[heap] Fix mark bits for partially compacted pages.

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 8a32ba8bda28d08c91b6876a3c4d9ed038fad9f6..ec0f7f02d911a900cd56f5c0b0fa925107706aaf 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -3353,6 +3353,13 @@ bool MarkCompactCollector::EvacuateLiveObjectsFromPage(
       HeapObject* target_object = nullptr;
       AllocationResult allocation = target_space->AllocateRaw(size, alignment);
       if (!allocation.To(&target_object)) {
+        // We need to abort compaction for this page. Make sure that we reset
+        // the mark bits for objects that have already been migrated.
+        if (i > 0) {
+          p->markbits()->ClearTillIndex(

[ulan, 2015/10/08 12:43:14]

As discussed offline, let's change the name to something like ClearRange.

[Michael Lippautz, 2015/10/08 12:57:51]

ClearRange it is.

+              p->AddressToMarkbitIndex(p->area_start()),
+              p->AddressToMarkbitIndex(object_addr));
+        }
         return false;
       }