093)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/bytecode/PutByIdVariant.h 2016-06-15 16:30:00 UTC (rev 202092)
+++ trunk/Source/JavaScriptCore/bytecode/PutByIdVariant.h 2016-06-15 16:39:19 UTC (rev 202093)
</span><span class="lines">@@ -112,7 +112,10 @@
</span><span class="cx">
</span><span class="cx"> // We don't support intrinsics for Setters (it would be sweet if we did) but we need this for templated helpers.
</span><span class="cx"> Intrinsic intrinsic() const { return NoIntrinsic; }
</span><del>-
</del><ins>+
+ // This is needed for templated helpers.
+ bool isPropertyUnset() const { return false; }
+
</ins><span class="cx"> PropertyOffset offset() const
</span><span class="cx"> {
</span><span class="cx"> ASSERT(isSet());
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoredfgDFGByteCodeParsercpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/dfg/DFGByteCodeParser.cpp (202092 => 202093)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/dfg/DFGByteCodeParser.cpp 2016-06-15 16:30:00 UTC (rev 202092)
+++ trunk/Source/JavaScriptCore/dfg/DFGByteCodeParser.cpp 2016-06-15 16:39:19 UTC (rev 202093)
</span><span class="lines">@@ -3008,11 +3008,11 @@
</span><span class="cx"> Structure* structure = base->constant()->structure();
</span><span class="cx"> if (!structure->dfgShouldWatch()) {
</span><span class="cx"> if (!variant.conditionSet().isEmpty()) {
</span><del>- // This means that we're loading from a prototype. We expect the base not to have the
- // property. We can only use ObjectPropertyCondition if all of the structures in the
- // variant.structureSet() agree on the prototype (it would be hilariously rare if they
- // didn't). Note that we are relying on structureSet() having at least one element. That
- // will always be true here because of how GetByIdStatus/PutByIdStatus work.
</del><ins>+ // This means that we're loading from a prototype or we have a property miss. We expect
+ // the base not to have the property. We can only use ObjectPropertyCondition if all of
+ // the structures in the variant.structureSet() agree on the prototype (it would be
+ // hilariously rare if they didn't). Note that we are relying on structureSet() having
+ // at least one element. That will always be true here because of how GetByIdStatus/PutByIdStatus work.
</ins><span class="cx"> JSObject* prototype = variant.structureSet()[0]->storedPrototypeObject();
</span><span class="cx"> bool allAgree = true;
</span><span class="cx"> for (unsigned i = 1; i < variant.structureSet().size(); ++i) {
</span><span class="lines">@@ -3049,7 +3049,13 @@
</span><span class="cx">
</span><span class="cx"> if (needStructureCheck)
</span><span class="cx"> addToGraph(CheckStructure, OpInfo(m_graph.addStructureSet(variant.structureSet())), base);
</span><del>-
</del><ins>+
+ if (variant.isPropertyUnset()) {
+ if (m_graph.watchConditions(variant.conditionSet()))
+ return jsConstant(jsUndefined());
+ return nullptr;
+ }
+
</ins><span class="cx"> SpeculatedType loadPrediction;
</span><span class="cx"> NodeType loadOp;
</span><span class="cx"> if (variant.callLinkStatus() || variant.intrinsic() != NoIntrinsic) {
</span><span class="lines">@@ -3144,7 +3150,7 @@
</span><span class="cx"> // optimal, if there is some rarely executed case in the chain that requires a lot
</span><span class="cx"> // of checks and those checks are not watchpointable.
</span><span class="cx"> for (const GetByIdVariant& variant : getByIdStatus.variants()) {
</span><del>- if (variant.intrinsic() != NoIntrinsic) {
</del><ins>+ if (variant.intrinsic() != NoIntrinsic || variant.isPropertyUnset()) {
</ins><span class="cx"> set(VirtualRegister(destinationOperand),
</span><span class="cx"> addToGraph(getById, OpInfo(identifierNumber), OpInfo(prediction), base));
</span><span class="cx"> return;
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoretestsstressundefinedaccessthenselfchangejs"></a>
<div class="addfile"><h4>Added: trunk/Source/JavaScriptCore/tests/stress/undefined-access-then-self-change.js (0 => 202093)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/tests/stress/undefined-access-then-self-change.js (rev 0)
+++ trunk/Source/JavaScriptCore/tests/stress/undefined-access-then-self-change.js 2016-06-15 16:39:19 UTC (rev 202093)
</span><span class="lines">@@ -0,0 +1,18 @@
</span><ins>+function foo(o) {
+ return o.f;
+}
+
+noInline(foo);
+
+var o = Object.create(null);
+
+for (var i = 0; i < 10000; ++i) {
+ var result = foo(o);
+ if (result !== void 0)
+ throw "Error: bad result in loop: " + result;
+}
+
+o.f = 42
+var result = foo(o);
+if (result !== 42)
+ throw "Error: bad result at end: " + result;
</ins></span></pre>
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