- Promote objects from new gen to old space if they survived a scavenge.

vm/scavenger.h

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_SCAVENGER_H_
 #define VM_SCAVENGER_H_
 
+#include "vm/assert.h"
+#include "vm/flags.h"
 #include "vm/globals.h"
-#include "vm/object.h"
+#include "vm/raw_object.h"
 #include "vm/utils.h"
 #include "vm/virtual_memory.h"
+#include "vm/visitor.h"
 
 namespace dart {
 
 // Forward declarations.
 class Heap;
 class Isolate;
 
+DECLARE_FLAG(bool, gc_at_alloc);
+
 class Scavenger {
  public:
   Scavenger(Heap* heap, intptr_t max_capacity, uword object_alignment);
   ~Scavenger();
 
   // Check whether this Scavenger contains this address.
   // During scavenging both the to and from spaces contain "legal" objects.
   // During a scavenge this function only returns true for addresses that will
   // be part of the surviving objects.
   bool Contains(uword addr) const {
@@ skipping 38 matching lines @@
   void VisitObjectPointers(ObjectPointerVisitor* visitor) const;
 
  private:
   uword FirstObjectStart() const { return to_->start() | object_alignment_; }
   void Prologue();
   void IterateRoots(Isolate* isolate, ObjectPointerVisitor* visitor);
   void IterateWeakRoots(Isolate* isolate, ObjectPointerVisitor* visitor);
   void ProcessToSpace(ObjectPointerVisitor* visitor);
   void Epilogue();
 
+  // During a scavenge we need to remember the promoted objects.
+  // This is implemented as a stack of objects at the end of the to space. As

[siva, 2011/12/22 23:48:38]

As object sizes are always greater than sizeof(uword) and promoted objects do
not consume space

[Ivan Posva, 2011/12/23 00:12:06]

Done.

+  // promoted objects will not consume space in the to space they leave enough
+  // room for this stack.
+  void PushToPromotedStack(uword addr) {
+    end_ -= sizeof(addr);
+    ASSERT(end_ > top_);
+    *reinterpret_cast<uword*>(end_) = addr;
+  }
+  uword PopFromPromotedStack() {
+    uword result = *reinterpret_cast<uword*>(end_);
+    end_ += sizeof(result);
+    ASSERT(end_ <= to_->end());
+    return result;
+  }
+  bool PromotedStackHasMore() const {
+    return end_ < to_->end();
+  }
+
   VirtualMemory* space_;
   MemoryRegion* to_;
   MemoryRegion* from_;
 
   Heap* heap_;
 
   // Current allocation top and end. These values are being accessed directly
   // from generated code.
   uword top_;
   uword end_;
 
+  // Objects below this address have survived a scavenge.
+  uword survivor_end_;
+
   // All object are aligned to this value.
   uword object_alignment_;
 
   // Scavenge cycle count.
   int count_;
   // Keep track whether a scavenge is currently running.
   bool scavenging_;
+  // Keep track whether the scavenge had a promotion failure.
+  bool had_promotion_failure_;
 
   friend class ScavengerVisitor;
   friend class ScavengerWeakVisitor;
 
   DISALLOW_COPY_AND_ASSIGN(Scavenger);
 };
 
 }  // namespace dart
 
 #endif  // VM_SCAVENGER_H_