sketch of finalizer/weak reference overhaul; type generator bugfixes involving array member layout

src/builtin.cpp

@@ -83,8 +83,8 @@ arraycopy(Thread* t, jobject src, jint srcOffset, jobject dst, jint dstOffset,
           }
         }
 
-        int32_t sl = cast<uint32_t>(s, offset * BytesPerWord);
-        int32_t dl = cast<uint32_t>(d, offset * BytesPerWord);
+        intptr_t sl = cast<uintptr_t>(s, offset * BytesPerWord);
+        intptr_t dl = cast<uintptr_t>(d, offset * BytesPerWord);
         if (LIKELY(srcOffset >= 0 and srcOffset + length <= sl and
                    dstOffset >= 0 and dstOffset + length < dl))
         {

src/heap.cpp

@@ -1412,6 +1412,31 @@ makeHeap(System* system)
       }
     }
 
+    virtual Status status(void* p) {
+      p = mask(p);
+
+      if (c.nextGen1.contains(p)) {
+        return Reachable;
+      } else if (c.nextGen2.contains(p)
+                 or (c.gen2.contains(p)
+                     and c.gen2.indexOf(p) >= c.gen2Base))
+      {
+        return Tenured;
+      } else if (wasCollected(&c, p)) {
+        return Reachable;
+      } else {
+        return Unreachable;
+      }
+    }
+
+    virtual CollectionType collectionType() {
+      if (c.mode == ::MinorCollection) {
+        return MinorCollection;
+      } else {
+        return MajorCollection;
+      }
+    }
+
     Context c;
   };
   

src/heap.h

@@ -12,6 +12,12 @@ class Heap {
     MajorCollection
   };
 
+  enum Status {
+    Reachable,
+    Unreachable,
+    Tenured
+  };
+
   class Visitor {
    public:
     virtual ~Visitor() { }
@@ -39,6 +45,8 @@ class Heap {
   virtual bool needsMark(void** p) = 0;
   virtual void mark(void** p) = 0;
   virtual void* follow(void* p) = 0;
+  virtual Status status(void* p) = 0;
+  virtual CollectionType collectionType() = 0;
   virtual void dispose() = 0;
 };
 

