Simplified GC marking logic
https://bugs.webkit.org/show_bug.cgi?id=70258
Reviewed by Filip Pizlo.
No perf. change.
This is a first step toward GC allocating string backing stores, starting
with ropes. It also enables future simplifications and optimizations.
- Replaced some complex mark stack logic with a simple linear stack of
JSCell pointers.
- Replaced logic for short-circuiting marking based on JSType and/or
Structure flags with special cases for object, array, and string.
- Fiddled with inlining for better codegen.
(JSC::Heap::Heap): Provide more vptrs to SlotVisitor, for use in marking.
- heap/HeapRootVisitor.h: Removed unused functions that no longer build.
(JSC::MarkStackArray::MarkStackArray):
(JSC::MarkStackArray::~MarkStackArray):
(JSC::MarkStackArray::expand):
(JSC::MarkStackArray::shrinkAllocation):
(JSC::MarkStack::reset):
(JSC::visitChildren):
(JSC::SlotVisitor::drain):
(JSC::MarkStack::MarkStack):
(JSC::MarkStack::~MarkStack):
(JSC::MarkStackArray::append):
(JSC::MarkStackArray::removeLast):
(JSC::MarkStackArray::isEmpty):
(JSC::MarkStack::append):
(JSC::MarkStack::appendUnbarrieredPointer):
(JSC::MarkStack::internalAppend): Replaced complex mark set logic with
simple linear stack.
(JSC::SlotVisitor::SlotVisitor): Updated for above changes.
(JSC::JSArray::visitChildren):
- runtime/JSArray.h:
- runtime/JSObject.cpp:
(JSC::JSObject::visitChildren):
- runtime/JSObject.h: Don't inline visitChildren; it's too big.
(JSC::MarkStack::internalAppend): Nixed the short-circuit for CompoundType
because it prevented strings from owning GC pointers.
(JSC::MarkStack::appendValues): No need to validate; internalAppend will
do that for us.
