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<dl class="meta">
<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/208404">208404</a></dd>
<dt>Author</dt> <dd>ggaren@apple.com</dd>
<dt>Date</dt> <dd>2016-11-04 16:02:19 -0700 (Fri, 04 Nov 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>EvalCodeCache should not give up in strict mode and other cases
https://bugs.webkit.org/show_bug.cgi?id=164357
Reviewed by Michael Saboff.
JSTests:
* microbenchmarks/eval-cached.js: Added. 45x faster now.
* stress/eval-cached.js: Added. Try running the same eval text in a bunch
of different scopes and verify that we access the right scope.
Source/JavaScriptCore:
EvalCodeCache gives up in non-trivial cases because generated eval code
can't soundly migrate from, for example, a let scope to a non-let scope.
The number of cases has grown over time.
Instead, let's cache eval code based on the location of the call to
eval(). That way, we never relocate the code, and it's sound to make
normal assumptions about our surrounding scope.
* bytecode/EvalCodeCache.h:
(JSC::EvalCodeCache::CacheKey::CacheKey): Use CallSiteIndex to uniquely
identify the location of our call to eval().
(JSC::EvalCodeCache::CacheKey::hash):
(JSC::EvalCodeCache::CacheKey::operator==):
(JSC::EvalCodeCache::CacheKey::Hash::equal): Use CallSiteIndex instead
of lots of other flags.
(JSC::EvalCodeCache::tryGet): No need to include details that are implied
by our CallSiteIndex.
(JSC::EvalCodeCache::getSlow): No need to skip caching in complex
situations. We promise we'll never relocate the cached code.
(JSC::EvalCodeCache::isCacheableScope): Deleted.
(JSC::EvalCodeCache::isCacheable): Deleted.
* interpreter/Interpreter.cpp:
(JSC::eval): Pass through a CallSiteIndex to uniquely identify this call
to eval().</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkJSTestsChangeLog">trunk/JSTests/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCorebytecodeEvalCodeCacheh">trunk/Source/JavaScriptCore/bytecode/EvalCodeCache.h</a></li>
<li><a href="#trunkSourceJavaScriptCoreinterpreterCallFrameh">trunk/Source/JavaScriptCore/interpreter/CallFrame.h</a></li>
<li><a href="#trunkSourceJavaScriptCoreinterpreterInterpretercpp">trunk/Source/JavaScriptCore/interpreter/Interpreter.cpp</a></li>
</ul>
<h3>Added Paths</h3>
<ul>
<li><a href="#trunkJSTestsmicrobenchmarksevalcachedjs">trunk/JSTests/microbenchmarks/eval-cached.js</a></li>
<li><a href="#trunkJSTestsstressevalcachedjs">trunk/JSTests/stress/eval-cached.js</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkJSTestsChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/JSTests/ChangeLog (208403 => 208404)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/JSTests/ChangeLog 2016-11-04 22:53:33 UTC (rev 208403)
+++ trunk/JSTests/ChangeLog 2016-11-04 23:02:19 UTC (rev 208404)
</span><span class="lines">@@ -1,3 +1,14 @@
</span><ins>+2016-11-03 Geoffrey Garen <ggaren@apple.com>
+
+ EvalCodeCache should not give up in strict mode and other cases
+ https://bugs.webkit.org/show_bug.cgi?id=164357
+
+ Reviewed by Michael Saboff.
+
+ * microbenchmarks/eval-cached.js: Added. 45x faster now.
+ * stress/eval-cached.js: Added. Try running the same eval text in a bunch
+ of different scopes and verify that we access the right scope.
+
</ins><span class="cx"> 2016-11-04 JF Bastien <jfbastien@apple.com>
</span><span class="cx">
</span><span class="cx"> WebAssembly JS API: implement more sections
</span></span></pre></div>
<a id="trunkJSTestsmicrobenchmarksevalcachedjs"></a>
<div class="addfile"><h4>Added: trunk/JSTests/microbenchmarks/eval-cached.js (0 => 208404)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/JSTests/microbenchmarks/eval-cached.js (rev 0)
+++ trunk/JSTests/microbenchmarks/eval-cached.js 2016-11-04 23:02:19 UTC (rev 208404)
</span><span class="lines">@@ -0,0 +1,14 @@
</span><ins>+function foo(string) {
+ let result = 42;
+ for (let i = 0; i < 1000; ++i)
+ eval(string);
+ return result;
+}
+
+noInline(foo);
+
+for (let i = 0; i < 200; ++i) {
+ let result = foo("++result");
+ if (result != 42 + 1000)
+ throw "Error: bad result: " + result;
+}
</ins></span></pre></div>
<a id="trunkJSTestsstressevalcachedjs"></a>
<div class="addfile"><h4>Added: trunk/JSTests/stress/eval-cached.js (0 => 208404)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/JSTests/stress/eval-cached.js (rev 0)
+++ trunk/JSTests/stress/eval-cached.js 2016-11-04 23:02:19 UTC (rev 208404)
</span><span class="lines">@@ -0,0 +1,79 @@
</span><ins>+(function () {
+ "use strict";
+
+ function verify() {
+ for (var i = 0; i < counter; ++i) {
+ if (results[i] != i)
+ throw "strict mode verify() failed for item " + i + "."
