79
80 void C2FastUnlockLightweightStub::emit(C2_MacroAssembler& masm) {
81 assert(_t == rax, "must be");
82
83 Label restore_held_monitor_count_and_slow_path;
84
85 { // Restore lock-stack and handle the unlock in runtime.
86
87 __ bind(_push_and_slow_path);
88 #ifdef ASSERT
89 // The obj was only cleared in debug.
90 __ movl(_t, Address(_thread, JavaThread::lock_stack_top_offset()));
91 __ movptr(Address(_thread, _t), _obj);
92 #endif
93 __ addl(Address(_thread, JavaThread::lock_stack_top_offset()), oopSize);
94 }
95
96 { // Restore held monitor count and slow path.
97
98 __ bind(restore_held_monitor_count_and_slow_path);
99 // Restore held monitor count.
100 __ increment(Address(_thread, JavaThread::held_monitor_count_offset()));
101 // increment will always result in ZF = 0 (no overflows).
102 __ jmp(slow_path_continuation());
103 }
104
105 { // Handle monitor medium path.
106
107 __ bind(_check_successor);
108
109 Label fix_zf_and_unlocked;
110 const Register monitor = _mark;
111
112 #ifndef _LP64
113 __ jmpb(restore_held_monitor_count_and_slow_path);
114 #else // _LP64
115 // successor null check.
116 __ cmpptr(Address(monitor, OM_OFFSET_NO_MONITOR_VALUE_TAG(succ)), NULL_WORD);
117 __ jccb(Assembler::equal, restore_held_monitor_count_and_slow_path);
118
119 // Release lock.
120 __ movptr(Address(monitor, OM_OFFSET_NO_MONITOR_VALUE_TAG(owner)), NULL_WORD);
121
122 // Fence.
123 // Instead of MFENCE we use a dummy locked add of 0 to the top-of-stack.
124 __ lock(); __ addl(Address(rsp, 0), 0);
125
126 // Recheck successor.
127 __ cmpptr(Address(monitor, OM_OFFSET_NO_MONITOR_VALUE_TAG(succ)), NULL_WORD);
128 // Observed a successor after the release -> fence we have handed off the monitor
129 __ jccb(Assembler::notEqual, fix_zf_and_unlocked);
130
131 // Try to relock, if it fails the monitor has been handed over
132 // TODO: Caveat, this may fail due to deflation, which does
133 // not handle the monitor handoff. Currently only works
134 // due to the responsible thread.
135 __ xorptr(rax, rax);
136 __ lock(); __ cmpxchgptr(_thread, Address(monitor, OM_OFFSET_NO_MONITOR_VALUE_TAG(owner)));
137 __ jccb (Assembler::equal, restore_held_monitor_count_and_slow_path);
138 #endif
139
140 __ bind(fix_zf_and_unlocked);
141 __ xorl(rax, rax);
142 __ jmp(unlocked_continuation());
143 }
144 }
145
146 #undef __
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79
80 void C2FastUnlockLightweightStub::emit(C2_MacroAssembler& masm) {
81 assert(_t == rax, "must be");
82
83 Label restore_held_monitor_count_and_slow_path;
84
85 { // Restore lock-stack and handle the unlock in runtime.
86
87 __ bind(_push_and_slow_path);
88 #ifdef ASSERT
89 // The obj was only cleared in debug.
90 __ movl(_t, Address(_thread, JavaThread::lock_stack_top_offset()));
91 __ movptr(Address(_thread, _t), _obj);
92 #endif
93 __ addl(Address(_thread, JavaThread::lock_stack_top_offset()), oopSize);
94 }
95
96 { // Restore held monitor count and slow path.
97
98 __ bind(restore_held_monitor_count_and_slow_path);
99 __ bind(_slow_path);
100 // Restore held monitor count.
101 __ increment(Address(_thread, JavaThread::held_monitor_count_offset()));
102 // increment will always result in ZF = 0 (no overflows).
103 __ jmp(slow_path_continuation());
104 }
105
106 { // Handle monitor medium path.
107
108 __ bind(_check_successor);
109
110 Label fix_zf_and_unlocked;
111 const Register monitor = _mark;
112
113 #ifndef _LP64
114 __ jmpb(restore_held_monitor_count_and_slow_path);
115 #else // _LP64
116 const ByteSize monitor_tag = in_ByteSize(UseObjectMonitorTable ? 0 : checked_cast<int>(markWord::monitor_value));
117 const Address succ_address{monitor, ObjectMonitor::succ_offset() - monitor_tag};
118 const Address owner_address{monitor, ObjectMonitor::owner_offset() - monitor_tag};
119
120 // successor null check.
121 __ cmpptr(succ_address, NULL_WORD);
122 __ jccb(Assembler::equal, restore_held_monitor_count_and_slow_path);
123
124 // Release lock.
125 __ movptr(owner_address, NULL_WORD);
126
127 // Fence.
128 // Instead of MFENCE we use a dummy locked add of 0 to the top-of-stack.
129 __ lock(); __ addl(Address(rsp, 0), 0);
130
131 // Recheck successor.
132 __ cmpptr(succ_address, NULL_WORD);
133 // Observed a successor after the release -> fence we have handed off the monitor
134 __ jccb(Assembler::notEqual, fix_zf_and_unlocked);
135
136 // Try to relock, if it fails the monitor has been handed over
137 // TODO: Caveat, this may fail due to deflation, which does
138 // not handle the monitor handoff. Currently only works
139 // due to the responsible thread.
140 __ xorptr(rax, rax);
141 __ lock(); __ cmpxchgptr(_thread, owner_address);
142 __ jccb (Assembler::equal, restore_held_monitor_count_and_slow_path);
143 #endif
144
145 __ bind(fix_zf_and_unlocked);
146 __ xorl(rax, rax);
147 __ jmp(unlocked_continuation());
148 }
149 }
150
151 #undef __
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