--- a/src/hotspot/share/opto/compile.cpp	Thu Nov 01 11:42:59 2018 -0400
+++ b/src/hotspot/share/opto/compile.cpp	Wed Nov 07 20:21:35 2018 +0100
@@ -1468,6 +1468,8 @@
         tj = TypeInstPtr::MARK;
         ta = TypeAryPtr::RANGE; // generic ignored junk
         ptr = TypePtr::BotPTR;
+      } else if (BarrierSet::barrier_set()->barrier_set_c2()->flatten_gc_alias_type(tj)) {
+        ta = tj->isa_aryptr();
       } else {                  // Random constant offset into array body
         offset = Type::OffsetBot;   // Flatten constant access into array body
         tj = ta = TypeAryPtr::make(ptr,ta->ary(),ta->klass(),false,offset);
@@ -1532,6 +1534,8 @@
       if (!is_known_inst) { // Do it only for non-instance types
         tj = to = TypeInstPtr::make(TypePtr::BotPTR, env()->Object_klass(), false, NULL, offset);
       }
+    } else if (BarrierSet::barrier_set()->barrier_set_c2()->flatten_gc_alias_type(tj)) {
+      to = tj->is_instptr();
     } else if (offset < 0 || offset >= k->size_helper() * wordSize) {
       // Static fields are in the space above the normal instance
       // fields in the java.lang.Class instance.
@@ -1630,7 +1634,8 @@
           (offset == Type::OffsetBot && tj == TypePtr::BOTTOM) ||
           (offset == oopDesc::mark_offset_in_bytes() && tj->base() == Type::AryPtr) ||
           (offset == oopDesc::klass_offset_in_bytes() && tj->base() == Type::AryPtr) ||
-          (offset == arrayOopDesc::length_offset_in_bytes() && tj->base() == Type::AryPtr)  ,
+          (offset == arrayOopDesc::length_offset_in_bytes() && tj->base() == Type::AryPtr) ||
+          (BarrierSet::barrier_set()->barrier_set_c2()->verify_gc_alias_type(tj, offset)),
           "For oops, klasses, raw offset must be constant; for arrays the offset is never known" );
   assert( tj->ptr() != TypePtr::TopPTR &&
           tj->ptr() != TypePtr::AnyNull &&