src/machine.cpp

@@ -127,6 +127,145 @@ visitRoots(Thread* t, Heap::Visitor* v)
   }
 }
 
+void
+postVisit(Thread* t, Heap::Visitor* v)
+{
+  Machine* m = t->vm;
+
+  object firstNewTenuredFinalizer = 0;
+  object lastNewTenuredFinalizer = 0;
+
+  for (object* p = &(m->finalizers); *p;) {
+    v->visit(p);
+
+    if (m->heap->status(finalizerTarget(t, *p)) == Heap::Unreachable) {
+      // target is unreachable - queue it up for finalization
+
+      v->visit(&finalizerTarget(t, *p));
+
+      object finalizer = *p;
+      *p = finalizerNext(t, finalizer);
+      finalizerNext(t, finalizer) = m->finalizeQueue;
+      m->finalizeQueue = finalizer;
+    } else {
+      // target is reachable
+
+      v->visit(&finalizerTarget(t, *p));
+
+      if (m->heap->status(*p) == Heap::Tenured) {
+        // the finalizer is tenured, so we remove it from
+        // m->finalizers and later add it to m->tenuredFinalizers
+
+        if (lastNewTenuredFinalizer == 0) {
+          lastNewTenuredFinalizer = *p;
+        }
+
+        object finalizer = *p;
+        *p = finalizerNext(t, finalizer);
+        finalizerNext(t, finalizer) = firstNewTenuredFinalizer;
+        firstNewTenuredFinalizer = finalizer;
+      } else {
+        p = &finalizerNext(t, *p);
+      }
+    }
+  }
+
+  object firstNewTenuredWeakReference = 0;
+  object lastNewTenuredWeakReference = 0;
+
+  for (object* p = &(m->weakReferences); *p;) {
+    if (m->heap->status(*p) == Heap::Unreachable) {
+      // reference is unreachable - remove it from the list
+
+      *p = jreferenceNext(t, *p);
+    } else if (m->heap->status(jreferenceTarget(t, *p)) == Heap::Unreachable) {
+      // target is unreachable - clear the reference and remove it
+      // from the list
+
+      jreferenceTarget(t, *p) = 0;
+      *p = jreferenceNext(t, *p);
+    } else {
+      // both reference and target are reachable
+
+      v->visit(&jreferenceTarget(t, *p));
+      v->visit(p);
+
+      if (m->heap->status(*p) == Heap::Tenured) {
+        // the reference is tenured, so we remove it from
+        // m->weakReferences and later add it to
+        // m->tenuredWeakReferences
+
+        if (lastNewTenuredWeakReference == 0) {
+          lastNewTenuredWeakReference = *p;
+        }
+
+        object reference = *p;
+        *p = jreferenceNext(t, reference);
+        jreferenceNext(t, reference) = firstNewTenuredWeakReference;
+        firstNewTenuredWeakReference = reference;
+      } else {
+        p = &jreferenceNext(t, *p);
+      }
+    }
+  }
+
+  if (m->heap->collectionType() == Heap::MajorCollection) {
+    for (object* p = &(m->tenuredFinalizers); *p;) {
+      v->visit(p);
+
+      if (m->heap->status(finalizerTarget(t, *p)) == Heap::Unreachable) {
+        // target is unreachable - queue it up for finalization
+
+        v->visit(&finalizerTarget(t, *p));
+
+        object finalizer = *p;
+        *p = finalizerNext(t, finalizer);
+        finalizerNext(t, finalizer) = m->finalizeQueue;
+        m->finalizeQueue = finalizer;
+      } else {
+        // target is reachable
+
+        v->visit(&finalizerTarget(t, *p));
+
+        p = &finalizerNext(t, *p);
+      }
+    }
+
+    for (object* p = &(m->tenuredWeakReferences); *p;) {
+      if (m->heap->status(*p) == Heap::Unreachable) {
+        // reference is unreachable - remove it from the list
+
+        *p = jreferenceNext(t, *p);
+      } else if (m->heap->status(jreferenceTarget(t, *p))
+                 == Heap::Unreachable)
+      {
+        // target is unreachable - clear the reference and remove it
+        // from the list
+
+        jreferenceTarget(t, *p) = 0;
+        *p = jreferenceNext(t, *p);
+      } else {
+        // target is reachable
+
+        v->visit(&jreferenceTarget(t, *p));
+        v->visit(p);
+
+        p = &jreferenceNext(t, *p);
+      }
+    }
+  }
+
+  if (lastNewTenuredFinalizer) {
+    finalizerNext(t, lastNewTenuredFinalizer) = m->tenuredFinalizers;
+    m->tenuredFinalizers = lastNewTenuredFinalizer;
+  }
+
+  if (lastNewTenuredWeakReference) {
+    jreferenceNext(t, lastNewTenuredWeakReference) = m->tenuredWeakReferences;
+    m->tenuredWeakReferences = lastNewTenuredWeakReference;
+  }
+}
+
 void
 postCollect(Thread* t)
 {
@@ -160,37 +299,7 @@ collect(Thread* t, Heap::CollectionType type)
         ::visitRoots(t, v);
       }
 
-      Thread* t = m->rootThread;
-      for (object* f = &(m->finalizers); *f;) {
-        object o = finalizerTarget(t, *f);
-        if (m->heap->follow(o) == o) {
-          // object has not been collected
-          object x = *f;
-          *f = finalizerNext(t, x);
-          finalizerNext(t, x) = m->doomed;
-          m->doomed = x;
-        } else {
-          f = &finalizerNext(t, *f);
-        }
-      }
-
-      v->visit(&(m->finalizers));
-      v->visit(&(m->doomed));
-
-      for (object p = m->weakReferences; p;) {
-        object o = jreferenceTarget(t, p);
-        object followed = m->heap->follow(o);
-        if (followed == o) {
-          // object has not been collected
-          jreferenceTarget(t, p) = 0;
-        } else {
-          jreferenceTarget(t, p) = followed;
-        }
-
-        object last = p;
-        p = jreferenceNext(t, p);
-        jreferenceNext(t, last) = 0;
-      }
+      postVisit(m->rootThread, v);
     }
 
     virtual unsigned sizeInWords(object o) {
@@ -256,7 +365,8 @@ collect(Thread* t, Heap::CollectionType type)
         unsigned fixedSize = classFixedSize(t, class_);
         unsigned arrayElementSize = classArrayElementSize(t, class_);
         unsigned arrayLength
-          = (arrayElementSize ? cast<uint32_t>(p, fixedSize - 4) : 0);
+          = (arrayElementSize ?
+             cast<uintptr_t>(p, fixedSize - BytesPerWord) : 0);
 
         int mask[intArrayLength(t, objectMask)];
         memcpy(mask, &intArrayBody(t, objectMask, 0),
@@ -317,13 +427,11 @@ collect(Thread* t, Heap::CollectionType type)
 
   postCollect(m->rootThread);
 
