1599   }
1600 }
1601 
1602 size_t Arguments::max_heap_for_compressed_oops() {
1603   // Avoid sign flip.
1604   assert(OopEncodingHeapMax > (uint64_t)os::vm_page_size(), "Unusual page size");
1605   // We need to fit both the NULL page and the heap into the memory budget, while
1606   // keeping alignment constraints of the heap. To guarantee the latter, as the
1607   // NULL page is located before the heap, we pad the NULL page to the conservative
1608   // maximum alignment that the GC may ever impose upon the heap.
1609   size_t displacement_due_to_null_page = align_up((size_t)os::vm_page_size(),
1610                                                   _conservative_max_heap_alignment);
1611 
1612   LP64_ONLY(return OopEncodingHeapMax - displacement_due_to_null_page);
1613   NOT_LP64(ShouldNotReachHere(); return 0);
1614 }
1615 
1616 void Arguments::set_use_compressed_oops() {
1617 #ifndef ZERO
1618 #ifdef _LP64




1619   // MaxHeapSize is not set up properly at this point, but
1620   // the only value that can override MaxHeapSize if we are
1621   // to use UseCompressedOops is InitialHeapSize.
1622   size_t max_heap_size = MAX2(MaxHeapSize, InitialHeapSize);
1623 
1624   if (max_heap_size <= max_heap_for_compressed_oops()) {
1625 #if !defined(COMPILER1) || defined(TIERED)
1626     if (FLAG_IS_DEFAULT(UseCompressedOops)) {
1627       FLAG_SET_ERGO(bool, UseCompressedOops, true);
1628     }
1629 #endif
1630   } else {
1631     if (UseCompressedOops && !FLAG_IS_DEFAULT(UseCompressedOops)) {
1632       warning("Max heap size too large for Compressed Oops");
1633       FLAG_SET_DEFAULT(UseCompressedOops, false);
1634       FLAG_SET_DEFAULT(UseCompressedClassPointers, false);
1635     }
1636   }
1637 #endif // _LP64
1638 #endif // ZERO

1599   }
1600 }
1601 
1602 size_t Arguments::max_heap_for_compressed_oops() {
1603   // Avoid sign flip.
1604   assert(OopEncodingHeapMax > (uint64_t)os::vm_page_size(), "Unusual page size");
1605   // We need to fit both the NULL page and the heap into the memory budget, while
1606   // keeping alignment constraints of the heap. To guarantee the latter, as the
1607   // NULL page is located before the heap, we pad the NULL page to the conservative
1608   // maximum alignment that the GC may ever impose upon the heap.
1609   size_t displacement_due_to_null_page = align_up((size_t)os::vm_page_size(),
1610                                                   _conservative_max_heap_alignment);
1611 
1612   LP64_ONLY(return OopEncodingHeapMax - displacement_due_to_null_page);
1613   NOT_LP64(ShouldNotReachHere(); return 0);
1614 }
1615 
1616 void Arguments::set_use_compressed_oops() {
1617 #ifndef ZERO
1618 #ifdef _LP64
1619   if(AllocateOldGenAt != NULL) {
1620     FLAG_SET_ERGO(bool, UseCompressedOops, false);
1621     return;
1622   }
1623   // MaxHeapSize is not set up properly at this point, but
1624   // the only value that can override MaxHeapSize if we are
1625   // to use UseCompressedOops is InitialHeapSize.
1626   size_t max_heap_size = MAX2(MaxHeapSize, InitialHeapSize);
1627 
1628   if (max_heap_size <= max_heap_for_compressed_oops()) {
1629 #if !defined(COMPILER1) || defined(TIERED)
1630     if (FLAG_IS_DEFAULT(UseCompressedOops)) {
1631       FLAG_SET_ERGO(bool, UseCompressedOops, true);
1632     }
1633 #endif
1634   } else {
1635     if (UseCompressedOops && !FLAG_IS_DEFAULT(UseCompressedOops)) {
1636       warning("Max heap size too large for Compressed Oops");
1637       FLAG_SET_DEFAULT(UseCompressedOops, false);
1638       FLAG_SET_DEFAULT(UseCompressedClassPointers, false);
1639     }
1640   }
1641 #endif // _LP64
1642 #endif // ZERO