8266368: Inaccurate after_unwind hook in C2 exception handler

Reviewed-by: dlong, thartmann

src/hotspot/share/opto/runtime.cpp

@@ -1280,6 +1280,11 @@ static void trace_exception(outputStream* st, oop exception_oop, address excepti
 // directly from compiled code. Compiled code will call the C++ method following.
 // We can't allow async exception to be installed during  exception processing.
 JRT_ENTRY_NO_ASYNC(address, OptoRuntime::handle_exception_C_helper(JavaThread* current, nmethod* &nm))
+  // The frame we rethrow the exception to might not have been processed by the GC yet.
+  // The stack watermark barrier takes care of detecting that and ensuring the frame
+  // has updated oops.
+  StackWatermarkSet::after_unwind(current);
+
   // Do not confuse exception_oop with pending_exception. The exception_oop
   // is only used to pass arguments into the method. Not for general
   // exception handling.  DO NOT CHANGE IT to use pending_exception, since
@@ -1422,7 +1427,7 @@ address OptoRuntime::handle_exception_C(JavaThread* current) {
   // deoptimized frame
 
   if (nm != NULL) {
-    RegisterMap map(current, false);
+    RegisterMap map(current, false /* update_map */, false /* process_frames */);
     frame caller = current->last_frame().sender(&map);
 #ifdef ASSERT
     assert(caller.is_compiled_frame(), "must be");
@@ -1461,11 +1466,6 @@ address OptoRuntime::rethrow_C(oopDesc* exception, JavaThread* thread, address r
   // Enable WXWrite: the function called directly by compiled code.
   MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXWrite, thread));
 
-  // The frame we rethrow the exception to might not have been processed by the GC yet.
-  // The stack watermark barrier takes care of detecting that and ensuring the frame
-  // has updated oops.
-  StackWatermarkSet::after_unwind(thread);
-
 #ifndef PRODUCT
   SharedRuntime::_rethrow_ctr++;               // count rethrows
 #endif

src/hotspot/share/runtime/sharedRuntime.cpp

@@ -497,7 +497,7 @@ address SharedRuntime::raw_exception_handler_for_return_address(JavaThread* curr
       return SharedRuntime::deopt_blob()->unpack_with_exception();
     } else {
       // The deferred StackWatermarkSet::after_unwind check will be performed in
-      // * OptoRuntime::rethrow_C for C2 code
+      // * OptoRuntime::handle_exception_C_helper for C2 code
       // * exception_handler_for_pc_helper via Runtime1::handle_exception_from_callee_id for C1 code
       return nm->exception_begin();
     }