/*
* The function tries to scan the whole rope tree using the marking stack as
* temporary storage. If that becomes full, the unscanned ropes are added to
* the delayed marking list. When the function returns, the marking stack is
* at the same depth as it was on entry. This way we avoid using tags when
* pushing ropes to the stack as ropes never leaks to other users of the
* stack. This also assumes that a rope can only point to other ropes or
* linear strings, it cannot refer to GC things of other types.
*/
static void
ScanRope(GCMarker *gcmarker, JSRope *rope)
{
ptrdiff_t savedPos = gcmarker->stack.position();
for (;;) {
JS_ASSERT(GetGCThingTraceKind(rope) == JSTRACE_STRING);
JS_ASSERT(rope->JSString::isRope());
JS_COMPARTMENT_ASSERT_STR(gcmarker->runtime, rope);
JS_ASSERT(rope->isMarked());
JSRope *next = NULL;
JSString *right = rope->rightChild();
if (right->markIfUnmarked()) {
if (right->isLinear())
ScanLinearString(gcmarker, &right->asLinear());
else
next = &right->asRope();
}
JSString *left = rope->leftChild();
if (left->markIfUnmarked()) {
if (left->isLinear()) {
ScanLinearString(gcmarker, &left->asLinear());
} else {
/*
* When both children are ropes, set aside the right one to
* scan it later.
*/
if (next && !gcmarker->stack.push(reinterpret_cast<uintptr_t>(next)))
gcmarker->delayMarkingChildren(next);
next = &left->asRope();
}
}
if (next) {
rope = next;
} else if (savedPos != gcmarker->stack.position()) {
JS_ASSERT(savedPos < gcmarker->stack.position());
rope = reinterpret_cast<JSRope *>(gcmarker->stack.pop());
} else {
break;
}
}
JS_ASSERT(savedPos == gcmarker->stack.position());
}
inline void
GCMarker::processMarkStackTop(SliceBudget &budget)
{
/*
* The function uses explicit goto and implements the scanning of the
* object directly. It allows to eliminate the tail recursion and
* significantly improve the marking performance, see bug 641025.
*/
HeapSlot *vp, *end;
JSObject *obj;
uintptr_t addr = stack.pop();
uintptr_t tag = addr & StackTagMask;
addr &= ~StackTagMask;
if (tag == ValueArrayTag) {
JS_STATIC_ASSERT(ValueArrayTag == 0);
JS_ASSERT(!(addr & Cell::CellMask));
obj = reinterpret_cast<JSObject *>(addr);
uintptr_t addr2 = stack.pop();
uintptr_t addr3 = stack.pop();
JS_ASSERT(addr2 <= addr3);
JS_ASSERT((addr3 - addr2) % sizeof(Value) == 0);
vp = reinterpret_cast<HeapSlot *>(addr2);
end = reinterpret_cast<HeapSlot *>(addr3);
goto scan_value_array;
}
if (tag == ObjectTag) {
obj = reinterpret_cast<JSObject *>(addr);
JS_COMPARTMENT_ASSERT(runtime, obj);
goto scan_obj;
}
processMarkStackOther(budget, tag, addr);
return;
scan_value_array:
JS_ASSERT(vp <= end);
while (vp != end) {
const Value &v = *vp++;
if (v.isString()) {
JSString *str = v.toString();
JS_COMPARTMENT_ASSERT_STR(runtime, str);
JS_ASSERT(str->compartment() == runtime->atomsCompartment ||
str->compartment() == obj->compartment());
if (str->markIfUnmarked())
ScanString(this, str);
} else if (v.isObject()) {
JSObject *obj2 = &v.toObject();
JS_COMPARTMENT_ASSERT(runtime, obj2);
JS_ASSERT(obj->compartment() == obj2->compartment());
if (obj2->markIfUnmarked(getMarkColor())) {
pushValueArray(obj, vp, end);
obj = obj2;
goto scan_obj;
}
}
}
return;
scan_obj:
{
JS_COMPARTMENT_ASSERT(runtime, obj);
budget.step();
if (budget.isOverBudget()) {
pushObject(obj);
return;
}
types::TypeObject *type = obj->typeFromGC();
PushMarkStack(this, type);
Shape *shape = obj->lastProperty();
PushMarkStack(this, shape);
/* Call the trace hook if necessary. */
Class *clasp = shape->getObjectClass();
if (clasp->trace) {
if (clasp == &ArrayClass) {
JS_ASSERT(!shape->isNative());
vp = obj->getDenseArrayElements();
end = vp + obj->getDenseArrayInitializedLength();
goto scan_value_array;
} else {
JS_ASSERT_IF(runtime->gcMode == JSGC_MODE_INCREMENTAL &&
runtime->gcIncrementalEnabled,
clasp->flags & JSCLASS_IMPLEMENTS_BARRIERS);
}
clasp->trace(this, obj);
}
if (!shape->isNative())
return;
unsigned nslots = obj->slotSpan();
vp = obj->fixedSlots();
if (obj->slots) {
unsigned nfixed = obj->numFixedSlots();
if (nslots > nfixed) {
pushValueArray(obj, vp, vp + nfixed);
vp = obj->slots;
end = vp + (nslots - nfixed);
goto scan_value_array;
}
}
JS_ASSERT(nslots <= obj->numFixedSlots());
end = vp + nslots;
goto scan_value_array;
}
}