8258553: Limit number of fields in instance to be considered for scalar replacement

Reviewed-by: kvn, vlivanov

Author: Igor Veresov

src/hotspot/share/opto/c2_globals.hpp

@@ -536,6 +536,10 @@
           "Array size (number of elements) limit for scalar replacement")   \
           range(0, max_jint)                                                \
                                                                             \
+  product(intx, EliminateAllocationFieldsLimit, 512, DIAGNOSTIC,            \
+          "Number of fields in instance limit for scalar replacement")      \
+          range(0, max_jint)                                                \
+                                                                            \
   product(bool, OptimizePtrCompare, true,                                   \
           "Use escape analysis to optimize pointers compare")               \
                                                                             \

src/hotspot/share/opto/escape.cpp

@@ -906,6 +906,12 @@ void ConnectionGraph::add_call_node(CallNode* call) {
          !cik->as_instance_klass()->can_be_instantiated() ||
           cik->as_instance_klass()->has_finalizer()) {
         es = PointsToNode::GlobalEscape;
+      } else {
+        int nfields = cik->as_instance_klass()->nof_nonstatic_fields();
+        if (nfields > EliminateAllocationFieldsLimit) {
+          // Not scalar replaceable if there are too many fields.
+          scalar_replaceable = false;
+        }
       }
     }
     add_java_object(call, es);