RFR(M): arraycopy/clone/copyOf intrinsics fixes for Lworld

[Roland Westrelin]

Hi Tobias,

> In graphKit.cpp:3954 and macro.cpp:1443 shouldn't you use can_be_value_type() (you are not handling
> the interface element type in macro.cpp)? Also, in macro.cpp you don't need to load elem_klass if
> it's statically known.

If the allocation is:

new I[];

for some interface I then we know we're not allocating a value type
array that needs special initialization.

If the allocation is through reflection for some Class c then the type
system will report Object as array element. In that case, the array
could be a value type array. But for

new Object[];

the element type is also Object but it doesn't need special
initialization. So my patch should actually test whether the element
type is exact or not.

New webrev:

http://cr.openjdk.java.net/~roland/valhalla/arraycopy-lworld/webrev.02/

Change from previous one is:

diff --git a/src/hotspot/share/opto/graphKit.cpp b/src/hotspot/share/opto/graphKit.cpp
--- a/src/hotspot/share/opto/graphKit.cpp
+++ b/src/hotspot/share/opto/graphKit.cpp
@@ -3951,7 +3951,7 @@
       // InitializeNode* init = alloc->initialization();
       //init->set_complete_with_arraycopy();
     }
-  } else if (EnableValhalla && (!layout_con || (elem_klass != NULL && elem_klass->is_java_lang_Object()))) {
+  } else if (EnableValhalla && (!layout_con || (elem_klass != NULL && elem_klass->is_java_lang_Object() && !ary_type->klass_is_exact()))) {
     InitializeNode* init = alloc->initialization();
     init->set_unknown_value();
   }
diff --git a/src/hotspot/share/opto/macro.cpp b/src/hotspot/share/opto/macro.cpp
--- a/src/hotspot/share/opto/macro.cpp
+++ b/src/hotspot/share/opto/macro.cpp
@@ -1440,7 +1440,7 @@
       elem_klass = ary_ptr->klass()->as_array_klass()->element_klass();
     }
 
-    if (elem_klass == NULL || elem_klass->is_java_lang_Object() || elem_klass->is_valuetype()) {
+    if (elem_klass == NULL || (elem_klass->is_java_lang_Object() && !ary_ptr->klass_is_exact()) || elem_klass->is_valuetype()) {
       // If it's an array of values we must go to the slow path so it is
       // correctly initialized with default values.
       Node* fast_region = new RegionNode(3);


Wrt, to the load of elem_klass that's not needed. That will be optimize
away, right? I would rather keep the logic simple.

Roland.