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<dl class="meta">
<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/172099">172099</a></dd>
<dt>Author</dt> <dd>akling@apple.com</dd>
<dt>Date</dt> <dd>2014-08-05 16:10:38 -0700 (Tue, 05 Aug 2014)</dd>
</dl>
<h3>Log Message</h3>
<pre>The JIT should cache property lookup misses.
<https://webkit.org/b/135578>
Source/JavaScriptCore:
Add support for inline caching of object properties that don't exist.
Previously we'd fall back to the C++ slow-path whenever a property was missing.
It's implemented as a simple GetById-style stub that returns jsUndefined() as
long as the Structure chain check passes.
10x speedup on the included microbenchmark.
Reviewed by Geoffrey Garen.
* jit/Repatch.cpp:
(JSC::toString):
(JSC::kindFor):
(JSC::generateByIdStub):
(JSC::tryCacheGetByID):
(JSC::patchJumpToGetByIdStub):
* runtime/PropertySlot.h:
(JSC::PropertySlot::isUnset):
LayoutTests:
Add a JS microbenchmark that accesses an undefined property in a hot loop.
Reviewed by Geoffrey Garen.
* js/regress/script-tests/undefined-property-access.js: Added.
(foo):
* js/regress/undefined-property-access-expected.txt: Added.
* js/regress/undefined-property-access.html: Added.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkLayoutTestsChangeLog">trunk/LayoutTests/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCorejitRepatchcpp">trunk/Source/JavaScriptCore/jit/Repatch.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoreruntimePropertySloth">trunk/Source/JavaScriptCore/runtime/PropertySlot.h</a></li>
</ul>
<h3>Added Paths</h3>
<ul>
<li><a href="#trunkLayoutTestsjsregressscripttestsundefinedpropertyaccessjs">trunk/LayoutTests/js/regress/script-tests/undefined-property-access.js</a></li>
<li><a href="#trunkLayoutTestsjsregressundefinedpropertyaccessexpectedtxt">trunk/LayoutTests/js/regress/undefined-property-access-expected.txt</a></li>
<li><a href="#trunkLayoutTestsjsregressundefinedpropertyaccesshtml">trunk/LayoutTests/js/regress/undefined-property-access.html</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkLayoutTestsChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/LayoutTests/ChangeLog (172098 => 172099)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/ChangeLog 2014-08-05 23:06:03 UTC (rev 172098)
+++ trunk/LayoutTests/ChangeLog 2014-08-05 23:10:38 UTC (rev 172099)
</span><span class="lines">@@ -1,3 +1,17 @@
</span><ins>+2014-08-05 Andreas Kling <akling@apple.com>
+
+ The JIT should cache property lookup misses.
+ <https://webkit.org/b/135578>
+
+ Add a JS microbenchmark that accesses an undefined property in a hot loop.
+
+ Reviewed by Geoffrey Garen.
+
+ * js/regress/script-tests/undefined-property-access.js: Added.
+ (foo):
+ * js/regress/undefined-property-access-expected.txt: Added.
+ * js/regress/undefined-property-access.html: Added.
