jspropertytree.cpp
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* vim: set ts=8 sts=4 et sw=4 tw=99:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "jspropertytree.h"
#include "jscntxt.h"
#include "jsgc.h"
#include "jstypes.h"
#include "vm/Shape.h"
#include "jsgcinlines.h"
#include "vm/Shape-inl.h"
using namespace js;
inline HashNumber
ShapeHasher::hash(const Lookup &l)
{
return l.hash();
}
inline bool
ShapeHasher::match(const Key k, const Lookup &l)
{
return k->matches(l);
}
Shape *
PropertyTree::newShape(ExclusiveContext *cx)
{
Shape *shape = js_NewGCShape(cx);
if (!shape)
js_ReportOutOfMemory(cx);
return shape;
}
static KidsHash *
HashChildren(Shape *kid1, Shape *kid2)
{
KidsHash *hash = js_new<KidsHash>();
if (!hash || !hash->init(2)) {
js_delete(hash);
return nullptr;
}
JS_ALWAYS_TRUE(hash->putNew(StackShape(kid1), kid1));
JS_ALWAYS_TRUE(hash->putNew(StackShape(kid2), kid2));
return hash;
}
bool
PropertyTree::insertChild(ExclusiveContext *cx, Shape *parent, Shape *child)
{
JS_ASSERT(!parent->inDictionary());
JS_ASSERT(!child->parent);
JS_ASSERT(!child->inDictionary());
JS_ASSERT(child->compartment() == parent->compartment());
JS_ASSERT(cx->isInsideCurrentCompartment(this));
KidsPointer *kidp = &parent->kids;
if (kidp->isNull()) {
child->setParent(parent);
kidp->setShape(child);
return true;
}
if (kidp->isShape()) {
Shape *shape = kidp->toShape();
JS_ASSERT(shape != child);
JS_ASSERT(!shape->matches(child));
KidsHash *hash = HashChildren(shape, child);
if (!hash) {
js_ReportOutOfMemory(cx);
return false;
}
kidp->setHash(hash);
child->setParent(parent);
return true;
}
if (!kidp->toHash()->putNew(StackShape(child), child)) {
js_ReportOutOfMemory(cx);
return false;
}
child->setParent(parent);
return true;
}
void
Shape::removeChild(Shape *child)
{
JS_ASSERT(!child->inDictionary());
JS_ASSERT(child->parent == this);
KidsPointer *kidp = &kids;
if (kidp->isShape()) {
JS_ASSERT(kidp->toShape() == child);
kidp->setNull();
child->parent = nullptr;
return;
}
KidsHash *hash = kidp->toHash();
JS_ASSERT(hash->count() >= 2); /* otherwise kidp->isShape() should be true */
hash->remove(StackShape(child));
child->parent = nullptr;
if (hash->count() == 1) {
/* Convert from HASH form back to SHAPE form. */
KidsHash::Range r = hash->all();
Shape *otherChild = r.front();
JS_ASSERT((r.popFront(), r.empty())); /* No more elements! */
kidp->setShape(otherChild);
js_delete(hash);
}
}
Shape *
PropertyTree::getChild(ExclusiveContext *cx, Shape *parentArg, StackShape &unrootedChild)
{
RootedShape parent(cx, parentArg);
JS_ASSERT(parent);
Shape *existingShape = nullptr;
/*
* The property tree has extremely low fan-out below its root in
* popular embeddings with real-world workloads. Patterns such as
* defining closures that capture a constructor's environment as
* getters or setters on the new object that is passed in as
* |this| can significantly increase fan-out below the property
* tree root -- see bug 335700 for details.
*/
KidsPointer *kidp = &parent->kids;
if (kidp->isShape()) {
Shape *kid = kidp->toShape();
if (kid->matches(unrootedChild))
existingShape = kid;
} else if (kidp->isHash()) {
if (KidsHash::Ptr p = kidp->toHash()->lookup(unrootedChild))
existingShape = *p;
} else {
/* If kidp->isNull(), we always insert. */
}
#ifdef JSGC_INCREMENTAL
if (existingShape) {
JS::Zone *zone = existingShape->zone();
if (zone->needsBarrier()) {
/*
* We need a read barrier for the shape tree, since these are weak
* pointers.
*/
Shape *tmp = existingShape;
MarkShapeUnbarriered(zone->barrierTracer(), &tmp, "read barrier");
JS_ASSERT(tmp == existingShape);
} else if (zone->isGCSweeping() && !existingShape->isMarked() &&
!existingShape->arenaHeader()->allocatedDuringIncremental)
{
/*
* The shape we've found is unreachable and due to be finalized, so
* remove our weak reference to it and don't use it.
