Remove slots that point to unboxed doubles from the StoreBuffer/SlotsBuffer.

src/heap/mark-compact.cc

Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index 77d084266264fbd78f56bc16115818a92b223ff4..be9f9a971c8fdd513f8138b7ef4c9714734bd7f8 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -712,6 +712,7 @@ void MarkCompactCollector::CollectEvacuationCandidates(PagedSpace* space) {
 
   int count = 0;
   int fragmentation = 0;
+  int page_number = 0;
   Candidate* least = NULL;
 
   PageIterator it(space);
@@ -726,9 +727,16 @@ void MarkCompactCollector::CollectEvacuationCandidates(PagedSpace* space) {
     CHECK(p->slots_buffer() == NULL);
 
     if (FLAG_stress_compaction) {
-      unsigned int counter = space->heap()->ms_count();
-      uintptr_t page_number = reinterpret_cast<uintptr_t>(p) >> kPageSizeBits;
-      if ((counter & 1) == (page_number & 1)) fragmentation = 1;
+      if (FLAG_manual_evacuation_candidates_selection) {
+        if (p->IsFlagSet(MemoryChunk::FORCE_EVACUATION_CANDIDATE_FOR_TESTING)) {
+          p->ClearFlag(MemoryChunk::FORCE_EVACUATION_CANDIDATE_FOR_TESTING);
+          fragmentation = 1;
+        }
+      } else {
+        unsigned int counter = space->heap()->ms_count();
+        if ((counter & 1) == (page_number & 1)) fragmentation = 1;
+        page_number++;
+      }
     } else if (mode == REDUCE_MEMORY_FOOTPRINT) {
       // Don't try to release too many pages.
       if (estimated_release >= over_reserved) {
@@ -4281,6 +4289,40 @@ bool SlotsBuffer::AddTo(SlotsBufferAllocator* allocator,
 }
 
 
+void SlotsBuffer::RemoveSlot(SlotsBuffer* buffer, ObjectSlot slot_to_remove) {

[Hannes Payer (out of office), 2015/03/03 09:48:53]

I think it would be more efficient to just clear the slot instead of moving
everything to the left.

[Igor Sheludko, 2015/03/04 14:54:19]

Done.

+  DCHECK(!IsTypedSlot(slot_to_remove));
+  while (buffer != NULL) {
+    intptr_t written = 0;
+    intptr_t length = buffer->idx_;
+
+    ObjectSlot* slots = buffer->slots_;
+    for (int slot_idx = 0; slot_idx < length; ++slot_idx) {
+      ObjectSlot slot = slots[slot_idx];
+      if (!IsTypedSlot(slot)) {
+        if (slot != slot_to_remove) {
+          if (written != slot_idx) slots[written] = slot;
+          ++written;
+        }
+      } else {
+        ++slot_idx;
+        DCHECK(slot_idx < length);
+        ObjectSlot typed_slot = slots[slot_idx];
+        if (typed_slot != slot_to_remove) {
+          if (written != slot_idx - 1) {
+            slots[written++] = slot;
+            slots[written++] = typed_slot;
+          } else {
+            written += 2;
+          }
+        }
+      }
+    }
+    buffer->idx_ = written;
+    buffer = buffer->next_;
+  }
+}
+
+
 static inline SlotsBuffer::SlotType SlotTypeForRMode(RelocInfo::Mode rmode) {
   if (RelocInfo::IsCodeTarget(rmode)) {
     return SlotsBuffer::CODE_TARGET_SLOT;