src/hotspot/share/runtime/arguments.cpp

@@ -1485,10 +1485,27 @@
  
  // NOTE: set_use_compressed_klass_ptrs() must be called after calling
  // set_use_compressed_oops().
  void Arguments::set_use_compressed_klass_ptrs() {
  #ifdef _LP64
+ 
+   if (UseCompactObjectHeaders) {
+     // 512 byte alignment, 22-bit values (Lilliput)
+     LogKlassAlignmentInBytes = 9;
+     MaxNarrowKlassPointerBits = 22;
+   } else {
+     // Traditional: 8 byte alignment, 32-bit values
+     LogKlassAlignmentInBytes = 3;
+     MaxNarrowKlassPointerBits = 32;
+   }
+ 
+   KlassAlignmentInBytes = 1 << LogKlassAlignmentInBytes;
+   assert(is_aligned(KlassAlignmentInBytes, BytesPerWord), "Must be at least word-sized");
+   KlassAlignmentInWords = KlassAlignmentInBytes / BytesPerWord;
+   NarrowKlassPointerBitMask = ((((uint64_t)1) << MaxNarrowKlassPointerBits) - 1);
+   KlassEncodingMetaspaceMax = UCONST64(1) << (MaxNarrowKlassPointerBits + LogKlassAlignmentInBytes);
+ 
    // On some architectures, the use of UseCompressedClassPointers implies the use of
    // UseCompressedOops. The reason is that the rheap_base register of said platforms
    // is reused to perform some optimized spilling, in order to use rheap_base as a
    // temp register. But by treating it as any other temp register, spilling can typically
    // be completely avoided instead. So it is better not to perform this trick. And by

@@ -1503,11 +1520,20 @@
      if (CompressedClassSpaceSize > KlassEncodingMetaspaceMax) {
        warning("CompressedClassSpaceSize is too large for UseCompressedClassPointers");
        FLAG_SET_DEFAULT(UseCompressedClassPointers, false);
      }
    }
- #endif // _LP64
+ 
+   // Assert validity of compressed class space size. User arg should have been checked at this point
+   // (see CompressedClassSpaceSizeConstraintFunc()), so no need to be nice about it, this fires in
+   // case the default is wrong.
+   // TODO: This is placed wrong. The CompressedClassSpaceSizeFunc is done after ergo, but this
+   // assert is during ergo.
+   // assert(CompressedClassSpaceSize <= Metaspace::max_class_space_size(),
+   //        "CompressedClassSpaceSize " SIZE_FORMAT " too large (max: " SIZE_FORMAT ")",
+   //        CompressedClassSpaceSize, Metaspace::max_class_space_size());
+ #endif
  }
  
  void Arguments::set_conservative_max_heap_alignment() {
    // The conservative maximum required alignment for the heap is the maximum of
    // the alignments imposed by several sources: any requirements from the heap

@@ -3101,10 +3127,26 @@
  
  #ifndef CAN_SHOW_REGISTERS_ON_ASSERT
    UNSUPPORTED_OPTION(ShowRegistersOnAssert);
  #endif // CAN_SHOW_REGISTERS_ON_ASSERT
  
+ #ifdef _LP64
+   if (UseCompactObjectHeaders && FLAG_IS_CMDLINE(UseCompressedClassPointers) && !UseCompressedClassPointers) {
+     // If user specifies -UseCompressedClassPointers, disable compact headers with a warning.
+     warning("Compact object headers require compressed class pointers. Disabling compact object headers.");
+     FLAG_SET_DEFAULT(UseCompactObjectHeaders, false);
+   }
+ 
+   if (UseCompactObjectHeaders && LockingMode == LM_LEGACY) {
+     FLAG_SET_DEFAULT(LockingMode, LM_LIGHTWEIGHT);
+   }
+ 
+   if (!UseCompactObjectHeaders) {
+     FLAG_SET_DEFAULT(UseSharedSpaces, false);
+   }
+ #endif
+ 
    return JNI_OK;
  }
  
  // Helper class for controlling the lifetime of JavaVMInitArgs
  // objects.  The contents of the JavaVMInitArgs are guaranteed to be