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. If we mask out the 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.
}
Space* owner() const {
- if ((reinterpret_cast<intptr_t>(owner_) & kFailureTagMask) ==
- kFailureTag) {
+ if ((reinterpret_cast<intptr_t>(owner_) & kPageHeaderTagMask) ==
+ kPageHeaderTag) {
return reinterpret_cast<Space*>(reinterpret_cast<intptr_t>(owner_) -
- kFailureTag);
+ kPageHeaderTag);
} else {
return NULL;
}
}
void set_owner(Space* space) {
- ASSERT((reinterpret_cast<intptr_t>(space) & kFailureTagMask) == 0);
- owner_ = reinterpret_cast<Address>(space) + kFailureTag;
- ASSERT((reinterpret_cast<intptr_t>(owner_) & kFailureTagMask) ==
- kFailureTag);
+ ASSERT((reinterpret_cast<intptr_t>(space) & kPageHeaderTagMask) == 0);
+ owner_ = reinterpret_cast<Address>(space) + kPageHeaderTag;
+ ASSERT((reinterpret_cast<intptr_t>(owner_) & kPageHeaderTagMask) ==
+ kPageHeaderTag);
}
base::VirtualMemory* reserved_memory() {