Request for reviews (S): 6832293: JIT compiler got wrong result in type checking with -server

[Tom Rodriguez]

That doesn't seem quite right to me or maybe I just don't like the way  
it's phrased.  The rules for subtyping for arrays are different than  
instances, so walking up the classes would change the subtype test.   
It also creates in consistency between klass and xklass.  What about  
this:

diff --git a/src/share/vm/opto/subnode.cpp b/src/share/vm/opto/ 
subnode.cpp
--- a/src/share/vm/opto/subnode.cpp
+++ b/src/share/vm/opto/subnode.cpp
@@ -639,8 +639,11 @@ const Type *CmpPNode::sub( const Type *t
      int kps = (p0->isa_klassptr()?1:0) + (p1->isa_klassptr()?1:0);
      if (klass0 && klass1 &&
          kps != 1 &&             // both or neither are klass pointers
-        klass0->is_loaded() && !klass0->is_interface() && // do not  
trust interfaces
-        klass1->is_loaded() && !klass1->is_interface()) {
+        // do not trust interfaces
+        klass0->is_loaded() && !klass0->is_interface() &&
+        (!klass0->is_obj_array_klass() || !klass0- 
 >as_obj_array_klass()->base_element_klass()->is_interface()) &&
+        klass1->is_loaded() && !klass1->is_interface() &&
+        (!klass1->is_obj_array_klass() || !klass1- 
 >as_obj_array_klass()->base_element_klass()->is_interface())) {
        bool unrelated_classes = false;
        // See if neither subclasses the other, or if the class on top
        // is precise.  In either of these cases, the compare is known

tom

On May 8, 2009, at 1:12 PM, Vladimir Kozlov wrote:

> http://cr.openjdk.java.net/~kvn/6832293/webrev.00
>
> Fixed 6832293: JIT compiler got wrong result in type checking with - 
> server
>
> Problem:
> The code in CmpPNode::sub is broken for arrays of interface types.
>
> Solution:
> In CmpPNode::sub compare klasses of obj arrays elements..
>
> Reviewed by:
>
> Fix verified (y/n): y, modified (for jdk7) bug's test
>
> Other testing:
> JPRT
>