Rename failure tag to page owner tag and add proper description.

src/globals.h

Index: src/globals.h
diff --git a/src/globals.h b/src/globals.h
index bddd4ef056c0538447bc7982d046dc789b142755..b4baabc6943aaf167862dc7b6539f921e394f303 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -216,11 +216,15 @@ 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;
+// The owner field of a page is tagged with the page header tag. We need that
+// to find out if a slot is part of a large object, i.e., if we mask out the

[Michael Starzinger, 2014/07/28 16:47:27]

nit: Long sentence is long. Can we split it up?

[Hannes Payer (out of office), 2014/07/28 18:53:19]

Done.

+// lower 0xfffff bits (1M pages), go to the owner offset, and see that this
+// field is tagged with the page header tag, we can just look up the owner.
+// Otherwise, we know that we are somewhere (not within the first 1M) in a
+// large object.
+const int kPageHeaderTag = 3;
+const int kPageHeaderTagSize = 2;
+const intptr_t kPageHeaderTagMask = (1 << kPageHeaderTagSize) - 1;
 
 
 // Zap-value: The value used for zapping dead objects.