Changeset 241571 in webkit for trunk/Source/JavaScriptCore/parser/VariableEnvironment.h

Timestamp:

Feb 14, 2019, 4:06:30 PM (6 years ago)

Author:

[email protected]

Message:

Cache the results of BytecodeGenerator::getVariablesUnderTDZ
​https://bugs.webkit.org/show_bug.cgi?id=194583
<rdar://problem/48028140>

Reviewed by Yusuke Suzuki.

JSTests:

• microbenchmarks/cache-get-variables-under-tdz-in-bytecode-generator.js: Added.

Source/JavaScriptCore:

This patch makes it so that getVariablesUnderTDZ caches a result of
CompactVariableMap::Handle. getVariablesUnderTDZ is costly when
it's called in an environment where there are a lot of variables.
This patch makes it so we cache its results. This is profitable when
getVariablesUnderTDZ is called repeatedly with the same environment
state. This is common since we call this every time we encounter a
function definition/expression node.

• builtins/BuiltinExecutables.cpp:

(JSC::BuiltinExecutables::createExecutable):

• bytecode/UnlinkedFunctionExecutable.cpp:

(JSC::UnlinkedFunctionExecutable::UnlinkedFunctionExecutable):

• bytecode/UnlinkedFunctionExecutable.h:
• bytecompiler/BytecodeGenerator.cpp:

(JSC::BytecodeGenerator::popLexicalScopeInternal):
(JSC::BytecodeGenerator::liftTDZCheckIfPossible):
(JSC::BytecodeGenerator::pushTDZVariables):
(JSC::BytecodeGenerator::getVariablesUnderTDZ):
(JSC::BytecodeGenerator::restoreTDZStack):

• bytecompiler/BytecodeGenerator.h:

(JSC::BytecodeGenerator::makeFunction):

• parser/VariableEnvironment.cpp:

(JSC::CompactVariableMap::Handle::Handle):
(JSC::CompactVariableMap::Handle::operator=):

• parser/VariableEnvironment.h:

(JSC::CompactVariableMap::Handle::operator bool const):

• runtime/CodeCache.cpp:

(JSC::CodeCache::getUnlinkedGlobalFunctionExecutable):

File:

• trunk/Source/JavaScriptCore/parser/VariableEnvironment.h (modified) (3 diffs)

trunk/Source/JavaScriptCore/parser/VariableEnvironment.h

@@ -205 +205 @@
 public:
     class Handle {
-        WTF_MAKE_NONCOPYABLE(Handle); // If we wanted to make this copyable, we'd need to do a hashtable lookup and bump the reference count of the map entry.
     public:
+        Handle() = default;
+
         Handle(CompactVariableEnvironment& environment, CompactVariableMap& map)
             : m_environment(&environment)
@@ -219 +220 @@
             other.m_environment = nullptr;
         }
+
+        Handle(const Handle&);
+        Handle& operator=(const Handle&);
+
         ~Handle();
+
+        explicit operator bool() const { return !!m_map; }
 
         const CompactVariableEnvironment& environment() const
@@ -227 +234 @@
 
     private:
-        CompactVariableEnvironment* m_environment;
+        CompactVariableEnvironment* m_environment { nullptr };
         RefPtr<CompactVariableMap> m_map;
     };