Changeset 190563 in webkit for trunk/Source/JavaScriptCore/heap/Heap.cpp

Timestamp:

Oct 5, 2015, 10:22:20 AM (10 years ago)

Author:

[email protected]

Message:

JSC::SlotVisitor should not be a hot mess
​https://bugs.webkit.org/show_bug.cgi?id=149798

Reviewed by Andreas Kling.

I had to debug JSC::SlotVisitor the other day. It was hard to follow.
Let's make it easy to follow.

• heap/Heap.cpp:

(JSC::Heap::markRoots):
(JSC::Heap::resetVisitors):
(JSC::Heap::objectCount):
(JSC::Heap::addToRememberedSet):
(JSC::Heap::collectAndSweep):

• heap/Heap.h: Deleted the string hash-consing code. It

was dead code.

Since no benchmark noticed the commit that broke this feature, perhaps
it's not worth having.

Either way, the best thing to do with dead code is to delete it.
It's still there in svn if we ever want to pick it up again.

• heap/HeapRootVisitor.h:

(JSC::HeapRootVisitor::visit):
(JSC::HeapRootVisitor::visitor): Removed the private append functions
for unsafe pointers and switched HeapRootVisitor over to the public
specially named functions for unsafe pointers.

In future, we should either remove the public specially named functions
or remove HeapRootVisitor, since they serve the same purpose. At least
for now we don't have pairs of functions on SlotVisitor that do the
exact same thing.

• heap/SlotVisitor.cpp:

(JSC::validate): Moved this static function to the top of the file.

(JSC::SlotVisitor::SlotVisitor):
(JSC::SlotVisitor::didStartMarking):
(JSC::SlotVisitor::reset): More hash cons removal.

(JSC::SlotVisitor::append):

(JSC::SlotVisitor::setMarkedAndAppendToMarkStack):
(JSC::SlotVisitor::appendToMarkStack): Renamed these functions to
distinguish them from the up-front helper functions that just do type
conversions. These are the functions that actually do stuff.

Moved these functions out of line to make it easier to set breakpoints,
and to enable code changes for debugging, like printf and synchronous
marking, without recompiling the world.

setMarkedAndAppendToMarkStack is roughly 258 bytes long (not including
function prologue and epilogue), so inlining it was probably not a
great idea in the first place.

(JSC::SlotVisitor::donateKnownParallel):
(JSC::SlotVisitor::drain):
(JSC::SlotVisitor::drainFromShared): Removed some stack probing code.
It was also dead.

(JSC::SlotVisitor::addOpaqueRoot):
(JSC::SlotVisitor::containsOpaqueRoot):
(JSC::SlotVisitor::containsOpaqueRootTriState):
(JSC::SlotVisitor::opaqueRootCount):
(JSC::SlotVisitor::mergeOpaqueRootsIfNecessary):
(JSC::SlotVisitor::mergeOpaqueRootsIfProfitable):
(JSC::SlotVisitor::donate):
(JSC::SlotVisitor::donateAndDrain):
(JSC::SlotVisitor::copyLater):
(JSC::SlotVisitor::mergeOpaqueRoots):
(JSC::SlotVisitor::harvestWeakReferences):
(JSC::SlotVisitor::finalizeUnconditionalFinalizers):
(JSC::SlotVisitor::dump): Moved more code out-of-line. These code paths
are not hot and/or not small, so we need more evidence before we inline
them. The SlotVisitor headers are included everywhere, so we should
make them include less.

Removed "internal" from all function names because it wasn't applied in
any consistent way that would mean anything.

(JSC::JSString::tryHashConsLock): Deleted.
(JSC::JSString::releaseHashConsLock): Deleted.
(JSC::JSString::shouldTryHashCons): Deleted.
(JSC::SlotVisitor::internalAppend): Deleted.
(JSC::SlotVisitor::validate): Deleted.

• heap/SlotVisitor.h:

(JSC::SlotVisitor::resetChildCount): Deleted.
(JSC::SlotVisitor::childCount): Deleted.
(JSC::SlotVisitor::incrementChildCount): Deleted. Removed this child
count thing. It was dead code.

• heap/SlotVisitorInlines.h:

(JSC::SlotVisitor::appendUnbarrieredPointer):
(JSC::SlotVisitor::appendUnbarrieredReadOnlyPointer):
(JSC::SlotVisitor::appendUnbarrieredValue):
(JSC::SlotVisitor::appendUnbarrieredReadOnlyValue): Some renaming and un-inlining.

(JSC::SlotVisitor::appendUnbarrieredWeak): Don't null check our input.
The one true place where null checking happens is our out-of-line
code. All inline functions do only type conversions.

(JSC::SlotVisitor::append):
(JSC::SlotVisitor::appendValues):
(JSC::SlotVisitor::addWeakReferenceHarvester):
(JSC::SlotVisitor::addUnconditionalFinalizer):
(JSC::SlotVisitor::reportExtraMemoryVisited): Some renaming and un-inlining.

(JSC::SlotVisitor::internalAppend): Deleted.
(JSC::SlotVisitor::unconditionallyAppend): Deleted.
(JSC::SlotVisitor::addOpaqueRoot): Deleted.
(JSC::SlotVisitor::containsOpaqueRoot): Deleted.
(JSC::SlotVisitor::containsOpaqueRootTriState): Deleted.
(JSC::SlotVisitor::opaqueRootCount): Deleted.
(JSC::SlotVisitor::mergeOpaqueRootsIfNecessary): Deleted.
(JSC::SlotVisitor::mergeOpaqueRootsIfProfitable): Deleted.
(JSC::SlotVisitor::donate): Deleted.
(JSC::SlotVisitor::donateAndDrain): Deleted.
(JSC::SlotVisitor::copyLater): Deleted.

• runtime/JSString.h:

(JSC::JSString::finishCreation):
(JSC::JSString::setIs8Bit):
(JSC::JSString::isHashConsSingleton): Deleted.
(JSC::JSString::clearHashConsSingleton): Deleted.
(JSC::JSString::setHashConsSingleton): Deleted. More hash cons removal.

• runtime/VM.cpp:

(JSC::VM::VM):

• runtime/VM.h:

(JSC::VM::currentThreadIsHoldingAPILock):
(JSC::VM::apiLock):
(JSC::VM::haveEnoughNewStringsToHashCons): Deleted.
(JSC::VM::resetNewStringsSinceLastHashCons): Deleted. More hash cons removal.

File:

• trunk/Source/JavaScriptCore/heap/Heap.cpp (modified) (3 diffs)

trunk/Source/JavaScriptCore/heap/Heap.cpp

@@ -544 +544 @@
         m_opaqueRoots.clear();
 
-    m_shouldHashCons = m_vm->haveEnoughNewStringsToHashCons();
-
     m_parallelMarkersShouldExit = false;
 
@@ -896 +894 @@
     ASSERT(m_sharedMarkStack.isEmpty());
     m_weakReferenceHarvesters.removeAll();
-    if (m_shouldHashCons) {
-        m_vm->resetNewStringsSinceLastHashCons();
-        m_shouldHashCons = false;
-    }
 }
 
@@ -1018 +1012 @@
         return;
     const_cast<JSCell*>(cell)->setRemembered(true);
-    m_slotVisitor.unconditionallyAppend(const_cast<JSCell*>(cell));
+    m_slotVisitor.appendToMarkStack(const_cast<JSCell*>(cell));
 }