Revert "Remove failure tag.".

TBR=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/398473002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22409 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/globals.h

@@ -216,6 +216,12 @@ const int kCodeAlignmentBits = 5;
 const intptr_t kCodeAlignment = 1 << kCodeAlignmentBits;
 const intptr_t kCodeAlignmentMask = kCodeAlignment - 1;
 
+// Tag information for Failure.
+// TODO(yangguo): remove this from space owner calculation.
+const int kFailureTag = 3;
+const int kFailureTagSize = 2;
+const intptr_t kFailureTagMask = (1 << kFailureTagSize) - 1;
+
 
 // Zap-value: The value used for zapping dead objects.
 // Should be a recognizable hex value tagged as a failure.
@@ -531,6 +537,9 @@ enum StateTag {
 #define HAS_SMI_TAG(value) \
   ((reinterpret_cast<intptr_t>(value) & kSmiTagMask) == kSmiTag)
 
+#define HAS_FAILURE_TAG(value) \
+  ((reinterpret_cast<intptr_t>(value) & kFailureTagMask) == kFailureTag)
+
 // OBJECT_POINTER_ALIGN returns the value aligned as a HeapObject pointer
 #define OBJECT_POINTER_ALIGN(value)                             \
   (((value) + kObjectAlignmentMask) & ~kObjectAlignmentMask)

src/spaces.h

@@ -312,11 +312,20 @@ class MemoryChunk {
   }
 
   Space* owner() const {
-    return owner_;
+    if ((reinterpret_cast<intptr_t>(owner_) & kFailureTagMask) ==
+        kFailureTag) {
+      return reinterpret_cast<Space*>(reinterpret_cast<intptr_t>(owner_) -
+                                      kFailureTag);
+    } else {
+      return NULL;
+    }
   }
 
   void set_owner(Space* space) {
-    owner_ = space;
+    ASSERT((reinterpret_cast<intptr_t>(space) & kFailureTagMask) == 0);
+    owner_ = reinterpret_cast<Address>(space) + kFailureTag;
+    ASSERT((reinterpret_cast<intptr_t>(owner_) & kFailureTagMask) ==
+           kFailureTag);
   }
 
   base::VirtualMemory* reserved_memory() {
@@ -682,7 +691,10 @@ class MemoryChunk {
 
   // If the chunk needs to remember its memory reservation, it is stored here.
   base::VirtualMemory reservation_;
-  Space* owner_;
+  // The identity of the owning space.  This is tagged as a failure pointer, but
+  // no failure can be in an object, so this can be distinguished from any entry
+  // in a fixed array.
+  Address owner_;
   Heap* heap_;
   // Used by the store buffer to keep track of which pages to mark scan-on-
   // scavenge.