8277180: Intrinsify recursive ObjectMonitor locking for C2 x64 and A64

Reviewed-by: aph, ngasson

Author: fisk

src/hotspot/cpu/aarch64/aarch64.ad

@@ -3945,7 +3945,7 @@ encode %{
     // Try to CAS m->owner from NULL to current thread.
     __ add(tmp, disp_hdr, (ObjectMonitor::owner_offset_in_bytes()-markWord::monitor_value));
     __ cmpxchg(tmp, zr, rthread, Assembler::xword, /*acquire*/ true,
-               /*release*/ true, /*weak*/ false, noreg); // Sets flags for result
+               /*release*/ true, /*weak*/ false, rscratch1); // Sets flags for result
 
     // Store a non-null value into the box to avoid looking like a re-entrant
     // lock. The fast-path monitor unlock code checks for
@@ -3954,6 +3954,15 @@ encode %{
     __ mov(tmp, (address)markWord::unused_mark().value());
     __ str(tmp, Address(box, BasicLock::displaced_header_offset_in_bytes()));
 
+    __ br(Assembler::EQ, cont); // CAS success means locking succeeded
+
+    __ cmp(rscratch1, rthread);
+    __ br(Assembler::NE, cont); // Check for recursive locking
+
+    // Recursive lock case
+    __ increment(Address(disp_hdr, ObjectMonitor::recursions_offset_in_bytes() - markWord::monitor_value), 1);
+    // flag == EQ still from the cmp above, checking if this is a reentrant lock
+
     __ bind(cont);
     // flag == EQ indicates success
     // flag == NE indicates failure
@@ -3997,11 +4006,20 @@ encode %{
     __ add(tmp, tmp, -(int)markWord::monitor_value); // monitor
     __ ldr(rscratch1, Address(tmp, ObjectMonitor::owner_offset_in_bytes()));
     __ ldr(disp_hdr, Address(tmp, ObjectMonitor::recursions_offset_in_bytes()));
-    __ eor(rscratch1, rscratch1, rthread); // Will be 0 if we are the owner.
-    __ orr(rscratch1, rscratch1, disp_hdr); // Will be 0 if there are 0 recursions
-    __ cmp(rscratch1, zr); // Sets flags for result
+
+    Label notRecursive;
+    __ cmp(rscratch1, rthread);
     __ br(Assembler::NE, cont);
 
+    __ cbz(disp_hdr, notRecursive);
+
+    // Recursive lock
+    __ sub(disp_hdr, disp_hdr, 1u);
+    __ str(disp_hdr, Address(tmp, ObjectMonitor::recursions_offset_in_bytes()));
+    // flag == EQ was set in the ownership check above
+    __ b(cont);
+
+    __ bind(notRecursive);
     __ ldr(rscratch1, Address(tmp, ObjectMonitor::EntryList_offset_in_bytes()));
     __ ldr(disp_hdr, Address(tmp, ObjectMonitor::cxq_offset_in_bytes()));
     __ orr(rscratch1, rscratch1, disp_hdr); // Will be 0 if both are 0.

src/hotspot/cpu/x86/c2_MacroAssembler_x86.cpp

@@ -574,8 +574,13 @@ void C2_MacroAssembler::fast_lock(Register objReg, Register boxReg, Register tmp
   // Unconditionally set box->_displaced_header = markWord::unused_mark().
   // Without cast to int32_t this style of movptr will destroy r10 which is typically obj.
   movptr(Address(boxReg, 0), (int32_t)intptr_t(markWord::unused_mark().value()));
-  // Intentional fall-through into DONE_LABEL ...
   // Propagate ICC.ZF from CAS above into DONE_LABEL.
+  jcc(Assembler::equal, DONE_LABEL);           // CAS above succeeded; propagate ZF = 1 (success)
+
+  cmpptr(r15_thread, rax);                     // Check if we are already the owner (recursive lock)
+  jcc(Assembler::notEqual, DONE_LABEL);        // If not recursive, ZF = 0 at this point (fail)
+  incq(Address(scrReg, OM_OFFSET_NO_MONITOR_VALUE_TAG(recursions)));
+  xorq(rax, rax); // Set ZF = 1 (success) for recursive lock, denoting locking success
 #endif // _LP64
 #if INCLUDE_RTM_OPT
   } // use_rtm()
@@ -670,10 +675,6 @@ void C2_MacroAssembler::fast_unlock(Register objReg, Register boxReg, Register t
   // Refer to the comments in synchronizer.cpp for how we might encode extra
   // state in _succ so we can avoid fetching EntryList|cxq.
   //
-  // I'd like to add more cases in fast_lock() and fast_unlock() --
-  // such as recursive enter and exit -- but we have to be wary of
-  // I$ bloat, T$ effects and BP$ effects.
-  //
   // If there's no contention try a 1-0 exit.  That is, exit without
   // a costly MEMBAR or CAS.  See synchronizer.cpp for details on how
   // we detect and recover from the race that the 1-0 exit admits.
@@ -721,9 +722,16 @@ void C2_MacroAssembler::fast_unlock(Register objReg, Register boxReg, Register t
   bind (CheckSucc);
 #else // _LP64
   // It's inflated
-  xorptr(boxReg, boxReg);
-  orptr(boxReg, Address(tmpReg, OM_OFFSET_NO_MONITOR_VALUE_TAG(recursions)));
-  jccb  (Assembler::notZero, DONE_LABEL);
+  Label LNotRecursive, LSuccess, LGoSlowPath;
+
+  cmpptr(Address(tmpReg, OM_OFFSET_NO_MONITOR_VALUE_TAG(recursions)), 0);
+  jccb(Assembler::equal, LNotRecursive);
+
+  // Recursive inflated unlock
+  decq(Address(tmpReg, OM_OFFSET_NO_MONITOR_VALUE_TAG(recursions)));
+  jmpb(LSuccess);
+
+  bind(LNotRecursive);
   movptr(boxReg, Address(tmpReg, OM_OFFSET_NO_MONITOR_VALUE_TAG(cxq)));
   orptr(boxReg, Address(tmpReg, OM_OFFSET_NO_MONITOR_VALUE_TAG(EntryList)));
   jccb  (Assembler::notZero, CheckSucc);
@@ -732,7 +740,6 @@ void C2_MacroAssembler::fast_unlock(Register objReg, Register boxReg, Register t
   jmpb  (DONE_LABEL);
 
   // Try to avoid passing control into the slow_path ...
-  Label LSuccess, LGoSlowPath ;
   bind  (CheckSucc);
 
   // The following optional optimization can be elided if necessary