+ }
+ }
+
+ let results = [ ];
+ let counter = 0;
+
+ let x = counter++;
+ results.push(eval("x"));
+
+ {
+ let x = counter++;
+ results.push(eval("x"));
+ }
+
+ try {
+ throw counter++;
+ } catch (x) {
+ results.push(eval("x"));
+ }
+
+ (() => {
+ var x = counter++;
+ results.push(eval("x"));
+ })();
+
+ (function (x) {
+ results.push(eval("x"));
+ })(counter++);
+
+ verify();
+})();
+
+(function () {
+ function verify() {
+ for (var i = 0; i < counter; ++i) {
+ if (results[i] != i)
+ throw "non-strict mode verify() failed for item " + i + "."
+ }
+ }
+
+ let results = [ ];
+ let counter = 0;
+
+ let x = counter++;
+ results.push(eval("x"));
+
+ {
+ let x = counter++;
+ results.push(eval("x"));
+ }
+
+ try {
+ throw counter++;
+ } catch (x) {
+ results.push(eval("x"));
+ }
+
+ (() => {
+ var x = counter++;
+ results.push(eval("x"));
+ })();
+
+ (function (x) {
+ results.push(eval("x"));
+ })(counter++);
+
+ with ({ x : counter++ }) {
+ results.push(eval("x"));
+ }
+
+ verify();
+})();
</ins></span></pre></div>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (208403 => 208404)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2016-11-04 22:53:33 UTC (rev 208403)
+++ trunk/Source/JavaScriptCore/ChangeLog 2016-11-04 23:02:19 UTC (rev 208404)
</span><span class="lines">@@ -1,3 +1,40 @@
</span><ins>+2016-11-02 Geoffrey Garen <ggaren@apple.com>
+
+ EvalCodeCache should not give up in strict mode and other cases
+ https://bugs.webkit.org/show_bug.cgi?id=164357
+
+ Reviewed by Michael Saboff.
+
+ EvalCodeCache gives up in non-trivial cases because generated eval code
+ can't soundly migrate from, for example, a let scope to a non-let scope.
+ The number of cases has grown over time.
+
+ Instead, let's cache eval code based on the location of the call to
+ eval(). That way, we never relocate the code, and it's sound to make
+ normal assumptions about our surrounding scope.
+
+ * bytecode/EvalCodeCache.h:
+ (JSC::EvalCodeCache::CacheKey::CacheKey): Use CallSiteIndex to uniquely
+ identify the location of our call to eval().
+
+ (JSC::EvalCodeCache::CacheKey::hash):
+ (JSC::EvalCodeCache::CacheKey::operator==):
+ (JSC::EvalCodeCache::CacheKey::Hash::equal): Use CallSiteIndex instead
+ of lots of other flags.
+
+ (JSC::EvalCodeCache::tryGet): No need to include details that are implied
+ by our CallSiteIndex.
+
+ (JSC::EvalCodeCache::getSlow): No need to skip caching in complex
+ situations. We promise we'll never relocate the cached code.
+
+ (JSC::EvalCodeCache::isCacheableScope): Deleted.
+ (JSC::EvalCodeCache::isCacheable): Deleted.
+
+ * interpreter/Interpreter.cpp:
+ (JSC::eval): Pass through a CallSiteIndex to uniquely identify this call
+ to eval().
+
</ins><span class="cx"> 2016-11-04 Keith Miller <keith_miller@apple.com>
</span><span class="cx">
</span><span class="cx"> Add support for Wasm br_table
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorebytecodeEvalCodeCacheh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/bytecode/EvalCodeCache.h (208403 => 208404)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/bytecode/EvalCodeCache.h 2016-11-04 22:53:33 UTC (rev 208403)
+++ trunk/Source/JavaScriptCore/bytecode/EvalCodeCache.h 2016-11-04 23:02:19 UTC (rev 208404)
</span><span class="lines">@@ -47,9 +47,9 @@
</span><span class="cx"> // Specialized cache key (compared with SourceCodeKey) for eval code cache.