-  for (object f = m->doomed; f; f = finalizerNext(t, f)) {
+  for (object f = m->finalizeQueue; f; f = finalizerNext(t, f)) {
     reinterpret_cast<void (*)(Thread*, object)>(finalizerFinalize(t, f))
       (t, finalizerTarget(t, f));
   }
-  m->doomed = 0;
-
-  m->weakReferences = 0;
+  m->finalizeQueue = 0;
 
   killZombies(t, m->rootThread);
 }
@@ -372,8 +480,9 @@ Machine::Machine(System* system, Heap* heap, ClassFinder* classFinder):
   monitorMap(0),
   types(0),
   finalizers(0),
-  doomed(0),
-  weakReferences(0),
+  tenuredFinalizers(0),
+  finalizeQueue(0),
+  tenuredWeakReferences(0),
   unsafe(false)
 {
   jni::populate(&jniEnvVTable);
@@ -912,6 +1021,10 @@ objectMonitor(Thread* t, object o)
   }
 }
 
+void
+noop()
+{ }
+
 #include "type-constructors.cpp"
 
 } // namespace vm

src/machine.h

@@ -1076,6 +1076,9 @@ strcmp(const int8_t* a, const int8_t* b)
                   reinterpret_cast<const char*>(b));
 }
 
+void
+noop();
+
 class Machine {
  public:
   enum {
@@ -1108,8 +1111,10 @@ class Machine {
   object monitorMap;
   object types;
   object finalizers;
-  object doomed;
+  object tenuredFinalizers;
+  object finalizeQueue;
   object weakReferences;
+  object tenuredWeakReferences;
   bool unsafe;
   JNIEnvVTable jniEnvVTable;
 };
@@ -1639,9 +1644,16 @@ hash(const int8_t* s, unsigned length)
 inline unsigned
 baseSize(Thread* t, object o, object class_)
 {
+  if (classArrayElementSize(t, class_)) {
+    noop();
+    if (cast<uintptr_t>(o, classFixedSize(t, class_) - BytesPerWord)) {
+      noop();
+    }
+  }
+
   return divide(classFixedSize(t, class_), BytesPerWord)
     + divide(classArrayElementSize(t, class_)
-             * cast<uint32_t>(o, classFixedSize(t, class_) - 4),
+             * cast<uintptr_t>(o, classFixedSize(t, class_) - BytesPerWord),
              BytesPerWord);
 }
 

src/type-generator.cpp

@@ -342,7 +342,7 @@ addMember(Object* o, Object* member)
   case Object::Type: case Object::Pod:
     if (member->type == Object::Array) {
       static_cast<Type*>(o)->members.append
-        (Scalar::make(o, 0, "uint32_t", "length", sizeof(uint32_t)));
+        (Scalar::make(o, 0, "uintptr_t", "length", sizeof(uintptr_t)));
     }
     static_cast<Type*>(o)->members.append(member);
     break;
@@ -1390,7 +1390,7 @@ typeFixedSize(Object* type)
     Object* m = it.next();
     switch (m->type) {
     case Object::Scalar: {
-      length = pad(it.offset() + it.space());
+      length = pad(it.offset() + it.size());
     } break;
 
     case Object::Array: break;
@@ -1521,7 +1521,7 @@ writeInitializations(Output* out, Object* declarations)
 
   out->write("t->vm->types = allocate(t, pad((");
   out->write(count);
-  out->write(" * sizeof(void*)) + 4 + sizeof(void*)));\n");
+  out->write(" * sizeof(void*)) + sizeof(uintptr_t) + sizeof(void*)));\n");
   out->write("cast<object>(t->vm->types, 0) = 0;\n");
   out->write("arrayLength(t, t->vm->types) = ");
   out->write(count);

src/types.def

@@ -80,9 +80,9 @@
   (object third))
 
 (type finalizer
-  (object target)
+  (void* target)
   (void* finalize)
-  (object next))
+  (void* next))
 
 (type hashMap
   (uint32_t size)