8338383: Implement JEP 491: Synchronize Virtual Threads without Pinning

Co-authored-by: Patricio Chilano Mateo <pchilanomate@openjdk.org>
Co-authored-by: Alan Bateman <alanb@openjdk.org>
Co-authored-by: Andrew Haley <aph@openjdk.org>
Co-authored-by: Fei Yang <fyang@openjdk.org>
Co-authored-by: Coleen Phillimore <coleenp@openjdk.org>
Co-authored-by: Richard Reingruber <rrich@openjdk.org>
Co-authored-by: Martin Doerr <mdoerr@openjdk.org>
Reviewed-by: aboldtch, dholmes, coleenp, fbredberg, dlong, sspitsyn

Author: 7 people

src/hotspot/cpu/aarch64/aarch64.ad

@@ -1648,8 +1648,8 @@ int MachCallRuntimeNode::ret_addr_offset() {
   // for real runtime callouts it will be six instructions
   // see aarch64_enc_java_to_runtime
   //   adr(rscratch2, retaddr)
+  //   str(rscratch2, Address(rthread, JavaThread::last_Java_pc_offset()));
   //   lea(rscratch1, RuntimeAddress(addr)
-  //   stp(zr, rscratch2, Address(__ pre(sp, -2 * wordSize)))
   //   blr(rscratch1)
   CodeBlob *cb = CodeCache::find_blob(_entry_point);
   if (cb) {
@@ -3696,14 +3696,13 @@ encode %{
       __ post_call_nop();
     } else {
       Label retaddr;
+      // Make the anchor frame walkable
       __ adr(rscratch2, retaddr);
+      __ str(rscratch2, Address(rthread, JavaThread::last_Java_pc_offset()));
       __ lea(rscratch1, RuntimeAddress(entry));
-      // Leave a breadcrumb for JavaFrameAnchor::capture_last_Java_pc()
-      __ stp(zr, rscratch2, Address(__ pre(sp, -2 * wordSize)));
       __ blr(rscratch1);
       __ bind(retaddr);
       __ post_call_nop();
-      __ add(sp, sp, 2 * wordSize);
     }
     if (Compile::current()->max_vector_size() > 0) {
       __ reinitialize_ptrue();

src/hotspot/cpu/aarch64/c1_MacroAssembler_aarch64.cpp

@@ -119,8 +119,8 @@ int C1_MacroAssembler::lock_object(Register hdr, Register obj, Register disp_hdr
     cbnz(hdr, slow_case);
     // done
     bind(done);
+    inc_held_monitor_count(rscratch1);
   }
-  increment(Address(rthread, JavaThread::held_monitor_count_offset()));
   return null_check_offset;
 }
 
@@ -159,8 +159,8 @@ void C1_MacroAssembler::unlock_object(Register hdr, Register obj, Register disp_
     }
     // done
     bind(done);
+    dec_held_monitor_count(rscratch1);
   }
-  decrement(Address(rthread, JavaThread::held_monitor_count_offset()));
 }