</span><span class="cx"> class CacheKey {
</span><span class="cx"> public:
</span><del>- CacheKey(const String& source, DerivedContextType derivedContextType, EvalContextType evalContextType, bool isArrowFunctionContext)
</del><ins>+ CacheKey(const String& source, CallSiteIndex callSiteIndex)
</ins><span class="cx"> : m_source(source.impl())
</span><del>- , m_flags(SourceCodeType::EvalType, JSParserBuiltinMode::NotBuiltin, JSParserStrictMode::NotStrict, JSParserScriptMode::Classic, derivedContextType, evalContextType, isArrowFunctionContext)
</del><ins>+ , m_callSiteIndex(callSiteIndex)
</ins><span class="cx"> {
</span><span class="cx"> }
</span><span class="cx">
</span><span class="lines">@@ -60,13 +60,13 @@
</span><span class="cx">
</span><span class="cx"> CacheKey() = default;
</span><span class="cx">
</span><del>- unsigned hash() const { return m_source->hash(); }
</del><ins>+ unsigned hash() const { return m_source->hash() ^ m_callSiteIndex.bits(); }
</ins><span class="cx">
</span><span class="cx"> bool isEmptyValue() const { return !m_source; }
</span><span class="cx">
</span><span class="cx"> bool operator==(const CacheKey& other) const
</span><span class="cx"> {
</span><del>- return m_source == other.m_source && m_flags == other.m_flags;
</del><ins>+ return m_callSiteIndex == other.m_callSiteIndex && m_source == other.m_source;
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> bool isHashTableDeletedValue() const { return m_source.isHashTableDeletedValue(); }
</span><span class="lines">@@ -78,7 +78,7 @@
</span><span class="cx"> }
</span><span class="cx"> static bool equal(const CacheKey& lhs, const CacheKey& rhs)
</span><span class="cx"> {
</span><del>- return StringHash::equal(lhs.m_source, rhs.m_source) && lhs.m_flags == rhs.m_flags;
</del><ins>+ return lhs == rhs;
</ins><span class="cx"> }
</span><span class="cx"> static const bool safeToCompareToEmptyOrDeleted = false;
</span><span class="cx"> };
</span><span class="lines">@@ -87,19 +87,15 @@
</span><span class="cx">
</span><span class="cx"> private:
</span><span class="cx"> RefPtr<StringImpl> m_source;
</span><del>- SourceCodeFlags m_flags;
</del><ins>+ CallSiteIndex m_callSiteIndex;
</ins><span class="cx"> };
</span><span class="cx">
</span><del>- EvalExecutable* tryGet(bool inStrictContext, const String& evalSource, DerivedContextType derivedContextType, EvalContextType evalContextType, bool isArrowFunctionContext, JSScope* scope)
</del><ins>+ EvalExecutable* tryGet(const String& evalSource, CallSiteIndex callSiteIndex)
</ins><span class="cx"> {
</span><del>- if (isCacheable(inStrictContext, evalSource, scope)) {
- ASSERT(!inStrictContext);
- return m_cacheMap.fastGet(CacheKey(evalSource, derivedContextType, evalContextType, isArrowFunctionContext)).get();
- }
- return nullptr;
</del><ins>+ return m_cacheMap.fastGet(CacheKey(evalSource, callSiteIndex)).get();
</ins><span class="cx"> }
</span><span class="cx">
</span><del>- EvalExecutable* getSlow(ExecState* exec, JSCell* owner, bool inStrictContext, DerivedContextType derivedContextType, EvalContextType evalContextType, bool isArrowFunctionContext, const String& evalSource, JSScope* scope)
</del><ins>+ EvalExecutable* getSlow(ExecState* exec, JSCell* owner, const String& evalSource, CallSiteIndex callSiteIndex, bool inStrictContext, DerivedContextType derivedContextType, EvalContextType evalContextType, bool isArrowFunctionContext, JSScope* scope)
</ins><span class="cx"> {
</span><span class="cx"> VariableEnvironment variablesUnderTDZ;
</span><span class="cx"> JSScope::collectVariablesUnderTDZ(scope, variablesUnderTDZ);
</span><span class="lines">@@ -107,11 +103,9 @@
</span><span class="cx"> if (!evalExecutable)
</span><span class="cx"> return nullptr;
</span><span class="cx">
</span><del>- if (isCacheable(inStrictContext, evalSource, scope) && m_cacheMap.size() < maxCacheEntries) {
- ASSERT(!inStrictContext);
- m_cacheMap.set(CacheKey(evalSource, derivedContextType, evalContextType, isArrowFunctionContext), WriteBarrier<EvalExecutable>(exec->vm(), owner, evalExecutable));
- }
-
</del><ins>+ if (m_cacheMap.size() < maxCacheEntries)
+ m_cacheMap.set(CacheKey(evalSource, callSiteIndex), WriteBarrier<EvalExecutable>(exec->vm(), owner, evalExecutable));
+
</ins><span class="cx"> return evalExecutable;
</span><span class="cx"> }
</span><span class="cx">
</span><span class="lines">@@ -125,19 +119,6 @@
</span><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> private:
</span><del>- ALWAYS_INLINE bool isCacheableScope(JSScope* scope)
- {
- return scope->isGlobalLexicalEnvironment() || scope->isFunctionNameScopeObject() || scope->isVarScope();
- }
-
- ALWAYS_INLINE bool isCacheable(bool inStrictContext, const String& evalSource, JSScope* scope)
- {
- // If eval() is called and it has access to a lexical scope, we can't soundly cache it.
