Changeset 194017 in webkit for trunk/Source/JavaScriptCore/parser/SourceCodeKey.h

Timestamp:

Dec 13, 2015, 12:03:24 PM (9 years ago)

Author:

[email protected]

Message:

CachedScript could have a copy-free path for all-ASCII scripts.
<​https://webkit.org/b/152203>

Source/JavaScriptCore:

Reviewed by Antti Koivisto.

Make SourceProvider vend a StringView instead of a String.
This relaxes the promises that providers have to make about string lifetimes.

This means that on the WebCore side, CachedScript is free to cache a String
internally, while only ever exposing it as a temporary StringView.

A few extra copies (CPU, not memory) are introduced, none of them on hot paths.

• API/JSScriptRef.cpp:
• bytecode/CodeBlock.cpp:

(JSC::CodeBlock::sourceCodeForTools):
(JSC::CodeBlock::dumpSource):

• inspector/ScriptDebugServer.cpp:

(Inspector::ScriptDebugServer::dispatchDidParseSource):
(Inspector::ScriptDebugServer::dispatchFailedToParseSource):

• interpreter/Interpreter.cpp:

(JSC::Interpreter::execute):

• jsc.cpp:

(functionFindTypeForExpression):
(functionHasBasicBlockExecuted):
(functionBasicBlockExecutionCount):

• parser/Lexer.cpp:

(JSC::Lexer<T>::setCode):

• parser/Lexer.h:

(JSC::Lexer<LChar>::setCodeStart):
(JSC::Lexer<UChar>::setCodeStart):

• parser/Parser.h:

(JSC::Parser::getToken):

• parser/SourceCode.cpp:

(JSC::SourceCode::toUTF8):

• parser/SourceCode.h:

(JSC::SourceCode::hash):
(JSC::SourceCode::view):
(JSC::SourceCode::toString): Deleted.

• parser/SourceCodeKey.h:

(JSC::SourceCodeKey::SourceCodeKey):
(JSC::SourceCodeKey::string):

• parser/SourceProvider.h:

(JSC::SourceProvider::getRange):

• runtime/Completion.cpp:

(JSC::loadAndEvaluateModule):
(JSC::loadModule):

• runtime/ErrorInstance.cpp:

(JSC::appendSourceToError):

• runtime/FunctionPrototype.cpp:

(JSC::functionProtoFuncToString):

• tools/FunctionOverrides.cpp:

(JSC::initializeOverrideInfo):
(JSC::FunctionOverrides::initializeOverrideFor):

Source/WebCore:

Reviewed by ANtti Koivisto.

Many (if not most) of script resources on the web contain nothing but ASCII characters.
Such resources, when streamed through a text decoder, will yield the exact same byte
sequence, except in anonymous heap memory instead of delicious file-backed pages.

Care is taken to ensure that the wrapper StringImpl is updated to target newly cached
resource data if an asynchronous caching notification comes in.

• loader/cache/CachedResource.cpp:

(WebCore::CachedResource::tryReplaceEncodedData):

• loader/cache/CachedResource.h:

(WebCore::CachedResource::didReplaceSharedBufferContents):

• loader/cache/CachedScript.cpp:

(WebCore::encodingMayBeAllASCII):
(WebCore::CachedScript::script):
(WebCore::CachedScript::didReplaceSharedBufferContents):

• loader/cache/CachedScript.h:
• platform/SharedBuffer.h:
• platform/cf/SharedBufferCF.cpp:

(WebCore::SharedBuffer::tryReplaceContentsWithPlatformBuffer):

File:

• trunk/Source/JavaScriptCore/parser/SourceCodeKey.h (modified) (2 diffs)

trunk/Source/JavaScriptCore/parser/SourceCodeKey.h

@@ -46 +46 @@
         , m_name(name)
         , m_flags((static_cast<unsigned>(codeType) << 3) | (static_cast<unsigned>(builtinMode) << 2) | (static_cast<unsigned>(strictMode) << 1) | static_cast<unsigned>(thisTDZMode))
-        , m_hash(string().impl()->hash())
+        , m_hash(sourceCode.hash())
     {
     }
@@ -65 +65 @@
     // To save memory, we compute our string on demand. It's expected that source
     // providers cache their strings to make this efficient.
-    String string() const { return m_sourceCode.toString(); }
+    StringView string() const { return m_sourceCode.view(); }
 
     bool operator==(const SourceCodeKey& other) const