src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp

*** 4309,13 ***
    ldr(holder, Address(method, Method::const_offset()));                      // ConstMethod*
    ldr(holder, Address(holder, ConstMethod::constants_offset()));             // ConstantPool*
    ldr(holder, Address(holder, ConstantPool::pool_holder_offset()));          // InstanceKlass*
  }
  
  void MacroAssembler::load_klass(Register dst, Register src) {
    if (UseCompressedClassPointers) {
!     ldrw(dst, Address(src, oopDesc::klass_offset_in_bytes()));
      decode_klass_not_null(dst);
    } else {
      ldr(dst, Address(src, oopDesc::klass_offset_in_bytes()));
    }
  }
--- 4309,41 ---
    ldr(holder, Address(method, Method::const_offset()));                      // ConstMethod*
    ldr(holder, Address(holder, ConstMethod::constants_offset()));             // ConstantPool*
    ldr(holder, Address(holder, ConstantPool::pool_holder_offset()));          // InstanceKlass*
  }
  
+ // Loads the obj's Klass* into dst.
+ // Preserves all registers (incl src, rscratch1 and rscratch2).
+ void MacroAssembler::load_nklass(Register dst, Register src) {
+   assert(UseCompressedClassPointers, "expects UseCompressedClassPointers");
+ 
+   if (!UseCompactObjectHeaders) {
+     ldrw(dst, Address(src, oopDesc::klass_offset_in_bytes()));
+     return;
+   }
+ 
+   Label fast;
+ 
+   // Check if we can take the (common) fast path, if obj is unlocked.
+   ldr(dst, Address(src, oopDesc::mark_offset_in_bytes()));
+   tbz(dst, exact_log2(markWord::monitor_value), fast);
+ 
+   // Fetch displaced header
+   ldr(dst, Address(dst, OM_OFFSET_NO_MONITOR_VALUE_TAG(header)));
+ 
+   // Fast-path: shift and decode Klass*.
+   bind(fast);
+   lsr(dst, dst, markWord::klass_shift);
+ }
+ 
  void MacroAssembler::load_klass(Register dst, Register src) {
    if (UseCompressedClassPointers) {
!     if (UseCompactObjectHeaders) {
+       load_nklass(dst, src);
+     } else {
+       ldrw(dst, Address(src, oopDesc::klass_offset_in_bytes()));
+     }
      decode_klass_not_null(dst);
    } else {
      ldr(dst, Address(src, oopDesc::klass_offset_in_bytes()));
    }
  }

*** 4349,12 ***
    ldr(dst, Address(dst, mirror_offset));
    resolve_oop_handle(dst, tmp1, tmp2);
  }
  
  void MacroAssembler::cmp_klass(Register oop, Register trial_klass, Register tmp) {
    if (UseCompressedClassPointers) {
!     ldrw(tmp, Address(oop, oopDesc::klass_offset_in_bytes()));
      if (CompressedKlassPointers::base() == nullptr) {
        cmp(trial_klass, tmp, LSL, CompressedKlassPointers::shift());
        return;
      } else if (((uint64_t)CompressedKlassPointers::base() & 0xffffffff) == 0
                 && CompressedKlassPointers::shift() == 0) {
--- 4377,17 ---
    ldr(dst, Address(dst, mirror_offset));
    resolve_oop_handle(dst, tmp1, tmp2);
  }
  
  void MacroAssembler::cmp_klass(Register oop, Register trial_klass, Register tmp) {
+   assert_different_registers(oop, trial_klass, tmp);
    if (UseCompressedClassPointers) {
!     if (UseCompactObjectHeaders) {
+       load_nklass(tmp, oop);
+     } else {
+       ldrw(tmp, Address(oop, oopDesc::klass_offset_in_bytes()));
+     }
      if (CompressedKlassPointers::base() == nullptr) {
        cmp(trial_klass, tmp, LSL, CompressedKlassPointers::shift());
        return;
      } else if (((uint64_t)CompressedKlassPointers::base() & 0xffffffff) == 0
                 && CompressedKlassPointers::shift() == 0) {