- // If the eval() only has access to the "var" scope, then we can cache it.
- return !inStrictContext
- && static_cast<size_t>(evalSource.length()) < Options::maximumEvalCacheableSourceLength()
- && isCacheableScope(scope);
- }
</del><span class="cx"> static const int maxCacheEntries = 64;
</span><span class="cx">
</span><span class="cx"> typedef HashMap<CacheKey, WriteBarrier<EvalExecutable>, CacheKey::Hash, CacheKey::HashTraits> EvalCacheMap;
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreinterpreterCallFrameh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/interpreter/CallFrame.h (208403 => 208404)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/interpreter/CallFrame.h 2016-11-04 22:53:33 UTC (rev 208403)
+++ trunk/Source/JavaScriptCore/interpreter/CallFrame.h 2016-11-04 23:02:19 UTC (rev 208404)
</span><span class="lines">@@ -57,6 +57,7 @@
</span><span class="cx"> #endif
</span><span class="cx">
</span><span class="cx"> explicit operator bool() const { return m_bits != UINT_MAX; }
</span><ins>+ bool operator==(const CallSiteIndex& other) const { return m_bits == other.m_bits; }
</ins><span class="cx">
</span><span class="cx"> inline uint32_t bits() const { return m_bits; }
</span><span class="cx">
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreinterpreterInterpretercpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/interpreter/Interpreter.cpp (208403 => 208404)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/interpreter/Interpreter.cpp 2016-11-04 22:53:33 UTC (rev 208403)
+++ trunk/Source/JavaScriptCore/interpreter/Interpreter.cpp 2016-11-04 23:02:19 UTC (rev 208404)
</span><span class="lines">@@ -109,6 +109,7 @@
</span><span class="cx"> RETURN_IF_EXCEPTION(scope, JSValue());
</span><span class="cx">
</span><span class="cx"> CallFrame* callerFrame = callFrame->callerFrame();
</span><ins>+ CallSiteIndex callerCallSiteIndex = callerFrame->callSiteIndex();
</ins><span class="cx"> CodeBlock* callerCodeBlock = callerFrame->codeBlock();
</span><span class="cx"> JSScope* callerScopeChain = callerFrame->uncheckedR(callerCodeBlock->scopeRegister().offset()).Register::scope();
</span><span class="cx"> UnlinkedCodeBlock* callerUnlinkedCodeBlock = callerCodeBlock->unlinkedCodeBlock();
</span><span class="lines">@@ -130,7 +131,7 @@
</span><span class="cx"> else
</span><span class="cx"> evalContextType = EvalContextType::None;
</span><span class="cx">
</span><del>- EvalExecutable* eval = callerCodeBlock->evalCodeCache().tryGet(callerCodeBlock->isStrictMode(), programSource, derivedContextType, evalContextType, isArrowFunctionContext, callerScopeChain);
</del><ins>+ EvalExecutable* eval = callerCodeBlock->evalCodeCache().tryGet(programSource, callerCallSiteIndex);
</ins><span class="cx"> if (!eval) {
</span><span class="cx"> if (!callerCodeBlock->isStrictMode()) {
</span><span class="cx"> if (programSource.is8Bit()) {
</span><span class="lines">@@ -147,7 +148,7 @@
</span><span class="cx"> // If the literal parser bailed, it should not have thrown exceptions.
</span><span class="cx"> ASSERT(!scope.exception());
</span><span class="cx">
</span><del>- eval = callerCodeBlock->evalCodeCache().getSlow(callFrame, callerCodeBlock, callerCodeBlock->isStrictMode(), derivedContextType, evalContextType, isArrowFunctionContext, programSource, callerScopeChain);
</del><ins>+ eval = callerCodeBlock->evalCodeCache().getSlow(callFrame, callerCodeBlock, programSource, callerCallSiteIndex, callerCodeBlock->isStrictMode(), derivedContextType, evalContextType, isArrowFunctionContext, callerScopeChain);
</ins><span class="cx">
</span><span class="cx"> if (!eval)
</span><span class="cx"> return jsUndefined();
</span></span></pre>
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