Changeset 196272 in webkit for trunk/Source/JavaScriptCore/runtime/CodeCache.cpp

Timestamp:

Feb 8, 2016, 2:31:52 PM (9 years ago)

Author:

[email protected]

Message:

CodeCache should give up on evals if there are variables under TDZ
​https://bugs.webkit.org/show_bug.cgi?id=154002
rdar://problem/24300998

Reviewed by Mark Lam.

Disable the code cache optimization because our approach to TDZ for scoped variables - using
a separate check_tdz opcode when logically it's the get_from_scope's job to do it - makes
caching code impossible if there are any variables in TDZ.

We should do the right thing in the future, and fold the TDZ check into the get_from_scope.
This is better not only because it will restore caching, but because our bytecode for heap
accesses is usually at the highest practically doable level of abstraction, so that ICs,
compilers and caches can see the intended meaning of the bytecode more easily.

This doesn't appear to slow anything down, but that's just because we don't have enough ES6
benchmarks. I've filed: ​https://bugs.webkit.org/show_bug.cgi?id=154010

• runtime/CodeCache.cpp:

(JSC::CodeCache::getGlobalCodeBlock):

File:

• trunk/Source/JavaScriptCore/runtime/CodeCache.cpp (modified) (2 diffs)

trunk/Source/JavaScriptCore/runtime/CodeCache.cpp

@@ -1 +1 @@
 /*
- * Copyright (C) 2012 Apple Inc. All Rights Reserved.
+ * Copyright (C) 2012, 2016 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -88 +88 @@
     SourceCodeKey key = SourceCodeKey(source, String(), CacheTypes<UnlinkedCodeBlockType>::codeType, builtinMode, strictMode, thisTDZMode);
     SourceCodeValue* cache = m_sourceCode.findCacheAndUpdateAge(key);
-    bool canCache = debuggerMode == DebuggerOff && profilerMode == ProfilerOff && !vm.typeProfiler() && !vm.controlFlowProfiler();
+    // FIXME: We should do something smart for TDZ instead of just disabling caching.
+    // https://bugs.webkit.org/show_bug.cgi?id=154010
+    bool canCache = debuggerMode == DebuggerOff && profilerMode == ProfilerOff && !vm.typeProfiler() && !vm.controlFlowProfiler() && !variablesUnderTDZ->size();
     if (cache && canCache) {
         UnlinkedCodeBlockType* unlinkedCodeBlock = jsCast<UnlinkedCodeBlockType*>(cache->cell.get());