src/hotspot/cpu/x86/c1_MacroAssembler_x86.cpp

@@ -60,10 +60,14 @@
 
   // Load object header
   movptr(hdr, Address(obj, hdr_offset));
   // and mark it as unlocked
   orptr(hdr, markOopDesc::unlocked_value);
+  if (EnableValhalla && !UseBiasedLocking) {
+    // Mask always_locked bit such that we go to the slow path if object is a value type
+    andptr(hdr, ~markOopDesc::biased_lock_bit_in_place);
+  }
   // save unlocked object header into the displaced header location on the stack
   movptr(Address(disp_hdr, 0), hdr);
   // test if object header is still the same (i.e. unlocked), and if so, store the
   // displaced header address in the object header - if it is not the same, get the
   // object header instead

@@ -148,11 +152,12 @@
 }
 
 
 void C1_MacroAssembler::initialize_header(Register obj, Register klass, Register len, Register t1, Register t2) {
   assert_different_registers(obj, klass, len);
-  if (UseBiasedLocking && !len->is_valid()) {
+  if ((UseBiasedLocking || EnableValhalla) && !len->is_valid()) {
+    // Need to copy markOopDesc::always_locked_pattern for values.
     assert_different_registers(obj, klass, len, t1, t2);
     movptr(t1, Address(klass, Klass::prototype_header_offset()));
     movptr(Address(obj, oopDesc::mark_offset_in_bytes()), t1);
   } else {
     // This assumes that all prototype bits fit in an int32_t