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

vm/scavenger.h

Index: vm/scavenger.h
===================================================================
--- vm/scavenger.h	(revision 2792)
+++ vm/scavenger.h	(working copy)
@@ -5,10 +5,13 @@
 #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 {
 
@@ -16,6 +19,8 @@
 class Heap;
 class Isolate;
 
+DECLARE_FLAG(bool, gc_at_alloc);
+
 class Scavenger {
  public:
   Scavenger(Heap* heap, intptr_t max_capacity, uword object_alignment);
@@ -74,6 +79,25 @@
   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
+  // object sizes are always greater than sizeof(uword) and promoted objects do
+  // 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_;
@@ -85,6 +109,9 @@
   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_;
 
@@ -92,6 +119,8 @@
   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;