*/
JS_ASSERT(parent->isMarked());
parent->removeChild(existingShape);
existingShape = nullptr;
}
}
#endif
if (existingShape)
return existingShape;
RootedGeneric<StackShape*> child(cx, &unrootedChild);
Shape *shape = newShape(cx);
if (!shape)
return nullptr;
new (shape) Shape(*child, parent->numFixedSlots());
if (!insertChild(cx, parent, shape))
return nullptr;
return shape;
}
Shape *
PropertyTree::lookupChild(ThreadSafeContext *cx, Shape *parent, const StackShape &child)
{
/* Keep this in sync with the logic of getChild above. */
Shape *shape = nullptr;
JS_ASSERT(parent);
KidsPointer *kidp = &parent->kids;
if (kidp->isShape()) {
Shape *kid = kidp->toShape();
if (kid->matches(child))
shape = kid;
} else if (kidp->isHash()) {
if (KidsHash::Ptr p = kidp->toHash()->readonlyThreadsafeLookup(child))
shape = *p;
} else {
return nullptr;
}
#if defined(JSGC_INCREMENTAL) && defined(DEBUG)
if (shape) {
JS::Zone *zone = shape->arenaHeader()->zone;
JS_ASSERT(!zone->needsBarrier());
JS_ASSERT(!(zone->isGCSweeping() && !shape->isMarked() &&
!shape->arenaHeader()->allocatedDuringIncremental));
}
#endif
return shape;
}
void
Shape::sweep()
{
if (inDictionary())
return;
/*
* We detach the child from the parent if the parent is reachable.
*
* Note that due to incremental sweeping, the parent pointer may point
* to the original reachable parent, or it may point to a new live
* object allocated in the same cell that used to hold the parent.
*
* There are three cases:
*
* Case 1: parent is not marked - parent is unreachable, may have been
* finalized, and the cell may subsequently have been
* reallocated to a compartment that is not being marked (cells
* are marked when allocated in a compartment that is currenly
* being marked by the collector).
*
* Case 2: parent is marked and is in a different compartment - parent
* has been freed and reallocated to compartment that was being
* marked.
*
* Case 3: parent is marked and is in the same compartment - parent is
* stil reachable and we need to detach from it.
*/
if (parent && parent->isMarked() && parent->compartment() == compartment())
parent->removeChild(this);
}
void
Shape::finalize(FreeOp *fop)
{
if (!inDictionary() && kids.isHash())
fop->delete_(kids.toHash());
}
#ifdef DEBUG
void
KidsPointer::checkConsistency(Shape *aKid) const
{
if (isShape()) {
JS_ASSERT(toShape() == aKid);
} else {
JS_ASSERT(isHash());
KidsHash *hash = toHash();
KidsHash::Ptr ptr = hash->lookup(StackShape(aKid));
JS_ASSERT(*ptr == aKid);
}
}
void
Shape::dump(JSContext *cx, FILE *fp) const
{
/* This is only used from gdb, so allowing GC here would just be confusing. */
gc::AutoSuppressGC suppress(cx);
jsid propid = this->propid();
JS_ASSERT(!JSID_IS_VOID(propid));
if (JSID_IS_INT(propid)) {
fprintf(fp, "[%ld]", (long) JSID_TO_INT(propid));
} else {
JSLinearString *str;
if (JSID_IS_ATOM(propid)) {
str = JSID_TO_ATOM(propid);
} else {
JS_ASSERT(JSID_IS_OBJECT(propid));
Value v = IdToValue(propid);
JSString *s = ToStringSlow<NoGC>(cx, v);
fputs("object ", fp);
str = s ? s->ensureLinear(cx) : nullptr;
}
if (!str)
fputs("<error>", fp);
else
FileEscapedString(fp, str, '"');
}
fprintf(fp, " g/s %p/%p slot %d attrs %x ",
JS_FUNC_TO_DATA_PTR(void *, base()->rawGetter),
JS_FUNC_TO_DATA_PTR(void *, base()->rawSetter),
hasSlot() ? slot() : -1, attrs);
if (attrs) {
int first = 1;
fputs("(", fp);
#define DUMP_ATTR(name, display) if (attrs & JSPROP_##name) fputs(&(" " #display)[first], fp), first = 0
DUMP_ATTR(ENUMERATE, enumerate);
DUMP_ATTR(READONLY, readonly);
DUMP_ATTR(PERMANENT, permanent);
DUMP_ATTR(GETTER, getter);
DUMP_ATTR(SETTER, setter);
DUMP_ATTR(SHARED, shared);
#undef DUMP_ATTR
fputs(") ", fp);
}
fprintf(fp, "flags %x ", flags);
if (flags) {
int first = 1;
fputs("(", fp);
#define DUMP_FLAG(name, display) if (flags & name) fputs(&(" " #display)[first], fp), first = 0
DUMP_FLAG(IN_DICTIONARY, in_dictionary);
#undef DUMP_FLAG
fputs(") ", fp);
}
}
void
Shape::dumpSubtree(JSContext *cx, int level, FILE *fp) const
{
if (!parent) {
JS_ASSERT(level == 0);
JS_ASSERT(JSID_IS_EMPTY(propid_));
fprintf(fp, "class %s emptyShape\n", getObjectClass()->name);
} else {
fprintf(fp, "%*sid ", level, "");
dump(cx, fp);
}
if (!kids.isNull()) {
++level;
if (kids.isShape()) {
Shape *kid = kids.toShape();
JS_ASSERT(kid->parent == this);
kid->dumpSubtree(cx, level, fp);
} else {
const KidsHash &hash = *kids.toHash();
for (KidsHash::Range range = hash.all(); !range.empty(); range.popFront()) {
Shape *kid = range.front();
JS_ASSERT(kid->parent == this);
kid->dumpSubtree(cx, level, fp);
}
}
}
}
#endif