src/hotspot/cpu/aarch64/c2_MacroAssembler_aarch64.cpp

*** 2252,5 ***
--- 2252,32 ---
        return true;
      }
    }
    return MacroAssembler::in_scratch_emit_size();
  }
+ 
+ void C2_MacroAssembler::load_nklass_compact(Register dst, Register obj, Register index, int scale, int disp) {
+   C2LoadNKlassStub* stub = new (Compile::current()->comp_arena()) C2LoadNKlassStub(dst);
+   Compile::current()->output()->add_stub(stub);
+ 
+   // Note: Don't clobber obj anywhere in that method!
+ 
+   // The incoming address is pointing into obj-start + klass_offset_in_bytes. We need to extract
+   // obj-start, so that we can load from the object's mark-word instead. Usually the address
+   // comes as obj-start in obj and klass_offset_in_bytes in disp. However, sometimes C2
+   // emits code that pre-computes obj-start + klass_offset_in_bytes into a register, and
+   // then passes that register as obj and 0 in disp. The following code extracts the base
+   // and offset to load the mark-word.
+   int offset = oopDesc::mark_offset_in_bytes() + disp - oopDesc::klass_offset_in_bytes();
+   if (index == noreg) {
+     ldr(dst, Address(obj, offset));
+   } else {
+     lea(dst, Address(obj, index, Address::lsl(scale)));
+     ldr(dst, Address(dst, offset));
+   }
+   // NOTE: We can't use tbnz here, because the target is sometimes too far away
+   // and cannot be encoded.
+   tst(dst, markWord::monitor_value);
+   br(Assembler::NE, stub->entry());
+   bind(stub->continuation());
+   lsr(dst, dst, markWord::klass_shift);
+ }