+
</ins><span class="cx"> 2014-08-05 Martin Hodovan <mhodovan.u-szeged@partner.samsung.com>
</span><span class="cx">
</span><span class="cx"> ASSERTION FAILED: name[0] == '@' && length >= 2 in WebCore::CSSParser::detectAtToken
</span></span></pre></div>
<a id="trunkLayoutTestsjsregressscripttestsundefinedpropertyaccessjs"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/js/regress/script-tests/undefined-property-access.js (0 => 172099)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/js/regress/script-tests/undefined-property-access.js (rev 0)
+++ trunk/LayoutTests/js/regress/script-tests/undefined-property-access.js 2014-08-05 23:10:38 UTC (rev 172099)
</span><span class="lines">@@ -0,0 +1,9 @@
</span><ins>+someGlobal = 0;
+
+function foo() {
+ var myObject = {};
+ for (var i = 0; i < 10000000; ++i) {
+ someGlobal = myObject.undefinedProperty;
+ }
+}
+foo();
</ins></span></pre></div>
<a id="trunkLayoutTestsjsregressundefinedpropertyaccessexpectedtxt"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/js/regress/undefined-property-access-expected.txt (0 => 172099)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/js/regress/undefined-property-access-expected.txt (rev 0)
+++ trunk/LayoutTests/js/regress/undefined-property-access-expected.txt 2014-08-05 23:10:38 UTC (rev 172099)
</span><span class="lines">@@ -0,0 +1,10 @@
</span><ins>+JSRegress/undefined-property-access
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+PASS no exception thrown
+PASS successfullyParsed is true
+
+TEST COMPLETE
+
</ins></span></pre></div>
<a id="trunkLayoutTestsjsregressundefinedpropertyaccesshtml"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/js/regress/undefined-property-access.html (0 => 172099)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/js/regress/undefined-property-access.html (rev 0)
+++ trunk/LayoutTests/js/regress/undefined-property-access.html 2014-08-05 23:10:38 UTC (rev 172099)
</span><span class="lines">@@ -0,0 +1,12 @@
</span><ins>+<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
+<html>
+<head>
+<script src="../../resources/js-test-pre.js"></script>
+</head>
+<body>
+<script src="../../resources/regress-pre.js"></script>
+<script src="script-tests/undefined-property-access.js"></script>
+<script src="../../resources/regress-post.js"></script>
+<script src="../../resources/js-test-post.js"></script>
+</body>
+</html>
</ins></span></pre></div>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (172098 => 172099)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2014-08-05 23:06:03 UTC (rev 172098)
+++ trunk/Source/JavaScriptCore/ChangeLog 2014-08-05 23:10:38 UTC (rev 172099)
</span><span class="lines">@@ -1,3 +1,27 @@
</span><ins>+2014-08-05 Andreas Kling <akling@apple.com>
+
+ The JIT should cache property lookup misses.
+ <https://webkit.org/b/135578>
+
+ Add support for inline caching of object properties that don't exist.
+ Previously we'd fall back to the C++ slow-path whenever a property was missing.
+
+ It's implemented as a simple GetById-style stub that returns jsUndefined() as
+ long as the Structure chain check passes.
+
+ 10x speedup on the included microbenchmark.
+
+ Reviewed by Geoffrey Garen.
+
+ * jit/Repatch.cpp:
+ (JSC::toString):
+ (JSC::kindFor):
+ (JSC::generateByIdStub):
+ (JSC::tryCacheGetByID):
+ (JSC::patchJumpToGetByIdStub):
+ * runtime/PropertySlot.h:
+ (JSC::PropertySlot::isUnset):
+
</ins><span class="cx"> 2014-08-05 Commit Queue <commit-queue@webkit.org>
</span><span class="cx">
</span><span class="cx"> Unreviewed, rolling out r172009.
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorejitRepatchcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/jit/Repatch.cpp (172098 => 172099)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/jit/Repatch.cpp 2014-08-05 23:06:03 UTC (rev 172098)
+++ trunk/Source/JavaScriptCore/jit/Repatch.cpp 2014-08-05 23:10:38 UTC (rev 172099)
</span><span class="lines">@@ -52,6 +52,8 @@
</span><span class="cx">
</span><span class="cx"> namespace JSC {
</span><span class="cx">
</span><ins>+static void patchJumpToGetByIdStub(CodeBlock*, StructureStubInfo&, JITStubRoutine*);
+
</ins><span class="cx"> // Beware: in this code, it is not safe to assume anything about the following registers
</span><span class="cx"> // that would ordinarily have well-known values:
