8341715: PPC64: ObjectMonitor::_owner should be reset unconditionally in nmethod unlocking

Reviewed-by: mdoerr, lucy

Author: reinrich

src/hotspot/cpu/ppc/macroAssembler_ppc.cpp

@@ -2651,7 +2651,19 @@ void MacroAssembler::compiler_fast_lock_object(ConditionRegister flag, Register
   // flag == NE indicates failure
   bind(success);
   inc_held_monitor_count(temp);
+#ifdef ASSERT
+  // Check that unlocked label is reached with flag == EQ.
+  Label flag_correct;
+  beq(flag, flag_correct);
+  stop("compiler_fast_lock_object: Flag != EQ");
+#endif
   bind(failure);
+#ifdef ASSERT
+  // Check that slow_path label is reached with flag == NE.
+  bne(flag, flag_correct);
+  stop("compiler_fast_lock_object: Flag != NE");
+  bind(flag_correct);
+#endif
 }
 
 void MacroAssembler::compiler_fast_unlock_object(ConditionRegister flag, Register oop, Register box,
@@ -2701,17 +2713,12 @@ void MacroAssembler::compiler_fast_unlock_object(ConditionRegister flag, Registe
   bind(object_has_monitor);
   STATIC_ASSERT(markWord::monitor_value <= INT_MAX);
   addi(current_header, current_header, -(int)markWord::monitor_value); // monitor
-  ld(temp,             in_bytes(ObjectMonitor::owner_offset()), current_header);
-
-  // In case of LM_LIGHTWEIGHT, we may reach here with (temp & ObjectMonitor::ANONYMOUS_OWNER) != 0.
-  // This is handled like owner thread mismatches: We take the slow path.
-  cmpd(flag, temp, R16_thread);
-  bne(flag, failure);
 
   ld(displaced_header, in_bytes(ObjectMonitor::recursions_offset()), current_header);
-
   addic_(displaced_header, displaced_header, -1);
   blt(CCR0, notRecursive); // Not recursive if negative after decrement.
+
+  // Recursive unlock
   std(displaced_header, in_bytes(ObjectMonitor::recursions_offset()), current_header);
   if (flag == CCR0) { // Otherwise, flag is already EQ, here.
     crorc(CCR0, Assembler::equal, CCR0, Assembler::equal); // Set CCR0 EQ
@@ -2752,7 +2759,19 @@ void MacroAssembler::compiler_fast_unlock_object(ConditionRegister flag, Registe
   // flag == NE indicates failure
   bind(success);
   dec_held_monitor_count(temp);
+#ifdef ASSERT
+  // Check that unlocked label is reached with flag == EQ.
+  Label flag_correct;
+  beq(flag, flag_correct);
+  stop("compiler_fast_unlock_object: Flag != EQ");
+#endif
   bind(failure);
+#ifdef ASSERT
+  // Check that slow_path label is reached with flag == NE.
+  bne(flag, flag_correct);
+  stop("compiler_fast_unlock_object: Flag != NE");
+  bind(flag_correct);
+#endif
 }
 
 void MacroAssembler::compiler_fast_lock_lightweight_object(ConditionRegister flag, Register obj, Register box,