src/hotspot/cpu/x86/interp_masm_x86.cpp

@@ -1,7 +1,7 @@
  /*
-  * Copyright (c) 1997, 2023, Oracle and/or its affiliates. All rights reserved.
+  * Copyright (c) 1997, 2024, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.

@@ -1250,12 +1250,10 @@
        const Register thread = r15_thread;
  #else
        const Register thread = lock_reg;
        get_thread(thread);
  #endif
-       // Load object header, prepare for CAS from unlocked to locked.
-       movptr(swap_reg, Address(obj_reg, oopDesc::mark_offset_in_bytes()));
        lightweight_lock(obj_reg, swap_reg, thread, tmp_reg, slow_case);
      } else if (LockingMode == LM_LEGACY) {
        // Load immediate 1 into swap_reg %rax
        movl(swap_reg, 1);
  

@@ -1369,24 +1367,17 @@
      // Free entry
      movptr(Address(lock_reg, BasicObjectLock::obj_offset()), NULL_WORD);
  
      if (LockingMode == LM_LIGHTWEIGHT) {
  #ifdef _LP64
-       const Register thread = r15_thread;
+       lightweight_unlock(obj_reg, swap_reg, r15_thread, header_reg, slow_case);
  #else
-       const Register thread = header_reg;
-       get_thread(thread);
+       // This relies on the implementation of lightweight_unlock being able to handle
+       // that the reg_rax and thread Register parameters may alias each other.
+       get_thread(swap_reg);
+       lightweight_unlock(obj_reg, swap_reg, swap_reg, header_reg, slow_case);
  #endif
-       // Handle unstructured locking.
-       Register tmp = swap_reg;
-       movl(tmp, Address(thread, JavaThread::lock_stack_top_offset()));
-       cmpptr(obj_reg, Address(thread, tmp, Address::times_1,  -oopSize));
-       jcc(Assembler::notEqual, slow_case);
-       // Try to swing header from locked to unlocked.
-       movptr(swap_reg, Address(obj_reg, oopDesc::mark_offset_in_bytes()));
-       andptr(swap_reg, ~(int32_t)markWord::lock_mask_in_place);
-       lightweight_unlock(obj_reg, swap_reg, header_reg, slow_case);
      } else if (LockingMode == LM_LEGACY) {
        // Load the old header from BasicLock structure
        movptr(header_reg, Address(swap_reg,
                                   BasicLock::displaced_header_offset_in_bytes()));