https://bugs.webkit.org/show_bug.cgi?id=32136
Add a rope representation to JSString. Presently JSString always holds its data in UString form.
Instead, allow the result of a string concatenation to be represented in a tree form - with a
variable sized, reference-counted rope node retaining a set of UString::Reps (or other rope nopes).
Reviewed by Oliver "Brraaaaiiiinnnnnzzzzzzzz" Hunt.
Strings must still currently be resolved down to a flat UString representation before being used,
but by holding the string in a rope representation during construction we can avoid copying data
until we know the final size of the string.
~2% progression on SunSpider (~25% on date-format-xparb, ~20% on string-validate-input).
- interpreter/Interpreter.cpp:
(JSC::Interpreter::privateExecute):
- Make use of new JSString::length() method to avoid prematurely resolving ropes.
(JSC::JIT::privateCompileCTIMachineTrampolines):
- Switch the string length trampoline to read the length directly from JSString::m_length,
rather than from the JSString's UString::Rep's 'len' property.
(JSC::DEFINE_STUB_FUNCTION):
- Modify op_add such that addition of two strings, where either or both strings are already
in rope representation, produces a rope as a result.
(JSC::JSString::Rope::~Rope):
(JSC::copyChars):
(JSC::JSString::resolveRope):
(JSC::JSString::getPrimitiveNumber):
(JSC::JSString::toBoolean):
(JSC::JSString::toNumber):
(JSC::JSString::toString):
(JSC::JSString::toThisString):
(JSC::JSString::getStringPropertyDescriptor):
(JSC::JSString::Rope::Fiber::Fiber):
(JSC::JSString::Rope::Fiber::destroy):
(JSC::JSString::Rope::Fiber::isRope):
(JSC::JSString::Rope::Fiber::rope):
(JSC::JSString::Rope::Fiber::string):
(JSC::JSString::Rope::create):
(JSC::JSString::Rope::initializeFiber):
(JSC::JSString::Rope::ropeLength):
(JSC::JSString::Rope::stringLength):
(JSC::JSString::Rope::fibers):
(JSC::JSString::Rope::Rope):
(JSC::JSString::Rope::operator new):
(JSC::JSString::JSString):
(JSC::JSString::value):
(JSC::JSString::length):
(JSC::JSString::isRope):
(JSC::JSString::rope):
(JSC::JSString::string):
(JSC::JSString::canGetIndex):
(JSC::jsSingleCharacterSubstring):
(JSC::JSString::getIndex):
(JSC::jsSubstring):
(JSC::JSString::getStringPropertySlot):
(JSC::jsAdd):
(JSC::concatenateStrings):
- Update string concatenation, and addition of ropes, to produce ropes.
- runtime/StringObject.cpp:
(JSC::StringObject::getOwnPropertyNames):
- Make use of new JSString::length() method to avoid prematurely resolving ropes.
