src/hotspot/cpu/x86/x86_64.ad

@@ -4382,19 +4382,22 @@
    match(Set dst (LoadNKlass mem));
    effect(KILL cr);
    ins_cost(125);
    format %{
      "movl    $dst, $mem\t# compressed klass ptr, shifted\n\t"
-     "shrl    $dst, markWord::klass_shift_at_offset"
+     "shrl    $dst, markWord::klass_shift"
    %}
    ins_encode %{
+     // The incoming address is pointing into obj-start + Type::klass_offset(). We need to extract
+     // obj-start, so that we can load from the object's mark-word instead.
+     Register d = $dst$$Register;
+     Address  s = ($mem$$Address).plus_disp(-Type::klass_offset());
      if (UseAPX) {
-       __ eshrl($dst$$Register, $mem$$Address, markWord::klass_shift_at_offset, false);
-     }
-     else {
-       __ movl($dst$$Register, $mem$$Address);
-       __ shrl($dst$$Register, markWord::klass_shift_at_offset);
+       __ eshrl(d, s, markWord::klass_shift, false);
+     } else {
+       __ movl(d, s);
+       __ shrl(d, markWord::klass_shift);
      }
    %}
    ins_pipe(ialu_reg_mem);
  %}