</span><span class="cx"> // - tagTypeNumberRegister
</span><span class="lines">@@ -226,6 +228,7 @@
</span><span class="cx">
</span><span class="cx"> enum ByIdStubKind {
</span><span class="cx"> GetValue,
</span><ins>+ GetUndefined,
</ins><span class="cx"> CallGetter,
</span><span class="cx"> CallCustomGetter,
</span><span class="cx"> CallSetter,
</span><span class="lines">@@ -237,6 +240,8 @@
</span><span class="cx"> switch (kind) {
</span><span class="cx"> case GetValue:
</span><span class="cx"> return "GetValue";
</span><ins>+ case GetUndefined:
+ return "GetUndefined";
</ins><span class="cx"> case CallGetter:
</span><span class="cx"> return "CallGetter";
</span><span class="cx"> case CallCustomGetter:
</span><span class="lines">@@ -255,6 +260,8 @@
</span><span class="cx"> {
</span><span class="cx"> if (slot.isCacheableValue())
</span><span class="cx"> return GetValue;
</span><ins>+ if (slot.isUnset())
+ return GetUndefined;
</ins><span class="cx"> if (slot.isCacheableCustom())
</span><span class="cx"> return CallCustomGetter;
</span><span class="cx"> RELEASE_ASSERT(slot.isCacheableGetter());
</span><span class="lines">@@ -299,7 +306,7 @@
</span><span class="cx"> static_cast<GPRReg>(stubInfo.patch.valueGPR));
</span><span class="cx"> GPRReg scratchGPR = TempRegisterSet(stubInfo.patch.usedRegisters).getFreeGPR();
</span><span class="cx"> bool needToRestoreScratch = scratchGPR == InvalidGPRReg;
</span><del>- RELEASE_ASSERT(!needToRestoreScratch || kind == GetValue);
</del><ins>+ RELEASE_ASSERT(!needToRestoreScratch || (kind == GetValue || kind == GetUndefined));
</ins><span class="cx">
</span><span class="cx"> CCallHelpers stubJit(&exec->vm(), exec->codeBlock());
</span><span class="cx"> if (needToRestoreScratch) {
</span><span class="lines">@@ -357,24 +364,28 @@
</span><span class="cx"> }
</span><span class="cx"> }
</span><span class="cx">
</span><del>- GPRReg baseForAccessGPR;
- if (chain) {
- // We could have clobbered scratchGPR earlier, so we have to reload from baseGPR to get the target.
- if (loadTargetFromProxy)
- stubJit.loadPtr(MacroAssembler::Address(baseGPR, JSProxy::targetOffset()), baseForGetGPR);
- stubJit.move(MacroAssembler::TrustedImmPtr(protoObject), scratchGPR);
- baseForAccessGPR = scratchGPR;
- } else {
- // For proxy objects, we need to do all the Structure checks before moving the baseGPR into
- // baseForGetGPR because if we fail any of the checks then we would have the wrong value in baseGPR
- // on the slow path.
- if (loadTargetFromProxy)
- stubJit.move(scratchGPR, baseForGetGPR);
- baseForAccessGPR = baseForGetGPR;
</del><ins>+ GPRReg baseForAccessGPR = InvalidGPRReg;
+ if (kind != GetUndefined) {
+ if (chain) {
+ // We could have clobbered scratchGPR earlier, so we have to reload from baseGPR to get the target.
+ if (loadTargetFromProxy)
+ stubJit.loadPtr(MacroAssembler::Address(baseGPR, JSProxy::targetOffset()), baseForGetGPR);
+ stubJit.move(MacroAssembler::TrustedImmPtr(protoObject), scratchGPR);
+ baseForAccessGPR = scratchGPR;
+ } else {
+ // For proxy objects, we need to do all the Structure checks before moving the baseGPR into
+ // baseForGetGPR because if we fail any of the checks then we would have the wrong value in baseGPR
+ // on the slow path.
+ if (loadTargetFromProxy)
+ stubJit.move(scratchGPR, baseForGetGPR);
+ baseForAccessGPR = baseForGetGPR;
+ }
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> GPRReg loadedValueGPR = InvalidGPRReg;
</span><del>- if (kind != CallCustomGetter && kind != CallCustomSetter) {
</del><ins>+ if (kind == GetUndefined)
+ stubJit.moveTrustedValue(jsUndefined(), valueRegs);
+ else if (kind != CallCustomGetter && kind != CallCustomSetter) {
</ins><span class="cx"> if (kind == GetValue)
</span><span class="cx"> loadedValueGPR = valueRegs.payloadGPR();
</span><span class="cx"> else
</span><span class="lines">@@ -408,7 +419,7 @@
</span><span class="cx"> std::unique_ptr<CallLinkInfo> callLinkInfo;
</span><span class="cx">
</span><span class="cx"> MacroAssembler::Jump success, fail;
</span><del>- if (kind != GetValue) {
</del><ins>+ if (kind != GetValue && kind != GetUndefined) {
</ins><span class="cx"> // Need to make sure that whenever this call is made in the future, we remember the
</span><span class="cx"> // place that we made it from. It just so happens to be the place that we are at
</span><span class="cx"> // right now!
