src/hotspot/share/opto/memnode.cpp

*** 1846,1860 ****
              // unsafe field access may not have a constant offset
              C->has_unsafe_access(),
              "Field accesses must be precise" );
      // For oop loads, we expect the _type to be precise.
  
-     // Optimize loads from constant fields.
      const TypeInstPtr* tinst = tp->is_instptr();
      ciObject* const_oop = tinst->const_oop();
      if (!is_mismatched_access() && off != Type::OffsetBot && const_oop != NULL && const_oop->is_instance()) {
-       BasicType bt = memory_type();
        ciType* mirror_type = const_oop->as_instance()->java_mirror_type();
        if (mirror_type != NULL && mirror_type->is_valuetype()) {
          ciValueKlass* vk = mirror_type->as_value_klass();
          if (off == vk->default_value_offset()) {
            // Loading a special hidden field that contains the oop of the default value type
--- 1846,1877 ----
              // unsafe field access may not have a constant offset
              C->has_unsafe_access(),
              "Field accesses must be precise" );
      // For oop loads, we expect the _type to be precise.
  
      const TypeInstPtr* tinst = tp->is_instptr();
+     BasicType bt = memory_type();
+ 
+     // Fold component and value mirror loads
+     ciInstanceKlass* ik = tinst->klass()->as_instance_klass();
+     if (ik == phase->C->env()->Class_klass() && (off == java_lang_Class::component_mirror_offset_in_bytes() ||
+                                                  off == java_lang_Class::value_mirror_offset_in_bytes())) {
+       ciType* mirror_type = tinst->java_mirror_type();
+       if (mirror_type != NULL) {
+         const Type* const_oop = TypePtr::NULL_PTR;
+         if (mirror_type->is_array_klass()) {
+           const_oop = TypeInstPtr::make(mirror_type->as_array_klass()->component_mirror_instance());
+         } else if (mirror_type->is_valuetype()) {
+           const_oop = TypeInstPtr::make(mirror_type->as_value_klass()->value_mirror_instance());
+         }
+         return (bt == T_NARROWOOP) ? const_oop->make_narrowoop() : const_oop;
+       }
+     }
+ 
+     // Optimize loads from constant fields.
      ciObject* const_oop = tinst->const_oop();
      if (!is_mismatched_access() && off != Type::OffsetBot && const_oop != NULL && const_oop->is_instance()) {
        ciType* mirror_type = const_oop->as_instance()->java_mirror_type();
        if (mirror_type != NULL && mirror_type->is_valuetype()) {
          ciValueKlass* vk = mirror_type->as_value_klass();
          if (off == vk->default_value_offset()) {
            // Loading a special hidden field that contains the oop of the default value type
*** 2240,2258 ****
      ciKlass *tary_klass = tary->klass();
      if (tary_klass != NULL   // can be NULL when at BOTTOM or TOP
          && tary->offset() == oopDesc::klass_offset_in_bytes()) {
        ciArrayKlass* ak = tary_klass->as_array_klass();
        // Do not fold klass loads from [V? because the runtime type might be [V due to [V <: [V?
!       bool can_be_flattened = ak->is_obj_array_klass() && !ak->storage_properties().is_null_free() && ak->element_klass()->is_valuetype();
  
!       if (tary->klass_is_exact() && !can_be_flattened) {
          return TypeKlassPtr::make(tary_klass);
        }
  
        // If the klass is an object array, we defer the question to the
        // array component klass.
!       if (ak->is_obj_array_klass() && !can_be_flattened) {
          assert(ak->is_loaded(), "");
          ciKlass *base_k = ak->as_obj_array_klass()->base_element_klass();
          if (base_k->is_loaded() && base_k->is_instance_klass()) {
            ciInstanceKlass *ik = base_k->as_instance_klass();
            // See if we can become precise: no subklasses and no interface
--- 2257,2275 ----
      ciKlass *tary_klass = tary->klass();
      if (tary_klass != NULL   // can be NULL when at BOTTOM or TOP
          && tary->offset() == oopDesc::klass_offset_in_bytes()) {
        ciArrayKlass* ak = tary_klass->as_array_klass();
        // Do not fold klass loads from [V? because the runtime type might be [V due to [V <: [V?
!       bool can_be_null_free = !tary->is_known_instance() && ak->is_obj_array_klass() && !ak->storage_properties().is_null_free() && ak->element_klass()->is_valuetype();
  
!       if (tary->klass_is_exact() && !can_be_null_free) {
          return TypeKlassPtr::make(tary_klass);
        }
  
        // If the klass is an object array, we defer the question to the
        // array component klass.
!       if (ak->is_obj_array_klass() && !can_be_null_free) {
          assert(ak->is_loaded(), "");
          ciKlass *base_k = ak->as_obj_array_klass()->base_element_klass();
          if (base_k->is_loaded() && base_k->is_instance_klass()) {
            ciInstanceKlass *ik = base_k->as_instance_klass();
            // See if we can become precise: no subklasses and no interface