</span><span class="lines">@@ -729,15 +740,46 @@
</span><span class="cx"> // FIXME: Cache property access for immediates.
</span><span class="cx"> if (!baseValue.isCell())
</span><span class="cx"> return GiveUpOnCache;
</span><ins>+
+ if (!slot.isCacheable() && !slot.isUnset())
+ return GiveUpOnCache;
+
</ins><span class="cx"> JSCell* baseCell = baseValue.asCell();
</span><span class="cx"> Structure* structure = baseCell->structure();
</span><del>- if (!slot.isCacheable())
- return GiveUpOnCache;
</del><span class="cx">
</span><span class="cx"> InlineCacheAction action = actionForCell(*vm, baseCell);
</span><span class="cx"> if (action != AttemptToCache)
</span><span class="cx"> return action;
</span><span class="cx">
</span><ins>+ if (slot.isUnset()) {
+ // Property lookup miss - let's try to cache that.
+ size_t count = normalizePrototypeChain(exec, baseCell);
+ if (count == InvalidPrototypeChain)
+ return GiveUpOnCache;
+ StructureChain* prototypeChain = structure->prototypeChain(exec);
+ PolymorphicGetByIdList* list = PolymorphicGetByIdList::from(stubInfo);
+ if (list->isFull()) {
+ // We need this extra check because of recursion.
+ return GiveUpOnCache;
+ }
+
+ RefPtr<JITStubRoutine> stubRoutine;
+ generateByIdStub(
+ exec, GetUndefined, propertyName, FunctionPtr(), stubInfo, prototypeChain, count, invalidOffset,
+ structure, false, nullptr,
+ stubInfo.callReturnLocation.labelAtOffset(stubInfo.patch.deltaCallToDone),
+ CodeLocationLabel(list->currentSlowPathTarget(stubInfo)), stubRoutine);
+
+ list->addAccess(GetByIdAccess(
+ *vm, codeBlock->ownerExecutable(),
+ GetByIdAccess::SimpleInline,
+ stubRoutine, structure, prototypeChain, count));
+
+ patchJumpToGetByIdStub(codeBlock, stubInfo, stubRoutine.get());
+
+ return list->isFull() ? GiveUpOnCache : RetryCacheLater;
+ }
+
</ins><span class="cx"> // Optimize self access.
</span><span class="cx"> if (slot.slotBase() == baseValue
</span><span class="cx"> && slot.isCacheableValue()
</span><span class="lines">@@ -760,7 +802,7 @@
</span><span class="cx"> repatchCall(exec->codeBlock(), stubInfo.callReturnLocation, operationGetById);
</span><span class="cx"> }
</span><span class="cx">
</span><del>-static void patchJumpToGetByIdStub(CodeBlock* codeBlock, StructureStubInfo& stubInfo, JITStubRoutine* stubRoutine)
</del><ins>+void patchJumpToGetByIdStub(CodeBlock* codeBlock, StructureStubInfo& stubInfo, JITStubRoutine* stubRoutine)
</ins><span class="cx"> {
</span><span class="cx"> RELEASE_ASSERT(stubInfo.accessType == access_get_by_id_list);
</span><span class="cx"> RepatchBuffer repatchBuffer(codeBlock);
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreruntimePropertySloth"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/runtime/PropertySlot.h (172098 => 172099)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/runtime/PropertySlot.h 2014-08-05 23:06:03 UTC (rev 172098)
+++ trunk/Source/JavaScriptCore/runtime/PropertySlot.h 2014-08-05 23:10:38 UTC (rev 172099)
</span><span class="lines">@@ -78,6 +78,7 @@
</span><span class="cx"> JSValue getValue(ExecState*, unsigned propertyName) const;
</span><span class="cx">
</span><span class="cx"> bool isCacheable() const { return m_cacheability == CachingAllowed && m_offset != invalidOffset; }
</span><ins>+ bool isUnset() const { return m_propertyType == TypeUnset; }
</ins><span class="cx"> bool isValue() const { return m_propertyType == TypeValue; }
</span><span class="cx"> bool isAccessor() const { return m_propertyType == TypeGetter; }
</span><span class="cx"> bool isCustom() const { return m_propertyType == TypeCustom; }
</span></span></pre>
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